US 11,702,717 B2
Martensitic stainless steel and method for producing the same
Pierre-Olivier Santacreu, Isbergues (FR); Coralie Parrens, Bethune (FR); and Jean-Benoît Moreau, Fille (FR)
Assigned to APERAM, Luxembourg (LU)
Appl. No. 16/761,158
Filed by APERAM, Luxembourg (LU)
PCT Filed Nov. 3, 2017, PCT No. PCT/IB2017/056865
§ 371(c)(1), (2) Date May 1, 2020,
PCT Pub. No. WO2019/086934, PCT Pub. Date May 9, 2019.
Prior Publication US 2020/0270718 A1, Aug. 27, 2020
Int. Cl. C21D 9/46 (2006.01); C21D 8/02 (2006.01); C21D 6/00 (2006.01); C21D 1/42 (2006.01); C22C 38/54 (2006.01); C22C 38/48 (2006.01); C22C 38/44 (2006.01); C22C 38/42 (2006.01); C22C 38/04 (2006.01); C22C 38/00 (2006.01)
CPC C21D 9/46 (2013.01) [C21D 1/42 (2013.01); C21D 6/004 (2013.01); C21D 6/005 (2013.01); C21D 6/008 (2013.01); C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C21D 8/0263 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/04 (2013.01); C22C 38/42 (2013.01); C22C 38/44 (2013.01); C22C 38/48 (2013.01); C22C 38/54 (2013.01); C21D 2211/004 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01)] 26 Claims
 
1. Martensitic stainless steel, wherein its composition is, in weight percentages:
0.05%≤C≤0.30%;
0.20%≤Mn≤2.0%;
traces %≤Si≤1.0%;
0.20%≤Mn+Si≤1.5%;
traces≤S≤0.01%, with 0≤10,000×Mn×S≤40;
traces≤P≤0.04%;
10.5%≤Cr≤17.0%, with [Cr−10.3−80×(C+N)2]≤(Mn+Ni);
traces≤Ni≤4.0%;
traces≤Mo<2.0%;
traces≤Mo+2W<2.0%;
traces≤Cu≤2.0%;
traces≤Ti≤0.5%;
traces≤V≤0.3%;
traces≤Zr≤0.5%;
traces≤Al≤0.2%;
traces≤O≤400 ppm;
traces≤Ta≤0.3%;
traces≤Nb≤0.3%;
0.25≤(Nb+Ta)/(C+N)≤8;
Nb≥[1.2 (C+N)−0.1]%;
0.009%≤N≤0.2%;
traces≤Co≤2.0%;
traces≤Cu+Co≤2.0%;
traces≤Cu+Co+Ni≤4.0%;
traces≤B≤0.1%;
traces≤H≤0.0005%;
traces≤rare earths≤0.06%, rare earths including Y;
traces≤Ca≤20 ppm;
the remainder being iron and impurities resulting from the processing;
and its microstructure comprises at least 75% martensite, less than 20% ferrite and at least 0.0001% and at most 0.5% carbides, the size of the ferrite grains being between 4 and 80 μm.