Brake discs excellent in resistance to temper softening and toughness

Abstract

The invention proposes brake discs which have appropriate quench hardness and are excellent both in resistance to temper softening and in toughness. The brake discs are obtained by working a stainless steel sheet having a composition which contains by mass C: 0.1% or below, Si: 1.0% or below, Mn: 2.0% or below, Cr: 10.5 to 15.0%, and N: 0.1% or below and satisfies the relationships: 5Cr + 10Si + 15Mo + 30Nb -9Ni - 5Mn - 3Cu - 225N- 270C < 45 AND 0.03< {(C + N) - (13 / 92)Nb} < 0.09 into a disc-like piece for brake disc and subjecting the disc-like piece to quenching to form a martensite structure having a prior gamma grain size of 8[mu]m or above but below 15[mu]m. The brake disc thus obtained has appropriate quench hardness and is excellent in resistance to temper softening and in toughness. Additionally, the composition may further contain Nb and / or Cu in order to enhance the resistance to temper softening.

Description

technical field [0001] The present invention relates to discs that can be used for disc brakes of motorcycles, motorcars, bicycles, etc., and in particular to having a suitable quenching of the friction parts with brake pads A brake disc having high hardness, high temper softening resistance, and excellent temper softening resistance and toughness. The term "excellent temper softening resistance" in the present invention means that the temper softening resistance is high, and the softening after being kept at a high temperature by friction heat during braking (braking) is small and can be maintained close to the initial stage. The hardness characteristics of the appropriate hardness. Background technique [0002] The function of the brake discs of motorcycles, cars, bicycles, etc. is to restrain the rotation of the wheels and brake the vehicle through the friction between the brake disc and the brake lining. Therefore, it is desirable for the brake disc to have proper hard...

AI Technical Summary

Problems solved by technology

[0009] However, in the techniques described in Japanese Patent Application Laid-Open No. 2002-146489, Japanese Patent No. 3315974, and Japanese Patent Laid-Open No. 2002-121656, it is necessary to add a relatively large amount of high-cost alloy elements, which has the cost of manufacturing brake discs. Expensive, and the problem of sharp decrease in hardness when kept at 600°C for a long time (about 1 hour)

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