Production method of low-cost cold-rolled low-alloy high-strength steel

Abstract

The invention relates to a low-cost cold-rolled low-alloy high-strength steel production method which comprises the following process steps: S1, hot coiling: adopting the process flows of molten iron pretreatment, 150t top-bottom combined blown converter, LF furnace and continuous casting to produce a qualified plate blank; s2, acid rolling is conducted, oxide scales on the hot-rolled surface are removed through a reasonable acid pickling technology, sufficient deformation distortion energy during annealing is provided through a proper acid rolling reduction rate, and power is provided for sufficient recrystallization; s3, continuous annealing and galvanization: strictly checking the surface reflectivity before annealing and annealing, ensuring the surface cleanliness, ensuring the surface quality of a final product, heating the cold hard coil to be above the recrystallization temperature through a continuous annealing furnace, ensuring the mechanical property of the final product, completing the annealing and cooling processes through the continuous annealing furnace for continuous annealing and galvanization, and performing continuous annealing and galvanization through an oiling machine. And uniformly coating the surface of the steel plate with anti-rust oil, and generating a final finished product through a coiling machine. The comprehensive tensile property and the surface quality of the cold-rolled low-alloy high-strength steel are guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of cold rolling, and in particular relates to a method for producing low-cost cold-rolled low-alloy high-strength steel. Background Art

[0002] ‌Cold-rolled low-alloy high-strength steel is mainly suitable for automotive panels, structural parts, and supporting parts. Compared with other cold-rolled automotive plates, cold-rolled low-alloy high-strength steel has strict requirements on surface quality and plate shape. Due to its complex processing deformation, it also has strict requirements on processing performance. The following technical problems will arise during the research and development and production process of cold-rolled low-alloy high-strength steel: unreasonable composition design, high cost, continuous annealing and galvanizing production lines generally cannot share the same composition system, hot rolling and annealing processes are not suitable, performance qualification rate is low, there are many types of steel, and the slab re-judgment rate is too high. Summary of the invention

[0003] In view of this, the object of the present invention is to provide a low-cost cold-rolled low-alloy high-strength steel production method to solve the above problems.

[0004] To achieve the above object, the technical solution adopted by the present invention is: a low-cost cold-rolled low-alloy high-strength steel production method, comprising the following process steps: S1, hot coil, adopts the process of hot metal pretreatment, 150t top and bottom double blowing converter, LF furnace, continuous casting to produce slabs of qualified quality; S2, pickling, through a reasonable pickling process, remove the hot-rolled surface oxide scale, through the appropriate pickling reduction rate, provide sufficient deformation energy during annealing, and provide power for sufficient recrystallization; S3, continuous annealing and galvanizing, strictly check the surface reflectivity before entering the annealing furnace to ensure surface cleanliness and surface quality of the final product, heat the cold hard coil to above the recrystallization temperature through the continuous annealing furnace to ensure the mechanical properties of the final product, complete the annealing and cooling process through the continuous annealing furnace for continuous annealing and galvanizing, evenly apply anti-rust oil to the surface of the steel plate through the oiler, and generate the final product through the coiler.

[0005] Preferably, in S1, reasonable components are designed, and the specific components are as follows: 340MPa grade: C: 0.07%-0.10%, Si: 0.10%-0.20%, Mn: 0.35%-0.50%, P≤0.025%, S≤0.020%, Alt: 0.020%-0.060%, Ti0.040-0.060%, the rest is Fe and unavoidable impurities; 380MPa grade: C: 0.07%-0.10%, Si: 0.10%-0.20%, Mn: 0.75%-0.90%, P≤0.025%, S≤0.020%, Alt: 0.020%-0.060%, Nb 0.007-0.020%, Ti0.050-0.065%, the rest is Fe and unavoidable impurities; 420MPa grade: C: 0.07%-0.10%, Si: 0.10%-0.20%, Mn: 0.75%-0.90%, P≤0.025%, S≤0.020%, Alt: 0.020%-0.060%, Ti0.060-0.075%, the rest is Fe and unavoidable impurities; Continuous annealing and galvanizing of 340MPa strength grade, 380MPa strength grade and 420MPa strength grade can be industrially produced with the same component system. The hot rolling adopts a low-temperature heating process of 1240-1300℃, the final rolling temperature adopts a high-temperature heating process of 850-890℃, and the hot rolling coiling adopts a coiling temperature process of 580-680℃, thereby ensuring the performance of the final annealed product.

