Reason Analysis on Low Impact Energy of 40CrNiMoA Steel Bar

Chemical composition, mechanical properties and microstructure were inspected to analyze the reason leading to impact property degradation and directivity of one batch 40CrNiMoA steel bars. The results showed that the banded structure in microstructure giving rises to the bad impact performance, and isothermal annealing was employed to eliminate banded structure for satisfying impact energy after analyze the reason of banded structure.