Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Patent
1990-10-19
1993-02-16
Walsh, Donald P.
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
75240, 428560, 428551, 428553, 408144, 761086, 76DIG11, 407119, B22F 500, B22F 706, B23B 2714
Patent
active
051867397
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a high-quality cermet alloy containing nitrogen which has an excellent wear resistance and toughness and is capable of withstanding high-speed cutting. The invention also relates to a drill which is formed of such a cermet alloy. The term "drill" as used herein refers to a drill bit.
Background Information
A drill is a cutting tool which is employed for drilling holes into a workpiece of steel or the like. FIG. 1 shows the structure of a twist drill by way of example. The twist drill generally comprises a head portion 1 which is adapted to cutting, and a shank portion 2 which is not much concerned with the cutting but is mainly adapted to discharge chips as well as to mount the drill in a chuck of a cutting machine such as a drilling machine.
In a working condition, the head portion and the shank portion of a drill are subject to different conditions. Therefore, characteristics required for the respective portions of the drill are different from each other. For example, wear resistance and deposition resistance etc. are required for a cutting edge part of the head portion, while toughness for maintaining strength of the tool is required for the shank portion. Also, different portions of the cutting edge part of the head portion must have different characteristics because the central cutting edge portion and the outer peripheral cutting edge portion are subject to vary different in cutting speeds. In order to satisfy such complicated requirements, various materials have hitherto been developed for drills.
Up to this time, general materials for drills are high-speed steel and cemented carbide. High-speed steel, which is superior in toughness but inferior in wear resistance, is improper for high-speed cutting. On the other hand, cemented carbide, which has an excellent wear resistance and cutting accuracy but is brittle, may be bent when used in a machine tool having low rigidity, for example.
In order to improve the above situation, a drill structure with a head portion of high-speed steel coated with hard TiN, or a structure with a head portion made of cemented carbide and brazing the same has been considered. However, the head portion subjected to coating has had such a disadvantage that a coating layer of at least its front flank side is removed when regrinding of the drill and the greater part of the effect of coating is lost. Further, the structure formed by brazing the head portion with cemented carbide has had such a disadvantage that the same cannot be used for cutting a hard to cut material; nor for deep hole drilling since brazing itself is essentially inferior in thermal strength and mechanical strength.
In recent years there have been proposed a structure of brazing different materials (P30 and D30) of cemented carbide, see Japanese Utility Model Laying-Open No. 58-143115, and a structure of metallurgically integrating or joining the same, see Japanese Utility Model Publication No. 62-46489 for attaining improvements in wear resistance and toughness. The difference between characteristics required for a central part and an outer peripheral part of a drill and making materials of cemented carbide for the central part and for the outer peripheral part to differ from each other to form a double structure, have been described in Japanese Patent Laying-Open No. 62-218010. Methods of forming this double structure by injection molding have been described in Japanese Patent Laying-Open Nos. 63-38501 and 38502. In addition, preparing the material for a drill from cermet, in order to improve the deposition resistance of the drill is described in Japanese Patent Laying-Open No. 62-292307 or the like. In these conventional examples, those preparing cemented carbide from coarse grains and bringing the same into strong binder phases for the purpose of improving the toughness of the shank portions of the drills, have unintendedly reduced strength of the materials or are subject to elastic change or distortion, which cause such a problem that the drills
Isobe Kazutaka
Nomura Toshio
Fasse W. G.
Jenkins Daniel
Kane, Jr. D. H.
Sumitomo Electric Industries Ltd.
Walsh Donald P.
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