TIG Welding FAQ

From Welding Wiki
Jump to: navigation, search

Here we will try to answer some of the questions that are often asked by newcomers to TIG (Tungsten Inert Gas) welding, the TIG process is also known as GTAW (Gas tungsten arc welding), and TAGS (Tungsten arc gas shielded).

Setting up the welder

Connecting the welding leads

The torch lead is normally connected to the Negative (-) connector of the welding set. That's DCEN (DC current electrode negative).

Selecting the correct tungsten size and current

Tungsten size is determined by the thickness of the metal to be welded and the welding current used, a rough rule of thumb is 30 to 40 amps per millimetre of metal thickness, Typical current ranges are: 1.6mm, 30 to 120 amps, 2.4mm, 80 to 240 amps, 3.2mm, 200 to 380 amps. For more information see Tungsten sizes

The welding torch

TIG torches are fairly simple items, but knowing what the individual components are called can save time when buying spares, and correct assembly can prevent simple operating problems, See The Basic TIG Torch

Gas flow

Gas flow is set by adjusting the cylinder regulator, flow rates will vary slightly depending on working conditions, joint type and ceramic cup size, but would not be expected to be less than 4 litres per minute, and may rise to as much as 12 litres per minute, See Setting up the gas

Shielding Gases

Gas Choice

Pure Argon is the most common shielding gas for Tig welding, it will cope with all common materials, for some specialised and automated processes Helium and Argon Helium mixes are sometimes used. Argon mix gases and CO2 as used in Mig welding cannot be used with TIG, the CO2 in the mix is an active gas and will destroy the tungsten electrode as soon as an arc is struck. For information on independent gas suppliers see the list on the Gas Suppliers page.

TIG Welding Steel and Stainless Steel

Welding Machines

A TIG welder with an DC output is required to weld Stainless and mild steels, these may be transformer based, or Inverter based, most modern DC inverter Arc welding sets can be used as a basic TIG welder

Electrodes For DC

Thoriated electrodes are the traditional choice for welding mild and stainless steel, because of a slight radiation risk from the dust produced by grinding they are increasingly being replaced by Ceriated or Lanthanated tungstens,

Preparing the tungsten

Tungsten electrodes used on DC need to be ground to a point, the length of the taper is usually about 2 to 3 times the diameter of the electrode, grinding should be carried out so that grinding marks are length-ways, and not radial. See DC Electrode Preparation

TIG Welding Aluminium

TIG Welders

A TIG welder with an AC output is required to weld aluminium and its alloys, AC TIG welders have either a high frequency generator on board or clever electronics to initiate and maintain the arc, cheap AC buzzbox welders are not suitable.

Electrodes for Aluminium

Traditionally, Zirconiated electrodes are used for Aluminium, there are also all purpose electrodes, such as Ceriated, and lanthanated, which can be used both with Aluminium, and mild and stainless steels. In AC welding the tip of the electrode will form a ball, up to and including 1.6mm will need no preparation, with electrodes of 2.4mm and above a very shallow point may be ground to assist with the formation of the ball, the length of the taper being about one third of the electrode diameter. See AC Electrode preparation