Steel for metal-cutting tools

Abstract

A steel for metal-cutting tools comprising carbon, chromium, molybdenum, vanadium, aluminum and nitrogen in certain concentration ranges. This Abstract is not intended to define the invention disclosed in the specification, nor intended to limit the scope of the invention in any way.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority under 35 U.S.C. §119 of Austrian Patent Application No. A 965 / 2003, filed on Jun. 23, 2003, the disclosure of which is expressly incorporated by reference herein in its entirety. BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a steel for metal-cutting tools. 2. Discussion of Background Information Cutting areas of tools are essentially highly stressed thermally, abrasively and in terms of toughness and compressive stress during a metal cutting of workpieces, and the stressing of the workpiece material takes place simultaneously. Alloy compositions which that take into account the highest demands in the stress profile to achieve the longest service life of the tool are known. High wear resistance of a tool can be achieved in general with the use of high-speed steels, but these have high contents of the expensive alloying element(s) molybdenum and / or tungsten in concen...

AI Technical Summary

Benefits of technology

Advantages achieved with the invention may include that a favorable hot hardness and, in particular, a high wear resistance with adequate toughness and compressive stress resistance of the heat-treated steel can be achieved by a combination of the elements molybdenum and vanadium on the one hand, in a considerably reduced concentration compared with high-speed steel, and with aluminum and nitrogen contents on the other hand, in relatively high contents compared to the prior art. Metal-cutting tools made of the alloy according to the invention can be produced cost-effectively due to the low contents of expensive alloying elements, but they also have high stability in the stress profile, particularly for exceptional requirements.

It has been found that the flow of chips on the face or in the area after the cutting edge of a tool made from the steel according to the invention takes place in a more favorable manner and there are comparatively far fewer craters. The reason for this has not yet been scientifically explained, but without wishing to be bound to any theory, it is assumed that it may be due to a synergistic effect of the elements aluminum, nitrogen, carbon and vanadium. The high affinity of vanadium toward carbon and nitrogen which on the one hand advantageously affords a high hot hardness with the formation of very fine, homogenously distributed carbides and carbonitrides during heat-treatment, can on the other hand leave an adequate amount of reactive aluminum in the matrix. Under temperature stress, the aluminum forms an alumina surface layer through oxidation in the cutting area of the tool, which alumina acts like a coating which promotes the flow of chips. Aluminum in the matrix has also proven to promote a hot hardness and retention of hardness of the material according to the invention.

When the ratio of aluminum to nitrogen is from about 0.5 to about 1.9 (Al / N=about 0.5 to about 1.9), the material according to the invention has a high hot hardness and toughness in the heat-treated state or after a hardening and at least a single tempering operation in the range from about 450° C. to about 500° C., whereby the cutting wear on the tool is extremely low.

Circular saws with a hardness of greater than about 63 HRC, preferably greater than about 64 HRC, can be produced from a steel according to the invention with particular cost-effectiveness and with a long service life in heavy operation.

Problems solved by technology

High wear resistance of a tool can be achieved in general with the use of high-speed steels, but these have high contents of the expensive alloying element(s) molybdenum and / or tungsten in concentrations up to 20% by weight.

As set forth above, the compositions of high-speed steels can be selected for a required stress profile of the tool, but these steels have the disadvantage of high alloying costs and therefore high material costs.

If the concentrations of the main alloying elements are reduced for reasons of economy, the heat-treatable quality, the hardness and the general performance characteristics of the steel may deteriorate abruptly.