If you have a quote on your desk that says “MIG welded, ground and powder coated”, you’re not the only one wondering what you’re paying for. If you’ve typed “what is welding and how does it work” into Google, here’s the short answer. Welding joins two pieces of metal by melting their edges, often with added filler metal, so they flow together and set as one solid piece.
At Swift Metal Fabrication, our Eumemmerring workshop team brings 55 years of combined experience to MIG and TIG welding every week. This guide is for people getting metalwork made, not people learning to weld.
Key takeaways
- Welding joins metal by melting the edges of two parts, usually with added filler metal, so they fuse into one solid piece as they cool.
- Most custom work in Australia uses arc welding: MIG, TIG, stick (MMAW) or flux-cored.
- Good welds start with good preparation.
- Mild steel, stainless steel and aluminium each need a different approach.
- Structural welding in Australia follows AS/NZS 1554.
What Is Welding?
Welding joins metals with heat. The metal being joined is called the parent metal. When heat melts its edges, a small molten puddle forms, called the weld pool, and the welder usually feeds in filler wire or rod to build up the joint.
As the pool cools, it hardens into a single piece of metal. That’s the big difference from other joining methods. Bolts and rivets clamp parts together, and soldering or brazing bond them with a lower-melting alloy without melting the parts themselves. The joint stops being a joint and turns into the metal itself.
That permanence is both the upside and the catch. You can’t unscrew a weld, so measurements need to be right before the work starts.
How Does Welding Work? Step by Step
Every arc weld follows roughly the same six stages, whether it’s a garden gate or a structural beam.
- Prepare and fit up. The welder removes rust, oil, paint and mill scale, bevels thick edges if needed, then clamps or tacks the parts in place.
- Strike the arc. An electric current jumps a small gap between the electrode and the metal, creating an arc that runs at thousands of degrees.
- Form the weld pool. The welder moves the arc along the joint at a steady pace, feeding filler metal into the molten pool.
- Shield the metal. Air is the enemy of hot metal, causing bubbles and weak spots. A shielding gas such as argon, or an argon and CO₂ mix, covers the pool. Some processes use flux instead.
- Cool and fuse. The pool solidifies into a raised weld bead. The metal beside it, called the heat-affected zone, doesn’t melt but does change slightly, which is why welders control heat carefully on thin metal.
- Inspect and clean up. The welder checks the bead, removes slag or spatter, and grinds the weld if the finish needs it.
From what we see on our workshop floor, most weld problems trace back to step one. A brilliant welder working on dirty, badly fitted metal is like a chef cooking with stale ingredients. Skill can only cover so much.
Main Types of Welding Used in Australian Workshops
There are dozens of welding processes, but four cover almost all custom fabrication in Australia. Quotes often use the technical acronyms, so we’ve included them.
| Process | How it’s shielded | Best suited to | Where you’ll see it |
| MIG/MAG (GMAW) | Gas, with a fed wire | Fast, strong welds on mild steel | Gates, fences, frames, trailers |
| TIG (GTAW) | Argon, with a tungsten electrode | Neat welds on thin metal, stainless and aluminium | Balustrades, benchtops, visible joints |
| Stick (MMAW) | Flux-coated rod | Windy outdoor and site work | Farm and on-site repairs |
| Flux-cored (FCAW) | Flux inside a hollow wire | Heavy sections | Structural steel, heavy plant |
MIG and TIG handle most custom shop work. If you’re unsure which suits your job, our guide to MIG vs TIG welding compares them side by side. Laser, electron beam and friction welding also appear in online lists, but they’re high-volume factory processes that rarely come up for one-off jobs.
Which Metals Can Be Welded, and What Changes With Each?
Most common metals can be welded, but each behaves differently under heat.
Mild steel is the most forgiving, and MIG joins it quickly and strongly.
Stainless steel usually calls for TIG. Welding leaves a rainbow-coloured heat tint that can rust if it’s left alone. A post-weld clean and passivation brings that protection back, a step worth paying for if your project faces salty bayside air.
Aluminium is the tricky one. It pulls heat away fast and has a tough oxide skin that melts at a far higher temperature than the metal underneath, so it needs AC TIG or specialist MIG equipment.
Galvanised steel can be welded, but the zinc coating burns off and releases harmful fumes. For new work, it’s usually better to weld first and then galvanise or powder coat.
What Makes a Good Weld? How to Check the Work You’re Paying For
You don’t need to be a welder to spot the basics. A good weld has a consistent, even bead that blends smoothly into the metal on both sides, with no cracks or gaps at the edges.
Watch for these warning signs:
- Porosity: pinholes from trapped gas
- Undercut: a groove melted into the metal along the weld edge
- Heavy spatter: blobs of metal stuck around the joint
- Lumpy beads: a sign of poor technique or wrong settings
For structural work in Australia, welding follows the AS/NZS 1554 series. Part 1 covers steel structures, and Part 6 covers structural stainless steel. Welds are classed as GP (general purpose) or SP (structural purpose), with SP welds held to stricter limits on defects and inspection. The Australian Steel Institute’s technical note on welding explains how these standards fit into steel design.
If your job carries load, like a mezzanine, staircase or awning frame, ask how the welders are qualified. Many Australian welders qualify under AS/NZS ISO 9606.1, which tests their skill against specific welding procedures.
What Happens After Welding?
A finished weld is rarely the end of the story. Most jobs move on to grinding, metal polishing or powder coating.
Weld quality shows through the finish. Spatter and rough beads stand out under powder coat like a pea under a mattress, so clean welding gives the coating a smooth surface to bond to.
Planning a Welded Project in Melbourne? What to Tell Your Fabricator
The more your fabricator knows upfront, the better they can choose the process and price the job. Start with the metal type and how thick it is. Not sure? Describe what the part is for, and they’ll work out the rest. Mention whether it will live indoors, outdoors or near the coast, and whether it will carry weight or people.
Add the finish you want and how many pieces you need. A drawing helps, but a photo with measurements works too. These details shape everything from welding method to labour time, as our breakdown of metal fabrication cost explains.
Get Your Welding Done Right the First Time
Knowing what welding is and how it works makes you a sharper buyer. Good results come down to preparation, process choice and skill. Send your drawings or photos to our Eumemmerring team, and we’ll talk you through the options for welding services in Melbourne.
Frequently Asked Questions
Is welding stronger than bolting?
A properly made weld can be as strong as the parent metal. Bolting suits parts that need to come apart for transport or maintenance, and many projects use both.
Can you weld stainless steel and mild steel together?
Yes, as long as the welder picks a filler made for mixed metals, such as 309L stainless wire. The mild steel side still needs protection against rust.
How long does welded steel last outdoors in Melbourne?
It depends more on the finish than the weld. Bare steel rusts quickly, while powder-coated or galvanised steel lasts many years.
Do I need a qualified welder for my project?
For anything structural or load-bearing, yes. Ask about qualifications such as AS/NZS ISO 9606.1 and whether the work follows AS/NZS 1554.