Effect of thermo mechanical control process on microstructure and properties of a non-quenched and tempered steel

Effect of thermo-mechanical control process (TMCP) on microstructure and mechanical properties of a non-quenched and tempered steel were discussed. The optimum controlled cooling technique to F40MnV steel steering knuckle after forging was obtained by forced-air cooling at local places. The results show that the local controlled cooling process can efficiently enhance the mechanical properties of the steering knuckle. When the forging temperature ranges from 1273 to 1373 K, grain size of the steel gradually refines from 26 to 12 μm with increasing strain from 0.22 to 1.61. With decreasing of forging temperature at 1173-1473 K, the deformation resistance of the non-quenched and tempered steel increases and its grain size is refined from 20 to 11 μm. The mechanical properties of F40MnV non-quenched steel can be efficiently improved by the combination of increasing forging ratio and local controlled cooling technique.