Method for 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 a step of carrying out shotblasting on a surface of the plug, and an arc-spraying step of performing arc-spraying of a spray wire to form a film on a surface of a base metal of the plug to which the shotblasting is applied. In the arc-spraying step, arc-spraying uses a cored wire whose iron sheath tube is filled with at least low-thermal conductive particles like ZrO 2 particles, which have lower thermal conductivity than that of iron oxide among iron particles and low-thermal conductive particles, to form the film containing iron oxide, Fe and low-thermal conductive material. The formed film has enhanced insulation performance to produce the plug capable of ensuring the steady enhancement of the durability life of the plug during the piercing-rolling.

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:
 shotblasting a surface of the plug; and   arc-spraying a spray wire so as to form a film on a surface of a base metal of the plug that is shotblasted, wherein   in the arc-spraying step, the arc-spraying is carried out by using, as the spray wire, a cored wire whose iron sheath tube is charged with at least specific particles that contribute to enhancement of the durability life of the plug among iron particles and the specific particles, so as to form the film containing iron oxide, Fe and the specific particles.   
     
     
         2 . The method for producing a plug for piercing-rolling according to  claim 1 , wherein
 the specific particles are low-thermal conductive particles having lower thermal conductivity than that of the iron oxide.   
     
     
         3 . The method for producing a plug for piercing-rolling according to  claim 2 , wherein
 the low-thermal conductive particles are ZrO 2  particles.   
     
     
         4 . The method for producing a plug for piercing-rolling according to  claim 3 , wherein
 the proportion of the ZrO 2  particles in the cored wire is 2.5 to 30.0 volume %.   
     
     
         5 . The method for producing a plug for piercing-rolling according to  claim 1 , wherein
 the specific particles are solid lubricant particles.   
     
     
         6 . The method for producing a plug for piercing-rolling according to  claim 5 , wherein
 the solid lubricant particles are BN particles.   
     
     
         7 . The method for producing a plug for piercing-rolling according to  claim 6 , wherein
 the proportion of the BN particles in the cored wire is 5.0 to 20.0 volume %.