Roughly-shaped steel material for nitrided part, and nitrided part

Patent metadata

Field	Value
Publication number	US-2022010416-A1
Application number	US-201917289237-A
Country	US
Kind code	A1
Filing date	Oct 29, 2019
Priority date	Oct 29, 2018
Publication date	Jan 13, 2022
Grant date	—

Abstract

Provided are a roughly-shaped steel material for a nitrided part, and a nitrided part obtained by nitriding the roughly-shaped steel material for a nitrided part, having a determined chemical composition, in which the portion with a diameter or width ranging from 60 to 130 mm of the roughly-shaped steel material for a nitrided part has a microstructure at a depth of 14.5 mm from a surface including, in terms of area fraction: tempered martensite and tempered bainite in total: from 70 to 100%; remaining austenite: from 0 to 5%; and a balance: ferrite and perlite; and has a microstructure at a depth of 15 mm or more from the surface including, in terms of area fraction: tempered martensite and tempered bainite in total: from 0 to less than 50%; remaining austenite: from 0 to 5%; and a balance: ferrite and perlite.

First claim

1 . A roughly-shaped material for a nitrided part having a portion with a diameter or width ranging from 60 to 130 mm, the roughly-shaped material for a nitrided part having a chemical composition comprising, by % by mass:
C: from 0.35 to 0.45%; Si: from 0.10 to 0.50%; Mn: from 1.5 to 2.5%; P: 0.05% or less; S: from 0.005 to 0.100%; Cr: from 0.15 to 0.60%; Al: from 0.001 to 0.080%; N: from 0.003 to 0.025%; Mo: from 0 to 0.50%; Cu: from 0 to 0.50%; Ni: from 0 to 0.50%; Ti: from 0 to 0.050%; Nb: from 0 to 0.050%; Ca: from 0 to 0.005%; Bi: from 0 to 0.30%; V: from 0 to 0.05%; and a balance comprising Fe and impurities; wherein the portion with a diameter or width ranging from 60 to 130 mm of the roughly-shaped material for a nitrided part has a microstructure at a depth of 14.5 mm from a surface comprising, in terms of area fraction:
tempered martensite and tempered bainite in total: from 70 to 100%;
remaining austenite: from 0 to 5%; and
a balance: ferrite and perlite; and
wherein the portion with a diameter or width ranging from 60 to 130 mm of the roughly-shaped material for a nitrided part has a microstructure at a depth of 15 mm or more from the surface comprising, in terms of area fraction:
tempered martensite and tempered bainite in total: from 0 to less than 50%;
remaining austenite: from 0 to 5%; and
a balance: ferrite and perlite.

2 . The roughly-shaped material for a nitrided part according to claim 1 , comprising, by % by mass, one or more of:
Mo: from more than 0 to 0.50%; Cu: from more than 0 to 0.50%; or Ni: from more than 0 to 0.50%.

3 . The roughly-shaped material for a nitrided part according to claim 1 , comprising, by % by mass, one or two of:
Ti: from more than 0 to 0.050%; or Nb: from more than 0 to 0.050%.

4 . The roughly-shaped material for a nitrided part according to claim 1 , comprising, by % by mass, one or more of:
Ca: from more than 0 to 0.005%; Bi: from more than 0 to 0.30%, or V: from 0 to 0.05%.

5 . A nitrided part using, as a material, the roughly-shaped material for a nitrided part according to claim 1 ,
wherein the portion with a diameter or width ranging from 60 to 130 mm of the nitrided part has a microstructure at a depth of 0.5 mm from the surface comprising, in terms of area fraction:
tempered martensite and tempered bainite in total: from 70 to 100%;
remaining austenite: from 0 to 5%; and
a balance: ferrite and perlite;
wherein the portion with a diameter or width ranging from 60 to 130 mm of the nitrided part has a microstructure at a depth of 15 mm or more from the surface comprising, in terms of area fraction:
tempered martensite and tempered bainite in total: from 0 to less than 50%;
remaining austenite: from 0 to 5%; and
a balance: ferrite and perlite; and
wherein the portion with a diameter or width ranging from 60 to 130 mm of the nitrided part has a Vickers hardness at a depth of 0.05 mm from the surface of from 350 to 550 HV.

