1.7225 | 42CrMo4 +QT defective

This very thick-walled, heat-treated forged component exhibits pronounced segregation lines.

As the distance from the surface increases, zones of predominantly acicular or granular upper bainite are accompanied by ultra-fine-striped pearlite and ferrite. Ultra-fine-striped pearlite (formerly known as ‘Troostite’) forms in former pearlite bands when the cooling rate is too low. The tensile strength is 820 MPa, the hardness 245 HBW 2.5/187.5.

Microhardness:

• needle-like upper bainite (light): 239 ± 7 HV 0.5
• granular upper bainite (dark): 272 ± 11 HV 0.5
• ultrafine-striped pearlite + ferrite: 251 ± 13 HV 0.5
• (pure troostite grain: 184 HV 0.3)