Jfe Steel Corporation

Hiromichi Hori

Takatoshi Okabe

Shinsaku Kokubo

Yoshikazu Kawabata

Shunsuke Toyoda

Masatoshi Aratani

Kenichi Iwazaki

Ryoji Matsui

Hiroshi Nakata

Tomonori Kondo

There are provided an electric resistance welded steel pipe for producing a high strength hollow stabilizer excellent in fatigue resistance and a high strength hollow stabilizer. In an electric resistance welded steel pipe () for producing a hollow stabilizer, an internal weld bead cut portion () has a three-peak shape and a depth (H) of a trough portion () of the three-peak shape is 0.3 mm or less and an angle (&#x3b8;) formed by a central portion in the circumferential direction of the trough portion () and the top of right and left peak portions () located on both the right and left sides of the trough portion () is 160&#xb0; or more and less than 180&#xb0;.

Electric resistance welded steel pipe for producing hollow stabilizer, hollow stabilizer, and production methods for same

A method for manufacturing an electric resistance welded steel tube for high-strength thin hollow stabilizers is provided. A steel with a certain chemical composition is heated to a temperature of 1000 to 1300&#xb0; C., hot rolled under conditions where the rolling finish temperature is 750 to 950&#xb0; C., cooled, coiled into a coil at 500 to 650&#xb0; C., and skin pass rolled with a rolling reduction ratio of not less than 0.3%. The resultant hot rolled sheet is electric resistance welded into an electric resistance welded steel tube, which is then reheated to a temperature of 800 to 1100&#xb0; C. and hot stretch-reducing rolled under conditions where the rolling finish temperature is not more than 850&#xb0; C. and the cumulative diameter reduction is not more than 75%. Consequently, a thin electric resistance welded steel tube is produced.

Electric resistance welded steel tubes for high-strength thin hollow stabilizers, and methods for manufacturing the same

A method for manufacturing an electric resistance welded steel pipe having an identifiable seam portion. The method includes electric resistance welding a steel pipe, cutting an inner surface bead and an outer surface bead of the steel pipe in such a manner so as to cut: (i) a whole the outer surface bead and a part of the inner surface bead to leave an uncut portion in the inner surface bead, or (ii) a whole of the inner surface bead and a part of the outer surface bead to leave an uncut portion in the outer surface bead, coating the steel pipe with zinc phosphate, and cold drawing the steel pipe using a plug and a die to make the seam portion of the steel pipe identifiable.

Electric resistance welded steel pipe having identifiable seam portion and method for manufacturing the same

An electric resistance welded steel pipe having an identifiable seam portion and a method for manufacturing the same. The electric resistance welded steel pipe includes a steel pipe portion with a seam portion, which is formed by electric resistance welding, and a coating portion of zinc phosphate. The coating portion covers at least an outer surface side of the steel pipe portion. A part of the coating portion that is immediately above the seam portion forms a color difference portion that has a width W along a pipe circumferential direction of greater than or equal to 0.1 times a wall thickness of the pipe and less than or equal to the wall thickness of the pipe. The color difference portion has a visually identifiable color difference from the other parts of the coating portion.

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Tokyo, Japan

Hiromichi Hori