High toughness steel material and method of producing steel pipes using same

• US 20030178111A1
• Filed: 04/22/2003
• Published: 09/25/2003
• Est. Priority Date: 08/02/2001
• Status: Active Grant

• Current Assignee: Nippon Steel Corporation
• Original Assignee: Sumitomo Metal Industries Limited (Nippon Steel Corporation)
• Inventors: Nakamura, Shigeru, Omura, Tomohiko, Kawano, Kaori, Abe, Toshiharu
• Granted Patent: US 6,958,099 B2
• Time in Patent Office: Days
• US Class Current: 148/593
• CPC Class Codes: C21D 8/10 during manufacturing of tubular bodies
• CPC Class Codes: C22C 38/002 containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: C22C 38/22 with molybdenum or tungsten
• CPC Class Codes: C22C 38/28 with titanium or zirconium

Abstract

A steel material and a steel pipe made by using the same are provided which are to be used in severe oil well environments. Such a highly tough oil well steel pipe can be produced by rolling the base material, quenching the rolling product from the austenite region and tempering the same so that the relationship between the content of Mo [Mo] in the carbides precipitated at austenite grain boundaries and the austenite grain size (according to ASTM E 112) can be defined by the formula (a) given below. In this manner, steel pipes suited for use even under oil well environments becoming more and more severe can be produced while satisfying the requirements that the cost should be rationalized, the productivity improved and energy saved.

[Mo]≦exp(G−5)+5  (a)

Claims

1. A steel material having high toughness comprising

the content of Mo [Mo], by mass %, in the carbides precipitated at austenite grain boundaries satisfies the formula (a) given below:

[Mo]≦

exp(G−

5)+5 

 

(a)

where G is the austenite grain size number according to ASTM E 112.

2. A steel material having high toughness comprising

containing, by mass %, C:

0.17-0.32%, Si;

0.1-0.5%, Mn;

0.30-2.0%, P;

not more than 0.030%, S;

not more than 0.010%, Cr;

0.10-1.50%, Mo;

0.01-0.80%, sol. Al;

0.001-0.100%, B;

0.0001-0.0020% and N;

not more than 0.0070%; and

the content of Mo [Mo] in the carbides precipitated at austenite grain boundaries satisfies the formula (a) given below;

[Mo]≦

exp(G−

5)+5 

 

(a)

where G is the austenite grain size number according to ASTM E 112.

3. A steel material having high toughness comprising

containing, by mass %, C:

0.17-0.32%, Si;

0.1-0.5%, Mn;

0.30-2.0%, P;

not more than 0.030%, S;

not more than 0.010%, Cr;

0.10-1.50%, Mo;

0.01-0.80%, sol. Al;

0.001-0.100%, B;

0.0001-0.0020% and N;

not more than 0.0070% and further containing one or more of Ti;

0.005-0.04%, Nb;

0.005-0.04% and V;

0.03-0.30%; and

the content of Mo [Mo] in the carbides precipitated at austenite grain boundaries satisfies the formula (a) given below;

[Mo]≦

exp(G−

5)+5 

 

(a)

where G is the austenite grain size number according to ASTM E 112.

4. A steel material having high toughness comprising

containing, by mass %, C:

0.20-0.28%, Si;

0.1-0.5%, Mn;

0.35-1.4%, P;

not more than 0.015%, S;

not more than 0.005%, Cr;

0.15-1.20%, Mo;

0.10-0.80%, sol. Al;

0.001-0.050%, B;

0.0001-0.0020% and N;

not more than 0.0070% and further containing one or more of Ti;

0.005-0.04%, Nb;

0.005-0.04% and V;

0.03-0.30%; and

the content of Mo [Mo] in the carbides precipitated at austenite grain boundaries satisfied the formula (a) given below;

[Mo]≦

exp(G−

5)+5 

 

(a)

where G is the austenite grain size number according to ASTM E 112.

5. A method of producing highly tough steel pipes for oil wells, comprising rolling a steel which contains, by mass %, C:

0.17-0.32%, Si;

0.1-0.5%, Mn;

0.30-2.0%, P;

not more than 0.030%, S;

not more than 0.010%, Cr;

0.10-1.50%, Mo;

0.01-0.80%, sol. Al;

0.001-0.100%, B;

0.0001-0.0020% and N;

not more than 0.0070%; and

quenching the rolling product from the austenite region, wherein, after the subsequent tempering, the content of Mo [Mo] in the carbides precipitated at austenite grain boundaries satisfies the formula (a) given below;

[Mo]≦

exp(G−

5)+5 

 

(a)

where G is the austenite grain size number according to ASTM E 112.

6. A method of producing highly tough steel pipes for oil wells, comprising rolling a steel which contains, by mass %, C:

0.17-0.32%, Si;

0.1-0.5%, Mn;

0.30-2.0%, P;

not more than 0.030%, S;

not more than 0.010%, Cr;

0.10-1.50%, Mo;

0.01-0.80%, sol. Al;

0.001-0.100%, B;

0.0001-0.0020% and N;

not more than 0.0070% and further containing one or more of Ti;

0.005-0.04%, Nb;

0.005-0.04% and V;

0.03-0.30%; and

quenching the rolling product from the austenite region, wherein, after the subsequent tempering, the content of Mo [Mo] in the carbides precipitated at austenite grain boundaries satisfies the formula (a) given below;

[Mo]≦

exp(G−

5)+5 

 

(a)

where G is the austenite grain size number according to ASTM E 112.

7. A method of producing highly tough steel pipes for oil wells, comprising rolling a steel which contains, by mass %, C:

0.20-0.28%, Si;

0.1-0.5%, Mn;

0.35-1.4%, P;

not more than 0.015%, S;

not more than 0.005%, Cr;

0.15-1.20%, Mo;

0.10-0.80%, sol. Al;

0.001-0.050%, B;

0.0001-0.0020% and N;

not more than 0.0070% and further containing one or more of Ti;

0.005-0.04%, Nb;

0.005-0.04% and V;

0.03-0.30%; and

quenching the rolling product from the austenite region, wherein, after the subsequent tempering, the content of Mo [Mo] in the carbides precipitated at austenite grain boundaries satisfies the formula (a) given below;

[Mo]≦

exp(G−

5)+5 

 

(a)

where G is the austenite grain size number according to ASTM E 112.