How Structural Steel Fabrication Works: The 8-Stage Process

Structural steel processing covers eight stages: (1) design and shop drawings, (2) material selection and procurement, (3) cutting and drilling, (4) bending and forming, (5) welding and assembly, (6) quality control and inspection, (7) protective coatings, and (8) delivery and site installation. Every stage must be completed and documented before moving to the next. In Australia, fabrication is governed by AS 4100, AS/NZS 5131 and AS/NZS 1554.

Whether you’re a builder pricing a commercial frame, an engineer specifying a structure, or a project manager commissioning a factory fit-out, structural steel ends up on nearly every shortlist. It’s strong, fast to erect, and adaptable to almost any design. But before any beam gets bolted into place, it goes through eight distinct stages, each one precise, each one documented, and each one a point where the quality of your fabricator either protects your project or creates problems you’ll spend months fixing.

This guide walks through every stage clearly, so you know exactly what a professional fabricator does, what questions to ask, and what to look for when you’re deciding who to trust with your project.

What Is Structural Steel Processing?

Structural steel processing is the complete set of steps that transforms raw steel sections, beams, columns, plates, hollow sections into finished, certified components ready to bolt or weld together on your site.

It sits between two other activities people often confuse it with:

• Steelmaking producing raw steel from iron ore (done at a steel mill, not a fabricator)
• Steel supply delivering standard sections from a steel distributor, unprocessed
• Steel fabrication/processing everything in between: cutting, drilling, welding, coating and documentation

What you’re buying from a fabricator is not just labour. You’re buying a documented, tested, quality-assured package that arrives on site ready to erect. The difference between a good fabricator and a poor one shows up most clearly in what’s missing from that package.

The 8 Stages at a Glance

#	Stage	What actually happens
1	Design & Shop Drawings	Engineering intent converted into fabrication-ready drawings with a full bill of materials
2	Material Selection & Procurement	Right steel grade sourced from certified suppliers with full mill certificate traceability
3	Cutting & Drilling	CNC saws, plasma cutters and drill lines cut and prep every section to exact tolerances
4	Bending & Forming	Press brakes and rolling machines create angles, curves and custom profiles where required
5	Welding & Assembly	Coded welders join components into structural assemblies under AS/NZS 1554
6	Quality Control & Inspection	Visual, dimensional and NDT checks; ITP, weld maps and material certs produced
7	Protective Coatings	Sandblasting, priming, painting, galvanising or intumescent fire protection applied
8	Delivery & Site Installation	Sequenced loads delivered and erected; bolted, surveyed and handed over

1. Design, Engineering & Shop Drawings

Where projects succeed or fail before a single cut is made

If you take nothing else from this guide, take this: the quality of the shop drawings determines the quality of everything that follows. Late drawings, drawings with errors, or drawings that haven’t accounted for real workshop constraints are the single biggest cause of delays, rework and cost blowouts on structural steel projects.

A complete set includes:

• Individual part drawings for every section, plate and assembly
• Connection details with weld sizes and bolt specifications
• A Bill of Materials (BOM) listing every steel item by grade, size and quantity
• An Inspection and Test Plan (ITP) defining quality checkpoints
• Erection information so the site crew can locate and orient every piece

At Kelly Steel, design and drafting is handled in-house. That matters because drawings produced inside the same business as the fabrication are aligned to real workshop processes from the start, fewer RFIs, fewer late revisions, and smoother delivery.

The governing standard is AS/NZS 5131 (Constructional steelwork fabrication and erection). Ask any fabricator you’re considering: do you fabricate to AS/NZS 5131, and can you provide a copy of your quality system? If they hesitate, keep looking.

2. Material Selection & Procurement

The grade you choose determines how strong your structure is

Structural steel in Australia is not one product. It comes in multiple grades, each with different yield strength, weldability and suitability for different applications. The most common grades under AS/NZS 3678 (flat products and plates) and AS/NZS 3679 (hot-rolled sections) are:

• Grade 250 (yield strength 250 MPa) secondary members, handrails, platforms, lightly loaded items
• Grade 350 (yield strength 350 MPa) the standard grade for primary structural steel: beams, columns, trusses
• Grade 350L0 same strength as 350, with improved low-temperature toughness for exposed or dynamic-load environments

Every piece of steel should arrive with a mill certificate, a document from the steel manufacturer confirming grade, yield strength, tensile strength, chemical composition and compliance with the relevant standard. A professional fabricator keeps these on file and includes them in the QA package they hand over at project completion.

If a fabricator can’t produce mill certificates for the steel in your project, that’s a serious red flag. It means there’s no paper trail confirming the material in your structure is what the engineer specified.

