SiO_2增加铝合金交流A-TIG焊熔深的机理

Mechanism of weld penetration increased by SiO_2 in AC A-TIG welding for aluminum alloy

采用单组元活性剂进行铝合金交流A-TIG(Activating flux TIG)焊时,SiO2增加熔深最明显,对其增加熔深的机理进行了研究。进行正散焦真空电子束焊试验,SiO2对焊缝成形几乎没有影响;进行系列直流正接A-TIG焊试验,研究了活性剂对电弧的影响,发现SiO2使得氧化膜厚度增加,电弧极性区收缩,弧柱区扩展,电弧电压升高;进行氦气保护交流A-TIG焊试验,发现SiO2使活性剂或金属蒸发的区域变窄且蒸发量变小,熔池表面凹陷,并且在焊接过程中SiO2涂层始终存在于熔池表面,只在熔池凹陷中央区域出现很窄的裂缝,蒸气主要集中在电弧中下部。认为电弧极性区收缩和热输入增加是SiO2增加铝合金交流A-TIG焊熔深的主要机理。

The weld penetration increased by SiO2 is the most obviously when some single-component fluxes are used as surface activating flux in AC A-TIG(alternating current activating-tungsten inert-gas) welding of aluminum alloy.The mechanism of SiO2 increasing weld penetration of AC A-TIG welding was studied.SiO2 has little effect on weld appearance of electron beam welding with positive defocus.A series of DCSP A-TIG welding experiments were carried out to investigate the effects of SiO2 on welding arc.It is found that SiO2 can constrict arc polarity area,broaden arc column and improve arc voltage.AC ATIG welding with helium shielding gas was carried out.It is found that SiO2 constricts evaporation area,weakens evaporation of activating flux or base metal,and depresses weld pool surface.During the welding process,SiO2 coating is always on the weld pool surface.Only there is very narrow gap on the central region of depressed weld pool.Vapor concentrates in the lower middle part of arc.The results indicate that arc polarity area constriction and input heat increase are the main mechanism to increase weld penetration by SiO2 in AC A-TIG welding for aluminum alloy.