Nippon Steel Corporation

Nhk Spring Co., Ltd.

Nippon Steel Sumitomo Metal Corporation

Yukinobu Nagata

Eiji Tsuru

Yasuhiro Shinohara

Yuki Motegi

Yuji Araoka

Yuusuke Ichinose

Ken Ou

This electric resistance-welded steel tube for a hollow stabilizer is an electric resistance-welded steel tube for a hollow stabilizer including a base material portion and a weld, in which the base material portion has predetermined chemical components, a wall thickness of the base material portion is 2.0 to 6.0 mm, an outer diameter of the electric resistance-welded steel tube is 10 to 40 mm, in a C direction cross section of the electric resistance-welded steel tube, a recessed bead cut is present in a region including the weld on an inner surface side of the electric resistance-welded steel tube, when an imaginary line is drawn from one opening edge to the other opening edge of the bead cut in a shortest distance, a maximum depth from the imaginary line to a bottom of the bead cut is 300 μm or less, a maximum inclusion diameter that is included in the base material portion is 300 μm or less, in the base material portion of the electric resistance-welded steel tube, a surface roughness of the inner surface side is 300 μm or less in terms of a maximum profile valley depth Rv, and maximum hardness of the electric resistance-welded steel tube including the weld is 300 Hv or less.

Electric resistance-welded steel tube for hollow stabilizer, hollow stabilizer, and manufacturing methods of same

A collapse strength prediction method of a steel pipe includes deriving a prediction equation indicating a relationship among D/t obtained by dividing an outer diameter D (mm) by a thickness t (mm), material characteristics, a collapse strength dominant factor, and a collapse dominant proof stress (&#x3c3;) of the steel pipe using a plurality of reference steel pipes collapse whose strengths have been obtained in advance, obtaining D/t, material characteristics, a collapse strength dominant factor, and a predicted collapse strength of a steel pipe that is an evaluation subject, obtaining a compressive stress-strain curve in a circumferential direction of the steel pipe that is the evaluation subject, obtaining a stress that causes a permanent strain to be generated in the steel pipe that is the evaluation subject as the collapse dominant proof stress on the basis of the compressive stress-strain curve, and computing the predicted collapse strength of the steel pipe that is the evaluation subject from the D/t, the material characteristics, the collapse strength dominant factor, and the collapse dominant proof stress, which have been obtained, on the basis of the prediction equation, and the permanent strain is set according to a value of the D/t of the steel pipe that is the evaluation subject.

Collapse strength prediction method

A pipeline is a pipeline having plural weld zones in which ends of plural steel pipes are joined by welding, the plural steel pipes are produced from plural charges of molten steel having one or more steel compositions; yield point elongation is not present on a stress-strain curve obtained when stress is applied in a longitudinal direction of each of the steel pipes; a thickness of each of the steel pipes t (mm) and an average pipe outside-diameter D (mm) satisfy t/D&#xd7;100&#x2264;6; and in the plurality of the weld zones, &#x394;YS which is a yield strength difference between one steel pipe and the other steel pipe that are welded to each other (MPa), and YR representing a yield ratio that is a ratio of the yield strength to tensile strength of a pipe having a low yield strength out of the one steel pipe and the other steel pipe, satisfy &#x394;YS&#x2264;&#x2212;1.75&#xd7;YR+230.

Pipeline and manufacturing method thereof

A pipeline is a pipeline having plural weld zones in which ends of plural steel pipes are joined by welding, the plural steel pipes are produced from plural charges of molten steel having one or more steel compositions; yield point elongation is not present on a stress-strain curve obtained when stress is applied in a longitudinal direction of each of the steel pipes; a thickness of each of the steel pipes t (mm) and an average pipe outside-diameter D (mm) satisfy t/D&#xd7;100&#x2266;6; and in the plurality of the weld zones, &#x394;YS which is a yield strength difference between one steel pipe and the other steel pipe that are welded to each other (MPa), and YR representing a yield ratio that is a ratio of the yield strength to tensile strength of a pipe having a low yield strength out of the one steel pipe and the other steel pipe, satisfy &#x394;YS&#x2266;&#x2212;1.75&#xd7;YR+230.

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Tokyo, Japan

Yukinobu Nagata