Research On Welding And Replacement Mechanism Of Continuous Extrusion Of Copper

With the development of high-voltage power,electronics,information,and high-speed railway industries,the demand for copper and copper alloy rods and wires,especially high-precision copper rods,is increasing.At the same time,the development trend of the world copper processing industry is towards high precision,high surface,and high consistent performance.The new process requires energy-saving,environmental protection,low carbon continuous,and short process.Since continuous extrusion technology has the advantages of high efficiency,low cost,and excellent micro structure of product,which meets the overall requirements of the development direction of copper processing technology,it is an inevitable trend to apply this technique to copper processing.However,in practice,product defects always emerge during the production process.Continuous extrusion of copper products within a certain depth from the surface sometimes has delamination defects and internal inclusions.The rod blank fed into the squeezing wheel under high pressure will be welded and replaced with the remaining material in the wheel groove.Whether the weld parts of the matrix and the welded metal would be separated during the expansion forming process,determines the product’s micro structure and performance.The present work takes TLJ250 continuous extruder as the main experimental equipment,conducting the welding experiment by simulating the environment of continuous extrusion,analyzing the influence of different factors on the welding quality of copper material,and verifying it by actual continuous extrusion experiment.At the same time,aiming at the problem of inclusions inside the product,the replacement experiment was carried out to analyse the distribution of the inclusions and the underlying cause.The problem of internal inclusions of the product was solved by improving the fixture and processing parameters.The research results indicates:The effect of temperature on the welding quality: under a certain unit pressure,when the temperature is between 550℃ and 600℃,the tensile strength and hardness of the sample at room temperature showed an increasing trend;when the temperature is between 600℃ and700℃,the tensile strength and hardness of the sample at room temperature showed a downward trend.The influence of unit pressure on the welding quality: under a certain temperature,as the unit pressure increases from 200 Mpa to 800 MPa,the tensile strength and hardness of the welding sample at room temperature gradually increase.The effect of grain size on welding quality: under the same temperature and unit pressure welding conditions,the room temperature tensile strength and hardness of the fine-grainedwelding samples are significantly higher than those of the casting-slab coarse crystal welded samples.The influence of the thickness of the remaining material on both sides of the wheel groove: reducing the thickness of the remaining material on both sides of the wheel groove,the defects in the product are also reduced.The effect of changing the flash gap: the product defect of the flash gap of 0.6mm is less than that of the flash gap of 0.3mmThe effect of improving the wheel groove structure of the extrusion wheel: extending the depth of the wheel groove boss can reduce the remaining material,and the defects of the product even disappear completely.The research results showed that the TLJ250 continuous extruder has successfully produced a ?12.5mm product at an extrusion wheel speed of 4rpm using an original ?8mm continuous casting copper rod.By reducing the thickness of the remaining material on both sides of the wheel groove,the overflow gap is 0.6mm.Improved wheel grooves can eliminate product defects.