Forging steel

Patent metadata

Field	Value
Publication number	US-9657379-B2
Application number	US-31201008-A
Country	US
Kind code	B2
Filing date	Apr 10, 2008
Priority date	Apr 11, 2007
Publication date	May 23, 2017
Grant date	May 23, 2017

Abstract

This invention provides a forging steel excellent in forgeability, which forging steel comprises, in mass %, C: 0.001 to less than 0.07%, Si: 3.0% or less, Mn: 0.01 to 4.0%, Cr: 5.0% or less, P: 0.2% or less, S: 0.35% or less, Al: 0.0001 to 2.0%, N: 0.03% or less, one or both of Mo: 1.5% or less (including 0%) and Ni: 4.5% or less (including 0%), and a balance of iron and unavoidable impurities; wherein Di given by the following Equation (1) is 60 or greater:

Di =5.41× Di (Si)× Di (Mn)× Di (Cr)× Di (Mo)× Di (Ni)× Di (Al)  (1)

First claim

What is claimed is:

1. A forging steel consisting of, in mass %:
C: 0.001 to less than 0.03%,
Si: 3.0% or less,
Mn: 0.01 to 4.0%,
Cr: 5.0% or less,
P: 0.2% or less,
S: 0.35% or less,
Al: greater than 0.06 to 2.0%,
N: 0.03% or less,
B: not less than BL given by Equation (7) below and not greater than 0.008%,
Ti: 0.005 to 0.15%, and
Mg: 0.0002 to 0.003%,
one or both of Mo: 1.5% or less (including 0%) and Ni: 4.5% or less (including 0%), and
a balance of iron and unavoidable impurities; and
optionally, one or more of Nb, V, Te, Ca, Zr, and REM;

wherein Di given by the following Equation (3) is 60 or greater:
Di= 5.41× Di (Si)× Di (Mn)× Di (Cr)× Di (Mo)× Di (Ni)× Di (Al)×1.976  (3),

where
Di(Si)=0.7×[% Si]+1,
Di(Mn)=3.335×[% Mn]+1 when Mn≦1.2%,
Di(Mn)=5.1×[% Mn]−1.12 when 1.2%<Mn,
Di(Ni)=0.3633×[% Ni]+1 when Ni≦1.5%,
Di(Ni)=0.442×[% Ni]+0.8884 when 1.5%<Ni≦1.7%,
Di(Ni)=0.4×[% Ni]+0.96 when 1.7%<Ni≦1.8%,
Di(Ni)=0.7×[% Ni]+0.42 when 1.8%<Ni≦1.9%,
Di(Ni)=0.2867×[% Ni]+1.2055 when 1.9%<Ni,
Di(Cr)=2.16×[% Cr]+1,
Di(Mo)=3×[% Mo]+1,
Di(Al)=1 when Al≦0.05%, and
Di(Al)=4×[% Al]+1 when 0.05%<Al,
wherein BL= 0.0004+10.8/14×([% N]−14/47.9×[% Ti])  (7)

where
([% N]−14/47.9×[% Ti]) of less than 0 is treated as 0,

a symbol in brackets [ ] indicating content (mass %) of the element concerned, and wherein a deformation resistance at room temperature is not more than 563 MPa.

2. The forging steel according to claim 1 , wherein one or more of Nb, V, Te, Ca, Zr, and REM is present in the following amounts:
Nb: 0.005 to 0.1%,
V: 0.01 to 0.5%,
Te: 0.0002 to 0.003%,
Ca: 0.0003 to 0.003%,
Zr: 0.0003 to 0.005%, and
REM: 0.0003 to 0.005%.

Assignees

• Saitoh Hajime
• Ochi Tatsuro
• Hashimura Masayuki
• Nippon Steel & Sumitomo Metal Corp

Inventors

• Saitoh Hajime
• Ochi Tatsuro
• Hashimura Masayuki

Classifications

• C22C38/06

  containing aluminium · CPC title

• C22C38/04 Primary

  containing manganese · CPC title

• C22C38/001

  containing N · CPC title

• C22C38/38

  with more than 1.5% by weight of manganese · CPC title

• C21D1/06

  Surface hardening · CPC title