Flux Core Welding Pattern: Stringer vs Weave Techniques

There is a moment in every flux core job when the bead stops looking like a weld and starts looking like a lump. The arc is running, the wire is feeding, the slag chips off on schedule — and yet the crown is fat, the toes are undercut, and the inspector keeps circling back for a third look. Almost always the problem is not the machine or the spool. It is the pattern: the path the torch takes while it deposits metal.

What Is a Flux Core Welding Pattern (and Why It Decides Weld Quality)

If you searched “flux core welding pattern” and came away with a vague idea of “moving the torch side to side,” it is worth pinning the definition down first, because everything else in this article hangs off it.

A welding pattern is the path the torch follows while it deposits metal. Two things are happening at once: travel along the joint, and whatever side-to-side motion the welder adds on top of that travel. Every manual arc process has patterns, but only two broad families. Stringer beads are made with very little side-to-side motion, so the torch walks the joint almost straight. Weave beads superimpose a deliberate side-to-side motion on forward travel so the arc covers a wider band. Everything else you will read about triangles, crescents and Z-weaves is a variation on the weave side of that family, and you can see the same basic split described in the GMAW and FCAW handbook materials that cover both processes.

Pattern family	What the torch does	Where it earns its keep
Stringer	Travels along the joint with minimal side-to-side motion	Root passes, all overhead work, narrow fillets, multi-pass grooves where deliberate bead placement beats raw width
Weave	Adds side-to-side motion to forward travel to cover a wider band	Cap passes, wide groove coverage, vertical-up fillets where toe fusion needs help

Why the Pattern Matters More in Flux Core Than Anywhere Else

Flux core arc welding uses a tubular electrode with a flux inside its core. Weld metal transfers in globular or spray modes much like GMAW, but the burning flux leaves a protective slag layer over the bead, as the FCAW process overview explains. That slag is the whole reason pattern control is so much more consequential here.

In a clean process, the arc, the puddle and the slag barely compete with one another. In FCAW they are constantly interacting, and the torch path decides where each one goes. Drag the wire at roughly 5–15 degrees from perpendicular, as described in the FCAW techniques material, and the arc sits at the leading edge of the puddle while slag flows behind it. Push the pattern wide and fast, and you sweep slag back into the puddle you are about to cover. The path is not decoration. It is traffic management for heat, metal and slag at the same time.

What Flux Core Arc Welding Actually Is

FCAW was developed in the 1950s, and the breakthrough moment came in 1959 with the first self-shielded flux-cored electrode. Instead of drawing shielding gas from a cylinder, the burning core generated its own protective atmosphere, which freed the process from gas lines entirely. That single change is why flux core took over field welding, pipeline work and outdoor fabrication the way it did, and the history is well covered in the AWS Welding Digest overview of the process.

Two variants came out of it: FCAW-S, self-shielded, and FCAW-G, gas-shielded with an added shielding gas around the arc. The Michigan DOT structural welding field manual makes the practical difference plain: GMAW cannot be used in a windy environment, because loss of the gas shield produces porosity, while FCAW can be run with or without shielding gas. If you are choosing wire for aluminum work, our aluminum flux core welding guide covers how the same slag-forming logic behaves on a very different base metal, and how aluminum flux welding works explains the chemistry behind it.

So Which Pattern Is Right?

There is no single best pattern, and anyone who tells you there is has not welded much code work. The correct pattern is a function of welding position, joint configuration, wire type, the bead width required and the governing welding procedure specification. A wide weave that looks impressive on a flat coupon can be an illegal path inside a procedure written for narrow stringer passes.

On structural and pressure-retaining work, the WPS is the authority rather than any rule of thumb. AWS D1.1/D1.1M:2025 prequalifies FCAW together with GMAW metal-core in Table 5.4, so even a “simple” pattern choice lives inside a documented, qualified procedure.

Stringer Beads: The Most Common Flux Core Welding Pattern

Learn the stringer first if you only learn one pattern for flux core welding. It is the default because it asks the least of your puddle and the most of your hand. The Goodheart-Willcox GMAW/FCAW Handbook defines it as travel along the joint with very little side-to-side motion, made with a small zigzag or a small circular motion, with forward speed varied as needed to maintain an even bead contour and shape.

The wire stays near the middle of the joint and lays down a narrow ribbon of metal. When a flux core bead starts to look like a lump, the stringer is the first pattern to question.

What a Quality Stringer Bead Looks Like

A good stringer is narrow, evenly crowned and consistent. Bead width generally lands around two to three times the wire diameter, the crown is slightly convex rather than flat or humped, and both toes wash in smoothly into the base metal with no undercut groove and no overlap. Even ripple spacing tells you travel speed was steady. Slag peels off cleanly behind the arc instead of breaking over the toe.

Wire diameter	Approximate stringer bead width
0.030 in (0.8 mm)	0.06 to 0.09 in (1.5 to 2.3 mm)
0.035 in (0.9 mm)	0.07 to 0.10 in (1.8 to 2.5 mm)
0.045 in (1.2 mm)	0.09 to 0.13 in (2.3 to 3.3 mm)
1/16 in (1.6 mm)	0.12 to 0.18 in (3.0 to 4.6 mm)

Treat those ranges as a starting reference, not a specification.

Why the Stringer Is the Default

Four reasons push nearly every procedure toward a stringer.

