US 2008/0156400 A1 · Low alloy steel

Abstract

According to a low alloy steel of the present invention, compositional elements thereof are limited, and a metal structure thereof comprises bainite or martensite. Further, a proper amounts of Nd inclusions are formed by appropriately selecting timings of deoxidation and Nd addition in melting a steel. Consequently, compatibility between high-temperature creep strength and long-term creep ductility, which is hardly established in conventional steels, can be achieved even in hostile conditions. Accordingly, the low alloy steel of the present invention can be widely applied as the material for the heat-resistant structural member used for a long time under the high-temperature and high-pressure conditions such as power plant boilers, turbines, and nuclear power plants.

Claims2

Dependent claims

A low alloy steel, comprising, in terms of mass %, C:

0.05 to 0.15%, Si:
0.05 to 0.70%, Mn:
1.50% or less, P:
0.020% or less, S:
0.010% or less, Cr:
0.8 to 8.0%, Mo:
0.01 to 1.00%, Nd:
0.001 to 0.10.0% o, sol. Al:
0.020% or less, N, 0.015% or less and 0 (oxygen):
0.0050% or less, the balance being Fe and impurities, wherein a metal structure thereof comprises bainite or martensite, and wherein inclusions containing Nd are formed therein in the range of 0.1 μm to 10 μm in terms of size;
and wherein the number of inclusions per 1000 μm2 ranges 10 to 1000.

8 more elements

Dependencies are inferred from the claim text.

Facts

Application

12/073,324Filed 4 Mar 2008

Priority

JP 2005-2582866 Sep 2005

Published

3 Jul 2008

Term ends

Not estimatedThe source records don’t support an estimate.

Classification8 codes

C21C 7/0006
Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00: adding metallic additives
C21C 7/06
Removing impurities by adding a treating agent: deoxidising, e.g. killing
C22C 38/005
Ferrous alloys, e.g. steel alloys: containing rare earths, i.e. Sc, Y, Lanthanides
C22C 38/02
Ferrous alloys, e.g. steel alloys: containing silicon

Low alloy steel

Life of this patent

Low alloy steel

Life of this patent

Abstract

Claims2