Analysis of abnormal fracture of 30CrMnSiNi2A bolts

Abstract In modern industry, 30CrMnSiNi2A high-strength alloy steel, due to its high strength, good toughness, and fatigue resistance, is widely used in aerospace, high-end equipment manufacturing, and other fields, and is often used to make high-load bolt connectors. However, in recent years, due to the complex and harsh service environment, abnormal bolt fracture accidents have occurred frequently, posing a serious threat to equipment operation safety and production stability. In this paper, taking the abnormal fracture of 30CrMnSiNi2A bolts during a test with a pressure holding of 42 MPa for 5 min, pressurized to 41 MPa, as the research object, the causes of fracture were systematically studied through chemical composition analysis, macro-micro fracture observation, hydrogen content testing, optical microstructure observation, and mechanical properties testing. The results show that the chemical composition of the bolt meets the standard, the hardness meets the heat treatment specification, but the fracture shows typical hydrogen embrittlement fracture characteristics, and the hydrogen content exceeds the standard. In a comprehensive judgment, the bolt fracture is identified as a hydrogen delayed fracture. This study provides a theoretical basis and technical reference for the prevention of similar problems.