600 MPa yield strength-graded, high-stretchability hot-dip aluminum-zinc and color-coated steel plate and manufacturing method therefor

Abstract

An aluminium-zinc-hot-dipped and colour-coated steel plate having a 600 MPa yield strength grade and a high elongation and a manufacturing method thereof, with the chemical components in mass percentage of a substrate of the steel plate being: 0.07-0.15% of C, 0.02-0.5% of Si, 1.3-1.8% of Mn, N0.004%, S0.01%, Ti0.20%, Nb0.060%, and the balance being Fe and other inevitable impurities, and meanwhile satisfying the conditions of: (C+Mn/6)0.3%; Mn/S150; Nb satisfying 0.01%(Nb0.22C1.1N)0.06% where no Ti is contained; Ti satisfying 0.5Ti/C1.5 where no Nb is contained; and 0.04%(Ti+Nb)0.26% where Ti and Nb are added in combination. The steel plate has a yield strength of 600 MPa, a tensile strength of 650 MPa, an elongation after fracture of 12%, a good strength and toughness and an excellent corrosion resistance.

Claims

1. An aluminum-zinc-hot-dipped steel plate having a yield strength of 600 MPa and a high elongation, wherein the steel plate comprises chemical components (in mass percentage) consisting of: 0.07-0.15% of C, 0.02-0.5% of Si, 1.3-1.8% of Mn, N0.004%, S0.01%, Ti0.20%, Nb0.060%, and the balance being Fe and other inevitable impurities, wherein said chemical components satisfy formulae provided as follows: (C+Mn/6)0.3%; Mn/S150; 0.01%(Nb0.22C1.1 N)0.06%; 0.5Ti/C1.5; and 0.04%(Ti+Nb)0.26%; and wherein the steel plate's microstructure is a complex phase structure consisting of ferrite, cementite, bainite, martensite, deformed banded grains, and fine precipitates.

2. The aluminum-zinc-hot-dipped steel plate of claim 1, wherein said steel plate has a tensile strength of 650 MPa and an elongation after fracture of 12%.

3. The aluminum-zinc-hot-dipped steel plate of claim 2, wherein the aluminum-zinc-hot-dipped steel plate has fine uniform silver-white spangles on its surface.

4. The aluminum-zinc-hot-dipped steel plate of claim 3, wherein the spangles have a grain diameter that is less than 5 mm.

5. The aluminum-zinc-hot-dipped steel plate of claim 1, wherein the aluminum-zinc-hot-dipped steel plate has fine uniform silver-white spangles on its surface.

6. The aluminum-zinc-hot-dipped steel plate of claim 5, wherein the spangles has a grain diameter that is less than 10 mm.

7. A color-coated steel plate manufactured by color-coating the aluminum-zinc hot dipped steel plate of claim 1.

8. The color-coated steel plate of claim 7, wherein the coating layer comprises fluorocarbon, polyester, silicon-modified polyester, highly weather resistant polyester, or polyvinylidene fluoride.

9. A method for manufacturing the aluminum-zinc-hot-dipped steel plate-of claim 1, said method comprising the steps of: 1) smelting and casting the components according to claim 1 to obtain a cast slab; 2) hot-rolling and pickling the cast slab from step 1), wherein the heating tapping temperature is 1150-1280 C., the finish rolling temperature of the hot rolling is 800-900 C. and the hot rolling coiling temperature is 500-650 C.; and the cooling method after the hot rolling is water cooling; 3) cold-rolling to form a steel strip with a rolling reduction of 60-80%; 4) continuous annealing in a non-oxidation continuous annealing aluminum-zinc-hot-dipping furnace comprising a direct-fired heating section, a radiant tube heating section, a soaking section, a cooling section before hot-dipping, a hot tension roller zone and a hot-dipping section, and cooling after hot-dipping, wherein the duration in the direct-fired heating section is 20-60 s, with the heating temperature being 650-710 C.; the duration in the radiant tube heating section is 30-60 s, with the heating temperature being 750-840 C.; the duration in the temperature holding section is 1-10 s, with the soaking temperature being 750-840 C.; the duration in an cooling after hot-dipping section is 8-15 s; the duration in the hot tension roller zone and the hot-dipping section is 8-12 s; and the cooling rate of the cooling after hot-dipping rate is 20 C./s; 5) hot-dipping the steel strip in a zinc pot for a hot-dipping treatment to obtain a high-strength low-alloy aluminum-zinc-hot-dipped steel strip, with the components in weight percentage of the hot-dipping liquid being: 48-58% of Al, 40-50% of Zn, 1.0-2.0% of Si, 0.005-0.050% of Ti and the balance being inevitable impurities and the zinc pot temperature being 550-610 C.; and 6) skin pass rolling and withdrawing-straightening the steel strip with a temper rolling ratio being 0.25%0.2 and a withdrawing-straightening ratio being 0.2%0.2.

