The big problem with titanium melting welding in the air is oxidation and compounds and intermetallic compounds caused by various pollutions. The so-called pollutants refer to oxygen, nitrogen and a variety of other oils, dust, etc. , which will reduce the quality of titanium welding. Contaminants include not only oxygen and nitrogen, but also organics, inorganics, and metals other than titanium. Such as mechanical oil stains, lubricants and nearby workshop iron powder, paint powder, surrounding moisture, moisture, sand, dust and so on. There is also tungsten mixed from the electrodes. The harm of oxygen, nitrogen and water in the air is greater. Therefore, the welding must be protected by inert gas. Usually the surface of titanium has a 40um thick oxide film, after cutting a few seconds can restore 80% of the thickness, after a few minutes can be restored to the original thickness. It is because of this layer of oxide film, titanium has such good corrosion resistance. The oxygen content in this range is not a pollutant. However, when titanium meets high temperatures in the atmosphere, it reacts with large amounts of oxygen and nitrogen. This produces contaminants. At an atmospheric temperature of 427 degrees C, the thickness of the oxide film on the titanium surface is 2 to 3 times that of normal temperature. The oxide film increases above 650 degrees C. In the molten state, oxygen, nitrogen, etc. will enter the welding pool, and then spread from the welding metal to the master material. In order to prevent the mixing of oxygen, nitrogen and other debris in the air, it is necessary to protect the welding surface and the inside through inert gas during welding. TIG welding of other metals generally does not require gas protection, and most of the inside does not require gas protection. In addition, to prevent the production of grease debris, titanium and operating table surface can not be wiped with oil. Most of the technical problems in titanium melting welding are how to avoid the above-mentioned pollutants. Countermeasures to prevent and control pollutants are cumbersome and costly. However, the success of titanium welding lies in the prevention of pollutants.
