AWS A2.4 §6.3, §6.4 · D1.1:2025 Figure 5.1 Type 4
Bevel 開先溶接 Symbol
How to read a ベベル開先 溶接記号 — the broken arrow convention, perpendicular leg rule, 開先角度, and D1.1:2025 事前認定 CJP joint details.
Ask Flux
Bevel Groove Weld Symbol — Anatomy
Single bevel — 45°
Joint cross-section
Broken arrow convention
Double bevel (K-groove)
Two critical rules: (1) The perpendicular leg is always on the left per A2.4 §6.3. (2) The broken arrow points to the member that must be beveled per A2.4 §6.4.1. A straight arrow means either member may be beveled.
Bevel Groove Dimensions — A2.4 Figs 7.10, 7.11
Root opening + groove angle
Double bevel, different depths
The Broken Arrow
Which Member Gets the Bevel?
The broken arrow is the most important — and most commonly misunderstood — convention in 溶接記号表示 reading. Per A2.4 §6.4.1:
Broken arrow (kinked) — the arrow has a visible bend or kink in its shaft. It points at the member that must receive the edge preparation. The 製作者 has no choice — that specific member gets beveled.
Straight arrow — per A2.4 §7.1.3.2, a straight arrow means either member may have the desired edge shape. The fabricator can choose which member to bevel based on access, material 板厚, or shop preference.
The broken arrow applies to all asymmetric groove types: bevel groove, J形開先, and フレア面取り開先. It does NOT apply to symmetric 種類 like V形開先, U形開先, or フレアV形開先.
Field reality: Many drawings omit the broken arrow when it should be present. If you see a bevel groove symbol with a straight arrow and it is not obvious which member should be beveled, ask the engineer before proceeding. Beveling the wrong member wastes material and may require re-製作.
D1.1:2025 Figure 5.1
Prequalified Single-Bevel CJP Details
| Process | Designation | Root Opening | Groove Angle | Positions |
|---|---|---|---|---|
| SMAW | B-U4a | 1/4" | 45° | All |
| SMAW | B-U4a | 3/8" | 30° | All |
| GMAW/FCAW | B-U4a-GF | 3/16" | 30° | All |
| SAW | B-U4a-S | 1/4" | 45° | F only |
| SAW (backgouge) | B-U4b-S | 0 | 60° | F only |
T-joints and corners: Single-bevel is especially common in T継手 and 角継手 connections (TC-U4a designation). The perpendicular member typically remains square while the abutting member receives the bevel. Same angle rules apply.
Common Questions
Bevel Groove Weld Symbol FAQ
What is the broken arrow on a bevel groove weld symbol?
The broken arrow (bent arrow) is an AWS A2.4 convention used to identify which member in a joint receives the bevel preparation. Per A2.4 §6.4.1, when only one member is to be prepared, the arrow has one break (a kink or bend) and points toward that member. A straight arrow means either member may be beveled. The broken arrow applies to bevel groove, J-groove, and flare-bevel groove symbols. It is the most commonly misunderstood welding symbol convention.
What is the difference between a bevel groove and a V-groove?
In a bevel groove, only one member is beveled while the other remains square. In a V-groove, both members are beveled symmetrically. The bevel groove symbol has a perpendicular leg (always on the left per A2.4 §6.3) and an angled line representing the bevel. The V-groove symbol is symmetric with no perpendicular leg rule. Bevel grooves use the broken arrow convention; V-grooves do not. Bevel grooves use less weld metal than V-grooves but produce asymmetric distortion.
Why is the perpendicular leg always on the left?
Per AWS A2.4 §6.3, fillet, bevel-groove, J-groove, and flare-bevel-groove weld symbols shall be drawn with the perpendicular leg always to the left. This is a fixed drawing convention that ensures consistent reading across all welding drawings. The perpendicular leg represents the square (unprepared) face of the joint. It does not indicate direction, joint orientation, or which member is square — that information comes from the broken arrow.
What is the 規格 bevel groove angle per D1.1?
Per D1.1:2025 Figure 5.1 (prequalified CJP joints), standard single-bevel groove angles are: SMAW — 45° with 1/4-inch root opening (all positions) or 30° with 3/8-inch root opening (all positions). GMAW/FCAW — 30° with 3/16-inch root opening (all positions). SAW — 45° with 1/4-inch root opening or 60° with zero root opening (flat only, with backgouge). Using a groove angle less than the prequalified minimum voids the prequalification.