[0006] Preferably, in S2, a suitable pickling process is adopted to ensure the surface cleanliness of the cold-hardened product. The specific pickling process is as follows: the tensile elongation is 0.6-0.8%, the pickling speed is 100-150 mpm, the pickling temperature is 80-90°C, and a large cold rolling deformation rate (55-80%) is used to provide high strain distortion energy for annealing recrystallization.

[0007] Preferably, in S2, a suitable emulsion is used and a suitable concentration is adopted to ensure the surface cleanliness of the cold-hardened product. The specific emulsion process is as follows: the emulsion concentration is 1.5-3.5%, and the cold-hardened coil surface reflectivity is 70-80%.

[0008] Preferably, in S3, a suitable annealing process is adopted, with a heating temperature of 740-800°C, a soaking temperature of 740-800°C, a continuous annealing line production speed of 100-210mpm, a galvanizing line production speed of 60-100mpm, and a smoothing or flattening elongation of 0.8-1.6%, to ensure sufficient recrystallization and final tensile properties of the finished product.

[0009] Preferably, in S3, an electrospark texturing leveling roller is used, the surface roughness of the leveling roller is 2.5-3.5 μm, and the actual surface roughness of the finished product is 0.8-1.6 μm, ensuring that enough anti-rust oil is stored, which is conducive to good processing performance.

[0010] The beneficial effects of the present invention are as follows: by designing reasonable composition and hot rolling and cold rolling processes and by using a suitable surface quality control method, the comprehensive tensile properties and surface quality of the cold-rolled low-alloy high-strength steel are guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is the metallographic diagram after annealing of the present invention (F+a small amount of P, grain size 8.5-9.0). DETAILED DESCRIPTION

[0012] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments: like Figure 1 As shown, a low-cost cold-rolled low-alloy high-strength steel production method includes the following process steps: S1, hot coil, adopts the process of hot metal pretreatment, 150t top and bottom double blowing converter, LF furnace, continuous casting to produce slabs with qualified quality; the composition is reasonably designed, and the specific composition is as follows: 340MPa strength grade: C: 0.07%-0.10%, Si: 0.10%-0.20%, Mn: 0.35%-0.50%, P≤0.025%, S≤0.020%, Alt: 0.020%-0.060%, Ti0.040-0.060%, the rest is Fe and unavoidable impurities; 380MPa strength grade: C: 0.07%-0.10%, Si: 0.10%-0.20%, Mn: 0.75%-0.90%, P≤0.025%, S≤0.020%, Alt: 0.020%-0.060%, Nb 0.007-0.020%, Ti0.050-0.065%, the rest is Fe and unavoidable impurities; 420MPa strength grade: C: 0.07%-0.10%, Si: 0.10%-0.20%, Mn: 0.75%-0.90%, P≤0.025%, S≤0.020%, Alt: 0.020%-0.060%, Ti0.060-0.075%, the rest is Fe and unavoidable impurities; Continuous annealing and galvanizing of 340MPa strength grade, 380MPa strength grade and 420MPa strength grade can be industrially produced with the same component system. The hot rolling adopts a low temperature heating process of 1240-1300℃, the final rolling temperature adopts a high temperature heating process of 850-890℃, and the hot rolling coiling adopts a coiling temperature process of 580-680℃, so as to ensure the performance of the final annealed product.

[0013] S2. Pickling: remove the hot-rolled surface oxide scale through a reasonable pickling process; provide sufficient deformation energy during annealing through a suitable pickling reduction rate to provide power for sufficient recrystallization; adopt a suitable pickling process to ensure the surface cleanliness of the cold-hardened product. The specific pickling process is as follows: tensile elongation 0.6-0.8%, pickling speed 100-150mpm, pickling temperature 80-90℃; provide high strain distortion energy for annealing recrystallization through a large cold rolling deformation rate (55-80%).

[0014] S3, continuous annealing and galvanizing, adopt appropriate annealing process, heating temperature 740-800℃, soaking temperature 740-800℃, continuous annealing line production speed 100-210mpm, galvanizing line production speed 60-100mpm, smoothing or flattening elongation 0.8-1.6%, to ensure full recrystallization and final tensile properties of the finished product.

