| 摘要 |
PURPOSE: To prevent seizing in hot working for the material to be worked constituted of a hard-to-work material such as pure Ti, Ti alloys, and martensitic, austenitic and duplex stainless steels and to prolong the service life of a tool. CONSTITUTION: On the surface of the base material of a tool, a metal-carbide composite coating film contg., by volume, 20 to 70% niobium carbide grains and an oxide coating film uniformly formed on the topmost surface of the same film are formed. The thickness of the same oxide coating film is preferably regulated to >=20μm. Since seizing at the inside face of a plug and a pipe stock can be prevented even in plug mill rolling not only for carbon steel and low alloy steel but also for a hard-to-work material such a pure Ti, Ti alloys and stainless steel, the pipe stock free from inside flaws can be produced, and moreover, the service life of the plug is remarkably prolonged. Moreover, the service lives of a die for pipe edge upset working and a mandrel are remarkably prolonged.
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