Welding Symbols

Welding symbols let a drawing specify the type, size, location and finish of a weld without needing a separate note for every joint. The charts below cover the basic weld type symbols and the supplementary symbols used to add extra instructions to a weld symbol, referencing both the international ISO 2553 standard and the US AWS A2.4 standard.

The elementary weld symbols themselves are identical, or very close to identical, between the two standards — the real differences between ISO 2553 and AWS A2.4 mostly show up in how the full welding symbol is built up around them (arrow/reference line conventions, tail contents, and some supplementary symbols). Where that's the case it's noted in the table.

BASIC WELD SYMBOLS

BASIC WELD SYMBOLS — ISO 2553 & AWS A2.4
WELD TYPE	SYMBOL	STANDARDS	NOTES
Fillet		ISO 2553 & AWS A2.4	Same symbol in both standards
Square Groove		ISO 2553 & AWS A2.4	Same symbol in both standards
V Groove		ISO 2553 & AWS A2.4	Same symbol in both standards
Bevel Groove		ISO 2553 & AWS A2.4	Same symbol in both standards
U Groove		ISO 2553 & AWS A2.4	Same symbol in both standards
J Groove		ISO 2553 & AWS A2.4	Same symbol in both standards
Flare-V Groove		ISO 2553 & AWS A2.4	Same symbol in both standards
Flare-Bevel Groove		ISO 2553 & AWS A2.4	Same symbol in both standards
Plug / Slot		ISO 2553 & AWS A2.4	ISO 2553 refers to this as a "slot" weld; AWS A2.4 covers plug and slot with the same symbol
Spot / Projection		ISO 2553 & AWS A2.4	Same symbol in both standards
Seam		ISO 2553 & AWS A2.4	Same symbol in both standards
Backing		ISO 2553 & AWS A2.4	Same symbol in both standards
Surfacing		ISO 2553 & AWS A2.4	Same symbol in both standards
Edge		ISO 2553 & AWS A2.4	Same symbol in both standards

SUPPLEMENTARY SYMBOLS

These are added to a basic weld symbol, on or around the reference line, to give extra instructions about how or where the weld should be made.

SUPPLEMENTARY WELD SYMBOLS — ISO 2553 & AWS A2.4
SYMBOL MEANING	SYMBOL	STANDARDS	NOTES
Weld All Around		ISO 2553 & AWS A2.4	Circle placed at the junction of the arrow and reference line; same symbol in both standards
Field Weld		ISO 2553 & AWS A2.4	Filled flag at the junction of the arrow and reference line; same symbol in both standards
Contour — Flush		ISO 2553 & AWS A2.4	Straight line above the weld symbol; same symbol in both standards
Contour — Convex		ISO 2553 & AWS A2.4	Outward curved line above the weld symbol; same symbol in both standards
Contour — Concave		ISO 2553 & AWS A2.4	Inward curved line above the weld symbol; same symbol in both standards
Melt-Through		ISO 2553 & AWS A2.4	Filled lens shape on the side opposite the basic symbol; same symbol in both standards
Backing Bar		ISO 2553 & AWS A2.4	A letter (R for removable, or similar) is often added inside the symbol in AWS A2.4 to show whether the backing is removed after welding
Consumable Insert		ISO 2553 & AWS A2.4	Shown as a filled square sitting in the root of a groove weld symbol; same symbol in both standards

These are simplified reference renderings intended to help identify each symbol at a glance. For the exact proportions, dimensions and full rules on combining symbols, arrows, tails and reference lines, always refer to ISO 2553 or AWS A2.4 directly.