Surface hardness
Surface hardness is the highest hardness level at the edge of a workpiece, developed through thermal or thermochemical treatments and influences behavior under mechanical load.
Physical-Chemical Mechanism of Action
Surface hardness arises from the arrangement of atoms in the upper micrograin. At elevated temperatures and under specific chemical environments, these atoms can organize into a harder crystal lattice, increasing hardness.
Metallurgical Relevance & Welding Risks
High surface hardness can better resist mechanical loads on the workpiece. However, it can also lead to cracking if the difference from the core hardness is too great. It also affects machinability and weldability of the material.
Workshop Practice & Action Instructions
To achieve optimal surface hardness, precisely control the temperature and time of the treatment. For steels with high carbon content (e.g., HSS), minimize the cooling time after welding to avoid cracking. Use a Rockwell hardness tester or Brinell hardness test for measurements.