Root gap can affect distortion even with a similar groove volume

Research on single-pass GMAW joints shows that fit-up geometry can change flatness deviation even when groove area and electrical parameters remain similar.

Electrical parameters are not the only boundary conditions

Discussions of welding distortion often focus on current, voltage, travel speed and sequence. The actual geometry of the prepared and fitted joint can be equally important. Root gap, groove angle and root face change the position of deposited metal and the heat distribution relative to the neutral axis of the component.

A study of GMAW joints in 1.4301 steel compared several geometries while limiting groove cross-sectional-area variation to about 2.3%. Under the investigated conditions, root gap had the strongest relationship with the distribution of flatness deviation. The maximum difference between geometric means reached 23%, but variability was high and the authors noted that three repetitions were insufficient for full process estimation.

Practical production relevance

Applying the same welding program to two assemblies does not guarantee the same thermal and distortion cycle. Actual root gap and misalignment should therefore be considered input process variables, not merely visual-inspection outcomes.

The result is not a reason to change a WPS root gap arbitrarily. It supports tighter control of edge preparation, fixturing and fit-up tolerances.

Boundary of applicability

The findings concern thin, single-pass austenitic-steel joints in one experimental setup. They do not establish a universal ranking of variables for multi-pass joints or carbon steels.

Source

• Grzesiak, D.; Nadolny, K.: Effect of welding groove geometry variation on flatness deviation in GMAW joints, *Welding in the World*, 28 August 2026.

This is an original summary and practical interpretation. No figures or tables have been reproduced.