Weld Symbol Chart — All AWS A2.4 Weld Symbols
A complete weld symbol chart per AWS A2.4:2020. All 16 weld type symbols — fillet, groove (V, bevel, J, U, square, flare-V, flare-bevel), plug, slot, spot, seam, stud, surfacing, back/backing, and edge — plus supplementary symbols (field weld, weld-all-around, melt-through). Use this chart on structural steel drawings and fabrication blueprints.
Fillet and Groove Weld Symbols
Fillet and groove welds represent the two foundational weld categories in AWS A2.4:2020. Fillet welds join surfaces at an angle without joint preparation. Groove welds fill a prepared groove between abutting members and can be complete joint penetration (CJP) or partial joint penetration (PJP).
| Symbol | Weld Type | Description | Typical Application |
|---|---|---|---|
| △ | Fillet Weld | Right triangle, vertical leg on left. Size = leg length to the left of symbol. | T-joints, lap joints, corner joints — most common weld in structural steel. |
| V | V-Groove Weld | Open-V shape on reference line. Both members beveled to form the groove. | Butt joints in plate and pipe requiring CJP. Most common groove joint. |
| / | Bevel Groove Weld | One vertical line + one angled line. Broken arrow indicates which member is beveled. | T-joints and butt joints where only one member is prepared. |
| J | J-Groove Weld | J-curve shape. One member has a radius + bevel preparation. Requires machining. | Heavy plate CJP where reduced distortion is required. Broken arrow indicates prepared member. |
| U | U-Groove Weld | U-curve on reference line. Both members have radius preparations. | Heavy butt joints where U-groove reduces filler metal and distortion vs. V-groove. |
| □ | Square Groove Weld | Two short perpendicular lines from reference line. Gap = root opening. | Thin material butt joints. Root opening specified to the left. |
| ⋂ | Flare-V Groove Weld | Two curved lines forming a flared-V. Used for curved member surfaces. | Joining two round bars or curved sections face-to-face. No joint preparation needed. |
| ⋃ | Flare-Bevel Groove Weld | One curved line + one straight line. One member is curved (e.g., tube or round bar). | Joining a round member to a flat plate — tube-to-plate T-joints. |
Special Weld Symbols
Special weld types join members through holes, surface contact, or overlapping faces rather than edge-to-edge joints. Each has its own symbol and dimension conventions per AWS A2.4:2020.
| Symbol | Weld Type | Description | Typical Application |
|---|---|---|---|
| □ | Plug Weld | Rectangle on reference line. Diameter specified to left; depth of fill in parentheses. | Joining lapped plates through a pre-drilled hole. Flush surface alternative to through-bolt. |
| ▬ | Slot Weld | Rectangle with width x length specified. Orientation angle above/below symbol. | Elongated hole version of plug weld. Used for shear connection of overlapping plates. |
| ○ | Spot Weld | Circle on reference line (no arrow touches joint). Size = weld diameter or shear strength. | RSW (resistance spot welding) and arc spot welding. Sheet metal and thin plate. |
| ― | Seam Weld | Two horizontal lines through circle. Length and pitch to right for intermittent seams. | Continuous or intermittent weld along overlapping member contact area. |
| △ | Stud Weld | Circle on reference line with perpendicular line. Stud diameter and quantity noted. | Nelson studs for composite deck construction. Drawn arc or capacitor-discharge process. |
| → | Surfacing Weld | Wavy line below reference line. Height dimension = minimum deposit thickness. | Build-up, hardfacing, corrosion-resistant overlay. Not a joint weld — deposits on a surface. |
Supplementary Symbols
Supplementary symbols modify the primary weld symbol or specify additional requirements. They appear on or near the reference line and are combined with any of the weld type symbols above.
| Symbol | Weld Type | Description | Typical Application |
|---|---|---|---|
| ▶ | Field Weld | Solid filled triangle flag at reference line / arrow junction. | Any weld made at the erection site rather than in the fabrication shop. |
| ○ | Weld All Around | Circle at reference line / arrow junction. Not at end of reference line. | Tube-to-plate, pipe sleeve, and any closed-perimeter joint requiring continuous weld. |
| R | Back / Backing Weld | Semicircle on opposite side of reference line from primary groove symbol. | Single-side CJP groove welds requiring backing pass (back weld) or bar (backing weld). |
| ⋯ | Melt-Through Weld | Filled semicircle on opposite side from primary weld symbol. | Single-side welds requiring visible complete penetration on the root side. |
| □ | Edge Weld | Two parallel lines (edge joint representation) on reference line. | Sheet metal edge joints, flanges, and light plate edge connections. |
How to Use This Chart
Use this chart as a quick lookup when reading a structural steel drawing or fabrication blueprint. Find the symbol you see on the drawing in the table above, then follow the link to the deep-dive page for full details on dimensions, placement conventions, and D1.1 requirements.
For a step-by-step method for reading any weld symbol — reference line, arrow side, dimensions, special indicators — see How to Read Weld Symbols.
For the anatomy of a welding symbol as it appears on a blueprint or shop drawing — the four-element system of reference line, arrow, weld symbol, and tail — see Welding Symbols on Drawings.