Key points and classification of TIG welding
TIG welding (abbreviated as tungsten insert gas welding) has been widely used since Hobart and Devers invented the tungsten inert gas welding in 1920s. As the name suggests, TIG welding is a welding method that uses the arc heat generated between the tungsten electrode and the weldment to melt the weldment and filler wire under the protection of inert gas. Its characteristics are as follows:
1. Inert gas has an excellent protective effect. It neither reacts with metals nor dissolves in high-temperature metals, which makes the metallurgical reaction in the weld pool simple and easy to control. It can weld almost all metals and alloys, such as active metals that are easy to oxidize and nitride, ferrous metals with high melting point, etc., especially suitable for welding aluminum, magnesium, titanium, copper and other non-ferrous metals Backing welding of metal, stainless steel, heat-resistant steel, pressure vessel and pipeline.
2. The arc combustion is very stable in argon, and it can still burn stably under the welding current as small as a few amperes. The filler wire is indirectly heated by the arc, and the heat input capacity is adjusted, so it is very suitable for thin plate and all position welding, and it is also a good welding method for single side welding and double side forming.
3. Because the filler wire does not pass through the current, there is no droplet transfer problem, and the arc is very stable in inert gas combustion, there is no spatter in the whole welding process, and the weld shape is fine and beautiful.
4. Inert gas only plays the role of protection and isolation in the welding process, so the surface condition of weldment is required to be high. Before welding, the surface of weldment shall be cleaned, derusted, deoxidized and decontaminated, and the metal luster must be exposed.
5. The current carrying capacity of tungsten electrode is limited, too much current will cause the melting and evaporation of tungsten plate, and the particles falling off may enter the molten pool to form tungsten clip, so the welding current of TIG welding will be limited by tungsten electrode, the welding speed is relatively slow, generally 10-50cm / min; the thickness of welding plate is generally less than 5mm.
6. The inert gas used in TIG welding is generally of high purity, over 99.8%. The welding machine is complex and expensive, and the cost of this welding method is high.
7. The inert gas is greatly affected by the surrounding air flow, and it can't even continue to weld, so it's not suitable to weld in the outdoor and windy places, and measures against wind and wind must be taken to weld. This is the biggest defect of TIG welding!
8. The light intensity produced by TIG welding arc is much higher than that produced by ordinary manual welding, and there is also bromine oxygen produced, which is more harmful to human body. Therefore, protective measures must be taken.
9. The direct current TIG welding also has the theory of positive connection and reverse connection, which is usually positive connection. Only when welding aluminum, magnesium and their alloys, the reverse connection method is used, but the allowable carrying current is very limited. In actual production, the alternating current TIG welding is generally used.
10. Although inert gas is used for TIG welding, some non inert gases, such as hydrogen, nitrogen, oxygen and carbon dioxide, are also used in actual production operation.
TIG welding classification:
11. Classification by current waveform: ① DC TIG welding; ② AC sine wave TIG welding; ③ AC square wave TIG welding; ④ low frequency pulse TIG welding; ⑤ intermediate frequency pulse TIG welding; ⑥ high frequency pulse TIG welding.
12. Classification by Mechanization: ① manual TIG welding; ② automatic TIG welding.
13. Classification according to whether the welding wire is preheated: ① cold wire TIG welding; ② hot wire TIG welding.
14. Classification according to the number of filler wires: ① single wire TIG welding; ② double wire TIG welding.
15. Classification by shielding gas: ① argon arc TIG welding; ② helium arc TIG welding; ③ mixed gas TIG welding.
16. TIG welding type selection: ① DC TIG welding is suitable for stainless steel, heat-resistant steel, copper (nickel, titanium) and its alloy, etc. ② AC TIG welding is suitable for aluminum (magnesium) and its alloy, aluminum bronze, etc. ③ Pulse TIG welding is suitable for thin plate, all position pipe welding, high speed welding, materials with strong thermal sensitivity, etc. ④ TIG welding with hot wire and double wire is of high efficiency.
