Plug and Method of Manufacturing the Same

Abstract

A plug that achieves prevention of peel-off of the coating and a method of manufacturing such a plug are provided. A plug ( 10 ) is used for piercing a billet. The plug ( 10 ) includes a plug body ( 1 ), a body coating ( 2 ), and a surface-layer coating ( 3 ). The body coating ( 2 ) is provided on a surface of the plug body. The body coating ( 2 ) contains iron and iron oxides. The surface-layer coating ( 3 ) is provided on the body coating ( 2 ). The surface-layer coating ( 3 ) contains iron and iron oxides. The surface-layer coating ( 3 ) has a porosity lower than that of a region of the body coating ( 2 ) adjacent to the surface-layer coating ( 3 ) and having a thickness equal to that of the surface-layer coating ( 3 ).

1 . A plug used for piercing a billet, comprising:
 a plug body;   a body coating provided on a surface of the plug body and containing iron and iron oxides; and   a surface-layer coating provided on the body coating and containing iron and iron oxides,   wherein the surface-layer coating has a porosity lower than that of a region of the body coating adjacent to the surface-layer coating and having a thickness equal to that of the surface-layer coating.   
     
     
         2 . The plug according to  claim 1 , wherein the porosity of the surface-layer coating is not higher than 2.5%. 
     
     
         3 . The plug according to  claim 1 , wherein the thickness of the surface-layer coating is not larger than 250 μm. 
     
     
         4 . A method of manufacturing a plug used for piercing a billet, comprising:
 preparing a plug body;   forming a body coating on a surface of the plug body by performing arc spraying using iron wire; and   forming a surface-layer coating on the body coating by performing arc spraying using iron wire at a spray distance shorter than that at completion of the formation of the body coating.   
     
     
         5 . The method of manufacturing a plug according to  claim 4 , wherein the forming the body coating performs arc spraying while the spray distance is gradually increased.