Failure Analysis and Surface Modification of Cold-drawing Dies for Precision Seamless Steel Pipe

Analyzed here in the paper is the failure of the cold-drawing inner dies for the precision seamless steel pipe.Also studied are the wear performance and wear mechanism of the Cr-plated and plasma-nitrided Cr12MoV die.Relevant production application result shows that micro-ploughing wear and adhesive wear act as the main causes for failure of the Cr-plated die;the plasma-nitrided Cr12MoV alloy die has a nitrided layer about 0.23 mm thick,and has high surface precision,and its hardness and friction wear characteristics are better than those of the Cr-plated Cr12MoV alloy die.therefore when ploughing characteristic occurs during the wear process,no surface peeling of the die is caused;and due to its high shape accuracy(i.e.,the roundness),the plasma-nitrided die has a service span as longer than that of the Cr plated one by about 50%.