Comprehensive A2.4 Symbol Reference
The complete AWS A2.4:2020 溶接記号表示 reference for fabricators and inspectors. Covers every 溶接の種類 including groove, fillet, plug, slot, spot, seam, stud, surfacing, バッキング, and edge welds, plus 10 NDE examination methods, 9 supplementary symbols, 136 process designations, 7 finishing designators, and D1.1:2025 cross-references for 構造用鋼.
This reference covers every symbol type defined in AWS A2.4:2020 (8th Edition), with D1.1:2025 条項 cross-references for structural steel applications. Print this page for a complete multi-page desk reference.
Section 1Symbol Anatomy — A2.4 §4.1
Section 2Weld Symbol 種類 — A2.4 Figure 4.1
| Type | Symbol | A2.4 Clause | D1.1 Cross-Reference |
|---|---|---|---|
| Fillet | §8 | Table 7.7 min サイズ, §4.5.2.9 max on edges | |
| Square Groove | §7 | Fig 5.1 事前認定 CJP/PJP joints | |
| V-Groove | §7 | Fig 5.1 B-U2, B-U2a (CJP single-V) | |
| Bevel Groove | §7, §6.3 perp leg | Fig 5.1 TC-U4a (T継手 bevel CJP) | |
| U-Groove | §7 | Fig 5.1 B-U6 (single-U CJP, backgouge) | |
| J-Groove | §7, §6.3 perp leg | Fig 5.1 B-U8 (single-J CJP, backgouge) | |
| Flare-V Groove | §7.2.10 | Table 4.1: 3/4R (GMAW), 5/8R (SMAW/FCAW-S). Process-dependent. | |
| Flare-Bevel Groove | §7.2.10, §6.3 perp leg | Table 4.1: 5/8R (GMAW/FCAW-G), 5/16R (SMAW/FCAW-S). Process-dependent. | |
| Plug | §9 | §4.11 min hole dia, §5.4.4 | |
| Slot | §10 | §4.11 (same rules as plug) | |
| Spot / Projection | §11 | N/A (D1.3 for arc spot on sheet steel) | |
| Seam | §12 | N/A (D1.1 does not cover seam welding) | |
| Stud | §14 (arrow-side only) | Clause 9 (drawn-arc stud welding) | |
| Surfacing | §15 | §7.25 (補修 welding provisions) | |
| Back / Backing | §7.7 | §5.4.1.3 backgouge to sound metal (Fig 5.1 note d) | |
| Edge | §13 | N/A (D1.3 for sheet steel edges) | |
| Scarf (brazing) | §16 | N/A (brazing only, not D1.1) |
Section 3Size Notation Quick Reference — A2.4 §7.2, §8.2
Fillet Weld Notation
6Leg size — 6mm equal-leg fillet both sides when on both sides of reference line6×8Unequal fillet — both sizes appear to the left as S1×S2. Orientation not specified by the symbol; a drawing detail shows which leg goes on which member.6left +50-150rightIntermittent — leg size (6mm) to left of symbol; length–pitch (50mm weld, 150mm c/c) to right.
Groove Weld Notation
D(S)D = groove depth (preparation depth). (S) = 溶接サイズ/有効のど厚 (design dimension)12(10)12mm groove depth, 10mm effective throat — D without parentheses, (S) in parenthesesRRoot opening value — often shown in tail or drawing note, not symbolαGroove angle — shown on the symbol to the left of the weld symbol (e.g. 45°). Per §7.3.
Intermittent Weld Notation
length-pitchWritten right of symbol. Length = each weld run. Pitch = center-to-center spacing50-15050mm long welds, 150mm apart (center). Net gap = 100mmstaggeredIntermittent symbols offset on arrow side vs other side = chain or staggered
Section 4Supplementary Symbols — A2.4 Figure 4.2
Circle at arrow/reference junction. Weld extends around entire joint perimeter. Per §6.11.
Flag at junction. Weld made at erection site, not shop. Per §6.9.
Filled semicircle opposite weld symbol. CJP with visible root reinforcement. Per §6.14.
Square symbol. Placed before ルートパス for CJP groove welds. Per §7.10.
Rectangle. Permanent or removable バッキングバー. R inside = removable. Per §7.8.
Rectangle (same as backing but placed inside groove). Metal spacer between root faces. Per §7.9.
