CAUSES OF STRESS-RELIEF CRACKS IN FORGED DIFFERENTIAL GEAR

The article investigates the formation of stress-relief cracking and lamellar cracking in steel forgings used for differential gears for transport components. The forging and heat treatment processes, conducted under consistent technological conditions, revealed the occurrence of carburizing annealing cracks caused by plasticity depletion during stress relaxation. Additionally, stress-relief cracks were microstructurally analyzed, and the primary cause of the disturbance of the equilibrium state, which resulted in the formation of these cracks, was sought. Die-tool wear and damage during forging were identified as key contributors to the formation of non-metallic oxide inclusion, transferring surface defects and creating lamellar propagation during subsequent heat treatment. The findings underscore the influence of tooling conditions and process parameters on the quality and reliability of steel forgings.