A rolling and cooling method of a 500mpa grade fine-grained high-strength steel
By controlling the temperature and speed during the rolling process, and by not cooling the strip for 2m±0.5m before the head of the strip, combined with a reasonable cooling method, the problem of temperature control during QSTE500TM steel coil winding was solved, achieving the required strength and smooth winding, thus avoiding economic losses.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANDONG TAISHAN STEEL GROUP
- Filing Date
- 2024-04-09
- Publication Date
- 2026-07-28
AI Technical Summary
In the production of QSTE500TM steel coils, the current technology makes it difficult to control the coiling temperature at 590℃±20℃, resulting in substandard product strength and economic losses.
By controlling the temperature and speed during the rolling process, and by not cooling the strip for 2m ± 0.5m before the head of the strip, combined with a reasonable cooling method, and adjusting the cooling method of the rest of the strip, the coiling temperature is ensured to be within the required range.
The QSTE500TM steel coil achieved the required strength, ensuring smooth winding and good coil shape, avoiding scrap steel and steel grade downgrading, and reducing economic losses.
Smart Images
Figure BDA0004781305860000051
Abstract
Description
Technical Field
[0001] This invention relates to the field of steel coil production technology, and in particular to a rolling and cooling method for 500MPa grade fine-grained high-strength steel. Background Technology
[0002] QSTE500TM is a fine-grained steel with high strength, good elongation and bending properties. It can be used for parts with high formability requirements. It is mainly used in automotive structural parts, such as beams, wheels, spokes and rims, automotive parts, load-bearing parts and components of mechanical equipment, and load-bearing parts of construction machinery, such as the frame of electric forklifts, the boom of small-tonnage cranes, and the frame.
[0003] In the production process of steel coils, after hot rolling, the coils are cooled and then wound up. To ensure smooth winding and good coil shape during winding, the current common practice is to cool the strip by leaving a 20m long section at the head and tail of the strip without cooling. Although this achieves the goal of smooth winding and good coil shape, it will cause the final strength of the product to fail to meet the requirements.
[0004] Research has revealed that the coiling temperature of QSTE500TM steel coils needs to be controlled at 590℃±20℃ to ensure the required strength. However, using existing rolling and cooling methods, the coiling temperature is difficult to achieve in the first 4-10 coils of QSTE500TM production, resulting in substandard strength and rendering the coils scrap or downgrading the steel grade, leading to economic losses. Therefore, there is an urgent need for a rolling and cooling method specifically for QSTE500TM steel coils to ensure their required strength. Summary of the Invention
[0005] This invention addresses the shortcomings of existing technologies by providing a rolling and cooling method for 500MPa grade fine-grained high-strength steel. Research has shown that the coiling temperature of QSTE500TM steel coils needs to be controlled at 590℃±20℃ to ensure the product strength meets requirements. This invention achieves this by rationally controlling the temperature and speed at each stage of the rolling process and adjusting the cooling method. Only the first 2m±0.5m of the strip head is not cooled, while the rest is subjected to layer cooling. Through the combination of rolling and cooling methods, the coiling temperature of the strip reaches the standard during coiling, ensuring that the mechanical properties of the steel coil meet the requirements.
[0006] The first aspect of the present invention provides a rolling and cooling method for 500MPa grade fine grain high strength steel, comprising the following steps: (1) roughing and finishing of strip steel: controlling the starting rolling temperature of the roughing rolling of strip steel to be 1140℃±30℃, the finishing rolling temperature of the roughing rolling to be 1080℃±20℃, the starting rolling temperature of the finishing rolling to be 1030℃±20℃, and the finishing rolling temperature of the finishing rolling to be 880℃±20℃;
[0007] (2) Cooling and coiling: When cooling the strip, the first 2m ± 0.5m of the strip head is not cooled, so that the coiling temperature of the strip head is 600-610℃, the coiling temperature of the strip body is 580-600℃, and the coiling temperature of the strip tail is 590-610℃.
[0008] Preferably, in step (1), the temperature of the soaking zone is controlled to be 1260-1280℃ before the rough rolling begins.
[0009] Preferably, in step (1), the finishing rolling is performed in 7 passes, with the highest finishing rolling speed being 5-5.4 m / s and the lowest speed being 1.05-1.15 m / s.
[0010] Preferably, the rolling speed for the first pass is 1.05-1.15 m / s, the rolling speed for the second pass is 1.50-1.75 m / s, the rolling speed for the third pass is 2.0-2.5 m / s, the rolling speed for the fourth pass is 2.9-3.4 m / s, the rolling speed for the fifth pass is 3.7-4.2 m / s, the rolling speed for the sixth pass is 4.5-5.0 m / s, and the rolling speed for the seventh pass is 5.0-5.4 m / s.
[0011] Preferably, the roll gap width of the first finishing pass is 18-20 mm, the roll gap width of the second finishing pass is 11-13 mm, the roll gap width of the third finishing pass is 8-9 mm, the roll gap width of the fourth finishing pass is 5-7 mm, the roll gap width of the fifth finishing pass is 4-6 mm, the roll gap width of the sixth finishing pass is 4.5-5 mm, and the roll gap width of the seventh finishing pass is 5-5.5 mm.
