Choosing the Right Welding Process for Casting to Mild Steel

When welding a cast item to mild steel, the choice of welding process and filler material is crucial due to the differences in material properties. This article discusses the recommended approaches for achieving a successful and durable weld.

Welding Process

There are several welding processes available, each with its own advantages and suitable for different applications. Here are the recommended processes:

Gas Metal Arc Welding (GMAW) or MIG Welding: Ideal for thin sections, offering good control and efficiency. Shielded Metal Arc Welding (SMAW) or Stick Welding: Versatile, suitable for thicker sections, and adaptable to various conditions. Tungsten Inert Gas Welding (TIG or GTAW): Suitable for precise work, producing high-quality welds, but may be slower and more challenging for thicker materials.

Filler Material

The choice of filler material is critical to ensure a strong and compatible weld between the cast and mild steel. Here are the recommended filler materials:

For Cast Iron to Mild Steel: Use a nickel-based filler rod, e.g., ERNiFe-C1, to enhance compatibility and reduce the risk of cracking. For Cast Aluminum to Mild Steel: Use aluminum filler rods, e.g., ER4047 or ER4045, specifically designed for aluminum. For Dissimilar Metals: Ensure the filler material is compatible with both metals to prevent complications during the welding process.

Pre-Weld Preparation

Proper preparation is essential for a successful weld. Follow these steps to prepare the surfaces:

Clean the surfaces to remove any contaminants, such as oil, rust, or paint. If necessary, preheat the cast item, especially for thicker sections, to reduce thermal stress and minimize cracking.

Post-Weld Treatment

Avoiding residual stresses and improving the overall integrity of the joint is crucial. Consider the following treatments:

Stress Relieving or Annealing: Relieve residual stresses and enhance the joint's integrity. This step is particularly important for thicker sections.

Conclusion

The best choice of welding process and filler material depends on the specific types of cast material and mild steel being welded. Always refer to material specifications and consult welding guidelines specific to the materials in use for optimal results.

Note: For precision and quality, especially with cast products, TIG welding is often recommended due to its advantages. However, using dissimilar metals electrodes with an arc welder can also be effective, provided the cast piece is maintained at a high temperature, as discussed below.

Alternatively, for cast iron work, it is best to have the cast piece hot beforehand and direct the majority of the heat where needed. Additionally, using a magnesian bronze rod flux coated with an oxy/acetylene gas torch can be an effective method. Lower temperatures may be required and the cast piece should remain hot or warm throughout the process.

For an expert level of welding, consider consulting with a welder-tradesman who has experience with these processes.