[2] For steel there are three major failure modes by which weldability can be measured: hydrogen-induced cold cracking, lamellar tearing, and spot-weld peeling.
In order to be able to judge alloys made up of many distinct materials, a measure known as the equivalent carbon content is used to compare the relative weldabilities of different alloys by comparing their properties to a plain carbon steel.
The effect on weldability of elements like chromium and vanadium, while not as great as carbon, is more significant than that of copper and nickel, for example.
Austenitic grades of stainless steels tend to be the most weldable, but they are especially susceptible to distortion due to their high coefficient of thermal expansion.
Aluminium alloys are susceptible to hot cracking, and to combat the problem, welders increase the welding speed to lower the heat input.
The design of the joint can be changed as well, and a more compatible filler alloy can be selected to decrease the likelihood of hot cracking.