[0015] Table 1. Hot rolling and cold rolling process temperature parameters corresponding to different strength levels Table 2. Specific production process and performance data The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-cost cold-rolled low-alloy high-strength steel production method, characterized in that: The process steps include: S1, hot coil, adopts the process of hot metal pretreatment, 150t top and bottom double blowing converter, LF furnace, continuous casting to produce slabs of qualified quality; S2, pickling, through a reasonable pickling process, remove the hot-rolled surface oxide scale, through the appropriate pickling reduction rate, provide sufficient deformation energy during annealing, and provide power for sufficient recrystallization; S3, continuous annealing and galvanizing, strictly check the surface reflectivity before entering the annealing furnace to ensure surface cleanliness and surface quality of the final product, heat the cold hard coil to above the recrystallization temperature through the continuous annealing furnace to ensure the mechanical properties of the final product, complete the annealing and cooling process through the continuous annealing furnace for continuous annealing and galvanizing, evenly apply anti-rust oil to the surface of the steel plate through the oiler, and generate the final product through the coiler.

2. The low-cost cold-rolled low-alloy high-strength steel production method according to claim 1, characterized in that: In the S1, reasonable components are designed, and the specific components are as follows: 340MPa grade: C: 0.07%-0.10%, Si: 0.10%-0.20%, Mn: 0.35%-0.50%, P≤0.025%, S≤0.020%, Alt: 0.020%-0.060%, Ti0.040-0.060%, the rest is Fe and unavoidable impurities; 380MPa grade: C: 0.07%-0.10%, Si: 0.10%-0.20%, Mn: 0.75%-0.90%, P≤0.025%, S≤0.020%, Alt: 0.020%-0.060%, Nb 0.007-0.020%, Ti0.050-0.065%, the rest is Fe and unavoidable impurities; 420MPa grade: C: 0.07%-0.10%, Si: 0.10%-0.20%, Mn: 0.75%-0.90%, P≤0.025%, S≤0.020%, Alt: 0.020%-0.060%, Ti0.060-0.075%, the rest is Fe and unavoidable impurities; Continuous annealing and galvanizing of 340MPa strength grade, 380MPa strength grade and 420MPa strength grade can be industrially produced with the same component system. The hot rolling adopts a low-temperature heating process of 1240-1300℃, the final rolling temperature adopts a high-temperature heating process of 850-890℃, and the hot rolling coiling adopts a coiling temperature process of 580-680℃, thereby ensuring the performance of the final annealed product.

3. The low-cost cold-rolled low-alloy high-strength steel production method according to claim 1, characterized in that: In S2, a suitable pickling process is adopted to ensure the surface cleanliness of the cold-hardened product. The specific pickling process is as follows: the tensile elongation is 0.6-0.8%, the pickling speed is 100-150mpm, the pickling temperature is 80-90°C, and a large cold rolling deformation rate (55-80%) is used to provide high strain distortion energy for annealing and recrystallization.

4. The low-cost cold-rolled low-alloy high-strength steel production method according to claim 1, characterized in that: In S2, a suitable emulsion is used and a suitable concentration is adopted to ensure the surface cleanliness of the cold-hardened product. The specific emulsion process is as follows: the emulsion concentration is 1.5-3.5%, and the cold-hardened coil surface reflectivity is 70-80%.

5. The low-cost cold-rolled low-alloy high-strength steel production method according to claim 1, characterized in that: In S3, a suitable annealing process is adopted, with a heating temperature of 740-800°C, a soaking temperature of 740-800°C, a production speed of 100-210mpm for the continuous annealing line, a production speed of 60-100mpm for the galvanizing line, and a smoothing or flattening elongation of 0.8-1.6%, to ensure sufficient recrystallization and final tensile properties of the finished product.

6. The low-cost cold-rolled low-alloy high-strength steel production method according to claim 1, characterized in that: In S3, an electrospark texturing leveling roller is used, the surface roughness of the leveling roller is 2.5-3.5 μm, and the actual surface roughness of the finished product is 0.8-1.6 μm, ensuring that enough anti-rust oil is stored, which is conducive to good processing performance.

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