Quenching method for steel pipe
View Patent ↗A method for quenching a steel pipe by water cooling from an outer surface thereof, where pipe end portions are not subjected to water cooling, and at least part of a main body other than the pipe end portions is subjected to water cooling. A region(s) that is not subjected to direct water cooling over an entire circumference thereof can be along an axial direction at least in part of the main body other than the pipe end portions. The start and stop of water cooling can be intermittent at least in part of the quenching. During the water cooling of the pipe outer surface, an intensified water cooling can be performed in a temperature range in which the pipe outer surface temperature is higher than Ms point. Thereafter, the cooling can be switched to moderate cooling so that the outer surface is cooled down to Ms point or lower.
1. A method for quenching a steel pipe by water cooling from an outer surface thereof, wherein
subjecting pipe end portions to air cooling from outer surfaces of the pipe end portions when at least part of a main body other than the pipe end portions is subjected to water cooling from an outer surface of the main body, and
the pipe end portions are not subject to water cooling during the subjecting step.
2. The method for quenching a steel pipe according to claim 1 , wherein
a region(s) that is not subjected to direct water cooling over an entire circumference thereof is provided along an axial direction at least in part of the main body other than the pipe end portions.
3. The method for quenching a steel pipe according to claim 2 , wherein
the steel pipe contains 0.2 to 1.2% of C in mass %.
4. The method for quenching a steel pipe according to claim 2 , wherein
the steel pipe is a Cr-based stainless steel pipe containing, in mass %, 0.10 to 0.30% of C and 11 to 18% of Cr.
5. The method for quenching a steel pipe according to claim 2 , wherein
the start and stop of water cooling are repeated intermittently at least in part of a quenching process.
6. The method for quenching a steel pipe according to claim 5 , wherein
the steel pipe contains 0.2 to 1.2% of C in mass %.
7. The method for quenching a steel pipe according to claim 5 , wherein
the steel pipe is a Cr-based stainless steel pipe containing, in mass %, 0.10 to 0.30% of C and 11 to 18% of Cr.
8. The method for quenching a steel pipe according to claim 2 , wherein
in order to apply water cooling onto an outer surface of the steel pipe, a first water cooling is performed in a temperature range in which the temperature of the outer surface of the steel pipe is higher than Ms point, thereafter switched to a second water cooling that is using a lesser amount of water than the first water cooling or air cooling, and the outer surface is forcedly cooled down to Ms point or lower.
9. The method for quenching a steel pipe according to claim 8 , wherein
the steel pipe contains 0.2 to 1.2% of C in mass %.
10. The method for quenching a steel pipe according to claim 8 , wherein
the steel pipe is a Cr-based stainless steel pipe containing, in mass %, 0.10 to 0.30% of C and 11 to 18% of Cr.
11. The method for quenching a steel pipe according to claim 1 , wherein
the start and stop of water cooling are repeated intermittently at least in part of a quenching process.
12. The method for quenching a steel pipe according to claim 11 , wherein
the steel pipe contains 0.2 to 1.2% of C in mass %.
13. The method for quenching a steel pipe according to claim 11 , wherein
the steel pipe is a Cr-based stainless steel pipe containing, in mass %, 0.10 to 0.30% of C and 11 to 18% of Cr.
14. The method for quenching a steel pipe according to claim 1 , wherein
in order to apply water cooling onto an outer surface of the steel pipe, a first water cooling is performed in a temperature range in which the temperature of the outer surface of the steel pipe is higher than Ms point, thereafter switched to a second water cooling that uses a lesser amount of water than the first water cooling or air cooling, and the outer surface is forcedly cooled down to Ms point or lower.
15. The method for quenching a steel pipe according to claim 14 , wherein
the steel pipe contains 0.2 to 1.2% of C in mass %.
16. The method for quenching a steel pipe according to claim 14 , wherein
the steel pipe is a Cr-based stainless steel pipe containing, in mass %, 0.10 to 0.30% of C and 11 to 18% of Cr.
17. The method for quenching a steel pipe according to claim 1 , wherein
the steel pipe contains 0.2 to 1.2% of C in mass %.
18. The method for quenching a steel pipe according to claim 1 , wherein
the steel pipe is a Cr-based stainless steel pipe containing, in mass %, 0.10 to 0.30% of C and 11 to 18% of Cr.