Tack welds and temporary attachments — strongbacks, erection lugs, fit-up clips, spreader bars — are the unglamorous workhorses of structural fabrication. They hold alignment while the permanent welds go in, and then they either get consumed by the production weld or get cut off and ground clean. Because they look temporary, shops sometimes treat them as outside the scope of the welding procedure program. That is a mistake with real consequences: a cracked tack buried under a fill pass, or a strongback gouged off carelessly, can create a defect in finished structure that ultrasonic or radiographic testing will find during final inspection.
AWS D1.1:2025 holds temporary welds to the same standard as production welds in every respect that matters for structural integrity.
What counts as a temporary weld
AWS D1.1 distinguishes between:
- Tack welds incorporated into the final weld — these become part of the permanent joint and must meet all WPS and quality requirements
- Tack welds that will be completely removed — still subject to WPS and preheat requirements, because HAZ cracking doesn't care whether the weld is temporary
- Temporary structural attachments — strongbacks, erection aids, fit-up fixtures welded directly to the base metal — these are temporary welds by function but are governed as production welds by the code
Any weld made to structural steel in the scope of a D1.1 contract falls under the code. "Temporary" describes its function in the fabrication sequence, not its exclusion from the quality system.
Preheat: no exemption for tack welds
The most common misconception is that tack welds don't need preheat because they are small. The opposite is true. A small, fast-cooling tack deposit has a steeper thermal gradient than a production weld bead, which drives the HAZ to higher hardness — precisely the condition that promotes hydrogen-assisted cracking. AWS D1.1 requires that preheat requirements determined by Annex I (carbon equivalent method) or by Table 6.2 apply to tack welds.
If the governing WPS for a SMAW E7018 fillet weld on A572 Grade 50 specifies a minimum preheat of 50°F [10°C], that same minimum applies to every tack weld in the joint. In cold-weather conditions, this means preheating the joint before tacking, not just before the production passes. See cold weather welding requirements for the full preheat verification procedure.
Rule library based on AWS D1.1:2025; verify against your governing edition.
Qualified welder and WPS requirements
Tack welds incorporated into the final joint
A tack weld that will be left in place and consumed by subsequent passes is part of the structural weld. It must be:
- Made by a welder qualified for the applicable position and process
- Made under a qualified or prequalified WPS
- Inspected before fill passes cover it
Inspecting incorporated tack welds before they are buried is a hold-point that gets missed in high-pressure production environments. A cracked tack concealed under fill passes becomes a linear discontinuity in the finished joint that will likely fail visual or volumetric examination — at the worst possible moment, during final inspection or after erection. CWI hold point inspection discusses setting up formal hold points in the inspection plan.
Tack welds to be removed
Tack welds that will be completely removed still require a qualified welder and applicable WPS, because a cracked tack in a steel assembly can propagate into the base metal under handling loads before removal. Shops that assign tacking to uncertified fitters are generating latent defects.
Temporary attachment welds
Erection lugs, strongbacks, and fit-up aids welded to the base metal require the same qualified welder and WPS coverage. Their removal requires specific care — see below.
Strongback and temporary attachment removal
Thermal cutting
Thermal cutting (oxy-fuel or plasma) is permitted to remove most of a temporary attachment, but the cut must stop before reaching the base metal surface. AWS D1.1 requires leaving a small stub that is then removed by grinding or air-arc gouging. Cutting flush with the base metal with a torch risks:
- Thermal damage and hardening of the base metal surface
- Undercut and gouging that can create stress concentrations
- Hydrogen pickup in the HAZ if the cut is too aggressive
The standard approach is to cut within 1/4 in [6 mm] of the base metal surface and grind the remainder flush. The direction of grinding should be parallel to the primary stress direction where possible, to minimize stress concentration from grinding marks.
Grinding flush and inspection
After a temporary attachment is removed, the area must be ground smooth and inspected. What to look for:
- Arc strikes: if the welder struck an arc on the base metal adjacent to the attachment weld, the arc strike must be addressed — blended smooth if superficial, or qualified as a repair weld if it created a notch or cracked HAZ. See arc strike repair AWS D1.1 for the repair procedure.
- Surface cracks: particularly in higher-carbon or higher-strength steels (Group II or III per Table 6.9), the HAZ of a temporary weld can crack during service. Magnetic particle (MT) or liquid penetrant (PT) examination of the cleaned area is good practice and may be required by contract.
- Laminations or delaminations: thermal cutting can expose pre-existing laminations in the base metal plate.
- Gouge depth: if grinding creates a depression deeper than 1/32 in [1 mm] into the base metal, treat it as a repair subject to WPS coverage.
Tack weld quality requirements
Whether incorporated or removed, tack welds must be free of:
- Cracks (including crater cracks — fill all craters)
- Excessive porosity
- Significant undercut that will not be consumed by subsequent passes
A cracked tack that will be incorporated is a defect in the finished weld. The repair procedure — excavating the crack and rewelding — is more disruptive after fill passes are in place than catching it before they are applied. Inspectors should make tack-weld inspection a standard pre-production hold point, not an afterthought.
Documentation in the WPS and inspection records
The WPS covering tack welds does not require a separate document from the production WPS — the same procedure applies — but the Welding Procedure Specification should state whether it covers tack passes, and the process record (typically the CWI's inspection log or an internal fabrication traveler) should note:
- Who performed the tacking
- The WPS used
- Preheat verified and at what temperature
- Disposition of tack welds (incorporated vs. removed)
Audit failures on temporary welds almost always stem from the same root cause: treating them as outside the quality system because they feel informal. An audit-ready welding procedure library covers tacking because tacking is welding.
Practical checklist for shops
Before tacking any joint in a D1.1 contract:
- Confirm the WPS covers the process, position, and base metal for the tack weld
- Verify welder qualification for that WPS covers the position being tacked
- Check preheat — measure with a contact pyrometer or temp sticks, not by feel
- Inspect tack welds before fill passes cover them; note disposition on the traveler
- For temporary attachments: plan the removal method and verify the base metal area after grinding
The production floor shortcut of letting uncertified fitters tack components "just to hold them" is a consistent source of audit findings and occasionally of real field defects. AWS D1.1 doesn't have a carve-out for tacks — and neither should your quality program.
To track welder qualification coverage for tacking assignments alongside production assignments, see how welder qualification matrices can surface gaps before the work starts.