Steel Structure Quality Control & Inspection System
The three-level inspection system behind 200,000 tons of annual output: incoming material testing, in-process weld and dimensional control, and outbound verification — with every member traceable to its heat number and weld record.
A Quality Chain, Not a Quality Department
Quality in steel fabrication is a chain of gates, and each gate has a named owner, a measurable criterion and a document. We build that chain around the three-level system used across the industry: IQC (incoming), IPQC (in-process) and OQC (outgoing).
The System in One Line
IQC rejects bad steel before cutting starts; IPQC catches deviations while the member is still on the line; OQC verifies geometry, coating and documents before a single truck leaves the plant. Gate failure stops the flow — it never "continues to the next step and we will fix it later".
Where the Framework Comes From
The management system is certified to ISO 9001:2015, with environmental management under ISO 14001 and occupational health under ISO 45001. For European-destined projects, fabrication follows EN 1090-1/2/3 requirements (factory production control plus execution classes), and Chinese domestic acceptance follows GB 50205-2020. The result is that the same member can be documented against the standard demanded by a Chinese auditor, a European notified body or an American consulting engineer — the test methods and records are compatible even where the limit values differ slightly.
Traceability is not a slogan. Each member is stamped with a fabrication number that connects the heat number, the mill certificate, the cutting machine log, the weld map, the NDT report and the QC sign-off. If a client asks "show me the report for member G-125", the answer is a folder, not a promise. Two decades and ten million tonnes of experience is exactly what this discipline looks like.
Quality data is reviewed weekly, not annually: first-pass rate per product line, NDT rejection causes, coating DFT distribution and rework cost. When a trend appears — say, a rising porosity indication on one joint type — the WPS, the consumable batch and the welder roster are reviewed together before the next batch reaches that station. This is how the 99.2% first-pass figure is kept honest: it is a managed number, compared against its own history in every production meeting, not a marketing average.
The Six Inspection Gates Every Member Passes
Each gate below lists the criterion our QC inspectors hold against production. These are the numbers printed on our inspection forms — they are not illustrative.
Raw Material Inspection (IQC)
Every delivered heat is verified against the mill certificate and re-tested: yield strength, tensile strength, elongation and impact toughness, per GB/T 1591 (Q355, Q420) and GB/T 700 (Q235). Identity is confirmed by positive material identification (PMI) spectral analysis on sampled plates. A heat whose re-test does not match its certificate is quarantined and returned — it is not "re-marked" or blended into another batch. All certificates are filed by heat number, which later becomes the root of the traceability chain.
Cutting & Drilling QC
CNC flame and plasma cutting holds profile accuracy to ± 1.0 mm; drilled holes are positioned within ± 0.5 mm; bevel angles are controlled to ± 2°. First-piece inspection is performed at machine start, then every tenth piece is dimension-checked against the CNC drawing. Cut surfaces are inspected for notches deeper than 0.5 mm and dross, because a poor cut face becomes a stress raiser at the corner of a tension member — and because a rejected cut costs ten times more to fix after assembly than before.
Welding QC
Every welding procedure has an approved WPS backed by a qualified PQR. Welders are certified to GB 50661 or ASME IX for the exact process, position and material they run. Consumables follow storage and rebake rules — low-hydrogen electrodes are oven-stored at 120–150°C and rebaked at 350°C for one hour if exposed. For plates over ~30 mm, preheat runs 80–120°C and interpass temperature is capped at 230°C, logged on the weld data sheet by the responsible welder. Current, voltage and travel speed are monitored on automated lines via the digital weld management system.
NDT Testing
Nondestructive testing is applied on a level-based schedule: level-one complete-joint-penetration welds: 100% ultrasonic testing (UT), with radiographic testing (RT) where the detail or the client requires film; level-two welds: 20% UT; fillet welds on primary members sampled by magnetic particle (MT); dye penetrant (PT) for open, accessible joint details. Acceptance per AWS D1.1 and GB/T 11345. NDT technicians hold current level II/III certifications; instruments are calibrated against reference blocks every working day, and calibration records travel with the project dossier. Findings are reported as raw indications plus a conforming/non-conforming verdict — the client sees both.
Coating QC
Surface preparation is blast-cleaned to Sa 2.5 (ISO 8501-1) with a surface profile of 40–70 µm, verified by replica tape. Dry film thickness is measured per member: 80–120 µm primer plus 40–60 µm topcoat for a C3 environment, applied in controlled temperature and below 80% relative humidity. Adhesion is checked by ISO 2409 cross-cut (class 1) and, on sampled members, ISO 4624 pull-off (≥ 5 MPa). DFT readings follow the 90-10 rule: 90% of readings above the minimum, none below the absolute minimum. Any member outside that rule goes back through blasting, not just an extra coat over a contaminated surface.
Dimensional & Assembly QC (OQC)
Complex and repeat-production structures undergo trial assembly (dry fitting) in the shop before shipping — a full bay, a node cluster or a truss chord set, depending on transport limits. Measured limits: column length ± 3 mm, beam length ± 2 mm, section size ± 2 mm, and assembled verticality ≤ h/250. Bolt holes must align across mating parts without drift pins being hammered to correct — if a fit-up needs force, it is a fabrication defect, not a site problem. Outgoing QC attaches the final check sheet and the packing list to each load, and every loose item on the list is a quality incident, not a "minor omission".
