Carbon Equivalent
The carbon equivalent is a calculated value that sums up how various alloying elements affect the hardening behavior and cold cracking susceptibility of structural steels when welding. It helps pick the right welding process.
Physical-Chemical Mechanism of Action
The carbon equivalent (CE) is a sum that calculates the total effect of carbon and other elements like silicon, chromium, molybdenum, and nickel on a steel's hardening behavior. This calculation recognizes that certain elements act similarly to carbon and influence the steel's microstructure.
Metallurgical Relevance & Welding Risks
A high carbon equivalent leads to stronger hardening, which increases susceptibility to cold cracking. This can cause cracks and distortion in the weld. With a low CE, the structure is softer and less prone to cold cracking, but maybe not as strong as you'd want.
Shop Practice & Action Points
To calculate the carbon equivalent, add the amounts of carbon and the corresponding elements in % to the alloy. For example: CE = %Carbon + 0.5 x (%Silicon + %Chromium) + 1.25 x %Molybdenum + 3 x %Nickel.
Watch the CE when picking a welding process. For high CE (e.g., > 0.8%), go with processes like TIG welding because they give you precise control over hardness. With low CE, you can use less strict methods.