Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Patent
1989-09-07
1990-06-26
Lechert, Jr., Stephen J.
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
75239, 75241, 75246, C22C 2904
Patent
active
049369113
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a cold work steel, i.e. a tool steel intended for use near room temperature, in the first place for cutting and punching metallic materials but also for plastically forming cold working operations, as for example for deep-drawing tools and for cold-rolling rollers. The invention also relates to a method of manufacturing the steel utilizing powder-metallurgy including the consolidation of metal powder to a dense body. The steel is inter alia characterized by a very high impact strength in combination with an extremely good wear resistance, which makes the steel very useful for punching and cutting tools.
BACKGROUND OF THE INVENTION
Cold work steels for cutting, punching or forming metallic materials shall fulfil a number of demands which are difficult to combine. Particularly high demands are raised upon the impact strength, especially when the tool is intended for cutting or punching adhesive materials (adhesive wear), as for example austenitic stainless steels. Further, the tool material must not be too expensive, which limits the possibility of choosing high contents of expensive alloying components.
Conventional cold work steels are well qualified in the above mentioned respects. Nevertheless, it is, however, desirable to obtain tool materials having still better features. Therefore, in some cases, there have been used powder-metallurgically manufactured high speed steels, i.e. steels which are characterized by high contents of tungsten and/or molybdenum and usually also cobalt. High speed steels, however, are expensive. Therefore, it is desirable to obtain a cold work steel without using such expensive alloying elements as tungsten and/or cobalt, at least not high contents of said elements, but nevertheless a steel having cold working features which are comparable with or better than what is achieved by means of high speed steels made through the powder-metallurgical manufacturing technique.
The wear resistance of steels can also be improved by providing the steel object with a thin coating of a very wear resistant material. Particularly, the so called CVD-technique (CVD=Chemical Vapour Deposition) gives a very wear resistant surface layer and as a matter of fact it is the most efficient method known and available today for improving the wear resistance. Unfortunately, the method also have some drawbacks which often render it impossible to use; it can be utilized only for the coating of comparatively small objects; the siz tolerances cannot be adjusted to any greater extent after the application of the CVD-coating; and it is very expensive.
BRIEF DISCLOSURE OF THE INVENTION
With reference to the above mentioned background it is an object of the invention to provide a new, powder-metallurgically produced cold work steel with a wear resistance and a toughness which is better than or comparable with that of powder-metallurgically produced high speed steels and having a combination of toughness and wear resistance better than that of conventional, high alloyed cold work steels. As far as the wear resistance is concerned, it is also a specific object of the invention to bring about a wear resistance which is comparable with that of CVD-coated, powder-metallurgically produced steels having a similar content of alloying elements. The steel shall, in order to achieve the above mentioned objects, contain 0.5-2.5% C, 0.1-2% Si, 0.1-2% Mn, 0.5-1.5% N, max 15% Cr, preferably 6.5-11% Cr, max 4% Mo, max 1% W, 3-15% V, wherein up to half the amount of vanadium can be replaced by 1.5 times as much niobium, and part of the vanadium can be replaced by titanium at a content up to four times the content of nitrogen and the double amount of zirconium at a content up to eight times the content of nitrogen, and wherein the ratio V/(C+N) shall amount to not less than 2.5 and not more than 3.8, balance essentially only iron, impurities and accessory elements in normal quantities. The total content of carbides, nitrides and carbonitrides amounts to between 5 and 20 volume-%, pref
REFERENCES:
patent: 4121929 (1978-10-01), Kawai et al.
patent: 4121930 (1978-10-01), Yukawa et al.
patent: 4780139 (1988-10-01), Hellman et al.
patent: 4863515 (1989-09-01), Roberts et al.
Johansson Borje
Roberts William
Bhat Nina
Lechert Jr. Stephen J.
Uddeholm Tooling Aktiebolag
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