Welding joint preparation for thin plates (< 5 mm): For arc welding of plates with thickness less than 5 mm, what edge preparation is generally recommended to obtain sound joints efficiently?

Introduction / Context:
Proper edge preparation balances penetration, productivity, and distortion control. Thin plates are sensitive to heat input; excessive groove opening increases weld metal volume and warpage without benefits.

Given Data / Assumptions:

• Plate thickness < 5 mm.
• Conventional processes like GMAW or GTAW with suitable root gaps.
• Joint fit-up is acceptable, and backing techniques may be used if needed.

Concept / Approach:
For thin plates, a square-butt joint without bevelling is sufficient because the arc can achieve full penetration across the small thickness. Adding bevels would increase deposited weld metal, heat input, and distortion. A small root gap and appropriate parameters (current, travel speed) help secure fusion at the root without grooves.

Step-by-Step Solution:
Recognise that thickness is small; penetration is attainable without groove.Adopt a square butt with controlled root gap and heat input.Avoid unnecessary bevelling that adds weld volume.Answer: do not require bevelling.

Verification / Alternative check:
Procedure qualification records for thin sheet show successful square-butt welds with proper backing or pulse control, confirming no groove is needed.

Why Other Options Are Wrong:
Single- or double-V/U grooves are intended for thicker sections, not thin sheet.

Backing strips are optional and not mandatory in all cases for < 5 mm.

Common Pitfalls:
Over-prepping edges leading to distortion; neglecting root gap control which can cause lack of fusion or burn-through.

Final Answer:
do not require bevelling