Selecting a structural welding partner is a high-leverage decision. The right shop delivers safe, code-compliant weldments that arrive on time and install cleanly; the wrong one locks in rework, schedule slips, and risk.
This guide walks you through what to look for, how to compare providers using data, and a practical scorecard you can reuse.
What Structural Welding Covers
Structural welding applies to load-bearing fabrications such as building frames, bridges, platforms, mezzanines, pipe racks, cranes, and heavy equipment bases.
It typically involves carbon and low-alloy steels (e.g., ASTM A36, A572 Grade 50), sometimes stainless or duplex where corrosion or hygiene matters, and is governed by standards such as AWS D1.1 (steel), AWS D1.5 (bridge), AWS D1.6 (stainless), and, for pressure-related components, ASME Section IX for procedure and welder qualification.
Common Welding Processes
- SMAW (Shielded Metal Arc Welding): Versatile, tolerant of fit-up and outdoor work, slower deposition rates.
- GMAW/MIG (Gas Metal Arc Welding): High productivity, good for long fillets and multi-pass groove welds; sensitive to wind and gas coverage.
- FCAW (Flux Cored Arc Welding): Excellent deposition for structural fillets; self-shielded options suit field work.
- GTAW/TIG (Gas Tungsten Arc Welding): Precision and cleanliness for critical root passes or thin sections; slower and costlier.
- SAW (Submerged Arc Welding): Very high deposition and deep penetration for long, straight seams on thick plate and beams.
Typical Materials and Codes
Materials: ASTM A36, A572 (Gr 50/55/60/65), A588 (weathering), A992 (wide-flange shapes), and, when needed, 304/316 stainless or duplex grades.
Codes & Documents: WPS (Welding Procedure Specification), PQR (Procedure Qualification Record), WQTR (Welder Qualification Test Record), ITP (Inspection & Test Plan), M
Key Factors to Consider
Code Compliance and Procedure Control
Ask for a procedure matrix showing each WPS, its essential variables (process, filler, position, preheat/interpass, base metal group), and supporting PQRs. A robust provider controls WPS issues/revisions, trains on it, and audits compliance on the floor.
Welder Qualification and Continuity
Confirm welders are tested to the appropriate code positions (e.g., 3G/4G for plate, 6G for pipe) with current continuity logs (no lapses >6 months unless re-tested). Look for cross-qualifications across processes you’ll actually need (FCAW, GMAW-Spray/Pulse, SAW).
Materials and Thickness Capability
Match your thickness range and joint types to shop capacity. Can they weld 2″ plate with controlled heat input? Do they maintain preheat for thick HSLA steels? Do they stock common wire/gas mixes and low-hydrogen controls for high-restraint joints?
Joint Preparation, Fit-Up, and Fixturing
Quality starts with cut accuracy and bevel prep. Ask about CNC plasma/oxy cutting tolerances, bevelling machines, and dedicated fixtures for repeat builds. Good fixturing minimizes distortion and speeds inspection.
Production Capacity and Lead Time
Tour the shop. Count welding stations, cranes, positioners, rotators, and beam lines. Ask for average WIP, takt time, and the bottleneck (fitting, welding, machining, coating?). Capacity transparency is a good predictor of schedule reliability.
Quality Control and NDE Capability
A strong QC program includes ITPs, hold/witness points, calibrated gauges, and trained inspectors. NDE should be matched to risk:
- VT (Visual): Always.
- MT/PT: Surface cracks on fillet/groove toes.
- UT/RT: Volumetric examination of critical CJP (complete joint penetration) welds.
Request recent NDE failure rates and repair logs to see the trend and responsiveness.
Traceability and Documentation
From MTRs to welder stamps and weld maps, traceability protects you during audits and in service. Look for digital document control with revision history and controlled issuance to the floor.
Equipment and Automation
Positioners, manipulators, and SAW heads drive repeatability and throughput. Pulse-MIG power sources help bridge gaps and manage heat input on thinner members. For repetitive subassemblies, ask about robotic cells and how they program and qualify them.
Design For Welding Support
The best suppliers co-engineer with you. They’ll suggest joint simplifications, fillet size optimizations, and standardization of details to reduce passes without compromising capacity or fatigue life.
Safety and EHS
A mature safety culture correlates with process discipline. Check TRIR trends, PPE compliance, fume extraction, weld screen use, and handling practices for heavy sections.
Supply Chain and Finish Operations
End-to-end capability (machining, blast, prime, galvanize/paint, kitting) reduces handoffs and delays. If they outsource coating or galvanizing, ask how they control dip distortion and vent/drain hole design on closed sections.
Data-Driven Evaluation Framework
Subjective impressions aren’t enough. Use a weighted scorecard so cross-functional teams can converge on a defensible choice.
KPI Weights and Definitions
Below is a typical weighting scheme you can adapt to your priorities.
| KPI Category | Weight | What To Measure | Why It Matters |
| Quality | 30% | NDE reject rate, rework %, first-pass yield, weld size/length variance | Rework and hidden defects inflate cost and risk |
| Delivery | 25% | On-time delivery (OTD), average lead time, schedule adherence | Structural projects hinge on sequence and critical path |
| Cost | 20% | Piece price, setup, NDE costs, packaging/logistics | Total landed cost beats low unit price |
| Technical Capability | 15% | Code coverage, thickness range, process breadth, fixturing/automation | Reduces engineering risk and expands options |
| EHS & Compliance | 10% | Safety record, traceability, document control, audits | Predicts stability and audit readiness |
Weighted Score (0–100) = Σ (KPI Score 0–100 × Weight). For example, a provider with 90 in Quality and 80 in Delivery would contribute 27 and 20 points respectively with the above weights.
