The Study On Microstructure And Mechanical Property Of 304 Stainless Steel-High Chromium Cast Iron Wear-resistant Composite Pipe

Waterway transportation is one of the most important transportation in this world,but silt silting is needed in many important rivers and ports.At present,as dredging equipment,mud pipe is usually made of carbon steel or low alloy steel.The low hardness and wear resistance make the pipe wear seriously and need to be replaced frequently.However,if the materials with high hardness and abrasion resistance are good,they can cause crack and even safety accidents.Because the single material is difficult to meet the comprehensive demand of high hardness,high wear resistance and good toughness,it is proposed to use bimetal composite as the pipe material.The bimetal composite pipe used in this paper is a 304 stainless steel-high chromium cast iron wear-resistant composite pipe made by centrifugal casting.The inner layer is high chromium cast iron with high hardness and good wear resistance,and the outer layer is304 stainless steel with good toughness.These make the bimetal composite pipe have good comprehensive mechanical properties.In this paper,wear-resistant composite pipe as the research object,using metallographic microscope,electron microprobe,scanning electron microscope,universal testing machine,impact testing machine and ANSYS simulation software on the inner tissue formation,elements distribution,mechanical properties and the formation of prestress were discussedThe study of the composite pipe shows that the microstructure of the inner layer is eutectic carbide,martensite and retained austenite,and the grain near the interface is finer than the inner surface,and has a clear direction.This is due to the fact that the heat transfer is mainly done through the interface,where the temperature gradient is relatively large.The element distribution of the inner layer is special,which is due to the common influence of centrifugal force and the viscosity resistance of metal liquid.The eutectic point of high chromium cast iron is not only related to the carbon content,but also has a certain relation with chromium and silicon.Therefore,the segregation of element will lead to different eutectic points of each thickness of the inner layer,which causes different amounts of carbides in different positions,resulting in the gradient change of hardness in the inner layer.The mechanical properties test shows that the hardness of bimetal compared pipe shows gradient change.The wear resistance of the inner layer is more than four times that of 45 steel,indicating that its wear resistance is better.The tensile strength is414.52MPa which is slightly lower than that of 304 stainless steel made by centrifugal casting.The interfacial shear strength is 502MPa,which indicates that its combination is good.Impact toughness is between 100 and 200J/cm~2,between high chromium cast iron and stainless steel.Using the SEM to analyze it,the fracture mechanism of the high chrome cast is a brittle fracture,and the stainless steel is broken.The combination of the two does not affect the stainless steel fracture.The simulation of temperature field and stress field are carried out on the centrifugal casting process using ANSYS.The results show that after the bimetal composite pipe is removed from the mould,the stress is gradually increased.High chrome cast-iron layer forms pressure,reaches 340MPa,and the stainless steel layer forms tensile stresses,reaches 162MPa.