MIG Welding WPS Guide for First-Time MIG Welders

My welding foreman said this to me on my second day at a Gulf fabrication yard. I had already set up the machine, cleaned the joint, and was about to pull the trigger. He walked over, stopped me, and asked one question - had I read the WPS for this joint.

I had seen the document pinned near the welding booth but honestly had no idea what to do with it. That moment became the most important five-minute lesson of my welding career. He sat with me, opened the WPS, and went through every line. After that day I never picked up a torch on a production job without reading the WPS first.

If you are a first-time MIG welder stepping into a professional fabrication shop, refinery project, or overseas contract, this guide explains exactly what a WPS is, what every line in it means, and how to follow it correctly before you start welding.

What Is a WPS

A Welding Procedure Specification - WPS - is a formal document that provides detailed instructions on how to perform a specific welding operation. It serves as a technical guide for welders, detailing the processes, materials, and parameters required in a welding project.

Think of the WPS as a recipe for the weld. Every ingredient - wire grade, shielding gas, voltage range, travel speed, preheat temperature, interpass limits - is listed. Your job as the welder is to follow that recipe exactly, every time, on every joint covered by that document.

Without a WPS, welders could use variable techniques, resulting in inconsistent welds that could compromise the structural integrity of the project. Variations in heat input can cause problems such as excessive distortion, cracking, or lack of fusion. By following a WPS, these risks are minimized.

On every serious industrial project I have worked on - Gulf refinery shutdowns, Singapore shipyard fabrication, Saudi ARAMCO connected contracts - the WPS was a controlled document. The QC inspector checked that the welder had access to the correct WPS before any production welding started.

WPS, PQR and WQT - What Is the Difference

First-time welders often confuse these three documents. Here is a clear explanation of each.

WPS - Welding Procedure Specification

This is the document you as the welder read and follow. It tells you how to weld a specific joint on a specific material. Written by a welding engineer and approved by the QA/QC department.

PQR - Procedure Qualification Record

PQR is a record of the variables and test results obtained during the qualification of a welding procedure. It serves as evidence that the WPS has been successfully tested and is qualified for production.

The PQR is the supporting test record that proves the WPS works. Before any WPS is issued for production use, test welds are made following those parameters and the coupons are tested - bend test, tensile test, or radiographic examination. The PQR records those test results. You as the welder do not write the PQR - the welding engineer does.

WQT - Welder Qualification Test

A welder qualification record shows that a welder has tested and is qualified to make specific types of welds. It is often required for certain codes such as AWS D1.1 Structural Welding Code. Having a WQR is an indication that a welder can apply the welding procedure specification to produce high-quality welds.

Your WQT record is your personal qualification document - it shows which processes, positions, and material groups you are qualified to weld. When you arrive on a new project, the QC department checks your WQT record against the WPS requirements to confirm you are approved to do that welding work.

What Information Is Inside a MIG Welding WPS

The first time I opened a WPS properly, it looked like a page full of codes and numbers I did not understand. My chargehand pointed to each section and explained it one by one. Now I can pick up any WPS and extract everything I need in under two minutes.

A WPS contains the following key information: welding process (GMAW/MIG, GTAW/TIG, SMAW), volts, amps, travel speed, travel direction, polarity, wire welding transfer mode (globular, spray, short circuit), shielding gas or flux core specification, number of passes, electrode size, pre and post weld heat treatment temperatures and times, and joint design including material thickness, bevel angles, and root opening dimension.

Let me break down each item in plain language for first-time welders.

Welding Process - Confirms which process is approved. For MIG welding it will show GMAW. Some WPS documents approve multiple processes - for example GMAW for fill and cap passes and SMAW for the root pass on pipe joints.

Base Material - The material type and grade being welded. P1 group for carbon steel, P8 for austenitic stainless steel. If you are welding SS304 plate and the WPS says P8 Group 1, that is your confirmation the procedure covers that material.

Filler Metal - The exact wire grade approved. ER70S-6 for carbon steel, ER308L for SS304. Never substitute a different wire grade without QC approval - even if the alternative seems similar.

Shielding Gas - Gas type and flow rate range. C25 mix for mild steel, 98% Argon + 2% CO2 for stainless. Flow rate is usually specified as a range - for example 15 to 20 LPM. Set your regulator within that range.

Welding Parameters - Voltage range, wire feed speed range, and travel speed range for each pass. Root pass, hot pass, fill passes, and cap pass may each have different approved parameters.

Preheat Temperature - Minimum base metal temperature before welding starts. For standard carbon steel under 20mm thickness this is often ambient temperature. For higher carbon content materials, alloy steels, or thick sections a specific minimum preheat - for example 100 degrees Celsius - is required. The QC inspector checks preheat with a temperature stick or contact thermometer before approving the start of welding.