Straight line above weld symbol. Weld face flush with 母材. Per §6.13.
Outward arc. Weld face crowns above base metal surface. Per §6.13.
Inward arc. Weld face dips below base metal surface. Per §6.13.
Section 5NDE Examination Method Symbols — A2.4 表 A6, Clause 17
| Code | Method | Category | Side Significance | D1.1 Reference |
|---|---|---|---|---|
RT | Radiographic Testing | Volumetric | Centered — no side preference (§17.5.5) | Clause 8, Part E |
UT | Ultrasonic Testing | Volumetric | Centered — no side preference | Clause 8, Part F |
MT | Magnetic Particle Testing | Surface | Arrow/other side — surface access matters (§17.5.2) | §8.14.4 (procedure), Part C (合否基準) |
PT | Penetrant Testing | Surface | Arrow/other side — surface access matters | §8.14.5 (procedure), Part C (acceptance) |
VT | Visual Testing | Surface | Arrow/other side — surface access matters | §8.6 (obligations), Part C (acceptance) |
ET | Electromagnetic (Eddy Current) Testing | Surface | Arrow/other side — surface access matters | Per Engineer specification |
AET | Acoustic Emission Testing | Specialized | Varies by application | Per Engineer specification |
LT | Leak Testing | Specialized | Varies by application | Per Engineer specification |
NRT | Neutron 放射線透過 Testing | Volumetric | Centered — no side preference | Per Engineer specification |
PRT | Proof Testing | Specialized | Varies by application | Per Engineer specification |
Surface methods detect what you can almost see. Volumetric methods find what you never will. The symbol tells you which side matters — and for RT and UT, neither side does. — CWI field perspective, based on A2.4 §17.5
Section 6Arrow Side & Other Side Rules — A2.4 §6.2–6.5
Arrow Side vs Other Side
Weld symbols placed below the 基線 specify the arrow side of the joint (the side the arrow points to). Symbols placed above the reference line specify the other side. Per §6.2.
Broken Arrow Rule
When only one joint member is to be prepared (bevel-groove, J-groove, flare-bevel), the arrow shall have one break and point toward that member. The arrow need not be broken if it is apparent which member is to be prepared, and shall not be broken if there is no preference. Per §6.4.1.
Fillet Weld Arrow
For fillet welds, the arrow may or may not be broken to indicate weld locations. There is no requirement to break the arrow for fillet welds as there is for single-bevel or J-groove welds. Per §6.4.2.
Combination Weld Symbols
For joints requiring more than one weld type (e.g., fillet + groove), a symbol shall be used to specify each weld. Per §6.5.
Multiple Arrows
Two or more arrows may be used with a single reference line to point to locations where identical welds are specified. Per §6.6.
Section 7Tail Contents — A2.4 §6.12
Process Designation
SMAWShielded Metal アーク溶接 (stick)FCAW-SSelf-Shielded Flux Cored Arc WeldingGMAWGas Metal Arc Welding (MIG)GTAWGas Tungsten Arc Welding (TIG)GTAW-AUAutomatic GTAW (suffix from Table A5)
References & Special Types
WPS-01Refers to specific 溶接施工要領書 document. Per§6.12.2.TYP"Typical" — avoids repeating identical symbols. User must identify all applicable joints. Per§6.12.3.DET ACross-section or detail reference when basic symbols are inadequate. Per§6.12.4.
Omission Rule
(no tail)When no references are required, the tail may be omitted from the welding symbol entirely. Per§6.12.5.Drawing noteDrawing notes may provide weld information without repeating it in the symbol. Per§6.12.6.
Section 8Multiple Reference Lines — A2.4 §6.7–6.8
Sequence of Operations
Two or more reference lines indicate a sequence of operations. The first operation is specified on the reference line nearest the arrow. Subsequent operations are specified sequentially on additional reference lines. Per §6.7.1.
Supplementary Data
The tail of additional reference lines may be used to specify data supplementary to welding symbol information (e.g., process data, standards references). Per §6.7.2.
Symbols on Each Line
Symbols (including supplementary symbols such as 現場溶接 flags) shall be placed on the reference line for each operation to which they are applicable. Per §6.7.3.
