Patent ID: 9333544
Filing Date: 2016-05-10
CPC Classification: B05D,B21B,C23C

Claim Text:
1. A piercing machine for piercing-rolling a billet, the piercing machine comprising: a plug; a mandrel having a front end, the plug being attached to the front end; and a pair of skew rolls located opposite to each other, the plug being located between the skew rolls; the plug comprising: a plug body; a build-up layer formed on a surface of the plug body, the build-up layer located at least in an area between a front end portion of the plug body and a position 3 cm backward of a position opposite to a portion at which a spacing between the pair of skew rolls is shortest; and a sprayed film covering at least an area ranging from a rear end of the build-up layer to a position of a maximum outer diameter of the plug body.