Common Joint Designs of gas tungsten ARC welding
Gas Tungsten Arc Welding (GTAW) is referred to in professional circles as Tungsten Inert Gas (TIG) welding. This is an arc welding process that uses a tungsten electrode to create the weld.
Learning the fundamentals of GTAW will certainly enlarge the welder's work skills. Gas tungsten arc welding (GTAW) is an electric arc welding process that produces an arc between a non-consumable electrode and the work to be welded. To qualify as a GTAW welder, you need to learn and gain proficiency in welding joints, corners, and T (fillet). Each of these types call for different considerations of GTAW and the welder must understand the varying methods.
It is possible to configure all three joint types with mild steel, stainless steel, and aluminum - provided the special precautions for each type of metal is followed.
As a common rule, before commencing welding on any joint of any material,clean the material properly and position the GTAW torch at a 70-degree angle to the seam of the joint, with the filler metal at a 20-degree angle to the joint. Make it a point to use a high-frequency start for DC work on mild steel and stainless steel, and use continuous high frequency for AC aluminum applications.
GTAW is capable of being used on both ferrous and nonferrous metals and depending on the base metal, in all welding positions. When welding thinner materials, edge joints, and flange, filler metals are not needed. For thicker materials, however, an externally fed filler wire is generally used. The type of filler metal wire to be used is based on the chemical analysis of the base metal. The size of the filler metal wire varies depending on the thickness of the base metal.
The procedure for welding butt joints of carbon and stainless steel is they should be tack welded or skip welded - weld an inch, move down several inches and weld another inch, until you reach the end of the joint. Thereafter do the welding between the existing welds. As aluminum does not distort as much as stainless steel, the tacks can be placed farther apart maybe at three inches.
T joints, as we know, consist of two pieces of material connecting each other at right angle. They need a fillet weld and are widely seen in many fabrication of building industry. T Joint in a tube requires a curved fillet weld as the connecting tube contours to the curve of the cross-member of the T. For T joints, you must place the weld on the same side of the joint where force against the weld will be applied.
A corner joint consists of two pieces of material joined to form an L shape. These are of two types. When the edge of one piece lies flush against the edge of the other piece, it is a closed corner joint. When two edges meet at their corners and there is an opening then it is an open corner joint. You usually can fusion weld a closed corner joint without adding filler metal. Open corner welds however, needs filler metal.
It may be stated that there are many things in common with regard to Corner, butt, and T Joints. But there also many differences amongst them. There are five basic types of joints and they are the butt joint, the corner joint, the edge joint, the lap joint, and the tee joint. Of the five types of joint designs, the butt and the tee joint are the most common.
Selecting welding variables depend on the base metal, filler metal and joint configuration. The fixed welding variables include filler metal, electrode type and size, the type of current, and the type of shielding gas. Secondary variables include work and travel angle and the distance the electrode extends beyond the end of the cup.
Gaining competence in the fundamentals of the GTAW will qualify the welder to produce quality welds. Having a good understanding of the GTAW process will help the welder make wiser choices of filler metals, welding equipment, tungsten electrodes, and shielding gases.