AWS A2.4 §7 · D1.1:2025 Figure 5.1 Type 2

V-開先溶接 Symbol

How to read a V-groove 溶接記号 — 開先角度, root opening, single-V vs double-V. D1.1:2025 事前認定 CJP details for the most common groove 溶接の種類.

Ask Flux

V-Groove Weld Symbol — Anatomy

Single-V — 45°, R=1/4"

Joint cross-section

Double-V (X-groove)

PJP — (3/8) weld size

Key rule: The V-groove symbol is symmetric — both legs are equal angle. Unlike bevel or J形開先 symbols, there is no perpendicular-leg orientation rule and no broken arrow convention. Root opening goes inside the V. Groove angle goes above or below the weld symbol as appropriate (A2.4 §7.3.2).

V-Groove Dimensions — A2.4 Figs 7.1, 7.10

V-groove with all dimensions

Double V, different depths

D1.1:2025 Figure 5.1

Prequalified V-Groove CJP Details

D1.1:2025 Figure 5.1 (Type 2) specifies prequalified single-V-groove CJP butt joints. These are the most commonly used groove weld configurations in 構造用鋼.

Process	Designation	Root Opening	Groove Angle	Positions
SMAW	B-U2a	1/4"	45°	All
SMAW	B-U2a	3/8"	30°	F, V, OH
SMAW	B-U2a	1/2"	20°	F, V, OH
GMAW/FCAW	B-U2a-GF	3/16"	30°	F, V, OH
SAW	B-L2a-S	1/4"	30°	F only

Groove angle is the total included angle, not a per-side half-angle. A 45° groove angle means each member is beveled at 22.5° from the joint centerline. A 30° angle means 15° per side. Using less than the prequalified 最小 groove angle voids the prequalification.

Reading the Symbol

How to Read V-Groove Dimensions

The V-groove symbol follows the 規格 groove dimension rules from A2.4 §7. All dimensions go on the same side of the 基線 as the V symbol.

Root opening (R) goes inside the V — between the two legs. This is the gap between the members before 溶接. Per D1.1 Figure 5.1, fit-up tolerance is +1/4", −1/16" from the specified root opening.

Groove angle (α) goes above or below the weld symbol as appropriate per A2.4 §7.3.2. This is the total 含み角 of the prepared groove.

Groove depth (D) goes to the left without parentheses — only for PJP. For CJP, D is omitted.

Weld サイズ (S) goes to the left in parentheses — only for PJP. The parentheses distinguish it from groove depth. For CJP, both D and (S) are omitted.

Single-V vs Double-V

Single-V: V symbol on one side of the reference line only. The joint is prepared from one side. Used for most structural butt joints.

Double-V (X-groove): V symbols on both sides of the reference line. The joint is welded from both sides. Used on thick plate (>1") to reduce 溶接金属 volume and balance 溶接ひずみ. Per A2.4, the V-groove is a symmetric symbol, so axes align directly across the reference line.

Common Questions

V-Groove Weld Symbol FAQ

What is a V-groove weld symbol?

A V-groove weld symbol is a V-shape placed on the reference line of a welding symbol. Both legs of the V are equal and symmetrical, representing a joint where both members are beveled to form a V-shaped groove. It is the most common groove weld type in structural steel. The V-groove is symmetric — unlike the bevel groove, there is no perpendicular-leg orientation rule. Below the reference line means arrow side; above means other side.

What is the difference between a V-groove and a ベベル開先?

In a V-groove, both members are beveled symmetrically to form a V-shaped groove. In a bevel groove, only one member is beveled while the other remains square. The V-groove symbol is symmetric (no orientation rule), while the bevel symbol has the perpendicular leg always on the left per AWS A2.4 §6.3. The bevel groove also uses the broken arrow convention to indicate which member gets the bevel. V-grooves use more weld metal but distribute shrinkage evenly; bevel grooves are more economical but produce asymmetric distortion.

What is the standard groove angle for a V-groove per D1.1?

Per D1.1:2025 Figure 5.1 (prequalified CJP joints), the standard V-groove angles for butt joints are: SMAW — 45° with 1/4-inch root opening (all positions), 30° with 3/8-inch root opening (flat, vertical, overhead), or 20° with 1/2-inch root opening (flat, vertical, overhead). GMAW/FCAW — 30° with 3/16-inch root opening. SAW — 30° with 1/4-inch root opening (flat only). The groove angle is the total included angle, not a per-side half-angle.

What is the difference between single-V and double-V groove?

A single-V groove has the V-shape on one side of the reference line only — the joint is prepared and welded primarily from one side. A double-V groove (also called an X-groove) has V-shapes on both sides of the reference line — the joint is welded from both sides. Double-V is used on thick plate to reduce weld metal volume and minimize distortion by balancing shrinkage. Per A2.4, the V-groove is a symmetric symbol, so the axes align directly across the reference line in a double-V configuration.

Related Reference

More Groove Weld Pages

Related Tools

°F Preheat Calculator D1.1 表 5.8 lookup