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:
Apr. 23, 1991
Filed:
Dec. 28, 1989
Applicant:
Inventors:
Hironori Yoshimura, Tokyo, JP;
Inada Shyogo, Tokyo, JP;
Assignee:
Mitsubishi Metal Corporation, Tokyo, JP;
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
C22C / ;
U.S. Cl.
CPC ...
75240 ; 419 18 ; 428552 ; 428457 ; 428220 ; 51307 ; 407119 ;
Abstract
A microdrill bit is made of a tungsten carbide based cemented carbide which contains a binder phase of 6% by weight to 14% by weight of a cobalt alloy and a hard dispersed phase of balance tungsten carbide. The cobalt alloy contains cobalt, chromium, vanadium and tungsten and has weight ratios so as to satisfy the relationships of 0.04.ltoreq.(c+d)/(a+b+c+d).ltoreq.0.10 and 0.50.ltoreq.c/(c+d).ltoreq.0.95, where a, b, c and d denote weight ratios of tungsten, cobalt, chromium and vanadium, respectively. The drill bit is formed so as to have a Rockwell A scale hardness of 92.0 to 94.0.