[0012] Preferably, the chemical composition of the strip steel is as follows (by mass percentage): C 0.07%–0.11%, Si 0.10%–0.25%, Mn 1.15%–1.45%, P ≤0.020%, S ≤0.010%, Alt 0.020%–0.050%, Nb 0.010%–0.025%, Ti 0.035%–0.060%, Nb+V+Ti ≤0.22%, with the balance being iron.
[0013] Preferably, in step (2), cooling is achieved by spraying cold water, with a spray flow rate of 5-6 m³ / h. 3 The forward speed of the strip is 5-5.4 m / s.
[0014] A second aspect of the present invention provides a QSTE500TM steel coil prepared using the above-described rolling and cooling methods.
[0015] The beneficial effects of this invention are as follows:
[0016] This invention achieves this by rationally controlling the temperature and speed at each stage of the rolling process and adjusting the cooling method. Only the first 2m ± 0.5m of the strip head is not cooled, while the rest is subjected to layer cooling. Through the combination of rolling and cooling methods, the coiling temperature of the strip reaches the standard when it is coiled, which not only ensures that the mechanical properties of the steel coil meet the standard, but also achieves the purpose of smooth coiling and good coil shape. Detailed Implementation
[0017] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.
[0018] Example 1
[0019] A rolling and cooling method for QSTE500TM steel includes the following steps: (1) roughing and finishing of strip steel: the initial rolling temperature of the roughing rolling is controlled at 1137℃, the final rolling temperature of the roughing rolling is controlled at 1087℃, the temperature of the soaking zone is controlled at 1266℃ before the roughing rolling begins, the initial rolling temperature of the finishing rolling is 1029℃, and the final rolling temperature of the finishing rolling is 869℃; finishing rolling is performed in 7 passes, with the rolling speed of the first pass being 1.13m / s, the rolling speed of the second pass being 1.71m / s, the rolling speed of the third pass being 2.41m / s, the rolling speed of the fourth pass being 3.35m / s, the rolling speed of the fifth pass being 4.16m / s, the rolling speed of the sixth pass being 4.93m / s, and the rolling speed of the seventh pass being 5.39m / s;
[0020] The roll gap width for the first finishing pass is 19.88 mm, for the second finishing pass it is 13 mm, for the third finishing pass it is 8.69 mm, for the fourth finishing pass it is 6.47 mm, for the fifth finishing pass it is 5.16 mm, for the sixth finishing pass it is 4.98 mm, and for the seventh finishing pass it is 5.30 mm.
[0021] (2) Cooling and coiling: When cooling the strip, the first 2m ± 0.5m of the strip head is not cooled, so that the coiling temperature of the strip head is 607℃, the coiling temperature of the strip body is 597℃, and the coiling temperature of the strip tail is 600℃.
[0022] The chemical composition of the strip steel by mass percentage is as follows: C 0.08%, Si 0.18%, Mn 1.26%, P≤0.020%, S≤0.010%, Alt 0.027%, Nb0.014%, Ti0.041%, Nb+V+Ti≤0.22%, with the balance being iron.
[0023] Example 2
[0024] A rolling and cooling method for QSTE500TM steel includes the following steps: (1) roughing and finishing of strip steel: the starting rolling temperature of the roughing rolling is controlled at 1122℃, the finishing rolling temperature is controlled at 1082℃, the temperature of the soaking zone is controlled at 1265℃ before the roughing rolling starts, the starting rolling temperature of the finishing rolling is 1038℃, and the finishing rolling temperature is 868℃; finishing rolling is performed in 7 passes, the rolling speed of the first pass is 1.12m / s, the rolling speed of the second pass is 1.70m / s, the rolling speed of the third pass is 2.41m / s, the rolling speed of the fourth pass is 3.33m / s, the rolling speed of the fifth pass is 4.20m / s, the rolling speed of the sixth pass is 4.95m / s, and the rolling speed of the seventh pass is 5.39m / s;
[0025] The roll gap width for the first finishing pass is 19.84 mm, for the second finishing pass it is 12.99 mm, for the third finishing pass it is 8.56 mm, for the fourth finishing pass it is 6.36 mm, for the fifth finishing pass it is 4.99 mm, for the sixth finishing pass it is 4.84 mm, and for the seventh finishing pass it is 5.23 mm.
[0026] (2) Cooling and coiling: When cooling the strip, the first 2m ± 0.5m of the strip head is not cooled, so that the coiling temperature of the strip head is 606℃, the coiling temperature of the strip body is 591℃, and the coiling temperature of the strip tail is 594℃.
[0027] The chemical composition of the strip steel by mass percentage is as follows: C 0.10%, Si 0.19%, Mn 1.22%, P≤0.020%, S≤0.010%, Alt 0.029%, Nb0.014%, Ti0.037%, Nb+V+Ti≤0.22%, with the balance being iron.
