| (19) |
 |
|
(11) |
EP 1 116 796 A3 |
| (12) |
EUROPEAN PATENT APPLICATION |
| (88) |
Date of publication A3: |
|
17.12.2003 Bulletin 2003/51 |
| (43) |
Date of publication A2: |
|
18.07.2001 Bulletin 2001/29 |
| (22) |
Date of filing: 08.01.2001 |
|
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| (84) |
Designated Contracting States: |
|
AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE TR |
|
Designated Extension States: |
|
AL LT LV MK RO SI |
| (30) |
Priority: |
11.01.2000 JP 2000006219
|
| (71) |
Applicants: |
|
- JAPAN as represented by NATIONAL RESEARCH INSITUTE FOR METALS
Ibaraki 300-26 (JP)
- Sumitomo Metal Industries Limited
Chiyoda-ku, Tokyo (JP)
|
|
| (72) |
Inventors: |
|
- Fujitsuna, Nobuyuki
2-1 Sengen 1-chome Tsukuba-shi Ibaraki (JP)
- Igarashi, Masaaki
2-1 Sengen 1-chome Tsukuba-shi Ibaraki (JP)
- Abe, Fujio
2-1 Sengen 1-chome Tsukuba-shi Ibaraki (JP)
|
| (74) |
Representative: Calamita, Roberto |
|
Frank B. Dehn & Co., European Patent Attorneys, 179 Queen Victoria Street
London EC4V 4EL
London EC4V 4EL (GB) |
|
| |
|
| (54) |
High chromium ferritic heat resisting steel and method of heat treatment for the same |
(57) The invention provides a method of heat-treatment for high chromium ferritic heat
resisting steel, which comprises the steps of:
- (a) heat-treating for 5 seconds or longer high chromium ferritic steel containing
chromium (Cr) in amount of 7-12 weight %; one or two elements of molybdenum (Mo) and
tungsten (W) as a solid-solution strengthening element; and one or more of elements
for forming (a) MX carbonitride(s) at a temperature higher than both solid-solution
temperature of said element(s) for forming the MX carbonitride(s) and a precipitation
starting temperature of δ ferrite;
- (b) cooling said steel at a rate of 0.5°C/s or faster; and
- (c) subsequently tempering said steel.