φ60mm毛管凹坑缺陷成因分析及对策

穿后毛管或荒管在热轧定径过程中，由于定径工序相关参数不符合工艺要求，致使毛管头部外表面纵向780mm处产生一种类似于月牙形的凹坑缺陷。通过分析凹坑缺陷的产生原因，结合现场实践，采取减小定径辊辊缝，提高装配质量，严格控制定径工序总减径率和终轧温度，定期修复定径机标高等措施，消除了毛管的凹坑缺陷，为后续变形的冷加工提供了合格的毛管，有效提高了产品一次成材率。

Brief Analysis of Causes and Countermeasures of Pits in φ 60 mm Hollow Billet

When hollow billet or pierced billet are in the process of hot rolling sizing, due to the sizing parameters do not con- form to technical requirements, the crescent - shaped pit occurs at head which is 780 mm along the outer surface of hollow billet. By analyzing the cause of pit and combined with on site practice, the measurements like ： reducing the roll gap of sizing , improving the as- sembly quality, strictly controlling the total reducing rate and finishing temperature, regular repair elevation of sizing mill, are carried out to remove the defects of pit. Qualified hollow billet are used for the subsequent deformation of cold machining and effectively im- prove the primary product yield.