Research On Microstructure And Mechanical Properties Of Cr27 High-Cr Cast Iron With Embedded Steel Bars

Hypereutectic high-chromium cast iron is a common wear-resistant material in engineering.Because of its poor toughness,failure behaviors such as smashing and fracture are likely to occur under high impact stress conditions.The Cr27 highchromium cast iron selected for this project has a carbon equivalent of 4.467%,which is a typical hypereutectic high-chromium cast iron.Aiming at the characteristics of poor toughness,the research idea from the perspective of composite material is put forward.This project uses insert casting technology to combine high-hardness and lowtoughness high-chromium cast iron with high-toughness and low-hardness ductile materials to prepare composite materials.Two kinds of ductile materials are selected in this study,which are H08 low carbon steel and 304 stainless steel,respectively.Through the solid-liquid composite preparation technology in which the steel wire was fixed in the cavity and then poured the molten high-chromium cast iron,composite samples of high-chromium cast iron-low carbon steel and high-chromium cast ironstainless steel were successfully prepared.The influence of ductile materials on the interfacial bonding of composites,matrix structure and mechanical properties was studied by changing the casting process.The wear mechanism of the composites was studied on Wear Mechanism of Composites by Silt Wear Test.Research indicates:1,the interface between the two composites is well-bonded,there are no defects such as air bubbles,slag inclusions,and the interface bonding quality is positively correlated with the pouring temperature.A layer of ring-shaped austenite is formed at the interface of the low carbon steel-high chromium cast iron composite material.However,this structure is not observed at the interface of the stainless steel-high chromium cast iron composite material.The reason is the compositional difference between the two sides of the interface.This layer of looped tissue increases the strength of the interface connection.2,the addition of the steel wire allows the molten iron to rapidly cool after pouring into the cavity,forming a fine-grained high-chromium cast iron grain around the steel wire,so that the hardness and wear resistance of the matrix are both improved.With the increase of the diameter of the steel wire,this chilling effect is strengthened.At the same time,the internal steel wire undergoes a hightemperature annealing,and coarsening of the organization occurs and the plastic toughness of the steel wire is reduced.3,the composite material superimposes the different properties of the two materials.Although the insert casting technology sacrifices part of the plasticity of the steel wire,the overall impact toughness of the composite material is improved.When the steel wire volume fraction reaches 12.56%,the impact toughness of composite specimens of low carbon steel-high chromium cast iron and stainless steel-high chromium cast iron is increased by 1 and 4 times compared with that of single high chromium cast iron respectively.4,the pouring temperature is controlled at 1450°C,and choose the subcritical heat treatment at 525°C for 4 hours then with air cooling can achieve the best comprehensive mechanical properties of the two composites.Through the sand slurry abrasion test,it was found that the composite material has more fine crystal structure and the wear resistance of mud sand is higher.However,due to the poor resistance of ductile material to silt and sand,pits will be formed during wear.Therefore,in the actual preparation of composite materials,it is necessary to ensure that the steel wire is not exposed to the wear surface.