What Is 3G Welding? Position, Technique & Test Guide

A welding instructor once watched a confident shop welder fail a plate test three times in a row — not because his flat welds were bad, but because gravity turned against him the moment the plate stood upright. That vertical plate coupon is called 3G, and it is the position that separates a welder who can make pretty beads from one who can actually control a pool of molten steel.

What Is 3G Welding? The Direct Answer

3G welding is a groove weld made on plate held vertically, with the seam running straight up (or straight down) the face of the metal. That is the whole concept. The \”3\” in the code means vertical position and the \”G\” means groove weld, according to the AWS welding position designation system, where 1 = flat, 2 = horizontal, 3 = vertical, and 4 = overhead. We will break that numbering system down later in this guide, but the key point right now is that 3G describes orientation. It says nothing about the process, the joint design, or the metal being welded.

In practice, a 3G weld comes from standing two plates on their edges, beveling the edges that face each other, tacking them together, and running a vertical weld from the root of the joint all the way to the cap. The plates are set so the seam climbs toward the welder’s face, and the weld progresses upward in a straight vertical line. Most 3G production work and nearly all 3G qualification tests are run uphill: torch and electrode travel from the bottom of the joint toward the top, working against gravity the entire way.

What the physical setup actually looks like

Picture 3/8 in. (10 mm) A36 steel plate about 12 inches wide by 12 inches long, clamped in a welding positioner so it stands vertically like a wall. The facing edges carry a bevel, and a backing bar behind the joint catches molten metal and supports the root. That is a typical 3G welder performance test coupon in structural steelwork. The welder tacks the coupon, runs a root pass with something like an E6010 electrode, follows with fill passes on E7018, and finishes with a cap pass, all climbing the plate.

One detail is worth flagging early. In many qualification programs the coupon is tacked in position and may not be moved once tacking is complete. You cannot lay it flat to weld the root pass and then stand it back up for the cap. That single rule has ended more 3G tests than bad technique ever has, so read your code book before you light the torch.

Why 3G matters

Vertical groove welding shows up wherever a structure puts a seam on a wall rather than a floor: building columns and erection seams, bridge girders and diaphragms, pressure vessel and tank shells, silo and hopper work, and a good share of heavy equipment and ship repair. Once a welder can run a vertical uphill groove cleanly, they can usually adapt to most other field positions, which is why 3G carries so much weight in the industry.

It also matters because of what it proves. 3G is one of the most widely used welder qualification test positions in North America. Pass a 3G coupon on a covered electrode procedure and, under AWS D1.1 structural welding code rules, you are typically credited with groove welds in flat, horizontal, and vertical positions, with the thickness range extending upward. One test often unlocks structural work in three positions at once, which is why shops and training providers lean on it so hard. Exact qualification ranges, bend test requirements, and acceptance criteria come up in the certification section.

Then there is the honest part: 3G is genuinely harder than it looks. The pool has to be held in the joint while gravity pulls it straight down. The puddle heats faster than the welder expects, the electrode angle drifts as the seam rises, and slag runs back into the arc. A welder can lay a beautiful flat bead all afternoon and lose control the moment the plate stands up.

What this guide covers

Coming up we will decode the full position code system so you can read any AWS, ASME, or ISO designation, compare 3G against 1G, 2G, 4G, 3F, 5G, and 6G, work through uphill versus downhill progression and what each one qualifies you for, walk through step-by-step 3G technique with settings and pass sequence, diagnose the defects that punish vertical welders, and lay out the safety, inspection, and career payoffs. For a quick comparison of the four basic plate positions first, the Miller guide to the four basic welding positions makes a good companion read.

One last framing before we go deeper: 3G is not a specialty trick. It is a fundamental position most professional welders will work in for a career. Understanding it properly is what separates a hobbyist who can make a clean bead on a flat table from a welder who can control molten steel in any orientation.

How Welding Position Codes Work: Numbers, Letters, and Standards

If you have ever picked up a welding procedure specification or stared at the back of an electrode box, you have seen codes like 3G, 2F, or PC and wondered what they actually mean. The good news is the system is not random. Once you learn the two halves of a code, you can read any welding position in the world.

Every position code has two parts, and each part answers a different question. The number tells you where the joint sits in relation to gravity. The letter tells you what kind of weld you are making. That is the entire logic behind the AWS system used in North America, and it is the logic behind the answer to “what is 3G welding?”

The Numbers Tell You Gravity’s Position

The number half of the code describes the orientation of the joint relative to gravity and the welder’s body:

• 1 = Flat. The work is held horizontally and you weld on top of it, looking down at the joint.
• 2 = Horizontal. The work is vertical, but the weld runs across the plate as you travel along it.
• 3 = Vertical. The work is vertical and the weld axis itself runs up or down the plate.
• 4 = Overhead. The work is held horizontally and you weld underneath it, torch above your head.

One wrinkle trips people up: for plate groove welds, the number describes the weld axis, the direction the seam travels. In a 3G coupon the plate stands on edge and the weld runs straight up it. In a 2G coupon the same plate stands on edge but the weld runs across it horizontally. The numbers stay the same; what changes is the orientation of the work and the travel direction relative to gravity. That is why the welding positions chart every shop wall is covered with draws each position as a little stick figure of the welder and the joint.

The Letters Tell You the Type of Joint

The letter half of the code answers a completely different question: what shape of joint are you making?

• G = Groove weld. Prepared edges are joined so that weld metal fills the gap between them. Think butt joint, V-groove, square groove, double V.
• F = Fillet weld. One member sits at an angle against another and the weld fills the triangular corner. Think lap joint, T-joint, corner joint.

