Soft Cr-containing steel
The soft Cr-containing steel includes, on a % by mass basis, C: from about 0.001% to about 0.020%, Si: more than about 0.10% and less than about 0.50%, Mn: less than about 2.00%, P: less than about 0.060%, S: less than about 0.008%, Cr: from about 12.0% to about 16.0%, Ni: from about 0.05% to about 1.00%, N: less than about 0.020%, Nb: from about 10×(C+N) to about 1.00%, Mo: more than about 0.80% and less than about 3.00%, wherein the contents of alloying elements, represented by Si and Mo, respectively, on a % by mass, satisfy the formula Si≦1.2−0.4Mo, so as to prevent precipitation of the Laves phase and to stably secure an effect of increasing high-temperature strength due to solid solution Mo.
1. A soft Cr-containing steel having a composition, on a % by mass basis, comprising:
C: from about 0.001% to about 0.020%;
Si: more than about 0.10% and less than about 0.50%;
Mn: less than about 2.00%;
P: less than about 0.060%;
S: less than about 0.008%;
Cr: from about 12.0% or more to about 16.0%;
Ni: from about 0.05% to about 1.00%;
N: less than about 0.020%;
Nb: from about 0.30% to less than 1.00%;
Mo: more than about 0.80% and less than about 3.00%;
W: from more than about 2.00% to about 5.00%; and
Fe and incidental impurities,
wherein the contents of alloying elements, silicon and molybdenum, represented by Si and Mo, respectively, on a % by mass basis, satisfy the following formula (1):
Si≦1.2−0.4Mo (1).
2. The soft Cr-containing steel according to claim 1 , wherein the content of Mo is more than about 1.50% and less than about 3.00% by mass in the composition.
3. The soft Cr-containing steel according to claim 1 , further comprising, on a % by mass basis, at least one selected from the group consisting of Cu: from about 0.05% to about 1.00%, Ti: from about 0.02% to about 0.50%, V: from about 0.05% to about 0.50%, and B: from about 0.0005% to about 0.0100%.
4. The soft Cr-containing steel according to claim 2 , further comprising, on a % by mass basis, at least one selected from the group consisting of Cu: from about 0.05% to about 1.00%, Ti: from about 0.02% to about 0.50%, V: from about 0.05% to about 0.50%, and B: from about 0.0005% to about 0.0100%.
5. The soft Cr-containing steel according to claim 1 , wherein W comprises from more than 2.00% to no more than 3.00%.
6. The soft Cr-containing steel according to claim 2 , wherein W comprises from more than 2.00% to no more than 3.00%.
7. The soft Cr-containing steel according to claim 3 , wherein W comprises from more than 2.00% to no more than 3.00%.
8. The soft Cr-containing steel according to claim 1 , further comprising Al: from about 0.02% to about 0.50% by mass.
9. The soft Cr-containing steel according to claim 2 , further comprising Al: from about 0.02% to about 0.50% by mass.
10. The soft Cr-containing steel according to claim 3 , further comprising Al: from about 0.02% to about 0.50% by mass.
11. The soft Cr-containing steel according to claim 4 , further comprising Al: from about 0.02% to about 0.50% by mass.
12. The soft Cr-containing steel according to claim 1 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
13. The soft Cr-containing steel according to claim 2 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
14. The soft Cr-containing steel according to claim 3 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
15. The soft Cr-containing steel according to claim 4 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
16. The soft Cr-containing steel according to claim 5 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
17. The soft Cr-containing steel according to claim 1 , wherein regarding the state of Mo in the steel, a ratio of (112) diffraction intensity of the Laves phase, (Fe,Cr) 2 (Mo,Nb), to (111) diffraction intensity of Nb carbonitride, Nb(C,N), A value=I{(Fe,Cr) 2 (Mo,Nb)} (112) /I{Nb(C,N)} (11l) , is less than 0.4 based on X-ray diffraction of extraction residues of precipitates in the steel.
18. The soft Cr-containing steel according to claim 1 , wherein the % by mass basis of Nb is from about 0.30% to about 0.70%.
19. A soft ferrite structure, Cr-containing steel having a composition, on a % by mass basis, comprising:
C: from about 0.001% to about 0.020%;
Si: more than about 0.10% and less than about 0.50%;
Mn: less than about 2.00%;
P: less than about 0.060%;
S: less than about 0.008%;
Cr: from about 12.0% or more to about 16.0%;
Ni: from about 0.05% to about 1.00%;
N: less than about 0.020%;
Nb: from about 0.30% to less than 1.00%;
Mo: more than about 0.80% and less than about 3.00%;
W: from more than about 2.00% to about 5.00%; and
Fe and incidental impurities,
wherein the contents of alloying elements, silicon and molybdenum, represented by Si and Mo, respectively, on a % by mass basis, satisfy the following formula (1):
Si≦1.2−0.4Mo (1)
wherein the steel has a ferrite single phase structure.
20. The ferrite structure, soft Cr-containing steel according to claim 19 , wherein the % by mass basis of Nb is from about 0.30% to about 0.70%.