• Arc force stays on the centerline. It is the narrowest bead you can produce for a given wire diameter, which concentrates the arc on the joint and delivers the best penetration-to-width ratio of any pattern.
• The puddle stays small. A narrow puddle is a puddle you can control, and control separates a sound bead from a fat, running one.
• Slag stays behind the arc. Flux core weld metal is slag forming, so the debris needs somewhere to go. Straight travel keeps it behind the torch where you can see it and knock it off. That arc, puddle and slag relationship is the core of the FCAW process overview.
• It is easy to learn and inspect. A narrow bead shows its defects clearly, which matters when a third party has to judge it.

Where Stringer Beads Belong

Stringers show up in most groove welds as the root pass, because a clean, narrow root is easy to verify for cracks and easy to fill over. They are the standard choice for flat and horizontal fillets, and for every overhead weld, where a small pool is the difference between a bead and a drip. They also suit multi-pass work where deliberate placement of each bead matters more than covering width in one pass.

The same straight-travel motion appears in stick welding, where the electrode is dragged up a fillet with no side-to-side movement at all. Why SMAW still wins on many jobs shows how the geometry carries across processes.

Vertical-up is the one position that needs a caveat. Lincoln Electric notes that some self-shielded wire families handle vertical-up stringer beads well, while others require manipulation of the puddle to flatten the weld face. If your wire is fluid and wants to run, an all-position electrode or wire with better vertical characteristics may be the smarter swap. Aluminum flux core wires behave differently again, as covered in aluminum flux core welding.

The Multi-Pass Advantage

Three or four side-by-side stringers beat one wide weave more often than most welders expect. Each pass gives you another chance to chip slag, so interpass cleaning opportunities multiply. The active puddle stays small, and every bead goes exactly where you put it. The price is extra starts, extra stops and extra slag removal, and on a schedule that is real money.

The handbook guidance on horizontal multi-pass groove welds leans the same way: make beads smaller when welding out of position, use stringer beads rather than weave beads for horizontal multi-pass groove work, and hold longitudinal gun angles of 10 to 15 degrees from the perpendicular position. For horizontal fillets it recommends a 45-degree transverse angle on a single pass and different angles for a multi-pass fillet, with the second pass made on the bottom so the finished weld has a slightly convex crown and equal legs.

Weave Patterns Explained: Triangle, Z-Weave, Crescent and Figure-Eight

A weave adds a side-to-side motion to your travel. Instead of running the torch straight along the joint, you lead it across the work and back, and that path is what welders call a weave pattern. Get it right and the bead is wider, better shaped and easier to fill. Get it wrong and you get a lumpy crown, melted toes and slag trapped in the deposit.

Most shops need only three or four of these patterns.

The Triangle Weave

Travel up the centre of the joint, pause briefly on one toe at the top of the weld, cross sideways over the face to the opposite toe, pause there, then come back down to the centre. Repeat, and the torch traces narrow triangles stacked up the joint.

Those pauses are the point: dwelling on a toe holds the arc still long enough for filler metal to wet into the sidewall and fuse. In vertical-up work the toes are where a vertical fillet bead fails first, and the open FCAW textbook from Lake Washington Institute of Technology says to move up the joint in small increments while weaving, stopping momentarily at each toe to prevent undercut.

The Z-Weave or Zigzag

The Z-weave is a continuous side-to-side sweep with no deliberate toe pauses. The torch crosses the centre line quickly and reaches each side more slowly, which is why it reads as a Z rather than a series of Vs. Because it never really stops, it lays heat quickly and evenly across the width, a favourite for cap passes and for filling a wide groove in one pass.

The same textbook notes that a steady push or a Z-weave can be used in the vertical position with uphill travel. The trade-off is less toe fusion, so it suits a wider joint where the centre needs coverage more than the edges need soaking. Many production welders prefer it on cap passes, where appearance matters more than root reinforcement.

The Crescent Weave

The crescent traces a curved, half-moon arc across the joint rather than a sharp zigzag. The torch sweeps in a smooth curve, spreading heat over a wider area and giving a gently convex crown with minimal reinforcement in the middle.

That even distribution is why it works in flat position and on slightly inclined or vertical joints, where a sharp zigzag would concentrate too much heat in one place. If the bead looks like a string of beads or the crown peaks in the middle, the crescent is usually the cure.

The Figure-Eight

The figure-eight weaves alternating loops that cross the centre line: loop on one side, cross the centre, loop on the other. Because the loops overlap, the path deposits extra metal in the middle, but it also redistributes heat smoothly and produces a wide, flat bead with a stable pool.

It shows up most often in pipe work and torch brazing, where a wide, even coverage band across the joint face is wanted without stacking a heavy crown.

Circular and Loop Patterns for Surfacing

Surfacing changes the pattern shape entirely. The circular or loop pattern draws overlapping circles or a continuous spiral so each pass overlaps the last. Used with FCAW hardfacing and cladding wires, it produces an even layer of deposit with good coverage and manageable heat.

The Rhythm of Any Weave

Every weave shares the same rhythm: move promptly through the centre, slow down and pause briefly at the toes, where sidewall fusion has to happen. Keep the pauses short and deliberate, not a stall.

Lincoln Electric’s technique guidance for vertical-up groove welds captures this well: hesitate distinctly at the outer edges of the bevel, travel fairly quickly across the face of the weld, minimise each upward step, do not step up at the edges, and do not weave wider than 3/4 in. (20 mm). Wider joints call for a split weave technique rather than a stretched arc.

For fillets, the same guidance calls for a short side-to-side motion on 1/4 in. welds and a triangular weave on larger welds, with a distinct hesitation at the outer edges for the first pass. Keep the leading motion focused into the root rather than riding on the puddle, and target a first-pass face width of 5/16 to 3/8 in. (8–10 mm). Second and later passes use a side-to-side weave.

