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■■■■■■■■■■■■■■■■■■■ 川崎製鉄技報 KAWASAKI STEEL GIHO Vol.12 (1980) No.1 ■■■■■■■■■■■■■■■■■■■ |
| 圧力容器用ASME SA387 鋼溶接金属の特性 Properties of ASME SA387 Weld Metals for Pressure Vessels 中野 昭三郎 (Shozaburo Nakano) 安田 功一 (Koichi Yasuda) 西山 昇 (Noboru Nishiyama) 坪井 潤一郎 (Jun-ichiro Tsuboi) 佐藤 功輝 (Koki Sato) 岡田 敏男 (Toshio Okada) 坂本 昇 (Noboru Sakamoto) |
| 要旨 : 圧力容器用SA387鋼のサブマージアーク溶接金属について，SR処理後の常温，高温強度の関係を明らかにし，高温強度の保証をも含めてClass2溶接金属を開発する目的で，その化学成分とSR後の強度，靭性および使用中の脆化特性との関係について検討を行った。溶接金属の強度上昇に対するSiの効果はきわめて顕著であり，MnおよびNb,V等炭化物生成元素の実用範囲での添加では，大きな強度上昇は期待できない。一方，使用中の脆化はSi,Mn,Pの低減によって軽減できるが，極端な低Si化は高温強度を保証できないため適切でない。また溶接金属の強度や靭性を著しく劣化させるフェライトバンドの発生位置，発生条件および発生機構などについても調査・検討を加えた。 |
| Synopsis : Tensile strength of ASME SA387 submerged arc weld metals after stress relief heat treatment (SR) and thermal embrittlement by GE type step cooling are examined to obtain the knowledge on designing the chemical composition of weld metals. Tensile strengths at room temperature and elevated temperatures after SR in various conditions are correlated lineally with tempering parameter. Linear relationships also exist between tensile strength at room temperature and elevated temperatures. Weld metals should be designed on the basis of tensile strength at elevated temperatures. Although the effect of silicon addition on tensile strength is remarkable, thermal embrittlement is aggravated by the additions of silicon, manganese and phosphorus. The optimum contents of each element are determined as follows to satisfy the tensile requirements for Class 2 welds, and to reduce the embrittlement: 0.30-0.35% Si, 0.45-0.65% Mn, and P as low as possible. The formation process of ferrite band is also studied using manual arc welds. Ferrite band is formed during SR within the limited regions of weld metal reheated to the temperature from Ac1 to Ac3 by the succeeding weld passes, and it grows lager as SR temperature becomes higher and/or SR time becomes longer when SR temperature is below Ac1. When SR temperature exceed Ac1, it is not generated at all. The ferrite band results from the growth of ferrite grain caused by abnormal coarsening of carbide. |
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