优质碳素结构钢盘条拉拔缺陷原因分析

Cause analysis on drawing defects of high-quality carbon structural steel wire rod

针对70和80优质碳素结构钢在拉拔过程中盘条上出现的斜坡状断裂、笔尖状断裂、飞皮和掉肉缺陷等问题,通过检测盘条的金相组织、硬度和非金属夹杂物,对这些缺陷产生的原因进行了研究。结果表明,铸坯局部表层夹渣是拉拔过程中盘条表面出现飞皮和掉肉缺陷的主要原因,部分飞皮脱落后会在盘条表面留下凹坑从而形成掉肉缺陷;以SiO_2为主的大颗粒夹杂物会严重破坏盘条基体的连续性,导致盘条在拉拔过程中发生笔尖状断裂;拉拔工艺不当会导致盘条产生表面缺陷从而引起斜坡状断裂。

In order to avoid drawing defects of general fracture, pen-tip shaped fracture, decrustation and scallop in drawing process of wire rods for high-quality carbon structural steel, i.e. 70 and 80 steel in the present work, optical mi- crostructures, Vickers hardness and non-metallic inclusions were detected to investigate the causes of the drawing de- fects. The results show that slag inclusions at local surface of steel billet generate the defects of decrustation and scallop, and the latter is transformed from the former. On the other hand, SiO2-based inclusions with large size produced by reox- idation of liquid steel in continuous casting process lead to the destruction of steel matrix and the pen-tip shaped fracture. Additionally, surface defects induced by unreasonable drawing process are the key reason for general fracture.