1. Weld symbol assistant (paste a screenshot · tap to interpret)
Take the weld symbol on the drawing — take a screenshot and press Ctrl+V to paste it here (shown locally for reference only — never uploaded or analysed), then follow the steps below, then tap the elements below with the screenshot to hand (one tap gives the reading); the page then assembles the full reading, size conversion and inspection points. Sources: GB/T 324-2008 / ISO 2553; process numbers GB/T 5185.
Click this area and press Ctrl+V to paste a symbol screenshot (or use the button to pick a file)
Screenshots are displayed locally for reference only; the reading is generated from the options you tap below.
⚡ Tap to interpret (tap a weld type for an instant reading; multiple selections allowed) Tap the weld type for a full reading instantly (multiple allowed — for a double-sided weld tap both). Other options may be left blank; they default to arrow side, continuous full length, no supplementary requirement.
Spot weld ≠ full weld: a spot weld is a circle straddling the reference line or leader (◉); a continuous full-length weld needs no special symbol — a weld symbol with no length on the right already means full length; the small circle ○ at a bend in the leader means "weld all around", not a spot weld.
2. Anatomy of a weld symbol
Arrow line (points to the joint)＋
Reference line (AWS: one solid line; GB: solid plus dashed)＋
Basic symbol (weld type)＋
Size symbols (a, z, b, p…)＋
Supplementary symbols (all around, field weld…)＋
Tail (process number)
Arrow side vs other side (AWS A2.4 — export drawings are read this way): AWS uses a single reference line:The weld symbol sits on the reference line Below = weld on the arrow side (the side the arrow points to); drawn on the reference line Above = weld on the other side; symbols on both sides = welded from both sides.
⚠️ This is the opposite of GB/T 324 / ISO 2553 — do not mix them up: GB/ISO use a double reference line (solid + dashed) — the arrow-side symbol goes on the Solid line side; the other side goes on the Dashed line side, and the dashed line may sit above or below the solid line. When the dashed line is below: under GB the symbol below the line = other side, whereas under AWS the symbol below the reference line = arrow side —the reading is exactly reversed. Never apply GB habits to an AWS drawing, or AWS habits to a GB drawing — establish the standard system first, then read the symbol.
3. Basic symbols (common)
| Symbol | Weld name | Plate thickness / notes |
|---|---|---|
| ∥ | Square groove (flanged edge) | Sheet ≤ 6 mm, square butt |
| V | V-groove | Medium plate 3–26 mm — most common |
| Ⅴ (single sided) | Single-bevel groove | Only one side is accessible |
| Y | V-groove with root face | Medium plate, prevents burn-through |
| X | Double-V (X) groove | Thick plate > 20 mm; welding both sides cuts fill volume |
| U | U-groove | Thick plate: less fill metal, more preparation cost |
| △ | Fillet weld | T-joints, lap joints and corner joints — the most widely used |
| ∟ | Single-sided fillet | Corner joint welded from one side only |
| □ | Plug / slot weld | Drilled through a lap joint |
| O | Spot weld | Sheet lap joint, resistance welding |
| ◎ | Seam welding (roller) | Leak-tight lap seam |
4. Supplementary symbols
| Symbol | Meaning | Note |
|---|---|---|
| ○ | Weld all around | Weld all around the part |
| ⌐ (flag) | Field weld | Site welding, not in the shop |
| Three sides | Weld on three sides | The opening points away from the welded side |
| ⌄ (concave) | Concave weld | Concave weld face |
| ⌒ (convex) | Convex weld | Convex weld face |
| — (flat) | Flush weld | Ground flush after welding |
| ⌐ kinked line (tail) | Tail | write the process number (ISO numbers such as 111, 135; AWS writes SMAW, GMAW and so on) |
5. Weld size callouts
| Symbol | Meaning | Note |
|---|---|---|
| z | Fillet leg size | leg length of the right triangle; GB/ISO prefix it with z; AWS omits the z prefix and puts the leg size straight to the left of the symbol |
| a | Fillet throat (effective thickness) | a ≈ 0.7z; ISO drawings usually call out a |
| b | Root gap | Root gap |
| p | Root face height | Square edge left to prevent burn-through |
| α | Groove angle | e.g. 60° |
| n×l(e) | Number of lengths × length (pitch) | Intermittent weld callout, e.g. 4×30(50) |
| K | Fillet leg (thick parts) | Unequal legs are called out separately |
Fillet strength comparison: For the same leg z=6, convex and concave fillets carry different throat sections; a drawing marked a4.2 is ≈ z6 — on ISO drawings multiply a by 1.4 to get z before choosing the electrode.
Reading sizes the AWS way: For fillets the leg is a plain number (e.g. "5/16" or "6", inch or mm per the title block) with no z/a prefix; groove welds carry root gap and groove angle placed by AWS A2.4 rules (sizes left or right of the symbol). Read the symbol first, then the number.
6. Welding process numbers (GB/T 5185 / ISO 4063, common)
| Code | Process | Code | Process |
|---|---|---|---|
| 101 | Metal arc welding (including manual) | 111 | Manual metal arc (MMA / stick) |
| 131 | MIG welding (inert gas) | 135 | MAG welding (active gas, common on steel) |
| 136 | Flux-cored active gas welding | 141 | TIG welding (stainless steel, aluminium) |
| 15 | Plasma arc welding | 21 | Spot welding (resistance) |
| 22 | Seam weld | 311 | Oxy-acetylene welding |
Tail on an AWS drawing: AWS A2.4 normally skips the numeric process numbers above and writes the abbreviation in the tail:SMAW (MMA / stick, ≈111), GMAW (GMAW MIG/MAG, ≈131/135), FCAW (flux-cored, ≈136), GTAW (TIG, ≈141), SAW (submerged arc). On an AWS drawing identify the process from the abbreviation first, then check it against the numeric process table.
7. Reading examples
- AWS: "△ 5/16" below the reference line: Arrow-side fillet, leg 5/16 (units per drawing, usually inch).
- AWS: the same "△ 5/16" above the reference line: fillet on the other side — the vertical position of the symbol decides arrow side vs other side, unlike the GB solid/dashed rule.
- GB: "z5 △" placed on the solid-line side: Arrow-side fillet, leg 5 mm; if placed on the dashed side it means the other side (GB double-line system, the reverse of AWS).
- "5×30(50) z6" means: Intermittent fillet weld: 5 lengths of 30 mm, 50 mm pitch, leg 6 mm.
- "V b2 α60° p2" with tail 135 means: Arrow-side V-groove butt weld: root gap 2 mm, groove angle 60°, root face 2 mm, MAG process.
- ○ containing "z4 △" plus a flag: All-around weld on site, leg 4 mm, one pass around the joint.
- Fillet both sides: One △ above and one below the reference line; the z values may differ (z5 above, z4 below).
For QA: Check the fillet leg with a weld gauge; judge convexity/concavity and undercut depth against GB/T 29712 or the applicable weld quality level.