Jfe Steel Corporation

Ryoji Matsui

Masatoshi Aratani

Tomonori Kondou

Yoshikazu Kawabata

Tomonori Kondo

Shinsaku Kokubo

Hiromichi Hori

Hiroshi Nakata

Kenichi Iwazaki

Kazutoshi Ishikawa

Provided is an electric-resistance-welded steel pipe or tube for a hollow stabilizer where the formation of not only a ferrite decarburized layer but also a total decarburization layer can be suppressed even when heat treatment is performed in the air. The electric-resistance-welded steel pipe or tube for a hollow stabilizer has a predetermined chemical composition, and the depths of total decarburized layers on an inner surface and on an outer surface are 100 μm or less.

Electric-resistance-welded steel pipe or tube for hollow stabilizer

Provided is an electric-resistance-welded steel pipe or tube for hollow stabilizer excellent in corrosion fatigue resistance having: a chemical composition containing, in mass %, C: 0.15% or more and less than 0.20%, Si: 0.1% or more and 1.0% or less, Mn: 0.1% or more and 2.0% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.01% or more and 0.10% or less, Ti: more than 0.05% and 0.1% or less, B: 0.0005% or more and 0.005% or less, Ca: 0.0001% or more and 0.0050% or less, and N: 0.0050% or less, with the balance being Fe and inevitable impurities; and a microstructure containing TiS and MnS particles which each have a particle size of 10 μm or more, the TiS and MnS particles having a cleanliness of 0% or more and 0.1% or less as measured by a point counting method according to JIS G 0555.

Electric-resistance-welded steel pipe or tube for hollow stabilizer and method of manufacturing same

An electric resistance welded steel pipe for manufacturing a hollow stabilizer has a Lankford value in a pipe longitudinal direction of from 0.7 to less than 1.0. The electric resistance welded steel pipe is subjected to cold bending and then to a heat treatment including quenching and tempering to manufacture a stabilizer. The cold bending is cold rotary draw bending. When bent with a bend radius of from 1.0 times to 3.0 times an outer diameter of the pipe before cold bending, a flattening ratio is from 0% to 10%, a thickness reduction rate on a bending outside and a thickness increase rate on a bending inside are from 0% to 10%, and additionally, a circumferential length change of a bending center portion is from 0% to 10%. A Vickers hardness of the stabilizer after the heat treatment is adjusted to from 400 HV to less than 580 HV.

Electric-resistance-welded steel pipe for producing hollow stabilizer, hollow stabilizer, and method for producing same

Provided is an electric resistance welded steel pipe or tube that develops no quench cracks despite having carbon content of 0.40% or more and has excellent fatigue strength. An electric resistance welded steel pipe or tube comprises: a chemical composition containing, in mass %, C: 0.40% to 0.55%, Si: 0.10% to 1.0%, Mn: 0.10% to 2.0%, P: 0.10% or less, S: 0.010% or less, Al: 0.010% to 0.100%, Cr: 0.05% to 0.30%, Ti: 0.010% to 0.050%, B: 0.0005% to 0.0030%, Ca: 0.0001% to 0.0050%, and N: 0.0005% to 0.0050%, with a balance consisting of Fe and inevitable impurities; and a ferrite decarburized layer at each of an outer surface and an inner surface, the ferrite decarburized layer having a depth of 20 μm to 50 μm from the surface.

Electric resistance welded steel pipe or tube

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

Disclosed is a high-strength welded steel pipe for airbag inflators that has high toughness and workability. A base material portion of the steel pipe has a composition containing, in mass %, C: 0.02 to 0.08%, Si: 0.001 to 1.0%, Mn: 0.1 to 2.0%, P: 0.1% or less, Al: 0.01 to 0.1%, N: 0.01% or less, Ti: 0.01 to 0.20%, and V: 0.01 to 0.50%, with the balance being Fe and incidental impurities. The base material portion has a structure that includes a ferrite phase having an average grain size of 10 &#x3bc;m or less at an area fraction of 90% or more and a Ti, V-based carbide having an average grain size of 10 nm or less and dispersed in the ferrite phase. The welded steel pipe has a high tensile strength TS of 780 MPa or more and a strength-elongation balance TS&#xd7;El of 15,000 MPa % or more. The difference &#x394;HV in Vickers hardness between the base material portion and the welded portion is 60 points or less. In a softened portion having Vickers hardness different from the Vickers hardness of the base material portion by at least 30 points, a softened width Ws in a circumferential direction is 0.05 mm or less.

Growing community of inventors

Tokyo, Japan

Ryoji Matsui