Stainless steel brake disc and method for production thereof

Patent metadata

Field	Value
Publication number	US-9523402-B2
Application number	US-201414394624-A
Country	US
Kind code	B2
Filing date	Feb 7, 2014
Priority date	Feb 8, 2013
Publication date	Dec 20, 2016
Grant date	Dec 20, 2016

Abstract

The present invention is directed to a stainless steel brake disc which is excellent in toughness, corrosion resistance, and wear resistance, and comprises, in % by mass, 0.030 to 0.080% of C, 0.05% to 1.0% of Si, 1.0 to 1.5% of Mn, 0.035% or less of P, 0.015% or less of S, 11.0 to 14.0% of Cr, 0.01 to 0.50% of Ni, 0.001 to 0.15% of V, less than 0.1% of Nb, 0.05% or less of Ti, 0.05% or less of Zr, 0.05% or less of Al, 0.015 to 0.060% of N, 0.0002% or more and 0.0050% or less of B, and 0.0080% or less of O, wherein an AT value of equation 1 is 0.055 to 0.090, equation 2 is satisfied, a ferrite phase fraction, in which an IQ value of an EBSD pattern is 4,000 or more, is 1% to 15%, a Charpy impact value is 50 J/cm 2 or more, and hardness is 32 to 38 HRC.

C+0.8(N−B)  (1)

PV=1.2Ti+0.8Zr+Nb+1.1Al+O≦0.1  (2)

First claim

The invention claimed is:

1. A stainless steel brake disc comprising, in % by mass, a stainless steel comprising 0.030 to 0.080% of C, 0.05% to 1.0% of Si, 1.0 to 1.5% of Mn, 0.035% or less of P, 0.015% or less of S, 11.0 to 14.0% of Cr, 0.01 to 0.50% of Ni, 0.001 to 0.15% of V, 0.10% or less of Nb, 0.05% or less of Ti, 0.05% or less of Zr, 0.05% or less of Al, 0.015 to 0.060% of N, 0.0002% or more and 0.0050% or less of B, and 0.0080% or less of O,
wherein an AT value of equation 1 is 0.055 or more and 0.090 or less,
equation 2 is satisfied,
the balance of the stainless steel is Fe and inevitable impurities,
a ferrite phase fraction of the stainless steel, defined by the fact that an image quality value of an electron backscatter diffraction (EBSD) pattern is 4,000 or more, and said ferrite phase fraction is 1% or more and 15% or less of the stainless steel, and
surface hardness of the stainless steel is 32 HRC or more and 38 HRC or less:
AT=C+0.8(N−B)  (1)

PV=1.2Ti+0.8Zr+Nb+1.1Al+O≦0.1  (2)

where N, B, Ti, Zr, Nb, Al, and O in equation 1 and equation 2 each means the element content (% by mass).

2. The stainless steel brake disc according to claim 1 , further comprising, in % by mass, one or two or more of 1.0% or less of Cu, 0.5% or less of Mo, 0.3% or less of Sn, 0.3% or less of Sb, 0.2% or less of rare earth elements, and 0.3% or less of Ga.

3. A method for producing a stainless steel brake disc comprising, in % by mass, a stainless steel comprising 0.030 to 0.080% of C, 0.05% to 1.0% of Si, 1.0 to 1.5% of Mn, 0.035% or less of P, 0.015% or less of S, 11.0 to 14.0% of Cr, 0.01 to 0.50% of Ni, 0.001 to 0.15% of V, 0.10% or less of Nb, 0.05% or less of Ti, 0.05% or less of Zr, 0.05% or less of Al, 0.015 to 0.060% of N, 0.0002% or more and 0.0050% or less of B, and 0.0080% or less of O,
wherein an AT value of equation 1 is 0.055 or more and 0.090 or less,
equation 2 is satisfied, and
the balance of the stainless steel is Fe and inevitable impurities,
said method comprises the steps of:
heating said stainless steel to a temperature of 950° C. or more and 1050° C. or lower;
retaining at a heating temperature for more than 0.1 second and 5 seconds or less;
cooling at a cooling rate of 100° C./s or more; and
setting a duration from the start of heating up to the start of cooling of 50 seconds or less:
AT=C+0.8(N−B)  (1)

PV=1.2Ti+0.8Zr+Nb+1.1Al+O≦0.1  (2)

where N, B, Ti, Zr, Nb, Al, and O in equation 1 and equation 2 each means the element content (% by mass).

4. The method for producing a stainless steel brake disc according to claim 3 , further comprising, in % by mass, one or two or more of 1.0% or less of Cu, 0.5% or less of Mo, 0.3% or less of Sn, 0.3% or less of Sb, 0.2% or less of rare earth elements, and 0.3% or less of Ga.

Assignees

• Nippon Steel & Sumikin Sst

Inventors

• Teraoka Shinichi
• Inoue Yoshiharu
• Koyama Yuji
• Kobayashi Masaaki
• Tanoue Toshio

Classifications

• C22C38/48

  with niobium or tantalum · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• F16D65/125 Primary

  characterised by the material used for the disc body · CPC title

• C22C38/001

  containing N · CPC title

• C22C38/50

  with titanium or zirconium · CPC title