10. The method of claim 9, further comprising step 7): color-coating to obtain a color-coated steel plate, wherein the coating layer comprises fluorocarbon, polyester, silicon-modified polyester, highly weather resistant polyester, or polyvinylidene fluoride.

11. The method of claim 10, wherein, after being color-coated, the coating surface does not have the defects of bubbles, cracks and holidays.

12. The method of claim 9 wherein gas jet cooling or gas-mist jet cooling is used for the cooling after hot-dipping in step 4).

13. The method of claim 9, wherein said steel plate has a tensile strength of 650 MPa and an elongation after fracture of 12%.

14. The method of claim 9, wherein the aluminum-zinc-hot-dipped steel plate has fine uniform silver-white spangles on its surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a metallograph of a steel substrate of Example 1 of the present invention.

(2) FIG. 2 is a metallograph of a steel substrate of Example 2 of the present invention.

(3) FIG. 3 is a metallograph of a steel substrate of Example 3 of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(4) The present invention is further described in detail in conjunction with the accompanying drawings and examples.

(5) Table 1 relates to the chemical compositions of the steel substrate of the steel strip and dipping layers of the examples of the present invention, with the balances being Fe and inevitable impurities.

(6) Table 2 relates to the hot-rolling and cold-rolling process conditions of the examples of the present invention, and Table 3 relates to the continuous annealing process conditions of the examples of the present invention.

(7) Table 4 relates to the mechanical properties of the steel plates of the examples of the present invention.

(8) TABLE-US-00001 TABLE 1 Percentage by weight (wt %) Steel substrate composition Dipping layer composition C Si Mn N S Ti Nb Al Zn Si Ti Example 1 0.12 0.075 1.5 0.0015 0.008 0.001 0.045 48 50 1 0.01 Example 2 0.08 0.05 1.7 0.0018 0.006 0.001 0.045 54 44 1 0.01 Example 3 0.15 0.3 1.4 0.0031 0.01 0.087 0.011 52 45 2 0.05 Example 4 0.10 0.2 1.6 0.001 0.009 0.17 0.001 51 47 1 0.02 Example 5 0.13 0.09 1.5 0.004 0.008 0.001 0.051 52 46 1 0.03 Example 6 0.12 0.09 1.5 0.004 0.008 0.04 0.035 51 47 1 0.03

(9) TABLE-US-00002 TABLE 2 Heating Finish rolling Coiling Cold tapping temper- temperature of temper- rolling ature/ C. hot rolling/ C. ature/ C. reduction/% Example 1 1230 860 550 80 Example 2 1220 850 600 62 Example 3 1260 880 650 71 Example 4 1170 890 630 66 Example 5 1190 840 590 70 Example 6 1160 810 510 72

(10) TABLE-US-00003 TABLE 3 Cooling rate of the Temperature Duration Temperature Duration cooling in in in radiant in after direct-fired direct-fired heating radiant Holding Holding hot-dipping section/ C. section/s section/ C. section/s temperature/ C. time/s rate/ C. s Example 1 660 28 770 38 770 3 30 Example 2 700 32 820 44 820 4 25 Example 3 680 31 780 42 780 4 31 Example 4 680 31 835 42 835 4 31 Example 5 680 46 760 48 760 7 31 Example 6 680 31 780 42 780 3 31

