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■■■■■■■■■■■■■■■■■■■ 川崎製鉄技報 KAWASAKI STEEL GIHO Vol.14 (1982) No.1 ■■■■■■■■■■■■■■■■■■■ |
| 狭開先サブマージアーク溶接法―NSA法― Narrow Gap Submerged Arc Welding (NSA) Process 平井 征夫(Yukio Hirai) 徳久 正昭(Masaaki Tokuhisa) 山下 至(Itaru Yamashita) 西尾 要(Kaname Nishio) 赤秀 公造(Kozo Akahide) 浮辺 輝男(Teruo Ukebe) |
| 要旨 : 極厚鋼材の狭開先サブマージアーク溶接におけるスラグはくり性の改善，溶接欠陥の防止に重点をおいて検討した結果，高塩基性焼成型フラックスKB120を用いるNSA法を開発いた。スラグの熱収縮挙動がはくり性を支配する最重要要因子であり，溶接冷却過程における700℃付近での変態膨張を抑制することによって最大のスラグ収縮量が得られた。MgO-BaO-SiO2系の高塩基性フラックスKB120は溶接金属の水素量，酸素量をも低減できる特長を有している。本法の高信頼性および高能率性は種々の現場適用によって確認された。板厚200mmまでは１層１パス法で積層でき，開先面積は従来法の1/2以下に低減できる。 |
| Synopsis : With main emphasis on improving slag detachability and preventing weld defects, study was made on heavy steel plate welding in the narrow gap submerged arc welding, leading to the development of the NSA process that uses an MgO-BaO-SiO2 type high-basicity agglomerated flux, KB-120. With thermal contraction behavior of slag found to be the most important factor that determines slag detachability, the maximum contraction was obtained by suppressing transformation expansion occurring around 700℃ during cooling. It was found that KB-120 can also produce weld metal of low level hydrogen and oxygen. High reliability and productivity of this process has been confirmed by its wide application to the fabrication of pressure vessels, offshore structures and machinery. Since the "one layer-one pass" welding method is used to build up for steel plates up to 200mm in thickness, the crosssectional area of the groove and arc time are reduced to 1/2 to 1/3 of those in the conventional process. The use of very low hydrogen flux provides additional advantages such as elimination of intermediate postweld heat treatment and lowering of preheating temperature. |
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