Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is a highly precise and versatile welding process that operates at temperatures over 6,000 degrees Fahrenheit (3,410 degrees Celsius). This process uses an electric arc between a nonconsumable tungsten electrode and the workpiece to produce a weld, with the weld area shielded from the atmosphere by a shielding gas.
Preparing the Weld Joint and Cleaning the Material
To ensure a successful GTAW weld, it is crucial to properly prepare the weld joint and thoroughly clean the material to be welded. This includes removing any oil, grease, paint, dirt, oxides, or other foreign material from the surface. For aluminum, it is essential to remove the oxide coating to prevent contamination of the weld area.
Cleaning Methods
- Cleaning solutions: Degreasing agents, solvents, and other chemical cleaners can be used to remove contaminants.
- Wire brushes: Stainless steel wire brushes can be used to mechanically remove surface impurities.
- Grinders: Angle grinders with abrasive discs can be used to grind away the surface layer and expose clean metal.
- Abrasive blasting: Techniques like sandblasting or bead blasting can effectively remove contaminants and oxides.
Welding Procedure Variables and Adjustable Parameters
The welding procedure variables for GTAW include the type of filler metal, electrode type and size, the type of current, and the type of shielding gas. The primary adjustable variables for GTAW are:
- Welding Current: The amount of electrical current flowing through the welding circuit, which affects the heat input and penetration of the weld.
- Arc Length: The distance between the tungsten electrode and the workpiece, which influences the arc stability and weld bead shape.
- Travel Speed: The rate at which the welding torch is moved along the joint, affecting the weld bead width and penetration.
Secondary variables include work and travel angle, as well as the distance the electrode extends beyond the end of the cup.
Preheating and Temperature Control
Preheating may be necessary for GTAW, depending on the alloying elements in the base material, the thickness of the steel, and the configuration of the joint. The amount of preheat needed is typically specified in the welding procedure.
Preheating Methods
- Furnace heating: Using a furnace to raise the temperature of the entire workpiece.
- Electric induction coils: Generating a localized electromagnetic field to heat the weld area.
- Oxyfuel torches: Using a combination of oxygen and fuel gas to preheat the joint.
- Resistance heating blankets: Applying a heating element directly to the workpiece.
GTAW Welding Setup and Techniques
There are several methods that can be used for a TIG welding setup, including:
- Scratch Starts: The welder scratches the tip of the tungsten electrode on the workpiece to initiate the arc.
- Lift Starts: The welder uses a foot pedal to lift the tungsten off the workpiece, starting the arc without any jumping.
- High-Frequency Starts: An electrical circuit generates a high-frequency voltage to start the arc without touching the workpiece.
In a TIG welding setup, the welder holds the torch in one hand and feeds the filler rod into the weld pool with the other hand, while controlling the electrical current with a foot pedal or other device.
Applications and Considerations
GTAW is especially well-suited for welding thin metals, ranging from sheet metal up to 1/4 inch thick. It can be used on a variety of ferrous and nonferrous materials, and in all welding positions, to produce smooth and sound welds with fewer spatters.
However, it is crucial to avoid contamination of the weld pool. If tungsten is transferred to the molten weld pool during welding, it can contaminate the weld, and the resulting tungsten inclusion is hard and brittle. Weld metal contamination can also occur if the filler rod end comes out of the inert gas shield.
Technical Specifications
- The tungsten electrode used in GTAW has a high melting temperature of about 6,170 degrees Fahrenheit (3,410 degrees Celsius).
- The size of the filler metal wire depends on the thickness of the base metal, which usually dictates the welding current.
Conclusion
GTAW welding temperature is over 6,000 degrees Fahrenheit, making it essential to take necessary precautions when welding to prevent accidents or injuries. The precision required in this process means that the welder must have a steady hand and a keen eye for detail, making it a challenging but rewarding technique.
By properly preparing the weld joint, cleaning the material, controlling the welding parameters, and using the appropriate setup and techniques, you can produce high-quality GTAW welds with fewer spatters and contamination issues.
References:
– Gas Tungsten Arc Welding (GTAW) – Wikipedia
– Gas Tungsten Arc Welding Fundamentals: Understanding GTAW – The Fabricator
– TIG Welding (Gas Tungsten Arc Welding) – Universal Technical Institute
– Experimental Study on the Influence of Welding Parameters on the Mechanical Properties of GTAW Welded Joints – SCIRP
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