Method for producing seamless steel tube/pipe

Abstract

When performing piercing-rolling by use of a plug with a protection film on its surface, applying a lubricant made of an aqueous solution containing a total of 5 to 30% mass % of one or more of boron oxide, boric acid, and amine borate to the protection film on the plug surface, and using this plug for piercing-rolling makes it possible to realize the increase of the life of plug for piecing-rolling without reducing the efficiency of piercing-rolling. The plug can be cooled after the piecing-rolling, the application of the above described lubricant is performed when the surface temperature of the front edge of plug decreases to 100° C. or less, and the plug is reused for the piercing-rolling. In this occasion, the protection film on the plug . surface can be formed by arc spraying iron wire material onto the surface of the base metal of plug, and comprises oxides and Fe.

1 . A method for producing a seamless steel tube/pipe in which piercing-rolling is performed by using a plug with a protection film on a surface thereof, comprising:
 applying a lubricant made of an aqueous solution containing a total of 5 to 30 mass % of one or more of boron oxide, boric acid, and amine borate to the protection film of the plug for use in the piercing-rolling.   
     
     
         2 . The method for producing a seamless steel tube/pipe according to  claim 1 , wherein
 the plug is cooled after piercing-rolling, the lubricant is applied when the surface temperature of the front edge of plug decreases to 100° C. or less, and the plug is reused for the piercing-rolling.   
     
     
         3 . The method for producing a seamless steel tube/pipe according to  claim 1 , wherein
 the protection film is formed by arc-spraying iron wire material on the surface of the base metal of plug, and comprises oxides and Fe.   
     
     
         4 . The method for producing a seamless steel tube/pipe according to  claim 2 , wherein
 the protection film is formed by arc-spraying iron wire material on the surface of the base metal of plug, and comprises oxides and Fe.