That is the whole letter code in practice. Combined, 3G means a vertical-orientation groove weld and 3F means a vertical-orientation fillet weld. The two halves are independent, which is why the standard set runs 1G, 1F, 2G, 2F, 3G, 3F, 4G and 4F, with pipe positions adding their own numbers for 5G and 6G coupons.

What the Codes Describe, and What They Don’t

One point deserves emphasis for anyone new to the trade: a position code describes orientation relative to gravity. It says nothing about your process, your filler metal, the plate thickness, or whether the joint is square, single V, or double V. A 3G groove weld can be made with stick, MIG, TIG, or flux core, and every one of them carries the same three-character code.

The codes come from published standards, and each region has its own flavor:

• AWS A3.0M is the standard welding terms and definitions document, where the formal position nomenclature is defined.
• AWS A2.4 covers the symbols used on drawings and engineering documents, so a designer can call out a specific weld orientation on a detail sheet.
• ISO 6947 provides the international system. ISO 6947:2019 assigns letter codes to plate groove positions and also carries a numerical set for the same four positions, where 100 is flat, 130 is horizontal, 135 is vertical up, and 136 is vertical down.
• ASME Section IX handles qualification. Position and vertical progression appear under QW-405, and QW-405.2 treats a change to vertical-uphill progression as a variable that has to be qualified separately.

You will meet the same codes on all-position welding rod data sheets and in every WPS. Filler metal specs list the positions each product is approved for, and the WPS ties a qualified position to a specific joint, thickness, and process.

AWS and ISO Side by Side

AWS code	ISO 6947:2019	Position
2G	PC	Horizontal groove weld, plate vertical, weld axis horizontal
3G uphill	PF	Vertical groove weld, travel upward
3G downhill	PG	Vertical groove weld, travel downward
4G	PE	Overhead groove weld, plate horizontal, weld underneath

Once you can read the numbers and the letters, drawings, WPS paperwork, and electrode boxes all become far less mysterious. The four basic positions explained and a position chart like the one your shop should have taped to the wall will do more for your weld quality than another stick of good rod.

The Four Plate Groove Positions: 1G, 2G, 3G, and 4G Compared

Seeing 3G beside the other plate groove positions makes the code click. The AWS position code gives you two things in two characters: a number describing how the joint sits relative to gravity, and a letter describing the weld type. Only four plate groove positions exist, and every plate groove test lands in one of them.

The geometry below follows this welding positions chart and Miller Welds’ overview of the four basic welding positions.

Position	Plate Orientation	Weld Axis	Welder Stands	Effect on the Puddle	Applications
1G (Flat)	Horizontal	Horizontal	Above the plate	Puddle rests in the groove	Shop fabrication, machine bases
2G (Horizontal)	Vertical	Horizontal	Beside the plate	Puddle sags toward the lower toe	Frames, tanks, railing
3G (Vertical)	Vertical	Vertical	Beside the plate	Puddle pulled straight down the face	Columns, bridges, pipework
4G (Overhead)	Horizontal	Horizontal	Below the plate	Puddle falls against the work surface	Heavy erection, shipbuilding

Flat and Horizontal: Building the Foundation

In 1G the plate lies flat on a bench and the welder stands over it. The puddle sits where you put it, heat disperses evenly, and travel speed is easy to read. Beginners learn arc length, work angle, and bead placement here without gravity adding a variable. Control a flat bead first; no other position follows.

2G introduces the first real test. The plate stands on edge, but the weld runs horizontally across its face. The puddle behaves much like 1G, only the joint is now vertical, and the added difficulty is that it wanders toward the lower toe, so the torch must be angled to push molten metal back into the groove.

Vertical and Overhead: Gravity Takes Control

3G is the position this article is about, and the change from 2G is the entire point. The plate stands vertical and the weld axis runs vertical, so the seam climbs the face of the plate. The puddle is not merely sagging, it is pulled straight down the joint. The welder must hold a small, well-shaped pool, control travel speed so the pool neither freezes nor floods, and manage the fact that the plate keeps heating as the pass climbs. Welding and Welder’s position breakdown notes the technique shift between flat work and vertical groove welds.

4G puts the welder under a horizontal plate with the torch pointing up. The molten pool wants to fall straight down, away from the joint, so feathering technique and fast, controlled travel keep it pinned against the work. Many shop welders call 4G the position they like least: the body position is miserable and heat and fume rise into your face. Why stick welding remains popular in the field is partly about this, since SMAW handles vertical and overhead work in ways few other processes can match.

Why 2G and 3G Are Not the Same Test

Beginners often assume 2G and 3G are near-identical because both use standing plate. They are not. In 2G the weld axis is horizontal, so the welder reads the puddle across the joint in a natural side-to-side stance; in 3G the plate is turned a quarter turn and the seam runs up the face, changing travel speed, electrode angle, body position, and heat build-up. A welder who lays a clean 2G bead may still fail 3G on the first pass, because the pool runs down the plate instead of across it.

The Skill Ladder and the “Harder Qualifies Easier” Rule

Positions are taught in order of difficulty: 1G, 2G, 3G, then 4G. Flat and horizontal build technique, while vertical and overhead demand puddle control, heat management, and stamina, which is why 3G is the bridge between intermediate and advanced welding. Holding a consistent uphill vertical groove bead proves a welder can manage a moving pool and control heat input without watching the joint. Qualification rules mirror that ladder: under AWS D1.1 logic, a harder position qualifies you for easier ones, so a 3G test plus a 4G test clears a welder for all four plate groove positions, while passing 1G alone does not. AWS discusses the reasoning behind position-based qualification ranges in this forum discussion on welding position qualification.

