LOW-CARBON, LOW-ALLOY AND HIGH-FORMABILITY DUAL-PHASE STEEL HAVING TENSILE STRENGTH OF GREATER THAN OR EQUAL TO 590 MPA, HOT-DIP GALVANIZED DUAL-PHASE STEEL, AND MANUFACTURING METHOD THEREFOR

Abstract

A low-carbon, low-alloy and high-formability dual-phase steel having a tensile strength of greater than or equal to 590 MPa, a hot-dip galvanized dual-phase steel, and a manufacturing method therefor by means of rapid heat treatment. The steel comprises the following components, in percentage by mass: 0.04-0.12% of C, 0.1-0.5% of Si, 1.0-2.0% of Mn, P0.02%, S0.015%, 0.02-0.06% of Al, and can further comprise one or two of Cr, Mo, Ti, Nb and V, wherein Cr+Mo+Ti+Nb+V0.5%, and the balance is Fe and other unavoidable impurities. The manufacturing method therefor includes smelting, casting, hot rolling, cold rolling, and rapid heat treatment processes. In the present invention, by controlling rapid heating, short-term thermal insulation and rapid cooling processes during the process of rapid heat treatment, the recovery of a deformed structure, recrystallization and austenite transformation processes are changed, the nucleation rate is increased, the grain growth time is shortened, grains are refined, the strength and n value of the material are improved, and the interval range of the material performance is expanded.

Claims

1. A low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa, which comprises the following chemical components in mass percentages: C: 0.040.12%, Si: 0.10.5%, Mn: 1.02.0%, P0.02%, S0.015%, Al: 0.020.06%, optionally one or two of Cr, Mo, Ti, Nb, V, and Cr+Mo+Ti+Nb+V0.5%, with a balance of Fe and other unavoidable impurities.

2. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 1, wherein the dual-phase steel or hot-galvanized dual-phase steel has a yield strength of 340560 MPa, a tensile strength of 620880 MPa, an elongation of 1930.5%, a product of strength and elongation of 15.520.5 GPa % and a strain hardening index n.sub.90 value greater than 0.20; and/or wherein the microstructure of the dual-phase steel or hot-galvanized dual-phase steel is a dual-phase structure of ferrite and martensite having an average grain size of 210 m.

3. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 1, wherein the low carbon low alloy dual-phase steel with high formability having a tensile strength of 590 MPa is obtained by the following process: 1) Smelting, casting wherein the above components are subjected to smelting and casting to form a slab; 2) hot rolling, coiling wherein a hot rolling finishing temperature is A.sub.r3; and a coiling temperature is 550680 C.; 3) cold rolling wherein a cold rolling reduction rate is 4085%; 4) Rapid heat treatment wherein the steel plate after cold rolling is rapidly heated to 750845 C., wherein the rapid heating is performed in one stage or two stages; when the rapid heating is performed in one stage, a heating rate is 50500 C./s; when the rapid heating is performed in two stages, the steel plate is heated in the first stage from room temperature to 550650 C. at a heating rate of 15500 C./s, heated in the second stage from 550650 C. to 750845 C. at a heating rate of 30500 C./s (such as 50500 C./s); then soaked at a soaking temperature of 750845 C. for a soaking time of 1060 s; wherein after soaking, the steel plate is slowly cooled to 670770 C. at a cooling rate of 515 C./s, then rapidly cooled from 670770 C. to room temperature at a cooling rate of 50200 C./s; or the steel plate is rapidly cooled from 670770 C. to 230280 C. at a cooling rate of 50200 C./s, and over-aged in this temperature range, wherein an over-ageing treating time is less than or equal to 200 s; and finally cooled to room temperature at a cooling rate of 3050 C./s.

4. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 3, wherein the process has one or more of the following features: in step 4), a total time of the rapid heat treatment is 41300 s or 41296 s; in step 2), the coiling temperature is 580650 C.; in step 3), the cold rolling reduction rate is 6080%; in step 4), when the rapid heating is performed in one stage, the heating rate is 50300 C./s; in step 4), the rapid heating is performed in two stages, wherein the steel plate is heated in the first stage from room temperature to 550650 C. at a heating rate of 15300 C./s, heated in the second stage from 550650 C. to 750845 C. at a heating rate of 50300 C./s; or the steel plate is heated in the first stage from room temperature to 550650 C. at a heating rate of 50300 C./s, heated in the second stage from 550650 C. to 750845 C. at a heating rate of 80300 C./s; in step 4), the soaking time is 1040 s; in step 4), the rapid cooling rate of the steel plate is 50150 C./s; and the over ageing time is 20200 s.

5. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 1, wherein: (1) the low carbon low alloy dual-phase steel with high formability comprises the following chemical components in mass percentages: C: 0.040.10%, Si: 0.10.3%, Mn: 1.01.6%, P0.02%, S0.015%, Al: 0.020.06%, optionally one or two of Cr, Mo, Ti, Nb, V, and Cr+Mo+Ti+Nb+V0.5%, with a balance of Fe and other unavoidable impurities; or (2) the low carbon low alloy dual-phase steel with high formability comprises the following chemical components in mass percentages: C: 0.050.12%, Si: 0.010.5%, Mn: 1.22.0%, P0.015%, S0.003%, Al: 0.020.055%, optionally one or two of Cr, Mo, Ti, Nb, V, and Cr+Mo+Ti+Nb+V0.5%, with a balance of Fe and other unavoidable impurities; or (3) the low carbon low alloy dual-phase steel with high formability comprises the following chemical components in mass percentages: C: 0.0450.12%, Si: 0.10.5%, Mn: 1.02.0%, P0.02%, S0.006%, Al: 0.020.055%, optionally one or two of Cr, Mo, Ti, Nb, V, and Cr+Mo+Ti+Nb+V0.5%, with a balance of Fe and other unavoidable impurities.

6.-7. (canceled)

8. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 5, wherein after the end of soaking step and the steel is slowly cooled to 670770 C., it is rapidly cooled to 460470 C. at a cooling rate of 50200 C./s and immersed in a zinc pot for hot galvanizing to obtain the hot-galvanized dual phase steel; optionally, after hot galvanizing, the steel is rapidly cooled to room temperature at a cooling rate of 30150 C./s to obtain a hot dip galvanized GI product or after hot galvanizing, the steel is heated to 480550 C. at a heating rate of 30200 C./s and alloyed for 1020 s; optionally, after alloying, the steel is rapidly cooled to room temperature at a cooling rate of 30250 C./s to obtain an alloy galvannealed GA product.

9. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 1, wherein the hot-galvanized dual-phase steel comprises the following chemical components in mass percentages: C: 0.0450.105%, Si: 0.10.4%, Mn: 1.01.5%, P0.02%, S0.006%, Al: 0.020.055%, optionally one or two of Cr, Mo, Ti, Nb, V, and Cr+Mo+Ti+Nb+V0.3%, with a balance of Fe and other unavoidable impurities.

10. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 1, wherein the hot-galvanized dual-phase steel comprises the following chemical components in mass percentages: C: 0.050.12%, Si: 0.010.5%, Mn: 1.22.0%, P0.015%, S0.003%, Al: 0.020.055%, optionally one or two of Cr, Mo, Ti, Nb, V, and Cr+Mo+Ti+Nb+V0.5%, with a balance of Fe and other unavoidable impurities.

11. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 9, wherein the hot-galvanized dual-phase steel with high formability is obtained by the following process: a) Smelting, casting wherein the above components are subjected to smelting and casting to form a slab; b) Hot rolling, coiling wherein a hot rolling finishing temperature is A.sub.r3; and a coiling temperature is 550680 C.; c) Cold rolling wherein a cold rolling reduction rate is 4085%; d) Rapid heat treatment, hot-galvanizing wherein the steel plate after cold rolling is rapidly heated to 750845 C., wherein the rapid heating is performed in one stage or two stages; when the rapid heating is performed in one stage, a heating rate is 50500 C./s; when the rapid heating is performed in two stages, the steel plate is heated in the first stage from room temperature to 550650 C. at a heating rate of 15500 C./s, heated in the second stage from 550650 C. to 750845 C. at a heating rate of 30500 C./s (such as 50500 C./s); then soaked at a soaking temperature of 750845 C. for a soaking time of 1060 s; wherein after soaking, the steel plate is slowly cooled to 670770 C. at a cooling rate of 515 C./s, then rapidly cooled to 460470 C. at a cooling rate of 50200 C./s, such as 50150 C./s, and immersed in a zinc pot for hot galvanizing; wherein after hot galvanizing, the steel plate is rapidly cooled to room temperature at a cooling rate of 30150 C./s to obtain a hot dip galvanized GI product; or after hot galvanizing, the steel plate is heated to 480550 C. at a heating rate of 30200 C./s and alloyed for 1020 s; after alloying, the steel plate is rapidly cooled to room temperature at a cooling rate of 30250 C./s to obtain an alloy galvannealed GA product.

12. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 11, wherein the process has one or more of the following features: a total time of the rapid heat treatment and hot-galvanizing of step d) is 30142 s; in step b), the coiling temperature is 580650 C.; in step c), the cold rolling reduction rate is 6080%; in step d), when the rapid heating is performed in one stage, the heating rate is 50300 C./s; in step d), the rapid heating is performed in two stages, wherein the steel plate is heated in the first stage from room temperature to 550650 C. at a heating rate of 15300 C./s, heated in the second stage from 550650 C. to 750845 C. at a heating rate of 50300 C./s; or the steel plate is heated in the first stage from room temperature to 550650 C. at a heating rate of 30300 C./s, heated in the second stage from 550650 C. to 750845 C. at a heating rate of 80300 C./s

13. A manufacturing process of low carbon low alloy dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 1, which comprises the following steps: 1) Smelting, casting wherein the above components are subjected to smelting and casting to form a slab; 2) hot rolling, coiling wherein a hot rolling finishing temperature is A.sub.r3; and a coiling temperature is 550680 C.; 3) cold rolling wherein a cold rolling reduction rate is 4085%, thereby obtaining a rolled hard strip steel or steel plate; 4) Rapid heat treatment a) Rapid heating wherein the strip steel or steel plate after cold rolling is rapidly heated to 750845 C., wherein the rapid heating is performed in one stage or two stages; when the rapid heating is performed in one stage, a heating rate is 50500 C./s; when the rapid heating is performed in two stages, the steel plate is heated in the first stage from room temperature to 550650 C. at a heating rate of 15500 C./s, heated in the second stage from 550650 C. to 750845 C. at a heating rate of 30500 C./s (such as 50500 C./s); b) Soaking wherein the strip steel or steel plate is soaked at a temperature of 750845 C., which is the target temperature of the dual phase region of austenite and ferrite, for a soaking time of 1060 s; c) Cooling wherein after soaking, the strip steel or steel plate is slowly cooled to 670770 C. at a cooling rate of 515 C./s, then rapidly cooled from 670770 C. to room temperature at a cooling rate of 50200 C./s; or the strip steel or steel plate is rapidly cooled from 670770 C. to 230280 C. at a cooling rate of 50200 C./s for over-ageing treatment, wherein an over-ageing treating time is less than or equal to 200 s; after over-ageing treatment, it is finally cooled to room temperature at a cooling rate of 3050 C./s.

