Rolling method for fine-grain steel plate of large-thickness steel ingot finished product

Abstract

The invention discloses a rolling method of a fine grain steel plate of a large-thickness steel ingot finished product. The steel plate is composed of the following chemical components in percentage by mass: 0.11%-0.13% of C, less than or equal to 0.35% of Si, 1.35%-1.55% of Mn, less than or equal to 0.010% of P, less than or equal to 0.003% of S, 0.020%-0.05% of Alt, 0.015%-0.02% of Nb, 0.25%-0.30% of Ni and the balance of Fe and inevitable impurities. The production method comprises controlled rolling. According to the method, the rolling reduction is increased by adjusting the torque coefficient of a rolling mill, the temperature of an intermediate billet is reduced through intermediate cooling, the rolling rhythm is improved, the self-tempering temperature after rolling ranges from 600 DEG C to 680 DEG C, grains can be refined to 8-10 grades, the large-thickness steel plate with the thickness of 230 mm can be produced through the method, and the center toughness of the steel plate at the temperature of 45 DEG C below zero is good.

Description

Technical Field

[0001] The invention belongs to the field of steel plate rolling, and in particular relates to a method for rolling fine-grained steel plates made from thick steel ingots. Background Art

[0002] With the development of industrial technology, the demand for steel plate thickness specifications is increasing, and the performance requirements of thicker plates are becoming increasingly difficult to meet. Design temperatures are generally below -40°C, and the impact temperature requirements are even lower. There is market demand for this type of steel, with a maximum thickness of 230mm. Currently, there are few steels on the market that meet this thickness and have good toughness at -45°C. Summary of the Invention

[0003] The object of the present invention is to provide a method for rolling fine-grained steel plates with a maximum thickness of 230 mm and good toughness at the center of the steel plate at -45°C into thick steel ingots.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for rolling fine-grained steel plates from thick ingots. The steel plates have the following chemical composition by weight: C: 0.11% to 0.13%, Si: ≤0.35%, Mn: 1.35% to 1.55%, P ≤0.010%, S ≤0.003%, Alt: 0.020% to 0.05%, Nb: 0.015% to 0.02%, Ni: 0.25% to 0.30%, with the balance being Fe and unavoidable impurities. This composition has the advantage of developing a composition design that reduces the amount of precious nickel alloy, reducing alloy cost and improving the purity of the thick plate.

[0005] Preferably, the maximum thickness of the steel plate is 230 mm.

[0006] Preferably, the mechanical properties at room temperature are: yield strength ≥ 355MPa, tensile strength ≥ 500MPa, -45℃ impact average ≥ 100J, at 400℃, R p0.2 ≥290MPa.

[0007] Preferably, it includes the steps of heating the steel billet, rolling and returning to the red; Billet heating process: The maximum billet heating temperature is 1250℃, the soaking temperature is 1220~1240℃, and the heating time is ≥12min / cm to ensure that the billet is evenly burned through.

[0008] The key production process of the steel plate of the present invention is controlled rolling.

[0009] Preferably, the rolling process employs a two-stage rolling process. Stage I begins at a rolling temperature of 1100-1130°C. After the completion of stage I, the intermediate cooling equipment in the roughing and finishing mills rapidly cools the intermediate billet back to 870-900°C. Stage II begins at 840-860°C, and the final rolling temperature is 800-830°C. The mill torque parameters are adjusted to ensure a maximum pass reduction of 40mm or greater. This promotes uniform precipitation of carbides within the grains, providing more nucleation sites for subsequent heat treatment. This further refines and uniformizes the grains, improving strength and low-temperature toughness.

[0010] Preferably, the surface temperature drop of the steel slab is increased between roughing and finishing rolling, further enhancing deformation penetration during finishing rolling. The post-rolling red-hot process: The red-hot temperature of the steel plate after finishing rolling is 600-680°C. Adjusting the red-hot temperature of the steel plate between roughing and finishing rolling lowers the temperature of the parent slab. This, combined with the finishing rolling process, further enhances rolling deformation and dynamic recrystallization in the core, further refining the core grains.

[0011] Preferably, the steel plate produced by the method has a grain size of 8 to 10.

[0012] The beneficial effects of adopting the above technical solution are: The method of the present invention achieves excellent -45°C impact toughness indicators for steel plates based on relatively low-precious alloys, with excellent -45°C center toughness, simply by controlling the rolling process. Intermediate cooling is used during the rolling process to lower the intermediate billet temperature, combined with two-stage high-reduction rolling. This not only improves the rolling rhythm but also increases deformation penetration in thick plates, ensuring that core grains are fully squeezed, deformed, and crushed.