Vertical Up or Vertical Down? Progression Inside the 3G Position

Here is a distinction that catches nearly every beginner taking a plate test. The “3” in 3G describes the orientation of the joint, not the direction of travel. A 3G coupon can be welded bottom up or top down, and those are two different qualifications sharing one plate orientation.

Ask any foreman or testing agency what “3G” means and you will usually hear one answer: vertical-uphill, the default in structural steel. But when a procedure or an electrode data sheet calls out vertical progression, it is telling you which travel direction your welder must be qualified to perform.

Vertical-Uphill: The Structural Standard

Vertical-up means you start at the bottom of the joint and climb, letting the puddle climb ahead of you. Because gravity assists the molten pool instead of fighting it, the puddle has more time to wet out into the prepared groove and fuse against the sidewalls. That means deeper penetration, more consistent root reinforcement, and fewer cold-lap or lack-of-fusion defects at the groove toes. The effect is strongest in shielded metal arc welding and flux-cored arc welding, where slower travel gives the puddle time to flow. AWS welding forum discussions echo the shop reality: uphill groove welds look and test better, so structural specifications call for them.

The trade-off is heat. Uphill welding deposits more heat per unit length than the same procedure run downhill, because the arc is slower and the electrode dwells longer over the joint. AWS D1.1 treats this as a real variable, so a 3G vertical-up test qualifies vertical-up production work, while vertical-down is considered separately and addressed only when the welding procedure specification calls for it.

Vertical-Downhill: Faster, Shallower, Thinner

Vertical-down means you start at the top and push the bead downward, with gravity helping molten metal fall into place. The advantages are speed and control: travel is faster, the puddle stays smaller, and heat builds up less in the plate, which suits thin material and repetitive work where cycle time matters.

Downhill also changes metallurgy and geometry. Penetration is shallower because the arc is pushed ahead of a falling puddle rather than working into a rising one, so it is rarely right for a structural groove weld that depends on root fusion for load. It shines in short-circuit GMAW on sheet metal fillets, where fast travel keeps heat and distortion manageable in thin-gauge fabrication.

If you are considering downhill vertical work, the advantages of stick welding still apply, but the technique changes enough to deserve its own practice plate instead of assuming uphill skill transfers.

Factor	Vertical-Up	Vertical-Down
Travel speed	Slower	Faster
Root and sidewall fusion	Excellent	Shallower, risk of lack of fusion
Heat input	Relatively high	Lower
Pool control	Must restrain the puddle	Gravity assists the puddle
Typical use	Structural groove welds, pressure work	Thin sheet, short-circuit GMAW fillets
Best suited material	Thicker plate and groove detail	Light gauge, thin wall
Impact toughness	Can be lower at higher heat input	Generally better

One Test Does Not Cover the Other

A welder who passes a 3G coupon traveling uphill is not automatically qualified to weld vertical-down. The two directions produce different heat input, penetration, and joint geometry, so qualification codes treat them as separate variables.

ASME Section IX handles it this way. The commentary to QW-405.2 spells out the logic: a vertical-uphill progression coupon, such as 3G, 5G, or 6G, qualifies a welder for all positions because uphill is the most demanding orientation in each of those groups. The converse is not true, so a change from any position to vertical-uphill progression requires requalification. In practice, a flat test does not buy you vertical-uphill, but a vertical-uphill test does buy you flat. The ISO 6947 reference and the federal welding safety and qualification guidance reflect the same logic in slightly different labeling.

That asymmetry also explains a testing phenomenon. ASME commentary notes that vertical-uphill welding produces relatively high heat input, which can result in lower impact toughness than other progressions. To compensate, toughness qualification is written so an uphill coupon covers all positions.

What to Ask Before You Weld

Before a test day or a production assignment, put three questions in writing. First, what is the qualified progression: up or down? Second, may the coupon be welded with a backing strip, or must it be backgouged? Third, does the qualification range cover the thickness and the joint you intend to weld in production?

Those answers eliminate most test-day failures. A welder who practices only uphill, then signs a WPS calling for vertical-down on 6 mm plate, has already lost the test before the arc is struck. Get the answers first, then rehearse that progression on a practice coupon until it feels automatic.

3G in Welder Qualification and Certification

Ask a shop owner, an instructor, or a pipeline foreman which test separates a hobbyist from a hireable welder, and the answer is usually the 3G. A plate coupon stood on edge forces the welder to manage heat, travel speed, and puddle placement while gravity pulls molten metal straight down. Those are the problems you meet on a structural column or a pressure vessel shell. So understanding what is 3G welding in certification means knowing the test and what passing it earns you.

Two different kinds of qualification

Beginners routinely mix up two very different things.

• Procedure qualification (PQR / WPS). This tests the recipe, not the person. It proves that a combination of joint geometry, filler metal, position, amperage, voltage, and travel speed produces a code-compliant weld. The finished document is a Welding Procedure Specification that tells the shop what to set the machine to. See the AWS B2.1 vertical-uphill SMAW specification for E6010 and E7018 for a published vertical-uphill example.
• Welder performance qualification (WPQ). This tests the welder. You weld an unfamiliar coupon in a stated position with a stated process and filler metal. Pass, and the paperwork says you are qualified to make welds in that position with that process and electrode. That credential travels with you to a job site. Training programs explain the two-track structure in their welding course material on qualification and certification.