6 . The nitrided part according to claim 5 ,
comprising, in the portion with a diameter or width ranging from 60 to 130 mm of the nitrided part, a single hole or a plurality of holes having L/D, which is a ratio of a depth L to a diameter D, of 8 or more, with the depth L being 60 mm or more; wherein 50% or more of a total length of each hole in a depth direction passes through a portion having a microstructure comprising, in terms of area fraction:
tempered martensite and tempered bainite in total: from 0 to less than 50%;
remaining austenite: from 0 to 5%; and
a balance: ferrite and perlite.

7 . The roughly-shaped material for a nitrided part according to claim 2 , comprising, by % by mass, one or two of:
Ti: from more than 0 to 0.050%; or Nb: from more than 0 to 0.050%.

8 . The roughly-shaped material for a nitrided part according to claim 2 , comprising, by % by mass, one or more of:
Ca: from more than 0 to 0.005%; Bi: from more than 0 to 0.30%, or V: from 0 to 0.05%.

9 . The roughly-shaped material for a nitrided part according to claim 3 , comprising, by % by mass, one or more of:
Ca: from more than 0 to 0.005%; Bi: from more than 0 to 0.30%, or V: from 0 to 0.05%.

10 . The nitrided part according to claim 5 ,
wherein the roughly-shaped material for a nitrided part comprising, by % by mass, one or more of: Mo: from more than 0 to 0.50%; Cu: from more than 0 to 0.50%; or Ni: from more than 0 to 0.50%.

11 . The nitrided part according to claim 6 ,
wherein the roughly-shaped material for a nitrided part comprising, by % by mass, one or more of: Mo: from more than 0 to 0.50%; Cu: from more than 0 to 0.50%; or Ni: from more than 0 to 0.50%.

12 . The nitrided part according to claim 5 ,
wherein the roughly-shaped material for a nitrided part comprising, by % by mass, one or two of: Ti: from more than 0 to 0.050%; or Nb: from more than 0 to 0.050%.

13 . The nitrided part according to claim 6 ,
wherein the roughly-shaped material for a nitrided part comprising, by % by mass, one or two of: Ti: from more than 0 to 0.050%; or Nb: from more than 0 to 0.050%.

14 . The nitrided part according to claim 10 ,
wherein the roughly-shaped material for a nitrided part comprising, by % by mass, one or two of: Ti: from more than 0 to 0.050%; or Nb: from more than 0 to 0.050%.

15 . The nitrided part according to claim 11 ,
wherein the roughly-shaped material for a nitrided part comprising, by % by mass, one or two of: Ti: from more than 0 to 0.050%; or Nb: from more than 0 to 0.050%.

16 . The nitrided part according to claim 5 ,
wherein the roughly-shaped material for a nitrided part comprising, by % by mass, one or more of: Ca: from more than 0 to 0.005%; Bi: from more than 0 to 0.30%, or V: from 0 to 0.05%.

17 . The nitrided part according to claim 6 ,
wherein the roughly-shaped material for a nitrided part comprising, by % by mass, one or more of: Ca: from more than 0 to 0.005%; Bi: from more than 0 to 0.30%, or V: from 0 to 0.05%.

18 . The nitrided part according to claim 10 ,
wherein the roughly-shaped material for a nitrided part comprising, by % by mass, one or more of: Ca: from more than 0 to 0.005%; Bi: from more than 0 to 0.30%, or V: from 0 to 0.05%.

19 . The nitrided part according to claim 11 ,
wherein the roughly-shaped material for a nitrided part comprising, by % by mass, one or more of: Ca: from more than 0 to 0.005%; Bi: from more than 0 to 0.30%, or V: from 0 to 0.05%.

20 . The nitrided part according to claim 12 ,
wherein the roughly-shaped material for a nitrided part comprising, by % by mass, one or more of: Ca: from more than 0 to 0.005%; Bi: from more than 0 to 0.30%, or V: from 0 to 0.05%.

Assignees

• Nippon Steel Corp

Inventors

• Yuya Masato
• Tahira Hiroaki
• Nishihara Kison
• Okawa Satoru

Classifications

• C22C38/40 Primary

  with nickel · CPC title

• C22C38/26

  with niobium or tantalum · CPC title

• C23C8/38

  Treatment of ferrous surfaces · CPC title

• C22C38/06

  containing aluminium · CPC title

• C22C38/20

  with copper · CPC title