Production method of 700MPa-grade high-strength weathering steel

Abstract

The invention discloses a production method of 700MPa-grade high-strength weathering steel. The production method comprises the following steps: smelting and continuous casting production process flow: molten iron pretreatment, converter treatment, LF (ladle furnace) refining and machine casting; the components of the molten steel for the casting machine in percentage by mass are limited; according to the hot rolling production technological process, the casting blank tapping temperature is 1230 + / -20 DEG C, the finish rolling temperature of finish rolling is 890 + / -10 DEG C, the cooling speed is 10-20 DEG C / S, and the thickness of a hot rolled steel strip is 2.5-3.5 mm; laminar cooling equipment is adopted for cooling, a pre-dispersion cooling mode is adopted, and the coiling temperature is 640 + / -10 DEG C. A conventional C, S, i and Mn component system design is adopted, the content of corrosion-resistant alloy elements is properly reduced by adding corrosion-resistant elements Cu, Cr and Ni, the production cost is reduced, and meanwhile good performance is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgical sheet production, and particularly relates to a production method of 700MPa grade high-strength weathering steel. Background Art

[0002] Weathering-resistant steel (i.e., weathering steel) refers to a low-alloy steel with good atmospheric corrosion resistance made by adding a certain amount of alloying elements such as Cu, P, C or Ni, Mo, Nb, Ti, etc. to steel. In industrial and rural atmospheric environments, weathering steel forms a dense and stable oxide protective film on its matrix surface, which hinders the entry of corrosive media and has excellent properties such as anti-atmospheric corrosion. However, the rust layer formed on the surface of ordinary carbon steel matrix is loose and has micro-cracks, and cannot really protect the matrix steel.

[0003] Under the guidance of the national strategies of giving priority to ecology, green development, carbon peak, and carbon neutrality, this type of product has very good market prospects. Summary of the Invention

[0004] The purpose of the present invention is to provide a production method of 700MPa grade high-strength weathering steel, which adopts a conventional C-Si-Mn composition system design, reduces production costs by adding corrosion-resistant elements Cu, Cr, Ni and appropriately reducing the content of corrosion-resistant alloying elements, and has good performance at the same time. This product is mainly used in the production of unpainted photovoltaic brackets.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A production method of 700MPa grade high-strength weathering steel of the present invention includes:

[0007] Smelting - continuous casting production process flow: hot metal pretreatment - converter - LF refining - casting machine; the mass percentage composition of the molten steel supplied to the casting machine is C: 0.06 - 0.08%, Si: 0.20 - 0.30%, Mn: 0.35 - 0.45%, P: ≤0.02%, S: ≤0.01%, Cu: 0.26 - 0.30%, Cr: 2.0 - 2.3%, Ni: 0.05 - 0.07%, Ti: 0.06 - 0.08%, and the rest is Fe and impurities;

[0008] Hot rolling production process flow: slab heating - high-pressure water descaling - sizing press - rolling on E1R1 roughing mill - rolling on E2R2 roughing mill - flying shear - high-pressure water descaling - rolling on F1-F7 finishing mills - intensified laminar cooling - coiling - warehousing - sampling and inspection - weighing and packaging; wherein:

[0009] The tapping temperature of the continuous casting billet is 1230±20℃, the finishing rolling temperature of finish rolling is 890±10℃, the cooling rate is 10-20℃ / S, the thickness of the hot-rolled steel strip is 2.5-3.5mm; laminar cooling equipment is used for cooling, in the front dispersed cooling mode, and the coiling temperature is 640±10℃.

[0010] Furthermore, the composition of the weathering steel by mass percentage is: C: 0.07%, Si: 0.25%, Mn: 0.38%, P: 0.013%, S: 0.004%, Cu: 0.27%, Cr: 2.10%, Ni: 0.06%, Ti: 0.063%, and the rest is Fe and impurities.

[0011] Furthermore, the composition of the weathering steel by mass percentage is: C: 0.07%, Si: 0.23%, Mn: 0.38%, P: 0.012%, S: 0.004%, Cu: 0.28%, Cr: 2.17%, Ni: 0.06%, Ti: 0.063%, and the rest is Fe and impurities.

[0012] Furthermore, the composition of the weathering steel by mass percentage is: C: 0.07%, Si: 0.23%, Mn: 0.39%, P: 0.015%, S: 0.003%, Cu: 0.28%, Cr: 2.04%, Ni: 0.06%, Ti: 0.063%, and the rest is Fe and impurities.