What the 3G test coupon actually looks like

A typical AWS D1.1 3G test is a carbon steel plate coupon stood on edge in a jig or against a back plate. Plates commonly run about 3/8 in. (10 mm) thick with a single-V or single-J bevel, a root opening near 1/8 in. (3 mm), and often a 3/8 in. backing bar so the root pass can be run without backgouging. Root passes commonly use a 1/8 in. E6010 keyhole technique, then fill and cap with E7018. A common fill-and-cap setup is E7018 at 3/32 in. and 1/8 in., DCRP, about 70 to 110 amps at 2 to 7 inches per minute. See our all-position welding rod guide and advantages of stick welding for electrode selection and why SMAW dominates testing.

Acceptance criteria: what the inspector looks for

Visual inspection comes first, and the thresholds are strict enough that one pass of the grinder can ruin a good coupon.

Criterion	Typical AWS D1.1 3G test plate requirement
Cracks	Any crack of any length is unacceptable
Craters	Filled to full cross section, no concave dips
Reinforcement	Shall not exceed 0.125 in. (3 mm) above the surface
Undercut	Shall not exceed 0.031 in. (1/32 in.)
Bend test	Bent 180 degrees; cracking limited to the allowance in weld metal and HAZ
Radiography	Required in some nuclear, pressure, and pipeline programs instead of bend tests

Bend specimens are cut from the coupon and bent with the weld root on the outside. A face bend and a root bend both have to survive, which is why cutout location and slag removal matter. Radiography and ultrasonic testing substitute for bend tests where the code requires nondestructive examination.

What one 3G test actually qualifies you to weld

Per the AWS D1.1 qualification tables, a 3G groove test qualifies a welder for flat, horizontal, and vertical positions, covers unlimited thickness for groove welds when the coupon uses backing or backgouging, and covers pipe groove welds on material 24 in. OD and larger. Because a 3G coupon is vertical uphill, it is the strongest single plate test short of adding overhead.

That is why the 3G + 4G combination is so common. The 3G covers everything except overhead; add a 4G overhead groove test and you hold an all-position groove qualification. See this welding positions and qualification chart for the qualifying tables, and our aerospace welding standards and careers guide for how ASME Section IX governs qualification in regulated industries.

The practical takeaway: a 3G ticket is the most transferable paper a new welder can own. Hold one already? Add the 4G to make it all-position. Do not have one? The coupon in front of you is proof you can control molten steel when the world tilts.

How to Weld 3G: Technique, Settings, and Pass Sequence

3G is two plates welded on edge, and the position rewards method over talent: control the puddle, hold a steady arc, clean between passes, and you can pass with electrodes beginners already own.

1. Prep and Tacking

• Bevel the edges. Single V-groove is standard for SMAW: a 37.5-degree included bevel (16 to 20 degrees per side) on 1/4 inch and thicker keeps the electrode off the sidewalls. Grind off mill scale, rust, paint, and moisture around the joint; water and oil cause porosity.
• Set the root gap. About 1/8 inch (3 mm) on a 1/4-inch coupon. Too tight burns through, too wide gives inconsistent root fusion. Thin material: smaller gap or a backing bar behind the root, which supports the pool.
• Fit up square. Straightedge across the joint, square on the face. A crooked fit forces a travel-angle change mid-seam, and undercut starts.

Tack in the position you will weld, then leave the coupon alone once it is upright: moving it disturbs fit-up, distorts the joint, and can invalidate the test. Tack on the root gap, then chip and brush every tack, since slag under a pass becomes an inclusion that fails a bend test.

Aluminum is a different animal, so read our guide to prepping aluminum correctly before you put a grinder on that joint.

2. Electrode Choice and Current Settings

E7018 and E6010 are the go-to consumables for vertical-up steel. E7018 is the low-hydrogen workhorse; E6010 freezes fast, with deep penetration and a forgiving root bead. Ranges: 70 to 100 amps on a 3/32-inch E7018, 90 to 130 amps on a 1/8-inch E7018. E6010 sits lower in the same diameters, since its coating gives a faster melt rate and concentrated arc.

Start mid-range, weld a few inches, then adjust: a small, sluggish puddle means add amps, a puddle that runs and spits means back off. Confirm settings against your electrode chart and the WPS.

3. Arc Length and Angles

• Arc length should roughly match the electrode core diameter, about 1/8 inch on a 1/8-inch rod. A long arc widens the puddle, spreads the heat, and invites undercut.
• Work angle stays at 90 degrees to the plate. Tilt the electrode and arc force pushes the puddle sideways.
• Travel angle gets a slight 5 to 10 degree upward push so the puddle climbs instead of running down.

As the seam climbs, bend your knees and drop your hips so your arm stays comfortable, not reaching overhead.

4. Root, Hot, Fill, and Cover Passes

Root pass with a 3/32-inch E6010: hold a slight upward push and a short arc. The whip or keyhole technique opens a keyhole in the joint, then drags back and up to fill: deeper penetration, harder control. The straight-up technique lays the electrode in the groove and lets the puddle fill ahead of you, slower but easier to control.

Then chip and brush the joint and run a hot pass (wash pass) to remove root defects, slag, and spatter before adding filler on top.

Fill passes are stringers or a weave. Stringers are single beads straight up the joint: easier to control and less prone to undercut. A weave (Z-weave or figure-eight) washes the puddle toward both toes of the groove, but adds heat and encourages undercut if you linger at the edges. Pull the arc to the edge you want to wet, hold long enough to wet the toe, then move across.

Aim the cover pass for a slightly convex profile with about 1/16 inch (1.5 mm) reinforcement and smooth, well-tied toes. A flat or concave cover bead is a common rejection reason.

