Austenitic alloy pipe and method for producing the same
View Patent ↗There is provided an austenitic alloy pipe that is durable even if a stress distribution different according to usage environment is applied. The austenitic alloy pipe in accordance with the present invention has a tensile yield strength YS LT of at least 689.1 MPa. The tensile yield strength YS LT , a compressive yield strength YS LC in a pipe axial direction, a tensile yield strength YS CT in a pipe circumferential direction of the alloy pipe, and a compressive yield strength YS CC in the pipe circumferential direction satisfy Formulas (1) to (4). 0.90≦ YS LC /YS LT ≦1.11 (1) 0.90≦ YS CC /YS CT ≦1.11 (2) 0.90≦ YS CC /YS LT ≦1.11 (3) 0.90≦ YS CT /YS LT ≦1.11 (4)
1. An austenitic alloy pipe, wherein
a tensile yield strength YS LT in a pipe axial direction of the alloy pipe is at least 689.1 MPa; and
the tensile yield strength YS LT , a compressive yield strength YS LC in the pipe axial direction, a tensile yield strength YS CT in a pipe circumferential direction of the alloy pipe, and a compressive yield strength YS CC in the pipe circumferential direction satisfy Formulas (1) to (4).
0.90≦ YS LC /YS LT ≦1.11 (1)
0.90≦ YS CC /YS CT ≦1.11 (2)
0.90≦ YS CC /YS LT ≦1.11 (3)
0.90≦ YS CT /YS LT ≦1.11 (4)
2. The austenitic alloy pipe according to claim 1 , comprising, by mass percent, of C: at most 0.03%, Si: at most 1.0%, Mn: 0.3 to 5.0%, Ni: 23 to 52%, Cr: 20 to 30%, N: 0.005 to 0.50%, Mo: at most 9%, and Cu: at most 3%, the balance being Fe and impurities.
3. The austenitic alloy pipe according to claim 2 , comprising, in place of some of the Fe, at least one type selected from a group consisting, by mass percent, of Ca: at most 0.01%, Mg: at most 0.01%, and REM (rare earth metal): at most 0.20%.
4. The austenitic alloy pipe according to claim 1 , which is produced by being subjected to straightening and low-temperature heat treatment at 300 to 550° C. after being cold-worked.
5. The austenitic alloy pipe according to claim 4 , which is produced by being subjected to the low-temperature heat treatment after being straightened.
6. A method for producing an austenitic alloy pipe, comprising:
a process for producing an austenitic alloy material pipe;
a process for cold-working the material pipe; and
a process for producing an austenitic alloy pipe, wherein by subjecting the cold-worked material pipe to straightening and low-temperature heat treatment at 300 to 550° C., the alloy pipe is provided with a tensile yield strength YS LT of at least 689.1 MPa in a pipe axial direction of the alloy pipe, and wherein for the alloy pipe, the tensile yield strength YS LT , a compressive yield strength YS LC (MPa) in the pipe axial direction, a tensile yield strength YS CT (MPa) in a pipe circumferential direction, and a compressive yield strength YS CC (MPa) in the pipe circumferential direction satisfy Formulas (1) to (4).
0.90≦ YS LC /YS LT ≦1.11 (1)
0.90≦ YS CC /YS CT ≦1.11 (2)
0.90≦ YS CC /YS LT ≦1.11 (3)
0.90≦ YS CT /YS LT ≦1.11 (4)
7. The method for producing an austenitic alloy pipe according to claim 6 , wherein the material pipe is subjected to the low-temperature heat treatment after being straightened.
8. The method for producing an austenitic alloy pipe according to claims 6 , wherein the material pipe comprises, by mass percent, of C: at most 0.03%, Si: at most 1.0%, Mn: 0.3 to 5.0%, Ni: 23 to 52%, Cr: 20 to 30%, N: 0.005 to 0.50%, Mo: at most 9%, and Cu: at most 3%, the balance being Fe and impurities.
9. The method for producing an austenitic alloy pipe according to claim 8 , wherein the material pipe comprises, in place of some of the Fe, at least one type selected from a group consisting, by mass percent, of Ca: at most 0.01%, Mg: at most 0.01%, and REM (rare earth metal): at most 0.20%.
10. The austenitic alloy pipe according to claim 2 , which is produced by being subjected to straightening and low-temperature heat treatment at 300 to 550° C. after being cold-worked.
11. The austenitic alloy pipe according to claim 3 , which is produced by being subjected to straightening and low-temperature heat treatment at 300 to 550° C. after being cold-worked.
12. The austenitic alloy pipe according to claim 10 , which is produced by being subjected to the low-temperature heat treatment after being straightened.
13. The austenitic alloy pipe according to claim 11 , which is produced by being subjected to the low-temperature heat treatment after being straightened.
14. The method for producing an austenitic alloy pipe according to claims 7 , wherein the material pipe comprises, by mass percent, of C: at most 0.03%, Si: at most 1.0%, Mn: 0.3 to 5.0%, Ni: 23 to 52%, Cr: 20 to 30%, N: 0.005 to 0.50% Mo: at most 9%, and Cu: at most 3%, the balance being Fe and impurities.
15. The method for producing an austenitic alloy pipe according to claim 14 , wherein the material pipe comprises, in place of some of the Fe, at least one type selected from a group consisting, by mass percent, of Ca: at most 0.01%, Mg: at most 0.01%, and REM (rare earth metal): at most 0.20%.
16. The austenitic alloy pipe according to claim 1 , wherein a microstructure of the austenitic alloy pipe substantially consists of austenite.
17. The method for producing an austenitic alloy pipe according to claim 6 , wherein a microstructure of the austenitic alloy pipe substantially consists of austenite.
18. The method for producing an austenitic alloy pipe according to claim 6 , wherein the process for producing the austenitic alloy material pipe is hot-working.
19. The method for producing an austenitic alloy pipe according to claim 6 , wherein the process for cold-working the material pipe is either cold drawing or cold rolling.