The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 16, 1991
Filed:
Feb. 28, 1990
Applicant:
Inventors:
Akira Takase, Tokyo, JP;
Takashi Tamura, Tokyo, JP;
Tsuneo Oikawa, Tokyo, JP;
Yutaka Mihara, Tokyo, JP;
Tomoyuki Hirakawa, Tokyo, JP;
Takeshi Kuwano, Tokyo, JP;
Assignee:
NKK Corporation, Tokyo, JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
B21B / ;
U.S. Cl.
CPC ...
72 97 ; 72209 ;
Abstract
A plug for manufacturing a seamless steel pipe is disclosed. The plug includes the surface layer made of molybdenum or molybdenum base alloy coming in contact with a workpiece to be drilled and the core covered with the surface layer. The surface of the core being in contact with the surface layer is formed uneven. According to the invention, the surface layer and the core are strongly joined together, and the life of the plug is elongated.