| The resistance Spot welding is an important craft method to connect thin plate The spot welding electrode is one of the materials which will be the easiest failure in the whole process of spot welding. With the spot welding technology being applied into galvanized steel and high strength aluminum alloy connection fields, electrode failure problem is more conspicuous. Therefore, the research of long-life electrode materials is imperative.In this paper, Cr、Zr 、B three elements are added into Cu-Ni-Si alloy. By traditional alloying ways, it has made the copper alloy including five different contents which are Cu-2.8Ni-0.7Si-0.6Cr-0.15Zr(WNi/Si=4:1),Cu-2.8Ni-0.7Si-0.6Cr-0.15Zr-0.06B(WNi/Si=4:1),Cu-2.8Ni-0.9Si-0.6Cr-0.15Zr(WNi/Si﹤4:1),Cu-2.8Ni-0.56Si-0.6Cr-0.15Zr(WNi/Si﹥4:1) and Cu-0.6Cr-0.15 Zr. It also studies systematically the impacts of the distribution ratio of alloy and different heat treatment process on alloy electrical conductivity and mechanical properties. And the main research contents and results are as follows:1.The microscopic structure of Cu-Ni-Si-Cr-Zr as-cast is mainly composed of thick columnar crystals. There are large amounts of coarse surplus-phases in the matrix. At the same time, the addition of Ni, Si and B elements refining the microscopic structure of Cu-0.6Cr-0.15 Zr as-cast and decreasing the alloy electrical conductivity with increasing of its hardness2. The alloy solid solution treatment shows that with the temperature increasing of solid solution, the tendency of grain growth becomes more obvious and the conductivity and hardness fall quickly at the same time. The lowest conductivity is16.03% IACS and the lowest hardness is 94.7 HV.3. The composition and distribution of Cu-Ni-Si-Cr-Zr alloy in aging state component are analyzed, it has found that a large amount of Ni elements and a small amount of Si element is soluted in the matrix. The precipitates of matrix is mainly concentrated in the grain boundaries. The main components include Cr Si, Cu Zr,Ni Si, B etc. The morphology of the particles mainly has three kinds, which includes rectangular, oval, circular.4. After aging treatments of Cu-Ni-Si-Cr-Zr, its conductivity and hardness will rebound largely. In the early aging, the conductivity of Cu-Ni-Si-Cr-Zr has a rapid rising, and the higher ageing temperature is, the shorter the time conductivityreaches its peak. while with prolonged aging, the electrical conductivity rises slowly and then it will be stabilized finally. For the alloy hardness, when the aging temperature is 450℃ and 500℃, the hardness rises rapidly and it will be stabilized later too. But in the early of reaching 550 ℃ aging temperature,the alloys will present the over-aging phenomenon, and the hardness shows a downward trend.5.The sorting of conductivity peak based on aging state of Cu-Ni-Si-Cr-Zr alloy shows that:%IACS(Ni/Si=4:1)>%IACS(Ni/Si=4:1,0.06B)>%IACS(Ni/Si>4:1)>%IACS(Ni/Si<4:1);the sorting of hardness peak are as follows: HV(Ni/Si<4:1)>HV(Ni/Si=4:1,0.06B)>HV(Ni/Si=4:1)>HV(Ni/Si>4:1).The hardness peak is little affected by alloy composition between 20 HVand 30HV. The conductivity peak is little affected too by alloy composition between 4%IACS and 9%IA CS.6.In this paper, the prepared copper alloy have a good performance of re sisting high temperature softening. The hardness of alloys will decreases with increasing temperature, when the temperature increased to 550℃-600℃ range,the alloy hardness sharply declines. The alloy softening temperatures above 550℃,which Cu-2.8Ni-0.7Si-0.6Cr-0.15 Zr softening temperature reached a maxim um 601℃. |
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