NDT Coverage by Weld Level
The matrix below is the standard scope on our fabrication floor. Deviations only ever go one direction — higher coverage, requested by the client or the engineer.
| Weld Level | Method | Coverage | Acceptance Basis |
|---|---|---|---|
| Level 1 (CJP, primary stress) | Ultrasonic (UT) | 100% | AWS D1.1 / GB/T 11345 |
| Level 1 (where specified) | Radiographic (RT) | Per drawing / client | AWS D1.1 / GB/T 3323 |
| Level 2 (secondary) | Ultrasonic (UT) | 20% | AWS D1.1 / GB/T 11345 |
| Fillet welds, primary members | Magnetic particle (MT) | 10% sampled | AWS D1.1 surface class |
| Open joint details (tubes, nodes) | Dye penetrant (PT) | Per WPS requirement | AWS D1.1 surface class |
All methods are applied after the weld has cooled to ambient and at least 48 hours after completion where hydrogen embrittlement is a concern (per project specification). Every NDT report carries the inspector's certificate number and the instrument serial and calibration date.
Weld repair follows a closed loop we do not shortcut. A rejected indication is excavated, re-welded under the same qualified WPS with the same welder category, and re-tested at 100% coverage — the repair and the re-test are both recorded in the NDT docket alongside the original report. A given location is allowed a maximum of two repairs; a third defect in the same joint triggers a joint-level review with the client's engineer before any further work. Repair welding on quenched-and-tempered or cold-climate grades adds a preheat verification step to the checklist, because a local reheat cycle can do more damage to a thick section than the original pass. The repair rate per production line is tracked in the same weekly review as first-pass yield, so a recurring joint problem surfaces as a trend, not as a surprise in a pre-shipment audit.
Measured, Not Claimed
Management Systems Behind the Gates
The quality gates run on top of audited management systems. Certificates are available on request and renewed on schedule — an expired certificate is a compliance incident, not a paperwork delay.
ISO 9001:2015
Quality management system covering design, fabrication, erection and service, audited annually by an accredited certification body.
EN 1090 CE Marking (EXC3)
Factory production control to EN 1090-1 with execution class 3 documentation — the level required for most structural steel placed on the EU market.
ISO 14001:2015
Environmental management covering shot-blast dust control, waste streams, solvent handling and energy use across the 300-acre production base.
ISO 45001:2018
Occupational health and safety management (successor to OHSAS 18001) for 3,000,000 m² of annual construction and all workshops.
Grade A Steel Structure Design
Class-A special design qualification for light steel structures — one of a small handful in China — so QC can start at the drawing, not at the plate.
Special-Grade Manufacturing & Contracting
Top-grade steel structure manufacturing and general contracting licenses, keeping design, fabrication, erection and inspection under one accountable chain.
Quality Control Questions from Buyers
What does 100% traceability actually mean in your factory?
It means any member in any project can be walked back to its raw material in minutes. The chain is: fabrication number stamped on the member → cutting record (machine, date, heat) → heat number → mill certificate and IQC re-test results → weld map with welder IDs → NDT reports → coating DFT record → outgoing QC sign-off. When we say "traceability", we mean the file exists and the links are unbroken for every heat that entered the plant. Auditors test this by picking a random member on the shop floor and asking for its documents; walking questions like "where did this column come from" are answered by the batch system, not by memory. For projects with strict requirements, unbroken traceability is what allows a consultant to accept material on site without re-testing every heat.
Do you accept third-party inspection?
Yes — and we schedule for it rather than tolerate it. Before production, the client and we agree on inspection gate points: raw material release, first-piece dimensional, weld NDT, coating and final assembly. Third-party inspectors (SGS, BV, TUV, Intertek, or the client's own engineers) attend those gates with full access to our records, without appointment at any other time. Reports go directly to the client unedited — we do not "review and correct" them first, because then they would not be independent. Typical third-party hold points add two to five days to a production cycle; our planners build them into the schedule instead of treating them as surprises. In practice, projects with third-party inspection reach the same first-pass rate as our internal audits, which is precisely why we prefer them: they prove the system works.
How do you control weld quality before we ever visit the shop?
Weld quality is engineered in four layers. First, procedure: every joint is welded to an approved WPS whose parameters were proven by a PQR, so "how the welder feels that day" is not the standard. Second, people: welders are certified to GB 50661 or ASME IX for the exact process, position and thickness, and re-qualified on a fixed cycle or after a 6-month gap. Third, environment: consumables are oven-controlled, preheat and interpass temperatures are logged, and welding stops when humidity exceeds 80% RH. Fourth, verification: level-one welds get 100% UT, and every NDT report names the welder, the inspector certificate number and the instrument calibration date. You do not need to be in the workshop to check any of this — the WPS package, welder certificates and reports are issued with the batch and can be audited remotely before shipment.
Can you supply EN 1090 / CE-compliant documentation?
Yes. For European-destined projects we structure the dossier to EN 1090-1 factory production control: material certificates (EN 10204 type 3.1 or 2.2 as specified), WPS/PQR to EN ISO 15614-1, welder qualification to EN ISO 9606, NDT to EN ISO 17640/17636/23278, and a Declaration of Performance where the scope requires CE marking. Execution class is agreed at contract stage — we document to EXC2 or EXC3, and the verification documents follow class 3.1/3.2 where the spec calls for them. If your consultant works to a different framework — AWS D1.1, AS/NZS 5131 or the local code — we produce the same physical records against that framework instead. The steel, the welds and the measurements are the same; only the cover sheets change.
Request Our QC Documentation Package
Send us your project's inspection requirements and we will return a sample QC dossier: inspection gate list, NDT scope, document templates and a production-schedule-aware inspection plan within 24 hours.
Request the QC Package