Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1996-04-19
1998-06-23
Sheehan, John
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
148122, 148222, 148225, 148230, 148233, H01F 100
Patent
active
057699658
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on a method for treating at least one part made of soft magnetic material, to form a hard wear area. A method is already known (German Patent Disclosure DE 31 49 916 A1) in which an armature, made of soft magnetic material, of a fuel injection valve is hardened in certain regions by nitriding to increase its wear resistance. This way of achieving wear protection by nitriding does not produce optimal switching functions of the magnet valve unless the production-dictated lessening of the magnetic properties is reversed by annealing. This has disadvantages, however: the double heat treatment entails increased costs; between annealing and nitriding, temporary storage of the part and transporting are necessary, with the attendant danger of damage; and after the annealing the surface of the parts can be contaminated.
A method is also known (German Patent Disclosure DE 30 16 993 A1), in which an armature of soft magnetic material is partially hardened by case hardening. The production steps for the particular armature and the case hardening produce the disadvantage that the armature is magnetically impaired, which thus undesirably impairs the function of the magnet valve.
A method is also known (German Patent Disclosure DE 37 33 809 A1) in which the valve member of a magnet valve is made of a nonmagnetic steel containing from 7.8 to 24.5% manganese, and the surface of the valve member is at least partially nitrided by plasma nitriding or so-called ion nitriding. However, this kind of steel cannot be used as a material for an armature or core for a magnet valve.
ADVANTAGES OF THE INVENTION
The method according to the invention has the advantage over the prior art of being especially economical, since for treating the soft magnetic part by annealing and producing a wear guard layer, no transportation between the individual treatment steps is needed; thus the space requirement and costs are reduced, and contamination of the surface of the part after the annealing is averted.
Advantageous further features of and improvements to the method disclosed in claim 1 are possible by means of the provisions recited in the dependent claims.
It is advantageous to carry out the annealing and the production of the wear guard layer in succession, regardless of the order, and in particular to carry out the annealing prior to the creation of the wear guard layer; as a result, a favorable environment for each operation can be created in the reaction chamber independently of one another, first for the annealing and then for the creation of the wear guard layer. For the annealing, this environment can be a vacuum; otherwise, an inert gas, a noble gas, a reducing gas, or a mixture thereof can also be used.
For the creation of the wear guard layer on the part, any methods involving furnaces, such as nitriding, carburizing, or other layer-forming processes are advantageous. The method can advantageously be shortened if the annealing and the creation of the wear guard layer are done simultaneously at annealing temperature.
Forming the parts of soft magnetic or ferritic chromium steel is advantageous.
It is also advantageous to use a part treated as an armature or core in a magnet valve or fuel injection valve actuatable by an electromagnet.
BRIEF DESCRIPTION OF THE DRAWINGS
Exemplary embodiments of the invention are shown in simplified form in the drawing and described in further detail in the ensuing description. FIG. 1 shows a cross-sectional view of a fuel injection valve; FIG. 2 shows a cross-sectional view of a magnet valve; FIG. 3 shows a partial cross-sectional view of an apparatus for performing the method of the invention; FIG. 4 is a diagram with the temperature as the ordinate and the time as the abscissa, showing the course of the prior art method; FIGS. 5 and 6 are diagrams with the temperature as the ordinate and the time as the abscissa, showing the course of the method of the invention; and FIG. 7 shows a partial cross-sectional view of a holder device.
DETAILED DE
REFERENCES:
Patent Abstracts of Japan, vol. 15 No. 289 (C-0852), 7 JP 03-104881, May 1991.
Derwent Publications Ltd.; An 78-28000ac15 JP 53-023836, Mar. 1978.
Stramke et al., "Eltropuls-Plasmanitriere, ein neues Verrahren der Warmebehandlaungstechnik" ZWF, pp. 589-892, Dec. 1983.
Graner Juergen
Illing Joerg
Keim Norbert
Liedtke Dieter
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
Sheehan John
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