Subreference Lines (Distinct from Multiple Ref Lines)
For joints transitioning from one type to another (e.g., pipe), multiple subreference lines branch from a single reference line. Unlike multiple reference lines, the sequence of welding is undetermined — subreference lines indicate joint type variation, not welding order. Per §6.8.
Section 9Process Letter Designations — A2.4 Table A2
Placed in the tail of the welding symbol per §6.12.1. Application mode suffixes (Table A5) may be appended: -MA Manual, -SA Semiautomatic, -AU Automatic, -ME Mechanized, -RO Robotic, -AD Adaptive Control.
Arc Welding Processes (most common)
| Code | Process | Notes |
|---|---|---|
SMAW | Shielded Metal Arc Welding | Stick/manual. D1.1 prequalified for all positions. |
GMAW | Gas Metal Arc Welding | MIG/MAG. External シールドガス required. |
GMAW-P | Pulsed Gas Metal Arc Welding | Pulsed transfer. Better control on thin material. |
GMAW-S | Short Circuiting Gas Metal Arc Welding | Short-circuit transfer. Sheet metal, root passes. |
GTAW | Gas Tungsten Arc Welding | TIG. High-quality root passes, thin materials. |
GTAW-P | Pulsed Gas Tungsten Arc Welding | Pulsed TIG. Better heat control. |
FCAW | Flux Cored Arc Welding | Tubular wire. Higher deposition than SMAW. |
FCAW-G | Gas Shielded Flux Cored Arc Welding | Dual-shield. External gas + flux core. |
FCAW-S | Self-Shielded Flux Cored Arc Welding | Innershield. No external gas. Field/outdoor use. |
SAW | Submerged Arc Welding | Highest deposition. Flat/horizontal only. |
SAW-S | Series Submerged Arc Welding | Dual-wire SAW for wider coverage. |
PAW | Plasma Arc Welding | Constricted arc. Keyhole technique for CJP. |
EGW | Electrogas Welding | Vertical-up, single pass. Heavy plate. |
SW | Arc Stud Welding | Shear connectors. D1.1 Clause 9. |
CAW | Carbon Arc Welding | Copper alloy backing. Repair applications. |
Section 10Finishing Designators — A2.4 §6.13
Added adjacent to the 仕上げ記号. Specifies the mechanical method to achieve the required weld face contour. Does not specify quality of finish.
Chipping
Grinding
Hammering
Machining
Planishing
Rolling
Unspecified
Method left to fabricator
FAQFrequently Asked Questions
All A2.4:2020 weld symbol types (fillet, 8 groove variants, plug, slot, spot, seam, stud, surfacing, backing, edge), 10 NDE examination method symbols (RT, UT, MT, PT, VT, ET), 9 supplementary symbols, 136 process letter designations, 7 finishing designators, and D1.1:2025 clause cross-references for each symbol type.
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Surface methods (MT, PT, VT, ET) examine the weld surface or near-surface region and have arrow-side or other-side significance on the symbol. Volumetric methods (RT, UT) penetrate the full weld 板厚 and are typically centered on the reference line with no side preference per A2.4 section 17.5.5.
Per A2.4 section 6.12.1, the 溶接工程 letter designation (e.g., SMAW, GMAW, FCAW-S) is placed in the tail of the welding symbol. An application mode suffix from Table A5 may be added (e.g., GTAW-AU for automatic gas tungsten arc welding). The tail may be omitted when no process reference is needed per section 6.12.5.
Weld symbols placed below the reference line specify the arrow side of the joint (the side the arrow points to). Symbols placed above the reference line specify the other side. For welds requiring preparation of only one member (bevel-groove, J-groove, flare-bevel), the arrow shall have a break and point toward the member to be prepared, per A2.4 section 6.4.1.
The tail may contain: the welding process letter designation from Table A2 (e.g., SMAW, GTAW-AU), a specification or 基準 reference, a WPS number, or a detail/cross-section reference when basic symbols are inadequate. The designation TYP (typical) avoids repeating identical symbols. When no references are required, the tail may be omitted entirely, per A2.4 section 6.12.
Two or more reference lines indicate a sequence of operations. The first operation is specified on the reference line nearest the arrow; subsequent operations are specified sequentially on additional reference lines. This is distinct from subreference lines, where multiple weld types branch from a single reference line and the welding sequence is undetermined, per A2.4 sections 6.7.1 and 6.8.