Effect of roll parameters on deformation process and inner folding in rotary tube piercing process
On view of the inner folding defect of 2Cr13 steel seamless tube in actual production of a steel pipe company,based on the determination of mechanical properties of 2Cr13 steel at high temperature,a three-dimensional elastoplastic finite element simulation of the existing process of the typical specification 2Cr13 steel rotary tube piercing process with the help of finite element software Simufact was analyzed,and the roll parameters were optimized.Furthermore,the influence of different roll entrance cone angle,entrance cone segment length,roll diameter and roll rotate speed on inner folding and secondary biting in rotary tube piercing was studied.The results show that the new roll is designed as a two-stage entry cone roll,that is,the first section length L11=170 mm,work cone angle β11=1.8°,the second section length L12=110 mm,work cone angle β12=3.2°.The maximum rolling force,plug axial force and guide shoe force decrease by 5.56％,3.89％and 20.55％,respectively,compared with the original roll when using the new design scheme roll in rotary tube piercing process,and the second bite is smooth,and the tendency of the rolled piece to produce inner folding is very small.When the diameter of the roll increases from 800 mm to 850 mm,the rolling force increases,the guide force decreases,which results in the axial resistance of the rolled piece decreases,which is beneficial to the second bite of the round bar and the stability of the piercing process,and the adjustment range of the reduction rate before plug is expanded.When the roll rotary speed increases from 56.4 r/min to 62 r/min,the outlet speed of the pierced shell increases,but the rolling torque increases which results in the energy consumption increases,the axial slip of rolled piece increases,so the axial speed efficiency decreases,and the tendency of inner folding of pierced shell increases.
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