On the 6G pipe test, the fixed 45-degree joint runs all-position with no rotation, and the hot pass is the second pass: the bead laid over the root before any fill begins. This is where most tests are won or lost.
The root gets the attention, but the hot pass carries the real tension. Run too cold and trapped slag and incomplete fusion turn up on the X-ray; run too hot and you burn through the root you just fought to lay. A 3/32" E7018 at the wrong amperage does both.
At many Shipyard Apprenticeship Programs, first-time 6G pass rates sit under 30 percent, and hot pass defects rank near the top of the reasons why.
What Is a Hot Pass in Welding?
A hot pass is commonly the second weld pass laid directly over the root pass, run before any fill passes begin. On a 6G pipe test, it usually goes down with a 3/32" E7018 low-hydrogen stick electrode, at a slightly higher amperage and faster travel speed than the root. The pass is thin and deliberate, and it is functional rather than decorative: it prepares the joint instead of building it.
Its Real Job on the Pipe
The hot pass has three specific purposes, and none of them is filling the groove:
- Burn out trapped slag: The root pass, especially an open-root TIG or 6010 open root, often leaves small slag pockets or wagon tracks along the toes. The extra heat of the hot pass melts those inclusions out before they get buried under fill metal.
- Ensure full fusion at the root toes: By tying cleanly into both sidewalls of the bevel and into the top of the root bead, the hot pass eliminates the cold laps and lack-of-fusion defects that x-ray inspectors look for first.
- Refine the root profile: It flattens any crown on the root, evens out ripple height, and gives the fill passes a clean, uniform surface to build on.
Not a Fill Pass
This distinction matters. A fill pass is about depositing volume and building the joint toward the cap weld. A hot pass is about cleaning and reinforcing what is already there. You run it hotter but move faster, using a controlled side-to-side weave or a tight whip to wash the toes without piling metal in the center. If you slow down and try to fill with it, you trap slag and defeat the purpose.
On the 6G Pipe Welding certification test, where the pipe is fixed at a 45-degree angle and you weld all positions in one continuous joint, the hot pass is where most inspection failures are prevented, or created.
Hot Pass Vs. Root, Fill, and Cap Passes
Many welders learn the root pass first and assume the hot pass is just a faster repeat. In practice, the root and hot pass solve different problems, and recognizing the distinction prevents most 6G failures.
Where Each Pass Fits in the Weld
A pipe weld is built in four stages, each with a specific job:
- Root pass: this open-root pass creates full penetration and fuses the pipe inside edge.
- Hot pass: the next pass removes slag and smooths the root before the groove gets narrower.
- Fill passes: these add the bulk of weld metal and build thickness to the joint.
- Cap pass: the final pass creates the required reinforcement and gives the weld its finished face.
Hot Pass vs. Root Pass
In Stick Welding, the root pass is usually run with a smaller electrode such as E6010 or E7010 because the open gap demands controlled, digging arc characteristics. The hot pass is run with a larger electrode, typically E7018, at higher amperage. Its main purpose is not penetration; it is cleaning and fusing the root. A hot pass also burns out small slag pockets, removes any remaining wagon tracks, and smooths the root face before fill metal goes in. It is also run faster to keep heat moving and reduce undercut risk.
Hot Pass vs. Fill and Cap
Do not confuse the hot pass with fill passes. Fill passes add volume and build the groove outward. The hot pass only cleans and conditions the root. Once the hot pass is in, fill passes stack until the joint is just below flush. The cap weld then runs with a slight weave or stringer to create final reinforcement.
This sequence matters because a cold or poorly cleaned hot pass can leave slag inside the root, and a cap pass applied over an unfilled groove will lack the correct face reinforcement. A common mistake is to run one heavy fill pass instead of multiple stringers, which creates uneven heat input and a high crown. Keep each pass in its place.
Tools and Settings for the 6G Hot Pass
An E7018 hot pass is not a place to guess settings. The electrode, amperage, polarity, and cleaning steps you choose before striking an arc determine whether the pass fuses the root, pushes out trapped slag, and leaves a clean shelf for fill passes and the cap weld.
Electrode Choice and Starting Amperage
On carbon-steel pipe with an open root, the common sequence is an E6010 root followed by an E7018 hot pass. The two workhorse hot pass electrodes are 3/32-inch and 1/8-inch E7018. Start with a range, not a single number:
- 3/32-inch E7018: 70 to 100 amps, 20 to 24 volts1
- 1/8-inch E7018: 90 to 130 amps, 24 to 28 volts1
- 5/32-inch E7018: 130 to 180 amps, 24 to 28 volts1
For a 6-inch Schedule 80 pipe, many welders start with a 1/8-inch electrode around 90 to 130 amps; a 3/32-inch electrode is more often run at 70 to 100 amps.1 On heavier-wall or larger-diameter pipe where access permits, a 5/32-inch E7018 may be used, with practical hot pass ranges around 130 to 180 amps.1 Vertical and overhead sections often run cooler: 80 to 120 amps for 1/8-inch and 110 to 180 amps for 5/32-inch.2 These are starting windows, not universal qualified procedures. One AWS D1.1:2025 summary lists 1/8-inch E7018 at 90 to 160 amps and 4 to 8 inches per minute, while electrode manufacturer sheets list narrower ranges for specific formulations.3 A 3/16-inch E7018 is generally reserved for fill and cap passes after the hot pass has been placed cleanly.
Polarity: DCEP for E7018
Use direct current electrode positive (DCEP) for E7018. DCEP directs more heat into the workpiece and less into the electrode, which improves arc starts, puddle control, and penetration on the hot pass. Running E7018 on the wrong polarity often produces a rough, erratic arc and weak slag coverage.