14. The manufacturing process by rapid heat treatment of the low carbon low alloy hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 1, which comprises the following steps: A) Smelting, casting wherein the above components are subjected to smelting and casting to form a slab; B) Hot rolling, coiling wherein a hot rolling finishing temperature is A.sub.r3; and a coiling temperature is 550680 C.; C) Cold rolling wherein a cold rolling reduction rate is 4085%, thereby obtaining a rolled hard strip steel or steel plate; D) Rapid heat treatment, hot-galvanizing a) rapid heating wherein the strip steel or steel plate after cold rolling is rapidly heated from room temperature to 750845 C., which is the target temperature of dual phase region of austenite and ferrite, wherein the rapid heating is performed in one stage or two stages; when the rapid heating is performed in one stage, a heating rate is 50500 C./s; when the rapid heating is performed in two stages, the strip steel or steel plate is heated in the first stage from room temperature to 550650 C. at a heating rate of 15500 C./s, heated in the second stage from 550650 C. to 750845 C. at a heating rate of 30500 C./s (such as 50500 C./s); b) Soaking wherein the strip steel or steel plate is soaked at a temperature of 750845 C., which is the target temperature of the dual phase region of austenite and ferrite, for a soaking time of 1060 s; c) Cooling, hot-galvanizing wherein after soaking, the strip steel or steel plate is slowly cooled to 670770 C. at a cooling rate of 515 C./s, then rapidly cooled to 460470 C. at a cooling rate of 50150 C./s and immersed in a zinc pot for hot galvanizing; d) after hot galvanizing, the strip steel or steel plate is rapidly cooled to room temperature at a cooling rate of 50150 C./s to obtain a hot dip galvanized GI product; or after hot galvanizing, the strip steel or steel plate is heated to 480550 C. at a heating rate of 30200 C./s and alloyed for 1020 s; after alloying, the strip steel or steel plate is rapidly cooled to room temperature at a cooling rate of 30250 C./s to obtain an alloy galvannealed GA product.

15. The process according to claim 13 comprises one or more of the following features: a total time of the rapid heat treatment of step 4) is 41300 s or 41296 s; in step 2), the coiling temperature is 580650 C.; in step 3), the cold rolling reduction rate is 6080%; in step 4), when the rapid heating is performed in one stage, the heating rate is 50300 C./s; in step 4), the rapid heating is performed in two stages, wherein the strip steel or steel plate is heated in the first stage from room temperature to 550650 C. at a heating rate of 15300 C./s, heated in the second stage from 550650 C. to 750845 C. at a heating rate of 50300 C./s, or the strip steel or steel plate is heated in the first stage from room temperature to 550650 C. at a heating rate of 50300 C./s, heated in the second stage from 550650 C. to 750845 C. at a heating rate of 80300 C./s; in step 4), the final temperature after rapid heating is 770830 C. or 790830 C.; in step 4), the rapid cooling rate of the strip steel or steel plate is 50150 C./s; in the soaking process of step 4) after the strip steel or steel plate is heated to the target temperature of dual phase region of austenite and ferrite, the temperature is kept unchanged for soaking; in the soaking process of step 4), the strip steel or steel plate is slightly heated up or cooled down in the soaking time, wherein the temperature after heating is no more than 845 C. and the temperature after cooling is no less than 750 C.; the soaking time is 1040 s; the over ageing time is 20200 s.

16. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 1, wherein in the dual-phase steel with high formability or the hot-galvanized dual-phase steel with high formability: the content of C is 0.0450.105%, 0.040.10%, 0.051.2%, 0.060.08%, 0.0650.085% or 0.070.1%; and/or the content of Si is 0.10.4%, 0.10.3% or 0.150.25%; and/or the content of Mn is 1.01.6%, 1.01.5%, 1.22.0%, 1.21.4%, 1.21.35% or 1.51.8%; and/or Cr+Mo+Ti+Nb+V0.3%; and/or the low carbon low alloy dual-phase steel with high formability having a tensile strength of 590 MPa comprises the following chemical components in mass percentages: C: 0.040.105%, Si: 0.10.4%, Mn: 1.01.6%, P0.02%, S0.015%, Al: 0.020.06%, optionally one or two of Cr, Mo, Ti, Nb, V, and Cr+Mo+Ti+Nb+V0.5%, with a balance of Fe and other unavoidable impurities.

17. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 5, wherein in (1): the dual-phase steel has a C content of 0.060.08%; and/or the dual-phase steel has a Si content of 0.150.25%; and/or the dual-phase steel has a Mn content of 1.2%1.4%; and/or the microstructure of the dual-phase steel is a dual-phase structure of ferrite and martensite having an average grain size of 410 m; and/or the dual-phase steel has a yield strength of 350410 MPa, a tensile strength of 620710 MPa, an elongation of 24.030.5%, a product of strength and elongation of 1720.5 GPa % and a strain hardening index n.sub.90 value greater than 0.20; or the dual-phase steel has a yield strength of 350405 MPa, a tensile strength of 624706 MPa, an elongation of 24.430.4%, a product of strength and elongation of 1720.1 GPa % and a strain hardening index n.sub.90 value greater than 0.20; and/or in the manufacturing process of the dual-phase steel, a total time of the rapid heat treatment in step 4) is 41300 s.

18. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 5, wherein in (2): the dual-phase steel has a tensile strength of 780 MPa; and/or the dual-phase steel has a C content of 0.070.1%; and/or the dual-phase steel has a Si content of 0.10.4%; and/or the dual-phase steel has a Mn content of 1.5%1.8%; and/or the microstructure of the dual-phase steel is a dual-phase structure of ferrite and martensite having an average grain size of 28 m; and/or the dual-phase steel has a yield strength of 400540 MPa, a tensile strength of 780880 MPa, an elongation of 1924.5%, a product of strength and elongation of 1924.5 GPa % and a strain hardening index n.sub.90 value greater than 0.20; or the dual-phase steel has a yield strength of 400533 MPa, a tensile strength of 781878 MPa, an elongation of 19.524.1%, a product of strength and elongation of 16.319.3 GPa % and a strain hardening index n.sub.90 value greater than 0.20; and/or in the manufacturing process of the dual-phase steel, a total time of the rapid heat treatment in step 4) is 41296 s.

19. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 9, wherein: in the hot-galvanized dual-phase steel, the C content is 0.0650.085%; and/or in the hot-galvanized dual-phase steel, the Si content is 0.150.25%; and/or in the hot-galvanized dual-phase steel, the Mn content is 1.2%1.35%; and/or in the hot-galvanized dual-phase steel, Cr+Mo+Ti+Nb+V0.2%; and/or the dual-phase steel has a yield strength of 340410 MPa, a tensile strength of 620710 MPa, an elongation of 2230.5%, a product of strength and elongation of 15.520.0 GPa % and a strain hardening index n.sub.90 value greater than 0.21; or the hot-galvanized dual-phase steel has a yield strength of 347405 MPa, a tensile strength of 624709 MPa, an elongation of 22.230.3%, a product of strength and elongation of 15.719.6 GPa % and a strain hardening index n.sub.90 value greater than 0.21.

20. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 10, wherein: the hot-galvanized dual-phase steel has a yield strength of 780 MPa; and/or the hot-galvanized dual-phase steel has a C content of 0.070.1%; and/or the hot-galvanized dual-phase steel has a Si content of 0.10.4%; and/or the hot-galvanized dual-phase steel has a Mn content of 1.5%1.8%; and/or the hot-galvanized dual-phase steel has a yield strength of 400560 MPa, a tensile strength of 790870 MPa, an elongation of 19.025.0%, a product of strength and elongation of 16.020.0 GPa % and a strain hardening index n90 value greater than 0.20; or the hot-galvanized dual-phase steel has a yield strength of 400552 MPa, a tensile strength of 798862 MPa, an elongation of 19.524.6%, a product of strength and elongation of 16.319.9 GPa % and a strain hardening index n90 value greater than 0.20.

21. The process according to claim 14, which comprises one or more of the following features: a total time of the rapid heat treatment and hot-galvanizing of step D) is 30142 s; in step B), the coiling temperature is 580650 C.; in step C), the cold rolling reduction rate is 6080%; in step D), when the rapid heating is performed in one stage, the heating rate is 50300 C./s; in step D), the rapid heating is performed in two stages, wherein the strip steel or steel plate is heated in the first stage from room temperature to 550650 C. at a heating rate of 15300 C./s, heated in the second stage from 550650 C. to 750845 C. at a heating rate of 50300 C./s, or the strip steel or steel plate is heated in the first stage from room temperature to 550650 C. at a heating rate of 50300 C./s, heated in the second stage from 550650 C. to 750845 C. at a heating rate of 80300 C./s; in step D), the final temperature after rapid heating is 770830 C. or 790830 C.; in step D), the rapid cooling rate of the strip steel or steel plate is 50150 C./s; in the soaking process of step D), after the strip steel or steel plate is heated to the target temperature of dual phase region of austenite and ferrite, the temperature is kept unchanged for soaking; in the soaking process of step D), the strip steel or steel plate is slightly heated up or cooled down in the soaking time, wherein the temperature after heating is no more than 845 C. and the temperature after cooling is no less than 750 C.; the soaking time is 1040 s; the over ageing time is 20200 s; in step D), after alloying, the strip steel or steel plate is rapidly cooled to room temperature at a cooling rate of 30200 C./s to obtain an alloy galvannealed GA product.

