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1. (WO2018066249) ELECTRIC RESISTANCE-WELDED STEEL PIPE FOR TORSION BEAM

Pub. No.:    WO/2018/066249    International Application No.:    PCT/JP2017/030205
Publication Date: Fri Apr 13 01:59:59 CEST 2018 International Filing Date: Thu Aug 24 01:59:59 CEST 2017
IPC: C22C 38/00
C22C 38/58
C21D 9/46
Applicants: NIPPON STEEL & SUMITOMO METAL CORPORATION
新日鐵住金株式会社
Inventors: FUKUSHI, Takaaki
福士 孝聡
SHINOHARA, Yasuhiro
篠原 康浩
HAMATANI, Hideki
濱谷 秀樹
Title: ELECTRIC RESISTANCE-WELDED STEEL PIPE FOR TORSION BEAM
Abstract:
An electric resistance welded steel pipe for a torsion beam, wherein: a base metal section comprises, in mass%, C: 0.04–0.12%, Si: 0.03–1.20%, Mn: 0.30–2.50%, Ti: 0.08–0.24%, Al: 0.005–0.500%, Nb: 0.01–0.06%, and N: 0.0005–0.0100% and the balance comprises Fe and impurities; Vc90 defined by equation (i) and equation (ii) is at least 200; the content mass ratio of Ti to C is 0.85–5.00; and in the center of the wall thickness of an L cross-section of the base metal section, the ferrite area ratio is at least 80%, the average crystal grain size of the ferrite crystal grains is 10 µm or less, and the average aspect ratio of the ferrite crystal grains is 2.0 or less. Equation (i): log V c90=2.94−0.75(βa−1) Equation (ii): βa=2.7C+0.4Si+Mn+0.45Ni+0.8Cr+Mo