Austenitic stainless steel and method for producing the same

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Quick Facts

Patent No.: US 10,316,383
App. No.: 15/303,532
Granted: Jun 11, 2019
Kind: B2

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Abstract

There is provided an austenitic stainless steel having a high strength and an excellent hydrogen brittleness resistance and further having an excellent machinability. The austenitic stainless steel of the present embodiment has a chemical composition including: in mass %, C: 0.10% or less; Si: 1.0% or less; Mn: 2.1 to 6.0%; P: 0.045% or less; S: 0.1% or less; Ni: 8.0 to 16.0%; Cr: 15.0 to 30.0%; Mo: 1.0 to 5.0%; N: 0.05 to 0.45%; Nb: 0 to 0.50%; and V: 0 to 0.50%, with the balance being Fe and impurities, and satisfying Formula (1). The austenitic stainless steel of the present embodiment has a grain size number of less than 8.0 and a tensile strength of 690 MPa or more. 15≤12.6C+1.05Mn+Ni+15N (1)

Claims (66)

1. An austenitic stainless steel comprising a chemical composition consisting of, in mass %:

C: 0.10% or less;

Si: 1.0% or less;

Mn: 2.1 to 6.0%;

P: 0.045% or less;

S: 0.1% or less;

Ni: 8.0 to 16.0%;

Cr: 15.0 to 30.0%;

Mo: 1.0 to 5.0%;

N: 0.05 to 0.45%;

Nb: 0 to 0.50%; and

V: 0 to 0.50%,

with the balance being Fe and impurities, and

satisfying Formula (1),

the austenitic stainless steel having a grain size number of 4.0 to less than 8.0 and a tensile strength, at a normal temperature, of 690 MPa or more:

15≤12.6C+1.05Mn+Ni+15N (1)

where symbols of elements in Formula (1) are to be substituted by contents of the corresponding elements (in mass %).

2. The austenitic stainless steel according to claim 1 , comprising one or more elements selected from the group consisting of

Nb: 0.01 to 0.50% and

V: 0.01 to 0.50%.

3. The austenitic stainless steel according to claim 1 , wherein a mixed grain ratio of a crystal grain micro-structure is 20% or less.

4. The austenitic stainless steel according to claim 2 , wherein a mixed grain ratio of a crystal grain micro-structure is 20% or less.

5. The austenitic stainless steel according to claim 1 , wherein a starting material having the chemical composition is subjected to hot working one or a plurality of times, and after last heating, subjected to hot working at a reduction in area of 70% or less.

6. The austenitic stainless steel according to claim 2 , wherein a starting material having the chemical composition is subjected to hot working one or a plurality of times, and after last heating, subjected to hot working at a reduction in area of 70% or less.

7. The austenitic stainless steel according to claim 3 , wherein a starting material having the chemical composition is subjected to hot working one or a plurality of times, and after last heating, subjected to hot working at a reduction in area of 70% or less.

8. The austenitic stainless steel according to claim 4 , wherein a starting material having the chemical composition is subjected to hot working one or a plurality of times, and after last heating, subjected to hot working at a reduction in area of 70% or less.

9. A method for producing the austenitic stainless steel according to claim 1 , comprising:

a step of preparing a starting material having the chemical composition; and