What is a requirement for a filler rod in the welding process?

In the welding process, a filler rod serves to supply additional material to the weld joint. It is crucial that the filler rod has a melting temperature that is lower than or comparable to that of the base materials being joined. This ensures that the filler rod can effectively melt and flow into the joint while the base materials are being heated.

Using a filler rod that melts at a higher temperature than the base materials can lead to difficulties in the welding process. The base materials will not be able to adequately melt and integrate with the filler rod, which can result in weak joints and a poor weld quality. Therefore, it is imperative for the filler rod to have a melting point that is conducive to the welding conditions and compatible with the base materials, enhancing both the bonding and overall structural integrity of the weld.

In contrast, the other options describe characteristics that may not be suitable for a functional filler rod. For instance, using a filler rod made of the same material as the base parts might not be necessary in all situations, especially when specific grade compatibility is required. Additionally, filler rods can include alloying elements to improve mechanical properties. Lastly, requiring the filler rod to be completely solid during application is not feasible since it must melt to fulfill its purpose in the welding