| ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ KAWASAKI STEEL TECHNICAL REPORT No.20 ( June 1989 ) Information Systems ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ |
| Development of Controlled-Rolled 70kgf/mm2 and 80kgf/mm2 Class High Tensile Strength Steel Plates for Welded Structures Keniti Amano, Osamu Tanigawa, Chiaki Shiga, Taketo Okumura |
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Synopsis : To meet demands for higher strength steel plates for construction machines with excellent cold formability and weldability, as-rolled HT70 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 HT80. |
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