22. The low carbon low alloy dual-phase steel with high formability or hot-galvanized dual-phase steel with high formability having a tensile strength of 590 MPa according to claim 10, wherein the hot-galvanized dual-phase steel with high formability is obtained by the following process: a) Smelting, casting wherein the above components are subjected to smelting and casting to form a slab; b) Hot rolling, coiling wherein a hot rolling finishing temperature is A.sub.r3; and a coiling temperature is 550680 C.; c) Cold rolling wherein a cold rolling reduction rate is 4085%; d) Rapid heat treatment, hot-galvanizing wherein the steel plate after cold rolling is rapidly heated to 750845 C., wherein the rapid heating is performed in one stage or two stages; when the rapid heating is performed in one stage, a heating rate is 50500 C./s; when the rapid heating is performed in two stages, the steel plate is heated in the first stage from room temperature to 550650 C. at a heating rate of 15500 C./s, heated in the second stage from 550650 C. to 750845 C. at a heating rate of 30500 C./s (such as 50500 C./s); then soaked at a soaking temperature of 750845 C. for a soaking time of 1060 s; wherein after soaking, the steel plate is slowly cooled to 670770 C. at a cooling rate of 515 C./s, then rapidly cooled to 460470 C. at a cooling rate of 50200 C./s, such as 50150 C./s, and immersed in a zinc pot for hot galvanizing; wherein after hot galvanizing, the steel plate is rapidly cooled to room temperature at a cooling rate of 30150 C./s to obtain a hot dip galvanized GI product; or after hot galvanizing, the steel plate is heated to 480550 C. at a heating rate of 30200 C./s and alloyed for 1020 s; after alloying, the steel plate is rapidly cooled to room temperature at a cooling rate of 30250 C./s to obtain an alloy galvannealed GA product.

Description

DESCRIPTION OF THE DRAWINGS

[0203] FIG. 1 is a microstructure photo of a dual-phase steel produced from test steel A of Example I according to Example 1 of the present disclosure.

[0204] FIG. 2 is a microstructure photo of a dual-phase steel produced from test steel A of Example I according to Traditional process 1 of the present disclosure.

[0205] FIG. 3 is a microstructure photo of a dual-phase steel produced from test steel F of Example I according to Example 6 of the present disclosure.

[0206] FIG. 4 is a microstructure photo of a dual-phase steel produced from test steel M of Example I according to Example 12 of the present disclosure.

[0207] FIG. 5 is a microstructure photo of a dual-phase steel produced from test steel S of Example I according to Example 23 of the present disclosure.

[0208] FIG. 6 is a microstructure photo of a dual-phase steel produced from test steel M of Example I according to Example 24 of the present disclosure.

[0209] FIG. 7 is a microstructure photo of a dual-phase steel produced from test steel A of Example II according to Example 1 of the present disclosure.

[0210] FIG. 8 is a microstructure photo of a dual-phase steel produced from test steel A of Example II according to Traditional process 1 of the present disclosure.

[0211] FIG. 9 is a microstructure photo of a dual-phase steel produced from test steel F of Example II according to Example 6 of the present disclosure.

[0212] FIG. 10 is a microstructure photo of a dual-phase steel produced from test steel M of Example II according to Example 12 of the present disclosure.

[0213] FIG. 11 is a microstructure photo of a dual-phase steel produced from test steel S of Example II according to Example 23 of the present disclosure.

[0214] FIG. 12 is a microstructure photo of a dual-phase steel produced from test steel M of Example II according to Example 24 of the present disclosure.

[0215] FIG. 13 is a microstructure photo of a hot dip galvanized dual-phase steel (GI) produced from test steel A of Example III according to Example 1 of the present disclosure.

[0216] FIG. 14 is a microstructure photo of a hot dip galvanized dual-phase steel (GI) produced from test steel A of Example III according to the present disclosure at a heating rate of Traditional process 1.

[0217] FIG. 15 is a microstructure photo of an alloy galvannealed dual-phase steel (GA) produced from test steel I of Example III according to Example 17 of the present disclosure.

[0218] FIG. 16 is a microstructure photo of a hot dip galvanized dual-phase steel (GI) produced from test steel D of Example III according to Example 22 of the present disclosure.

[0219] FIG. 17 is a microstructure photo of an alloy galvannealed dual-phase steel (GA) produced from test steel I of Example III according to Example 34 of the present disclosure.

[0220] FIG. 18 is a microstructure photo of a hot dip galvanized dual-phase steel (GI) produced from test steel A of Example IV according to Example 1 of the present disclosure.

[0221] FIG. 19 is a microstructure photo of a hot dip galvanized dual-phase steel (GI) produced from test steel A of Example IV according to Traditional process 1 of the present disclosure.

[0222] FIG. 20 is a microstructure photo of an alloy galvannealed dual-phase steel (GA) produced from test steel I of Example IV according to Example 17 of the present disclosure.

[0223] FIG. 21 is a microstructure photo of a hot dip galvanized dual-phase steel (GI) produced from test steel D of Example IV according to Example 22 of the present disclosure.

[0224] FIG. 22 is a microstructure photo of an alloy galvannealed dual-phase steel (GA) produced from test steel I of Example IV according to Example 34 of the present disclosure.

DETAILED DESCRIPTION

[0225] The present disclosure is further explained below in reference to the Examples and the accompanying drawings. The Examples are implemented in accordance with the technical solution of the present disclosure. Detailed embodiments and specific operation process are provided, but the protection scope of the present disclosure is not limited to the Examples described below.

[0226] In the Examples, yield strength, tensile strength and elongation were tested on P7 specimen transversely according to GB/T228.1-2010 Metallic materialsTensile testingPart 1: Method of test at room temperature. n90 was tested on the P7 specimen transversely according to GB/T228.1-2010 Metallic materialsTensile testingPart 1: Method of test at room temperature and n90 value was obtained according to GBT 5028-2008 Metallic materialsSheet and stripDetermination of tensile strain hardening exponent.

Example I

[0227] The composition of the test steel of the present disclosure is shown in Table 1. The specific parameters of the present example and the traditional processes are shown in Table 2 and Table 3. The main performances of the steel prepared from the test steel composition of this example according to the examples and the traditional processes are listed in Table 4 and Table 5.

[0228] It can be seen from Table 1-Table 5 that the rapid heat treatment process of the present disclosure can reduce the alloy content in the same grade of steel, refine grains, and obtain a matching of material structure and composition with strength and toughness. The dual-phase steel obtained by the process of the present disclosure has a yield strength of 350405 MPa, a tensile strength of 624706 MPa MPa, an elongation of 24.430.4%, a product of strength and elongation of 1720.1 GPa %, and a strain hardening index n.sub.90 value of greater than 0.20, which is higher than that of the dual-phase steel produced by the traditional process.

[0229] FIG. 1 is a structure photo of A steel having a typical composition obtained by Example 1, and FIG. 2 is a structure photo of A steel having a typical composition obtained by traditional process 1. It can be seen from the figures that there are very large differences in the structures treated by different heat treatment methods. The microstructure of the A steel after the rapid heat treatment process of this example has fine grains and is mainly composed of a fine martensitic structure and a small amount of carbide dispersed in ferrite matrix (FIG. 1). In the structure after treated by the process of the present disclosure, the grain structure of ferrite and martensite and carbide are very fine and evenly distributed in the matrix, which is very beneficial to the improvement of the strength and plasticity of the material. The A steel obtained by the traditional process treatment has a typical dual-phase steel microstructure (FIG. 2), that is, there is a small amount of black martensite structure on the grain boundary of white ferrite. Due to element segregation and other reasons, the material structure after traditional process treatment shows a certain directionality, and its ferrite structure is distributed in long strips along the rolling direction. The microstructure treated by the traditional process is characterized in that the grain size is relatively coarse, there is a certain banded structure with martensite and carbide distributed in a network along ferrite grain boundary, the ferrite grain is relatively coarse, and the distribution of dual-phase structure of ferrite and martensite is uneven.

[0230] FIG. 3 is a structure photo of F steel having a typical composition obtained by Example 6 (over ageing treatment), and FIG. 4 is a structure photo of M steel having a typical composition obtained by Example 12 (without over ageing treatment). FIG. 5 is a structure photo of S steel having a typical composition obtained by Example 23, and FIG. 6 is a structure photo of M steel having a typical composition obtained by Example 24. Examples 6, 12, 23, 24 all adopt processes with short heat treatment cycles. It can be seen from the figures that the removal of ageing treatment segment in the process of the present disclosure can also provide very uniform, fine, dispersed distribution of each phase structure. Therefore, the manufacturing process of the dual-phase steel of the present disclosure can refine grains, and make the structure of each phase of the material evenly distributed in the matrix, thereby improving the material structure and the material properties.

TABLE-US-00001 TABLE 1 unit: mass percentage test steel C Si Mn Cr Mo Ti Nb V P S Al A 0.04 0.1 1.60 / / / / / 0.010 0.015 0.020 B 0.055 0.21 1.56 / / / / / 0.012 0.011 0.032 C 0.08 0.23 1.35 / / / / / 0.018 0.008 0.043 D 0.10 0.30 1.00 / / / / / 0.015 0.0038 0.025 E 0.05 0.17 1.27 0.26 / / / / 0.011 0.013 0.030 F 0.06 0.25 1.60 / 0.16 / / / 0.013 0.005 0.027 G 0.08 0.18 1.35 / / 0.020 / / 0.019 0.012 0.046 H 0.10 0.28 1.10 / / / 0.023 / 0.020 0.014 0.055 I 0.09 0.19 1.20 / / / / 0.026 0.012 0.009 0.033 J 0.04 0.27 1.60 0.22 0.20 / / / 0.013 0.006 0.028 K 0.06 0.15 1.55 0.20 / 0.015 / / 0.014 0.005 0.025 L 0.10 0.18 1.40 0.23 / / 0.020 / 0.015 0.012 0.033 M 0.09 0.25 1.26 0.24 / / / 0.021 0.017 0.015 0.035 N 0.07 0.30 1.37 / 0.16 0.018 / / 0.019 0.011 0.044 0 0.08 0.13 1.60 / 0.13 / 0.015 / 0.02 0.0085 0.055 P 0.10 0.21 1.38 / 0.15 / / 0.020 0.015 0.0092 0.047 Q 0.08 0.12 1.57 / / 0.015 0.020 / 0.016 0.0075 0.060 R 0.10 0.20 1.59 / / 0.020 / 0.021 0.016 0.0022 0.053 S 0.09 0.23 1.44 / / / 0.015 0.020 0.013 0.0018 0.045

