Low alloy oil-well steel pipe

Patent metadata

Field	Value
Publication number	US-10563793-B2
Application number	US-201515328087-A
Country	US
Kind code	B2
Filing date	Jul 21, 2015
Priority date	Jul 25, 2014
Publication date	Feb 18, 2020
Grant date	Feb 18, 2020

Abstract

Provided is a low alloy oil-well steel pipe having a yield strength of 827 MPa or more, and an excellent SSC resistance. The low alloy oil-well steel pipe according to the present invention consisting of: in mass %, C: more than 0.35 to 0.65%; Si: 0.05 to 0.50%; Mn: 0.10 to 1.00%; Cr: 0.40 to 1.50%; Mo: 0.50 to 2.00%; V: 0.05 to 0.25%; Nb: 0.01 to 0.040%; sol.Al: 0.005 to 0.10%; N: 0.007% or less; Ti: 0 to 0.012%; Ca: 0 to 0.005%; and a balance being Fe and impurities, the impurities including: P: 0.020% or less; S: 0.002% or less; O: 0.006% or less; Ni: 0.10% or less; Cu: 0.03% or less; and B: 0.0005% or less, wherein in a microstructure, a number of cementite particles each of which has an equivalent circle diameter of 200 nm or more is 200 particles/100 μm2 or more, and a yield strength is 827 MPa or more.

First claim

The invention claimed is:

1. A low alloy oil-well steel pipe having a chemical composition consisting of:
in mass %,
C: more than 0.35 to 0.65%;
Si: 0.05 to 0.50%;
Mn: 0.10 to 1.00%;
Cr: 0.40 to 1.50%;
Mo: 0.50 to 2.00%;
V: 0.05 to 0.25%;
Nb: 0.01 to 0.04%;
sol.Al: 0.005 to 0.10%;
N: 0.007% or less;
Ti: 0 to 0.012%;
Ca: 0 to 0.005%; and
a balance being Fe and impurities,
the impurities including:
P: 0.020% or less;
S: 0.002% or less;
O: 0.006% or less;
Ni: 0.10% or less;
Cu: 0.03% or less; and
B: 0.0005% or less,
wherein
in a microstructure, a number of cementite particles each of which has an equivalent circle diameter of 200 nm or more is 200 particles/100 μm 2 or more
and
a yield strength is 827 MPa or more.

2. The low alloy oil-well steel pipe according to claim 1 , wherein the Ti content is
0.003 to 0.012%.

3. The low alloy oil-well steel pipe according to claim 2 , wherein the Ca content is
0.0005 to 0.005%.

4. The low alloy oil-well steel pipe according to claim 1 , wherein the Ca content is
0.0005 to 0.005%.

Assignees

• Nippon Steel & Sumitomo Metal Corp
• Nippon Steel Corp

Inventors

• Kondo Keiichi
• Arai Yuji

Classifications

• C21D2211/008

  Martensite · CPC title

• C22C38/02

  containing silicon · CPC title

• C22C38/54

  with boron · CPC title

• C22C38/06

  containing aluminium · CPC title

• C22C38/44

  with molybdenum or tungsten · CPC title