Steel for steam turbine blade with excellent strength and toughness

Patent metadata

Field	Value
Publication number	US-9416436-B2
Application number	US-201313869275-A
Country	US
Kind code	B2
Filing date	Apr 24, 2013
Priority date	Apr 27, 2012
Publication date	Aug 16, 2016
Grant date	Aug 16, 2016

Abstract

The present invention aim at providing a steel for steam turbine blades which is excellent in terms of strength and toughness. The steel of the present invention has a composition which contains, in terms of % by mass, 0.02-0.10% of C, up to 0.25% of Si, 0.001-0.10% of Mn, up to 0.010% of P, up to 0.010% of S, 8.5-10.0% of Ni, 10.5-13.0% of Cr, 2.0-2.5% of Mo, 0.001-0.010% of N, 1.15-1.50% of Al, less than 0.10% of Cu, up to 0.20% of Ti, and the remainder being incidental impurities and Fe, and which satisfies 6.0≦Ni/Al≦8.0, 9.0≦Nieq≦11.0 and 17.0≦Creq≦19.0, in which

Nieq=[Ni]+0.11[Mn]−0.0086([Mn] 2 )+0.44[Cu]+18.4[N]+24.5[C]

Creq=[Cr]+1.21[Mo]+0.48[Si]+2.2[Ti]+2.48[A1].

First claim

What is claimed is:

1. A steel for steam turbine blades which contains, in terms of % by mass,
0.02-0.10% of C,
up to 0.25% of Si,
0.001-0.10% of Mn,
up to 0.010% of P,
up to 0.010% of S,
8.8%-10% of Ni,
10.5-13.0% of Cr,
2.0-2.5% of Mo,
0.001-0.010% of N,
1.15-1.50% of Al,
less than 0.10% of Cu,
up to 0.20% of Ti, and
the remainder being incidental impurities and Fe, and which satisfies the following expression (1), expression (2), and expression (3):
6.0≦Ni/Al≦8.0  expression (1)

9.0≦Nieq≦11.0  expression (2)

17.0≦Creq≦19.0  expression (3)

wherein
Nieq=[Ni]+0.11[Mn]−0.0086([Mn] 2 )+0.44[Cu]+18.4[N]+24.5[C]

Creq=[Cr]+1.21[Mo]+0.48[Si]+2.2[Ti]+2.48[Al]
(wherein the atomic symbols in expression (1) and in the equations defining Nieq and Creq represent the contents in % by mass of the respective elements).

2. The steel for steam turbine blades of claim 1 , which contains an austenite phase.

Assignees

• Takabayashi Hiroyuki
• Ueta Shigeki
• Daido Steel Co Ltd

Inventors

• Takabayashi Hiroyuki
• Ueta Shigeki

Classifications

• C22C38/02

  containing silicon · CPC title

• C22C38/06

  containing aluminium · CPC title

• C21D9/0068

  for particular articles not mentioned below · CPC title

• C21D6/004

  containing Cr and Ni · CPC title

• C22C38/50 Primary

  with titanium or zirconium · CPC title