Which material would typically require using a different filler material than mild steel?

The choice of filler material in welding is crucial for ensuring a strong, reliable weld that matches the properties of the base materials. Mild steel, which is commonly used due to its versatility and weldability, typically requires a specific type of filler material that complements its mechanical properties.

When welding aluminum, a different filler material is needed because aluminum has unique characteristics, including a lower melting point and different thermal conductivity compared to mild steel. Additionally, aluminum can be sensitive to contamination from other metals, which might weaken the weld if inappropriate filler is used. Therefore, welders would use aluminum-based fillers, such as 4047 or 5356, specifically designed for this metal.

Similarly, cast iron also requires special handling and filler materials distinct from those used for mild steel. Cast iron is more brittle and has a higher carbon content, which means that not using a compatible filler can lead to cracking or other defects in the weld. For joining cast iron, fillers such as nickel-based alloys or specific cast iron rods are often used to ensure compatibility and structural integrity.

Thus, both aluminum and cast iron necessitate different filler materials compared to mild steel, making the choice involving both these materials accurate. This understanding is essential for welders to create durable and appropriate joins in various