TABLE-US-00002 TABLE 2 Rapid heat treatment (one stage) Over ageing Hot Slow cooling Rapid cooling treatment Total rolling Cold Rapid Soaking Temper- Temper- Over time of Coiling rolling heating Soaking ature ature ageing Over Final rapid temper- reduction rate (one temper- Soaking Cooling after Cooling after temper- ageing Cooling heat ature rate stage) ature time rate cooling rate cooling ature time rate treat- C. % C./s C. s C./s C. C./s C. C. s C./s ment Ex. 1 680 45 50 810 60 15 695 50 240 240 180 30 279.90 Ex. 2 650 85 80 790 50 13 670 60 230 230 200 40 281.44 Ex. 3 610 75 150 770 40 11 680 80 235 235 150 50 213.04 Ex. 4 580 65 300 750 30 9 680 100 260 260 120 35 171.27 Ex. 5 550 70 500 815 10 6 700 120 280 280 110 38 151.10 Ex. 6 590 40 250 820 20 5 750 150 250 250 100 45 145.64 Ex. 7 640 50 350 845 55 12 770 140 238 238 80 43 152.48 Ex. 8 600 68 400 830 45 8 710 130 252 252 60 48 130.38 Ex. 9 570 60 230 825 35 10 730 110 270 270 40 33 99.76 Ex. 10 630 80 100 815 25 14 680 200 245 245 20 30 72.27 Ex. 11 660 77 180 800 30 7 690 170 20 30 53.99 Ex. 12 550 55 200 790 20 9 680 160 20 30 40.20 Traditional 680 85 11 750 160 10 675 100 230 230 290 30 535.31 process 1 Traditional 650 75 10 770 130 9 675 80 250 250 260 30 488.53 process 2 Traditional 610 65 11 800 110 10 675 75 240 240 230 30 436.54 process 3 Traditional 580 55 13 830 90 8 675 60 260 260 160 30 346.60 process 4 Traditional 550 40 15 845 70 12 675 50 280 280 180 30 332.40 process 5

TABLE-US-00003 TABLE 3 Rapid heat treatment (two-stage) Rapid heating (two-stage) Temperature Heating Slow cooling Hot Cold Heating after rate in Temper- rolling rolling rate in heating the Soaking ature Coiling reduction the first in the second Soaking Soaking Cooling after temperature rate stage first stage stage temper- time rate cooling C. % C/s. C. C/s. ature s C/s. C. Ex. 13 680 45 15 550 500 810 60 50 240 Ex. 14 650 85 30 570 300 790 50 60 230 Ex. 15 610 75 80 600 150 770 40 80 235 Ex. 16 580 65 150 630 80 750 30 100 260 Ex. 17 550 70 300 640 50 815 10 120 280 Ex. 18 590 40 500 650 30 820 20 150 250 Ex. 19 640 50 150 647 400 845 55 140 238 Ex. 20 600 68 250 635 250 830 45 130 252 Ex. 21 570 60 300 640 350 825 35 110 270 Ex. 22 630 80 250 620 250 815 25 200 245 Ex. 23 660 77 100 580 150 800 30 170 20 Ex. 24 550 55 200 610 200 790 20 160 20 Traditional 680 85 11 150 8 750 160 100 230 process 6 Traditional 650 75 10 150 7 770 130 80 250 process 7 Traditional 610 65 11 180 6 800 110 75 240 process 8 Traditional 580 55 13 210 5 830 90 60 260 process 9 Traditional 550 40 15 250 5 845 70 50 280 process 10 Rapid heat treatment (two-stage) Total Rapid cooling Over ageing treatment time of Temperature Over Over Final rapid Cooling after ageing ageing Cooling heat rate cooling temperature time rate treatment C/s. C. C. s C/s. s Ex. 13 50 240 240 180 30 299.95 Ex. 14 60 230 230 200 40 290.88 Ex. 15 80 235 235 150 50 216.43 Ex. 16 100 260 260 120 35 174.40 Ex. 17 120 280 280 110 38 155.08 Ex. 18 150 250 250 100 45 149.37 Ex. 19 140 238 238 80 43 152.01 Ex. 20 130 252 252 60 48 130.89 Ex. 21 110 270 270 40 33 98.34 Ex. 22 200 245 245 20 30 67.50 Ex. 23 170 20 / 56.72 Ex. 24 160 20 / 40.20 Traditional 100 230 230 290 30 555.77 process 6 Traditional 80 250 250 260 30 515.11 process 7 Traditional 75 240 240 230 30 483.51 process 8 Traditional 60 260 260 160 30 422.91 process 9 Traditional 50 280 280 180 30 415.07 process 10

TABLE-US-00004 TABLE 4 Main process Product of parameters Yield Tensile strength and test (Rapid heating-one strength strength Elongation elongation No. steel stage) MPa MPa % MPa % n90 value 1 A Traditional process 1 268 516 36 18576 0.191 2 A Ex. 1 354 658 28.8 18950.4 0.214 3 B Traditional process 2 268 491 36.5 17921.5 0.197 4 B Ex. 2 350 645 28.3 18253.5 0.211 5 C Traditional process 3 270 509 36.1 18374.9 0.189 6 C Ex. 3 365 663 28.4 18829.2 0.221 7 D Traditional process 4 285 539 35.4 19080.6 0.919 8 D Ex. 4 360 659 29 19111 0.212 9 E Traditional process 5 279 510 35.7 18207 0.181 10 E Ex. 5 364 673 28.5 19180.5 0.213 11 O Ex. 6 370 672 29 19488 0.216 12 0 Traditional process 4 281 547 32.6 17832.2 0.198 13 L Ex. 7 379 684 29.4 20109.6 0.213 14 L Traditional process 3 276 524 36.2 18968.8 0.187 15 H Ex. 4 392 660 27.8 18348 0.207 16 H Traditional process 4 279 510 35.5 18105 0.192 17 Q Ex. 2 352 631 30.4 19182.4 0.221 18 Q Traditional process 2 271 490 37.6 18424 0.195 19 I Ex. 3 379 698 25.7 17938.6 0.222 20 J Ex. 4 392 699 24.9 17405.1 0.224 21 N Ex. 5 376 691 25.5 17620.5 0.226 22 F Ex. 6 385 706 24.4 17226.4 0.22 23 K Ex. 7 390 640 28.1 17984 0.234 24 R Ex. 8 380 683 26 17758 0.21 25 G Ex. 9 403 697 26.3 18331.1 0.222 26 P Ex. 10 370 675 27 18225 0.201 27 S Ex. 11 368 680 26.6 18088 0.208 28 M Ex. 12 363 650 27.8 18070 0.212

TABLE-US-00005 TABLE 5 Main process Product of parameters Yield Tensile strength and test (Rapid heating- strength strength Elongation elongation n90 No. steel twostage) MPa MPa % MPa % value 1 A Traditional 264 527 33.8 17812.6 0.199 process 6 2 A Ex. 13 387 677 27.7 18752.9 0.214 3 B Traditional 285 517 36.1 18663.7 0.196 process 7 4 B Ex. 14 371 666 27.7 18448.2 0.226 5 C Traditional 297 522 34.4 17956.8 0.202 process 8 6 C Ex. 15 369 651 27.2 17707.2 0.211 7 D Traditional 268 517 36.5 18870.5 0.199 process 9 8 D Ex. 16 352 631 29.4 18551.4 0.223 9 E Traditional 265 516 36 18576 0.198 process 10 10 E Ex. 17 347 624 30.3 18907.2 0.213 11 O Ex. 18 354 687 27.8 19098.6 0.232 12 O Traditional 270 569 31.1 17695.9 0.189 process 9 13 L Ex. 19 405 658 25.8 16976.4 0.226 14 L Traditional 276 522 33.3 17382.6 0.197 process 8 15 H Ex. 16 364 650 28.3 18395 0.22 16 H Traditional 265 547 33 18051 0.191 process 9 17 Q Ex. 14 389 660 27.6 18216 0.232 18 Q Traditional 304 523 33.4 17468.2 0.191 process 7 19 I Ex. 15 390 641 27.9 17883.9 0.225 20 J Ex. 16 388 679 27.9 18944.1 0.232 21 N Ex. 17 360 648 29.1 18856.8 0.213 22 F Ex. 18 365 647 30.3 19604.1 0.226 23 K Ex. 19 392 649 27.2 17652.8 0.226 24 R Ex. 20 353 669 29 19401 0.226 25 G Ex. 21 349 638 28 17864 0.225 26 P Ex. 22 377 642 28.6 18361.2 0.216 27 S Ex. 23 397 692 28 19376 0.233 28 M Ex. 24 395 689 27 18603 0.223

Example II

[0231] The composition of the test steel of the present disclosure is shown in Table 6. The specific parameters of the present example and the traditional processes are shown in Table 7 and Table 8. The main performances of the steel prepared from the test steel composition of this example according to the examples and the traditional processes are listed in Table 9 and Table 10.

[0232] It can be seen from Table 6-Table 10 that the process of the present disclosure can reduce the alloy content in the same grade of steel, refine grains, and obtain a matching of material structure and composition with strength and toughness. The dual-phase steel obtained by the process of the present disclosure has a yield strength of 400533 MPa, a tensile strength of 781878 MPa MPa, an elongation of 19.524.1%, a product of strength and elongation of 16.319.3 GPa %, and a strain hardening index n.sub.90 value of greater than 0.20, which is higher than that of the dual-phase steel produced by the traditional process.

[0233] FIG. 7 is a structure photo of A steel having a typical composition obtained by Example 1, and FIG. 8 is a structure photo of A steel having a typical composition obtained by traditional process 1. It can be seen from the figures that there are very large differences in the structures treated by different heat treatment methods. The microstructure of the A steel after the rapid heat treatment process of this example is mainly composed of a fine, uniform martensitic structure and a small amount of carbide dispersed in ferrite matrix (FIG. 7). In the structure after treated by the process of the present disclosure, the grain structure of ferrite and martensite and carbide are very fine and evenly distributed in the matrix, which is very beneficial to the improvement of the strength and plasticity of the material. The A steel obtained by the traditional process treatment has a typical dual-phase steel microstructure (FIG. 8). That is, there is a small amount of black martensite structure on the grain boundary of white ferrite. Due to element segregation and other reasons, the material structure after traditional process treatment shows a certain directionality, and its ferrite structure is distributed in long strips along the rolling direction. The microstructure treated by the traditional process is characterized in that the grain size is relatively coarse, there is a certain banded structure with martensite and carbide distributed in a network along ferrite grain boundary, the ferrite grain is relatively coarse, and the distribution of dual-phase structure of ferrite and martensite is uneven.

