Oxygen-free copper is widely used in various fields due to its excellent properties. However, casting defects can significantly affect its performance. This article focuses on the impact of casting defects on the properties of upward continuous oxygen-free copper rods. Through experimental research and finite element simulation, the effects of and defects on the mechanical, physical, and chemical properties of copper rods are analyzed. The results provide valuable references for improving the quality of oxygen-free copper products.
1. Introduction
1.1 Background and Significance
Copper has played a crucial role in human civilization. Oxygen-free copper, with its high purity and excellent properties, is widely used in power, communication, and superconducting technology. However, casting defects can reduce its quality and performance. Therefore, studying the influence of casting defects on the properties of oxygen-free copper rods is of great significance for improving product quality and meeting the needs of various industries.
1.2 Upward Continuous Casting Process of Oxygen-free Copper
The upward continuous casting process is an advanced production method for oxygen-free copper. It includes raw material selection, melting, and casting. The key to this process is to control the temperature, traction speed, and quality of the crystallizer to ensure the quality of the copper rod.
1.3 Research Status of Oxygen-free Copper Casting Properties
In recent years, there have been many studies on the properties of oxygen-free copper castings, including conductivity, thermal conductivity, mechanical properties, and corrosion resistance. These studies have provided a theoretical basis for the application and development of oxygen-free copper.
1.4 Research Status of the Influence of Casting Defects on Casting Properties
Casting defects have a significant impact on the performance of castings. 国内外学者 have conducted extensive research on this issue and have proposed various methods to control and reduce casting defects. However, there is still a lack of in-depth research on the specific influence of casting defects on the properties of oxygen-free copper rods.
1.5 Quantitative Fracture Analysis Technology
Quantitative fracture analysis technology is an important method for studying the fracture mechanism of materials. It can provide detailed information about the fracture surface and help analyze the influence of casting defects on the mechanical properties of materials.
1.6 Main Contents of This Study
This study mainly focuses on the following aspects:
- Analyze the mechanical and physical and chemical properties of oxygen-free copper rods produced by different raw materials.
- Study the influence of casting defects on the mechanical properties of copper rods.
- Explore the influence of 气孔 defects on the macroscopic mechanical properties of oxygen-free copper through finite element simulation.
1.7 Technical Route
The technical route of this study is as follows:
- Prepare samples of oxygen-free copper rods with different raw materials.
- Conduct mechanical property tests, including tensile tests, hardness tests, and conductivity tests.
- Analyze the fracture morphology and composition of the samples.
- Conduct electrochemical corrosion tests to study the corrosion resistance of the samples.
- Establish a finite element model to simulate the influence of 气孔 defects on the mechanical properties of copper rods.
2. Experimental Materials and Methods
2.1 Experimental Materials and Equipment
- Experimental materials: The samples used in this experiment are oxygen-free copper rods produced by upward continuous casting, including TUY03 silver oxygen-free copper rods (benchmark) and recycled copper rods.
- Experimental equipment: The main experimental equipment includes a vertical sawing machine, a metallographic microscope, a polishing machine, a universal tensile testing machine, a digital eddy current metal conductivity meter, a field emission scanning electron microscope, a Vickers hardness tester, an electrochemical workstation, and an electronic balance.
2.2 Experimental Sample Preparation
The samples were cut from the oxygen-free copper rods collected from the production line and processed into different shapes and sizes for different tests.
2.3 Characterization and Analysis Methods
- Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS): These techniques were used to analyze the fracture morphology and composition of the samples.
- Room temperature tensile testing: The tensile properties of the samples were tested according to the national standard.
- Microhardness testing: The hardness of the samples was measured using a Vickers hardness tester.
- Conductivity testing: The conductivity of the samples was measured using a digital eddy current metal conductivity meter.
- Electrochemical testing: The corrosion resistance of the samples was evaluated by electrochemical tests, including potentiodynamic polarization tests and electrochemical impedance spectroscopy tests.
3. Influence of Casting Defects on the Properties of Oxygen-free Copper Rods
3.1 Influence of Casting Defects on the Mechanical Properties of Oxygen-free Copper Rods
- Influence of 夹杂 defects on the mechanical properties of copper rods
- Mechanical property statistics: The tensile strength, yield strength, elongation, and reduction of area of the benchmark and recycled copper rods were measured and compared. The results showed that the benchmark samples had better mechanical properties than the recycled copper rods.
- Fracture macroscopic analysis: The fracture morphology of the samples was observed, and it was found that both the benchmark and recycled copper rods exhibited ductile fracture characteristics. However, the benchmark samples had a more uneven fracture surface and fewer holes, indicating better fracture toughness.
- Fracture microscopic analysis: The microstructure of the fracture surface was analyzed by SEM and EDS. It was found that the inclusions in the samples were mainly composed of C, O, Al, and Si. The size and distribution of the inclusions had a certain impact on the mechanical properties of the copper rods.
- Influence of 孔洞 defects on the mechanical properties of copper rods
- Weibull distribution statistics of tensile properties: The tensile strength and elongation of the samples were analyzed by Weibull distribution. The results showed that the Weibull modulus of the benchmark samples was higher than that of the recycled copper rods, indicating that the mechanical properties of the benchmark samples were more stable.
