At the 2024 (19th) SMM Copper Conference and Copper Industry Expo - Copper Bar Industry Development Forum, jointly organized by Shanghai Nonferrous Metals Network (SMM) and Shandong Hengbang Smelting Co., Ltd., Li Zengde, director of the Advanced Copper Alloy Research Institute of GRI Engineering Technology Research Institute Co., Ltd., shared the research status of advanced copper alloy bars for automotive spot welding.
1. Overview of advanced copper alloy bars for automotive spot welding
As the core material of automotive spot welding galvanized steel plate, automotive spot welding electrode has broad prospects for future development
• In 2023, Continental passenger car sales will grow rapidly, reaching 30.161 million units and 30.094 million units, respectively, a year-on-year increase of 11.6% and 12%, a record high.
• At present, the automotive industry is in the adjustment stage due to the impact of many parties, but the increase of electric vehicles is relatively rapid, and the annual market demand for electrode materials is about 80 million yuan, and the market size is expected to exceed 150 million yuan by 2025, with a compound annual growth rate of more than 20%.
In order to "reduce weight and save energy" and improve crash safety standards, the wide application of high-strength galvanized steel sheet has been born
The application of ultra-high strength galvanized (≥100g/m2) automotive steel plate includes: automotive exterior plate (engine hood outer panel, side panel, car cover, etc.), body structure (bottom cross member, anti-collision reinforcement member, suspension structure member, side beam, bottom longitudinal member, etc.).
Pain points: The challenge of welding high-strength galvanized automotive steel strip, traditional welding materials in the process of automobile welding cause an increase in accident rate, a decrease in quality stability, and a decrease in production efficiency, which brings huge losses to the automobile industry
The development of automotive steel plate to ultra-high strength (≥1400MPa) brings great challenges to the quality stability of automotive welding (pressure and current). The increase in the amount of galvanizing of automotive steel sheets has increased the downtime accident rate caused by "sticking" during the welding process by 15%.
The new generation of automotive spot welding electrode materials is the simplest and most effective way to weld high-strength galvanized automotive steel plates!
For ultra-high-strength galvanized automotive applications, alumina-copper materials become an excellent solution
2. Research status of advanced copper alloy bars
Research Status of Advanced Copper Alloy Bar - CuCrZr Alloy
The estimation expressions of ultimate strength and maximum conductivity of Cu-XCrCr-YZrZr alloy after 450°C aging treatment were determined, and the existence form and interaction mechanism of alloying elements were clarified.
The addition of Zr can improve the stability of the alloy at room temperature and high temperature.
Zr元素的添加能抑制Cr相的长大，且以fcc Cu5Zr相和CuCrZr相存在。
The addition of Zr can inhibit the recrystallization behavior of alloys.
In addition to precipitation in the precipitated phase, the Zr element is also enriched around the Cr phase to inhibit the growth of the Cr phase.
Alloying elements such as Ag, Sn, and Mg have less influence on the comprehensive properties of alloys than Zr elements.
It also lists representative companies.
Research status of advanced copper alloy bars - alumina copper
The hardness of diffuse copper increases with the increase of aluminum content, and the conductivity decreases with the increase of aluminum content. The annealing temperature had no obvious effect on the conductivity. The hardness of diffuse copper decreases slowly with the increase of annealing temperature, and it has good anti-high temperature softening characteristics compared with oxygen-free copper.
平均晶粒度约为1.2μm；纳米氧化铝弥散分布；氧化铝为γ- Al2O3。
Dispersed copper grains are fine; Alumina is diffusely distributed in the matrix; The size of the alumina particles is not uniform.
The XRD results of the diffuse phase in the alloy prepared by reaction synthesis showed that the diffuse phase was a single face-centered cubic γ-Al2O3. The polycrystalline diffraction rings of pγ-Al2O3 correspond to the (220), (311), (400) and (440) crystal planes of γ-Al2O3, respectively.
The hardness value of the alloy decreases slowly with the increase of annealing temperature, and the decrease is not large. After high-temperature annealing, the yield ratio of the alloy is as high as 89%, which reflects the excellent high-temperature softening resistance of the alloy. High-temperature performance decreases as temperature rises.
He introduced representative companies.
3. Future development and response
It introduces the characteristics of the economic operation of the automobile industry.
It also introduced the all-aluminum body, steel-aluminum hybrid body and the case of related car companies.
Aluminum alloy welding features
The spot welding electrode of aluminum plate is very seriously burned under the action of high temperature and high pressure.
The surface of the aluminum plate is easy to oxidize, and the melting point of the alumina film is extremely high (2054°C), which aggravates the adhesion between the electrode cap and the aluminum plate.
The electrode cap will stick to the aluminum plate, and the electrode cap will need to be resharpened.
The very high frequency of grinding, the consumption of a large number of electrode caps and the sacrifice of production cycle time have become the pain points that need to be solved urgently in the aluminum spot welding process.
Determine the appropriate copper alloy system, and the new copper alloy materials can include but are not limited to: high-strength and high-conductivity Al203 dispersion-strengthened copper, CuCrZr and CuZr alloys, etc.; The high-life electrode cap suitable for spot welding of aluminum plate was developed and prepared, and the life was increased by 40~60%.
Material design ideas to improve the overall conductivity of ODS dispersion strengthened copper alloys.
Inhibits the growth of Cr phase, thereby improving the strength and softening resistance of the alloy.
》2024SMM 19th Copper Conference & Copper Industry Expo Special Report