Sumitomo Metal Industries, Inc.

Nippon Steel Sumitomo Metal Corporation

Usui Kokusai Sangyo Kaisha Limited

Keisuke Hitoshio

Kunio Kondo

Yuji Arai

Takashi Takano

Miyuki Yamamoto

Kenichi Beppu

Susumu Hirano

Hidetoshi Kurata

Kikuo Asada

Katsunori Nagao

Osamu Endo

There is provided a method for manufacturing a seamless steel pipe for line pipe, capable of improving the toughness of the seamless steel pipe for line pipe. A round billet having a chemical composition, by mass percent, of C: 0.02 to 0.15%, Si: at most 0.5%, and Mn: 0.5 to 2.5%, the balance being Fe and impurities, is heated. The heated round billet is piercing-rolled to produce a hollow shell. The hollow shell is elongated and rolled and sized to produce a seamless steel pipe. The seamless steel pipe is water cooled, and the water cooling is stopped when the temperature of the seamless steel pipe reaches at most 450&#xb0; C. The water-cooled seamless steel pipe is quenched, and the quenched seamless steel pipe is tempered.

Method for manufacturing seamless steel pipe for line pipe and seamless steel pipe for line pipe

A seamless steel pipe for line pipe having high strength and high toughness contains, by mass percent, C: 0.02 to 0.10%, Si: at most 0.5%, Mn: 0.5 to 2.0%, Al: 0.01 to 0.1%, P: at most 0.03%, S: at most 0.005%, Ca: at most 0.005%, and N: at most 0.007%, and further contains at least one selected from a group consisting of Ti: at most 0.008%, V: less than 0.06%, and Nb: at most 0.05%, the balance being Fe and impurities. A carbon equivalent Ceq defined by Formula (1) is at least 0.38, a content of Ti, V and Nb satisfies Formula (2), and the size of carbo-nitride containing at least one of Ti, V, Nb and Al is at most 200 nm,C=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15&#x2003;&#x2003;(1)Ti+V+Nb&#x3c;0.06&#x2003;&#x2003;(2).

Seamless steel pipe for line pipe and method for manufacturing the same

To provide a steel pipe as a fuel injection pipe with high material strength, high internal pressure limit free from fatigue failure, prolonged fatigue life, and high reliability. A steel pipe as a fuel injection pipe of 500 N/mmor higher tensile strength comprising, by mass, C: 0.12 to 0.27%, Si: 0.05 to 0.40%, and Mn: 0.8 to 2.0%, and the balance being Fe and impurities, the contents of Ca, P, and S in the impurities being Ca: 0.001% or less, P: 0.02% or less, and S: 0.01% or less, respectively, characterized in that the maximum diameter of nonmetallic inclusions present in at least in a region extending from the inner surface of the steel pipe to a depth of 20 &#x3bc;m is 20 &#x3bc;m or less. Further, this steel pipe may contain, in place of a portion of Fe, at least one selected from among Cr: 1% or less, Mo: 1% or less, Ti: 0.04% or less, Nb: 0.04% or less, and V: 0.1% or less.

Steel pipe as fuel injection pipe

In order to manufacture a steel pipe for an air bag which can cope with increase in the pressure of gas blown into an air bag and decreases in the wall thickness of an accumulator, a steel having a composition, mass %, of:

High strength steel pipe for an air bag

A steel pipe for an airbag inflator having a high strength of at least 900 MPa and preferably at least 1000 MPa in tensile strength along with a high toughness and exhibiting good resistance to bursting such that it has no propagation of cracks in a burst test at &#x2212;40&#xb0; C. or below is manufactured by quenching a pipe of a steel comprising, in mass %, C: 0.05-0.20 %, Si: 0.1-1.0 %, P: at most 0.025 %, S: at most 0.010 %, Cr: 0.05-1.45 %, Al: at most 0.10 %, and one or both of Ti and Mn satisfying Ti&#x2266;0.02% and 0.4%&#x2266;Mn+40Ti&#x2266;1.2% from a temperature of at least the Actransformation point of the steel, tempering the pipe at a temperature lower than the Actransformation point, applying cold working to it with a reduction of area of at most 65%, and subjecting it to stress relief annealing at a temperature lower than the Actransformation point. The ratio L/T of the X-ray integrated intensity ratio of the {110} plane measured for the cross section perpendicular to the axial direction L of the steel pipe to that measured for the cross section perpendicular to the circumferential direction T is at most 50.

Steel pipe for an airbag inflator and a process for its manufacture

In order to manufacture a steel pipe for an air bag which can cope with increase in the pressure of gas blown into an air bag and decreases in the wall thickness of an accumulator, a steel having a composition, mass %, of:  if necessary at least one of Mo: at most 0.50%, Ni: at most 1.5%, Cu: at most 0.5%, V: at most 0.2%, Ti: at most 0.1%, Nb: at most 0.1%, and B: at most 0.005%, and also if necessary, at least one of Ca: at most 0.01%, Mg: at most 0.01%, and REM (rare earth elements): at most 0.01%, and a remainder of Fe and impurities is used to produce a steel pipe, and the pipe is then subjected to cold working to predetermined dimensions, then to heating to a temperature of at least the Actransformation temperature followed by quenching, and then to tempering at a temperature no higher than the Actransformation temperature.

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Hannan, Japan

Keisuke Hitoshio