(11) TABLE-US-00004 TABLE 4 Yield Tensile strength/ strength/ Elongation/ Thickness/ MPa MPa % mm Example 1 640 678 13.5 0.6 Example 2 627 711 13.5 0.8 Example 3 619 702 13.4 0.75 Example 4 623 708 14.5 0.7 Example 5 641 685 13.2 0.65 Example 6 611 680 14.2 0.7

Example 1

(12) This example relates to a method for manufacturing an aluminium-zinc-hot-dipped and colour-coated steel plate having a 600 MPa yield strength grade and a high elongation, with the steel plate having a thickness of 0.6 mm after being colour-coated, the method comprising the steps of:

(13) 1) smelting: performing molten iron desulphurization, converter smelting and casting to obtain a cast slab having chemical components in weight percentage: 0.12% of C, 0.075% of Si, 1.5% of Mn, 0.0015% of N, 0.008% of S, 0.001% of Ti, 0.045% of Nb, and the balance being Fe and other inevitable impurities;

(14) 2) hot-rolling and pickling

(15) wherein the heating tapping temperature is 1230 C., the finish rolling temperature of hot rolling is 860 C. and the hot rolling coiling temperature is 550 C., wherein water quenching cooling is carried out before coiling, and the hot-rolled plate has a thickness of 2.7 mm;

(16) 3) cold-rolling, wherein the overall reduction rate is controlled to 80%, and the cold-rolled plate has a thickness of 0.56 mm;

(17) 4) continuous annealing

(18) performing continuous annealing in a non-oxidation continuous annealing furnace comprising a direct-fired heating section, a radiant tube heating section, a soaking treatment and a cooling treatment. The duration in the direct-fired heating section is 28 s; the heating temperature is 660 C., and the induction heating time is 38 s; the soaking temperature is 770 C., and the soaking time is 3 s; the cooling temperature is 600 C., and the cooling time is 11 s; and the holding temperature is low so that a certain cold-rolled structure retains, strengthening the substrate.

(19) 5) aluminium-zinc-hot-dipping, wherein the hot-dipped aluminium-zinc metal layers on both sides are controlled to a weight of 150 g/m.sup.2, with the components of the dipping layer being, in weight percentage: 48% of Al, 50% of Zn, 1% of Si, 0.01% of Ti, and the balance being impurities; the temperature of the strip steel when entering the zinc pot is controlled at 600 C. and the temperature of an aluminium zinc liquid is controlled at 580 C.; the cooling after hot-dipping method is cold-gas jet cooling; a rapid cooling method is used, and the substrate is an uniform complex phase structure of ferrite+cementite+bainite+martensite+some deformed banded grains+fine precipitates (see FIG. 1);

(20) 6) skin pass rolling, withdrawing-straightening and coiling for use;

(21) 7) optionally Colour-coating, wherein the final product has a thickness of 0.6 mm.

(22) After test detection, the yield strength RP.sub.0.2 is 640 MPa, the tensile strength Rm is 678 MPa, and the elongation after fracture A80 mm is 13.5%.

Example 2

(23) This example relates to a method for manufacturing an aluminium-zinc-hot-dipped and colour-coated steel plate having a 600 MPa yield strength grade and a high elongation, with the steel plate having a thickness of 0.8 mm after being colour-coated, the method comprising the steps of:

(24) 1) smelting: performing molten iron desulphurization, converter smelting and casting to obtain a cast slab having chemical components in weight percentage: 0.08% of C, 0.05% of Si, 1.7% of Mn, 0.0018% of N, 0.006% of S, 0.001% of Ti, 0.045% of Nb, and the balance of Fe and other inevitable impurities;

(25) 2) hot-rolling and Pickling

(26) wherein the heating tapping temperature is 1220 C., the finish rolling temperature of hot rolling is 850 C. and the hot rolling coiling temperature is 600 C. Water quenching cooling is carried out before coiling; and the hot-rolled plate has a thickness of 2.0 mm;

(27) 3) cold-rolling, wherein the overall reduction rate is controlled to 62%, and the cold-rolled plate has a thickness of 0.76 mm; and a lower reduction can increase the recrystallization temperature and increase the recrystallization completion time, and with this process, a certain cold-rolled structure retains, strengthening the substrate.

