Insights /Trades 101
Welding Certifications Explained: What 6G, Structural, and Pipe Mean for a Staffing Order
Years of experience won't tell you if a welder can pass your weld test. The certification code will — if you know how to read it and write it into the order.
Contractors & Plant Managers6 min read
A welding certification code identifies the position tested (1G through 6G), the process used (stick, TIG, MIG, flux-core), the governing code body (AWS D1.1, ASME Section IX, API 1104), and the base metal and thickness range. A GC who orders by these specifics gets the right welder; one who orders by years of experience often doesn't.
Why the Code Matters More Than the Years on the Tools
Most staffing orders for welders still read something like "need three welders, five-plus years experience." That line feels specific, but it tells a staffing desk almost nothing about what the person can actually do under your weld procedure. Experience is a proxy. The certification code is the actual spec.
Say a sub orders an "experienced welder" for a mechanical room re-pipe and gets someone genuinely good — fifteen years running structural steel column welds on high-rises. That person may have never run an open-root joint in the 6G position on schedule 40 pipe. The first few welds fail X-ray, the inspector flags the QC package, and two days disappear to rework and re-testing. The fix wasn't a more experienced welder. It was a correctly specified cert requirement on the order in the first place.
Position Codes: What 1G Through 6G Actually Test
Position codes describe the orientation the welder was tested in, not how good they are. 1G through 4G apply to plate: flat, horizontal, vertical, and overhead. Pipe positions are different and harder. 5G is pipe fixed in the horizontal, with the welder moving around a stationary joint through flat, vertical, and overhead sections. 6G fixes the pipe at a 45-degree angle, forcing the welder through every position in a single continuous weld.
Because 6G covers every position at once, it's often treated as close to a universal pipe qualification — and it gets over-requested as a result. It's still only good for the diameter and thickness range the welder was actually tested on. A 6G cert earned on 2-inch schedule 40 doesn't automatically extend to 12-inch schedule 80 without a look at the qualifying variables underneath it.
Process and Code Body: Matching the Standard to the Scope
The process matters as much as the position. Stick (SMAW), TIG (GTAW), MIG (GMAW), and flux-core (FCAW) each produce different weld characteristics, and production welds often combine them — TIG root with stick fill is common on pressure piping because it gives a clean, X-ray-ready root pass with faster fill on top.
The code body governs what counts as acceptable and how it gets inspected. AWS D1.1 covers structural steel — columns, beams, platforms. ASME Section IX governs pressure piping, boilers, and vessels, which is the standard most process-plant and mechanical-room work falls under. API 1104 covers cross-country pipeline and uses different acceptance criteria entirely. AWS D1.6 covers stainless, D9.1 covers sheet metal and duct. A welder qualified under D1.1 structural isn't automatically qualified for ASME IX pressure piping even if the position code on paper looks identical — the two codes test and accept welds differently.
Thickness, Base Metal, and the Fine Print That Breaks Projects
Every certification is tied to a test coupon — a specific thickness and base metal, with a qualified range built off that coupon under the governing code's rules. A welder tested on three-eighths-inch carbon steel plate isn't automatically qualified for one-inch wall pipe, and isn't qualified for stainless or exotic alloys at all without a separate test.
Most governing codes also carry a continuity clause: a welder who hasn't worked in a given process and position for an extended stretch needs to requalify before going back on code work. A certification that's technically current on paper can still be stale in practice. If your staffing order doesn't ask when the welder last worked in that specific process and position, you're trusting a document you haven't fully read.
Writing the Cert Requirement Into Your Staffing Order
"Certified welder" is not a spec. A usable staffing order line looks more like this: two welders, GTAW root / SMAW fill, 6G, ASME Section IX, carbon steel schedule 40 through 80, active within the continuity window. That single line does more to prevent a failed weld test than any amount of years-of-experience language, because it gives the staffing desk a filter it can actually match against its bench instead of a gut-feel search.
It also protects you on the back end. If a weld fails inspection and the paperwork shows the order asked for the wrong code or process, that's a staffing order problem, not a bad-welder problem — and it's a problem you'll keep repeating on the next job if you don't fix the spec.
When to Require an On-Site Weld Test Anyway
A paper certification establishes eligibility, not performance on your project that day. Heat, awkward fit-up, fatigue, and unfamiliar joint configurations all affect how a qualified welder actually produces in the field. For code pipe, structural connections headed for X-ray or UT, or any scope where a failed weld means a schedule hit, many GCs and plant owners still require a coupon test against the actual project procedure before anyone touches a production joint — regardless of what the cert says.
That's the gap between "qualified" and "ready," and it's worth catching before the first production weld, not after the radiographic film comes back. A documented pre-screen on the staffing side exists specifically to close that gap.
Frequently asked
Does a 6G certification mean a welder can weld anything?
No. 6G describes the position tested — pipe fixed at 45 degrees, covering every orientation in one weld — not the process, code body, or material. A 6G cert is still limited to the diameter, thickness range, and base metal the welder was actually tested on, and to whichever process (stick, TIG, etc.) and code (ASME, AWS, API) governed the test. Treat 6G as one variable in the spec, not a universal pass.
What's the difference between AWS D1.1 and ASME Section IX?
AWS D1.1 governs structural steel welding — columns, beams, platforms, connections that carry structural load. ASME Section IX governs pressure piping, boilers, and vessels, which covers most process-plant and mechanical-room pipe work. The two codes have different acceptance criteria and different qualifying variables, so a welder certified under one isn't automatically qualified under the other even if the position code looks the same on paper.
How long is a welding certification good for?
Most governing codes build in a continuity requirement: a welder who goes an extended period without welding in the certified process and position has to requalify before working code scope again. A cert that's current on the document can still be effectively lapsed in practice. Staffing orders should ask when the welder last worked in that specific process and position, not just whether the cert exists.
Can a TIG-certified welder do stick welding scopes?
Only if they're also certified in SMAW (stick) for the applicable position, code, and material — TIG (GTAW) and stick are separate process qualifications. It's common in pressure piping to combine them on the same joint, using TIG for the root pass and stick for the fill, but that requires the welder to hold qualifications in both processes, not just one.
Let's staff your project.
Whether you need one electrician next week or a 20-person crew next month, we can scope it in 15 minutes.