What is a flare-bevel groove weld?

A flare-bevel groove weld is made in the groove formed between the curved surface of a tube, pipe, or round bar and an adjacent flat surface. The groove geometry is determined by the radius of the curved element, not by a machined bevel. AWS D1.1:2025 specifies effective throat as a fraction of the radius R of the round member for prequalified applications.

Are flare-bevel groove welds prequalified under AWS D1.1:2025?

Yes, under specific conditions in the prequalified joint configuration tables. The joint must be filled to the depth that achieves the specified effective throat, the process and position must meet prequalification requirements, and the base metal combination must be in the prequalified group. Deviation from these conditions requires PQR qualification testing.

Does a standard groove weld PQR qualify flare groove welds?

Not automatically. Flare groove welds are a geometrically distinct joint type. A PQR run on a standard CJP or PJP groove weld in flat plate does not demonstrate adequate fusion in the curved-surface geometry of a flare groove. If the project requires qualified (non-prequalified) flare groove welds, the PQR should use representative flare groove test coupons.

What does 'flush-filled' mean for a flare-bevel groove weld?

Flush-filled means the weld metal is deposited to a height level with or slightly above the plane of the flat surface, filling the full concave groove. AWS D1.1 prequalified effective throat values for flare-bevel welds assume flush-filled condition. Under-filled welds have a smaller actual throat than the theoretical value and must be evaluated accordingly.

Flare-bevel and flare-V groove welds: WPS requirements

Flare-bevel and flare-V groove welds appear at tube-to-plate connections. AWS D1.1:2025 has specific effective throat rules and prequalification limits.

Flare-bevel and flare-V groove welds appear wherever a round structural element meets a flat surface or another round element: circular hollow structural sections (HSS) welded to baseplate, round bar shear connectors, tube-to-gusset connections, and similar configurations. They look simple in the field — the welder fills an obvious groove — but the WPS, effective throat calculation, and prequalification logic are more complicated than they appear, and WPS documentation errors on these welds show up regularly in third-party audits.

Joint geometry: what makes a flare groove different

A standard groove weld is made in a groove formed by machined or cut bevel faces — the geometry is explicit and controlled. A flare groove is formed by the curved surface of a tube or round bar as it meets an adjacent surface. The groove shape is determined by the radius of the round member, not by the welder or the fabricator.

This matters for effective throat. In a standard CJP groove weld, the throat equals the depth of the groove — the full thickness of the part for a CJP. In a flare groove weld, the groove is curved and the weld metal must be built up to achieve a specified throat. The theoretical throat is a fraction of the radius R of the round member, specified in AWS D1.1:2025 prequalified joint tables.

Flare-bevel groove weld: Formed between one curved surface (round tube or bar) and one flat surface (plate or flat web). Common application: HSS tube-to-baseplate connections, angle or channel-to-plate where the rolled radius contacts the plate.

Flare-V groove weld: Formed between two curved surfaces. Less common in structural steel fabrication; appears in some round bar-to-round bar configurations and certain connection types.

Effective throat for prequalified flare groove welds

AWS D1.1:2025 specifies effective throat for prequalified flare-bevel groove welds as a fraction of the radius R of the round member (where R = outside radius of the tube or bar). For the common case of SMAW, GTAW, and other processes in the standard flush-filled condition, the effective throat is 5/16 × R.

For GMAW and FCAW in the flat position, where the process characteristics produce deeper penetration into the curved surface, the effective throat may be taken as 5/8 × R — but only when the shop has demonstrated by qualification testing that the process achieves that penetration consistently. Without that demonstration, the conservative 5/16 × R value applies.

These fractions come from geometric analysis of how deep weld metal actually fuses into the curved groove. A larger tube has a larger R, which produces a deeper groove and a larger achievable throat. A small-diameter tube with a thin wall may have a radius small enough that the effective throat becomes a governing design constraint.

Rule library based on AWS D1.1:2025; verify against your governing edition.

Prequalification conditions

A flare-bevel groove weld is prequalified under AWS D1.1:2025 when:

The joint configuration matches the prequalified details in the joint tables — the groove must be left open (no close fit that blocks access) and the round element must have a radius that produces an accessible groove geometry.
The filler metal is prequalified for the base metal combination and process.
The welding position is within the prequalified envelope for that joint type.
The weld is flush-filled — the weld metal is deposited to the theoretical throat depth required by the design.