(28) 4) continuous annealing

(29) performing continuous annealing in a non-oxidation continuous annealing furnace comprising a direct-fired heating section, a radiant tube heating section, a soaking treatment and a cooling treatment, wherein the duration in the direct-fired heating section is 32 s; the heating temperature is 700 C., and the induction heating time is 44 s; the soaking temperature is 820 C., and the soaking time is 4 s; and the cooling temperature is 590 C., and the cooling time is 12 s;

(30) 5) aluminium-zinc hot-dipping

(31) wherein the hot-dipped aluminium-zinc metal layers on both sides are controlled to a weight of 150 g/m.sup.2, with the components of the dipping layer being, in weight percentage: 54% of Al, 44% of Zn, 1% of Si and 0.01% of Ti; and the temperature of the strip steel when entering the zinc pot is controlled at 600 C. and the temperature of an aluminium zinc liquid is controlled at 590 C. The cooling after hot-dipping is gas-mist jet cooling. A rapid cooling method is used, and the substrate is a uniform complex phase structure of ferrite+cementite+a small amount of bainite+a small amount of martensite+a small amount of deformed banded grains+fine precipitates (see FIG. 2);

(32) 6) skin pass rolling, withdrawing-straightening and coiling for use;

(33) 7) colour-coating. The final product has a thickness of 0.8 mm.

(34) After test detection, the yield strength RP.sub.0.2 is 627 MPa, the tensile strength Rm is 711 MPa, and the elongation after fracture A80 mm is 13.5%.

Example 3

(35) This example relates to a method for manufacturing an aluminium-zinc-hot-dipped and colour-coated steel plate having a 600 MPa yield strength grade and a high elongation, with the steel plate having a thickness of 0.75 mm after being colour-coated, the method comprising the steps of:

(36) 1) smelting: performing molten iron desulphurization, converter smelting and casting to obtain a cast slab having chemical components in weight percentage: 0.15% of C, 0.3% of Si, 1.4% of Mn, 0.0031% of N, 0.01% of S, 0.087% of Ti, 0.011% of Nb, and the balance of Fe and other inevitable impurities;

(37) 2) hot-rolling and pickling

(38) wherein the heating tapping temperature is 1230 C., the finish rolling temperature of hot rolling is 880 C. and the hot rolling coiling temperature is 650 C.; water quenching cooling is carried out before coiling; and the hot-rolled plate has a thickness of 2.6 mm;

(39) 3) cold-rolling, wherein the overall reduction rate is controlled to 71%, and the cold-rolled plate has a thickness of 0.72 mm; the reduction is proper.

(40) 4) continuous annealing

(41) performing continuous annealing in a non-oxidation continuous annealing furnace comprising a direct-fired heating section, a radiant tube heating section, a soaking treatment and a cooling treatment, wherein the duration in the direct-fired heating section is 31 s; the heating temperature is 680 C., and the induction heating time is 42 s; the soaking temperature is 780 C., and the soaking time is 4 s; and the cooling temperature is 600 C., and the cooling time is 11 s;

(42) 5) aluminium-zinc hot-dipping

(43) wherein the hot-dipped aluminium-zinc metal layers on both sides are controlled to a weight of 150 g/m.sup.2, with the components of the dipping layer being, in weight percentage: 52% of Al, 45% of Zn, 2% of Si and 0.05% of Ti; the temperature of the strip steel when entering the zinc pot is controlled at 600 C. and the temperature of an aluminium zinc liquid is controlled at 600 C.; the cooling after hot-dipping is gas-mist jet cooling; and a rapid cooling method is used, and the substrate is an uniform complex phase structure of ferrite+cementite+bainite+martensite+deformed banded grains+fine precipitates (see FIG. 3);

(44) 6) skin pass rolling, withdrawing-straightening and coiling for use; and

(45) 7) colour-coating; wherein the final product has a thickness of 0.75 mm.

