SEAMLESS PIPE PIERCE-ROLLING PLUG, SEAMLESS PIPE PRODUCING DEVICE AND SEAMLESS PIPE PRODUCING METHOD USING THEM

摘要

A plug to be used such that the front and rear sections of a split plug are held as an integral plug, specifically a seamless pipe pierce-rolling plug wherein at least the front is made of low alloy steel, the front and rear sections having oxide films formed on their surfaces; and a method of producing seamless pipes by using an inclined roll type pierce-rolling machine using the plug as a piercing tool to effect pierce-rolling. Further, a seamless pipe producing device in which the front and rear sections are held as an integral plug, one or both of them being removably mounted, and a core holding the plug extends through the rear section to be connected to the front section; and a seamless pipe producing method using the production device, with one or both being replaceable in a production line. The thickness of the oxide film formed on the front section is 200 mum or above, being preferably greater than that of the oxide film formed on the rear section. Even in the case of the pierce-rolling of a hard-to-process material, it is possible to prevent eruption flaw or inner surface flaw and to achieve excellent plug life and reduced plug requirements.