5. Cleaning, Preheat, and Travel Speed

Chip the slag and wire brush the bead between every pass: trapped slag becomes an inclusion that radiography finds and a bend test cracks. Cold plate pulls heat from the puddle, so the root may not fuse. Preheating slows cooling, helps slag float off, and cuts hydrogen cracking risk in restrained joints. Interpass limits in your WPS are not suggestions; exceeding them causes delayed cracking.

Travel speed is the most abused variable. Too fast gives a narrow, cold bead that drags the sidewalls and cuts undercut; too slow grows the puddle into a lumpy bead with burn-through, overlap, and overheated plate. Vertical-up stringers on 1/4-inch material typically run 2 to 4 inches per minute, but your WPS number rules. Keep the same bead shape for the pass; if the bead grows, stop, let it freeze, and restart faster or at lower amperage.

Before the arc, read the advantages of stick welding reference and confirm electrode, polarity, and settings against the WPS. See also our all-position welding rod guide. Then tack, root, hot pass, fill, and cover.

Common 3G Defects and How to Troubleshoot Them

Vertical groove welding fails in ways flat welding rarely does. Gravity, rising heat, and a narrow column of molten metal produce a specific family of defects, and nearly all trace back to one problem: the puddle wants to fall, and the sidewalls are the only thing holding it in.

Undercut: the number one test-killer

Undercut is a groove melted into the base metal along the sidewall of the joint. Inspectors look for it first, and it appears with unusual regularity in vertical work. Three causes: travel speed so fast the arc never dwells on the sidewall; an electrode angle aimed at the pool instead of into the joint, starving the toes; and an arc that lingers on the sidewall and burns a channel into it.

Overlap, roping, and lack of fusion at the toes

Overlap is molten metal rolling over the top of the bead without fusing beside it, giving a lumpy, rippled, rope-like surface. It comes from welding straight up the joint with no side-to-side manipulation, so the puddle stacks in the center and leaves the toes unfilled. Lack of fusion is the opposite failure: the weld metal never melted into the base metal at the edges, leaving a sharp unfused line along the toe that usually shows up right after the bend test, when the specimen cracks along the toe or fillet legs. The cause is a puddle that never reached the edges, or travel speed so high that the arc runs along the seam instead of into the joint.

Both respond to the same fix: a controlled weave or stringer motion with pauses at the extreme edges of the toe, slower travel, and the arc held slightly inward a beat longer. A slightly wider bead spreads heat over more of the joint width.

Slag inclusions

Slag inclusions are pockets of solidified flux trapped inside the weld metal. Slag is a normal byproduct of SMAW, and in vertical work it is easy to leave behind: dark, rough spots in the bead, and discrete dark indications under radiography. The classic cause is poor interpass cleaning, since a hot pass welded over a slag-covered surface traps the slag in the joint. Trapped slag also drives hot cracking by breaking the continuity of the weld metal. Chip and brush every pass before welding over it, and keep the pass from running so hot that slag flows back into the puddle.

Porosity, restarts, and cracking

Porosity is gas trapped in the weld metal: small pits on the surface of a vertical bead, round indications under radiography or ultrasonic testing. It is commonly caused by contamination on the joint surfaces or improper shielding. Rust, paint, oil, moisture, and even a damp welding glove dragged across the puddle feed it, and so does a long arc, which lets the atmosphere in as the shielding breaks down.

Porosity at restarts deserves special mention. Break the arc and the electrode tip loses its shielding while a new arc is struck, and that startup is where the atmosphere gets in, which is why a small cluster of porosity at the tie-in is so common. Keep the arc length short, restart deliberately rather than stabbing, and clean the crater and surrounding metal first.

Cracking points to a different family of causes: hydrogen embrittlement or thermal stress. A low-hydrogen electrode such as E7018 and preheat on thicker material are the standard mitigations, and the AWS D1.1 example WPS for vertical uphill SMAW shows how tightly preheat, electrode, and heat input ranges are controlled.

Excessive reinforcement, burn-through, and cold lap

• Excessive reinforcement means the cap is too tall or proud of the plate, usually from low travel speed, too much heat in the center of the joint, or a weave that lingers in the middle. It fails inspection for profile.
• Burn-through on the root happens when the pool is too hot or too large, or the root gap is too wide and unsupported. Vertical position makes it worse, because molten root metal has a long way to fall. Look for a blown-out hole in the root, sagging, and metal dripping onto the back of the plate. Reduce amperage, keep the arc on the leading edge, close the root gap, and use a backing strip or slower travel until the root pass is done.
• Cold lap is molten metal laid onto a surface already solidifying or too cold to melt. It shows at the start of a pass, where the puddle touches the sidewall before the base metal melts. The bead looks smooth but is sitting on the surface, and it usually fails a bend test. Dwell the arc on the starting point until the base metal melts, and keep interpass temperature high enough that the previous pass is still hot.

Root pass problems and heat buildup

The root pass is where most failures begin: blowouts, burn-through, and insufficient penetration, especially when the welder rushes before the plate cools. Heat buildup is the quiet problem tying the section together. As the coupon climbs, the plate gets hotter with every pass, the torch angle drifts as body position changes, and by the cover pass the puddle is more fluid and the plate may be distorting. Watch interpass temperature, keep a consistent work angle by moving your body, and slow down as the plate heats. A tacked test coupon cannot be moved once welding begins, so you cannot rotate the problem away.

How defects are caught

Nearly all of these defects are found in the same order. Visual inspection comes first: undercut, overlap, lack of fusion, excessive reinforcement, porosity, cracks, and cold lap are all visible to a trained eye, and the guide to welding positions, techniques and defects shows what each one looks like in practice. Then come the mechanical tests: face and root bend specimens are machined from the coupon and bent to reveal lack of fusion, slag, and cracking. A bend test fails long before a radiograph would catch the same flaw, which is why it remains the standard acceptance method for 3G qualification in structural work. Radiography and ultrasonic testing come next, and they are what pipeline and pressure applications rely on. Radiography reveals internal porosity, slag, and lack of fusion that the surface conceals. Ultrasonic testing finds the same flaws in thick plate with less radiation exposure, though it is harder to run on a vertical joint with irregular surfaces.

