Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Patent
1998-04-16
2000-01-18
Mai, Ngoclan
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
75246, 419 11, 419 49, C22C 3300
Patent
active
060154462
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
It has been known for a long time that powder-metallurgically produced steels have characteristics which are superior to those of an identical composition of melt-metallurgically produced steels. In particular, powder-metallurgically produced steels are characterized by the feature that in all dimensional ranges they exhibit the same microstructural state over their whole cross-section. Hence, the mechanical characteristics are substantially the same over the whole cross-section.
It has already been known that the hot-work steel X40CrMoV51 is produced in a powder-metallurgical process by hot isostatic pressing. As can be gathered from the "Archiv fur das Eisenhuttenwesen" ("Archives for Iron Metallurgy") 55 (1984), pages 169-176, the said hot-work steel contains carbon of 0.37 to 0.41%, silicon of 1.0 to 1.07%, manganese of 0.38 to 0.42%, chromium of 5.3 to 5.5%, molybdenum of 1.37 to 1.41%, vanadium of 1.0 to 1.27% and negligible amounts of nitrogen, oxygen, sulfur and phosphorus.
A powder of the above-stated composition, which has been produced by nitrogen atomization from the melt, is compacted in steel capsules which, prior to being closed, are evacuated to a vacuum of less than 10.sup.-4 mbar. Compacting is carried out at temperatures of from 1075.degree. C. to 1225.degree. C.
Although the above-mentioned powder-metallurgically produced hot-work steel has an adequate hardness, it is not suited for highly stressed hot-work tools, such as pressing mandrels, pressing dies and containers for metal-tube extrusion or for extrusion, nor for hot extrusion tools, tools for making hollow bodies, tools for screw, nut, rivet and bolt products, die-casting tools, press dies for shaped parts, die inserts or hot shear blades because of its insufficient hot hardness and its lack of good tempering properties and because of its tendency to cracking caused by temperature changes. In short, the stability of the steel in question is not satisfactory in the case of highly stressed hot-work tools.
It is therefore the object of the present invention to provide a powder-metallurgically produced hot-work steel which, apart from a sufficient degree of toughness, has a high hot hardness and, in particular, a high resistance to cracking caused by temperature changes. To be more specific, it is the object of the present invention to provide a powder-metallurgically produced hot-work steel which is particularly suited for use in extrusion processes, in particular for pressing mandrels, pressing dies and containers, and is also suited for use in forging presses and die-casting dies, particularly in the case of large dimensions.
Furthermore, it is the object of the invention to provide a method of producing an improved powder-metallurgically produced hot-work steel.
As for the steel to be produced, this object is achieved by the subject matter of claim 1. As for the method to be created, this object is achieved by the subject matter of claim 5.
Furthermore, the invention relates to the use of the powder-metallurgically produced hot-work steel as a material for producing pressing mandrels, pressing dies and containers for extrusion and for producing forging presses and die-casting dies.
The technical progress which can be achieved with the aid of the invention is primarily due to the fact that as a consequence of the inventive cobalt-containing composition, synergetically enhanced by the special compaction according to the invention, a powder-metallurgically produced hot-work steel is provided which essentially has the same good hot-ductility characteristics as a known cobalt-free hot-work steel, but, in addition, has high hot-hardness and temper values, as well as high resistance values regarding fire check.
Among the experts, there are strong objections to the inclusion of cobalt in a hot-work steel. To be more specific, there prevails the idea among the experts that the addition of cobalt to an alloy will certainly not yield or even improve the toughness characteristics, in particular hot ductility characteristics, of a
REFERENCES:
patent: 4923671 (1990-05-01), Aslund
patent: 5435824 (1995-07-01), Dorsch et al.
patent: 5435827 (1995-07-01), Wisell
patent: 5447800 (1995-09-01), Dorsch et al.
patent: 5522914 (1996-06-01), Stasko et al.
Wegst C.W. "Stahlschluessel" 1989, Stahlschlussel, Nachschlagewerk, NR. ED. 1989, pp. 237/238, 242, Wegst C W XP002019003.
Hanspeter Hau
Mai Ngoclan
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