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热轧冷却方式与冷轧压下率对低碳退火板性能的影响

Impact of hot-rolling cooling pattern and cold-rolling reduction on properties of low-carbon annealed steel

  • 摘要: 针对国产化设备生产的低碳冷轧退火板,系统探究了热轧冷却工艺与冷轧压下率对材料织构及力学性能的影响机制。通过对比热轧前段冷却工艺与后段冷却工艺发现:后段冷却工艺因奥氏体高温停留时间延长,促进了晶粒粗化,使退火后屈服/抗拉强度降低约10 MPa,同时R值提升0.17。微观组织分析表明,后段冷却工艺可显著改善钢板的横向性能均匀性,抑制边部与中心区域强度差异。此外,冷轧压下率提升至62.5%以上时,边部力学性能异常点消失,混晶现象减少,111织构比例增加,并且在厚度方向上的分布更均匀。EBSD分析表明,高压下率(66.7%)可促进γ纤维织构(111//ND)的演化,再结晶过程中111<112>取向晶粒的竞争性生长主导了深冲性能的优化。研究表明,热轧后段冷却结合冷轧大压下率工艺(≥62.5%),通过储能均匀化与晶粒细化(Hall-Petch效应),有效协调强度、塑性及各向异性,使屈强比降至0.7以下,横向性能稳定性显著提升。该工艺在国产设备上实现了高成形性冷轧钢的生产可行性,为低碳钢深冲性能优化提供了理论与实践依据。

     

    Abstract: Aiming at the low-carbon cold-rolled annealed sheets produced by domestic equipment, the influence mechanisms of hot rolling cooling processes and cold rolling reduction ratios on the texture and mechanical properties of the material were systematically investigated. A comparison between the early-stage and late-stage hot rolling cooling processes revealed that the late-stage cooling process prolonged the austenite holding time at high temperature, which promoted grain coarsening, reduced the yield/tensile strength by approximately 10 MPa after annealing, and increased the R-value by 0.17 simultaneously. Microstructural analysis indicated that the late-stage cooling process could significantly improve the uniformity of the transverse properties of the steel sheet and suppress the strength difference between the edge and central regions. In addition, when the cold rolling reduction ratio was increased to more than 62.5%, the abnormal points of mechanical properties at the edge disappeared, the mixed grain phenomenon was reduced, the proportion of 111 texture increased, and the distribution was more uniform along the thickness direction. EBSD analysis showed that the high reduction ratio(66.7%) could promote the evolution of γ-fiber texture(111//ND), and the competitive growth of 111<112> oriented grains during recrystallization dominated the optimization of deep drawing performance. The research results demonstrated that the combined process of late-stage hot rolling cooling and high cold rolling reduction ratio(≥62.5%) effectively coordinated the strength, plasticity and anisotropy through strain energy homogenization and grain refinement(Hall-Petch effect), reducing the yield strength ratio to below 0.7 and significantly improving the stability of transverse properties. This process verified the production feasibility of cold-rolled steel with high formability on domestic equipment, and provided a theoretical and practical basis for the optimization of deep drawing performance of low-carbon steel.

     

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