摘要
钛合金具有比强度大、比重量轻、耐高温、加工成型以及焊接性良好等优点,一直被广泛的应用于航天、航空、化工等领域。材料的发展及被广泛应用,离不开良好的焊接方法的支撑,因此,探索出高效的焊接方法能够促进钛合金的发展。同时,钛合金实际焊接生产中焊缝经常出现气孔、夹杂等缺陷,在服役过程中结构件易于磨损,为了延长结构件的使用寿命和降低成本,补焊不失为一种良好的解决问题的方法。
本课题以此为出发点,针对国内牌号TA15钛合金板材,探索出适合TA15钛合金的高效焊接方法,其中包括激光-TIG复合热源焊接方法和活性化TIG焊接方法。同时对钛合金焊接试件进行补焊,并对补焊焊缝进行了系统的分析。
研究结果表明,采用激光-TIG复合热源焊接工艺可以实现钛合金的高速焊接,其焊接速度可达普通TIG的3～4倍。通过接头微观组织和力学性能分析,发现激光-TIG复合焊接接头成型良好,焊缝区由上部的柱状晶和下部的等轴晶构成,断口为韧性断裂,焊缝抗拉强度可以达到母材的98%以上。
采用活性化焊接,在单一活性剂堆焊的基础上,综合考虑熔深及力学性能等方面因素,选取4种活性剂分别进行两组3水平3因素的正交试验,试验结果显示,选用理想配比的混合活性剂,在相同参数条件下,熔深可提高到普通TIG焊接熔深的3.46倍。
对TA15钛合金焊接接头进行多次补焊,发现随着补焊次数的增加,补焊焊缝组织长大,合金元素在母材中与在焊缝中含量不均衡程度加大,接头疲劳循环次数降低,其中初始焊接接头、一次、二次和三次补焊接头变化较小,而三次补焊接头与四次补焊接头的差别则尤为明显。采用涂活性剂补焊,可以在焊缝缺陷处直接进行填丝补焊,并且补焊焊缝熔合良好,补焊焊缝组织不发生长大现象。
Titanium alloys are widely used in the fields of aviation, spaceflight and chemical industry due to their excellent properties such as excellent specific strength, low specific gravity, strong resistance to elevated temperatures, good design ability and good weldability. The developments and applications of materials can not go along without good welding means. Thus it will accelerate the developments of titanium alloys to explore the high efficient welding methods. However, the defects such as porosity, impurity, faulty fusion are always found in the titanium alloy welding joints, additionally the welding joints are liable to be worn out when in using, thus it make the service life of structures reduce. It will be large economic losses that exchange the structures. Thus, repaired welding is a good method to prolong the service life of the structures.For the plate of TA15 titanium alloy, the high efficient welding methods have been explored concluding laser-TIG hybrid welding method and active TIG method. Meanwhile the weldment has been repaired welded and the repaired welding joints have been analyzed sysmeticly.The results show that by laser-TIG hybrid welding it can actualize welding titanium plate method in high speed which is 300-400% of TIG method. Through the analyzing the microstructures and properties of the joint, it can be found that welded seam of titanium alloys, forming well and regularly is made up of columnar crystals above and equiaxed crystals below. The tensile strength achieves 98% of base metal and the fracture of samples proves to be gliding fracture.TA15 titanium alloy is bead welded by active TIG with single flux firstly. Based on penetrations and properties, 4 species of fluxes are selected and the orthogonal test with 3 factors and 3 indexes are carried out. The result show that in the same parameters, weld penetration can be 3.46 times deep of TIG with ideal match mixed fluxes.TA15 titanium alloy weld joints are repaired welded with multiple times. It found that with the repaired welding times increase, the microstructures of the repaired weld seams grow up. Alloy elements between the base metal and the weld bead distribute more unevenly. Fatigue circles reduce and the amplitude of reduction augments especially from 3rd time repaired weld joint to 4th time repaired weld joint. When the weld joints are repaired welded with flux, it can be repaired at the defect place straightly without drilling out the defects. Further, the repaired weld seam forms well and the structures do not grow up.
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