公开(公告)号：US11345982B2

公开(公告)日：2022-05-31

申请号：US16330655

申请日：2017-09-20

申请人： NIPPON STEEL & SUMITOMO METAL CORPORATION

发明人： Tatsuya Iwasaki ,  Koji Watari ,  Hidekazu Sueno

IPC分类号： C22C38/06 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/26 ,  C22C38/54 ,  C22C38/60 ,  F16C3/02 ,  C21D1/10 ,  C21D1/28 ,  C21D9/28

摘要： A shaft part excellent in static torsional strength and torsional fatigue strength containing, by mass %, essential elements of C: 0.35 to 0.70%, Si: 0.01 to 0.40%, Mn: 0.5 to 2.6%, P: 0.050% or less, S: 0.005 to 0.020%, Al: 0.010 to 0.050%, N: 0.005 to 0.025%, and O: 0.003% or less, further containing optional elements, having a balance of Fe and impurities, having a chemical composition satisfying formula (1), having at least one hole at an outer circumferential surface, having a volume ratio (R1) of 4 to 20% of retained austenite at a position of a 2 mm depth from the outer circumferential surface, having a volume ratio of retained austenite at a position of a 2 mm depth from the outer circumferential surface in an axial direction of the hole and at a position of a 20 μm depth from the surface of the hole as R2, and having a reduction rate Δγ of 40% or more of retained austenite found by the formula (A): Δγ=[(R1−R2)/R1]×100: Formula (1): 15.0≤25.9C+6.35Mn+2.88Cr+3.09Mo+2.73Ni≤27.2 (Notations of elements in formula are contents of the elements).

公开(公告)号：US11421727B2

公开(公告)日：2022-08-23

申请号：US16331468

申请日：2017-09-20

申请人： NIPPON STEEL & SUMITOMO METAL CORPORATION

发明人： Tatsuya Iwasaki ,  Koji Watari ,  Hidekazu Sueno

IPC分类号： F16C3/02 ,  C21D1/06 ,  C21D9/28 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/20 ,  C22C38/22 ,  C22C38/24 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38 ,  C22C38/58 ,  C23C8/22

摘要： A carburized shaft part having a predetermined composition, a C content at a surface layer part of a mass % of 0.60 to 1.00%, at least one hole at an outer circumferential surface, a total volume ratio of martensite and retained austenite of 97% or more at a structure at a position of a 1 mm depth from the outer circumferential surface in an axial direction of the hole and a position of a 20 μm depth from the surface of the hole, a maximum retained austenite volume ratio (R1) of 10.0 to 30.0% at a position of a 1 mm depth from the outer circumferential surface in the axial direction of the hole and a range up to a 200 μm depth from the surface of the hole, and a retained austenite reduction ratio of 20% or more found from R1 and the retained austenite volume ratio (R2) at a position of a 1 mm depth from the outer circumferential surface in the axial direction of the hole and a position of a 20 μm depth from the surface of the hole by the formula (A): Δγ=(R1−R)/R1×100.