[0013] Furthermore, the hot metal is subjected to desulfurization pretreatment, and top-bottom combined blowing converter smelting is used to dephosphorize and decarburize the hot metal to obtain molten steel. Argon is blown throughout the converter smelting process, and scrap steel is added to the converter. The tapping temperature of the converter is 1620℃; then the molten steel after converter smelting is subjected to LF secondary refining. The refining in-position temperature is ≥1560℃, and temperature measurement and composition fine-tuning are carried out during LF secondary refining; the superheat of slab continuous casting is 25℃, and then slab cleaning, slow cooling, and quality inspection of the continuous casting billet are carried out; the slab heating temperature is 1240℃, the heating time is 43min, and hot tandem rolling mill is used for rolling; the finishing rolling temperature of finish rolling is 890℃, the finished product thickness is 3mm; laminar cooling adopts front dispersed cooling, the cooling rate is 13℃ / S, and the steel strip temperature is reduced to 635℃ for coiling; finally, product performance testing is carried out.

[0014] Further, the hot metal is subjected to desulfurization pretreatment, and top and bottom combined blowing converter smelting is used to dephosphorize and decarburize the hot metal to obtain molten steel. Argon is blown throughout the converter smelting process, and scrap steel is added to the converter. The tapping temperature of the converter is 1620°C. Then, the molten steel after converter smelting is subjected to LF secondary refining. The refining in-position temperature is ≥1560°C, and temperature measurement and composition fine-tuning are carried out during LF secondary refining. The superheat of slab continuous casting is 25°C. After that, slab cleaning, slow cooling, and quality inspection of the continuous casting billet are carried out. The slab heating temperature is 1233°C, and the heating time is 43 minutes. Hot tandem rolling is carried out using a hot tandem mill. The finishing rolling temperature is 888°C, and the finished product thickness is 3 mm. Laminar cooling uses pre-dispersed cooling, and the cooling rate is 14°C / S. The strip temperature is reduced to 643°C for coiling. Finally, product performance testing is carried out.

[0015] Further, the hot metal is subjected to desulfurization pretreatment, and top and bottom combined blowing converter smelting is used to dephosphorize and decarburize the hot metal to obtain molten steel. Argon is blown throughout the converter smelting process, and scrap steel is added to the converter. The tapping temperature of the converter is 1633°C. Then, the molten steel after converter smelting is subjected to LF secondary refining. The refining in-position temperature is ≥1560°C, and temperature measurement and composition fine-tuning are carried out during LF secondary refining. The superheat of slab continuous casting is 20°C. After that, slab cleaning, slow cooling, and quality inspection of the continuous casting billet are carried out. The slab heating temperature is 1240°C, and the heating time is 49 minutes. Hot rolling is carried out using a hot tandem mill. The finishing rolling temperature is 899°C, and the finished product thickness is 3 mm. Laminar cooling uses pre-dispersed cooling, and the cooling rate is 14°C / S. The strip temperature is reduced to 643°C for coiling. Finally, product performance testing is carried out.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0017] The metallographic microstructure of the steel grade of the present invention is ferrite + pearlite + bainite. The 700 MPa grade high-strength weathering steel produced by the method provided by the present invention has been inspected in the laboratory, and all indexes of surface quality and performance meet the relevant technical standard requirements of the manufacturer and meet the relevant use requirements. The mechanical properties and process properties meet the relevant standards and user requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below with reference to the drawings.

[0019] Figure 1 It is the microstructural diagram of Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be described in more detail below through specific embodiments. The embodiments are only descriptions of the best implementation modes of the present invention and do not limit the scope of the present invention in any way.

[0021] Embodiment 1

[0022] The hot metal is subjected to desulfurization pretreatment, and the top-bottom combined blowing converter is used for smelting to remove phosphorus and carbon from the hot metal to obtain molten steel. Argon is blown throughout the converter smelting process, and scrap steel is added to the converter. The tapping temperature of the converter is 1620 °C. Then, the molten steel after converter smelting is subjected to LF secondary refining. The refining in-position temperature is ≥1560 °C. Temperature measurement and composition fine-tuning are carried out during LF secondary refining. The chemical composition of the molten steel supplied to the continuous caster by LF secondary refining is shown in Table 1. The superheat of slab continuous casting is 25 °C. Then, slab cleaning, slow cooling, and quality inspection of the continuous casting billet are carried out. The slab heating temperature is 1240 °C, and the heating time is 43 min. Hot tandem rolling is carried out. The finishing rolling temperature is 890 °C, and the finished product thickness is 3 mm. The laminar flow cooling adopts pre-dispersed cooling, with a cooling rate of 13 °C / S. The strip temperature is reduced to 635 °C for coiling. Finally, product performance testing is carried out.