Defect	Cause	Fix
Undercut	Fast travel, wrong angle	Slow down, aim into the joint
Overlap / roping	No manipulation	Weave, dwell at the edges
Lack of fusion	Puddle misses sidewalls	More edge dwell, slower travel
Slag inclusions	Poor interpass cleaning	Chip and brush every pass
Porosity	Contamination, long arc	Clean joint, keep arc short
Porosity at restarts	Arc broken	Clean crater, restart deliberately
Excess reinforcement	Slow travel, center heat	More travel, spread the weave
Burn-through	Hot, unsupported root	Lower amps, close the gap
Cold lap	Base metal not melted	Hold the arc on the start
Cracking	Hydrogen, thermal stress	E7018, preheat thicker material

Every defect on this list is visible while you are welding it. Welders who fail 3G tests repeatedly are rarely the ones who cannot see the problem; they are the ones who saw it on pass three and kept going anyway. For background on why vertical work differs from every other position, see what the four basic welding positions are and when to use them, and for electrode behavior as the arc angle changes, read the all-position welding rod guide.

3G vs. 3F, 5G, 6G, and Other Positions: What Each Test Qualifies

Ask five welders what their ticket covers and you get five answers, because most know only one test. The 3G coupon is structural steel’s workhorse, yet it is neither every weld a shop runs nor every site that hires on a ticket. Mapping the codes prevents expensive do-overs: paying a welder to re-test for a position he was never qualified in, or turning down a contract because nobody holds the right paper. The basics of the four plate positions are worth revisiting first.

3G vs. 3F: Same Orientation, Different Joint

Both tests use standing plate. The difference is what you are joining. 3G is a groove (butt) weld on a vertical plate with the weld axis running up the face. 3F is a vertical-up fillet weld in the corner of a T-joint, one plate lying flat and the other upright.

Most welders find 3F more forgiving, and the geometry explains why: the horizontal lower member forms a shelf under the puddle, so molten metal has somewhere to sit while it cools. In 3G you hold that same pool against a vertical sidewall with gravity pulling straight down it.

Here is the catch: the easier test does not buy more ground. Under AWS D1.1 and ASME Section IX, a 3F coupon qualifies the welder for all fillet positions (1F, 2F, 3F, 4F), but a groove ticket does not carry fillet work with it. Groove and fillet are separate tracks, so a shop running structural fillets still needs a fillet test on file. The aluminium welding course overview shows how codes differ by material and process.

3G vs. 5G: Plate Coupon and Fixed Pipe

The 5G test uses a pipe coupon. The pipe stays fixed horizontally, the welder stays put, and the torch travels around one full circumference. As the bead runs from the bottom of the pipe up the side and over the top, it passes through flat, vertical and overhead orientations inside one coupon. That is why a 5G covers flat, vertical and overhead pipe positions with no separate overhead coupon.

But a 5G is a pipe qualification. It does not hand you a plate ticket, and a 3G plate ticket does not automatically make you a pipe welder, because thickness limits, diameter limits and joint details attached to each coupon are specific. The case for SMAW explains why so many of these tests are run with stick welding in the first place.

3G vs. 6G: The Toughest Common Qualification

The 6G coupon takes that same fixed pipe and tilts it to 45 degrees. The welder completes one circumference that starts vertical-up, rolls through overhead and finishes vertical-down in a single continuous weld. No reposing, no crutching the pipe halfway through. It is the most versatile single pipe test available, and it is what pipeline and pressure-work employers ask to see.

One limit applies across the pipe family: qualification coupons are generally bounded at 24 in. OD in the mainstream codes. Above that diameter, expect extra qualification handling rather than assuming a 5G or 6G ticket transfers across. AWS and ASME track this through position and progression variables, and the NCFFA welder certification reference tabulates the ranges.

What Each Test Actually Qualifies

Test	Coupon Setup	Positions Qualified
1G	Plate flat, welder above	Flat only (1G)
2G	Plate vertical, axis horizontal	1G and 2G
3G	Plate vertical, axis up	1G, 2G and 3G
4G	Plate flat, welder below	1G and 4G
3G + 4G	Two plate coupons	All plate groove positions
3F	Vertical fillet on a T-joint	All fillet positions: 1F, 2F, 3F, 4F
5G	Pipe fixed horizontally	All pipe positions: flat, vertical, overhead
6G	Pipe fixed at 45 degrees	All pipe positions; most versatile single test

One ASME rule catches people out. A vertical-uphill coupon is a broad qualification: pass 3G uphill (or 6G) and you are covered for all positions. A flat coupon is not. Passing 1G alone buys flat and nothing more, which is why test programs push candidates toward 3G or 3G+4G. The positions chart reference keeps this table straight at the bench.

Which test a shop cares about comes down to the work. Structural steel fabricators live on 3G and 3G+4G, since field erection means welding a beam that is standing up. Pipeline and heavy pressure work points to 6G. Stairs, handrails and platform shops lean on 3F and 3G, and aerospace primes often ask for 6G-style pipe coupons even on aluminum work, where filler and oxide control dominate; the aerospace welding guide covers that.

