500 MPA yield strength-graded, high-stretchability hot-dip aluminum-zinc and color-coated steel plate and manufacturing method therefore

Abstract

An aluminium-zinc-hot-dipped and colour-coated steel plate having yield strength of ≥500 MPa 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, N≤0.004%, S≤0.01%, Ti≤0.15%, Nb≤0.050%, and the balance being Fe and other inevitable impurities, and meanwhile satisfying the conditions of: (C+Mn/6)≥0.3%; Mn/S≥150; Nb satisfying 0.01%≤(Nb-0.22C-1.1N)≤0.05% where no Ti is contained; Ti satisfying 0.5≤Ti/C≤1.5 where no Nb is contained; and 0.04%≤(Ti+Nb)≤0.2% where Ti and Nb are added in combination. The steel plate has a tensile strength of ≥550 MPa, an elongation after fracture of ≥15%, a good strength and toughness and an excellent corrosion resistance.

Claims

1. An aluminium-zinc-hot-dipped steel plate having a yield strength of ≥500 MPa and a high elongation, with the chemical components in mass percentage of a substrate of the steel plate consisting of: 0.07-0.15% of C, 0.02-0.5% of Si, 1.3-1.8% of Mn, N≤0.004%, S≤0.01%, Ti≤0.15%, Nb≤0.050%, and the balance being Fe and other inevitable impurities, wherein said chemical components satisfy formulae provided as follows: (C+Mn/6)≥0.3%; Mn/S≥150; 0.01%≤(Nb-0.22C-1.1 N)≤0.05%; 0.5≤Ti/C≤1.5; and 0.04%≤(Ti+Nb)≤0.2%; and wherein the steel plate has a microstructure which is a complex phase structure comprising ferrite, cementite, fine precipitates, bainite, martensite and deformed banded grains.

2. The aluminium-zinc-hot-dipped steel plate of claim 1, wherein said steel plate has a tensile strength of ≥550 MPa and an elongation after fracture of ≥15%.

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

4. The aluminium-zinc-hot-dipped steel plate of claim 3, wherein the spangles has a grain diameter that is less than 10 mm.

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

6. The aluminium-zinc-hot-dipped steel plate of claim 1, wherein the aluminium-zinc-hot-dipped steel plate has a dipping layer with the components in weight percentage 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.

7. A steel plate comprising the aluminium-zinc-hot-dipped steel plate of claim 1 with a coating layer coated on its surface.

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

9. The steel plate of claim 7, wherein the aluminium-zinc-hot-dipped steel plate has a tensile strength of ≥550 MPa and an elongation after fracture of ≥15%.

10. The steel plate of claim 7, wherein the aluminium-zinc-hot-dipped steel plate has fine, uniform silver-white spangles on its surface.

11. The steel plate of claim 7, wherein the spangles have a grain diameter that is less than 10 mm.

12. The steel plate of claim 7, wherein the aluminium-zinc-hot-dipped steel plate has a dipping layer with the components in weight percentage 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.

13. A method for producing the aluminium-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 the cast slab; 2) hot-rolling and pickling the casting 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 a cooling method after the hot rolling, which method is water cooling; 3) cold-rolling to form a steel strip with a rolling reduction of 70-80%; 4) continuous annealing in a non-oxidation continuous annealing aluminium-zinc-hot-dipping furnace comprising a direct-fired heating section, a radiant tube heating section, a soaking section, a pre-hot-dipping cooling section, a hot tension roller zone and a hot-dipping section, and post-hot-dipping cooling, 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 the post-hot-dipping cooling section is 8-15 s; the duration in the hot tension roller zone and the hot-dipping section is 8-12 s; and the post-hot-dipping cooling 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 aluminium-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 temper rolling ratio being 0.25%±0.2 and a withdrawing-straightening ratio being 0.2%±0.2.

14. The method of claim 13, further comprising step 7: coating with a coating layer selected from the group consisting of a fluorocarbon, a polyester, a silicon-modified polyester, a highly weather resistant polyester, and a polyvinylidene fluoride.

15. The method of claim 14, wherein, after being coated, the coating surface does not have the defects of bubbles, cracks and holidays.

16. The method of claim 13, wherein cold gas jet cooling or gas-mist jet cooling is used for the post-hot-dipping cooling in step 4).

17. The method of claim 13, wherein said steel plate has a tensile strength of ≥550 MPa and an elongation after fracture of ≥15%.

18. The method of claim 13, the aluminium-zinc-hot-dipped steel plate has fine, uniform silver-white spangles on its surface.

19. The method of claim 18, wherein the spangles has a grain diameter that is less than 10 mm.

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.