21. An automobile exhaust system component, comprising a member made of a soft Cr-containing steel having a composition, on a % by mass basis, comprising:
C: from about 0.001% to about 0.020%;
Si: more than about 0.10% and less than about 0.50%;
Mn: less than about 2.00%;
P: less than about 0.060%;
S: less than about 0.008%;
Cr: from about 12.0% or more to about 16.0%;
Ni: from about 0.05% to about 1.00%;
N: less than about 0.020%;
Nb: from about 0.30% to less than 1.00%;
Mo: more than about 0.80% and less than about 3.00%;
W: from more than about 2.00% to about 5.00%; and
Fe and incidental impurities,
wherein the contents of alloying elements, silicon and molybdenum, represented by Si and Mo, respectively, on a % by mass basis, satisfy the following formula (1):
Si≦1.2−0.4Mo (1).
22. The automobile exhaust system component of claim 21 , wherein the component is an outer casing for a catalytic converter.
23. The automobile exhaust system component of claim 21 , wherein the component is an exhaust pipe.
24. The soft Cr-containing steel according to claim 19 , wherein the content of Mo is more than about 1.50% and less than about 3.00% by mass in the composition.
25. The soft Cr-containing steel according to claim 19 , further comprising, on a % by mass basis, at least one selected from the group consisting of Cu: from about 0.05% to about 1.00%, Ti: from about 0.02% to about 0.50%, V: from about 0.05% to about 0.50%, and B: from about 0.0005% to about 0.0100%.
26. The soft Cr-containing steel according to claim 24 , further comprising, on a % by mass basis, at least one selected from the group consisting of Cu: from about 0.05% to about 1.00%, Ti: from about 0.02% to about 0.50%, V: from about 0.05% to about 0.50%, and B: from about 0.0005% to about 0.0100%.
27. The soft Cr-containing steel according to claim 19 , wherein W comprises from more than 2.00% to no more than 3.00%.
28. The soft Cr-containing steel according to claim 24 , wherein W comprises from more than 2.00% to no more than 3.00%.
29. The soft Cr-containing steel according to claim 25 , wherein W comprises from more than 2.00% to no more than 3.00%.
30. The soft Cr-containing steel according to claim 19 , further comprising Al: from about 0.02% to about 0.50% by mass.
31. The soft Cr-containing steel according to claim 24 , further comprising Al: from about 0.02% to about 0.50% by mass.
32. The soft Cr-containing steel according to claim 25 , further comprising Al: from about 0.02% to about 0.50% by mass.
33. The soft Cr-containing steel according to claim 26 , further comprising Al: from about 0.02% to about 0.50% by mass.
34. The soft Cr-containing steel according to claim 19 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
35. The soft Cr-containing steel according to claim 24 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
36. The soft Cr-containing steel according to claim 25 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
37. The soft Cr-containing steel according to claim 26 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
38. The soft Cr-containing steel according to claim 27 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
39. The soft Cr-containing steel according to claim 19 , wherein regarding the state of Mo in the steel, a ratio of (112) diffraction intensity of the Laves phase, (Fe,Cr) 2 (Mo,Nb), to (111) diffraction intensity of Nb carbonitride, Nb(C,N), A value=I{(Fe,Cr) 2 (Mo,Nb)} (112) /I{Nb(C,N)} (111) , is less than 0.4 based on X-ray diffraction of extraction residues of precipitates in the steel.
40. The exhaust system according to claim 21 , wherein the content of Mo is more than about 1.50% and less than about 3.00% by mass in the composition.
41. The exhaust system according to claim 21 , further comprising, on a % by mass basis, at least one selected from the group consisting of Cu: from about 0.05% to about 1.00%, Ti: from about 0.02% to about 0.50%, V: from about 0.05% to about 0.50%, and B: from about 0.0005% to about 0.0100%.
42. The exhaust system according to claim 40 , further comprising, on a % by mass basis, at least one selected from the group consisting of Cu: from about 0.05% to about 1.00%, Ti: from about 0.02% to about 0.50%, V: from about 0.05% to about 0.50%, and B: from about 0.0005% to about 0.0100%.
43. The exhaust system according to claim 21 , wherein W comprises from more than 2.00% to no more than 3.00%.
44. The exhaust system according to claim 40 , wherein W comprises from more than 2.00% to no more than 3.00%.
45. The exhaust system according to claim 41 , wherein W comprises from more than 2.00% to no more than 3.00%.
46. The exhaust system according to claim 21 , further comprising Al: from about 0.02% to about 0.50% by mass.
47. The exhaust system according to claim 40 , further comprising Al: from about 0.02% to about 0.50% by mass.
48. The exhaust system according to claim 41 , further comprising Al: from about 0.02% to about 0.50% by mass.
49. The exhaust system according to claim 42 , further comprising Al: from about 0.02% to about 0.50% by mass.
50. The exhaust system according to claim 21 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
51. The exhaust system according to claim 40 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
52. The exhaust system according to claim 41 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
53. The exhaust system according to claim 42 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
54. The exhaust system according to claim 43 , further comprising, on a % by mass basis, at least one element selected from the group consisting of REM: from about 0.03% to about 0.10% and Zr: from about 0.05% to about 0.50%.
55. The exhaust system according to claim 21 , wherein regarding the state of Mo in the steel, a ratio of (112) diffraction intensity of the Laves phase, (Fe,Cr) 2 (Mo,Nb), to (111) diffraction intensity of Nb carbonitride, Nb(C,N), A value=I{(Fe,Cr) 2 (Mo,Nb)} (112) /I{Nb(C,N)} (111) , is less than 0.4 based on X-ray diffraction of extraction residues of precipitates in the steel.