- Relationship between cross-sectional porosity and tensile properties and prediction: The relationship between the cross-sectional porosity and the elongation of the samples was studied by fitting a power function model. The results showed that the elongation of the samples decreased with the increase of the cross-sectional porosity. When the porosity was close to 0, the maximum elongation of the benchmark and recycled copper rods was predicted to be 45.86% and 41%, respectively.
3.2 Hardness of the Two Groups of Oxygen-free Copper Rod Castings
The hardness of the benchmark and recycled copper rods was measured. The results showed that the hardness of the benchmark samples was higher than that of the recycled copper rods, indicating that the holes had a significant impact on the hardness of the copper rods.
3.3 Conductivity of the Two Groups of Oxygen-free Copper Rod Castings
The conductivity of the benchmark and recycled copper rods was measured. The results showed that the conductivity of the two groups of samples was similar, indicating that the holes had little impact on the conductivity of the copper rods.
3.4 Electrochemical Corrosion Behavior of the Two Groups of Oxygen-free Copper Rods
- Polarization curve analysis: The potentiodynamic polarization curves of the benchmark and recycled copper rods were measured. The results showed that the corrosion current density of the benchmark samples was lower than that of the recycled copper rods, and the corrosion potential was more positive, indicating that the benchmark samples had better corrosion resistance.
- EIS impedance spectroscopy analysis: The electrochemical impedance spectroscopy of the benchmark and recycled copper rods was measured. The results showed that the charge transfer resistance of the benchmark samples was higher than that of the recycled copper rods, indicating that the benchmark samples had better corrosion resistance.
- Corrosion mechanism: The corrosion mechanism of the oxygen-free copper rods in the sodium chloride solution was analyzed. It was found that the main corrosion process was the dissolution of copper to form a sodium chloride complex.
4. Finite Element Simulation of the Influence of Pore Defects on the Mechanical Properties of Oxygen-free Copper
4.1 Establishment and Verification of the Numerical Simulation Model
- Establishment of a model with randomly distributed pore defects: A three-dimensional solid structure model of oxygen-free silver copper with randomly distributed pore defects was established using COMSOL software.
- Acquisition of material constitutive model and parameters: The material parameters of oxygen-free silver copper were obtained by tensile tests, and a porous elastoplastic constitutive model was established.
- Mesh division: The model was simplified to a two-dimensional axisymmetric model for mesh division to improve the calculation efficiency and accuracy.
- Boundary conditions: Displacement boundary conditions were applied to the model to simulate the tensile process of the specimen.
- Model verification: The simulation results were compared with the experimental results to verify the correctness of the model.
4.2 Influence of Pore Defects on the Mechanical Properties of Materials
- Influence analysis of pore defect size: The influence of pore defect size on the tensile mechanical properties of oxygen-free silver copper was analyzed by designing different models with different pore diameters and porosities. The results showed that when the porosity was not more than 3% and the defect diameter was not more than 80 μm, the defect diameter had little impact on the mechanical properties of the copper.
- Influence analysis of structural porosity size: The influence of structural porosity size on the tensile mechanical properties of oxygen-free silver copper was analyzed by designing different models with different porosities and constant pore diameters. The results showed that with the increase of porosity, the hardening ability of the material in the plastic hardening stage decreased, and the tensile strength also decreased.
5. Conclusions and Prospects
5.1 Conclusions
- The mechanical properties of the benchmark samples were better than those of the recycled copper rods. The benchmark samples had higher tensile strength, yield strength, elongation, and reduction of area, and lower cross-sectional porosity.
- The fracture toughness and plasticity of the benchmark samples were better than those of the recycled copper rods. The benchmark samples had a more uneven fracture surface and fewer holes.
- The Weibull modulus of the benchmark samples was higher than that of the recycled copper rods, indicating that the mechanical properties of the benchmark samples were more stable.
- The hardness of the benchmark samples was higher than that of the recycled copper rods, indicating that the holes had a significant impact on the hardness of the copper rods.
- The conductivity of the two groups of samples was similar, indicating that the holes had little impact on the conductivity of the copper rods.
- The corrosion resistance of the benchmark samples was better than that of the recycled copper rods. The benchmark samples had a lower corrosion current density and a more positive corrosion potential.
- When the porosity was not more than 3% and the defect diameter was not more than 80 μm, the defect diameter had little impact on the mechanical properties of the copper. With the increase of porosity, the hardening ability of the material in the plastic hardening stage decreased, and the tensile strength also decreased.
5.2 Prospects
- Future research can focus on finding more suitable non-destructive testing methods to characterize the three-dimensional characteristics of internal holes in oxygen-free copper, which will provide more guidance for actual production.
- To obtain the optimal raw material ratio for upward continuous casting of oxygen-free copper rods, more groups of experiments with different raw material ratios should be set up for analysis.
- To more accurately compare the performance of the two groups of samples, the number of experimental samples should be increased in future research.
- In future research, the mechanism of the influence of inclusions on the mechanical properties of materials can be further explained by statistically analyzing the number and distribution of inclusions.
