What parameter can affect the weld metal's mechanical properties?

The cooling rate significantly affects the mechanical properties of weld metal due to its impact on microstructural formation. When welding, the heat generated from the welding process raises the temperature of the base metal and filler material. After welding, the weld joint cools down, and the rate at which it cools can influence the final metallurgical structure.

A slower cooling rate generally allows for the formation of larger grains in the metal, which can lead to lower strength and toughness. Conversely, a faster cooling rate tends to produce finer grains and can enhance strength, leading to improved hardness and enhanced mechanical properties. This reinforces the idea that controlling cooling rate is crucial for achieving desired characteristics, such as strength, ductility, and toughness, in the weld metal.

While other factors like electrode type, welding speed, and gas flow rate can affect weld quality and properties, it is the cooling rate that primarily governs the transformation phases and the resultant microstructure of the weld metal, ultimately affecting mechanical properties.