Pattern	Shape	Best for
Triangle	Up centre, pause at toes	Vertical-up fillets, root reinforcement
Z-weave	Fast zigzag, no pauses	Cap passes, wide grooves
Crescent	Smooth half-moon sweep	Flat and inclined position
Figure-eight	Loops over the centre line	Pipe work, torch brazing
Circular / loop	Overlapping spiral	Surfacing, cladding, hardfacing

Two Warnings Before You Weave

First, never weave over slag. In a slag-producing process like FCAW, the arc should stay on the active leading pool, and slag left in place gets rolled under and trapped inside the bead. Slag inclusions are a common reason a coded weld gets rejected, so clean every pass before you cover it.

Second, the same path does not behave identically in every process. A weave that runs cleanly in FCAW may behave completely differently in SMAW, GMAW or GTAW, because the balance between arc, puddle and slag changes completely. Slag-free processes fill differently, and a weave width that suits flux core can be far too wide for a short-circuit GMAW bead. Re-learn the width when you switch processes.

New to flux core? Master stringer beads first, then add one pattern at a time on scrap. A repeatable stringer beats a fancy weave you cannot yet control. Match the pattern to the metal as well: the guides on aluminum flux core welding and aluminum MIG welding both come back to the same idea, match the motion to the pool.

Choosing Your Flux Core Welding Pattern by Welding Position

When working with flux core, position is one of the biggest factors that dictates which pattern will actually work. Gravity doesn’t care about how good your hand is on the flat table, and once the molten puddle is out of position, it will pull wherever it’s allowed to. Because of this, the pattern isn’t being chosen for looks, but to fight gravity while still achieving proper fusion. More importantly, changing position doesn’t just mean changing your torch path, it changes the entire operating point. Out of position, you’ll generally want a slightly lower wire feed speed, a tighter arc, a smaller and more controlled pool, and an adjusted travel speed to hold the same bead shape as you would in the flat position.

Flat Position (1G / 1F)

The flat position is the easiest to work in, which makes it the perfect place to build speed and consistency. With gravity holding the puddle in place, you have the highest deposition rates available for flux core. For most joints, a simple stringer bead is the way to go. If you’re running a wider cap or need a slightly smoother crown, a gentle crescent weave can work as well. Regardless of which you choose, keep a steady drag angle between 5–15 degrees and focus more on maintaining a consistent travel speed than on a complicated motion. This is the position to dial in your settings before moving anywhere else.

Horizontal Position (2G / 2F)

Once you rotate to horizontal, gravity immediately starts pulling the molten puddle down towards the lower plate. This is exactly why your pattern has to stay narrow. For fillets, a tight stringer bead is usually your safest bet. If coverage calls for just a little more width, a very slight weave with a deliberate pause at the upper toe is acceptable, but it needs to be restrained.

Aiming is just as important as the pattern here. Try to aim your wire slightly towards the upper plate, and tilt the gun slightly above the horizontal plane to help fight that downward pull. This becomes especially important for multi-pass horizontal fillets. The shelf of previous passes supports the next one, so make your first pass in the root with a stringer, then stack subsequent passes slightly toward the upper plate. Stacking this way allows each new bead to sit on that supported shelf rather than fighting to float on an unsupported, sagging pool.

Vertical-Up Position (3G / 3F)

Vertical-up is where flux core really shines compared to some other processes. The solidified weld metal below creates a natural shelf to support the puddle, and the fast-freeze slag of flux core adds even more support against gravity. To take advantage of this, the go-to pattern is a triangular weave.

Start at the bottom of the joint and travel uphill. As you go, focus on watching the puddle behind the arc, not the bright arc itself. This allows you to react to the shape of the pool instead of guessing. The most critical part of this motion is the pause at each toe. That pause lets the puddle wet into the sidewall, fusing properly instead of rolling over the toes without penetration. Without it, you’ll be left with a ropey bead with little to no sidewall fusion. You’ll also want to drop your wire feed speed and voltage slightly from your flat settings to keep that puddle tight and manageable.

Overhead Position (4G / 4F)

Overhead is the least forgiving position for any puddle, period. There’s nowhere for excess molten metal to go but down, so your number one goal is to keep the pool as small as humanly possible. For this reason, stringer beads only are the recommended pattern for overhead FCAW.

Keep a shortened stick-out to concentrate heat and tighten the arc, maintain a steady travel speed, and do not hesitate. Any unnecessary pause will allow the puddle to grow, and once an overhead puddle gets too large, it will drip. A tight stringer with discipline will always beat any attempt to weave in this position.

Vertical-Down Position (3G/3F Downhill)

Vertical-down travel can be tempting for speed, however, it is not a universal option for flux core. Some self-shielded and gas-shielded wires simply aren’t qualified or recommended for downhill progression, as the puddle can run ahead of the arc far too easily and drastically reduce penetration. Because of this, vertical-down is only acceptable if it’s explicitly allowed by your wire data sheet and your approved WPS. If either of them are silent or say “no”, don’t guess. Speed is never worth sacrificing fusion or code compliance.

At the end of the day, the pattern is never the only thing changing between these positions. Voltage, wire feed speed, contact-tip-to-work distance, and travel speed all need to be tuned to fit them. The trick is remembering that the motion is your tool to control the puddle, not to cover more area. Keep it tight where gravity fights you, and let gravity help you where it can. That’s the difference between a bead that just looks placed, and one that’s fused correctly.