DETAILED DESCRIPTION OF EMBODIMENTS

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

(4) 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. The components above are subjected to molten iron desulphurization, converter smelting and casting to obtain a cast slab; subsequently, the cast slab is hot-rolled and cold-rolled, and subjected to continuous annealing, hot-dipping, skin pass rolling and withdrawing-straightening to finally obtain an aluminium-zinc-hot-dipped plate; optionally, the aluminium-zinc-hot-dipped plate is further colour-coated to obtain a colour-coated steel plate.

(5) For the specific process conditions of the examples of the present invention, reference can be made to tables 2 and 3. Table 3 relates to the continuous annealing process conditions of the examples of the present invention. Table 4 relates to the mechanical properties of the steel plates of the examples of the present invention.

(6) 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 1.3 0.0015 0.008 0.001 0.045 48 50 1.1 0.01 Example 2 0.12 0.075 1.5 0.0015 0.008 0.001 0.045 49 49 1.1 0.02 Example 3 0.08 0.092 1.7 0.0018 0.006 0.006 0.045 52 45 2 0.05 Example 4 0.13 0.045 1.4 0.0018 0.006 0.140 0.001 52 45 2 0.05 Example 5 0.09 0.050 1.6 0.0018 0.006 0.001 0.042 53 44 2 0.05 Example 6 0.11 0.120 1.6 0.0018 0.006 0.031 0.030 53 44 2 0.03

(7) 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 1230 860 550 80 Example 3 1200 880 630 71 Example 4 1170 810 510 76 Example 5 1250 890 640 80 Example 6 1250 860 620 80

(8) TABLE-US-00003 TABLE 3 Temperature Temperature in direct- Duration in radiant Duration Holding Post- fired in direct- heating in radiant temper- hot-dipping section/ fired section/ heating ature/ Holding cooling rate/ ° C. section/s ° C. section/s ° C. times/s ° C./s Example 1 680 28 790 38 790 3 30 Example 2 680 28 785 38 785 4 25 Example 3 690 31 835 42 835 4 31 Example 4 680 28 785 38 785 4 31 Example 5 680 44 755 43 755 8 31 Example 6 680 28 790 38 790 4 31

(9) TABLE-US-00004 TABLE 4 Yield Tensile strength/ strength/ Elongation/ Thickness/ MPa MPa % mm Example 1 543 586 17 0.5 Example 2 537 571 15.5 0.45 Example 3 534 591 15.8 0.6 Example 4 524 581 16.1 0.6 Example 5 511 572 16.8 0.5 Example 6 513 578 15.6 0.5

Example 1

(10) This example relates to a method for producing an aluminium-zinc-hot-dipped and colour-coated steel plate having a 500 MPa yield strength grade and a high elongation, with the steel plate having a thickness of 0.5 mm after being colour-coated, the method comprising the steps of:

(11) 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, 1.3% of Mn, S≤0.01%, N≤0.004%, Ti≤0.001%, 0.045% of Nb, and the balance being Fe and other inevitable impurities.

(12) 2) hot-rolling and pickling

(13) 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. Water quenching cooling is carried out before coiling, and the hot-rolled plate has a thickness of 2.3 mm;

(14) 3) cold-rolling, wherein the overall reduction rate is controlled to 80%, and the cold-rolled plate has a thickness of 0.46 mm;

(15) 4) continuous annealing performing continuous annealing in a non-oxidation continuous annealing furnace comprising a direct-fired heating section, a radiant tube heating section, a radiant tube soaking treatment and a cooling treatment. wherein the duration in the direct-fired heating section is 28 s; the heating temperature is 680° C., and the radiant tube heating time is 38 s; the soaking temperature is 790° C., and the soaking time is 3 s; and the cooling temperature is 600° C., and the cooling time is 11 s;

(16) 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: 489% of Al, 50% of Zn, 1.1% 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 600° C.; the post-hot-dipping cooling method is gas-mist jet cooling; and

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

(18) 7) optionally, colour-coating. The final product has a thickness of 0.5 mm.

(19) After test detection, the yield strength RP.sub.0.2 of the steel plate of this example is 543 MPa, the tensile strength Rm is 586 MPa, and the elongation after fracture A.sub.80 mm is 17%.

(20) The substrate of this example is a uniform complex phase structure of ferrite+cementite+bainite+martensite+deformed banded grains+fine precipitates (see FIG. 1).

