TMK Research Center (Moscow, Russia)

D. V. Mikhalkin, Head of the Screw Rolling Laboratory, dmitriy.mikhalkin@tmk-group.com
E. V. Alyutina, Junior Researcher, Screw Rolling Laboratory, ekaterina.alyutina@tmk-group.com
A. A. Korsakov, Cand. Eng., Head of the Seamless Tube Dept., andrey.korsakov@tmk-group.com
D. A. Balakin, Junior Researcher, Screw Rolling Laboratory, BalakinDA@tmk-group.com

This article discusses the pressing issue of increasing the durability of piercing mill plugs, which are a critical element of the screw rolling process. The focus is on a little-studied aspect: the influence of plug sizing on its wear and service life. Various sizing types and working surface types of plugs (spherical, convex/concave, conical, and with special profiling) are analyzed. The key idea of the study is to compare the nature and magnitude of plug wear with the distribution of partial deformation rates (PDRs) of the rough tube across the piercing mill’s roll pass and evaluate their impact on durability. The authors divided the deformation zone into two sections (rolling of a solid billet and plug rolling) and calculated the PDRs. The results showed that maximum plug wear corresponds to maximum PDR values, and using a plug with a specially profiled working surface reduces the maximum PDR value and shifts it toward the more massive and wear-resistant calibration section of the plug. Thus, it was demonstrated that changing the calibration of the plug’s working surface is the most controllable parameter for optimizing the piercing process. Using four plug variants (classic, with a reduced nose diameter, with a conical and specially profiled working surface), the influence of the profile on the PDRs distribution was demonstrated. It was concluded that plug durability increases with a decrease in the maximum PDR value, a wider PDRs distribution area, and a shift in the peak deformation toward the massive part of the plug. To confirm the identified relationships, further research is planned, including computer modeling and industrial testing.

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