Rolling method of 4-5mm ultrathin low-density high-strength steel
By employing a coil rolling method involving preheating, heating, descaling, rolling, and straightening, combined with DNN algorithm optimization of rolling force, the problem of one-time forming of ultra-thin, low-density, high-strength steel has been solved, achieving efficient, low-cost mass production and superior performance.
Patent Information
- Application Number
- CN202511046496.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-29
- Publication Date
- 2025-12-09
AI Technical Summary
Existing technologies make it difficult to achieve one-time rolling of 4-5mm ultrathin low-density high-strength steel, resulting in a long production process, high cost, low efficiency, and insufficient rolling precision, which cannot meet the needs of mass production.
A coil rolling method involving preheating, heating, descaling, rolling, primary straightening, and secondary straightening is adopted. The rolling force is calculated by combining a DNN integrated neural network algorithm with a deep learning and deformation resistance mechanism model to ensure one-time forming and optimize the rolling process.
It achieves one-time forming of 4~5mm ultra-thin low-density high-strength steel, reducing production costs by 25%~30%, increasing production efficiency by 40%, improving rolling precision to an error of ≤3%, and producing products with excellent performance that meet the requirements of lightweight and high strength.
Smart Images
Figure CN121082684A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of steel rolling technology, specifically relating to a method for rolling 4-5mm ultra-thin low-density high-strength steel coils, which is particularly suitable for the mass production of ultra-thin specifications of Fe-Mn-Al-C austenitic low-density high-strength steel. Background Technology
[0002] With the increasing demand for lightweight and high safety in automobiles, ships, and special equipment, low-density high-strength steel has become a key material. Low-density steel is usually made by adding elements such as Al and Mn to reduce density (each 1% increase in Al can reduce density by 0.101 g / cm³), while ensuring high strength (yield strength ≥900 MPa) and good toughness.
[0003] In existing technologies, the maximum thickness for low-density steel coils formed in a single rolling process is 6-8 mm. Thicknesses of 4-5 mm require secondary processing such as cold rolling and grinding, which presents the following problems: Secondary processing leads to a longer production process and higher costs (more than 30% higher than the cost of primary rolling). Cold rolling can easily introduce residual stress, requiring an additional process to eliminate it, which affects production efficiency. Mass production is not possible (the current process has a daily capacity of ≤50 tons).
[0004] Furthermore, traditional rolling calculations rely on empirical formulas, resulting in low accuracy (error ≥8%), making them unsuitable for rolling ultra-thin, low-density steel. Therefore, a method for single-pass rolling of 4-5mm ultra-thin, low-density, high-strength steel is urgently needed to address these issues. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to provide a method for rolling 4-5mm ultrathin low-density high-strength steel in a coil, which achieves one-time rolling forming, shortens the process, reduces costs, and at the same time ensures the strength, toughness and density performance of the product to meet the needs of mass production.
[0006] The technical solution adopted by the present invention to solve the above problems is: a method for rolling 4-5mm ultra-thin low-density high-strength steel coils, comprising the following steps: preheating, heating, descaling, rolling, primary straightening, shearing, and secondary straightening; Preheating: Based on the slab after casting (size: thickness 100~110mm × width 1500~1700mm × length 4300~5000mm), the slab to be processed is clamped between two hot billets at 400~600℃ and kept at the temperature for 12~15h to ensure that the temperature difference between the core and the surface of the slab is ≤50℃; Heating: After preheating, the slab enters a regenerator for heating. The heating process is as follows: preheating section 700~1000℃, first heating section 900~1100℃, second heating section 1050~1250℃, and soaking section 1170~1230℃; furnace time 1.5~2min / mm (total time ≥150min), heating rate 1.5~2℃ / s, ensuring that the core temperature of the slab reaches 1170~1230℃ and the uniformity is ≤30℃; Descaling: After exiting the furnace, the surface iron oxide scale is removed by passing the high-pressure water at a speed of 1.5~2m / s (water pressure 18~22MPa). The rolling temperature is controlled at 1050~1080℃. Rolling: Reversible alternating rolling is adopted, with 1 to 3 passes of on-machine descaling throughout the process (water pressure 20 to 25 MPa), and the roller cooling water is turned off; Roughing in 4 passes: low speed and large reduction, pass reduction rate 25%~45%, cumulative reduction >80mm, rolling speed 2.0~3.2m / s; Finishing rolling in 5 passes: The coiling furnace is used for auxiliary heat preservation (temperature 900~950℃). Passes 6-8 have a speed of 5.0~5.5m / s, and pass 9 (leveling pass) has a speed of 1.2~1.8m / s. The pass reduction rate is 12%~35%, using high rolling force (30000~60000kN). The rolling force is calculated using a DNN integrated neural network algorithm, which combines deep learning with a deformation resistance mechanism model. The input parameters include chemical composition, deformation temperature, rate, and degree. First straightening: After rolling, the material enters a hot straightening machine at 400~500℃ and is straightened in 3~5 passes (pressure 2000~3000kN) to eliminate rolling stress; Cutting: The fixed-length shears cut the mother board into sub-boards of 4000~15000mm, with an error of ≤±5mm, and simultaneously print the material, specifications and batch number markings; Secondary straightening: After the subplate is air-cooled to 200~300℃, it is shot-blasted (steel shot diameter 0.8~1.2mm), and then straightened 4~6 times by a high-strength straightening machine (pressure 4000~5000kN) to ensure flatness ≤2mm / m.