Code Limits: What AWS D1.1 Says About Weld Patterns and WPS Rules

On structural, pressure-retaining, and safety-critical work, the Welding Procedure Specification (WPS) is the authority, not any rule of thumb. Even the cleanest bead can be an illegal one if the motion of your gun falls outside of what was qualified. For flux core welding, your pattern isn’t just a matter of appearance, it can directly impact whether a procedure is still valid under code.

Which Processes Are Prequalifiable?

Under AWS D1.1/D1.1M:2025 Clause 5, there are only four processes that may be prequalified. These are SMAW (Table 5.1), SAW (Table 5.2), GMAW solid wire (Table 5.3), and FCAW plus GMAW metal-core combined (Table 5.4).

There is one hard exclusion to know: GMAW short-circuit transfer is not prequalifiable under any condition. Clause 5.5.1 requires that the mode of transfer not be short circuit for GMAW prequalification, meaning short-circuit applications must go through Clause 6 qualification testing with no exception.

The Tables That Control Prequalification

Prequalification isn’t a blanket pass for any settings. AWS D1.1 lays out strict boundaries for every qualified procedure. The essential variables are found in Table 5.5, base metal groups in Table 5.6, filler metals and shielding gases in Tables 5.7 through 5.10, and minimum preheat and interpass temperatures in Table 5.11.

Most importantly, prequalification is both process-specific and joint-specific. Any joint configuration that does not match the prequalified details within Clause 5.4 requires a qualified WPS under Clause 6, even if every other variable happens to fall within the prequalified limits. This is especially relevant when working with materials that call for the correct selection of alloy steel welding electrodes or specific filler requirements.

When a Pattern Becomes an Essential Variable

Your weave, stringer choice, position, and joint detail all live inside these prequalified boundaries. For this reason, the welding pattern can become an essential variable question. Changing from a self-shielded to a gas-shielded wire changes the filler classification and therefore the procedure entirely. An unauthorized weave, an unapproved wire switch, or going outside of a prequalified joint detail can all invalidate prequalification and push the job into Clause 6 qualification testing.

Testing, Qualification, and Acceptance

Prequalified status only exempts the procedure from Clause 6 procedure qualification testing. The welder must still be qualified separately under Clause 6 Part C, regardless of whether the WPS is prequalified. On top of that, every production weld must still meet the visual acceptance criteria of Table 8.1.

With that being said, a visually pleasing pattern means nothing if it does not meet size, profile, undercut, or any other acceptance criteria listed within Table 8.1. The code does not care how smooth your weave looks, it cares if it is sound, within profile, and made under an authorized procedure by a qualified welder.

On any code-governed job, your WPS will always trump any “shop rule of thumb”. The pattern is a tool to meet that WPS, not something to freestyle past it.

Wire Type Changes the Pattern: FCAW-S vs FCAW-G

Swap the spool and the same pattern lays down a different bead. A welding pattern is a relationship between three things: the arc, the puddle and the slag. Self-shielded and gas-shielded flux core wire balance those three differently, so drag angle, stick-out and the travel speed you can hold all shift. The open textbook overview of flux core arc welding draws the line simply: FCAW-S protects itself with the flux core, FCAW-G adds an external shielding gas, and nearly every practical difference in your pattern traces back to that choice.

FCAW-S: Self-Shielded Wire on DCEN

Self-shielded electrodes such as E71T-8 and E71T-11 run DCEN for best results, and the reason is electron heating. With the electrode negative, the arc delivers far greater heat to the wire than to the workpiece, giving the flux time to break down and release shielding gases before the wire reaches the pool. On DCEP you lose that advantage entirely.

That heat arrives through the electrode extension, the stretch of wire between the drive rolls and the contact tip. Resistance heating follows Hres = I²R, so a longer stick-out turns more of the arc’s energy into heat in the wire instead of in the joint. Some procedures call for an extension of about 3 to 3-3/4 in. for exactly this reason, and the GMAW and FCAW handbook walks through the technique and the polarity logic behind it.

Here is the trade-off that changes how you weld. A long stick-out combined with DCEN means less arc heat reaches the base metal, so penetration is poorer than with CO2-shielded E71T-1 on DCEP. You are borrowing heat from the plate to feed the flux, and the pattern compensates with slower, more deliberate travel and a firmer drag angle.

Two Self-Shielded Wires, Two Personalities

The two common self-shielded classifications differ enough that experienced welders pick between them for the joint, not the spool price. E71T-8 weld metal typically lands near 0.06% carbon with higher manganese and lower aluminum, which is where its excellent Charpy toughness comes from. E71T-11 typically runs near 0.26% carbon with higher aluminum and lower manganese, trading toughness for a smoother arc, easier slag release and a better looking bead.

That carbon has a shop floor consequence: because it raises the risk of hydrogen-assisted cracking, plates over 1/2 in. thick generally need preheat when running E71T-11.

Property	E71T-8 (self-shielded)	E71T-11 (self-shielded)	E71T-1 (gas-shielded)
Polarity	DCEN	DCEN	DCEP
Carbon	About 0.06%	About 0.26%	Lower
Aluminum / manganese	Lower Al, higher Mn	Higher Al, lower Mn	Not deoxidized with Al
Charpy toughness	Excellent	Reduced	Good
Arc and slag	Less smooth	Smoother arc, easy slag release	Smooth arc, less spatter

FCAW-G: Gas-Shielded and More Versatile

Gas-shielded flux core wire runs DCEP, and that single change flips the heat balance back toward the plate. You get smoother arc action, less spatter, and a puddle that behaves more like a gas-shielded process than a stick electrode. The cost is wind protection. AWS’s overview of flux cored arc welding is blunt about how fast a shielding gas curtain is torn apart outdoors, so a windy day means shields, shelters or a change of plan.

