低镍奥氏体不锈钢冷轧边裂原因分析

针对低镍Cr-Mn-Ni-N奥氏体不锈钢冷连轧过程中的边裂问题,采用金相显微镜、扫描电子显微镜分析了断口、边裂位置附近、正常位置显微形貌;分析了冷轧带钢横向应力、轧制力分布规律。结果表明,钢中镍元素偏析、存在Al₂O₃夹杂物、形变马氏体组织含量增加,以及带钢边部应力、轧制力较大,是导致低镍奥氏体不锈钢冷连轧过程出现边裂,甚至导致断带的主要原因。为此,提出了连铸冷却模式采用弱冷;在热连轧铸坯加热及后工序带钢固溶退火工艺中对材料合金元素进行均质化处理;优化冷连轧工艺,保证第1道次压下率为30%~35%,总压下率为50%~68%,使马氏体形变组织得到有效控制;保证原料楔形、板凸度等在合理范围内,并通过调整弯辊力来改善轧制力的横向分布等措施,使带钢轧后边裂断带率由0.98%降至0.25%。

Cause analysis of edge crack of low nickel austenitic stainless steel strip during cold rolling

Aiming at the edge crack problem of low nickel Cr-Mn-Ni-N austenitic stainless steel strip during cold rolling, the metallurgical microscope, scanning electron microscope were used to analyze the microscopic morphology of the fracture, edge crack position and the normal position; the distribution law of the transverse stress and rolling force of the cold rolled strip was analyzed. The results show that the segregation of nickel in the steel, the presence of Al₂O₃ inclusions, the increase in the content of deformed martensite microstructure, and the greater stress and rolling force at the edge of the strip lead to edge cracks in the cold tandem rolling,and finally even lead to the strip broken. Therefore, the weak cooling model of continuous casting is proposed. The alloy elements are homogenized in billet heating and the subsequent strip solution annealing process. The cold continuous rolling process is optimized to ensure the first pass reduction rate is 30%-35%, and the total reduction rate is 50%-68%, so that the deformation martensite structure can be effectively controlled. The wedge shape and crown of raw material should be controlled within a reasonable range, and the transverse distribution of rolling force is improved by adjusting the roll bending force. Based on these measures, the rate of edge crack to break of strip is reduced from 0.98% to 0.25%.