What is the purpose of preheating the workpiece in GTAW?

Preheating the workpiece in Gas Tungsten Arc Welding (GTAW) primarily serves to reduce stress and minimize the potential for cracking in the weld. When a metal is welded, rapid heating and cooling can take place, which introduces thermal stresses due to the differing rates of expansion and contraction. By preheating the workpiece, the material is brought closer to the temperature of the molten weld pool, which helps to mitigate these stresses.

The preheating process allows for a more uniform distribution of heat throughout the workpiece, which helps in reducing the temperature gradient. This is particularly important in materials that are more susceptible to thermal stress and cracking, such as high-carbon steels or certain alloys. By preventing rapid cooling, preheating also maintains the ductility of the weld area, enhancing its overall integrity and reducing the likelihood of defects such as cracks or warping.

The other options, while seemingly relevant, do not accurately capture the primary purpose of preheating in the context of GTAW. Enhancing the aesthetics of the weld does not directly correlate to the fundamental mechanical properties being addressed through preheating. Creating a more intense arc does not relate to the workpiece's physical state, and improving thermal conductivity is not the primary goal,