汽车用700L大梁钢成形开裂原因分析及改进措施  

Causes analysis of forming cracks of 700Lbeam steel for automobiles and its improvement measures

作　　者：孙红智 单庆林[2] 李红斌 汪云辉[2] 陈彤 田亚强 SUN Hongzhi;SHAN Qinglin;LI Hongbin;WANG Yunhui;CHEN Tong;TIAN Yaqiang(Key Laboratory of Ministry of Education for Modern Metallurgy Technology,North China University of Science and Technology,Tangshan 063210,China;Tangshan Iron and Steel Group Co.,Ltd.,Tangshan 063000,China)

机构地区：[1]华北理工大学教育部现代冶金技术重点实验室,河北唐山063210 [2]唐山钢铁集团有限责任公司,河北唐山063000

出　　处：《轧钢》2025年第1期35-42,共8页Steel Rolling

基　　金：河北省自然科学基金重点基金项目(E2022209049)。

摘　　要：针对汽车用700L大梁钢制梁成形过程中出现的开裂问题,采用宏观形貌、微观组织分析及力学性能测试等手段,对其开裂原因进行了研究,并提出了相应的改进措施。结果表明:在大梁钢弯曲位置的横、纵两个方向上存在长度约2cm的裂纹,裂纹附近存在以Ti、N元素为主的夹杂物,平均尺寸约为13μm,面积约为44μm^(2)。大梁钢的未变形区域与弯曲变形区域的抗拉强度和屈服强度差别较小,但是弯曲变形处拉伸试样的伸长率为7.8%,而未变形处拉伸试样的伸长率为16.9%,大梁钢弯曲变形位置的止裂能力降低。在大梁钢拉伸断口颈缩处发现K、Na等元素的复合化合物,是导致大梁钢中的裂纹、气孔等缺陷增加,塑、韧性降低,开裂几率增加的原因。通过优化冶炼工艺,减少K、Na等杂质元素含量,避免K、Na等复合化合物聚集;同时,选择合适的板坯加热温度、保温时间,控制TiN夹杂物的尺寸、数量及分布情况,可大幅减少700L大梁钢开裂的风险。Aiming at the cracking problem in the forming process of 700Lbeam steel for automobile,the causes of cracking were studied by means of macro-morphology and microstructure analysis and mechanical property test,and the corresponding improvement measures were put forward.The results show that there are cracks with a length of about 2cm in the transverse and longitudinal directions of the bending position of the beam steel.There are inclusions dominated by Ti and N elements near the cracks,with an average size of about 13μm and an area of about 44μm^(2).The difference of tensile strength and yield strength between the undeformed area and the bending deformation area of the beam steel is small,but the elongation of the tensile sample at the bending deformation area is 7.8%,while the elongation of the tensile sample at the undeformed area is 16.9%,and the crack arrest ability of the bending deformation position of the beam steel is reduced.The compound compounds of K,Na and other elements were found at the necking of the tensile fracture of the beam steel,which led to the increase of cracks,pores and other defects in the beam steel,the decrease of plasticity and toughness,and the increase of cracking probability.By optimizing the smelting process,the content of impurity elements such as K and Na can be reduced,and the aggregation of composite compounds such as K and Na can be avoided.Meanwhile,selecting the appropriate slab heating temperature and holding time in the process of rolling,the size,quantity and distribution of inclusions such as TiN can be controlled,the cracking risk of 700Lbeam can be reduced.

关 键 词：700L大梁钢 成形 开裂 TiN夹杂物 K、Na化合物 止裂能力 

分 类 号：U465.11[一般工业技术—材料科学与工程] TG142[机械工程—车辆工程]