[0013] The method of the present invention is suitable for the production of 230mm thick steel plates requiring low-temperature toughness; Reducing the Ni content of precious alloys significantly reduces alloy costs and production costs; By controlling rolling, the grain size of the steel plate can be significantly improved and the impact toughness can be improved (-45℃, transverse impact energy ≥100J); Low cost and good benefits; The steel plate obtained by the present invention fully meets the standards and safety requirements, and is used in the petroleum, chemical, power station, boiler and other industries for making reactors, heat exchangers, separators, spherical tanks and other equipment and components. DETAILED DESCRIPTION

[0014] The present invention will be further described in detail below with reference to specific embodiments. Example 1

[0015] The chemical composition (by weight percentage) of a fine-grained steel plate made from a thick steel ingot is C: 0.11%, Si: 0.27%, Mn: 1.45%, P: 0.008%, S: 0.0014%, Alt: 0.026%, Nb: 0.015%, Ni: 0.30%, and the remainder is Fe and inevitable impurity elements.

[0016] The thickness of the steel plate is 200 mm.

[0017] A two-stage rolling process is adopted: the starting rolling temperature in stage I is 1100℃, and the intermediate cooling equipment is used to water and return the steel to 900℃; the starting rolling temperature in stage II is 840℃, the final rolling temperature is 800℃, the maximum pass reduction is 40mm, and the return temperature is 660℃.

[0018] The steel plate produced by this method has a grain size of 10 and mechanical properties at room temperature: R eH is 380MPa, R m 526MPa, tensile elongation 25.5%, -45℃ low temperature impact toughness value: 121J, 156J, 136J, 400℃ high temperature tensile mechanical properties of steel plate: R p0.2 It is 300MPa. Example 2

[0019] The chemical composition (by weight percentage) of a fine-grained steel plate made from a thick steel ingot is C: 0.11%, Si: 0.25%, Mn: 1.40%, P: 0.009%, S: 0.001%, Alt: 0.032%, Nb: 0.018%, Ni: 0.28%, and the remainder is Fe and inevitable impurity elements.

[0020] The thickness of the steel plate is 210 mm.

[0021] A two-stage rolling process is adopted: the starting rolling temperature of stage I is 1120℃. After the completion of stage I rolling, the intermediate cooling equipment is used to water and return the steel to 890℃. The starting rolling temperature of stage II is 850℃, the final rolling temperature is 800℃, the maximum pass reduction is 40mm, and the return temperature is 660℃.

[0022] The steel plate produced by this method has a matrix structure of pearlite plus ferrite, a uniform and refined internal structure and a grain size of 10. The mechanical properties of the steel plate at room temperature are: R eH is 398MPa, R m 539MPa, tensile elongation 27.4%, -45℃ low temperature impact toughness value: 155J, 89.6J, 135J, 400℃ high temperature tensile mechanical properties of steel plate: R p0.2 302MPa. Example 3

[0023] The chemical composition (by weight percentage) of a fine-grained steel plate made from a thick steel ingot is C: 0.13%, Si: 0.35%, Mn: 1.35%, P: 0.009%, S: 0.002%, Alt: 0.043%, Nb: 0.015%, Ni: 0.28%, and the remainder is Fe and inevitable impurity elements.

[0024] The thickness of the steel plate is 210 mm.

[0025] A two-stage rolling process is adopted: the starting rolling temperature of stage I is 1130℃. After the completion of stage I rolling, the intermediate cooling equipment is used to water and return the temperature to 900℃. The starting rolling temperature of stage II is 843℃, the final rolling temperature is 827℃, the maximum pass reduction is 45mm, and the red-returning temperature is 680℃.

[0026] The steel plate produced by this method has a matrix structure of pearlite plus ferrite, a uniform and refined internal structure, and a grain size of 9.5. The mechanical properties of the steel plate at room temperature are: R eH is 407MPa, R m The tensile strength is 554MPa, the tensile elongation is 26.2%, the low temperature impact toughness value at -45℃ is 81.4J, 111J, 170J, and the high temperature tensile mechanical properties of the steel plate at 400℃ are: R p0.2 312MPa. Example 4

[0027] The chemical composition (by weight percentage) of a fine-grained steel plate made from a thick steel ingot is C: 0.12%, Si: 0.30%, Mn: 1.45%, P: 0.008%, S: 0.002%, Alt: 0.025%, Nb: 0.020%, Ni: 0.30%, and the remainder is Fe and inevitable impurity elements.

