Study On The High Temperature Creep Character At The Clad Steel Interface

The cladding material Composite steel has the characteristics of corro-sion resistance, abrasion resistance, conductivity, and resistance to vibration. The base-layer material has the characteristics of high strength. Those charac-teristics make composite steel save the production cost, and improve the per-formance of the steel plate. With the development of science and technology, the process equipment is under high pressure effect and high temperature, so the material demand is higher and higher. The composite steel plate for its good suitability and economy, is more and more widely used in the national pillar industry, such as the military-industrial complex, metallurgy, chemical industry, petroleum, natural gas, Marine, shipbuilding, nuclear power countries. However, clad steel in the process of manufacturing and processing technology, the inter-face of base layer and clad layer of clad steel plate is easy to produce defects such as Impurities, porosity and dislocation. And there is a big difference be-tween the clad layer material and base layer material of the clad steel plate in thermal expansion coefficient, chemical composition and microstructure. Under the action of external load and high temperature for a long time, it lead to a creep rupture at the interface, and make the interface has become one of the im-portant failure part of composite steel plate.Due to the stringent craft requirements, the long experiment cycle of the high temperature creep experiment, the difficulty of reflecting creep property at interface and other practical factors, the high-temperature creep experiment for the interface of the clad steel plate is too difficult to achieve. Finite element analysis method solves the engineering problem which cannot be solved exactly by approximate solution. At the same time, it also has the advantage of short time-consuming and low cost. It has been widely used on the study of material high temperature creep. Therefore, by using finite element numerical analysis method, this paper conducted in-depth research for composite steel plate inter-face of high temperature creep properties. Based on the elastic mechanics and the viscoelastic mechanics theory, this paper carried on the theoretical research about the high temperature creep properties of the interface between composite steel plates. The interface stress, creep strain, creep and creep characteristics changing over time of each node and creep characteristics of clad steel plate in-terface which effected by different position of the original defects in materials are analyzed through the finite element numerical analysis method.Through the theoretical research and numerical simulation of high temperature creep properties at the composite steel plate interface, The follow-ing conclusions are derived:(1) Theoretical study:Through the differential constitutive relations of generalized Calvin model of metal material, the creep viscoelastic constitutive equation of the clad steel plate internal pressure cylinder is deduced. The creep constitutive equation of the material which contains the original cavernous de-fects is also studied.(2) The numerical simulation:Creep stress jumped at the interface between the base-layer and clad-layer of the clad steel plate under the same temperature and external load. The creep stress of clad-layer decreases with time, the creep stress of base-layer increases with time, and the creep strain of the both increases with time. Under the constant load, Creep stress difference and the value of creep strain at interface of the clad steel plate increase when the op- erating temperature increases.(3) When the original cavernous defect exists in the clad steel plate, the stress of the hole edge concentrates, and the creep stress and creep strain dis-tributions near the hole present butterfly. When there is a cavernous defect in the clad-plate, compared with the zero defect clad steel plate, the differences of the creep stress and the creep strain at the interface increase; when there is a cav-ernous defect in the base-plate, the creep stress difference is smaller at the inter-face, and there is no significant mutations of the creep strain; when there is a cavernous defect at the interface, along the barrel radial direction, the creep strain reduces gradually and keep continuous at the interface.The research results of this paper provides the reliable theory basis for the use of clad steel under high temperature conditions.