Use of a non-corrosive, martensitically hardening steel

Abstract

The aim of the invention is to produce mechanically driven rotary tools, preferably boring, milling, grinding and cutting tools which are stable, non-corrosive and biocompatible and also have high mechanical strength properties, in conjunction with good ductility properties. To this end, the invention relates to the use of a precipitation-hardenable, martensitic, stainless chromium-nickel steel having the following composition (in weight %): 10 to 14 of chromium; 7 to 11 nickel; 0.5 to 6 of molybdenum; 0.5 to 4 of copper; 0.05 to 0.55 of aluminium; 0.4 to 1.4 of titanium; up to 0.3 of carbon and nitrogen; less than 0.05 of sulphur; less than 0.05 of phosphorus; up to 0.5 of manganese; up to 0.5 of silicon; respectively up to 0.2 of tantalum, niobium, vanadium and wolfram; and optionally up to 9 of cobalt; optionally 0.0001 to 0.1 of boron; the reminder consisting of iron and common impurities.

Description

TECHNICAL FIELD [0001] The invention relates to a novel use for precipitation-hardenable, martensitic, stainless steels for the manufacture of rotary tools for applications with high requirements as regards a combination of high hardness and ductility as well as corrosion resistance, such as drilling, milling, grinding and cutting tools. BACKGROUND AND TECHNICAL PROBLEM POSED [0002] Precipitation-hardenable, martensitic, stainless steels are known from WO 93 / 07303. In this a composition of a stainless steel is described which has a very high strength with simultaneously good ductility. This steel is described as being particularly suitable for the manufacture of injection cannulae, dental instruments and medical instruments on the basis of wire and strip material produced from the named types of steel. Because of the high hardness of the steel, further working had to be restricted to a minimum. [0003] In WO 01 / 14601 A1 a process is described for the manufacture of parts with complic...

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Benefits of technology

[0025] As the corrosion results suggest that the material has a high corrosion resistance under both acid and alkaline application conditions, it is to be assumed tha

Problems solved by technology

Because of the high hardness of the steel, further working had to be restricted to a minimum.

The problem of workability was solved in this case with the help of the special manufacturing process, but this cannot be applied to tools, especially rotary tools with complicated geometry.

Because of this extreme length/diameter ratio and the resulting unfavourable moment distribution, such tools are very sensitive to the bending loads applied in practical use.

A slight bending, barely visible to the naked eye, of the drill can result in its generally running untrue and being unbalanced when next prepared by the operator or next used.

Because of the frequently very high rotation speeds this results, in practice, in the drill bits breaking off during operation.

This means not only that the drills have a short life and must frequently be replaced for reasons of safety, but also that there is a substantial risk of injury for operator, patient and bystanders who may be hit by flying parts of tools, as well as a substantial cost factor.

According to the Medical Products Law, tools with small dimensions in particular are designated disposable products by manufacturers, which represents an additional cost for the user.

After the tools have been used once their use on a second occasion is no longer allowed,

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