Ultra-high-strength steel strip and method for manufacturing the same
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- BAOSHAN IRON & STEEL CO LTD
- Filing Date
- 2024-06-20
- Publication Date
- 2026-06-23
AI Technical Summary
【0063】 本発明にかかる超高強度鋼帯は、部品の寸法精度や使用安定性などに厳しい要求が課される自動車部品、例えば自動車キャビンシステムにおけるフロントシートスライドレールなどの自動車構造部品に適用可能であり、「高級·精密·先端」という精密化·安定化·差別化製品の新たな設計理念を代表し、良好な普及見通しおよび応用価値を有する。
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Abstract
Claims
1. It contains Fe and unavoidable impurity elements, and further contains the following chemical elements in the following mass percentages: C: 0.13 to 0.20%; Si: 0.15 to 0.50%; Mn: 1.4 to 2.0%; B: 0.001 to 0.004%; Al: 0.01 to 0.04%; Cr: 0.1 to 0.4%; Mo: 0.1 to 0.4%; Ti+V+Nb≦0.02%; This ultra-high-strength steel strip is characterized by its microstructure, which contains granular bainite uniformly dispersed in a coral-sea-like pattern.
2. The mass percentage content of each chemical element is: C: 0.13–0.20%; Si: 0.15–0.50%; Mn: 1.4–2.0%; B: 0.001–0.004%; Al: 0.01–0.04%; Cr: 0.1–0.4%; Mo: 0.1–0.4%; Ti + V + Nb ≤ 0.02%; the remainder is Fe and unavoidable impurity elements. The ultra-high-strength steel strip according to claim 1, characterized in that...
3. The ultra-high-strength steel strip according to claim 1 or 2, characterized in that the mass percentage content of each chemical element satisfies at least one of the following conditions: C: 0.14-0.18%; Ti+V+Nb≦0.01%.
4. The ultra-high-strength steel strip according to claim 1 or 2, further characterized in that the mass percentage content of Cr, Mo, and C satisfies the condition 2.7 ≤ (Cr + Mo) / C ≤ 3.
3.
5. The ultra-high-strength steel strip according to claim 1 or 2, characterized in that the mass percentage content of unavoidable impurity elements satisfies at least one of the following conditions: P ≤ 0.012%, S ≤ 0.004%, N ≤ 0.004%.
6. The volume phase ratio of the granular bainite is ≥ 95.0%; preferably, the area of the granular bainite is ≤ 5 μm ２ The ultra-high-strength steel strip according to claim 1 or 2, characterized in that the aspect ratio is ≤2:1; preferably, the microstructure further contains ferrite, and the volume phase ratio of the ferrite is 0.1 to 4.5%.
7. In all regions of the steel strip except for areas 30 μm away from the top and bottom surfaces in the thickness direction, any cross-sectional area ≤ 50 μm ２ Within the region, the granular bainite is uniformly distributed; preferably, in the entire region except for the regions 20 μm away from the upper and lower surfaces of the steel strip in the thickness direction, any cross-sectional area ≤ 10 μm ２ The ultra-high-strength steel strip according to claim 1 or 2, characterized in that granular bainite is uniformly distributed within the region.
8. The ultra-high-strength steel strip according to claim 1 or 2, characterized in that the tensile strength is ≥1000 MPa, the yield strength is ≥780 MPa, preferably ≥800 MPa, more preferably ≥850 MPa, and even more preferably ≥880 MPa; and the low anisotropy satisfies that the difference in yield strength between the transverse and longitudinal directions at the same position on the steel strip is ≤25 MPa and the difference in tensile strength is ≤20 MPa; and the internal mechanical uniformity of the coil satisfies that, for the same steel coil, the difference in yield strength at different positions in the same elongation direction along its longitudinal or width direction is ≤25 MPa and the difference in tensile strength is ≤20 MPa; and preferably, the elongation at break is ≥10% and / or the hole expansion ratio is ≥50%.
