Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Patent
1994-02-04
1996-11-26
Mai, Ngoclan
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
75243, 75239, C22C 3500
Patent
active
055787738
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a high-speed steel with a new alloy composition. The steel is designed in the first place for the manufacture of tools having a high wear resistance. Particularly, the steel is intended for tools for cutting wood and paper, such as paper sheet cutting knives; powder dies and drifts, etc. Other conceivable applications are for wear parts, such as for details which are exposed to wear against roadways, for example tire studs and for other applications where the wear resistance is of primary importance, while the demands as far as toughness are concerned are more moderate.
For these applications there is today used a high-speed steel which is marketed under the trade name ASP.RTM. 23 (currently available from Erasteel Kloster Aktiebolag, a Swedish corporation), which has the nominal composition 1.29 C, 0.4 Si, 0.3 Mn, 4.0 Cr, 5.0 Mo, 6.2 W, 3.1 V, balance iron and impurities in normal amounts. Characteristic features of this steel are that it has a comparatively good wear resistance and a comparatively good toughness. However, there is a demand for tools having a still better wear resistance, whereas a certain reduction of the toughness can be tolerated. This particularly concerns objects of the type which are mentioned in the preamble. A steel which has a very high wear resistance is the steel which is marketed under the trade name ASP.RTM. 60 (currently available from Erasteel Kloster Speedsteel Aktiebolag, a Swedish corporation) and which has the nominal composition 2.30 C, 4.2 Cr, 7.0 Mo, 6.5 W, 10.5 Co, 6.5 V, balance iron and impurities in normal amounts. This steel is used for metal cutting tools and for cold work tools but is not suitable for the type of tools which are mentioned in the preamble; i.e., for tools intended for cutting paper and wood, etc. This type of tools often require a shape which is difficult to produce because the steel is difficult to machine, which in its turn depends on the limited toughness of the steel.
*ASP is a registered trade mark of Kloster Speedsteel Aktiebolag.
It is an object of the invention to provide a new high-speed steel which, better than steels used in the past satisfies the various requirements which are raised on steels for tools of the type mentioned in the preamble, and which requirements are difficult to combine.
Particularly, the invention aims at providing a high-speed steel having a wear resistance which is substantially better than that of the commercially available steel ASP.RTM. 23, and preferably as good or better than that of the commercially available steel ASP.RTM. 60 in combination with a very good toughness, which means that the toughness shall be substantially better than that of the commercially available steel ASP.RTM. 60 and preferably in the same order as that of the commercially available steel ASP.RTM. 23.
These and other objects may be achieved therein that the steel is characterized by what is stated in the appending claims.
In the following, the choice of the various alloy elements will be explained more in detail. Herein some theories will be made concerning the mechanisms which are considered to be the basis for the achieved effects. It should, however, be understood that the claimed patent protection is not bound to any particular theory.
DESCRIPTION OF THE INVENTION
Carbon is multifunctional in the steel of the invention. It forms MC-carbides, in the first place with vanadium, which carbides exist as undissolved primary carbides and as precipitation hardening secondary carbides. Further, carbon forms precipitation hardening M.sub.2 C-carbides in the first place with molybdenum and tungsten. The carbon content therefore in the first place is adapted to the contents of vanadium, molybdenum and tungsten for the formation of the said carbides, which also contain minor amounts of chromium, iron and manganese.
Therefore, the carbon content shall be at least 2.2%, preferably at least 2.25%, suitably at least 2.3%. On the other hand, the carbon content must not be so high th
REFERENCES:
patent: 4519839 (1985-05-01), Toyoaki et al.
patent: 4780139 (1988-10-01), Hellman et al.
patent: 4880461 (1989-11-01), Uchida
patent: 4936911 (1990-06-01), Roberts et al.
patent: 4964908 (1990-10-01), Greetham
Bednarek Michael D.
Erasteel Kloster Aktiebolag
Mai Ngoclan
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