[0023] Example 2

[0024] The hot metal is subjected to desulfurization pretreatment, and the top-bottom combined blowing converter is used for smelting to remove phosphorus and carbon from the hot metal to obtain molten steel. Argon is blown throughout the converter smelting process, and scrap steel is added to the converter. The tapping temperature of the converter is 1620 °C. Then, the molten steel after converter smelting is subjected to LF secondary refining. The refining in-position temperature is ≥1560 °C. Temperature measurement and composition fine-tuning are carried out during LF secondary refining. The chemical composition of the molten steel supplied to the continuous caster by LF secondary refining is shown in Table 1. The superheat of slab continuous casting is 25 °C. Then, slab cleaning, slow cooling, and quality inspection of the continuous casting billet are carried out. The slab heating temperature is 1233 °C, and the heating time is 43 min. Hot tandem rolling is carried out. The finishing rolling temperature is 888 °C, and the finished product thickness is 3 mm. The laminar flow cooling adopts pre-dispersed cooling, with a cooling rate of 14 °C / S. The strip temperature is reduced to 643 °C for coiling. Finally, product performance testing is carried out.

[0025] Example 3

[0026] The hot metal is subjected to desulfurization pretreatment, and the top-bottom combined blowing converter is used for smelting to remove phosphorus and carbon from the hot metal to obtain molten steel. Argon is blown throughout the converter smelting process, and scrap steel is added to the converter. The tapping temperature of the converter is 1633 °C. Then, the molten steel after converter smelting is subjected to LF secondary refining. The refining in-position temperature is ≥1560 °C. Temperature measurement and composition fine-tuning are carried out during LF secondary refining. The chemical composition of the molten steel supplied to the continuous caster by LF secondary refining is shown in Table 1. The superheat of slab continuous casting is 20 °C. Then, slab cleaning, slow cooling, and quality inspection of the continuous casting billet are carried out. The slab heating temperature is 1240 °C, and the heating time is 49 min. Hot tandem rolling is carried out. The finishing rolling temperature is 899 °C, and the finished product thickness is 3 mm. The laminar flow cooling adopts pre-dispersed cooling, with a cooling rate of 14 °C / S. The strip temperature is reduced to 643 °C for coiling. Finally, product performance testing is carried out.

[0027] Comparative Example 1

[0028] The hot metal is subjected to desulfurization pretreatment. The top and bottom combined blowing converter is used for smelting to remove phosphorus and carbon from the hot metal to obtain molten steel. Argon is blown throughout the converter smelting process. Scrap steel is added to the converter, and the tapping temperature of the converter is 1620 °C. Then, the molten steel after converter smelting is subjected to LF secondary refining. The refining in-position temperature is ≥1560 °C. Temperature measurement and composition fine-tuning are carried out during LF secondary refining. The chemical composition of the molten steel supplied to the continuous casting machine for LF secondary refining is shown in Table 1. The superheat of the slab continuous casting is 25 °C. Then, slab cleaning, slow cooling, and quality inspection of the continuous casting billet are carried out. The slab heating temperature is 1230 °C, and the heating time is 50 min. Hot strip rolling is carried out using a hot tandem mill. The finish rolling temperature of the finishing mill is 890 °C, and the finished product thickness is 3 mm. Laminar cooling adopts pre-dispersed cooling, with a cooling rate of 15 °C / S. The strip temperature is reduced to 650 °C for coiling. Finally, product performance testing is carried out.

[0029] Table 1 Chemical composition (wt%) of Examples 1-3 of the present invention

[0030]

[0031]

[0032] The mechanical properties of the steel coils of Examples 1-3 of the present invention are inspected, and the inspection results are shown in Table 2.

[0033] Table 2 Mechanical properties of the steel coils of Examples 1-3 of the present invention

[0034]

[0035] It can be seen from the data in Table 2 that the mechanical properties and process properties of the 700 MPa grade high-strength weathering steel produced by the method provided by the present invention meet the requirements of the agreement signed with the user, and the corrosion resistance of the steel is effectively improved by adding Cu and Cr.

[0036] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for producing 700MPa grade high-strength weathering steel, characterized in that: include: Smelting-continuous casting production process: molten iron pretreatment-converter-LF refining-casting machine; the composition of the molten steel for the casting machine is C: 0.06-0.08%, Si: 0.20-0.30%, Mn: 0.35-0.45%, P: ≤0.02%, S: ≤0.01%, Cu: 0.26-0.30%, Cr: 2.0-2.3%, Ni: 0.05-0.07%, Ti: 0.06-0.08%, and the rest is Fe and impurities; Hot rolling production process: slab heating - high-pressure water descaling - fixed width press - E1R1 roughing mill rolling - E2R2 roughing mill rolling - flying shear - high-pressure water descaling - F1-F7 finishing mill rolling - encrypted laminar cooling - coiling - storage - sampling, inspection - weighing, packaging; Among them: The temperature of the ingot out of the furnace is 1230±20℃, the final rolling temperature of the finish rolling is 890±10℃, the cooling rate is 10-20℃ / S, the thickness of the hot rolled steel strip is 2.5-3.5mm; the cooling adopts laminar cooling equipment, front dispersed cooling mode, and the coiling temperature is 640±10℃.

