Method for producing high elastic limit nonmagnetic steel material using an austenitic stainless steel sheet
[Problem] To provide a raw material steel sheet for providing a high strength nonmagnetic austenitic stainless steel material that has a high elastic limit stress and excellent toughness. [Solution to Problem] An austenitic stainless steel sheet containing 0.12% or less of C, from 0.30 to 3.00% of Si, from 2.0 to 9.0% of Mn, from 7.0 to 15.0% of Ni, from 11.0 to 20.0% of Cr, and 0.30% or less of N, and further containing at least one kind of 3.0% or less of Mo, 1.0% or less of V, 1.0% or less of Nb, 1.0% or less of Ti, and 0.010% or less of B, all in terms of percentage by mass, with the balance of Fe and unavoidable impurities, having a component composition having a Ni equivalent of 19.0 or more, having a value of d −1/2 of 0.40 or more, wherein d (μm) represents an average austenitic crystal grain diameter, and having a property that provides a magnetic permeability μ of 1.0100 or less after subjected to cold rolling with an equivalent strain of 0.50 or more.
1. A method for producing a high elastic limit nonmagnetic stainless steel material that is excellent in toughness, comprising:
subjecting an austenitic stainless steel sheet consisting of 0.02 to 0.09% of C, from 0.30 to 3.00% of Si, from 2.0 to 9.0% of Mn, from 7.0 to 14.0% of Ni, from 16.0 to 20.0% of Cr, and from 0.02 to 0.30% of N, all in terms of percentage by mass, with the balance of Fe and unavoidable impurities, having a component composition having a Ni equivalent defined by the following expression (1) of 19.0 or more to hot rolling, cold rolling, and annealing at a temperature of from 700° C. or more to 1000° C. or less to provide a value of d −1/2 (μm −1/2 ) of 0.40 or more, wherein d (μm) represents an average austenitic crystal grain diameter, then
subjecting the stainless steel sheet to cold rolling at a rolling reduction ratio of 40% or more to provide a magnetic permeability μ of 1.0100 or less, and then
subjecting the stainless steel sheet to an aging treatment at an aging temperature of from 300 to 600° C. under a condition that satisfies the following expression (4):
Ni equivalent=Ni+0.6Mn+9.69(C+N)+0.18Cr−0.11Si 2 (1)
13,000< T (log t+ 20)<16,500 (4)
wherein T represents the aging temperature in K in terms of absolute temperature, and t represents the aging time in h.
2. A method for producing a high elastic limit nonmagnetic stainless steel material that is excellent in toughness, comprising:
subjecting an austenitic stainless steel sheet consisting of 0.02 to 0.09% of C, from 0.30 to 3.00% of Si, from 2.0 to 9.0% of Mn, from 7.0 to 14.0% of Ni, from 16.0 to 20.0% of Cr, and from 0.02 to 0.30% of N, and further comprising at least one kind of 3.0% or less of Mo, 1.0% or less of Nb, 1.0% or less of Ti, and 0.010% or less of B, all in terms of percentage by mass, with the balance of Fe and unavoidable impurities, having a component composition having a Ni equivalent defined by the following expression (3) of 19.0 or more to hot rolling, cold rolling, and annealing at a temperature of from 700° C. or more to 1000° C. or less to provide a value of d −1/2 (μm −1/2 ) of 0.40 or more, wherein d (μm) represents an average austenitic crystal grain diameter, then
subjecting the austenitic stainless steel sheet to cold rolling at a rolling reduction ratio of 40% or more to provide a magnetic permeability μ of 1.0100 or less, and then
subjecting the austenitic stainless steel sheet to an aging treatment at an aging temperature of from 300 to 600° C. under a condition that satisfies the following expression (4):
Ni equivalent=Ni+0.6Mn+9.69(C+N)+0.18Cr−0.11Si 2 +0.6Mo+2.3(V+Nb+Ti) (3)
13,000< T (log t+ 20)<16,500 (4)
wherein T represents the aging temperature in K in terms of absolute temperature, and t represents the aging time in h.
3. The method for producing a high elastic limit nonmagnetic stainless steel material according to claim 1 , wherein the annealing temperature is from 700° C. or more to 900° C. or less.
4. The method for producing a high elastic limit nonmagnetic stainless steel material according to claim 2 , wherein the annealing temperature is from 700° C. or more to 900° C. or less.
5. The method for producing a high elastic limit nonmagnetic stainless material according to claim 1 , wherein the stainless steel has a property that provides an increment of elastic limit stress σ 0.01 before and after an aging treatment of 150 N/mm 2 or more.
6. The method for producing a high elastic limit nonmagnetic stainless material according to claim 2 , wherein the stainless steel has a property that provides an increment of elastic limit stress σ 0.01 before and after an aging treatment of 150 N/mm 2 or more.
7. The method for producing a high elastic limit nonmagnetic stainless steel material according to claim 3 , wherein the stainless steel has a property that provides an increment of elastic limit stress σ 0.01 before and after an aging treatment of 150 N/mm 2 or more.
8. The method for producing a high elastic limit nonmagnetic stainless steel material according to claim 4 , wherein the stainless steel has a property that provides an increment of elastic limit stress σ 0.01 before and after an aging treatment of 150 N/mm 2 or more.
9. A method for producing a high elastic limit nonmagnetic stainless steel material that is excellent in toughness, comprising:
subjecting an austenitic stainless steel sheet consisting of from 0.02 to 0.09% of C, from 0.30 to 3.00% of Si, from 2.0 to 9.0% of Mn, from 7.0 to 14.0% of Ni, from 16.0 to 20.0% of Cr, and from 0.02 to 0.30% of N, and 1.0% or less of V, all in terms of percentage by mass, with the balance of Fe and unavoidable impurities, having a component composition having a Ni equivalent defined by the following expression (3) of 19.0 or more, to hot rolling, cold rolling, and annealing at an annealing temperature of from 700° C. or more to 900° C. or less to provide a value of d −1/2 (μm −1/2 ) of 0.40 or more, wherein d in μm represents an average austenitic crystal grain diameter, then subjecting the stainless steel sheet to cold rolling at a rolling reduction ratio of 40% or more to provide a magnetic permeability μ of 1.0100 or less, and then
subjecting the stainless steel sheet to an aging treatment at an aging temperature of from 300 to 600° C. under a condition that satisfies the following expression (4):
Ni equivalent=Ni+0.6Mn+9.69(C+N)+0.18Cr−0.11Si 2 +0.6Mo+2.3(V+Nb+Ti) (3)
13,000< T (log t+ 20)<16,500 (4)
wherein T represents the aging temperature in K in terms of absolute temperature, and t represents the aging time in h.
10. The method for producing a high elastic limit nonmagnetic stainless steel material according to claim 9 , wherein the stainless steel has a property that provides an increment of elastic limit stress σ 0.01 before and after an aging treatment of 150 N/mm 2 or more.