(46) After test detection, the yield strength RP.sub.0.2 is 619 MPa, the tensile strength Rm is 702 MPa, and the elongation after fracture A80 mm is 13.4%.

Example 4

(47) This example relates to a method for manufacturing an aluminium-zinc-hot-dipped and colour-coated steel plate having a 600 MPa yield strength grade and a high elongation, with the steel plate having a thickness of 0.7 mm after being colour-coated, the method comprising the steps of:

(48) 1) smelting: performing molten iron desulphurization, converter smelting and casting to obtain a cast slab having chemical components in weight percentage: 0.10% of C, 0.2% of Si, 1.6% of Mn, 0.001% of N, 0.009% of S, 0.17% of Ti, 0.001% of Nb, and the balance being Fe and other inevitable impurities;

(49) 2) hot-rolling and pickling

(50) wherein the heating tapping temperature is 1170 C., the finish rolling temperature of hot rolling is 890 C. and the hot rolling coiling temperature is 630 C., wherein water quenching cooling is carried out before coiling, and the hot-rolled plate has a thickness of 1.95 mm;

(51) 3) cold-rolling, wherein the overall reduction rate is controlled to 66%, and the cold-rolled plate has a thickness of 0.66 mm;

(52) 4) continuous annealing

(53) performing continuous annealing in a non-oxidation continuous annealing furnace comprising a direct-fired heating section, a radiant tube heating section, a soaking treatment and a cooling treatment. The duration in the direct-fired heating section is 31 s; the heating temperature is 680 C., and the induction heating time is 42 s; the soaking temperature is 835 C., and the soaking time is 3 s; and the cooling temperature is 560 C., and the cooling time is 11 s;

(54) 5) aluminium-zinc-hot-dipping, wherein the hot-dipped aluminium-zinc metal layers on both sides are controlled to a weight of 150 g/m.sup.2, with the components of the dipping layer being, in weight percentage: 51% of Al, 47% of Zn, 1% of Si, 0.02% of Ti, and the balance being impurities; the temperature of the strip steel when entering the zinc pot is controlled at 560 C. and the temperature of an aluminium zinc liquid is controlled at 580 C.; the cooling after hot-dipping is cold-gas jet cooling; a rapid cooling method is used, and the substrate is an uniform complex phase structure of ferrite+cementite+bainite+martensite+some deformed banded grains+fine precipitates;

(55) 6) skin pass rolling, withdrawing-straightening and coiling for use;

(56) 7) optionally Colour-coating, wherein the final product has a thickness of 0.7 mm.

(57) After test detection, the yield strength RP.sub.0.2 is 623 MPa, the tensile strength Rm is 708 MPa, and the elongation after fracture A80 mm is 14.5%.

Example 5

(58) This example relates to a method for manufacturing an aluminium-zinc-hot-dipped and colour-coated steel plate having a 600 MPa yield strength grade and a high elongation, with the steel plate having a thickness of 0.7 mm after being colour-coated, the method comprising the steps of:

(59) 1) smelting: performing molten iron desulphurization, converter smelting and casting to obtain a cast slab having chemical components in weight percentage: 0.13% of C, 0.09% of Si, 1.5% of Mn, 0.004% of N, 0.008% of S, 0.001% of Ti, 0.051% of Nb, and the balance of Fe and other inevitable impurities;

(60) 2) hot-rolling and Pickling

(61) wherein the heating tapping temperature is 1190 C., the finish rolling temperature of hot rolling is 840 C. and the hot rolling coiling temperature is 590 C., wherein water quenching cooling is carried out before coiling, and the hot-rolled plate has a thickness of 2.03 mm;

(62) 3) cold-rolling, wherein the overall reduction rate is controlled to 70%, and the cold-rolled plate has a thickness of 0.61 mm;

(63) 4) continuous annealing

(64) performing continuous annealing in a non-oxidation continuous annealing furnace comprising a direct-fired heating section, a radiant tube heating section, a soaking treatment and a cooling treatment. The duration in the direct-fired heating section is 46 s; the heating temperature is 680 C., and the induction heating time is 48 s; the soaking temperature is 760 C., and the soaking time is 7 s; the cooling temperature is 600 C., and the cooling time is 11 s; the holding temperature is low so that a certain cold-rolled structure retains, strengthening the substrate.