Mistakes Beginners Make in 3G (and How to Fix Them)

Most 3G failures have nothing to do with metallurgy. A welder treats a vertical plate like a flat plate that is standing up: the puddle behaves differently, the heat goes somewhere else, and flat-position habits suddenly cost points on the coupon. These mistakes are fixable with preparation, not talent.

The Panic Speed-Up

The plate heats up mid-fill, the welder speeds up, and the bead goes narrow, stacked, and ragged. The instinct is wrong: slow down and let the plate warm, because heat input controls the puddle. Set a rhythm first, with fixed bead length, fixed inches per fill pass, and a pause between passes to check.

Too Much Amperage on the Root

Beginners crank amperage because the root bead looked thin, so it burns through and leaves a lumpy underside. Geometry comes from the WPS: on the standard 3G carbon steel coupon described in the AWS B2.1 / D1.1 practice materials, expect 3/8 in. plate at a 45-degree included angle, a 1/4 in. root gap, and a backing plate 1/4 in. or 3/8 in. thick and at least 3 in. wide, with preheat at 50°F minimum. Undercut is usually a travel speed and angle problem, not an amperage problem.

Moving the Coupon After Tack

Unbolt the plate to see the joint, tip it back, and the test is over before you start. Test procedures are explicit: once the test weld is placed in the 3G position, the coupon shall not be removed until the weld is completed. Plan the fit-up before you tack. If the joint sits above your working height, use a welding table, a tilting fixture, or a block under the plate, never a hammer.

Slag Left Between Passes

Beginners grind the root but skip interpass cleaning on fill passes, then weld slag into the joint, and inspections find the inclusions. Chip and brush every pass, including the toe of the previous bead, before restarting. A wire brush and hammer are enough; stubborn slag needs a light grind back to bright metal.

Craters at the End of the Rod

Every rod end in a vertical-up bead leaves a crater unless you fill it, and beginners either stop the arc dead and leave a hole or back out and leave a porous taper. At the end of a bead, stop forward travel, hold the arc, feed filler to fill the depression, then break the arc quickly and drag the electrode upward to break the surface tension.

Letting the Torch Angle Drift

Start at the bottom with a good work angle, then lean in and around as the bead climbs until the electrode pushes the arc instead of striking into the joint, and the bead pinches, undersides, and undercuts. Keep the work angle near 90 degrees with a slight upward push, holding it for the whole bead by shifting your feet, not reaching.

Guessing Instead of Reading the WPS

A machine set by feel will not do on a coupon with a specified root gap, angle, and pass sequence. Read the procedure before you light the torch, then again between passes: amperage range, voltage, travel speed, electrode, preheat, and interpass temperature. If the WPS lists an interpass maximum, treat it as a real limit, because stacking passes on hot steel gives a failed bend specimen.

Practicing Only Flat

Most shop time is flat and horizontal, so 3G skill does not develop on its own. Practice deliberately on cheap material. Mark a practice plate with chalk before welding, then compare the bead to the line afterward: the mark shows whether you drifted off the joint. An all-position welding rod guide covers how rods behave as they heat up and why vertical-up needs a different hand position.

Self-Inspection With a Mirror and Flashlight

Do not judge a finished pass from the front. Hold a flashlight at a low angle across the bead so ripples and undercuts pop, and use a small mirror to check the root bead and toes before you cover them. It is the cheapest quality control available.

Rod Count Planning

Running out of rod mid-fill-pass means grinding a hot weld to restart cold and losing your rhythm. Estimate rods per pass and stage them in reach, kept dry in a rod oven or heater. The practical advantages of stick welding are worth reviewing, since SMAW handles outdoor and in-position work other processes cannot.

Pre-Test Checklist

None of these fixes are exotic. They are preparation, and they separate welders who qualify on the third attempt from those who never do. For position codes and qualification ranges, see the welding positions reference chart and Miller’s overview of the four basic welding positions.

Safety, Inspection, and Real-World Use of 3G Welding

When the arc points up on a 3G coupon, gravity sends molten spatter, slag, and stray sparks straight down the front of your body, into the crook of your elbows and onto your forearms. Test coupons are usually bare plate with no mill scale protection, so they spit, and a raised hood with full leather sleeves is the difference between a good day and a burn.

The Spatter Problem Nobody Warns You About

• Long gauntlet leather sleeves and gloves are the minimum for vertical work, not short cuffs.
• Raise the hood properly and look through the lens; tilting the helmet back to see leaves your face open to falling slag.
• Wear flame-resistant clothing under the leathers. Cotton burns, and a molten glob burns through in a second.
• Cover your boots in closed leather footwear and keep leather dry and hole-free; many shops require metatarsal guards for vertical and overhead work.

Fumes, Ventilation, and Your Lungs

In 3G you often lean over a hot plate, so the fume plume rises right in your face. As the coupon heats through successive passes, fume generation climbs, and that is when concentration and pass quality slip.

OSHA’s welding, cutting, and brazing standard, 29 CFR 1910.252 sets the baseline: ventilation to control fume, protection from fumes and gases, and hot work controls including fire prevention. The CDC/NIOSH welding fume topic page calls welding fume a leading occupational health concern, with manganese among the metals of concern for neurological effects from chronic exposure. On stainless and other chrome-bearing alloys, hexavalent chromium is a recognized carcinogen that demands local exhaust.

• Use local exhaust ventilation: a fume extractor with a hood near the arc, or a positioned exhaust fan.
• Never weld in a confined space or poorly ventilated booth without a plan. Welding gases and shielding setups matter because gas flow affects fume and porosity.
• Wear the right respirator when ventilation is inadequate, and know your material: stainless and galvanized steel change the fume profile.

