If you buy fabrication work or run a welding shop, you have almost certainly asked yourself one of these five questions about industrial welding. Our team has worked through them for years, both on the shop floor and in client meetings. In this article we go through each one, explain the reasoning behind our recommendations, and point out where the common mistakes hide. That way you can judge the answers for yourself instead of simply taking our word for it.
Which welding process fits my material and thickness?
There is no single best process, and anyone who insists otherwise is usually selling something. The right choice depends on three things: the base metal, the plate or pipe thickness, and how strict your inspector is about weld quality. Each process trades speed against skill and cleanliness, so the decision really comes down to which trade-off your project can live with.
On our own jobs, MIG/MAG has become the workhorse for high-output carbon steel frames. We once watched a fabrication line double its daily weld metres by moving one repetitive joint from stick welding to MIG. TIG still gives the cleanest bead on thin stainless steel and on the root passes of critical joints, but it is slow and demands a lot from the welder. Stick welding stays tough and portable, which is why site repair crews keep using it when they cannot haul a wire feeder up a scaffold. Submerged arc lays long, straight seams in thick plate very quickly, though only in the flat position.
The mistake we see most often is assuming aluminium or stainless will behave like mild steel. They will not. Both need far tighter control of shielding gas and surface cleanliness. A shop that skips that discipline usually finds out during the first radiographic check.
- MIG/MAG: carbon steel, high output, moderate skill required.
- TIG: thin stainless steel and critical root passes, high skill, low travel speed.
- SMAW: site work and maintenance, portable, low equipment outlay.
- SAW: long seams in thick plate, flat position only.
How do I check that a welder is really qualified?
A welder’s certificate is a record of a past test, not a guarantee of what that person will produce today. It shows the welder passed a test in a given process and position under a named standard such as ISO 9606, ASME Section IX or AWS D1.1. That is valuable, but it is only the starting point of a sound check.
Begin by matching the certificate against the process and position written in your Welding Procedure Specification. A certificate for 3G vertical-up tells you little about a 6G pipe joint overhead. Then ask when the welder last worked that process. We once inherited a crew whose certificates were four years old, with no continuous production in between. Their first test coupon failed, a useful reminder that a certificate fades when the skill goes unused. In any doubtful case, test a coupon or inspect the first production joints before you trust the whole batch. For the fundamentals behind this, our earlier guide on the basics of industrial welding walks through the process families in more detail.
Which documents must exist before production welding begins?
Before the first arc is struck, four documents should be in place: the Welding Procedure Specification (WPS), the Procedure Qualification Record (PQR), the welder qualification records, and an Inspection and Test Plan (ITP). Think of them as the recipe, the evidence that the recipe actually works, the cook’s credentials, and the checklist for tasting before the dish leaves the kitchen.
Paperwork alone never guarantees quality. The procedure has to be followed on the shop floor, and inspection has to verify that it was. The gap we meet most often sits with small workshops running production without a properly qualified WPS. The parts look fine at the bench, final inspection rejects them, and the rework bill arrives weeks later. It is usually far larger than the time it would have taken to qualify the procedure in the first place.
Why do welds fail, and how can I prevent the common defects?
The usual suspects are porosity from gas trapped in the weld, lack of fusion, undercut, cracking and distortion. Cracking worries engineers most, especially in higher-strength steels and thick sections where the metal cools quickly and traps hydrogen. Once a crack sits in a load-bearing joint, the repair is expensive and the risk never fully goes away.
Prevention comes down to controlling heat and cleanliness. Preheat and interpass temperature slow the cooling rate so the metal has time to release hydrogen. Low-hydrogen electrodes must stay dry, because moisture picked up from the air is a direct route to hydrogen cracking. We store ours in heated ovens and issue only what a shift will use. Good fit-up and a planned welding sequence keep distortion within tolerance, which matters far more on long assemblies than most people expect.
Be careful with material certificates too. In one investigation we traced a defect back to a steel grade that differed from what the paperwork claimed. If the material has not been verified, treat it as a risk to be tested rather than assumed safe.
What really drives the cost of industrial welding?
Labour is normally the largest share of the bill, followed by consumables and shielding gas, energy, inspection and rework. Inspection is the line item buyers most often leave out when they compare a low quote, and it is the one that hurts most later. Radiographic, ultrasonic and dye penetrant testing each add cost, and a bid that omits them is not cheaper, only incomplete.
Costs in Vietnam vary with region, metal prices and project size, so treat any comparison as a direction rather than a price list. The broad pattern is that MIG/MAG and SAW win on speed for long runs, while TIG costs more in labour but earns its place on critical joints where the inspection bill is already high.
When you compare bids, ask every supplier to itemise what is included. If inspection and a rework allowance are missing, the lower figure is not the real figure, and you will pay the difference on site.
Frequently asked questions
Do I always need a WPS for industrial welding?
For code-controlled work such as pressure equipment or structural steel, yes, and the client will almost certainly ask for it. A simple, non-critical repair may get by with a lighter documented procedure, but writing one down still costs far less than cutting out a failed joint later.
Can one welder handle both stainless and carbon steel?
Often yes, but the qualification must cover each material and each process separately. Stainless needs different consumables and gas control, so check that the certificate names both materials before you assign the job.
How long does it take to qualify a new welding procedure?
It depends on the test coupons, the inspection scope and the laboratory schedule. In our experience, plan for several days to a few weeks and build that time into the project plan before production starts.
Is visual inspection enough, or do I need NDT?
Visual inspection only catches surface defects. Internal flaws such as subsurface porosity or cracks need non-destructive testing to be found. For critical or code-governed joints, visual inspection alone is not sufficient.
Which standards apply to welding in Vietnam?
The governing standard depends on the sector and the customer. Many projects reference ISO 9606 for welder qualification, ASME Section IX for procedures and AWS D1.1 for structural steel. Confirm with your client which standard the contract names before you write the first procedure.
Choosing a fabrication partner comes down to a handful of checks: documented WPS and PQR records, certified welders for your process, real inspection capability, and references on comparable work. A small workshop may do simple parts well but fall short on code-controlled jobs, so match the shop to the job rather than to the price. If you need that full combination, a specialist such as MONA Media is worth evaluating against the same criteria. Ask for their WPS list, welder certificates and recent inspection reports before you commit. For the engineering side of joint design, our team also covers TIG welding for aerospace structural assemblies in more depth.