Factors need to be considered in choosing tungsten electrode
1. Requirement of tungsten electrode without melting for TIG: the electron emission ability, arc characteristics(striking arc and stable arc) of all kinds of tungsten electrode, current carrying capacity, the material quality and welding thickness of metal to be welded must withstand high temperatures and be not easy to melt loss.
2. The maximum allowable current is related to the chemical composition, diameter, and type of current and current polarity of tungsten electrode, the extending length from current contact nozzle of tungsten electrode.
Loss of tungsten electrode:
(1) Normal loss: in the normal welding process, the loss of tungsten electrode caused by heat evaporation and slow oxidation. Normal loss is related to chemical constituents of tungsten electrode, the types of power supply and polarity.
(2) Abnormal loss: it mainly occurs in multiple short circuit arcs, or caused by the contact between tungsten electrode and welding wire and molten pool.
(3)The capability of stable arc and striking arc: it is mainly determined by the size of work function of tungsten electrode. If the work function is low, the electron emission ability is strong, the stable arc and striking arc performance will be good. Otherwise, it will be bad.
(4)In addition, the source of electrode, the service life and price etc. should be considered. Generally, the thick plate welding requires it can be obtained the increasing penetration; therefore, the welding should adopt the DCSP and large current, and should use the thorium tungsten with strong current carrying ability or zirconium tungsten electrode.
The penetration requirements of thin sheet metal welding is shallower, so the welding current should be small, it should adopt the method of reverse DC, but this is easy to make the electrode to produce heat. Therefore, the electrode should choose thoriated tungsten or cerium tungsten electrode which has easy starting arc and good stability. The welding of aluminum and magnesium and its alloys requires using AC. In this case, the burning loss degree of electrode will be smaller than DCRP, so we can choose a relatively cheap pure tungsten electrode.
2. The maximum allowable current is related to the chemical composition, diameter, and type of current and current polarity of tungsten electrode, the extending length from current contact nozzle of tungsten electrode.
Loss of tungsten electrode:
(1) Normal loss: in the normal welding process, the loss of tungsten electrode caused by heat evaporation and slow oxidation. Normal loss is related to chemical constituents of tungsten electrode, the types of power supply and polarity.
(2) Abnormal loss: it mainly occurs in multiple short circuit arcs, or caused by the contact between tungsten electrode and welding wire and molten pool.
(3)The capability of stable arc and striking arc: it is mainly determined by the size of work function of tungsten electrode. If the work function is low, the electron emission ability is strong, the stable arc and striking arc performance will be good. Otherwise, it will be bad.
(4)In addition, the source of electrode, the service life and price etc. should be considered. Generally, the thick plate welding requires it can be obtained the increasing penetration; therefore, the welding should adopt the DCSP and large current, and should use the thorium tungsten with strong current carrying ability or zirconium tungsten electrode.
The penetration requirements of thin sheet metal welding is shallower, so the welding current should be small, it should adopt the method of reverse DC, but this is easy to make the electrode to produce heat. Therefore, the electrode should choose thoriated tungsten or cerium tungsten electrode which has easy starting arc and good stability. The welding of aluminum and magnesium and its alloys requires using AC. In this case, the burning loss degree of electrode will be smaller than DCRP, so we can choose a relatively cheap pure tungsten electrode.
