Optimization of Heavy-wall Pipe Pass of Slight-stretch Sizing(Reducing)Mill

Described in the article are the activities for optimization of the slight-stretch sizing(reducing)mill in a bid to improving the steel tube dimensional accuracy. Addressing the problem that when rolling heavy-wall pipes with wall thickness over 10 mm by using the passes of the slight-stretch sizing(reducing)mill of the Φ159 mm and Φ177 mm mandrel pipe milllines,out-of-tolerance wall thickness and serious “hexagonal bore”occur with the pipe,the pass is optimized as a negatively-broadsided one. And the OD and WT of the pipe as rolled with the said optimized pass are measured to verify the optimization effectiveness. The verification result shows that owing to the optimized pass,both the OD and WT accuracies of the heavy-wall steel pipe are improved,and the trend of the OD out-of roundness and“hexagonal bore”are alleviated.