Which welding process mandates a minimum thickness of 3/16" for backing when using ER70S-X filler metal?

The correct response identifies the Shielded Metal Arc Welding (SMAW) process as having a specified requirement regarding backing thickness when using ER70S-X filler metal. In the context of this standard, SMAW is often utilized for welding thicker materials, which necessitates a backing bar or plate to support the weld pool and prevent defects like burn-through or inadequate fusion. The minimum thickness of 3/16" ensures that the backing can effectively withstand the thermal conditions and forces imparted during the welding operation, thus contributing to the overall integrity of the weld.

The other welding processes, such as Flux-Cored Arc Welding (FCAW), Gas Metal Arc Welding (GMAW), and Submerged Arc Welding (SAW), have different requirements regarding backing, which may allow for thinner backing materials or no backing at all in certain applications. These variations stem from differences in heat input, welding techniques, and the types of joints being welded, resulting in distinct considerations for each welding process.