Example 2

(21) This example relates to a method for producing an aluminium-zinc-hot-dipped and colour-coated steel plate having a 500 MPa yield strength grade and a high elongation, with the steel plate having a thickness of 0.45 mm after being colour-coated, the method comprising the steps of:

(22) 1) smelting: performing molten iron desulphurization, converter smelting and casting to obtain a cast slab having chemical components in weight percentage: 0.11% of C, 0.075% of Si, 1.5% of Mn, S≤0.01%, N≤0.004%, Ti≤0.001%, 0.045% of Nb, and the balance being Fe and other inevitable impurities;

(23) 2) hot-rolling and pickling

(24) 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. Water quenching cooling is carried out before coiling; and the hot-rolled plate has a thickness of 2.1 mm;

(25) 3) cold-rolling, wherein the overall reduction rate is controlled to 80%, and the cold-rolled plate has a thickness of 0.41 mm;

(26) 4) continuous annealing wherein continuous annealing is performed in a non-oxidation continuous annealing furnace comprising a direct-fired heating section, a radiant tube heating section, a radiant tube soaking treatment and a cooling treatment, the duration in the direct-fired heating section is 28 s; the heating temperature is 680° C., and the induction heating time is 38 s; the soaking temperature is 785° C., and the soaking time is 4 s; and the cooling temperature is 600° C., and the cooling time is 11 s;

(27) 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: 49% of Al, 49% of Zn, 1.1% of Si and 0.02% 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 590° C.; the post-hot-dipping cooling method is gas-mist jet cooling; and

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

(29) 7) optionally, colour-coating. The final product has a thickness of 0.45 mm.

(30) After test detection, the yield strength RP.sub.0.2 of the steel plate of this example is 537 MPa, the tensile strength Rm is 571 MPa, and the elongation after fracture A.sub.80 mm is 15.5%.

(31) The substrate of this example is a uniform complex phase structure of ferrite+cementite+bainite+martensite+deformed banded grains+fine precipitates (see FIG. 2).

Example 3

(32) This example relates to a method for producing an aluminium-zinc-hot-dipped and colour-coated steel plate having a 500 MPa yield strength grade and a high elongation, with the steel plate having a thickness of 0.5 mm after being colour-coated, the method comprising the steps of:

(33) 1) smelting: wherein molten iron desulphurization, converter smelting and casting are performed to obtain a cast slab having chemical components in weight percentage: 0.08% of C, 0.092% of Si, 1.7% of Mn, S≤0.01%, N≤0.004%, 0.006% of Ti, 0.045% of Nb, and the balance being Fe and other inevitable impurities.

(34) 2) hot-rolling and pickling

(35) wherein the heating tapping temperature is 1200° C., the finish rolling temperature of hot rolling is 880° C. and the hot rolling coiling temperature is 630° C. Water quenching cooling is carried out before coiling; and the hot-rolled plate has a thickness of 1.93 mm;

(36) 3) cold-rolling, wherein the overall reduction rate is controlled to 71%, and the cold-rolled plate has a thickness of 0.56 mm;

(37) 4) continuous annealing wherein continuous annealing is performed in a non-oxidation continuous annealing furnace comprising a direct-fired heating section, a radiant tube heating section, a radiant tube soaking treatment and a cooling treatment, the duration in the direct-fired heating section is 31 s; the heating temperature is 690° C., and the radiant tube heating time is 42 s; the soaking temperature is 835° C., and the soaking time is 4 s; and the cooling temperature is 600° C., and the cooling time is 11 s;

(38) 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, 45% of Zn, 2% of Si, 0.05% 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 560° C.; the post-hot-dipping cooling method is gas-mist jet cooling; and

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

(40) 7) optionally, colour-coating. The final product has a thickness of 0.6 mm.

(41) After test detection, the yield strength RP.sub.0.2 of the steel plate of this example is 534 MPa, the tensile strength Rm is 591 MPa, and the elongation after fracture A.sub.80 mm is 15.8%.

(42) The substrate of this example is a uniform complex phase structure of ferrite+cementite+bainite+martensite+deformed banded grains+fine precipitates.

Example 4

(43) This example relates to a method for producing an aluminium-zinc-hot-dipped and colour-coated steel plate having a 500 MPa yield strength grade and a high elongation, with the steel plate having a thickness of 0.45 mm after being colour-coated, the method comprising the steps of:

(44) 1) smelting: wherein molten iron desulphurization, converter smelting and casting are performed to obtain a cast slab having chemical components in weight percentage: 0.13% of C, 0.045% of Si, 1.4% of Mn, S≤0.01%, N≤0.004%, 0.14% of Ti, 0.001% of Nb, and the balance being Fe and other inevitable impurities;

(45) 2) hot-rolling and pickling

(46) wherein the heating tapping temperature is 1170° C., the finish rolling temperature of hot rolling is 810° C. and the hot rolling coiling temperature is 510° C. Water quenching cooling is carried out before coiling; and the hot-rolled plate has a thickness of 2.3 mm;

(47) 3) cold-rolling, wherein the overall reduction rate is controlled to 76%, and the cold-rolled plate has a thickness of 0.56 mm;

(48) 4) continuous annealing wherein continuous annealing is performed in a non-oxidation continuous annealing furnace comprising a direct-fired heating section, a radiant tube heating section, a radiant tube 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 38 s; the soaking temperature is 785° C., and the soaking time is 4 s; and the cooling temperature is 600° C., and the cooling time is 11 s;

(49) 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, 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 605° C.; the post-hot-dipping cooling method is gas-mist jet cooling; and

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

(51) 7) optionally, colour-coating. The final product has a thickness of 0.6 mm.

