Study On Heat Treatment Behavior Of Stainless Steel Clad Plate

Stainless steel clad plate combines the excellent mechanical properties of the carbon steel substrate and high corrosion resistance of stainless steel cladding,which allows for the possibility of saving precious alloy elements and reducing the cost.More and more attention has been paid to it in the automotive,petroleum,chemical,ship and other fields with great economic and social benefits.Series of SUS304/Q235 stainless steel clad plates were fabricated by symmetry assemble technique and vacuum hot rolling at different hot rolling temperatures?1100^oC,1200^oC and 1300^oC?.Herein,the clad plate rolled at 1100^oC was chosen to study the effect of the quenching temperature and time on microstructure and properties.Subsequently,the ultimate strength of carbon steel substrate,corrosion resistance of stainless steel cladding and interfacial bonding strength can be improved by quenching heat treatment.The effect of quenching on the microstructures,element distribution,hardness,shear performance and tensile behavior of stainless steel clad plates were discussed.The conclusions are as follows:Bending tests show that the clad plate rolled at1100^oC has high bending strength and toughness,which could hinder the crack propagation at a certain extent.So the clad plate rolled at 1100^oC was selected as object for heat treatment.Stainless steel clad plate can be divided into five areas:stainless steel cladding,carburized layer,interface line,decarburized layer and carbon steel substrate.It is revealed that grain boundaries of carburized layer are the precipitation sites of chromium carbide during the quenching temperatures from 900^oC to 1050^oC,leading to low corrosion resistance due to the formation of intergranular corrosion crack.Precipitation amount decreases with the increase of quenching temperature.And precipitation are completely disappeared for sample quenched at 1100^oC.In addition,holding time have little effect on the precipitation of carbide chromium.It is observed that the microstructure of carbon steel substrate was changed from ferrite and pearlite to lath martensite and retained austenite phases after quenching treatment.The bainite phases amount and the grain size are gradually increased with the increase of quenching temperature and holding time.For stainless steel cladding the size of austenite and twinning grain was also increased with the increasing quenching temperature and holding time.The alloying element diffusion layer is formed at the clad interface.The microstructure of stainless steel clad plate quenched at 1100^oC for 6min is optimal.The microhardness of the clad interface was increased with the increase of quenching temperature.The interfacial microstructure was martensite and the dispersed Cr₂₃C₆.The microhardness of carbon steel is decreased with the increase of quenching temperature and holding time,which is due to the overheating of the structure and formation of bainite.The interfacial shear strength is increased with the increase of quenching temperature.The shear fracture location of different quenching temperatures changes from the interface?900^oC?to the decarburized layer?1000^oC?,indicating that the real interfacial bonding strength is higher than that of the decarburized layer.The tensile testing results show that the ultimate strength and the fracture elongation of the stainless steel clad plate is decreased with the increase of quenching temperature and holding time,which are mainly due to the softening of the matrix at high temperature,overheating of the structure,coarsening of grains and the decreasing dislocation density.The dimple shape of the tensile fracture morphology was changed from stable growth to unstable growth,and the fracture mode gradually changed from ductile fracture to brittle fracture.To ensure the corrosion resistance and mechanical properties of clad plates,the optimal quenching process is 1100^oC insulation 6min.