Gas-shielded flux core is also the more versatile of the two, reaching strengths self-shielded wire does not. The Fabricators’ Guide notes that current technology limits self-shielded FCAW deposits to 90 ksi tensile strength or less, while higher-strength gas-shielded flux cored electrodes are available.

Short Note: Picking the consumable comes before pattern work. If you are still choosing electrode by position, start with our all position welding rod guide, and for alloy steel base metal read our alloy steel welding electrodes guide before you touch the gun angle.

What This Means for Your Pattern

On both wire types the slag-forming drag is the norm, because the pattern pushes slag behind the arc where it can freeze, chip off and stay out of the toe. Where they diverge is margin for error. Self-shielded wire is far more sensitive to stick-out and angle, because that long extension and the electrode heat do the shielding work. Half an inch too much stick-out and the flux does not gas properly. Two degrees off on the drag and the slag lands on the toe instead of behind it.

With gas-shielded wire the same mistake is a smaller event. The gas does the protecting, the arc is cleaner, and the pattern you learned holds across a wider range of travel speed and work position. Practically, self-shielded work rewards a slower, more exacting pattern with longer pauses and tighter control of angle, while gas-shielded work lets you push a faster, slightly wider weave with far more forgiveness. The pattern is the same shape in both cases. The tolerance around it is not.

I’ll rewrite this section to fit the 576–864 word range while keeping the heading, facts, and all links intact.

Let me first count the current fragment’s approximate length to know how much to cut or add.

The current fragment appears to run around 1,050–1,100 words, so it needs meaningful tightening. Let me check the key elements to preserve:

– Heading: Torch Angle, Travel Speed and How They Govern Your Pattern
– Links to preserve: Goodheart-Willcox GMAW/FCAW Handbook, WPS America PDF, OpenWA FCAW techniques, Welding Digest AWS, OpenWA FCAW overview, WeldZen aluminum flux core welding
– Facts: 5–15 degrees drag angle, 10–15 degrees from perpendicular, 10–20 degrees either side of vertical, 6 mm (1/4 in.) contact tube recess, ~5 mm from manufacturers, heat input formula, three benefits of hesitation motion, weave width vs wire diameter

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Torch Angle, Travel Speed and How They Govern Your Pattern

A pattern is not a drawing you follow by eye. It is the visible result of three machine settings and one physical decision: where you point the torch, how fast you move it, and how you manage the puddle. Change any one of those and the pattern changes with it. Learn to read the three and you can diagnose most bad beads before the inspector does.

Drag or Push: The Slag Decides

Every flux core weld is either dragged (pulled) or pushed. Drag it and the arc points back toward the heat you have already laid down, so the arc sits at the leading edge of the puddle and the slag flows behind it. Push it and the arc points into cold base metal ahead of the pool, and slag can be forced ahead of the pool where it gets trapped under the bead.

FCAW is a drag process in the vast majority of cases. The memory aid that holds up on the shop floor: if there is slag, you normally drag. Pushing a flux core weld is not forbidden, but it is the exception and demands far more attention to slag behaviour than the reward is worth for most jobs.

The drag angle for FCAW is roughly 5 to 15 degrees from perpendicular, with the gun trailing the travel direction. The Goodheart-Willcox GMAW/FCAW Handbook gives longitudinal gun angles of 10 to 15 degrees from the perpendicular position for horizontal multipass groove and fillet work, where the extra lean keeps the leading toe from getting too hot and undercut.

Forehand and Backhand

Angle and direction of travel are two different things, and welders mix them up constantly. In forehand (push) technique the torch leads the travel direction. In backhand (drag) technique the torch trails it.

According to WPS America guidance, forehand gives better visibility of the joint and a flatter weld puddle, while backhand yields better penetration. The same guidance notes the torch angle is usually maintained 10 to 20 degrees either side of vertical. On flux core, the visibility advantage of forehand usually loses to the penetration and slag-control advantage of backhand, which is why drag wins by default.

The Three Machine Controls, in Plain Terms

Each setting on the machine does one job, and each one feeds the pattern:

• Voltage sets arc length. Raise it and the arc stretches longer and softer. Lower it and the arc shortens, concentrates and sounds harder. A long arc sprays metal, widens the bead and lets slag form ahead of the pool.
• Wire feed speed sets deposition rate and current. Push more wire and the machine raises amperage to melt it. That gives a bigger puddle, faster travel capability and a wider bead. Dial wire feed down and the puddle shrinks, which is what you want overhead or vertical.
• Travel speed sets heat input per unit length. Move slower and you put more heat into each inch of joint. Move faster and the bead flattens and penetration drops.

Heat input per inch is calculated as voltage multiplied by amperage, multiplied by 60, divided by travel speed in inches per minute:

Heat input (J/in) = (Voltage x Amperage x 60) / Travel speed (in/min)

This number explains a lot of bad beads. A wide weave slows your effective travel along the joint, so the same settings produce higher heat input per inch than a stringer at the same wire feed speed. Wide weave plus high amperage is the classic recipe for a fat, sagging bead with undercut toes. Always treat the WPS as the authority on allowable heat input; the formula is for understanding what your hands are doing.

Contact Tip to Work Distance

The gap between contact tip and work is short for a reason. A long extension heats the wire, which on self-shielded flux core is useful (the FCAW technique guidance from OpenWA notes this benefits stick-out technique), but it also costs you arc stability and directional control.