2. The method for producing 700MPa grade high strength weathering steel according to claim 1, characterized in that: The components of the weathering steel in mass percentage are C: 0.07%, Si: 0.25%, Mn: 0.38%, P: 0.013%, S: 0.004%, Cu: 0.27%, Cr: 2.10%, Ni: 0.06%, Ti: 0.063%, and the rest are Fe and impurities.

3. The method for producing 700MPa grade high strength weathering steel according to claim 1, characterized in that: The components of the weathering steel in mass percentage are C: 0.07%, Si: 0.23%, Mn: 0.38%, P: 0.012%, S: 0.004%, Cu: 0.28%, Cr: 2.17%, Ni: 0.06%, Ti: 0.063%, and the rest are Fe and impurities.

4. The method for producing 700MPa grade high strength weathering steel according to claim 1, characterized in that: The components of the weathering steel in mass percentage are C: 0.07%, Si: 0.23%, Mn: 0.39%, P: 0.015%, S: 0.003%, Cu: 0.28%, Cr: 2.04%, Ni: 0.06%, Ti: 0.063%, and the rest are Fe and impurities.

5. The method for producing 700MPa grade high strength weathering steel according to claim 2, characterized in that: The molten iron is pre-treated with desulfurization, and top and bottom combined blowing converter is used to dephosphorize and decarbonize the molten iron to obtain molten steel. Argon is blown throughout the converter smelting process, scrap steel is added to the converter, and the converter tapping temperature is 1620℃; the molten steel after converter smelting is then subjected to LF refining outside the furnace, and the refining temperature is ≥1560℃, and the LF refining is performed for temperature measurement and composition fine-tuning; the overheat degree of slab continuous casting is 25℃, followed by slab cleaning, slow cooling, and continuous casting slab quality inspection; the slab heating temperature is 1240℃, the heating time is 43min, and hot rolling mill is used for rolling; the finishing rolling temperature is 890℃, and the finished product thickness is 3mm; laminar cooling adopts front dispersion cooling, the cooling rate is 13℃ / S, and the steel strip temperature is reduced to 635℃ for coiling; finally, product performance testing is carried out.

6. The method for producing 700MPa grade high strength weathering steel according to claim 3, characterized in that: The molten iron is pre-treated with desulfurization, and top and bottom combined blowing converter is used to dephosphorize and decarbonize the molten iron to obtain molten steel. Argon is blown throughout the converter smelting process, scrap steel is added to the converter, and the converter tapping temperature is 1620℃; the molten steel after converter smelting is then subjected to LF refining outside the furnace, and the refining temperature is ≥1560℃, and the LF refining is performed for temperature measurement and composition fine-tuning; the overheat of the slab continuous casting is 25℃, followed by slab cleaning, slow cooling, and continuous casting slab quality inspection; the slab heating temperature is 1233℃, the heating time is 43min, and hot rolling mill is used for rolling; the finishing rolling temperature is 888℃, and the finished product thickness is 3mm; laminar cooling adopts front dispersion cooling, the cooling rate is 14℃ / S, and the steel strip temperature is reduced to 643℃ for coiling; finally, product performance testing is carried out.

7. The method for producing 700MPa grade high strength weathering steel according to claim 4, characterized in that: The molten iron is pre-treated with desulfurization, and the top and bottom combined blowing converter is used to dephosphorize and decarbonize the molten iron to obtain molten steel. Argon is blown throughout the converter smelting process, scrap steel is added to the converter, and the converter tapping temperature is 1633℃; the molten steel after converter smelting is then subjected to LF off-furnace refining, the refining in-situ temperature is ≥1560℃, and the LF off-furnace refining is performed for temperature measurement and composition fine-tuning; the slab continuous casting overheat is 20℃, followed by slab cleaning, slow cooling, and continuous casting slab quality inspection; the slab heating temperature is 1240℃, the heating time is 49min, and the hot rolling mill is used for rolling; the finishing rolling temperature is 899℃, and the finished product thickness is 3mm; laminar cooling adopts front dispersion cooling, the cooling rate is 14℃ / S, and the steel strip temperature is reduced to 643℃ for coiling; finally, the product performance is tested.

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