Identification of Internal Defects in the Forging of the Rotary Shaft Made of Steel Grade 35crni1mo

In the article a detailed study was conducted to identify defects identified during the narrow forging of a 35CrNi1Mo rotary shaft (ingot weight 71.5t). It is shown that most of the cracks are located in the zone of off-axis liquation. The conducted studies using optical microscopy methods have shown the porous nature of cracks with a fine crystalline structure. Electronic fractography of fractures by defects also showed that this type of defect is surrounded by non-metallic inclusions (MnS-FeS) characteristic of the zone of off-axis liquation of the ingot. According to the totality of metallographic features, after the conducted studies, these defects are classified as floccules.