Control that distance by recessing the end of the contact tube inside the cup nozzle. The Goodheart-Willcox handbook recommends recessing the contact tube at least 6 mm (1/4 in.) inside the nozzle, and some manufacturers suggest about 5 mm. That gives a consistent stick-out as you work rather than letting the nozzle crowd the joint.

The Stepping or Hesitation Motion

This is the small pause you make at the toes of the bead, and it does more work than it looks like it does. The Welding Digest explanation of FCAW practice lays out three benefits:

1. The pool cools slightly, so it does not sag or run ahead of the arc.
2. Slag gets time to float up to the surface instead of being rolled into the bead.
3. The bead comes out cleaner, with less chance of a slag inclusion.

Notice the sequence built into a weave: brief hesitation at the toe for placement and slag clearance, then quick movement across the centre. The hesitation belongs at the edges, not the middle.

Weave Width, Wire Diameter and Bead Profile

Weave width should stay proportionate to wire diameter. A 0.045 in. wire does not want to be swept across a 3/4 in. face. Push the width and you get a wide, flat, cold bead with poor sidewall fusion and toes that never get properly filled. That relationship is the reason many shops keep the bead narrow.

For a wide joint, multiple stringer passes usually beat one wide weave. Each stringer deposits clean metal in a controlled position, gives you more interpass cleaning opportunities, and stacks into a wide joint without the sidewall fusion problems of a single sweeping bead.

Before you finalise any of these settings, confirm the procedure rather than the habit. Detailed pattern and parameter guidance for FCAW setups is covered in the FCAW overview, and when the base metal is aluminium the considerations shift enough to be worth reading separately in aluminum flux core welding: what actually works.

Troubleshooting Bad Patterns: Undercut, Overlap, Cold Lap and Porosity

A bad bead is usually a bad pattern before it’s a bad setting. Instead of reaching for the knobs first, read the bead. The toe, crown, and edges will often tell you exactly what your path did wrong.

Undercut: the groove that eats the toe

Undercut is a groove melted into the base metal next to the weld toe with no weld metal to fill it. On a fillet, it eats into the leg. Under AWS acceptance criteria, this isn’t cosmetic, and any undercut must be ground out and rewelded.

According to the open FCAW defects and discontinuities reference, the causes are excessive heat at the toe from high current or voltage, travel speed that’s too fast, poor edge preparation, or dirt and grit on the surface.

Most of these come down to your pattern. Watch out for the following:

• A fast weave with no toe pause: Skipping the edges means the arc never dwells long enough to wet them.
• A centre-heavy dwell: Holding in the middle dumps heat down the centreline, melting channels into the toes instead.
• The wrong lead angle: A push angle on a drag process can throw the arc towards the toe and away from the puddle.

The fix is simple: correct your angle, shorten arc length, adjust travel speed and amperage, and repair any existing undercut. A grinder is a repair, not a habit fix.

Overlap and cold lap: when the puddle gets ahead of you

Overlap is when the molten puddle runs ahead of the arc and spills over the toe onto unwelded base metal. Cold lap takes it a step further, rolling over without fusing at all. From the outside, it can look like a clean, rounded bead, but radiography will expose two pieces sitting on top of each other.

Both are caused by an imbalance between puddle size and travel speed. Too much heat, too little travel, or an oversized pool will overrun the arc. On vertical-up, watch the puddle behind the arc, not the arc itself. Often, less dwell at the centre and more controlled travel will correct it without raising wire feed.

This is closely tied to incomplete fusion. A wide, quick weave across cold plate is the classic culprit, as the leading edge of the pool never reaches fusion temperature on the sidewall. Slow down, hold on the toe to wet it, and raise heat only if the joint is still too cold.

Porosity: shielding, cleanliness, and the wormhole

Porosity is trapped gas, and it comes in multiple forms. The FCAW overview chapter points to insufficient shielding, improper gas flow, moisture, rust, dirt on the base metal or consumables, excessive current, or an overly long arc.

Form	What you see	Usual root cause
Surface porosity	Pitted craters on the bead face	Moisture, rust, dirty wire, or wire feed too high
Subsurface porosity	Round voids seen on radiographs	Unshielded arc or excessive arc length
Linear porosity	A dark line along the weld on film	Slag trapped in the deposit or inclusions
Wormhole porosity	Large open cavity, often visible through the section	Severe gas entrapment, moisture, or poor surface prep

Wormhole porosity is by far the most severe, as it can create a leak path straight through the weld. For pressure-retaining work, it must be air gouged or ground out and rewelded, with the cause corrected before the repair.

For FCAW-S, there is no gas cylinder. Shielding comes from the flux core, so stick-out length and travel speed become shielding parameters. Wire selection and polarity are equally critical. Running self-shielded wire on the wrong polarity can create an unstable arc that traps gas into the bead.

Slag inclusions and spatter

In multi-pass welds, slag left behind from a previous pass is easily entrapped by the next. These show as dark lines on radiographs. Cleaning every pass with a wire brush or chipping hammer is part of your flux core welding pattern, not an optional step.

Spatter is most often traced to arc length, travel speed, and wire feed balance. For FCAW-G, adding an argon blend can drastically cut it compared to pure CO₂. Anti-spatter spray can help, but excessive use can cause porosity. On windy sites, gas and shielding setup will be the limiting factor more often than your weave.

The common thread is simple: undercut is a path problem, overlap and cold lap are a path and speed problem, and porosity is a shielding and housekeeping problem. A stable, controlled pattern makes all three far easier to prevent.

