Study On Failure Behavior Of Large-scale Casting Stainless Steel Valve Body

Facilities made by cast stainless steel are usually used as the important equipment in processing technique that are highly required for corrosion-resistant, resistance to elevated temperatures and hygienic conditions, so it will Cause abnormal shutdown and even cause property damage and endanger Personnel safety if equipment failure. Through Finite element method and Physical Testing Methods to find out the reason of failure on large failure cast stainless steel of one petrochemical factory, and put forward relevant prevention measures.Base on the basic theories of crack propagation and physical testing and chemical analysis methods were used to systematically analysis the kind of failure in valve body, failure model, fracture morphology, operation conditions, materials, production and maintenance, etc. And analysis the failure reason basic on the morphology of feature, working atmosphere and other elements.It is found that carbon and Silicon content in material are higher, and shrinkage defects are existed in materials internal, especially in the import and export of straight section connection with abdominal cavity is very seriously found by physical testing and chemical analysis. And energy spectrum analysis indicates that carbon was reach 50% in some grain boundary.FEM (Finite element method) soft (ANSYS) was used to calculate the structural stress distribution on Valve in Steady-state operation and fluctuations may occur in production conditions. The results indicated that stress of structure is low in steady-state operation, but there appear stress concentration in import and export of straight section connection with abdominal cavity inner surface; and stress concentration also appear in the same position in and out surface when flashboard shut down.Finally,comprehensive analysis the failure reason of valve body combined with the rest of physical testing and chemical analysis and FEM analysis. The results showed that the root reason for valve body failure was seriously casting defect exist and its big and density shrinkage porosity form the original crack; and structure stress and its fluctuated make crack expand; and its worked condition in high temperature and hydrogenous environment made material trend to embrittlement which had accelerated cracks'expand.