Example Benchmark Ranges
Use realistic, defensible targets to anchor scoring. The figures below are practical ranges for many structural programs; adjust to your risk and complexity.
| Metric | Good (Score 90–100) | Acceptable (70–89) | Poor (<70) |
| NDE Reject Rate (UT/RT on CJP) | ≤1.0% | 1.1–3.0% | >3.0% |
| Rework Rate (All Welds) | ≤2.0% | 2.1–4.0% | >4.0% |
| First-Pass Yield | ≥98% | 95–97.9% | <95% |
| On-Time Delivery (OTD) | ≥96% | 90–95.9% | <90% |
| Lead Time Variability (Std Dev/Mean) | ≤0.15 | 0.16–0.30 | >0.30 |
| WPS Coverage (By Joint/Process) | 100% | 90–99% | <90% |
| Welder Continuity Lapses | 0 in 12 months | 1–2 | >2 |
| Document Traceability (Lot→Weld→Report) | Digital end-to-end | Mixed digital/paper | Paper-only/fragmented |
| Safety TRIR vs. Industry | ≤50% of industry | 51–100% | >100% |
Tip: When a provider sits in the “Acceptable” band, probe the trend. Improving metrics beats static “Good” numbers if you’re forming a long-term relationship.
Sample Supplier Scorecard
Here’s a filled-in example using the weights above. Scores are illustrative; replace with your audit data.
| KPI | Weight | Supplier A Score | Supplier B Score | Supplier C Score |
| Quality | 30% | 92 | 85 | 78 |
| Delivery | 25% | 94 | 88 | 83 |
| Cost | 20% | 82 | 90 | 95 |
| Technical Capability | 15% | 88 | 80 | 72 |
| EHS & Compliance | 10% | 95 | 85 | 80 |
| Weighted Total | 100% | 90.3 | 86.6 | 82.3 |
How the math works (Supplier A): (92×0.30) + (94×0.25) + (82×0.20) + (88×0.15) + (95×0.10) = 27.6 + 23.5 + 16.4 + 13.2 + 9.5 = 90.3
Interpretation: Supplier C is the cheapest (high Cost score) but lags on quality/tech; Supplier A wins on total value and schedule assurance.
Cost and Quotation Analysis
What Drives Cost
- Material: Grade, thickness, and scrap factors on plate/beam nesting.
- Labor: Weld time (passes, deposition rate), fit-up, and handling.
- NDE: VT always; MT/PT/UT/RT as required by your ITP.
- Heat Treatment/Preheat: For thick HSLA or impact-tested steels, thermal control adds time and utility costs.
- Fixtures/Tooling: One-time cost amortized over quantity; huge leverage for repeat work.
- Finishing & Logistics: Blast, coating/galvanizing, packing, and transport (oversize permits, escorts).
How to Compare Quotes
Normalize Scope: Ensure identical joint lists, weld sizes, NDE scope, tolerances, and coatings.
Ask For Weld-Hour Breakdowns: See how many hours are in fit-up vs. welding vs. NDE; anomalies reveal optimism bias.
Evaluate Deposition Strategy: Providers using SAW or pulse-MIG on long seams often have lower weld hours and less distortion.
Total Landed Cost: Include expedite risk, rework exposure, and schedule buffer costs—not just unit price.
Change Management: Understand rates for RFIs, ECNs, and drawing revisions.
Pilot, FAT, and Contracting
Trial Lot and Process Prove-Out
Run a small batch to lock in parameters, sequence, and inspection steps. Capture: heat inputs, pass maps, distortion measurements, and cycle times. Use the pilot to refine fixtures and confirm NDE acceptance criteria.
Factory Acceptance Test (FAT)
Define FAT content in the PO: dimensional reports, NDE certificates, coating DFT (dry film thickness) readings, bolt hole quality, surface prep grade, and packaging photos. Include witness points for critical welds or assemblies.
Acceptance Criteria and Warranty
Cite the governing code (e.g., AWS D1.1) and your project tolerances. Spell out acceptance classes, undercut/porosity limits, and the rework protocol. Require a workmanship warranty and specify the time window for latent defect claims.
Service-Level Agreement (SLA)
Tie OTD to measurable dates and define remedies for misses (e.g., expedited freight at supplier’s cost). Include document delivery timelines (weld maps, NDE reports, MTRs) since paperwork delays can stall installation.
Putting It All Together
A disciplined selection process looks like this:
- Pre-Qualification: Shortlist providers with proven code coverage and thickness range; collect WPS/PQR and safety data.
- On-Site Audit: Validate equipment, fit-up practices, preheat/interpass control, and document discipline.
- Pilot Build: Run a representative assembly; capture weld hours, distortion, and NDE results.
- Scorecard Review: Populate the KPI table and compute weighted totals; hold a cross-functional decision review.
- Contract & SLA: Lock testing, documentation, schedule, and change management terms.
- Ongoing Governance: Quarterly business reviews against the same KPIs; drive continuous improvement.