氟化物ATIG焊接Ti6Al4V的焊缝成形和组织

试验选用MF型氟盐(LiF,NaF,KF)、MF2型氟盐(MgF2,CaF2,BaF2)和KN型钾盐(KF,KCl,KBr)对Ti6Al4V进行ATIG焊接,焊后研究了焊缝的成形、熔深和组织.结果表明,除MgF2焊道成形稍有曲折外,其它活性剂ATIG焊接接头均成形良好、无缺陷;氟化物能起到阻止熔池金属氧化的作用;KF和MF2型氟盐可显著减小焊缝熔宽;同阳离子的氟化物相比其氯化物和溴化物可显著增加Ti6Al4V焊缝熔深;MF型氟盐中KF活性剂获得的焊缝熔深最大,MF2型氟盐中MgF2活性剂获得的焊缝熔深最大,且熔深MgF2>KF;TIG和ATIG的焊缝组织均为粗大的柱状晶,活性剂ATIG焊可细化焊缝晶粒尺寸,但不会对焊缝的相结构组成造成影响.

Weld shape and microstructure of Ti6Al4V alloy fluoride A-TIG weld

Three types of compounds, i.e. MF type fluorides (including LiF, NaF, KF), MF2 type fluorides (including MgF2, CaF2, BaF2) and KN type potassium (including KF, KCl, KBr), were chosen as activated fluxes to evaluate the effect of weld shape, penetration and microstructure on the A-TIG Ti6Al4V alloy weld. The results show that good appearance and defect-free welded joints could be obtained with fluoride fluxes, except MgF2. Fluorides might act as antioxidants, which could keep weld bead from oxidation. In addition, bead width was significantly decreased in A-TIG with KF flux and MF2 type fluxes. Fluoride could effectively increase weld penetration than other halides (chloride and bromide) under the condition of same cationic. The KF fluoride in MF type had the greatest impact in increasing penetration, while MgF2 fluoride in MF2 type had the highest impact with larger penetration than that with KF fluoride. Furthermore, the solidification microstructure consisted of coarse and columnar grains throughout the complete fusion zone in both TIG and A-TIG welds. And the grains exhibited obvious refining effect in A-TIG weld, but it did not change the phase structure of weld bead.