Magnet assembly for dental magnetic attachment
AssigneeHitachi Metals, Ltd.
InventorsYukyo Takada, Masatoshi Takahashi, Akira Kikuchi
Life of this patent
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Abstract
A magnet assembly for a dental magnetic attachment comprising a cup-shaped yoke of substantially Ni-free ferritic stainless steel, a permanent magnet received in a recess of the cup-shaped yoke, a seal member sealing an opening of the cup-shaped yoke, and an abutment-welded portion of the seal member and the cup-shaped yoke; the seal member comprising a center portion of substantially Ni-free ferritic stainless steel; an intermediate portion of substantially Ni-free austenitic stainless steel having a nitrogen content of 0.5-2.0% by mass, and a peripheral portion made of substantially Ni-free ferritic stainless steel having a nitrogen content of 1.3% or less by mass, smaller than in the intermediate portion.
Claims14
A magnet assembly for a dental magnetic attachment comprising:
- a cup-shaped yoke of substantially Ni-free ferritic stainless steel, a permanent magnet received in a recess of said cup-shaped yoke, a seal member sealing an opening of said cup-shaped yoke, and an abutment-welded portion of said seal member and said cup-shaped yoke;
- said seal member integrally comprising:
- a center portion of substantially Ni-free ferritic stainless steel;
- an intermediate portion outside said center portion, which is made of substantially Ni-free austenitic stainless steel having a nitrogen content of 0.5-2.0% by mass;
- and
- a peripheral portion outside said intermediate portion, which is made of substantially Ni-free ferritic stainless steel having a nitrogen content of 1.3% or less by mass, wherein the nitrogen content in said peripheral portion is smaller than that in said intermediate portion,
- wherein said cup-shaped yoke and said seal member have a Ni content of 0.2% or less by mass, and
- wherein the abutment-welded portion welds said peripheral portion of said seal member to said cup-shaped yoke.
A method for producing a magnet assembly for a dental magnetic attachment comprising:
- a cup-shaped yoke of substantially Ni-free ferritic stainless steel, a permanent magnet received in a recess of said cup-shaped yoke, a seal member sealing an opening of said cup-shaped yoke, and an abutment-welded portion of said seal member and said cup-shaped yoke;
- said seal member integrally comprising:
- a center portion of substantially Ni-free ferritic stainless steel;
- an intermediate portion outside said center portion, which is made of substantially Ni-free austenitic stainless steel having a nitrogen content of 0.5-2.0% by mass;
- and
- a peripheral portion outside said intermediate portion, which is made of substantially Ni-free ferritic stainless steel having a nitrogen content of 1.3% or less by mass, wherein the nitrogen content in said peripheral portion is smaller than that in said intermediate portion,
- wherein said cup-shaped yoke and said seal member have a Ni content of 0.2% or less by mass, and
- wherein the abutment-welded portion welds said peripheral portion of said seal member to said cup-shaped yoke, comprising the steps of placing the permanent magnet in the recess of the cup-shaped yoke of substantially Ni-free ferritic stainless steel, inserting the disc-shaped seal member into an opening of the recess, and welding an abutment portion of the cup-shaped yoke and the seal member,
- wherein the seal member is obtained by subjecting a round rod of substantially Ni-free ferritic stainless steel to a nitrogen-dissolving treatment to austenize a surface layer of the round rod to a predetermined depth, denitriding a surface portion of the austenized portion for ferritization, and then transversely cutting the round rod to a disc shape.
Dependencies are inferred from the claim text.