[0234] FIG. 9 is a structure photo of F steel having a typical composition obtained by Example 6 (over ageing treatment), and FIG. 10 is a structure photo of M steel having a typical composition obtained by Example 12 (without over ageing treatment). FIG. 11 is a structure photo of S steel having a typical composition obtained by Example 23, and FIG. 12 is a structure photo of M steel having a typical composition obtained by Example 24. Examples 6, 12, 23, 24 all adopt processes with short heat treatment cycles. It can be seen from the figures that the removal of ageing treatment segment in the process of the present disclosure can also provide very uniform, fine, dispersed distribution of each phase structure. Therefore, the manufacturing process of the dual-phase steel of the present disclosure can refine grains, and make the structure of each phase of the material evenly distributed in the matrix, thereby improving the material structure and the material properties.

TABLE-US-00006 TABLE 6 (unit: mass percentage) test steel C Si Mn Cr Mo Ti Nb V P S Al A 0.05 0.50 2.00 / / / / / 0.010 0.0026 0.020 B 0.07 0.24 1.81 / / / / / 0.015 0.0025 0.035 C 0.10 0.33 1.52 / / / / / 0.015 0.0022 0.043 D 0.12 0.42 1.20 / / / / / 0.012 0.0018 0.055 E 0.05 0.44 1.41 0.25 / / / / 0.010 0.0025 0.022 F 0.06 0.35 1.63 / 0.18 / / / 0.014 0.0025 0.034 G 0.09 0.1 1.52 / / 0.040 / / 0.015 0.0021 0.042 H 0.11 0.42 1.44 / / / 0.033 / 0.012 0.0020 0.053 I 0.09 0.26 1.61 / / / 0.035 0.012 0.0022 0.043 J 0.05 0.43 1.23 0.22 0.20 / / / 0.010 0.0023 0.020 K 0.06 0.27 1.40 0.20 / 0.025 / / 0.015 0.0025 0.035 L 0.08 0.10 1.52 0.18 / / 0.05 / 0.015 0.0022 0.043 M 0.10 0.46 1.41 0.21 / / / 0.025 0.013 0.0019 0.055 N 0.07 0.50 1.52 / 0.15 0.028 / / 0.012 0.0023 0.043 O 0.08 0.18 1.71 / 0.18 / 0.025 / 0.010 0.0026 0.035 P 0.10 0.23 1.82 / 0.14 / / 0.050 0.015 0.0023 0.043 Q 0.08 0.19 1.72 / / 0.025 0.030 / 0.013 0.0025 0.035 R 0.10 0.22 1.83 / / 0.020 / 0.041 0.015 0.0021 0.043 S 0.09 0.31 1.65 / / / 0.025 0.030 0.012 0.0018 0.055

TABLE-US-00007 TABLE 7 Rapid heat treatment (one stage) Over ageing Hot Cold Rapid Slow cooling Rapid cooling treatment rolling rolling heating Soaking Tem- Tem- Over Total time Coiling re- rate Soaking perature perature ageing Over Final of rapid tem- duction (one tem- Soaking Cooling after Cooling after tem- ageing Cooling heat perature rate stage) perature time rate Cooling rate cooling perature time rate treatment C. % C./s C. s C./s C. C./s C. C. s C./s s Ex. 1 680 45 50 750 60 15 670 60 240 240 180 30 274.43 Ex. 2 650 85 80 770 50 13 690 50 230 230 200 40 279.98 Ex. 3 610 75 150 800 40 11 700 80 235 235 150 50 214.40 Ex. 4 580 65 300 830 30 9 730 160 260 260 120 35 173.61 Ex. 5 550 70 500 845 10 6 770 200 280 280 110 38 143.44 Ex. 6 590 40 250 835 20 5 750 180 250 250 100 45 148.15 Ex. 7 640 50 350 795 55 12 695 140 238 238 80 43 153.88 Ex. 8 600 68 400 780 45 8 740 130 252 252 60 48 120.49 Ex. 9 570 60 230 815 35 10 710 110 270 270 40 33 100.53 Ex. 10 630 80 100 830 25 14 680 145 245 245 20 30 74.31 Ex. 11 660 77 180 820 30 7 720 135 20 / / 30 53.92 Ex. 12 550 55 200 835 20 9 760 90 20 / / 30 40.63 Traditional 680 85 11 750 160 10 675 100 230 230 290 30 535.31 process 1 Traditional 650 75 10 770 130 9 675 80 250 250 260 30 488.53 process 2 Traditional 610 65 11 800 110 10 675 75 240 240 230 30 436.54 process 3 Traditional 580 55 13 830 90 8 675 60 260 260 160 30 346.60 process 4 Traditional 550 40 15 845 70 12 675 50 280 280 180 30 332.40 process 5

TABLE-US-00008 TABLE 8 Rapid heat treatment (two-stage) Rapid heating (two-stage) Tem- Total Heat- perature Heat- Over ageing time Hot Cold ing after ing Soaking Slow cooling Rapid cooling treatment of rolling rolling rate heating rate Soak- Tem- Tem- Over Final rapid Coiling re- in the in the in the ing Soak- Cool- perature Cool- perature ageing Over Cool- heat tem- duction first first second tem- ing ing after ing after tem- ageing ing treat- perature rate stage stage stage perature time rate cooling rate cooling perature time rate ment C. % C./s C. C./s C. s C./s C. C./s C. C. s C./s s Ex. 13 680 45 15 550 500 750 60 15 670 60 240 240 180 30 295.57 Ex. 14 650 85 30 570 300 770 50 13 690 50 230 230 200 40 289.60 Ex. 15 610 75 80 600 150 800 40 11 700 80 235 235 150 50 217.79 Ex. 16 580 65 150 630 80 830 30 9 730 160 260 260 120 35 177.47 Ex. 17 550 70 300 640 50 845 10 6 770 200 280 280 110 38 147.96 Ex. 18 590 40 500 650 30 835 20 5 750 180 250 250 100 45 152.32 Ex. 19 640 50 450 647 400 795 55 12 695 140 238 238 80 43 153.43 Ex. 20 600 68 350 635 450 780 45 8 740 130 252 252 60 48 120.67 Ex. 21 570 60 400 640 350 815 35 10 710 110 270 270 40 33 99.13 Ex. 22 630 80 250 620 250 830 25 14 680 145 245 245 20 30 69.45 Ex. 23 660 77 100 580 150 820 30 7 720 135 20 / / / 56.67 Ex. 24 550 55 200 610 200 835 20 9 760 90 20 / / / 40.63 Traditional 680 85 11 150 8 750 160 10 675 100 230 230 290 30 555.77 process 6 Traditional 650 75 10 150 7 770 130 9 675 80 250 250 260 30 515.11 process 7 Traditional 610 65 11 180 6 800 110 10 675 75 240 240 230 30 483.51 process 8 Traditional 580 55 13 210 5 830 90 8 675 60 260 260 160 30 422.91 process 9 Traditional 550 40 15 250 5 845 70 12 675 50 280 280 180 30 415.07 process 10

TABLE-US-00009 TABLE 9 Main process Product of parameters Yield Tensile strength and test (Rapid heating-one strength strength Elongation elongation n90 No steel stage) MPa MPa % MPa % value 1 A Traditional process 1 357 655 28.4 18602 0.165 2 A Ex. 1 487 807 22.1 17834.7 0.202 3 B Traditional process 2 361 665 27 17955 0.159 4 B Ex. 2 490 814 22.4 18233.6 0.221 5 C Traditional process 3 367 678 27.5 18645 0.174 6 C Ex. 3 495 798 22.5 17955 0.212 7 D Traditional process 4 339 670 26.6 17822 0.174 8 D Ex. 4 473 781 23.5 18353.5 0.213 9 E Traditional process 5 362 692 25.7 17784.4 0.16 10 E Ex. 5 509 807 22.6 18238.2 0.22 11 O Ex. 6 475 815 21.6 17604 0.205 12 O Traditional process 4 365 678 27.4 18577.2 0.161 13 L Ex. 7 508 797 23.6 18809.2 0.225 14 L Traditional process 3 357 617 27.3 16844.1 0.164 15 H Ex. 4 490 800 24.1 19280 0.231 16 H Traditional process 4 363 650 27.8 18070 0.171 17 Q Ex. 2 498 814 23.2 18884.8 0.215 18 Q Traditional process 2 368 680 26.6 18088 0.175 19 I Ex. 3 491 804 22.4 18009.6 0.223 20 J Ex. 4 513 802 21.1 16922.2 0.216 21 N Ex. 5 499 802 23.4 18766.8 0.224 22 F Ex. 6 502 813 21.6 17560.8 0.221 23 K Ex. 7 509 809 20.7 16746.3 0.223 24 R Ex. 8 511 820 20.3 16646 0.217 25 G Ex. 9 533 817 22 17974 0.213 26 P Ex. 10 530 814 23 18722 0.221 27 S Ex. 11 524 822 22.5 18495 0.231 28 M Ex. 12 518 829 21.7 17989.3 0.203

TABLE-US-00010 TABLE 10 Main process parameters Product of (Rapid Yield Tensile Elon- strength and test heating-two strength strength gation elongation n90 No. steel stage) MPa MPa % MPa % value 1 A Traditional process 6 343 716 20.6 14749.6 0.165 2 A Ex. 13 417 812 20.07 16296.84 0.224 3 B Traditional process 7 330 661 24.7 16326.7 0.173 4 B Ex. 14 419 816 22.7 18523.2 0.266 5 C Traditional process 8 343 693 25.7 17810.1 0.163 6 C Ex. 15 416 808 23.1 18664.8 0.271 7 D Traditional process 9 350 683 24 16392 0.175 8 D Ex. 16 400 798 22 17556 0.226 9 E Traditional process 10 401 688 24.3 16718.4 0.174 10 E Ex. 17 438 847 19.5 16516.5 0.233 11 O Ex. 18 434 827 21.7 17945.9 0.222 12 O Traditional process 9 422 716 23.7 16969.2 0.166 13 L Ex. 19 458 834 22.1 18431.4 0.246 14 L Traditional process 8 474 746 22.1 16486.6 0.173 15 H Ex. 16 487 858 21.2 18189.6 0.22 16 H Traditional process 9 421 723 23.8 17207.4 0.176 17 Q Ex. 14 457 862 21.5 18533 0.224 18 Q Traditional process 7 405 695 24.4 16958 0.174 19 I Ex. 15 479 841 21.3 17913.3 0.224 20 J Ex. 16 462 843 20.1 16944.3 0.222 21 N Ex. 17 440 812 22.1 17945.2 0.223 22 F Ex. 18 462 846 21.9 18527.4 0.236 23 K Ex. 19 465 856 20.4 17462.4 0.224 24 R Ex. 20 443 845 20.1 16984.5 0.214 25 G Ex. 21 476 853 21.5 18339.5 0.236 26 P Ex. 22 460 858 21.6 18532.8 0.216 27 S Ex. 23 483 878 20.4 17911.2 0.223 28 M Ex. 24 482 874 20.5 17917 0.223

Example III

[0235] The composition of the test steel of the present disclosure is shown in Table 11. The specific parameters of the present example and the traditional processes are shown in Table 12 (heating in one stage) and Table 13 (heating in two stages). The main performances of the hot-dip galvanized dual phase steel GI and GA prepared from the test steel composition of this example according to the examples and the traditional processes in Table 2 and Table 3 are listed in Table 14 and Table 15.

