Study On The Reaction Mechanism Of Rare Earth Elements And Microalloying Elements In The Smelting Process Of Ship Steel

The research on the preparation of ship plate steel for rare earth and microalloys mainly focuses on the substitution research of precious microalloying elements,the influence of single and composite trace elements on the properties of rolled materials,and the research on the properties of rolled materials by adding rare earth and then adjusting the rolling process.However,However,However,the effect of single and composite rare earth elements on the microstructure and mechanical properties of steel is still unclear.Therefore,This project adopts arc smelting and induction smelting.On the basis of composite addition of alloying elements AH36 and AH32,the single and composite rare earths La,Ce and Pr are added to study the effect of rare earth elements on microstructure and mechanical properties of ship plate steel.The results of metallographic observation by Zeiss microscope and scanning electron microscope showed that the addition of rare earth elements to AH36 and AH32 steel can significantly refine the grains,which can transform the slab-shaped and polygonal ferrite into acicular ferrite and promote the layer,promote lamellar pearlite formation,with the increase of rare earth content,the structure was more uniform and the grains were more refined.The energy spectrum analysis of the inclusions by EDS showed that the rare earth elements were mainly distributed in the steel in the form of inclusions,and the main components of the inclusions were S,Al,Mn,Ca and rare earth elements.The coarse Al₂O₃ and long strips of MnS inclusions converted into small spherical rare earth aluminate and rare earth manganese sulfide inclusions.The effect on the modification of inclusions was obvious.Scanning electron microscopy observation of the fracture samples showed that the rare earth elements can change the fracture morphology,which maked the dimples change from polygonal to equiaxed,the dimples were deepened,its size became smaller,the distribution was more uniform,The inclusions were evenly distributed at the bottom of the dimple.The comparative study on the microstructure and properties of steel by arc smelting and induction melting in AH36 showed that the microstructure of the sample obtained by arc melting was more uniform,the number of rare earth inclusions was more,the hardness was higher,The arc smelting method was superior to induction smelting.By comparing the microstructure and properties of AH36 steel with single and composite rare earth elements,the results showed that the microstructure and properties of the composite rare earth elements were better than the single addition.From the mechanical properties and economic considerations,the optimal addition amount of rare earth was determined as follows:The single addition of 0.015%rare earth element in AH36 increased the Rockwell hardness by 13%;The single addition of 0.02%rare earth element in AH32 increased the Rockwell hardness by 12%;The compound addition of 0.015%rare earth element in AH36 increased the Rockwell hardness by 20%.