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:
Nov. 30, 1999
Filed:
May. 21, 1997
Tomonori Niwa, Aichi, JP;
NGK Spark Plug Co., Ltd., Aichi, JP;
Abstract
A sintered alumina-based ceramic has a relative density of equal to or higher than 95%, an average grain size in a range of 10-25 .mu.m and a fracture toughness Kc equal to or lower than 3.0 MPam.sup.1/2 Furthermore. In a machinability evaluation test using a surface grinder, the ceramic exhibits equal to or less than 310 W of increase in the load on a motor rotating a grinding wheel of the surface grinder. The machinability evaluation test is performed under the following condition. (1) The dimension of a test piece of the sintered alumina-based ceramic is larger than 15 mm in width, larger than 30 mm in length and larger than 10 mm in height. (2) The test piece is fixed on a table of said surface grinder and ground by the grinding wheel along a direction of its length. (3) The grinding wheel has a dimension of 10 mm in width and 200 mm in outer diameter, and consists of synthetic (or artificial) diamond abrasive grains more than 80 wt % of which are in a grain size range of 74-88 .mu.m, and which are resin-bonded at 3.3 cts/cm.sup.3 of weight content per unit volume. (4) The circumferrential speed of said grinding wheel is 2400 m/min, the table traversing speed is 60 mm/min, and the infeed per traverse is 3 mm.