For more background on what raw materials go into fabricated steel, see the Kelly Steel guide.

3. Cutting & Drilling

CNC precision that eliminates guesswork on site

Once the right material is in the workshop, it’s cut to exact lengths and drilled for bolt holes. Modern fabrication workshops use CNC (computer numerically controlled) equipment that reads directly from the digital drawing files the same files your engineer signed off.

Cutting methods

• CNC band saw the standard method for cutting sections to length; fast, clean, no heat-affected zone
• Plasma cutting used for plate profiles, cope cuts (notching flanges so beams connect flush), and complex shapes; high-definition plasma achieves tight tolerances on thick plate
• Oxy-fuel cutting for very thick plate where plasma reach is limited
• Laser cutting for thin plate and sheet where micron-level accuracy is needed

Piece marking

After cutting, every section is piece-marked; a unique identifier matched to the shop drawing is stamped, stencilled or tagged onto the steel. On site, this is how the erection crew locates every single component without guesswork. Proper piece marking is one of those things that separates a professional fabricator from an amateur: if the marks are missing, sloppy or inconsistent, expect a slow, expensive erection.

4. Bending & Forming

When straight sections aren’t enough

Not every structural element is straight. Curved roof members, architectural arches, angled brackets, kick plates and swept handrails all require bending. Steel’s ductility and its ability to deform without fracturing is what makes this possible.

• Press brake applies force through a punch and die to create precise angles in plates and flat bar; used for connection brackets, cleats and base plates
• Section bending (roll bending) passes beams, channels and RHS through a set of rolls to produce a consistent curve; used for portal knees, curved purlins and architectural arches
• Plate bending large flat plates formed into cylinders or cones for tanks, hoppers and curved cladding supports

This is a cold process for most structural steel with no heating required. Where tight radii are specified, the fabricator should confirm the minimum bend radius to avoid cracking or compromising the section’s structural integrity.

5. Welding & Assembly

The stage most people think of and the one that’s most misunderstood

Welding is where individual components become structural assemblies. It’s also the stage with the most variation in quality between fabricators because welding quality is largely invisible until something goes wrong.

In a professional fabrication workshop, welding is a controlled, documented process governed by AS/NZS 1554 (structural steel welding). That means:

• Welders must hold current qualifications (coded welders) for the joint type and position they’re working in
• Each weld type must have a documented Weld Procedure Specification (WPS) and Procedure Qualification Record (PQR)
• Weld quality is inspected against defined acceptance criteria not just ‘does it look okay?’

Welding processes used in structural fabrication

• MIG (GMAW) Gas Metal Arc Welding; the workhorse of structural fabrication; high deposition rate, suitable for fillet and butt welds on primary and secondary members
• TIG (GTAW) Gas Tungsten Arc Welding; slower but produces cleaner, more precise welds; used where appearance or tight tolerances matter
• Flux-cored arc (FCAW) high-productivity process for thick plate and high-volume fillet welds
• Arc/stick (SMAW) used for on-site repairs and connections in restricted-access locations

Welding vs bolting what’s the difference?

Many structural connections are bolted rather than welded, especially on site. Bolted connections allow for adjustment during erection and can be disassembled if required. High-strength bolts are installed and torqued to the specification set out in AS 4100. A good fabricator’s QA package will include torque records for every bolted connection.

See how Kelly Steel manages structural steel fabrication across commercial, industrial and infrastructure projects.

6. Quality Control & Inspection

The paperwork that proves your building is safe

What does quality control in steel fabrication actually involve? Quality control in structural steel fabrication means visual weld inspection, dimensional checks against shop drawings, and non-destructive testing (NDT) of critical welds all documented in an Inspection and Test Plan (ITP). A compliant fabricator delivers a QA package including weld maps, material certificates, welder qualifications and NDT reports at project completion.

QC is not a final tick-and-flick. It runs throughout every stage. Here’s what it should look like:

• Incoming material mill certificates verified; sections checked for dimensional compliance before any cutting begins
• Fit-up assemblies checked for squareness, camber and hole alignment before welding
• Weld inspection every weld visually inspected; NDT performed where specified by the structural engineer
• Dimensional check finished assemblies measured against shop drawings
• Trial assembly for complex frames, a dry fit in the workshop confirms connections and alignment before paint and dispatch

Non-destructive testing (NDT) methods used in structural steel fabrication include ultrasonic testing (UT), which uses sound waves to detect internal weld defects; magnetic particle inspection (MPI), which detects surface cracks in ferromagnetic material; and radiographic testing (RT), which uses X-rays to image weld cross-sections. The method and extent required is specified by your structural engineer based on weld category.