Fire Control and Ergonomics

Vertical 3G work happens amid combustible material: wood cribbing, cardboard, rags, other coupons. OSHA hot work rules mean a permit system, a fire watch, and a clear zone. Keep a fire blanket behind the plate near anything flammable, and never weld over solvent or a parts washer.

A coupon at chest to shoulder height means welding upward and reaching, which strains shoulders and neck, tires the lower back from twisting to follow the rising bead, and locks the wrist at a locked-out torch angle. Counter it by lowering the plate, keeping the bead near your mid-torso, and adjusting your stance as the seam rises. A coupon table with the right height and clamp system, as described in this guide to welding positions and safety considerations, saves shoulders on every test.

Inspection: What Actually Gets Checked

Passing the coupon is only the first gate. Many employers follow qualification with destructive or nondestructive examination, and the same logic applies to production 3G welds. Under AWS D1.1, Clause 4.9.1.1, groove welds get visual inspection before any other examination method is applied, and visual is the cheapest, fastest way to catch the defects that cause the most trouble: cracks, unacceptable concavity, overdeep undercuts, overlap, excessive reinforcement, visible porosity, and unfilled craters at rod ends.

Method	What it reveals	Why it matters in 3G
Visual (VT)	Surface profile, undercut, cracks, porosity, crater fill	First-line check per D1.1 4.9.1.1
Bend test	Root and face fusion, penetration	Standard for qualification coupons; exposes lack of fusion and slag
Radiography (RT)	Internal porosity, inclusions, cracks	Critical pipe and pressure joints
Ultrasonic testing (UT)	Internal flaws, delamination, lack of fusion	Faster field alternative to RT on thick plate

Bend specimens are cut from the coupon, usually one root bend and one face bend, then bent to a specified radius. A clean bend means the weld went all the way through, fused to the sidewalls, and carries no trapped slag. Inspectors look hardest at the 3G root pass, because vertical-uphill welding concentrates heat in a narrow column of metal and root defects hide well. See the AWS forum discussion on welding positions and the NCFFA welder certification overview for how positions map to qualification requirements.

Where 3G Welding Actually Gets Used

3G is not a test-only exercise. Vertical-uphill groove welding shows up in building frame erection, where a column or beam flange meets a base plate or stiffener, and in bridge and highway structures, tank and silo work, heavy equipment and crawler fabrication, and pressure piping and tanks where the joint orientation is fixed by vessel geometry. Many structural shops qualify welders in 3G and 3G plus 4G because that is the work they do, while pipeline contractors tend to demand 6G-level pipe qualifications, since a fixed 45-degree pipe is the harder geometry. ISO 6947 equivalents matter on imported drawings and mixed crews, and the ISO 6947 standard document sets out the numbering that mirrors the AWS system.

Conclusion

So what is 3G welding? A groove weld on plate held vertically with the weld axis running up, coded in the AWS position system where 3 means vertical and G means groove. It is one of the four plate groove positions and one of the hardest, because gravity fights the molten pool on every pass. It is also the qualification most shops care about: holding a consistent uphill bead proves control of heat, travel speed, and torch angle that translates into structural work, heavy fabrication, and repair. Qualified 3G plus 4G opens the widest range of work a shop will let you take, so test at a lab qualified to AWS D1.1 or ASME Section IX and plan to add 4G.

Frequently Asked Questions

What does 3G mean in welding?

3G means a groove weld made in the vertical position on plate: the number 3 indicates the vertical position and G indicates a groove weld. It is defined by the AWS position designation system and appears on WPS documents, filler metal data sheets, and welder qualification tests.

Is 3G welding done uphill or downhill?

Either, but structural 3G groove welds are almost always run uphill (vertical-up) because it gives better root fusion and sidewall wash-in. Direction of travel, called progression, is tracked separately from position, so a welder qualified 3G-up is not automatically qualified 3G-down.

What does a 3G welder test qualify me for?

Under AWS D1.1, a 3G groove test with backing or backgouging generally qualifies a welder for flat, horizontal, and vertical plate groove welding, unlimited thickness, and pipe groove welds 24 inches OD and larger. Adding a 4G overhead test clears you for all plate positions.

How is 3G different from 3F?

Both are vertical, but 3G is a groove weld in a beveled joint between two plates, while 3F is a fillet weld in a corner or T-joint. The lower member of a fillet joint supports the puddle, which generally makes 3F easier than 3G.

How is 3G different from 5G and 6G pipe welding?

3G is flat-plate welding on a vertical joint. 5G is a fixed horizontal pipe weld where you pass through flat, vertical, and overhead around one circumference, and 6G is a pipe fixed at a 45-degree angle. Both pipe tests are more demanding and qualify broader ranges.

Which electrodes are most common for a 3G test?

The classic combination is E6010 for the root and hot pass followed by E7018 for fill and cover, run on DC reverse polarity. Many test procedures use E7018 alone for the entire weld, especially on 3/8 in. coupon thickness.

What is the hardest part of welding 3G?

Controlling the puddle as gravity pulls it downward while keeping the toes washed in without creating undercut. Most failures come from cover-pass undercut, ropey beads from going straight up with no manipulation, and slag inclusions from poor interpass cleaning.

What are typical acceptance criteria for a 3G test plate?

No cracks are permitted, craters must be filled to full cross-section, weld reinforcement must not exceed 0.125 in., and undercut must not exceed 0.031 in. (1/32 in.). After visual inspection the plate is typically cut and bend-tested or radiographed.

Is 3G considered hard for beginners?

Yes, it is the position where most beginners hit a wall because it is the first time gravity works against the pool. With proper amperage reduction, controlled travel speed, and consistent manipulation, most students produce sound vertical-up welds within a few weeks of focused practice.