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川崎製鉄技報
KAWASAKI STEEL GIHO
Vol.21 (1989) No.1
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溶接構造用非調質HT70およびHT80kgf/mm2 鋼の開発
Development of Controlled-Rolled 70 kgf/mm2 and 80 kgf/mm2 Class High Tensile Strength Steel Plate for Weld Structure

天野 虔一(Keniti Amano) 谷川 治(Osamu Tanigawa) 志賀 千晃(Chiaki Shiga) 奥村 健人(Taketo Okumura)
要旨 :
建設産業機械の軽量化,大型化を図る目的で,溶接性および冷間加工性に優れた厚板圧延ままの非調質HT 70 (25.4mm)およびHT 80 (12.7mm)を開発した。厚板圧延で可能な2相域圧延を最適化すると,TiCの歪誘起析出による析出強化および加工フェライトの回復抑制効果により,靭性劣化の伴わない高強度化が可能となり,低Ceqの標記鋼が製造可能となった。開発鋼の冷間曲げ加工性は従来のHT 80より優れ,また常温での予熱無し溶接施工が可能である。溶接継手部の靭性は建設産業機械用として十分な値を示すとともに,母材疲労特性も従来鋼と同等であった。
Synopsis :
To meet demands for higher strength steel plates for construction machines with excellent cold formability and weldability, as-rolled HT 70 steel plates (TS: 686 MPa) having a maximum thickness of 25.4 mm and as-rolled HT80 (TS: 784 MPa) steel plates of 12.7 mm thickness have successfully been developed by using a plate mill. Both precipitation hardening and inhibition of recovery of deformed ferrite are maximized by optimizing ferrite and austenite dual-phase region rolling. Consequently, strength of the plate has been much increased without deteriorating toughness for lower Ceq. The cold formability of the developed steels is superior to that of conventional as-hot-rolled HT80. Weldability tests have shown that the steels developed have good impact properties at welded HAZ and do not need pre-heating in weld fabrication. The fatigue limit of the steels with mill scale is slightly higher than 50% of its TS, indicating the same behavior as that of the conventional HT 80.
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(c)JFE Steel Corporation, 2003