Optimization of 488 mm Series Pass of Cone Type Piercer

In order to solve the problems as staying with the 488 mm series pass of the piercer of the Φ460 mm PQF mandrel pipe mill，i.e.，high expansion rate，serious shell inner surface spiral defect，and irregular tail end，etc.，countermeasures are taken，including replacing the Φ400 mm billet with the Φ450 mm billet，changing the angle of the roll inlet cone first section from 2.5° into 3° via optimizing the piercing roll，and optimizing the dimensional design of the guide shoe and the plug via determining empirical parameters based on theoretic data and actual production experiences， and then performing production verification. Relevant practice shows that owing to optimized design of the 488 mm series pass，the design of the rolling tools of the piercer is more reasonable，the piercing process is more consistent，the dimensional accuracy and the outer and inner surface quality of the shell are significantly improved，having met the requirements for the PQF manufacturing process.