A Practice Plan and Shop Habits That Make Patterns Stick

Patterns are motor skills, and motor skills get built one repetition at a time, with feedback faster and more honest than your own eyes. A new flux core welder usually knows the theory after an afternoon of reading, but the arc still wanders at first because the hand is learning a rhythm the brain has to stop narrating. The progression below runs from least demanding to most and takes weeks of honest practice, not hours of pretending.

A Five-Step Practice Progression

Step	Focus	What to work on
1. Stringers, flat position	Travel speed and arc length	Mild steel on a simple butt or lap joint. Even width, even height. A tall bead means you went slow; flat and wide means you went fast or drifted arc length. Once those feel boring, add torch angle: hold the drag at a consistent 10 to 15 degrees and watch the profile change when you deliberately change it.
2. Flat and horizontal fillets	Heat and toe coverage	Stringer down the joint, then the same joint with a gentle crescent, and compare. Horizontal position: keep the puddle narrow, watch for the moment gravity starts pulling it toward the lower plate, then stop traveling and let it set.
3. Vertical-up	Triangular weave	Work uphill from the bottom, hesitate deliberately at both toes, keep the centre crossing fast. Count the beats out loud at first. Awkward for a while, then automatic, which is what you want before overhead.
4. Overhead	Stringers only	Short stick-out, small pool. Any hesitation up there invites the puddle to drip onto your helmet. Practise until you can place a short stringer without looking at it.
5. Multi-pass groove work	Cleaning discipline	Fill a V-groove with multiple stringer passes, chip and grind every pass before covering it, and note how clean interpass surfaces change the next pass. Slag left behind becomes an inclusion, and inclusions become a rejection.

Inspect Coupons, Not Impressions

Do not judge a practice bead by how it looks while it is still hot and glowing. A good bead looks flat and slightly dull when you look at it, and it will look considerably worse than a bad one for a couple of minutes after the arc breaks.

Five Habits That Keep a Pattern Consistent in Production

• Watch the puddle behind the arc, not the arc itself. The arc is bright and distracting. The puddle is where your heat is going, and it is the part of the weld you can still control.
• Hold travel speed and arc length steady. Most poor beads come from a wandering hand, not a bad setting.
• Clean every pass before you cover it. Slag and spatter left behind become inclusions in the next one.
• Keep the gun angle constant. Changing drag angle changes penetration, bead shape and slag behaviour all at once.
• Change one variable at a time. Adjust one thing, run another coupon, look at the result. Changing voltage, wire feed and travel speed together teaches you nothing.

FCAW or GMAW: Which Process Deserves the Job?

The AWS Welding Digest makes the distinction cleanly: flux core wins on high-deposition, heavy-duty and outdoor work because it feeds faster, tolerates wind better and lays down serious poundage. GMAW produces cleaner welds with lower spatter and far lighter post-weld cleanup, which is why it dominates in controlled shops where finished appearance matters. One practical difference shows up on every work order: FCAW leaves slag, GMAW does not. That slag means chipping, grinding and interpass cleaning in your routine, so plan for it in the schedule rather than treating it as a surprise at the end of the shift.

Safety: The Pattern Is Made in Your Breathing Zone

Every good pattern in this article is made a few inches from your face.

The OSHA welding fume fact sheet states that prolonged exposure to welding fume may cause lung damage and cancers including lung, larynx and urinary tract, along with irritation, dizziness and nausea. It also notes that prolonged exposure to manganese fume can cause Parkinson’s-like symptoms, and that short-term exposure can cause metal fume fever.

For hexavalent chromium, the permissible exposure limit is 5 micrograms per cubic metre as an 8-hour time-weighted average, regulated under 29 CFR 1910.1026 and 1926.1126. OSHA requires engineering and work practice controls as the primary means of reducing fume exposure, with local exhaust ventilation preferred over dilution ventilation and respirators supplementing those controls rather than replacing them.

The open FCAW techniques text recommends a fume extractor with a flexible hose arm positioned close to the fume source, and notes welding guns with built-in fume extraction as another option. Welder fume extraction guns and welding helmets with respirators are both reasonable kit additions. If you are new to the process, review what an aluminium welding course covers, since the same fume questions apply with extra emphasis on cleaning.

Build the progression, keep the five habits, and the pattern stops being something you think about. It becomes something your hand already knows, which is the whole point.

Conclusion: Choosing the Right Flux Core Welding Pattern

Start with a stringer and weave only when you have a reason. That one habit will carry you further than any trick you pick up later. A stringer bead is the default flux core welding pattern because it concentrates arc force on the centreline, keeps the puddle small and controllable, pushes the slag behind the arc, and gives you a narrow bead that is easy to inspect. A weave, by contrast, is a deliberate response to a specific condition: the joint needs wider coverage, the toes need deliberate fusion, or the position demands more pool control than straight travel can give.

A quick-reference card for the next job

Position changes the operating point far more than it changes the pattern, so the pattern itself stays relatively simple. The all-position rod guide covers the same logic for stick welding, and the reasoning transfers straight across to flux core.

Situation	Default pattern	What to watch
Flat position	Stringer, or a gentle crescent	Steady drag angle and travel speed, the place to build speed
Horizontal	Stringer or a very slight weave with a pause at the upper toe	Wire angled at the upper plate, the puddle fights gravity
Vertical-up	Triangular weave with brief pauses at both toes	Travel uphill, watch the puddle behind the arc, cut heat input
Overhead	Stringer only, short stick-out	No hesitation, a large overhead puddle drips
Wide groove joint	Multiple stringer passes	Clean between passes and build width in layers

Read the last row carefully. A wide weave lays down a flatter, thinner cross-section, spreads heat unevenly, and raises the chance of a cold lap along the centreline where the arc dwells. Multiple stringer passes are frequently the stronger and more consistent answer, and along the way they give you better interpass cleaning and coverage control.

