Abstract: Cracks were found during the machining process, on the surface of some forged track links of 35MnB steel produced in a certain batch. In order to find the cause of crack formation and prevent further problems in subsequent production, macroscopic analysis and microscopic morphology observation were conducted on the surface cracks of the 35MnB forged track links, and composition analysis was performed using an energy spectrometer. The chemical composition, non-metallic inclusions, and microstructure of the defective and normal parts were compared and analyzed. The results indicate that the heating temperature before forging is too high, which results in coarse austenite grains and the precipitation of manganese sulfide particles on the grain boundaries, and leads to poor bonding force at the grain boundaries. The main reason for the formation of such defects is grain boundary cracking during forging. Burning occurs due to excessive heating temperature, which is an irreversible defect. Properly selecting the heating temperature or shortening the residence time in the high temperature range can avoid the formation of such defects.

Key words: 35MnB steel, forged track links, burning, grain boundary cracking