Plug and Method of Manufacturing the Same
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.