Under-filled flare groove welds are a common field problem. A welder who stops when the groove "looks full" may have deposited metal only partway up the curved groove, leaving an effective throat smaller than the WPS requires. QC inspection of flare groove welds should include a check of the bead profile relative to the flat surface, not just a visual check that the groove is covered.

For prequalified use, see prequalified WPS under AWS D1.1 Clause 5 for the broader prequalification framework and what conditions must be met across all prequalified joint types.

WPS documentation for flare groove welds

A WPS covering flare-bevel groove welds must document the joint type explicitly — not just "groove weld" but "flare-bevel groove weld." The essential variables in AWS D1.1:2025 Table 6.6 apply to flare groove welds the same as other groove welds: changes to process, filler classification, base metal group, position, and heat input that exceed the qualified limits require requalification.

Additionally, the WPS should specify:

Nominal radius range covered: The effective throat is a function of R. If the WPS is to be used across multiple tube sizes, the smallest radius in the range determines the minimum achievable throat, which must still meet the design throat requirement.
Fill condition requirement: Specify flush-filled explicitly. This gives the CWI a clear inspection standard: the weld is flush with the flat surface, not convex or concave.
Process-specific effective throat: If GMAW or FCAW is used and the shop intends to claim 5/8 × R effective throat, the supporting demonstration must be documented and attached to the WPS. Without it, the WPS should state 5/16 × R.

For a broader discussion of joint geometry documentation on WPSs, see CJP vs. PJP groove weld WPS requirements.

When PQR testing is required

Flare groove welds move from prequalified to test-qualified when any of the following conditions apply:

Out of prequalification range: The joint geometry, process, or base metal combination falls outside the prequalified tables. This is common with non-standard tube sizes, cold-formed square HSS with tight corner radii, or specialty alloys.
Claiming increased effective throat: If the design requires the 5/8 × R throat for GMAW or FCAW and the shop has not previously demonstrated this by test, a PQR is required before claiming it.
Owner specification requires test qualification: Some owners, particularly on high-consequence or seismic projects, require PQR test qualification for all groove welds regardless of prequalification eligibility.
ASME or alternative code governs: Projects under ASME IX or API 1104 do not use AWS D1.1 prequalification — all procedures require PQR qualification testing.

When PQR testing is required for flare groove welds, the test coupons should use the actual flare groove geometry — the same tube radius and plate combination as the production joint. A standard flat-plate CJP groove weld PQR does not demonstrate fusion behavior in the curved-surface geometry. See how to qualify a welding procedure for the general PQR process, keeping in mind that the coupon geometry must match the joint being qualified.

Common WPS deficiencies on flare groove welds

Third-party auditors and CWIs on structural projects with HSS base connections regularly find:

Wrong throat value on the WPS: The WPS documents effective throat at 5/8 × R without a supporting penetration demonstration. The design may be based on that throat; if the joint was actually built at 5/16 × R, there is a structural deficiency that has to be evaluated by the EOR.

Generic "groove weld" designation: The WPS says "groove weld" and the inspector checks for fusion and size per general groove weld criteria, without applying the flush-fill standard specific to flare groove welds.

No radius range specified: The WPS was written for a specific tube size and is being applied to a tube with a smaller radius, producing a smaller effective throat than the WPS documents.

Process-position mismatch: FCAW in the vertical or overhead position on a flare groove connection, where the prequalification table requires flat position for the increased throat claim, and the reduced prequalified throat is inadequate for the design load.

Managing WPS applicability across multiple joint types — groove, fillet, flare groove — is much easier with a digital procedure library that links each WPS to the joints and base metals it covers. WPS welding software keeps that mapping explicit so shops know which WPS applies before the first arc is struck.

Practical guidance for fab shops

For shops that regularly weld HSS connections to baseplate or gusset:

Write a dedicated WPS for flare-bevel groove welds, separate from your standard groove weld procedures. The joint type designation and effective throat documentation should be explicit.
Specify the tube radius range the WPS covers. If you work with multiple HSS sizes, either write separate WPSs or include a table of R values and corresponding effective throats.
Train welders on the flush-fill requirement. Many welders treat the flare groove like a fillet weld — the profile may look similar, but the fill requirement is different.
If the design uses 5/8 × R effective throat for GMAW or FCAW, run the penetration demonstration on actual tube-to-plate test pieces and document it formally before using those procedures in production.

For shops welding HSS assemblies that also require tubular connection qualification, see welding procedure requirements for hollow structural sections for how D1.1 treats tubular joints more broadly.