Research On High Conductivity Copper And Copper Alloy

Due to the great harm of impurity iron to copper,it is necessary to find an alloy element that can be used to remove iron from oxygen-free copper rods.This article takes copper and copper alloys for electrified railways as the main body,and prepares a series of alloy samples with A-grade copper as raw materials.By comparing the electrical conductivity,tensile strength and other properties of the alloy samples,using optical microscope and scanning electron microscope to observe the structure and analyze it in combination with thermodynamic calculations,the focus is on the effect of boron in removing iron from pure copper and the influence of trace boron on copper alloys for electrified railways.The conclusions are as follows:1.The effect of boron in removing iron from copper is very significant.A proper amount of boron can restore the conductivity of iron-containing copper to the level of pure copper.Thermodynamic calculations show that when the iron content is only 75ppm,iron and boron will react to form FeB at about 900?.Therefore,iron and boron react during high-temperature heat treatment to achieve the effect of iron removal.Adding a trace amount of boron can not improve the conductivity of oxygen-free copper conductors made of A-grade copper,but can refine the crystal grains of pure copper.2.Adding a trace amount of boron to the copper-magnesium alloy for contact wires can increase the strength of the alloy,and has a minimal effect on the conductivity of the alloy.After adding 10ppm boron,the tensile strength of the copper-magnesium alloy is increased by about 5MPa;the yield strength is increased by about 10MPa.Thermodynamic calculations show that adding boron to copper-magnesium alloys(magnesium content greater than 0.2%)will generate MgB4 instead of MgB2.The microstructure map shows that the grains of the copper-magnesium alloy have been refined after adding boron.Therefore,the increase in the strength of copper-magnesium alloys is jointly affected by the formation of magnesium-boron compounds and the grain refinement of the alloy.3.The addition of trace boron can increase the tensile strength of the copper-chromium-zirconium alloy for contact wires,and has a minimal effect on the conductivity of the alloy.After adding 20ppm boron,the tensile strength of Cu-0.3Cr-0.1Zr alloy is increased by 10MPa.Thermodynamic calculations have found that by adding boron to Cu-0.3Cr-0.1Zr alloy,boron may react with chromium and zirconium,but when the boron content is small,boron will preferentially react with zirconium to form ZrB2.The increase in the strength of copper-chromium-zirconium alloy may be related to the formation of ZrB2 and CrB2.