R＆D Of New Type Marine Agglomerated Flux For SAW With Large Heat Input

In order to improve the welding productive and short the period efficiency of ship-building, the high efficient welding technique has been used in many domestic shipyards. FCB is short for the high efficient technique of flux and copper backing with one-side welding both-side forming. At present, the welding material as such as flux involving in this technique mainly depend on importation. For this reason, the spread use of high efficient welding technique of FCB was greatly restricted in domestic shipyard. Therefore, the development of new welding material which is adapted to our country's material resources has been a critical subject for instant development of shipbuilding industry.In allusion to the characteristic agglomerated flux using in the FCB, a new agglomerated flux with slag system of MgO-CaO-Al₂O₃-SiO₂ has been successfully developed. Under the condition of 116J/cm heat input, excellent welding technology property obtained by using submerged arc welding with three electrode. The mechanical property of weld joint can satisfy the 3Y requirement of classification society of china, as well as the shipyards.HG·FCB-1 combined separately with weld wire H10Mn2 and H08A has been used for automatic submerged-arc welding. The result indicated that the welding arc was stable, and there was basically no splash with the molten slag. The appearance of the surface weld was beautiful with finely waviness, while the backing weld with homogeneous width and height was in good fusion to the base metal.While the HG·FCB-1 was applied to automatic submerged-arc welding combined with H10Mn2 for the first electrode , H08A for the other two, and heat input is 116kJ/cm, the impact ductility value at -20℃of welding joint all were bigger than 34J, which meet the using requirements of shipyard absolutely.By adding alloy such as Mn, Si and Ti into the agglomerated flux, the capability of resisting gas cavity was greatly improved in weld metal. At the meantime, this alloy method can effectively reduce the content of proeutectoid ferrite in weld metal, and promoting the forming of the acicular ferrite, with great impact ductility of weld joint. The microscopic structure of the weld mainly consisted of proeutectoid ferrite, acicular ferrite and pearlite.