Gas Carburizing

Carburizing means introducing carbon into the surface layer of a steel. You do this in a furnace with a carbon-rich atmosphere, e.g. from gas or carbon powder. The steel absorbs the carbon, so after hardening it becomes hard and wear-resistant on the surface, while the core remains tough. When welding, you must be careful not to destroy the carburized layer by getting too hot or losing the shielding gas. If unsure, it's better to stress-relieve the parts before welding.