HEAT TREATMENT METHOD AND HEAT TREATMENT DEVICE

• US 20190309386A1
• Filed: 07/14/2017
• Published: 10/10/2019
• Est. Priority Date: 07/14/2016
• Status: Active Grant

• Current Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Original Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Inventors: SUZUKI, Kensuke, YOSHIDA, Wataru
• Granted Patent: US 11,136,640 B2
• Time in Patent Office: Days
• CPC Class Codes: C21D 1/10 by electric induction
• CPC Class Codes: C21D 1/18 Hardening C21D1/02 takes precedence; Quenching with or without subsequent tempering quenching devices C21D1/62
• CPC Class Codes: C21D 1/42 Induction heating
• CPC Class Codes: C21D 1/62 Quenching devices
• CPC Class Codes: C21D 1/63 for bath quenching
• CPC Class Codes: C21D 1/667 for spray quenching
• CPC Class Codes: C21D 9/40 for rings; for bearing races
• CPC Class Codes: F16C 19/36 with a single row of rollers
• CPC Class Codes: F16C 19/364 with tapered rollers, i.e. rollers having essentially the shape of a truncated cone
• CPC Class Codes: F16C 2204/66 High carbon steel, i.e. carbon content above 0.8 wt%, e.g. through-hardenable steel
• CPC Class Codes: F16C 2204/70 with chromium as the next major constituent
• CPC Class Codes: F16C 2223/10 Hardening, e.g. carburizing, carbo-nitriding in general C21D, C23C8/00
• CPC Class Codes: F16C 33/62 Selection of substances
• CPC Class Codes: F16C 33/64 Special methods of manufacture
• CPC Class Codes: Y02P 10/25 Process efficiency

Abstract

In a heat treatment method for obtaining a bearing ring for an annular roller bearing whose thickness changes in an axial direction, the heat treatment method includes (A) applying a quenching process to a work which is annular, made of high carbon chromium bearing steel, and having a thickness changing in an axial direction, (B) applying a tempering process to the work which is quenched to entirely soak the work in cooling liquid and inductively heat the work in a state that the work is soaked in the cooling liquid, and (C) applying a finishing process to the work which is tempered.

Claims

1. A heat treatment method for obtaining a bearing ring for an annular roller bearing, the heat treatment method comprising:

(A) applying a quenching process to a work which is annular, made of high carbon chromium bearing steel, and having a thickness changing in an axial direction;

(B) applying a tempering process to the work which is quenched to entirely soak the work in cooling liquid and inductively heat the work in a state that the work is soaked in the cooling liquid; and

(C) applying a finishing process to the work which is tempered,

wherein the process (B) is carried out

(B1) in such a way that the work is divided into a plurality of blocks along the axial direction in accordance with the thickness and the block in which the thickness is thicker is inductively heated in a lower frequency than the thinner block; and

(B2) under a state that a flow of the cooling liquid is generated so as to collect the cooling liquid to a part in which a first raceway surface of the work is formed in the cooling liquid in which the work is soaked.

2. A heat treatment method according to claim 1,

wherein in the process (B), an injection nozzle which injects the cooling liquid is used and an injection opening of the injection nozzle is opposed to the part in which the first raceway surface is formed to inject the cooling liquid to the part in which the first raceway surface is formed from the injection opening.

3. A heat treatment method according to claim 1,

wherein in the (B1), a frequency fin which the blocks are respectively inductively heated is set in such a way that a ratio of the thickness T (mm) of each block to a current penetration depth δ

(mm) represented by a below-described expression (1) satisfies a below-described inequality (2), and

δ

=5.03√

{square root over (ρ

/μ

f)} 

 

(1)

wherein the ρ

is a specific resistance (μ

Ω

·

mm) at 20°

C. of the work, the μ

is a relative magnetic permeability and the f is the frequency (Hz) of the inductively heating.

1.5<

=T/δ

<

=4.0 

 

(2)

4. A heat treatment method according to claim 1,

wherein the work includes an inner layer part, a surface layer part which surrounds an entire part of a periphery of the inner layer part and has Vickers hardness on a surface higher than that of the inner layer part, a first raceway surface having a compression residual stress and including a part which comes into contact with at least one end of a rolling surface of a roller in an axial direction and a second raceway surface having a compression residual stress lower than that of the first raceway surface are provided, and

wherein the thickness changes in the axial direction.

5. A manufacturing method of a bearing ring for an annular roller bearing, the manufacturing method comprising:

(A) applying a quenching process to a work which is annular, made of high carbon chromium bearing steel, and having a thickness changing in an axial direction;

(B) applying a tempering process to the work which is quenched to entirely soak the work in cooling liquid and inductively heat the work in a state that the work is soaked in the cooling liquid; and

(C) applying a finishing process to the work which is tempered,

wherein the process (B) is carried out

(B1) in such a way that the work is divided into a plurality of blocks along the axial direction in accordance with the thickness and the block in which the thickness is thicker is inductively heated in a lower frequency than the thinner block; and

(B2) under a state that a flow of the cooling liquid is generated so as to collect the cooling liquid to a part in which a first raceway surface of the work is formed in the cooling liquid in which the work is soaked.

6. A manufacturing method according to claim 5,

wherein in the process (B), an injection nozzle which injects the cooling liquid is used and an injection opening of the injection nozzle is opposed to the part in which the first raceway surface is formed to inject the cooling liquid to the part in which the first raceway surface is formed from the injection opening.

7. A manufacturing method according to claim 5,

wherein in the (B1), a frequency fin which the blocks are respectively inductively heated is set in such a way that a ratio of the thickness T (mm) of each block to a current penetration depth δ

(mm) represented by a below-described expression (1) satisfies a below-described inequality (2), and

δ

=5.03√

{square root over (ρ

/μ

f)} 

 

(1)

wherein the ρ

is a specific resistance (μ

Ω

·

mm) at 20°

C. of the work, the μ

is a relative magnetic permeability and the f is the frequency (Hz) of the inductively heating.

1.5<

=T/δ

<

=4.0 

 

(2)

8. A manufacturing method according to claim 5,

wherein the work includes an inner layer part, a surface layer part which surrounds an entire part of a periphery of the inner layer part and has Vickers hardness on a surface higher than that of the inner layer part, a first raceway surface having a compression residual stress and including a part which comes into contact with at least one end of a rolling surface of a roller in an axial direction and a second raceway surface having a compression residual stress lower than that of the first raceway surface are provided, and

wherein the thickness changes in the axial direction.

9. A heat treatment device which inductively heats a work which is annular and made of a steel material to apply a heat treatment thereto, the heat treatment device comprising:

a treatment vessel in which the work is set to apply the heat treatment to the work,

a holding part which holds the work in a predetermined position,

a heating member which surrounds the work to inductively heat the work, and

an injection nozzle which injects cooling liquid to the work,

wherein the heating member is formed with a plurality of inductively heating coils and frequencies of the inductively heating coils are respectively independently controlled.

10. A heat treatment device according to claim 9,

wherein in the injection nozzle, an injection opening is arranged so as to be opposed to the work.