Welding practice — butt joint type most commonly used in fabrication Among the following butt weld preparations used in steel fabrication, which one is most commonly used in practice for general plate thicknesses?

Introduction / Context:
Butt joints are widely used to join plates and rolled sections in bridges, buildings, tanks, and pipelines. The edge preparation affects accessibility, weld metal volume, distortion control, and economy. Selecting a common, versatile joint preparation ensures practicality for shop and site welding with standard equipment.

Given Data / Assumptions:

• General structural fabrication context (mild or low-alloy steels).
• Range of moderate plate thicknesses where both cost and ease of execution matter.
• Common manual or semi-automatic welding processes (SMAW, GMAW, FCAW).

Concept / Approach:
The single V-butt joint is the most commonly used butt joint preparation. It provides a straightforward groove accessible from one side, requires moderate beveling, and balances penetration with reasonable weld metal volume. For thicker plates, double V can be preferable to reduce total weld metal and balance shrinkage, but in everyday fabrication, single V prevails for simplicity and productivity.

Step-by-Step Solution:

Verification / Alternative check:
Standard welding handbooks and codes (e.g., AWS D1.1) show single V as a default detail for a wide range of thicknesses, with prequalified groove angles and root openings for typical processes.

Why Other Options Are Wrong:

• Double V-butt: common for thick sections but not the most common overall due to two-sided access and increased prep.
• Double U-butt: efficient for very thick plates but requires specialized machining and higher prep cost.
• Single inverted V: uncommon; gravity and access issues make it less practical as a standard choice.
• Square butt with no prep: limited to thin plates where full penetration is achievable; not a general solution.

Common Pitfalls:
Assuming the most economical for very thick plate (double V or U) is the most common in all situations; conflating “possible” with “prevalent.”

Final Answer:
Single V-butt joint