(65) 5) aluminium-zinc-hot-dipping, wherein the hot-dipped aluminium-zinc metal layers on both sides are controlled to a weight of 150 g/m.sup.2, with the components of the dipping layer being, in weight percentage: 52% of Al, 46% of Zn, 1% of Si, 0.03% of Ti, and the balance being impurities; the temperature of the strip steel when entering the zinc pot is controlled at 600 C. and the temperature of an aluminium zinc liquid is controlled at 600 C.; the cooling after hot-dipping is cold-gas jet cooling; a rapid cooling method is used, and the substrate is an uniform complex phase structure of ferrite+cementite+bainite+martensite+some deformed banded grains+fine precipitates;

(66) 6) skin pass rolling, withdrawing-straightening and coiling for use;

(67) 7) optionally colour-coating, wherein the final product has a thickness of 0.65 mm.

(68) After test detection, the yield strength RP.sub.0.2 is 641 MPa, the tensile strength Rm is 685 MPa, and the elongation after fracture A80 mm is 13.2%.

Example 6

(69) This example relates to a method for manufacturing an aluminium-zinc-hot-dipped and colour-coated steel plate having a 600 MPa yield strength grade and a high elongation, with the steel plate having a thickness of 0.7 mm after being colour-coated, the method comprising the steps of:

(70) 1) smelting: performing molten iron desulphurization, converter smelting and casting to obtain a cast slab having chemical components in weight percentage: 0.12% of C, 0.09% of Si, 1.5% of Mn, 0.004% of N, 0.008% of S, 0.04% of Ti, 0.035% of Nb, and the balance of Fe and other inevitable impurities;

(71) 2) hot-rolling and pickling

(72) wherein the heating tapping temperature is 1160 C., the finish rolling temperature of hot rolling is 810 C. and the hot rolling coiling temperature is 510 C., wherein water quenching cooling is carried out before coiling, and the hot-rolled plate has a thickness of 2.35 mm;

(73) 3) cold-rolling, wherein the overall reduction rate is controlled to 72%, and the cold-rolled plate has a thickness of 0.66 mm;

(74) 4) continuous annealing

(75) performing continuous annealing in a non-oxidation continuous annealing furnace comprising a direct-fired heating section, a radiant tube heating section, a soaking treatment and a cooling treatment. The duration in the direct-fired heating section is 31 s; the heating temperature is 680 C., and the induction heating time is 42 s; the soaking temperature is 780 C., and the soaking time is 3 s; and the cooling temperature is 585 C., and the cooling time is 11 s; the holding temperature is low so that a certain cold-rolled structure retains, strengthening the substrate.

(76) 5) aluminium-zinc-hot-dipping, wherein the hot-dipped aluminium-zinc metal layers on both sides are controlled to a weight of 150 g/m.sup.2, with the components of the dipping layer being, in weight percentage: 51% of Al, 47% of Zn, 1% of Si, 0.03% of Ti, and the balance being impurities; the temperature of the strip steel when entering the zinc pot is controlled at 585 C. and the temperature of an aluminium zinc liquid is controlled at 550 C.; the cooling after hot-dipping is cold-gas jet cooling; a rapid cooling method is used, and the substrate is an uniform complex phase structure of ferrite+cementite+bainite+martensite+some deformed banded grains+fine precipitates;

(77) 6) skin pass rolling, withdrawing-straightening and coiling for use;

(78) 7) optionally colour-coating, wherein the final product has a thickness of 0.7 mm.

(79) After test detection, the yield strength RP.sub.0.2 is 611 MPa, the tensile strength Rm is 680 MPa, and the elongation after fracture A80 mm is 14.2%.