Q195钢冷镦开裂原因分析

采用酸洗、光学显微镜以及扫描电镜—能谱(SEM+EDS)等方法,分析了Q195冷镦钢轧材及冷镦试样的表面质量、裂纹形貌、金相组织、氧氮含量和非金属夹杂物对冷镦钢开裂的影响。结果表明,钢中T[O]含量为154×10-6,钢中夹杂物含量较高;在轧材裂纹处发现大尺寸夹杂物,同时在轧材靠近边缘1/4处发现较多大尺寸夹杂物聚集分布现象,其成分与连铸结晶器保护渣成分相似,大型夹杂物在冷镦过程中引起应力集中从而导致和加剧冷镦开裂程度。同时由于轧制工艺控制不当,使得产品表面形成折叠缺陷,产生180°通条对称纵裂纹,是导致冷镦开裂的主要原因。

Analysis of Cracking Reasons in the Cold Heading Process of Q195 Steel

The surface quality,crack morphologies,microstructures,oxygen and nitrogen content and non-metallic inclusions of Q195 cold heading steel were studied by a set of analysis techniques,such as acid washing,optical microscopy,scanning electronic microscope (SEM),and energy dispersive X-ray spectroscopy (EDS).The results showed that the total oxygen content in steel was 154×10-6,which indicated that non-metallic inclusions content was higher.Large size inclusions were found at the cracks of the rolled material,and a large number of large-sized inclusions were found near 1/4 width to the edge of rolled material,the composition of the inclusions was similar to that of the continuous casting mold powder.Large inclusions cause stress concentration during cold heading,which leads to and aggravates cold heading cracking.At the same time,improper control of rolling process causing the folding defects on the product surface and further 180 °symmetrical longitudinal cracks,is the main reason for cold heading cracking.