Three things decide quality, and the pattern is not one of them

1. The qualified procedure. The WPS governs filler classification, position, joint detail and every other essential variable, and the prequalified ranges in AWS D1.1 set the limits. On code work, a beautiful pattern outside those limits is still a nonconformance.
2. The wire classification and polarity. E71T-8 and E71T-11 want DCEN and a long stick-out; gas-shielded E71T-1 runs DCEP. The AWS Welding Digest guide to flux cored arc welding covers how shielding reshapes the balance of arc, puddle and slag, and your pattern has to follow the wire you actually loaded.
3. Angle, travel speed and puddle control. The pattern is a relationship between the drag angle, the travel speed and the behaviour of the pool. Change any one of the three and the same drawn path produces a different bead.

On choosing the process at all: FCAW and GMAW run on nearly identical equipment, so the decision rests on environment, deposition requirement and finish expectations rather than setup complexity. FCAW wins outdoors and on heavy deposition, GMAW wins on cosmetic finish and cleanup. Weighing the full family, including why stick welding still wins on some jobs, is worth doing before you commit a spool.

The last word

On any code or contract job, the WPS beats every rule of thumb in this article. And interpass cleaning is part of the pattern, not a housekeeping afterthought. Slag left between passes is a direct cause of slag inclusions in the following pass, which is exactly why a wide groove joint is better built from a series of clean stringers than one wide weave.

Keep one idea in front of you: the pattern is a controlled motion, not a flourish. The best flux core welders on the floor are not the ones who can draw the fanciest triangle. They are the ones whose beads look like they were placed there on purpose, every time, because they control the motion instead of performing it. That is a learnable skill, and for a new flux core welder it is one of the fastest ways to move from beads that merely pass inspection to beads that look like they belong on the structure.

Frequently Asked Questions

What is the difference between a stringer bead and a weave bead in flux core welding?

A stringer bead is deposited with the torch travelling mainly along the joint with little or no side-to-side motion, producing a narrow bead that is easy to control in every position. A weave bead adds a deliberate side-to-side path — triangle, Z, crescent or figure-eight — to cover more width or to place metal deliberately at the toes. Because flux core produces slag, a stringer is the normal default and a weave needs a reason.

Is a wider weave bead stronger than a stringer bead?

No. Strength comes from sound fusion, correct heat input, the qualified procedure and the filler metal, not from the shape of the torch path. A very wide weave actually produces a flatter, thinner cross-section with uneven heat distribution and a greater risk of cold lap at the centreline, so a wide groove is usually better filled with several stringer passes than one broad weave.

What is the best flux core welding pattern for vertical-up fillet welds?

A triangular weave with a brief hesitation at each toe is the most common answer for vertical-up fillets, because the pause lets the puddle wet into the sidewall before the arc moves away. On smaller welds a short side-to-side motion is enough, and some qualified procedures allow stringer beads where the wire is approved for them. The wire data sheet and WPS decide, not general advice.

Should I push or drag the torch when welding with flux core?

Drag it. Flux core leaves a slag layer, and a drag angle of roughly 5 to 15 degrees from perpendicular keeps the arc at the leading edge of the puddle with the slag flowing behind. Pushing tends to force slag ahead of the pool, which is a common route to slag inclusions. A useful memory aid is: if there is slag, you normally drag.

How wide can I weave a flux core weld?

Stay inside the limits of your qualified procedure. Lincoln Electric’s technique guidance for vertical-up work advises not weaving wider than 3/4 in. (20 mm) and using a split weave if the joint is wider than that. AWS D1.1 and the WPS control what is acceptable on code work, and bead profile and undercut are judged against the visual acceptance criteria regardless of how attractive the bead looks.

Does switching from self-shielded to gas-shielded flux core change the pattern rules?

Yes. Changing the wire type changes the filler classification on the WPS, which is an essential variable and can require requalification under AWS D1.1 Clause 6. Self-shielded wires such as E71T-11 and E71T-8 run on DCEN and rely on resistance heating at the wire extension to activate the flux, while gas-shielded wire usually runs on DCEP and needs protection from wind. The drag-and-slag rule still applies to both, but self-shielded wire is far less forgiving of stick-out and angle changes.

Can I use a weave pattern if my WPS calls for stringer beads?

No. A prequalified procedure is only valid while its essential variables stay inside the code limits, and a permitted weave pattern is part of how the procedure was qualified. A pretty wide weave on a procedure written for stringers can void prequalification and requires qualification testing before you return to production. If you want to weave, the procedure needs to say so.

Why does my flux core bead undercut at the toes?

The usual causes are too much heat, travel speed that is too fast, a drift in torch angle and poor edge preparation. In pattern terms, a weave that moves quickly across the joint without pausing at the toes removes the heat before the toes are filled. Fix it by reducing amperage, shortening the arc, correcting the electrode angle, adjusting travel speed, and grinding out and rewelding the undercut.

Do I have to clean the slag between passes on a flux core weld?

Yes. Slag left on a completed pass becomes trapped in the following pass, which is a leading cause of slag inclusions, and multi-pass welds are far more prone to them than single-pass welds. Interpass cleaning is part of the procedure, not an optional extra, and it also gives you a chance to inspect for undercut and incomplete fusion before they get buried.