Tig welding is a semi-automatic or automatic high-frequency process that melts the filler metal into the base material by using electricity from a separate power source to establish an arc between the tip of the torch, where contact is first made with metals, and the workpiece/electrode.
Every day, welders are called on to repair things like broken pipes, torn metal parts and equipment that has been damaged by fire. Welding can also be used to create new things out of new materials. Welding is the process of joining two surfaces with intermittent or permanent layers of molten metals.
Two types of welding exist:
- Gas Tungsten Arc Welding (GTAW)
- Gas Metal Arc Welding (GMAW)
How Does Metal Melt Using Tig Welder?
Initially, AC current is used to heat electrodes up to 2400 degrees Celsius and force them into contact with each other (the resulting friction causes sufficient heat for fusion), then a DC current is applied after which forced alternating current forms an electric arc between the electrode tip and workpiece (that has been preheated) which in turn causes the metal to melt.
Factors That Effects Tig Welding
This is a simplified explanation of how tig welding works, as there are many different factors that come into play. The actual configuration and design of equipment used in TIG welding vary widely depending on the intended application. For example, materials may require higher or lower operating voltages, gas flow rates, types of filler rods, and more. Arcing (contact between electrode and workpiece) must be carefully controlled for reasons discussed below.
Welding machines typically include an AC/DC power source with electronic controls capable of adjusting current and voltage to account for changing current demand during a weld. Unlike other arc welding methods such as shielded metal arc welding (SMAW), which uses open-circuit electrodes that create a pool of molten metal on the workpiece, TIG welding uses an electrically isolated electrode to start a small electric arc between the electrode and the workpiece. This arc is well below the melting point of either electrode or of the workpiece, allowing an external filler rod to be added to form the desired weld.
This makes possible highly specialized TIG processes for applications such as difficult metals like titanium or magnesium alloys that are heated only by this focused heat source. Filler materials may be added manually (via welding torch) as semi-molten beads, but in contemporary industrial use, it is more common for current to be supplied through a “stinger” tube with multiple gas nozzles designed for specific filler types. In “air-cooled” TIG, the only heat source is an electrical arc between the workpiece and one electrode. The other electrode or ground shield simply serves as a convenient current return path for the welding circuit.
The air gap in this application allows the use of lighter (higher frequency) power supplies that will not pass excessive currents through the relatively high impedance gas plasma. In fact, although important in MIG welding, gas flow is usually unnecessary for TIG except to help cool filler metal deposited by spray transfer.
Gas Tungsten Arc Welding (GTAW):
Tungsten inert gas (TIG) welding is also known as tungsten inert gas shielded metal arc welding (GTAW), informally known as “tig”, and often with interpunctuation as tig welding.
A Tig Welder Using Gas Tungsten Arc Welding works just like other types of welding except that it uses a nonconsumable tungsten electrode(tungsten electrode does not melt during welding) instead of bare electrodes or rods made out of metal alloy. When voltage is supplied to this non-consumable electrode it heats up to extremely high temperatures and emits electricity that is transferred to the work piece. The electric arc forms between this electrode and the work piece, creating fusion and thus welding takes place.
In a clean, modern TIG welder with a ball-drain type electrode holder, the arc is easily started by touching the tungsten to the work and then creating a small negative voltage between the workpiece and machine. If you hear a loud crackling noise or see smoke coming from the work before you start welding, your connections are probably wet or dirty. A slight positive voltage applied between the tungsten and work will propel molten metal from the end of the rod into contact with base metal for fusion.
This is called ‘spray transfer’. (In an older welder with electrodes threaded through a rubber sleeve surrounding its cable, it is easy to touch both electrodes and work simultaneously.) When you see metal transfer taking place, it is too late to make any changes in current.
With the voltage increasing, stop adding a filler rod and let the tungsten do all the work. The metal transfer will end when either (1) the weld is complete or (2) too much heat enters the weld pool and oxidizes its surface or (3) both – I’m not sure how this works.
When welding aluminum with a 10% silicon alloy wire, there’s a momentary delay between when you first see metal transfer and when it actually begins. You may have to experimentation with different processes to determine where “metal transfer” occurs for your equipment.