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川崎製鉄技報
KAWASAKI STEEL GIHO
Vol.19 (1987) No.2
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溶接熱影響部じん性に優れたTMCP製ジャケット用降伏強さ355 MPa級極厚鋼板
The 355 MPa Yield Strength Grade Heavy Section Plate for Jacket Structure with Good Welding Heat Affected Zone Toughness Produced by TMCP

小林 英司(Eiji Kobayashi) 弟子丸 慎一(Shin-ichi Deshimaru) 平井 征夫(Yukio Hirai) 小川 隆生(Takao Ogawa) 天野 虔一(Keniti Amano) 中野 善文(Yoshifumi Nakano)
要旨 :
エネルギー資源開発に必要な巨大構造物に使用されるYS355 MPa級板厚75〜150mm厚鋼板の製造にあたり当社開発のTMCP法であるMACS (Multipurpose accelerated cooling system)を適用した。従来の焼ならし工程では達成が困難であった極厚材の合金量の低減が実現でき,耐溶接割れ性の向上と溶接継手部CTOD値の高位安定化が図れた。さらに圧延仕上り温度と冷却の制御により板厚方向の強度とじん性が均一な板厚150mmまでの製造方法を確立した。−10℃での溶接継手部の要求CTOD値を溶接のままで満足するTMCP製海洋構造物用厚鋼板は,高さ484mの世界最大ジャケット(1986年)に使用された最大板厚100mmを含め,現在までに6万tの実績を得ている。
Synopsis :
MACS (Multipurpose accelerated cooling system) process, controlled rolling and accelerated controlled cooling, were applied to the production of the 355 MPa yield strength grade heavy section steel plates for the huge offshore jacket structure, which has been required for the development of energy resources. By using the MACS process, the decrease in the micro-alloy a-mount of heavy section steel plates was achieved resulting in good welding crack characteristic and good CTOD values at the welding heat affected zone. The heavy section steel plates of up to 150 mm in thickness were thus developed which have homogeneous strength and toughness along the through-thickness direction by controlling the finish rolling temperature and accelerated cooling. Steel plates totaling 60 000 t which were produced by MACS for offshore structures including 100-mm-thick plate and used for huge jackets of 484 m in structural height, have been supplied by Kawasaki steel with satisfying required HAZ CTOD values at minus 10℃ in as-welded condition.
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