Steel alloy for gliding elements

Details Steel alloy for gliding elements Steel alloy for gliding elements

1999-02-25

2001-05-22

Yee, Deborah (Department: 1742)

Alloys or metallic compositions

Ferrous

Nine percent or more chromium containing

C420S069000

Reexamination Certificate

active

06235237

ABSTRACT:

The invention relates to a material for gliding elements of sports equipment, in particular for gliding edges of winter sports equipment such as, for example, skis, skibobs and toboggans.
Such materials are subject to extremely diverse stresses; they require high surface quality, in particular high glidability and high wear resistance, overall stability and corrosion resistance and a low tendency to vibration or good damping properties.
A high wear resistance and corrosion resistance reduce the need for regrinding the edges, whereas the straight-line property and/or distortion resistance is of decisive importance when fitting the edges to, for example, the ski. Finally materials for gliding elements and gliding edges require good workability, in particular a good deformation behavior, so that they can be economically produced by rolling or drawing.
For the production of ski edges having an L-shaped cross section by rolling or drawing, German Offenlegungsschrift 2,204,270 proposes the use of a quenchable and temperable steel, whose use properties are adjusted after the quenching and tempering by a special heat treatment. This heat treatment consists of a pearlitization of the flank embedded in situ into the body of the ski underneath the gliding surface, while retaining the martensitic head. To achieve this, heating of the flank to a temperature above the annealing temperature and simultaneous cooling of the head are necessary. In this way, a ski edge head having a high hardness and a relatively soft flank results, which ensures a correspondingly low tool wear during the subsequent stamping-out of recesses.
This heat treatment involves, however, the disadvantage that, as a consequence of the one-sided heating, curvatures, that is to say so-called sickle deviations, occur and this is to be ascribed to a volume contraction during the conversion of the originally martensitic microstructure of the profile flank into the pearlitic state.
In order to avoid the occurrence of sickle deviations, German Offenlegungsschrift 4,218,099 limits the deviation in the Rockwell hardness over the cross section and over the length of the ski edge profile in the hardened and annealed state to less than 2 HRC and, for the pearlitization, prescribes a uniform heat input and, after the pearlitization, deforming of the heat-treated edge profile by bending. The deformation by bending is intended to stretch the flank uniformly, in order to eliminate in this way the curvatures resulting from the partial heat treatment.
The abovementioned process is extremely expensive and frequently does not achieve the desired effect, because it is extremely difficult to achieve the required uniformity of the hardness across the width and length of the profile and a uniform degree of bending stretching over the length of the flank. Furthermore, the quenching and tempering steels being used are not corrosion resistant and therefore require frequent regrinding.
In a process known from German Offenlegungsschrift 4,000,744 for the heat treatment in situ, the ski edge is austenitized by means of a laser beam at temperatures above 700° C., and the austenite is transformed into martensite during cooling. The in-situ heating requires, however, careful cooling of the body of the ski which in most cases consists of plastic and is glued, for example laminated. For this purpose, copper wheels running alongside during the austenitization are used for removing the heat in the edge/body region. This also involves difficulties because, in spite of the heat removal, it is not suitable for every plastic or adhesive for the production of skis, because of the remaining residual quantities of heat. Moreover, the stability of the microstructure is relatively low and internal strains which can be the cause of edge break-outs under lateral impact stress, and distortion can occur.
Furthermore, Swiss patent specification 682,492 proposes the use of a wire using a nitride layer which, in the course of a subsequent deformation, is adjusted to an austenitic microstructure and finally heat-treated. When the wire is transformed into the edge profile, the thickness of the nitride layer decreases and there is a risk of the remaining thickness being too small and the layer tearing apart locally.


REFERENCES:
patent: 3595643 (1971-07-01), Boyce et al.
patent: 5714114 (1998-02-01), Uehara
patent: 53-103918 (1978-09-01), None
patent: 9/6580 (1982-03-01), None

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