The best shielding gas for copper MIG welding is typically a mixture of argon and helium. This combination is preferred due to its ability to provide excellent arc stability and penetration, which are crucial for welding copper. Argon, being an inert gas, helps in stabilizing the arc and reducing spatter, while helium increases the heat input, which is necessary for the high thermal conductivity of copper. A common mixture used is 75% helium and 25% argon. This ratio ensures that there is sufficient heat to achieve proper fusion and penetration, while the argon component helps maintain a stable arc and good weld pool control. In some cases, especially for thicker copper materials, a higher percentage of helium, such as 90% helium and 10% argon, may be used to provide even more heat. Using pure argon is generally not recommended for copper MIG welding because it may not provide enough heat for adequate penetration, especially on thicker sections. Conversely, using pure helium can make the arc too hot and difficult to control, leading to excessive spatter and potential burn-through. In summary, the argon-helium mixture is optimal for copper MIG welding due to its balance of arc stability and heat input, which are essential for overcoming the challenges posed by copper's high thermal conductivity and achieving high-quality welds.

For copper MIG welding, the recommended settings depend on the thickness of the copper, the type of copper alloy, and the specific welding machine being used. However, general guidelines can be provided: 1. **Material Preparation**: Ensure the copper surfaces are clean and free from oxides, oils, and contaminants. Use a stainless steel brush or chemical cleaner. 2. **Shielding Gas**: Use a mixture of Argon and Helium. A common ratio is 75% Argon and 25% Helium, but this can vary based on the specific application and desired penetration. 3. **Wire Type**: Use a deoxidized copper wire, such as ERCu or ERCuSi-A, which helps prevent porosity and ensures better weld quality. 4. **Wire Diameter**: Choose a wire diameter appropriate for the thickness of the copper. Common diameters range from 0.8 mm to 1.2 mm (0.030 to 0.045 inches). 5. **Voltage and Amperage**: Set the voltage and amperage according to the wire diameter and material thickness. For thinner materials, lower settings are used, while thicker materials require higher settings. For example, a 1.0 mm wire might require 18-22 volts and 100-150 amps. 6. **Travel Speed**: Maintain a consistent travel speed to ensure even heat distribution and prevent burn-through. Adjust speed based on the thickness of the material. 7. **Polarity**: Use Direct Current Electrode Positive (DCEP) for better penetration and arc stability. 8. **Preheating**: Preheat thicker copper sections to 50-200°C (122-392°F) to reduce thermal conductivity and improve weld quality. 9. **Technique**: Use a push technique to improve gas coverage and reduce oxidation. Adjust these settings based on trial welds and specific equipment capabilities to achieve optimal results.

Yes, you can weld copper to steel using MIG welding, but it is challenging due to the differences in their melting points and thermal conductivities. Copper has a higher thermal conductivity and a lower melting point compared to steel, which can lead to issues like uneven heating and poor fusion. To successfully weld these two metals, you need to use a filler material that is compatible with both copper and steel, such as a silicon bronze wire. The process involves using a MIG welder with a spool gun to feed the silicon bronze wire. The welder settings should be adjusted to accommodate the properties of the filler material and the base metals. Typically, a lower voltage and wire feed speed are used to prevent overheating the copper. Preheating the steel can also help in achieving a better bond by reducing the thermal gradient between the two metals. Shielding gas is crucial in this process to prevent oxidation and contamination. A mixture of argon and helium is often recommended to provide adequate coverage and heat input. The welding technique should focus on minimizing heat input to the copper while ensuring sufficient penetration into the steel. Despite these precautions, the joint may not be as strong as those achieved with similar metals, and the weld may be more prone to cracking and other defects. Therefore, this method is generally used for applications where the joint does not bear significant structural loads. Proper post-weld treatments, such as stress relieving, can further enhance the weld quality.

For welding copper using the MIG (Metal Inert Gas) process, the best type of wire to use is a silicon bronze wire, often designated as ERCuSi-A. Silicon bronze wire is preferred because it offers excellent corrosion resistance, good mechanical properties, and a lower melting point than pure copper, which helps in reducing distortion and warping during the welding process. This wire is specifically designed for welding copper, copper-silicon, and copper-zinc base metals, making it versatile for various copper alloys. Silicon bronze wire contains a small percentage of silicon, which enhances fluidity and wetting action, leading to smoother welds with less spatter. It also provides a good color match for copper, which is important for aesthetic applications. The wire is typically used with a shielding gas mixture of 100% argon or a combination of argon and helium to ensure proper arc stability and penetration. When using silicon bronze wire, it is crucial to maintain proper heat control, as copper has high thermal conductivity, which can lead to overheating and burn-through if not managed correctly. Preheating the copper workpiece can also be beneficial to ensure better fusion and reduce the risk of cracking. Overall, silicon bronze wire is the optimal choice for MIG welding copper due to its compatibility with copper alloys, ease of use, and ability to produce high-quality welds with minimal defects.

To prevent porosity when MIG welding copper, follow these steps: 1. **Material Preparation**: Ensure the copper surface is clean and free from contaminants such as oil, grease, and oxides. Use a wire brush or chemical cleaner to remove any impurities. 2. **Preheating**: Preheat the copper to a temperature between 400°F and 750°F (204°C to 399°C) to reduce thermal shock and improve weld quality. This helps in reducing porosity by allowing gases to escape more easily. 3. **Shielding Gas**: Use an appropriate shielding gas mixture, typically 100% argon or a mix of argon with a small percentage of helium. This provides a stable arc and minimizes atmospheric contamination. 4. **Filler Material**: Select a compatible filler material, such as a deoxidized copper alloy, to ensure good fusion and reduce the risk of porosity. 5. **Welding Parameters**: Adjust the welding parameters, including voltage, current, and travel speed, to suit the thickness of the copper. Use a higher heat input to ensure proper fusion and gas escape. 6. **Technique**: Employ a consistent welding technique with a steady hand to maintain a stable arc. Avoid excessive weaving, which can trap gases and lead to porosity. 7. **Post-Weld Treatment**: Allow the weld to cool slowly to prevent cracking and further porosity. Use controlled cooling methods if necessary. 8. **Inspection**: Conduct thorough inspection using non-destructive testing methods to ensure the weld is free from porosity and other defects. By following these steps, you can minimize the risk of porosity and achieve high-quality welds on copper materials.