Kelly Steel holds ISO 9001 certification the quality management system is independently audited. Every project package includes ITPs, weld maps, welder qualifications, material certificates, NDT reports, torque records and as-built mark-ups.

What to ask any fabricator before you commit Do you fabricate to AS/NZS 5131?Are your welders coded to AS/NZS 1554, with current WPS and PQR documentation?Do you hold ISO 9001 certification?What QA documentation will I receive at project completion?Can you provide mill certificates for all structural steel in my project?Do you carry out trial assemblies for complex frames?

7. Protective Coatings

What stops your steel frame from becoming a rust problem in 10 years

Uncoated structural steel corrodes. The right coating system depends on where your structure is located, what it’s exposed to, and whether fire protection is required. Your structural engineer specifies the exposure class and coating system. The fabricator’s job is to apply it correctly and document it.

Surface preparation

All steel is abrasive blasted to Sa 2.5 standard before coating. This removes mill scale, rust, oil and contamination, and creates a surface profile (measured in microns) that the coating can properly bond to. Skipping or cutting corners on preparation is the most common reason coatings fail prematurely.

Common coating systems

• Zinc-rich primer + intermediate + topcoat the standard system for most commercial and industrial steel; the zinc primer provides active galvanic protection at the substrate level
• Hot-dip galvanising the fabricated section is immersed in molten zinc; provides excellent corrosion protection for exposed structural steel, handrails and items in marine-adjacent or high-humidity environments
• Intumescent paint (passive fire protection) a fire-resistant coating that swells when exposed to heat, insulating the steel and delaying critical temperature rise; required on exposed structural steel in most commercial buildings under the National Construction Code
• Epoxy and specialty systems for chemical exposure, immersion service, or architecturally exposed steel where a durable decorative finish is specified.

8. Delivery, Erection & Site Installation

Where everything either comes together or doesn’t

How fabricated steel gets from the workshop to a standing frame depends entirely on how well the earlier stages were managed. When the drawings were right, the steel was cut accurately, the pieces are marked clearly and the loads are sequenced correctly, erection is fast and uneventful. When any of those things went wrong, erection is where you find out.

A professional fabricator sequences delivery loads matched to the erection plan primary columns first, then beams, then secondary steel, stairs and platforms. This minimises the steel sitting on a congested site waiting to be lifted, and reduces crane time (which is typically the most expensive line on an erection budget).

On site, the installation process involves:

• Checking hold-down bolt positions against the shop drawings before any steel arrives
• Crane-lifting and positioning primary columns and beams in erection sequence
• Installing and torquing bolted connections to AS 4100 specification
• Completing on-site welding and applying touch-up coatings at cut ends and field welds
• Survey set-out to confirm plumb, level and alignment before the frame is locked off

When the fabricator and the installer are the same company as they are at Kelly Steel transport, cranage, access windows and site sequencing are coordinated under one program. For Melbourne CBD and inner-city projects this typically includes managing night and weekend delivery windows. 

How Long Does Structural Steel Processing Take?

The honest answer: it depends on project scale, complexity and how quickly drawings get approved. But as a general guide for Melbourne projects:

• Design & drafting: 1-4 weeks heavily dependent on how quickly the structural engineer resolves RFIs
• Material procurement: 1-3 weeks standard sections are typically ex-stock; heavy plate or specialty grades may take longer
• Fabrication: 2-8 weeks for mid-size commercial projects; larger infrastructure packages run longer
• Coatings: 3-10 days for paint systems; hot-dip galvanising adds 1-2 weeks including transport
• Delivery & erection: staged weekly deliveries aligned to the builder’s erection sequence

The single biggest lever you have on lead time is drawing approval speed. Getting shop drawings to review promptly and resolving RFIs quickly can save weeks off a steel program. Delays at the drawing stage compound into delivery delays that affect every following trade. 

What Can Go Wrong and How to Avoid It

Most structural steel problems are not random. They cluster around the same failure points:

• Late or incomplete drawings the most common cause of delays; fix this by appointing your fabricator early and getting drawings into review as soon as engineer sign-off is achieved
• Wrong steel grade supplied prevented by requiring mill certificates and having an ITP that verifies incoming material against the BOM before fabrication begins
• Poor weld quality prevented by requiring coded welders, WPS/PQR documentation and weld inspection records; NDT where specified
• Coating failures almost always caused by inadequate surface preparation; ask for a coatings report specifying blast standard achieved and DFT (dry film thickness) readings
• Erection problems holes that don’t align, members that don’t fit, missing pieces; prevented by trial assemblies, accurate piece marking and a single point of accountability across fabrication and installation