Analysis and Control on Fracture of 20Mn2A High Tensile Steel for Round Link Chain

摘要

Based on the phenomenon of brittle fracture occurred during tensile test for 20Mn2A high strength circular chain used in coal mines, the fracture property is regarded as intercrystalline brittle one after macroscope observation and metallographic examination. It is analysed that the intercrystalline brittle fracture is due to high tempering temperature and limited processing site where final products are piled together after heat treatment, which lead to a lower cooling rate of internal chain, with Si, Mn and P etc elements segregating and enriching in the austenite grain boundary and forming high tempering brittleness. After these circular chains are tempered again for one hour at 670℃, and oil-cooled rapidly, due to the reversibility of high temper brittleness for structural alloy steel, the high temper brittleness can be eliminated and products are completely qualified after tensile inspection.