Researches On Behaviour Of Interface Bonding Of The Copper Clad Steel Sheet Fabricated By Cold Rolling

Metallic clad plates can maintain the properties of the base metal.Meanwhile,they have "complementary effect".Compared to the base metal,metallic clad plates have better mechanical properties and formabilities so that they have widespread application in the fields of vehicles,household appliances,weapons and architectural decoration,etc.At present,the researches on the cold-rolled metallic clad plates focus on the effect of the processing parameters on the bonding strength or mechanical properties,while lack in the analysis of the bonding process.In the paper,copper clad steel sheet is the research material,which is fabricated by the mean of "surface treatment and cold roll bonding",here in the carbon steel is taken as substrate and the cold-rolled pure copper is taken as cladding.Copper clad steel sheet combines the high conductivity and corrosion resistance of copper with the high strength,hardness and remarkable weldability of steel.This paper investigates the effect of cold rolling conditions on the interface bonding performance of the clad sheet using the finite element analysis.In addition,in order to study the effect of annealing treatment on the interface bonding behaviors,the interface statues and mechanical properties of the clad sheet after annealing,series of annealing treatments are conducted.The results show:In the cold roll bonding process,pre-bonding region of mechanical meshing will produce when the bonding points have produced,and atomic diffusion will take place in pre-bonding region when annealing.With the thickness reduction increasing from 50% to 66%,the unbonded region at the interface of the cold-rolled clad sheet decreases,and bonding area increases from 2% to 3%.After annealing,bonding area improves 3 times.The finite element simulation results show that normal pressure distributes uneven due to work hardening or other factors at the interface,and the proportion of the maximum normal pressure increases with the thickness reduction.Points whose normal pressure exceed 1100 MPa are taken as bonding points,the proportion of bonding points is in agreement with the experimental results.Diffusion layer thicknesses of clad sheet increase with annealing temperatures and annealing time.Diffusion layer thickness reaches 2.00 μm and keeps constant basically when annealing temperature exceeds 700°C.The thickness of diffusion layer decreases due to the cuprous oxide is reduced to iron oxide when annealing time exceeds 2 h.Micro-hardness test results show that the hardness of the copper clad steel sheet is higher than the cladding and lower than the substrate due to the solution strengthening.The hardness of the cladding,interface and substrate decrease with the increase of annealing temperatures.And the hardness of the cladding,interface and substrate decrease with the increase of annealing time until stable,the hardness of each layer is 58 HV,80 HV and 124 HV,respectively.The tensile test results show that the yield strength and tensile strength of copper clad steel sheet increase with the increase of thickness reduction,and the elongation of cold-rolled decrease with the increase of thickness reduction.During the drawing process of annealed samples,the delaminated cracks produce in the annealed clad sheet are shorter than the cold-rolled samples,and the necking phenomenon is obvious,which shows a better deformation coordination.