9. A method for manufacturing an ultra-high-strength steel strip according to any one of claims 1 to 8, characterized by comprising the following steps. Smelting and casting; Hot rolling; Post-rolling cooling and winding: Post-rolling cooling employs a multi-stage cooling method that alternates between rapid and slow cooling. Finally, the steel strip body is cooled to the winding temperature of 440°C to 520°C at a cooling rate of 5 to 100°C for the region excluding the leading and trailing 100m of the steel strip, while the leading and trailing 100m of the steel strip is cooled to the leading and trailing winding temperature of 480°C to 560°C at a cooling rate of 5 to 25°C for the region excluding the leading and trailing 100m of the steel strip. Pickling and cold rolling; Annealing: Heat to 840-900°C at a heating rate of ≤50°C / s and hold the temperature, then cool to 700-780°C at a cooling rate of 2-20°C / s and hold the temperature, then cool to 360-430°C at a cooling rate of 20-50°C and hold the temperature, then heat to 440-480°C at a heating rate of 5-30°C / s, then cool to 330-400°C at a cooling rate of 0.1-0.5°C / s, and finally cool to room temperature at a cooling rate of 15-50°C / s and wind up.
10. The manufacturing method according to claim 9, characterized in that, in the hot rolling step, the heating temperature is controlled to 1180 to 1280°C and the finish rolling completion temperature is controlled to 870 to 970°C; and / or, in the width direction of the cross-section of the steel strip after finish rolling, the difference between the thickness at the center point and the thickness in the region within 40 cm from the edge is controlled to ≤ 50 μm.
11. The manufacturing method according to claim 9, characterized in that, throughout the hot rolling process, the post-rolling cooling and winding process, the temperature difference between the non-intermediate region and the intermediate region in the width direction of the steel strip at the same time is controlled to ≤30°C, and the temperature fluctuation between the intermediate region and the non-intermediate region in the longitudinal direction is controlled to ≤15°C; and / or, throughout the annealing process, the temperature difference between the non-intermediate region and the intermediate region in the width direction of the steel strip at the same time is controlled to ≤10°C, and the temperature fluctuation between the intermediate region and the non-intermediate region in the longitudinal direction of the steel strip is controlled to ≤5°C.
12. In the post-rolling cooling process, the rapid cooling rate is 50 to 200°C / s, and the slow cooling rate is 5 to 30°C / s, preferably 5 to 25°C / s; preferably, the initial rapid cooling stop temperature is 680 to 760°C, and the final slow cooling stop temperature is 490 to 570°C; preferably, except for the initial rapid cooling, the temperature of the steel strip is reduced by 20 to 160°C with each cooling, preferably 30 to 80°C; more preferably, the rapid cooling and slow cooling are performed alternately. The manufacturing method according to claim 9, characterized in that the stage cooling specifically includes: a first stage of cooling the steel strip to 680 to 760°C at a cooling rate of 100 to 200°C / s; a second stage of cooling the steel strip to 600 to 670°C at a cooling rate of 5 to 30°C / s, preferably 5 to 25°C / s; a third stage of cooling the steel strip to 520 to 590°C at a cooling rate of 50 to 150°C / s; and a fourth stage of cooling the steel strip to 490 to 570°C at a cooling rate of 5 to 30°C / s, preferably 5 to 25°C / s.
13. The manufacturing method according to claim 9, characterized in that, in the cold rolling process, the cold rolling reduction ratio is controlled to be ≥30%, and the target thickness of the steel strip is controlled such that the difference between the thickness at the center point and the thickness at any position within 40 cm from the edge in the width direction of the cross-section of the steel strip is ≤30 μm.
14. The manufacturing method according to claim 9, characterized in that, in the annealing process, when the heating temperature is ≥ 870°C, the holding time is ≤ 2 min, and when the heating temperature is < 870°C, the holding time is > 2 min.
15. The manufacturing method according to claim 9, characterized in that, in the annealing process, the material is heated to 840 to 900°C at a heating rate of ≤50°C / s and held for 1 to 4 minutes, then cooled to 700 to 780°C at a cooling rate of 2 to 20°C / s and held for 10 to 40 seconds, and then cooled to 360 to 430°C at a cooling rate of 20 to 50°C and held for 2.5 to 10 seconds.