Method of producing plug for piercing-rolling

Abstract

A method for producing a plug for use in a piercing rolling mill for producing a seamless steel tube/pipe includes an arc-spraying step of melting iron wires, and spraying molten material thereof onto a surface of a base metal of a plug by use of an arc-spray gun, so as to form a film containing oxide and Fe on the surface of the base metal of the plug. In the arc-spraying step, the surface of the base metal of the plug is divided into plural sections along an axial direction of the plug, and in turn, the arc-spraying is separately carried out in each of the plural sections while an intersection angle between the center line of a spraying stream from the arc-spray gun and the surface of the plug base metal is maintained within a range of 35 degrees to 90 degrees.

What is claimed is: 
     
         1 . A method for producing a plug for use in a piercing-rolling mill for producing a seamless steel tube/pipe, the method comprising:
 an arc-spraying step of melting iron wires, and spraying molten material thereof onto a surface of a base metal of a plug by use of an arc-spray gun, so as to form a film containing oxide and Fe on the surface of the base metal of the plug, wherein   in the arc-spraying step, the surface of the base metal of the plug is divided into plural sections along an axial direction of the plug, and in turn, the arc-spraying is separately carried out in each of the plural sections while an intersection angle between the center line of a spraying stream from the arc-spray gun and the surface of the plug base metal is maintained within a range of 35 degrees to 90 degrees.   
     
     
         2 . The method for producing a plug for piercing-rolling according to  claim 1 , wherein
 the plug has a bullet shape, and includes a body portion and a tip end portion, while   the plural sections comprise a region of the body portion and a region of the tip end portion.