Skip to main content

GAS TUNGSTEN - ARC WELDING (TIG) , ITS PROCESS AND ADVANTAGES

This process, often called TIG (Tungsten inert gas) welding, is similar to MIG in that it uses the gases for shielding. This arc-welding process uses the intense heat of an electric arc between a non consumable tungsten electrode and the material to be wielded.

The shielding is obtained form an inert gas such as helium or argon or a mixture of the two. Argon is more widely used than helium because it is a heavier gas, producing better shielding at lower flow rate. the shielding gas displaces the air surrounding the arc and weld pool. This prevents the contamination of the weld by the oxygen and nitrogen in the air.

Filler metal may or may not be used. However, it is usually employed, except the material. When a filler metal rod is used, it is usually employed, except thin material. When a filler metal rod is used, it is usually fed manually into the weld pool. Automatic feeding of the filler wire into the TIG arc to speed up the process has now been developing.

Electrodes used in this process are made of tungsten and tungsten alloys. The tungsten electrode is used only to generate an arc. The arc does not melt the tungsten, which has a melting point of over 3300*C. The end of the welding gun where the arc is created either is made of  high-impact ceramic or is water-cooled.

The TIG process lends itself ably to the fusion welding of  aluminum and its alloys, stainless steel, magnesium alloy, nickel-base alloys, copper-base alloys, carbon steel and low alloy steel. TIG welding can also be used for the combining of dissimilar metals, hard facing and the surfacing of metals. But this process is not used as often on plate over 64 mm thick, but it is easier than MIG welding for thin plates and small parts.

The torch used in this welding method holds the electrode and directs shielding gas and welding power to the arc. Arc spot welds can also be made with a TIG torch fitted with special adapters. In this case a 3 mm electrode is often used for a total cycle time of 1/2 to 3 s depending on the alloy and its thickness.

In general, an arc power source is best for TIG welding non ferrous alloys except deoxidized copper. For ferrous alloys the dc power source with straight polarities (electrode negative) is better for gas tungsten-arc welding because it greatly reduces the volumetric loss from the tungsten electrode. For example, a TIG torch which has a rating of 250A when used with straight polarity (dcsp) must be derated to 15 to 25A when used with reversed polarity ( dcrp - electrode positive) . As little as 3 A may be used for work on very thin metals and intricate parts.


Gas Tungsten - Arc Welding (TIG)


Advantages of  TIG Welding :

1.) It produces high- quality welds in non-ferrous metals, 

2.) Practically no weld cleaning is necessary 

3.) The arc and the weld pool are clearly visible to the welder. 



Labels:

Comments

Post a Comment

Popular posts from this blog

ELECTRICAL COMPARATORS AND ITS WORKING

Electrical Comparators are used as a means of  detecting and amplifying small movements of a work contacting elements. An electrical comparator consists essentially of  a pick-up head or transducer for converting a displacement into a corresponding change in current and a meter or recorder connected in the circuit to indicate the electrical change, calibrated to show in terms of displacement. Generally, an amplifier is needed to provide the requisite sensitivity and to match the characteristics of different parts of  the circuit. Electrical comparators can be classified according to the electrical principle used in the pick-up head. Most of the comparators use either a differential transformer, an inductance bridge, a strain gauge or a capacitor as a means of detecting movement of the gauging element. There are different types of  electrical comparators. One kind called an electrolimit gauge is used to check or measure the outside diameter of a  roll. The objec...
1 comment
Read more

TOP POLLUTION RECORDED IN WORLD

CHERNOBYL NUCLEAR DISASTER (NUCLEAR POLLUTION) :  In April 26,1986, the melt down of the Chernobyl nuclear reactor , in Russia, has leaked out the radioactive rays and radioactive materials.   Effects : 1. In this Pollution nearly 2000 persons have been killed by the accident. 2. People suffered due to the illness such as, degeneration of the cells, severe bleeding, anemia, skin cancer. 3. Animals, Plants are also affected by nuclear radiation.  MINAMATA EPIDEMIC (1953) : MARINE POLLUTION ( CASE STUDY ) Minamata is a small coastal village in Japan. The Chisso Chemical Company , which produces vinyl polymer plastics used organomercurial compound. The industry released its effluent into Minamata sea. The effluent containing mercury ions is converted into methyl mercury, which is highly toxic.  The marine organisms like phytoplankton and zoo-planktons easily absorb the toxic methyl mercury compound. These organisms are consumed by small fishes and these are in ...
Post a Comment
Read more

MELTING FURNACES FOR FERROUS METALS : CUPOLA AND ITS WORKING

Various types of melting furnaces are used in different foundry shops, depending upon the quantity of metal to be melted at a time, and the nature of work that is carried out in the shop.  The primary objective in cupola is to produce iron of desired composition, temperature and properties at the required rate in the most economical manner. Besides, this furnace has many distinct advantages over the other types, e.g., simplicity of operation, continuity of production, and increased output coupled with a high degree of efficiency.  Description Of a Cupola : The Cupola Furnace consists of a vertical, cylindrical steel sheet, 6 to 12 mm thick, and lined inside with acid refractory bricks or acid tamping clay. The refractory bricks or the tamping clay used consist of  silicon oxide acid (SiO2) and alumina (Al2O3). The lining is generally thicker in the lower where the temperatures encountered are higher than in the upper region. The shell is mounted either on a brick work fo...
Post a Comment
Read more