[0028] The thickness of the steel plate is 210 mm.

[0029] A two-stage rolling process is adopted: the starting rolling temperature of stage I is 1125℃. After the completion of stage I rolling, the intermediate cooling equipment is used to water and return the temperature to 880℃. The starting rolling temperature of stage II is 860℃, the final rolling temperature is 830℃, the maximum pass reduction is 45mm, and the returning temperature is 610℃.

[0030] The steel plate produced by this method has a matrix structure of pearlite plus ferrite, a uniform and refined internal structure, and a grain size of 8.5. The mechanical properties of the steel plate at room temperature are: R eH is 467MPa, R m The tensile strength is 578MPa, the tensile elongation is 27.4%, the low temperature impact toughness value of -45℃ is 122J, 137J, 159J, and the high temperature tensile mechanical properties of the steel plate at 400℃ are: R p0.2330MPa. Example 5

[0031] The chemical composition (by weight percentage) of a fine-grained steel plate made from a thick steel ingot is C: 0.11%, Si: 0.35%, Mn: 1.55%, P: 0.010%, S: 0.003%, Alt: 0.045%, Nb: 0.020%, Ni: 0.30%, and the remainder is Fe and inevitable impurity elements.

[0032] The thickness of the steel plate is 230 mm.

[0033] A two-stage rolling process is adopted: the starting rolling temperature of stage I is 1130℃. After the completion of stage I rolling, the intermediate cooling equipment is used to water and return the steel to 870℃. The starting rolling temperature of stage II is 840℃, the final rolling temperature is 800℃, the maximum pass reduction is 50mm, and the returning temperature is 600℃.

[0034] The steel plate produced by this method has a matrix structure of pearlite plus ferrite, a uniform and refined internal structure and a grain size of 9. The mechanical properties of the steel plate at room temperature are: R eH is 407MPa, R m The tensile strength is 542MPa, the tensile elongation is 31.6%, the low temperature impact toughness value of -45℃ is 102J, 124J, 95J, and the high temperature tensile mechanical properties of the steel plate at 400℃ are: R p0.2 305MPa.

[0035] Although some preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0036] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications of the present invention fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for rolling fine-grained steel plates from thick steel ingots, characterized in that: The steel plate is composed of the following chemical components in percentage by mass: C: 0.11% to 0.13%, Si: ≤0.35%, Mn: 1.35% to 1.55%, P≤0.010%, S≤0.003%, Alt: 0.020% to 0.05%, Nb: 0.015% to 0.02%, Ni: 0.25% to 0.30%, and the balance is Fe and unavoidable impurities.

2. The method for rolling fine-grained steel plates from thick steel ingots according to claim 1, characterized in that: The maximum thickness of the steel plate is 230 mm.

3. The method for rolling fine-grained steel plates from thick steel ingots according to claim 1, characterized in that: Mechanical properties at room temperature: yield strength ≥355MPa, tensile strength ≥500MPa, -45℃ impact average ≥100J, at 400℃, R p0.2 ≥290MPa.

4. A method for rolling fine-grained steel plates from thick steel ingots according to claims 1 to 3, characterized in that: Including billet heating, rolling and red-hot process; Billet heating process: The maximum billet heating temperature is 1250℃, the soaking temperature is 1220~1240℃, and the heating time is ≥12min / cm.

5. The method for rolling fine-grained steel plates from thick steel ingots according to claim 4, characterized in that: The rolling process adopts a two-stage rolling process, wherein the starting rolling temperature of stage I is 1100-1130°C. After the completion of rolling I, the intermediate cooling equipment of the rough rolling and finishing rolling mills is used to quickly cool the intermediate billet back to 870-900°C. The starting rolling temperature of stage II is 840-860°C, and the finishing rolling temperature is 800-830°C. The rolling mill torque parameters are adjusted so that the maximum pass reduction is ≥40mm.

6. The method for rolling fine-grained steel plates from thick steel ingots according to claim 4, characterized in that: Post-rolling reddening process: The reddening temperature of the steel plate after finish rolling is 600~680℃.

7. The method for rolling fine-grained steel plates from thick steel ingots according to claim 4, characterized in that: The steel plate produced by the method has a grain size of 8 to 10 levels.