Final answer:
The four main zones of welding include the weld metal zone, the heat-affected zone, the unaffected base metal zone, and the weld interface zone. Each zone has different characteristics and properties due to the heat treatment during the welding process.
Step-by-step explanation:
The four main zones of the welding process include the weld metal zone, the heat-affected zone (HAZ), the unaffected base metal zone, and the weld interface zone. The weld metal zone is formed from the filler metal that has melted and solidified. The heat-affected zone (HAZ) is an area surrounding the weld, which hasn't melted but has experienced changes in its material properties due to exposure to high temperatures. The unaffected base metal zone is the area that remains completely unaffected by the heat. Lastly, the weld interface zone is where the weld metal and the HAZ meet, acting as a transition area from the weld metal to the base metal.
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