钛及钛合金的焊接是比较困难的,这是由钛及钛合金的物理化学性能所引起的,主要表现在冶金焊接性和热焊接性两个方面。首先,在高温下,特别是在熔融状态下,钛及钛合金具有很高的化学活性,极易为氮、氢、氧等杂质所污染,致使金属脆化,并使焊接后易出现气孔、裂缝等缺陷。其次,在加热过程中,钛及钛合金晶粒容易长大,在冷却过程中又会发生复杂的相转变,易形成脆性相,同时导热系数低,热容量小,线膨胀系数大。因此,对焊接工艺要求特别严 Titanium and titanium alloy welding is more difficult, which is caused by the physical and chemical properties of titanium and titanium alloys, mainly in the metallurgical and thermal weldability of two aspects. First of all, at high temperature, especially in the molten state, titanium and titanium alloys have very high chemical activity and can easily be contaminated with impurities such as nitrogen, hydrogen and oxygen, resulting in embrittlement of metal and easy occurrence of pores after welding. Cracks and other defects. Secondly, during the heating process, the titanium and titanium alloy grains grow easily. During the cooling process, complicated phase transformation occurs, forming brittle phase with low thermal conductivity, small heat capacity and large linear expansion coefficient. Therefore, the welding process is particularly demanding