Interpass Temperature - Maximum temperature allowed between passes. On stainless steel this is typically 150 degrees Celsius maximum. On carbon steel structures it may be 250 to 300 degrees Celsius. Exceeding interpass temperature causes microstructural changes and potential loss of toughness properties.

Joint Design - Bevel angle, root gap, root face dimensions. If the WPS says 60 degree included angle with 2 to 4mm root gap and 1.5mm root face, that is what your pipe fit-up must show before welding is approved.

Welding Position - Positions the WPS covers. A WPS qualified for 3G covers flat and horizontal as well. A WPS qualified for 6G covers all positions. If the WPS only covers 1G and 2G, you cannot use it for vertical or overhead welding.

WPS Quick Reference Table

How I Follow a WPS on Site - My Step by Step Habit

On any production welding job, this is exactly what I do before the first arc strike.

Collect the WPS from the site supervisor or chargehand. Read base material, filler metal, gas, and parameters. Check my wire spool - confirm wire grade and diameter match the WPS. Check gas cylinder - confirm gas type, adjust flow rate to within specified range. Check joint fit-up against WPS joint design dimensions - root gap, bevel angle, root face. If preheat is required, use temperature stick to verify. Tack weld only at approved locations. Run a short test bead on scrap plate to confirm machine settings produce acceptable arc sound and bead profile within the approved parameter range. Then proceed to production welding.

My QC inspector on one Saudi project told me after three months of working together - "I never have to follow you around because I know you read the WPS before you start. That saves both of us time."

That is the professional standard every first-time welder should aim for.

For proper MIG welding machine settings and how they relate to WPS voltage and wire speed parameters, our complete settings reference is at MIG Welding Settings – Voltage and Wire Speed.

Common First-Time WPS Mistakes

Ignoring the preheat requirement. On carbon steel above 25mm thickness or on alloy steel, preheat is critical. Skipping it causes hydrogen-induced cracking - a defect that may not appear until hours after welding. My foreman once rejected a full day of pipe welding on a thick-wall spool because the welder had not preheat checked a single joint.

Setting parameters outside the approved range. If the WPS says 19 to 22 volts and you run at 24 volts because the arc feels better, you have violated the procedure. Any QC inspection that catches machine settings outside WPS range results in weld rejection and potential procedure deviation report.

Using wrong wire grade. Looked similar on the label, different AWS classification. This happened once on a stainless job in my team - someone used ER316L where ER308L was specified. The joints looked perfect visually. The PMI (positive material identification) test caught the wrong filler composition. Full rework followed.

Not checking position qualification. If your WQT record only covers 1G and 2G but the joint is in 3G vertical position, you are not qualified to weld it under that WPS. The welder must hold the correct position qualification to work on each joint type.

Understanding WPS requirements also helps significantly during welding job interviews. Supervisors test WPS reading ability specifically. Our interview preparation guide covers this in detail: MIG Welding Interview Questions – How I Passed My Interview.

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FAQ

Q: What is the difference between WPS and PQR? WPS is the document the welder follows during production welding. PQR is the supporting test record proving those WPS parameters produce acceptable welds. The welding engineer prepares both - the welder uses the WPS.

Q: Can a welder change WPS parameters on site? No. All parameters in the WPS are approved within specific ranges. Welding outside those ranges violates the procedure. Any change to WPS parameters requires formal re-qualification and QC approval before production welding continues.

Q: What is preheat in a WPS and why does it matter? Preheat is the minimum base metal temperature required before welding starts. It reduces the cooling rate of the weld zone and prevents hydrogen cracking, especially on thicker and higher-carbon steel sections. The WPS specifies the minimum preheat temperature for each base material group.

Q: How do I know if my WQT covers the WPS requirements? Your WQT record lists the approved process, base material group, filler metal group, positions, and thickness range you are qualified for. Compare these directly against the WPS requirements. If any item does not match, you need a new qualification test for that specific variable.

Q: Does every welding job require a WPS? On professional industrial projects - oil and gas, refinery, pressure vessel, structural steel fabrication under code compliance - yes, a WPS is always required. For simple maintenance or non-code fabrication work, some companies use pre-qualified procedures without a formal WPS. Gulf and overseas projects always require WPS compliance.

Conclusion

The WPS is not paperwork. It is the technical backbone of every quality weld you make on a professional project. Read it before you start. Follow every parameter within range. Check your preheat. Confirm your wire grade and gas match. Verify your fit-up dimensions.

Welders who treat the WPS as optional are the ones who produce rework. Welders who make WPS reading a habit before every shift are the ones QC inspectors trust - and contractors keep rehiring across multiple projects.

That five-minute lesson my chargehand gave me on day two of my first Gulf contract shaped every professional welding habit I have built since. Get comfortable with WPS documents early in your career. It is one of the fastest ways to separate yourself from average welders in any job market.