Microstructure and mechanical properties of multi-pass forged and annealed 42CrMo steel

In this work, we investigate the effects of multi-pass forging and annealing treatment on the microstructure and mechanical properties of 42CrMo steel. The homogenized specimens were firstly multi-pass forged at 1100 degrees C followed by air cooling, and then were annealed for 1 h at 400 degrees C, 500 degrees C, 600 degrees C, and 700 degrees C, respectively. It is found that the average prior austenite grain size of the homogenized material is refined from 273 +/- 78 mu m to 12 +/- 1 mu m accompanied by an increased dislocation density from 6.09 x 1014 m- 2 to 2.35 x 1015 m- 2 after multipass forging. As a result, the yield stress of the as-forged specimen is 1.7 times that of the homogenized counterparts. Annealed at different temperatures ranging from 400 degrees C to 700 degrees C after forging, the yield stress of the forged specimen reduces from 798 MPa to 522 MPa with an enhancement of elongation from 8% to 16%. The corresponding fracture features experience brittle-ductile transition. The results are attributed to gradually spheroidized pearlite and reduced dislocation density with increasing annealing temperature.

Automated summary

The effects of multi-pass forging and annealing treatment on the microstructure and mechanical properties of 42CrMo steel were investigated in this work. The results show that multi-pass forging can refine the grain size and increase dislocation density, leading to higher yield stress. Annealing at different temperatures after forging can reduce the yield stress and improve elongation, with corresponding brittle-ductile transition in fracture features.