[0236] It can be seen from Table 11-Table 15 that the process of the present disclosure can reduce the alloy content in the same grade of steel and obtain a matching of material structure and composition with strength and toughness. The dual-phase steel obtained by the process of the present disclosure has a yield strength of 347405 MPa, a tensile strength of 624709 MPa MPa, an elongation of 22.230.3%, a product of strength and elongation of 15.719.6 GPa %, and a strain hardening index n.sub.90 value of greater than 0.21.

[0237] FIG. 13 and FIG. 14 are structure photos of A steel having a typical composition obtained by Example 1 and Comparative Traditional process 1. It can be seen from the figures that there are very big differences in the structure after hot-dip galvanizing. The A steel after rapid heat treatment of the present disclosure has a microstructure composed of fine, uniform martensitic structure and carbides dispersed on a fine ferritic matrix. In the microstructure of the steel after the process treatment of the present disclosure, ferritic, martensitic grain structure and carbide are very fine and evenly dispersed, which is very beneficial to the improvement of the strength and plasticity of the material. The A steel obtained by the traditional process treatment has a typical dual-phase steel microstructure (FIG. 2). That is, there is a small amount of black martensite structure on the grain boundary of large pieces of white ferrite. The microstructure treated by the traditional process is characterized in that the grain size is relatively coarse, martensite and carbide are distributed in a network along ferrite grain boundary, and the content of martensite is not high.

[0238] FIG. 15 is a structure photo of I steel having a typical composition obtained by Example 17 (GA), and FIG. 16 is a structure photo of D steel having a typical composition obtained by Example 22 (GI). FIG. 17 is a structure photo of I steel having a typical composition obtained by Example 34 (GA). Examples 17, 22, 34 all adopt processes with short heat treatment cycles. It can be seen from the figures that the hot-dip galvanizing process by rapid heat treatment of the present disclosure can also provide a very uniform, fine, dispersed distribution of each phase structure after alloying (FIG. 15 and FIG. 17). The manufacturing process of the hot-galvanized dual-phase steel of the present disclosure can refine grains and make the structure of each phase of the material evenly distributed in the matrix, thereby improving the material structure and the material properties.

TABLE-US-00011 TABLE 11 (unit: mass percentage) test steel C Si Mn Cr Mo Ti Nb V P S Al A 0.045 0.10 1.50 / / / / / 0.0105 0.0045 0.0272 B 0.055 0.21 1.46 / / / / / 0.0136 0.0059 0.0304 C 0.084 0.33 1.35 / / / / / 0.0124 0.0052 0.0402 D 0.105 0.40 1.00 / / / / / 0.0149 0.0056 0.0200 E 0.051 0.17 1.27 0.24 / / / / 0.0200 0.0059 0.0496 F 0.062 0.25 1.56 / 0.15 / / / 0.0136 0.0041 0.0550 G 0.082 0.18 1.35 / / 0.021 / / 0.0160 0.0044 0.0491 H 0.103 0.28 1.20 / / / 0.023 / 0.0150 0.0057 0.0377 I 0.098 0.19 1.16 / / / / 0.026 0.0156 0.0043 0.0508 J 0.046 0.27 1.48 0.23 0.07 / / / 0.0177 0.0051 0.0403 K 0.065 0.15 1.49 0.25 / 0.017 / / 0.0119 0.0024 0.0289 L 0.101 0.18 1.44 0.21 / / 0.020 / 0.0098 0.0035 0.0390 M 0.095 0.25 1.26 0.24 / / / 0.021 0.0095 0.0060 0.0251 N 0.076 0.36 1.37 / 0.17 0.022 / / 0.0103 0.0026 0.0378 O 0.088 0.13 1.50 / 0.14 / 0.015 0.0119 0.0059 0.0338 P 0.102 0.21 1.38 / 0.15 / / 0.020 0.0195 0.0060 0.0241 Q 0.085 0.32 1.47 / / 0.016 0.020 / 0.0137 0.0053 0.0425 R 0.102 0.28 1.49 / / 0.020 / 0.021 0.02 0.0048 0.0377 S 0.097 0.23 1.44 / / / 0.015 0.020 0.0141 0.0034 0.0365

TABLE-US-00012 TABLE 12 Total Rapid heat treatment (one stage) time of Hot Cold Rapid Soaking Slow cooling Rapid cooling Hot-dip rapid heat rolling rolling heating Soak- Tem- Tem- galva- Alloying Final treatment Coiling re- rate ing Soak- Cool- perature Cool- perature nizing Heat- tem- Cool- and tem- duction (one tem- ing ing after ing after tem- ing pera- ing hot-dip perature rate stage) perature time rate cooling rate cooling perature rate ture rate galvanizing C. % C./s C. s C./s C. C./s C. C. C./s C. times C./s s Ex. 1 680 40 50 750 60 15 670 50 460 460 / / / 100 88.53 Ex. 2 650 85 80 770 50 13 690 60 465 465 / / / 80 74.84 Ex. 3 610 70 150 790 40 11 700 80 470 470 / / / 75 62.19 Ex. 4 580 60 300 800 30 9 730 100 466 466 / / / 60 50.45 Ex. 5 550 65 500 840 10 15 770 120 467 467 / / / 50 29.58 Ex. 6 590 45 250 845 20 5 750 150 461 461 / / / 30 58.93 Ex. 7 640 55 350 795 55 12 695 140 468 468 / / / 140 70.37 Ex. 8 590 63 400 790 45 8 670 130 469 469 / / / 150 66.46 Ex. 9 570 55 230 815 35 10 675 100 460 460 / / / 120 58.27 Ex. 10 560 75 100 830 25 14 710 200 470 470 / / / 100 48.39 Ex. 11 600 72 180 820 30 7 675 170 465 465 / / / 130 61.36 Ex. 12 550 50 200 835 20 6 720 180 470 470 / / / 150 49.11 Ex. 13 680 40 50 750 60 15 670 50 460 460 30 480 20 30 122.93 Ex. 14 650 85 80 770 50 13 690 60 465 465 50 490 17 60 95.36 Ex. 15 610 70 150 790 40 11 710 80 470 470 100 510 15 90 76.25 Ex. 16 580 60 300 820 30 9 730 100 466 466 150 530 12 150 61.13 Ex. 17 550 65 500 845 10 6 770 120 467 467 200 550 10 250 39.21 Traditional 680 80 11 770 160 10 675 100 470 470 / / / 30 254.05 process 1 Traditional 650 76 10 790 130 9 675 80 465 465 / / / 60 229.82 process 2 Traditional 610 70 11 810 110 10 675 75 460 460 / / / 90 203.07 process 3 Traditional 580 65 13 830 90 8 675 60 470 470 / / / 120 178.85 process 4 Traditional 550 60 15 845 70 12 675 50 470 470 / / / 150 146.27 process 5 Traditional 680 80 12 770 160 10 675 100 470 470 12 480 20 30 270.22 process 6 Traditional 650 76 14 790 130 9 675 80 465 465 16 490 17 60 226.80 process 7 Traditional 610 70 10 810 110 10 675 75 460 460 10 510 15 90 230.81 process 8 Traditional 580 65 11 830 90 8 675 60 470 470 20 530 12 120 205.68 process 9 Traditional 550 60 15 845 70 12 675 50 470 470 25 550 10 150 160.00 process 10

TABLE-US-00013 TABLE 13 Rapid heat treatment (two-stage) Total Rapid heating time of (two-stage) rapid Tem- Slow Rapid heat Heat- pera- cooling cooling Hot- treat- Hot ing ture Heat- Soaking Tem- Tem- dip ment rolling Cold rate after ing Soak- pera- pera- galva- and Coiling rolling in heating rate ing ture ture nizing Alloying Final hot-dip tem- re- the in in the tem- Soak- Cool- after Cool- after tem- heat- tem- Cool- gal- pera- duction first the first second pera- ing ing cool- ing cool- pera- ing pera- ing va- ture rate stage stage stage ture time rate ing rate ing ture rate ture time rate nizing C. % C./s C. C./s C. s C./s C. C./s C. C. C./s C. s C./s s Ex. 18 680 40 15 550 500 750 60 15 670 50 460 460 / / / 100 109.67 Ex. 19 650 85 30 570 300 770 50 13 690 60 465 465 / / / 80 84.47 Ex. 20 610 70 80 600 150 790 40 11 700 80 470 470 / / / 75 65.57 Ex. 21 580 60 150 630 80 800 30 9 730 100 466 466 / / / 60 54.04 Ex. 22 550 65 300 640 50 840 10 15 770 120 467 467 / / / 50 32.20 Ex. 23 590 45 500 650 30 845 20 5 750 150 461 461 / / / 30 63.39 Ex. 24 640 55 250 647 200 795 55 12 695 140 468 468 / / / 140 71.40 Ex. 25 590 63 350 635 450 790 45 8 670 130 469 469 / / / 150 66.64 Ex. 26 570 55 400 640 350 815 35 10 675 100 460 460 / / 120 56.87 Ex. 27 560 75 250 620 250 830 25 14 710 200 470 470 / / / 100 43.01 Ex. 28 600 72 100 580 150 820 30 7 675 170 465 465 / / / 130 63.60 Ex. 29 550 50 200 610 200 835 20 6 720 180 470 470 / / / 150 48.23 Ex. 30 680 40 15 550 500 750 60 15 670 50 460 460 30 480 20 30 141.27 Ex. 31 650 85 30 570 300 770 50 13 690 60 465 465 50 490 17 60 104.24 Ex. 32 610 70 80 600 150 790 40 11 710 80 470 470 100 510 15 90 79.63 Ex. 33 580 60 150 630 80 820 30 9 730 100 466 466 150 530 12 150 64.91 Ex. 34 550 65 300 640 50 845 10 6 770 120 467 467 200 550 10 250 43.73 Traditional 680 80 11 150 8 770 160 10 675 100 470 470 / / / 30 275.87 process 11 Traditional 650 76 10 150 7 790 130 9 675 80 465 465 / / / 60 257.25 process 12 Traditional 610 70 11 180 6 810 110 10 675 75 460 460 / / / 90 250.80 process 13 Traditional 580 65 13 210 5 830 90 8 675 60 470 470 / / / 120 255.16 process 14 Traditional 550 60 15 250 5 845 70 12 675 50 470 470 / / / 150 225.60 process 15 Traditional 680 80 11 150 8 770 160 10 675 100 470 470 12 480 20 30 297.03 process 16 Traditional 650 76 10 150 7 790 130 9 675 80 465 465 16 490 17 60 276.23 process 17 Traditional 610 70 11 180 6 810 110 10 675 75 460 460 10 510 15 90 271.36 process 18 Traditional 580 65 13 210 5 830 90 8 675 60 470 470 20 530 12 120 270.66 process 19 Traditional 550 60 15 250 5 845 70 12 675 50 470 470 25 550 10 150 239.33 process 20

