# US 10,370,734 B2 · Method for heat treatment of stainless member, and method for producing forged stainless product

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- Number: US 10,370,734 B2
- Document ID: US10370734B2
- Status: Granted
- Kind: B2
- Application number: 15/025,699
- Filed: 2014-09-29
- Published: 2016-08-18
- Granted: 2019-08-06
- Earliest claimed: 2013-10-11
- Assignees: Mitsubishi Hitachi Power Systems, Ltd.
- Applicants: Mitsubishi Hitachi Power Systems, Ltd.
- Inventors: Kohei Hatano; Hiroharu Oyama; Yasuo Matsunami; Naoyuki Umezu; Shuhei Kuroki; Hidetaka Haraguchi; Takumi Matsumura; Motonari Machida
- Web page: https://patentgrep.com/patent/US10370734B2

## CPC

- C21D 9/0068: {for particular articles not mentioned below}
- B21K 3/04: blades, e.g. for turbines; Upsetting of blade roots
- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- C21D 1/19: by interrupted quenching
- C21D 1/70: while heating or quenching
- C21D 6/00: Heat treatment of ferrous alloys
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- C21D 6/02: Hardening by precipitation
- C21D 8/00: Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02)
- F01D 5/286: {Particular treatment of blades, e.g. to increase durability or resistance against corrosion or erosion (F01D5/288 takes precedence)}
- C21D 1/00: General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D 9/00: Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- F05D 2230/25: by forging
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- B21K: MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS (making particular articles by working sheet metal without essentially removing material B21D; processing wire B21F; making pins, needles or nails B21G; making particular articles by rolling B21H; forging machines, pressing machines, hammering machines, in general B21J; making chains B21L; plating B23K)
- F01D: NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES (machines or engines for liquids F03; non-positive displacement pumps F04D)
- F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS

## Abstract

A heating step, in which a stainless member is heated to a temperature within or above a heating phase-transformation temperature range (Ar) in which the stainless member is phase-transformed, is executed. A cooling step in which the stainless member heated in the heating step is cooled to a temperature below a cooling phase-transformation temperature range (Mr) in which the stainless member is phase-transformed, is executed. In the cooling step, cooling of the stainless member is suppressed in a control temperature range including the cooling phase-transformation temperature range (Mr).

## Claims

### Claim 1

A method for heat treatment of a stainless member,
a heating step, in which a stainless member is heated to a temperature within or above a heating phase-transformation temperature range in which the stainless member is phase-transformed when the stainless member is heated, is executed; and
a cooling step, in which the stainless member heated in the heating step is cooled to a temperature below a cooling phase-transformation temperature range in which the stainless member is phase-transformed when the stainless member is cooled, is executed,
wherein in the cooling step,
a cooling medium is supplied to the stainless member,
a flow rate of the cooling medium supplied to the stainless member per unit time is gradually increased from when the cooling step is started until when a predetermined length of time has elapsed, or from when the cooling step is started until when the temperature of the stainless member reaches a predetermined temperature, and
a flow rate of the cooling medium in a control temperature range including the cooling phase-transformation temperature range is set to be smaller than those immediately before the temperature of the stainless member reaches the control temperature range and immediately after the temperature passes the control temperature range,
wherein the predetermined length of time is shorter than a length of time from when the cooling step is started until when a temperature of the stainless member is a temperature within the heating phase-transformation temperature range,
wherein the predetermined temperature is above the heating phase-transformation temperature range.

### Claim 2 (depends on 1)

The method for heat treatment of a stainless member according to claim 1,
wherein in the cooling step, a length of time from when the cooling of the stainless member is started until when the temperature of the stainless member reaches the cooling phase-transformation temperature range is obtained in advance, and
wherein in the cooling step, the flow rate of the cooling medium supplied to the stainless member is decreased before the length of time obtained in advance has elapsed from when the cooling of the stainless member is started.

### Claim 3 (depends on 1)

The method for heat treatment of a stainless member according to claim 1,
wherein a phase-transformation start temperature of the cooling phase-transformation temperature range is obtained in advance, and
wherein in the cooling step, the flow rate of the cooling medium supplied to the stainless member is decreased before the temperature of the stainless member reaches the phase-transformation start temperature.

### Claim 4 (depends on 1)

The method for heat treatment of a stainless member according to claim 1,
wherein the stainless steel member has a small surface area portion having a surface area per unit mass equal to or less than a first surface area and a large surface area portion having a surface area per unit mass larger than the first surface area, and
wherein in the cooling step, a covering member covering the large surface area portion of the stainless member is provided on a large surface area portion having a large surface area per unit mass.

### Claim 5 (depends on 4)

The method for heat treatment of a stainless member according to claim 4, wherein dimensions of the covering member are determined such that an amount of heat dissipation per unit mass from the large surface area portion covered with the covering member is the same as the amount of heat dissipation per unit mass from a portion not covered with the covering member.

### Claim 6 (depends on 4)

The method for heat treatment of a stainless member according to claim 4,
wherein the covering member is made of the same material as that of the stainless member.

### Claim 7 (depends on 4)

The method for heat treatment of a stainless member according to claim 4,
wherein the covering member is provided on the stainless member before the heating step is started.

### Claim 8 (depends on 1)

The method for heat treatment of a stainless member according to claim 1,
wherein the stainless member is made of a precipitation hardening stainless steel.