(52) After test detection, the yield strength RP.sub.0.2 of the steel plate of this example is 524 MPa, the tensile strength Rm is 581 MPa, and the elongation after fracture A.sub.80 mm is 16.1%.

(53) The substrate of this example is a uniform complex phase structure of ferrite+cementite+bainite+martensite+deformed banded grains+fine precipitates.

Example 5

(54) This example relates to a method for producing an aluminium-zinc-hot-dipped and colour-coated steel plate having a 500 MPa yield strength grade and a high elongation, with the steel plate having a thickness of 0.5 mm after being colour-coated, the method comprising the steps of:

(55) 1) smelting: wherein molten iron desulphurization, converter smelting and casting are performed to obtain a cast slab having chemical components in weight percentage: 0.09% of C, 0.05% of Si, 1.6% of Mn, S≤0.01%, N≤0.004%, 0.001% of Ti, 0.042% of Nb, and the balance being Fe and other inevitable impurities.

(56) 2) hot-rolling and pickling

(57) wherein the heating tapping temperature is 1250° C., the finish rolling temperature of hot rolling is 890° C. and the hot rolling coiling temperature is 640° C. Water quenching cooling is carried out before coiling; and the hot-rolled plate has a thickness of 2.3 mm;

(58) 3) cold-rolling, wherein the overall reduction rate is controlled to 80%, and the cold-rolled plate has a thickness of 0.46 mm;

(59) 4) continuous annealing wherein continuous annealing is performed in a non-oxidation continuous annealing furnace comprising a direct-fired heating section, a radiant tube heating section, a radiant tube soaking treatment and a cooling treatment, the duration in the direct-fired heating section is 44 s; the heating temperature is 680° C., and the radiant tube heating time is 43 s; the soaking temperature is 755° C., and the soaking time is 8 s; and the cooling temperature is 600° C., and the cooling time is 11 s;

(60) 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: 53% of Al, 44% of Zn, 2% of Si, 0.05% 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 post-hot-dipping cooling method is gas-mist jet cooling; and

(61) 6) skin pass rolling, withdrawing-straightening and coiling, and Packaging procedure for use; and

(62) 7) optionally, colour-coating. The final product has a thickness of 0.5 mm.

(63) After test detection, the yield strength RP.sub.0.2 of the steel plate of this example is 511 MPa, the tensile strength Rm is 572 MPa, and the elongation after fracture A.sub.80 mm is 16.8%.

(64) The substrate of this example is a uniform complex phase structure of ferrite+cementite+bainite+martensite+deformed banded grains+fine precipitates.

Example 6

(65) This example relates to a method for producing an aluminium-zinc-hot-dipped and colour-coated steel plate having a 500 MPa yield strength grade and a high elongation, with the steel plate having a thickness of 0.45 mm after being colour-coated, the method comprising the steps of:

(66) 1) smelting: wherein molten iron desulphurization, converter smelting and casting are performed to obtain a cast slab having chemical components in weight percentage: 0.11% of C, 0.12% of Si, 1.6% of Mn, S≤0.01%, N≤0.004%, 0.031% of Ti, 0.030% of Nb, and the balance being Fe and other inevitable impurities;

(67) 2) hot-rolling and pickling

(68) wherein the heating tapping temperature is 1250° C., the finish rolling temperature of hot rolling is 860° C. and the hot rolling coiling temperature is 620° C. Water quenching cooling is carried out before coiling; and the hot-rolled plate has a thickness of 2.3 mm;

(69) 3) cold-rolling, wherein the overall reduction rate is controlled to 80%, and the cold-rolled plate has a thickness of 0.46 mm;

(70) 4) continuous annealing wherein continuous annealing is performed in a non-oxidation continuous annealing furnace comprising a direct-fired heating section, a radiant tube heating section, a radiant tube soaking treatment and a cooling treatment, the duration in the direct-fired heating section is 28 s; the heating temperature is 680° C., and the induction heating time is 38 s; the soaking temperature is 790° C., and the soaking time is 4 s; and the cooling temperature is 600° C., and the cooling time is 11 s;

(71) 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: 53% of Al, 44% 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 560° C.; the post-hot-dipping cooling method is gas-mist jet cooling; and

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

(73) 7) optionally, colour-coating. The final product has a thickness of 0.5 mm.

(74) After test detection, the yield strength RP.sub.0.2 of the steel plate of this example is 513 MPa, the tensile strength Rm is 578 MPa, and the elongation after fracture A.sub.80 mm is 15.6%.

(75) The substrate of this example is a uniform complex phase structure of ferrite+cementite+bainite+martensite+deformed banded grains+fine precipitates.