TABLE-US-00014 TABLE 14 Main process Product parameters of strength Type (Rapid Yield Tensile and test of the heating-one strength strength Elongation elongation n90 No. steel Product stage) MPa MPa % MPa % value 1 A Hot dip Traditional 271 490 33.6 16464 0.165 galvanized process 1 2 A Ex. 1 376 691 23.5 16238.5 0.249 3 B Traditional 271 497 34.5 17146.5 0.181 process 2 4 B Ex. 2 379 698 25.7 17938.6 0.254 5 C Traditional 265 517 36.5 18870.5 0.179 process 3 6 C Ex. 3 356 674 28.2 19006.8 0.26 7 D Traditional 293 521 32.6 16984.6 0.18 process 4 8 D Ex. 4 350 652 27.5 17930 0.249 9 E Traditional 297 560 34.3 19208 0.173 process 5 10 E Ex. 5 360 659 27 17793 0.251 11 N Ex. 6 373 692 23.3 16123.6 0.248 12 F Ex. 7 381 705 23 16215 0.243 13 K Ex. 8 392 709 22.2 15739.8 0.242 14 R Ex. 9 385 706 22.4 15814.4 0.25 15 G Ex. 10 370 672 28 18816 0.252 16 P Ex. 11 362 671 27.9 18720.9 0.253 17 S Ex. 12 360 674 24.7 16647.8 0.254 18 O Alloy Ex. 13 377 642 28.6 18361.2 0.232 19 O galvannealed Traditional 304 523 32.4 16945.2 0.189 process 6 20 L Ex. 14 392 699 25.9 18104.1 0.255 21 L Traditional 276 522 34.1 17800.2 0.177 process 7 22 H Ex. 15 349 638 28 17864 0.234 23 H Traditional 302 518 35.5 18389 0.174 process 8 24 Q Ex. 16 373 695 25 17375 0.248 25 Q Traditional 268 491 36.5 17921.5 0.171 process 9 26 I Ex. 17 356 659 28.4 18715.6 0.253 27 J Traditional 304 526 29.2 15359.2 0.181 process 10

TABLE-US-00015 TABLE 15 Main process Product of parameters strength and (Rapid Yield Tensile elongation test Type of the heating-two strength strength Elongation MPa n90 No. steel product stage) MPa MPa % % value 1 A Hot dip Traditional 264 527 33.8 17812.6 0.199 galvanized process 11 2 A Ex. 19 387 677 27.7 18752.9 0.214 3 B Traditional 285 517 36.1 18663.7 0.196 process 12 4 B Ex. 20 371 666 27.7 18448.2 0.226 5 C Traditional 297 522 34.4 17956.8 0.202 process 13 6 C Ex. 21 369 651 27.2 17707.2 0.211 7 D Traditional 268 517 36.5 18870.5 0.199 process 14 8 D Ex. 22 352 631 29.4 18551.4 0.223 9 E Traditional 265 516 36 18576 0.198 process 15 10 E Ex. 23 347 624 30.3 18907.2 0.213 11 N Ex. 18 360 648 29.1 18856.8 0.213 12 F Ex. 24 365 647 30.3 19604.1 0.226 13 K Ex. 25 392 649 27.2 17652.8 0.226 14 R Ex. 26 353 669 29 19401 0.226 15 G Ex. 27 349 638 28 17864 0.225 16 P Ex. 28 377 642 28.6 18361.2 0.216 17 S Ex. 29 397 692 28 19376 0.233 18 O Alloy Ex. 30 354 687 27.8 19098.6 0.232 19 O galvannealed Traditional 270 569 31.1 17695.9 0.189 process 16 20 L Ex. 31 405 658 25.8 16976.4 0.226 21 L Traditional 276 522 33.3 17382.6 0.197 process 17 22 H Ex. 32 364 650 28.3 18395 0.22 23 H Traditional 265 547 33 18051 0.191 process 18 24 Q Ex. 33 389 660 27.6 18216 0.232 25 Q Traditional 304 523 33.4 17468.2 0.191 process 19 26 I Ex. 34 390 641 27.9 17883.9 0.225 27 J Traditional 308 529 32.9 17404.1 0.182 process 20

Example IV

[0239] The composition of the test steel of Example IV is shown in Table 16. The specific parameters of the present example and the traditional processes are shown in Table 17 (heating in one stage) and Table 18 (heating in two stages). The main performances of the hot-dip galvanized dual phase steel GI and GA prepared from the test steel composition of the present disclosure according to the examples and the traditional processes in Table 17 and Table 18 are listed in Table 19 and Table 20.

[0240] It can be seen from Table 16-Table 20 that the process of the present disclosure can reduce the alloy content in the same grade of steel, refine grains, and obtain a matching of material structure and composition with strength and toughness. The dual-phase steel obtained by the process of the present disclosure has a yield strength of 400552 MPa, a tensile strength of 798862 MPa, an elongation of 19.524.6%, a product of strength and elongation of 16.319.9 GPa % and a strain hardening index n.sub.90 value of greater than 0.20.

[0241] FIG. 18 and FIG. 19 are structure photos of A steel having a typical composition obtained by Example 1 and Comparative Traditional process 1. It can be seen from the figures that there are very big differences in the structure after hot-dip galvanizing. The A steel after rapid heat treatment of the present disclosure has a microstructure composed of fine, uniform martensitic structure and carbides dispersed on a fine ferritic matrix (FIG. 18). The steel after the process treatment of the present disclosure has a microstructure that is characterized in that ferritic, martensitic grain structure and carbide are very fine and evenly dispersed, which is very beneficial to the improvement of the strength and plasticity of the material. The A steel after traditional process treatment (FIG. 19) has a typical dual-phase steel structure. That is, there is a small amount of black martensite structure on the grain boundary of large pieces of white ferrite. Due to element segregation and other reasons, the material structure after traditional process treatment shows a certain directionality, and its ferrite structure is distributed in long strips along the rolling direction. The microstructure treated by the traditional process is characterized in that the grain size is relatively coarse, there is a certain banded structure with martensite and carbide distributed in a network along ferrite grain boundary, the ferrite grain is relatively coarse, and the distribution of dual-phase structure of ferrite and martensite is uneven.

[0242] FIG. 20 is a structure photo of I steel having a typical composition obtained by Example 17 (GA), and FIG. 21 is a structure photo of D steel having a typical composition obtained by Example 22 (GI). FIG. 5 is a structure photo of I steel having a typical composition obtained by Example 34 (GA). Examples 17, 22, 34 all adopt processes with short heat treatment cycles. It can be seen from the figures that the hot-dip galvanizing process by rapid heat treatment of the present disclosure can also provide a very uniform, fine, dispersed distribution of each phase structure after alloying (FIG. 22), while Traditional process 9 provides coarse ferritic structure with a small amount of martensitic structure distributed on the ferrite grain boundary, which is a typical hot-dip galvanized dual-phase steel structure. The manufacturing process of the hot-galvanized dual-phase steel of the present disclosure can refine grains, and make the structure of each phase of the material evenly distributed in the matrix, thereby improving the material structure and the material properties.

TABLE-US-00016 TABLE 16 (unit: mass percentage) test steel C Si Mn Cr Mo Ti Nb V P S Al A 0.050 0.45 2.00 / / / / / 0.0135 0.0015 0.0314 B 0.070 0.20 1.91 / / / / / 0.0079 0.0020 0.0316 C 0.103 0.33 1.62 / / / / / 0.0144 0.0009 0.0269 D 0.120 0.42 1.41 / / / / / 0.0148 0.0012 0.0314 E 0.055 0.44 1.41 / / 0.0253 0.022 / 0.0118 0.0011 0.0340 F 0.068 0.35 1.63 / / / 0.023 0.031 0.0118 0.0015 0.0366 G 0.092 0.25 1.50 0.040 / 0.022 / 0.0115 0.0006 0.0297 H 0.099 0.42 1.44 / 0.033 / / / 0.0064 0.0028 0.0294 I 0.110 0.26 1.61 / / 0.0305 / 0.035 0.0143 0.0003 0.0358 J 0.103 0.43 1.23 / / / 0.02 / 0.0136 0.0018 0.0286 K 0.083 0.27 1.40 0.025 / / / / 0.0097 0.0030 0.0276 L 0.095 0.35 1.52 / 0.05 / / / 0.0095 0.0028 0.0303 M 0.078 0.45 1.41 / / 0.0276 0.025 0.0099 0.0003 0.0290 N 0.069 0.50 2.00 0.028 / / 0.022 / 0.0134 0.0008 0.0367 O 0.105 0.10 1.7 / 0.025 / / / 0.0099 0.0017 0.0290 P 0.094 0.23 1.82 / / / / 0.05 0.0124 0.0012 0.0259 Q 0.089 0.15 1.72 0.025 0.030 / / / 0.0096 0.0011 0.0319 R 0.095 0.18 1.83 0.020 / / / 0.032 0.0075 0.0015 0.0285 S 0.096 0.31 1.65 / 0.025 / / 0.03 0.0066 0.0007 0.0495

