Study On Brass-Copper Cold-rolling Bonding And Annealing Process

Nickel brass is widely used in the fields of navigation,weaponry,home decoration and minting industry,due to its high plasticity,good corrosion resistance and anti-tarnishing properties.A new nickel brass for cold-rolling bonding was studied through alloy design,micro structure observation and performance test in the present work.The effect of material composition,rolling process and annealing on the mechanical properties of the nickel brass was obtained.The single pass cold-rolling bonding experiments were carried out with the adjustment of rolling speed,rolling temperature and reduction to obtain the key parameters affecting bonding strength.The effect of cold rolling of the bonded plate after annealing on the bonding interface was also studied.The experimental research work was also carried out to investigate the annealing on the bonding interface by changing annealing temperature and annealing time.Based on the experiments,the main results are shown as following:(1)With the increase of annealing temperature and the prolongation of annealing time,the hardness and strength of the nickel brass decrease rapidly at first and then keep in a stable range;while the elongation shows a rapid increase at the beginning and then a stable state.The elongation of the alloy can reach 62.5%with the annealing of 700?×1h,which can meet the requirement of the cold-rolling bonding process.Within the range of 15-35%,with the increase of the concentration of Zn,the elongation of the nickel brass shows a slight increase.(2)Rolling speed has important influence on the cold-rolling bonding process.With the decrease of the rolling speed,the successful bonding rate is significantly increased.With the single pass reduction rate 75%,when the rolling speed reduced from 1.1m/s to 0.025m/s,the successful bonding rate was improved from 56.3%to 100%.And the suitable heating of the blank is beneficial to improve the successful bonding rate in the process of cold-rolling bonding.(3)Single pass reduction is one of the most important factors affecting the cold-rolling bonding process.The effect of single pass reduction on the bonding performance within the reduction range of 50-86.3%was studied.The results showed that the successful bonding can be achieved when the reduction reaches or is higher than 68%.With the increase of the reduction,the interface trends to straight and the bonding strength increases.The bending times of the annealed composite plate(700?×1h)can be improved from 4 to 9 with increasing the reduction rate from 75.3%to 86.3%during cold-rolling process.(4)The cold rolling of the bonded plate after annealing plays an important role in the bonding strength.The bonding strength is dramatically enhanced from 50MPa to 97MPa with a Cold-rolling of bonded plate.(5)The annealing process has great influence on the bonding strength and the thickness of diffusion layer of the interface.The bonded plates prepared by cold-rolling bonding with the single pass reduction of 75.3%were anealed for an hour.With the increase of the annealing temperature from 600 to 800 ?,the diffusion distance of Zn increased from 28.94?m to 64.13?m,and the bending times can be increased from 2 to 7.