[0028] Example 3
[0029] A rolling and cooling method for QSTE500TM steel includes the following steps: (1) roughing and finishing of strip steel: the starting rolling temperature of the roughing rolling is controlled at 1154℃, the finishing rolling temperature is controlled at 1084℃, the temperature of the soaking zone is controlled at 1272℃ before the roughing rolling starts, the starting rolling temperature of the finishing rolling is 1027℃, and the finishing rolling temperature is 865℃; finishing rolling is performed in 7 passes, the rolling speed of the first pass is 1.06m / s, the rolling speed of the second pass is 1.58m / s, the rolling speed of the third pass is 2.19m / s, the rolling speed of the fourth pass is 2.97m / s, the rolling speed of the fifth pass is 3.76m / s, the rolling speed of the sixth pass is 4.56m / s, and the rolling speed of the seventh pass is 5.06m / s;
[0030] The roll gap width for the first finishing pass is 18.38 mm, for the second finishing pass it is 11.94 mm, for the third finishing pass it is 8.06 mm, for the fourth finishing pass it is 5.95 mm, for the fifth finishing pass it is 4.49 mm, for the sixth finishing pass it is 4.62 mm, and for the seventh finishing pass it is 5.02 mm.
[0031] (2) Cooling and coiling: When cooling the strip, the first 2m ± 0.5m of the strip head is not cooled, so that the coiling temperature of the strip head is 602℃, the coiling temperature of the strip body is 590℃, and the coiling temperature of the strip tail is 608℃.
[0032] The chemical composition of the strip steel by mass percentage is as follows: C 0.09%, Si 0.15%, Mn 1.15%, P≤0.020%, S≤0.010%, Alt 0.046%, Nb0.015%, Ti0.050%, Nb+V+Ti≤0.22%, with the balance being iron.
[0033] The products prepared in Examples 1-3 were subjected to performance testing, and the test results are shown in Table 1.
[0034] Table 1
[0035]
[0036] In summary, the QSTE500TM steel coils produced by the rolling and cooling method of the present invention meet the strength requirements.
[0037] Of course, the above description is not limited to the examples above. Technical features not described in this invention can be implemented by or using existing technology, and will not be repeated here. The above embodiments are only used to illustrate the technical solutions of this invention and are not intended to limit this invention. This invention has been described in detail with reference to preferred embodiments. Those skilled in the art should understand that any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this invention do not depart from the spirit of this invention and should also fall within the scope of protection of the claims of this invention.
Claims
1. A rolling and cooling method for 500MPa grade fine-grained high-strength steel, characterized in that, Includes the following steps: (1) For strip roughing and finishing: the initial rolling temperature of the strip roughing is controlled at 1140℃±30℃, the final rolling temperature of the roughing is controlled at 1080℃±20℃, the initial rolling temperature of the finishing is controlled at 1030℃±20℃, and the final rolling temperature of the finishing is controlled at 880℃±20℃; the roll gap width of the first pass of the finishing is 18-20mm, the roll gap width of the second pass is 11-13mm, the roll gap width of the third pass is 8-9mm, the roll gap width of the fourth pass is 5-7mm, the roll gap width of the fifth pass is 4-6mm, and the roll gap width of the sixth pass is... The roll gap width for the seventh pass of the finishing mill is 4.5-5mm, and the roll gap width for the seventh pass is 5-5.5mm. The rolling speed for the first pass of the finishing mill is 1.05-1.15m / s, the rolling speed for the second pass is 1.50-1.75m / s, the rolling speed for the third pass is 2.0-2.5m / s, the rolling speed for the fourth pass is 2.9-3.4m / s, the rolling speed for the fifth pass is 3.7-4.2m / s, the rolling speed for the sixth pass is 4.5-5.0m / s, and the rolling speed for the seventh pass is 5.0-5.4m / s. (2) Cooling and coiling: When cooling the strip, the first 2m ± 0.5m of the strip head is not cooled, so that the coiling temperature of the strip head is 600-610℃, the coiling temperature of the strip body is 580-600℃, and the coiling temperature of the strip tail is 590-610℃.
2. The rolling and cooling method for a 500MPa grade fine-grained high-strength steel according to claim 1, characterized in that: In step (1), the temperature of the soaking zone is controlled to be 1260-1280℃ before the rough rolling begins.
3. The rolling and cooling method for a 500MPa grade fine-grained high-strength steel according to claim 1, characterized in that, The chemical composition of the strip steel by mass percentage is as follows: C 0.07%~0.11%, Si 0.10%~0.25%, Mn 1.15%~1.45%, P≤0.020%, S≤0.010%, Alt 0.020%~0.050%, Nb0.010%~0.025%, Ti0.035%~0.060%, Nb+V+Ti≤0.22%, and the balance is iron.
4. The rolling and cooling method for a 500MPa grade fine-grained high-strength steel according to claim 1, characterized in that: In step (2), cooling is achieved by spraying cold water to lower the temperature.
5. A QSTE500TM steel coil prepared by the rolling and cooling method of a 500MPa grade fine-grained high-strength steel according to any one of claims 1-4.