TABLE-US-00017 TABLE 17 Rapid heat treatment (one stage) Total time of Hot Cold Rapid Slow cooling Rapid cooling Hot-dip rapid heat rolling rolling heating Soaking Tem- Tem- gal- Alloying Final treatment Coiling re- rate Soaking Soak- Cool- perature Cool- perature vanizing heat- tem- Cool- and tem- duction (one tem- ing ing after ing after tem- ing pera- ing hot-dip perature rate stage) perature time rate cooling rate cooling perature rate ture time rate galvanizing C. % C./s C. s C./s C. C./s C. C. C./s C. s C./s s Ex. 1 680 40 50 750 60 15 670 50 460 460 / / / 100 88.53 Ex. 2 650 85 80 770 50 13 690 60 465 465 / / / 80 74.84 Ex. 3 610 70 150 790 40 11 700 80 470 470 / / / 75 62.19 Ex. 4 580 60 300 800 30 9 730 100 466 466 / / / 60 50.45 Ex. 5 550 65 500 840 10 15 770 120 467 467 / / / 50 29.58 Ex. 6 590 45 250 845 20 5 750 150 461 461 / / / 30 58.93 Ex. 7 640 55 350 795 55 12 695 140 468 468 / / / 140 70.37 Ex. 8 590 63 400 790 45 8 670 130 469 469 / / / 150 66.46 Ex. 9 570 55 230 815 35 10 675 100 460 460 / / / 120 58.27 Ex. 10 560 75 100 830 25 14 710 200 470 470 / / / 100 48.39 Ex. 11 600 72 180 820 30 7 675 170 465 465 / / / 130 61.36 Ex. 12 550 50 200 835 20 6 720 180 470 470 / / / 150 49.11 Ex. 13 680 40 50 750 60 15 670 50 460 460 30 480 20 30 122.93 Ex. 14 650 85 80 770 50 13 690 60 465 465 50 490 17 60 95.36 Ex. 15 610 70 150 790 40 11 710 80 470 470 100 510 15 90 76.25 Ex. 16 580 60 300 820 30 9 730 100 466 466 150 530 12 150 61.13 Ex. 17 550 65 500 845 10 6 770 120 467 467 200 550 10 250 39.21 Traditional 680 80 11 770 160 10 675 100 470 470 / / / 30 254.05 process 1 Traditional 650 76 10 790 130 9 675 80 465 465 / / / 60 229.82 process 2 Traditional 610 70 11 810 110 10 675 75 460 460 / / / 90 203.07 process 3 Traditional 580 65 13 830 90 8 675 60 470 470 / / / 120 178.85 process 4 Traditional 550 60 15 845 70 12 675 50 470 470 / / / 150 146.27 process 5 Traditional 680 80 12 770 160 10 675 100 470 470 12 480 20 30 270.22 process 6 Traditional 650 76 14 790 130 9 675 80 465 465 16 490 17 60 226.80 process 7 Traditional 610 70 10 810 110 10 675 75 460 460 10 510 15 90 230.81 process 8 Traditional 580 65 11 830 90 8 675 60 470 470 20 530 12 120 205.68 process 9 Traditional 550 60 15 845 70 12 675 50 470 470 25 550 10 150 160.00 process 10

TABLE-US-00018 TABLE 18 Rapid heat treatment (two-stage) Total Rapid heating time of (two-stage) rapid Hot Cold Tem- heat rolling rol- Heat- perature Heat- Soaking Slow cooling Rapid cooling treat- Coil- ling ing after ing Soak Tem- Tem- Hot-dip ment ing re- rate in heating rate ing pera- pera- gal- Alloying Final and tem- duc- the in the in the tem- Soak- Cool- ture Cool- ture vanizing Heat- tem- Cool- hot-dip pera- tion first first second pera- ing ing after ing after tem- ing pera- ing gal- ture rate stage stage stage ture time rate cooling rate cooling perature rate ture time rate vanizing C. % C./s C. C./s C. s C./s C. C./s C. C. C./s C. s C./s s Ex. 18 680 40 15 550 500 750 60 15 670 50 460 460 / / / 100 109.67 Ex. 19 650 85 30 570 300 770 50 13 690 60 465 465 / / / 80 84.47 Ex. 20 610 70 80 600 150 790 40 11 700 80 470 470 / / / 75 65.57 Ex. 21 580 60 150 630 80 800 30 9 730 100 466 466 / / / 60 54.04 Ex. 22 550 65 300 640 50 840 10 15 770 120 467 467 / / / 50 32.20 Ex. 23 590 45 500 650 30 845 20 5 750 150 461 461 / / / 30 63.39 Ex. 24 640 55 250 647 200 795 55 12 695 140 468 468 / / / 140 71.40 Ex. 25 590 63 350 635 450 790 45 8 670 130 469 469 / / / 150 66.64 Ex. 26 570 55 400 640 350 815 35 10 675 100 460 460 / / / 120 56.87 Ex. 27 560 75 250 620 250 830 25 14 710 200 470 470 / / / 100 43.01 Ex. 28 600 72 100 580 150 820 30 7 675 170 465 465 / / / 130 63.60 Ex. 29 550 50 200 610 200 835 20 6 720 180 470 470 / / / 150 48.23 Ex. 30 680 40 15 550 500 750 60 15 670 50 460 460 30 480 20 30 141.27 Ex. 31 650 85 30 570 300 770 50 13 690 60 465 465 50 490 17 60 104.24 Ex. 32 610 70 80 600 150 790 40 11 710 80 470 470 100 510 15 90 79.63 Ex. 33 580 60 150 630 80 820 30 9 730 100 466 466 150 530 12 150 64.91 Ex. 34 550 65 300 640 50 845 10 6 770 120 467 467 200 550 10 250 43.73 Traditional 680 80 11 150 8 770 160 10 675 100 470 470 / / / 30 275.87 process 11 Traditional 650 76 10 150 7 790 130 9 675 80 465 465 / / / 60 257.25 process 12 Traditional 610 70 11 180 6 810 110 10 675 75 460 460 / / / 90 250.80 process 13 Traditional 580 65 13 210 5 830 90 8 675 60 470 470 / / / 120 255.16 process 14 Traditional 550 60 15 250 5 845 70 12 675 50 470 470 / / / 150 225.60 process 15 Traditional 680 80 11 150 8 770 160 10 675 100 470 470 12 480 20 30 297.03 process 16 Traditional 650 76 10 150 7 790 130 9 675 80 465 465 16 490 17 60 276.23 process 17 Traditional 610 70 11 180 6 810 110 10 675 75 460 460 10 510 15 90 271.36 process 18 Traditional 580 65 13 210 5 830 90 8 675 60 470 470 20 530 12 120 270.66 process 19 Traditional 550 60 15 250 5 845 70 12 675 50 470 470 25 550 10 150 239.33 process 20

TABLE-US-00019 TABLE 19 Main process Product of parameters Yield Tensile strength and test Type of the (Rapid heating-one strength strength Elongation elongation n90 No. steel product stage) MPa MPa % MPa % value 1 A Hot dip Traditional process 1 380 683 23 15709 0.164 2 A galvanized Ex. 1 498 814 23.2 18884.8 0.226 3 B GI Traditional process 2 390 640 24.1 15424 0.155 4 B Ex. 2 504 810 23.6 19116 0.217 5 C Traditional process 3 389 660 23.6 15576 0.165 6 C Ex. 3 500 813 23.2 18861.6 0.21 7 D Traditional process 4 388 649 23.9 15511.1 0.161 8 D Ex. 4 511 814 23.8 19373.2 0.211 9 E Traditional process 5 390 641 24.9 15960.9 0.168 10 E Ex. 5 514 808 23.4 18907.2 0.215 11 N Ex. 6 547 848 22.7 19249.6 0.231 12 F Ex. 7 552 824 23.2 19116.8 0.223 13 K Ex. 8 535 852 22.4 19084.8 0.235 14 R Ex. 9 513 816 23.2 18931.2 0.213 15 G Ex. 10 538 848 21.2 17977.6 0.228 16 P Ex. 11 520 820 22.3 18286 0.211 17 S Ex. 12 501 823 23 18929 0.237 18 O Alloy Ex. 13 510 828 23.8 19706.4 0.212 19 O galvannealed Traditional process 6 392 699 21.9 15308.1 0.168 20 L GA Ex. 14 526 833 22.4 18659.2 0.228 21 L Traditional process 7 385 706 22.4 15814.4 0.169 22 H Ex. 15 509 807 24.6 19852.2 0.214 23 H Traditional process 8 376 691 21.5 14856.5 0.164 24 Q Ex. 16 536 821 23 18883 0.213 25 Q Traditional process 9 392 669 22.2 14851.8 0.169 26 I Ex. 17 551 829 22.2 18403.8 0.216 27 J Traditional process 10 402 721 23.4 16871.4 0.188

TABLE-US-00020 TABLE 20 Main process parameters Product of (Rapid Yield Tensile strength and test Type of the heating- strength strength Elongation elongation n90 No. steel product two stage) MPa MPa % MPa % value 1 A Hot dip Traditional 343 716 20.6 14749.6 0.165 galvanized process 11 2 A GI Ex. 19 417 812 20.07 16296.84 0.224 3 B Traditional 330 661 24.7 16326.7 0.173 process 12 4 B Ex. 20 419 816 22.7 18523.2 0.266 5 C Traditional 343 693 25.7 17810.1 0.163 process 13 6 C Ex. 21 416 808 23.1 18664.8 0.271 7 D Traditional 350 683 24 16392 0.175 process 14 8 D Ex. 22 400 798 22 17556 0.226 9 E Traditional 401 688 24.3 16718.4 0.174 process 15 10 E Ex. 23 438 847 19.5 16516.5 0.233 11 N Ex. 18 465 856 20.4 17462.4 0.224 12 F Ex. 24 434 827 21.7 17945.9 0.222 13 K Ex. 25 440 812 22.1 17945.2 0.223 14 R Ex. 26 474 834 22.1 18431.4 0.246 15 G Ex. 27 479 841 21.3 17913.3 0.224 16 P Ex. 28 487 858 21.2 18189.6 0.22 17 S Ex. 29 476 853 21.5 18339.5 0.236 18 O Alloy Ex. 30 457 862 21.5 18533 0.224 19 O galvannealed Traditional 458 746 22.1 16486.6 0.173 GA process 16 20 L Ex. 31 462 843 20.1 16944.3 0.222 21 L Traditional 453 734 23 16898.2 0.181 process 17 22 H Ex. 32 462 846 21.9 18527.4 0.236 23 H Traditional 422 716 23.7 16969.2 0.166 process 18 24 Q Ex. 33 443 845 20.1 16984.5 0.214 25 Q Traditional 421 723 23.8 17207.4 0.176 process 19 26 I Ex. 34 460 858 21.6 18532.8 0.216 27 J Traditional 405 695 24.4 16958 0.174 process 20