| Steel/aluminum clad plate combines the advantages of high strength and toughness of steel with excellent electrical and thermal conductivity,corrosion resistance and low density of aluminum.It is widely used in radiators,electro-thermal transmission,petrochemical,automotive,marine,water conservancy and hydropower,environmental protection and other fields.The thickness of the product ranges from tens of microns to tens of millimeters,and the layer thickness ratio of steel and aluminum is also large.For example,the thickness of steel/aluminum clad plate such as automobile radiator fins and electric heat transfer sheets is usually less than 2mm,while the thickness of steel/aluminum transition joints for large ships is more than 30 mm or even 60 mm.For thick steel/aluminum clad plate,the main forming process is explosion-welded process,but the defects of pollution,noise and low automation of this process also force researchers to explore alternative processes continuously.Rolling-bonding process is widely used in production of metal sheet due to its stable production,high efficiency,easy industrialization,strong process controllability,and smooth surface after rolling.This paper hopes to introduce this way to prepare the thin steel/aluminum composite sheet to produce thick steel/aluminum clad plate.This way can be used to replace the explosion-welded process in the fabrication of thick steel/aluminum clad plate to achieve purpose of batch production.Three kinds of methods are used in the experiment.The first one is to prepare thick steel/aluminum clad plate by conventional hot rolling compounding method.The interface bonding effects of multi-pass rolling under small reduction rate and single pass rolling under large reduction rate are investigated respectively,which are determined by shear strength and micro interface.The second one is to conduct hot rolling experiments on the basis of plasma-spraying steel plate with siliconaluminum alloy ZL102.The effects of rolling pass,temperature and reduction rate on interface structure and bond strength are investigated.The third one is to conduct hot rolling experiments on the basis of hot-dip silicon-aluminum alloy ZL102 process.After the optimal hot-dip time is determined,the influence of the rolling reduction rate and the temperature on the bonding strength and the micro interface is analyzed by a single variable method.The shear strength test,metallographic microscope,SEM,EDS and hardness test are carried out to analyze the combination performance.It is found that the deformation and thinning mainly occur on the aluminum plate,and the shape of steel plate has not changed.In the conventional hot-rolling process,the interfacial shear strength of the steel/aluminum clad plate prepared by multi-pass rolling under small reduction rate and single pass rolling under large reduction rate is very low,and metallurgical bonding in the interface does not formed.In this case,it is only one-sided pursuit of an increase reduction for enhancing the bonding performance of the thick steel/aluminum clad plate.In the plasma spraying + hot rolling process,the steel/coating interface forms a metallurgical bonding.The thick steel/aluminum composite plate by single-pass rolling has a better bonding effect.The rolling speed has little effect on the bonding strength of the prepared steel/aluminum composite plate.As the rolling reduction increases,the bonding strength of the steel/aluminum composite plate increases gradually,and the interface defects are gradually improved.After rolling,the thickness of the diffusion layer slightly decreases.There are still some defects in the steel/coating interface after rolling at 400°C.The defects in the steel/coating interface rolled at 450°C basically disappear,and cracks begin to occur in the interface at 500°C,and the shear strength also increases first and then decreases with rolling temperature.The bonding performance is optimal and the maximum shear strength reaches 66.4 MPa when plasma spraying ZL102 is adopted,the reduction rate is 40% and the rolling temperature is 450°C.In the hot-dip aluminum + hot rolling process,as the hot-dip time increases,the surface quality tends to be good.Within the 5 min,the thickness of the reaction layer increased gradually.After 5 min,the thickness of the diffusion layer gradually decreased.The shear strength of the steel/aluminum composite plate after hot-dip ZL102 increases with the increase of hot-dip time of the steel plate,but after 4 min,the shear strength decreases with the increase of hot-dip time.After hot-dip aluminum,there is a clear and straight boundary between the diffusion layer and the steel matrix,and the interface between the diffusion layer and the coating exhibits an irregular shape.During the heating process before rolling,the diffusion layer is further growing,and the diffusion layer is zigzag-shaped toward the coating,and branch-shaped compounds appear in the coating.As the reduction ratio increases,the shear strength increases first and then decreases.There is an obvious crack in the coating/Al interface rolled at reduction rate of 26.7%,and there is an obvious crack in the steel/coating interface rolled at reduction rate of 40%.As the rolling temperature increases,the shear strength first increases and then decreases.At the rolling temperature of 400°C,cracks of different sizes occur in the diffuse layer,and the diffuse layer becomes very irregular at 500°C.The bonding performance is the best and the maximum shear strength reaches 61.6MPa when the time of hot-dip ZL102 is 4min and the reduction rate is 33.3%,the rolling temperature is 450°C. |
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