[0007] Compared with the prior art, the present invention has the following beneficial effects: 1. One-time roll forming of 4-5mm ultra-thin specifications eliminates the need for cold rolling and grinding processes, reducing production costs by 25%-30% and increasing production efficiency by more than 40% (daily capacity ≥80 tons). 2. The design incorporates hot billet clamping preheating, coiling furnace insulation, and roller table water shut-off to reduce temperature drop (temperature drop rate during rolling ≤ 5℃ / s) and ensure rolling stability; 3. The DNN algorithm improves the accuracy of rolling force prediction (error ≤ 3%), avoiding mill overload or insufficient reduction; 4. Excellent product performance: density 6.63~7.19g / cm³ (10%~15% lighter than ordinary carbon steel of the same thickness), yield strength 900~1050MPa, tensile strength 1000~1150MPa, V-type impact energy ≥50J at -40℃, meeting the requirements of lightweight and high strength. Attached Figure Description
[0008] Figure 1 This is a heating process diagram of an embodiment of the present invention; Figure 2 This is a schematic diagram of the rolling process according to an embodiment of the present invention; Figure 3 This is a flowchart of the DNN integrated neural network algorithm according to an embodiment of the present invention. Detailed Implementation
[0009] The technical solution of the present invention will be described in more detail below with reference to preferred embodiments. However, these embodiments are merely descriptions of preferred implementations of the present invention and should not be construed as limiting the scope of the present invention.
[0010] Example 1: Rolling 100mm billet into 4mm steel plate Preheating: The billet size is 100mm×1500mm×5000mm. It is held between two 500℃ hot billets and kept at the temperature for 12 hours. The core-surface temperature difference is 40℃. Heating: Preheating section 800℃, first heating section 1000℃, second heating section 1150℃, soaking section 1200℃; furnace time 160min (1.6min / mm), core temperature 1200℃; Descaling: Descaling is performed at a speed of 1.8 m / s, with an initial rolling temperature of 1060℃; Rolling: Rough rolling in 4 passes: reduction rates of 25.98%, 31.73%, 37.6%, and 43.84% respectively, with a cumulative reduction of 82.3 mm and a speed of 2.19~3.02 m / s; Finishing rolling in 5 passes: coiling furnace temperature 920℃, speed of 5.2m / s for passes 6-8, and 1.5m / s for pass 9; reduction rates are 33.7%, 32.53%, 26.01%, 18.04%, and 12.56% respectively. The rolling force was calculated using a DNN algorithm, with a prediction error of 2.8%. One-pass straightening: 3 straightening passes at 450℃, stress relief rate 85%; Shearing: Cut into 6000mm sub-plates, with an error of ±3mm; Secondary straightening: After shot blasting, 5 passes of high-intensity straightening are performed to achieve a flatness of 1.5 mm / m.
[0011] Product performance: Thickness 4.16mm, density 6.82g / cm³, yield strength 980MPa, tensile strength 1080MPa, impact energy at -40℃ 55J, hardness 65HRC.
[0012] Example 2: Rolling 110mm billet into 5mm steel plate Preheating: The billet size is 110mm×1600mm×4500mm. It is held between two 550℃ hot billets and kept at the temperature for 14 hours. The core-to-surface temperature difference is 35℃. Heating: Preheating section 900℃, first heating section 1050℃, second heating section 1200℃, soaking section 1220℃; furnace time 180min (1.64min / mm), core temperature 1220℃; Descaling: Descaling is performed at a speed of 2.0 m / s, with an initial rolling temperature of 1070℃; Rolling: Rough rolling in 4 passes: reduction rates of 28%, 33%, 38%, and 42% respectively, with a cumulative reduction of 85 mm and a speed of 2.3~3.1 m / s; Finishing rolling in 5 passes: coiling furnace temperature 940℃, speed of 5.3m / s for passes 6-8, and 1.6m / s for pass 9; reduction rates are 34%, 33%, 27%, 19%, and 13% respectively. One-pass straightening: 4 passes at 480℃, stress relief rate of 88%; Secondary straightening: After shot blasting, 6 passes of high-strength straightening are performed, achieving a flatness of 1.8 mm / m.
