Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B37/00—Cases
  • G04B37/22—Materials or processes of manufacturing pocket watch or wrist watch cases

Definitions

• the invention relates to a corrosion-resistant and structurable alloy for use as a material for parts which are at least partially in contact with the skin of living beings, in particular humans, comprising essentially the components manganese, chromium and nitrogen, the rest iron. Furthermore, the invention is concerned with the use of a corrosion-resistant alloy as a material for, in particular, structured parts of clothing and / or for jewelry and articles of daily use which are at least partially in contact with the skin of living beings, in particular humans.
• the skin of living things can be hypersensitive when irritated by certain substances or rays. Such overreactions are called allergies, and even living beings of the same genus can show no or hypersensitive, possibly different intensity reactions to the same stimuli. Many substances are known to affect the skin of humans in particular, which may cause allergies.
• nickel allergy is particularly common. It was found that not only pure nickel but also alloys with a nickel concentration of a few percent can trigger an allergic reaction. Living things, especially humans, inevitably come into contact with metallic materials, especially stainless steels and alloys, which can contain nickel. Many everyday objects such as wristwatches, watch straps, eyeglass frames, fashion jewelry and the like. and parts of or on items of clothing, for example fasteners, trousers rivets of jeans and also parts on medical, possibly prosthetic support or holding devices to be worn on the body, are made of metallic materials in particular for reasons of the required material strength and the preferred material properties.
• the parts In order to achieve the rust resistance of the parts, which is required in particular for cleaning or storage, they can be coated, for example galvanically, optionally with chrome.
• the disadvantages of such coatings are high manufacturing costs and peeling caused by cracks in the layer. If a triggering of a nickel allergy is to be avoided with certainty, the classic rust-resistant steels with approx. 8 to 12 wt.% Nickel, such as DIN material No. 1.4401 and No. 1.4404, may not be used for parts that are at least partially in contact with the skin . Attempts have already been made to use nickel-free, rust-resistant chrome steels such as DIN material No. 1.4001 and No. 1.4016.
• a disadvantage of such materials is that, in the presence of sweat or salt solutions, cracks can be formed on the parts containing more than 12% by weight chromium to form a passivation layer on the surface in the presence of sweat or salt solutions, and so-called stress corrosion cracking, and / or a large manufacturing effort is required.
• chemical structuring of the surface of the parts with a desired similarity to achieve a special surface appearance as is often provided for watch straps, watch floors, eyeglass frames and the like, is usually not possible.
• stainless chrome steels can be magnetized, which excludes their use for housings from clocks that can be influenced in their function by magnetic fields. It is known that titanium does not cause any allergic reactions, so it is particularly well tolerated by living things. The high price and one often elaborate production of parts from titanium, however, represent significant disadvantages.
• the object of the invention is to eliminate the disadvantages of the known materials and to provide a corrosion-resistant and structurable alloy for use as a material for parts which are at least partially in contact with the skin of living beings, in particular humans, and which do not cause allergies, high strength possesses and has non-magnetic properties.
• This goal is achieved in the case of an alloy of the type mentioned at the outset in that this alloy in% by weight carbon Max. 0.10 silicon Max. 1.0 manganese 11.0 to 25.0 chrome 10.0 to 20.0 molybdenum up to 1.6 nitrogen 0.05 to 0.55 optionally one or more of the elements vanadium, niobium, tantalum, tungsten, aluminum, titanium, copper, boron in a concentration of at most 2.0% by weight, the rest iron and production-related impurities with the proviso that their nickel content is below 0, 5% by weight and the material is quenched after a solution heat treatment carried out at a temperature of 1010 ° C. to 1080 ° C. and is optionally cold-formed to increase the yield strength and strength of the material and has an austenitic structure.
• the advantages achieved by the invention are essentially to be seen in the fact that, on the one hand, it has been found that a subcritical nickel concentration of the alloy does not trigger any allergic reactions, but on the other hand the material has at least the favorable usage properties known from nickel-containing, austenitic, stainless steels.
• the material according to the invention is subjected to a solution heat treatment with subsequent quenching, because it eliminates precipitates, for example carbides and / or structural phases, and stabilizes a purely austenitic structural state.
• Structural inhomogeneity or excretions are mostly associated with local concentration differences of alloy or trace elements, which results in concentration maxima and allergic reactions can be caused.
• a chemical structuring ability of the part is also adversely affected by material inhomogeneity.
• a molybdenum content of up to 1.6% by weight improves the corrosion resistance and can increase the mechanical properties of the material. Higher levels were not favorable because molybdenum is a ferrite and carbide-forming element.
• the alloy has the concentrations of the elements carbon, manganese, chromium, nitrogen and nickel characterized in claims 2 and 3.
• the part formed from the alloy has a Cold working of at least 5%, preferably greater than 15%.
• the 0.2% proof stress of the material can be increased from approx. 400 N / mm2 to, for example, approx. 900 N / mm2 by an approx. 25 to 30% degree of deformation.
• a desired yield strength can thus be easily set by a correspondingly large cold deformation without, as has been found by numerous tests, the stress corrosion cracking and the toughness of the material and the fatigue with elastic change in shape, in particular bending, being adversely affected.
• the austenitic amagnetic material state is retained even at high degrees of cold forming, so there is no formation of deformation martensite, which is magnetic, known to the person skilled in the art of manganese steels, which makes the material particularly suitable for watch cases and watch bands.
• the material according to the invention can be used particularly well for parts of clothing, preferably underwear, such as corsets, possibly medical support corsets, because with good skin tolerance, an easily attainable high material strength enables a small wall thickness of the fastener parts.
• the alloy can be used for the production of costume jewelry and the like, it is advantageous that after a mechanical, but in particular after a chemical structuring, a particularly effective gloss of the surface can be achieved without impairing the good skin tolerance of the part.
• the good skin tolerance can also be used advantageously when using the alloy for everyday objects such as spectacle frames, banknote clips, parts of writing implements, household objects, keys, coins and the like.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Adornments (AREA)

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Cited By (12)

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Citations (7)

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• 1992
  • 1992-07-07 AT AT139392A patent/AT397968B/de not_active IP Right Cessation
• 1993
  • 1993-06-21 CH CH1862/93A patent/CH684979B5/de not_active IP Right Cessation
  • 1993-08-23 EP EP93890161A patent/EP0640695B1/fr not_active Revoked

Patent Citations (7)

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