What technique is used to improve the fusion of the weld on thicker materials?

Increasing heat input or using a multi-pass technique is essential for welding thicker materials because it ensures penetration and fusion of the base metal. When working with thicker sections, a single pass may not produce adequate heat to melt the filler metal and the base material sufficiently, which can lead to weak weld joints and inadequate fusion.

By increasing the heat input, welders can achieve better penetration into the material, creating a stronger bond. This can be done by adjusting factors such as amperage, voltage, or the size of the welding torch. Alternatively, using a multi-pass technique involves making several passes over the same joint, which allows the heat to build up and properly fuse the layers, ensuring a strong and durable weld.

In contrast, using a larger welding rod may not necessarily improve the fusion on its own, as it primarily increases the amount of filler material used rather than addressing the heat and penetration concerns. Decreasing the welding speed can lead to overheating or distortion rather than improved fusion, and switching from MIG to TIG welding does not inherently solve the fusion problem on thicker materials, as both methods can be effective depending on the settings used. Thus, the multi-pass technique and increased heat input are the most effective strategies for achieving good fusion in thicker welds.