[0013] Product performance: Thickness 5.02mm, density 6.95g / cm³, yield strength 1020MPa, tensile strength 1120MPa, impact energy at -40℃ 52J, hardness 67HRC.
[0014] This invention employs a DNN integrated neural network algorithm that combines deep learning algorithms with traditional deformation resistance mechanism models, applying artificial intelligence-related theories and technologies to the control and optimization of rolling process parameters. Traditional mathematical models of deformation resistance are derived from numerous experiments, resulting in various regression formulas. However, the metal rolling process is characterized by typical multivariate, nonlinear, and strongly coupled features, making it difficult to describe with precise formulas. Based on the deep learning neural network algorithm, not only are key factors such as deformation rate, deformation temperature, and deformation degree considered, but the effects of chemical composition fluctuations, residual strain, recovery, and recrystallization are also fully taken into account. This combination improves the accuracy of deformation resistance calculations.
Claims
1. A method for rolling 4-5mm ultrathin low-density high-strength steel coils, characterized in that, The process includes the following steps: preheating, heating, descaling, rolling, primary straightening, shearing, and secondary straightening. Preheating: Based on the slab after the die casting, the slab to be processed is clamped between two hot billets at 400~600℃ and kept at the temperature for 12~15 hours; Heating: The furnace is heated in the following stages: preheating section 700~1000℃, first heating section 900~1100℃, second heating section 1050~1250℃, soaking section 1170~1230℃, furnace time 1.5~2min / mm; Descaling: Descaling at a speed of 1.5~2m / s, with an initial rolling temperature of 1050~1080℃; Rolling: Reversible alternating rolling is adopted, with 4 passes for roughing, a cumulative reduction of >80mm, 5 passes for finishing, and holding in the coiling furnace at 900~950℃, for a total of 9 passes to form the finished product; One-time straightening: hot straightening at 400~500℃; Cutting: Cut to length for segmentation; Secondary straightening: After shot blasting, perform strong straightening multiple times.
2. The method for rolling 4-5mm ultra-thin low-density high-strength steel coils according to claim 1, characterized in that, During the preheating step, after the slab to be processed is clamped with the hot slab, the temperature difference between the core and the surface is ≤50℃.
3. The method for rolling 4-5mm ultra-thin low-density high-strength steel coils according to claim 1, characterized in that: In the heating step, the total heating time is ≥150min, the core temperature of the slab reaches 1170~1230℃, and the temperature difference between the core and the surface is ≤30℃.
4. The method for rolling 4-5mm ultra-thin low-density high-strength steel coils according to claim 1, characterized in that: The descaling step uses high-pressure water descaling with a water pressure of 18~22MPa, and the surface iron oxide scale removal rate is ≥98% after descaling.
5. The method for rolling 4-5mm ultra-thin low-density high-strength steel coils according to claim 1, characterized in that: In the rolling process, the roughing pass has a reduction rate of 25% to 45% and a rolling speed of 2.0 to 3.2 m / s; the finishing pass has a speed of 5.0 to 5.5 m / s for the 6th to 8th passes and a speed of 1.2 to 1.8 m / s for the 9th pass and the leveling pass.
6. The method for rolling 4-5mm ultra-thin low-density high-strength steel coils according to claim 1, characterized in that: In the rolling step, the rolling force is calculated using a DNN integrated neural network algorithm. This algorithm combines deep learning with a deformation resistance mechanism model, and the input parameters include chemical composition, deformation temperature, deformation rate, and degree of deformation.
7. The method for rolling 4-5mm ultra-thin low-density high-strength steel coils according to claim 1, characterized in that: The straightening process is performed using a hot straightening machine, with 3 to 5 straightening passes, a straightening pressure of 2000 to 3000 kN, and a stress relief rate of ≥80%.
8. The method for rolling 4-5mm ultra-thin low-density high-strength steel coils according to claim 1, characterized in that: Before the secondary straightening, shot blasting is performed with steel shot diameter of 0.8~1.2mm, and the surface roughness Ra after shot blasting is ≤12.5μm; the secondary straightening passes 4~6 times, the straightening pressure is 4000~5000kN, and the flatness is ≤2mm / m.
9. The method for rolling 4-5mm ultra-thin low-density high-strength steel coils according to claim 1, characterized in that: The steel plate prepared by the method has the following properties: thickness 4~5mm, density 6.63~7.19g / cm³, yield strength 900~1050MPa, tensile strength 1000~1150MPa, V-type impact energy ≥50J at -40℃, and hardness 62~68HRC.
10. The method for rolling 4-5mm ultra-thin low-density high-strength steel coils according to claim 1, characterized in that: During the rolling process, the roller cooling water is turned off, and on-machine descaling is used for the first to third passes, with an on-machine descaling water pressure of 20 to 25 MPa.