Voltage and Travel Speed
On a constant-current SMAW machine, you set amperage, not voltage. The arc length controls actual voltage. Typical operating voltages are 20 to 24 volts for 3/32-inch E7018, 24 to 28 volts for 1/8-inch, and 24 to 28 volts for 5/32-inch hot passes.1 Keep the arc short enough to avoid undercut and porosity. Common WPS examples show travel speeds of about 4 to 8 inches per minute for 3/32-inch and 5 to 10 inches per minute for 5/32-inch.4 Move at a steady pace and avoid a wide weave that lets the puddle roll ahead of the arc.
Clean Between Passes
Cleaning between passes is not optional on a hot pass. After the root pass, remove all slag, oxidation, and spatter with a wire brush or a light grinder. In a 6G pipe welding procedure, trapped slag under the hot pass is one of the most common weld defects. Clean the root face enough to expose bright metal, but do not grind so deep that you thin the root or leave a groove for the hot pass to bridge.
Step-By-Step 6G Hot Pass Technique With E7018
Today's 6G pipe tests still turn on the hot pass more than any other single bead. With E7018, the window between a clean, fused hot pass and a failed test is narrow, so technique has to stay deliberate from the moment you strike the arc.
Strike and Set the Rod Angle
Run the hot pass only after the root has been cleaned and lightly ground or feathered where needed. Use a 3/32-inch or 1/8-inch E7018 rod and keep the amperage on the lower end of the rod's range, often 90 to 115 amps for 1/8-inch, so you do not wash out the root. Hold a 5 to 15 degree drag angle through the flat and horizontal portions of the 6G position. As the pipe rotates your body around the fixed 45-degree position, the joint orientation changes, but the rod angle stays tied to the direction of travel, not to the floor.
In the overhead section, shift to a near-vertical push angle, as you would on a 4G SMAW Certification test. This lets the arc force lift the molten metal up into the root instead of letting it sag onto your hood. Do not hold a long arc. A tight arc keeps the puddle small and predictable.
Control the Puddle: Sidewall Pauses and Travel Speed
Work the puddle side to side. Pause 1 to 2 seconds on each bevel wall. That dwell time lets the arc dig out any shallow undercut left by the root pass and ties the hot pass into both sides of the groove. Whip quickly across the center, just fast enough to keep the crown from piling up. The goal is a flat or slightly convex bead, not a rope in the middle of the joint.
Keep travel speed moderate, about 4 to 8 inches per minute depending on wall thickness, root opening, and amperage. Thicker wall with a wide root face will accept a slower sidewall pause. Thin wall or a tight root needs more travel speed and less center dwell. If the keyhole drops out or the puddle becomes watery, back off amperage or speed up slightly.
On the vertical sides of the 6G coupon, shorten the sidewall pause just enough to keep the puddle from sliding. Many welders hold a near-perpendicular rod angle or a very slight upward push there, much like the technique for 3G SMAW Certification. Overhead requires the opposite adjustment: hold the sides a fraction longer and cross the center faster, because gravity pulls the puddle down if you linger in the middle.
Clean, Inspect, and Adjust Before Fill Passes
When the hot pass is complete, chip the slag completely and wire brush the bead. Check both toes for lack of fusion, undercut, or trapped slag. Look at the crown height. The hot pass should fill the groove without closing it off. A convex center bead will make the fill pass struggle to wet into the sidewalls. Grind any high spots or wagon tracks before you start filling.
If you find a pinhole or a small void, grind it out and repair that section before moving on. Do not let a hot pass defect ride into the fill passes. In 6G, a small discontinuity in the hot pass often becomes a larger repair after the cap weld goes on.
Hot Pass Sequence at a Glance
The hot pass locks in the root and starts building the joint. Follow this sequence after the root pass passes inspection and before any fill or cap pass.
Common Hot Pass Defects and How to Fix Them
Even a well-run 6G hot pass can leave discontinuities that fail inspection during Welder Certifications. Knowing what causes each one, and what it looks like on the surface, is how you catch problems before an X-ray does.
Wagon Tracks
"Wagon tracks" is a nickname, not an official defect category. It describes the twin dark lines that show up along the toes of the hot pass, usually pointing to lack of fusion, cold lap, or undercut underneath.1 Before you grind and repair, identify which of those is actually present. Causes typically trace back to amperage that's too low to wash out the root toes, or travel that's too fast to let the arc melt into the sidewall. Slowing down and adding a deliberate pause at each toe usually resolves it on the next attempt.
Undercut
Undercut shows up as a visible groove melted into the base metal at the weld toe, left unfilled by filler metal. It comes from excessive amperage, too steep a rod angle, or rushing the pass without enough sidewall hold. Inspectors measure depth with a V-WAC gauge or bridge cam gauge. AWS D1.1 visual guidance generally allows up to 1/32 in on tension members1 and statically loaded connections, tightens to about 0.01 in for cyclically loaded welds, and permits up to 1/16 in on compression members and welds not carrying primary tension1, though the applicable limit always depends on the specific member and loading condition. Fix undercut by dropping amperage slightly and holding a one or two count at each sidewall before moving on.
Burn-Through
Burn-through looks like a hole, sag, or icicle hanging through the root, and it's never accepted as-is. It happens from excessive heat input, amperage set too hot, travel too slow over the root opening, or a wider-than-expected root gap.3 Correct it by increasing travel speed slightly, lowering amperage, and using a tighter, more controlled whip pattern instead of dwelling in one spot.
Incomplete Fusion
Surface lines can hint at fusion problems, but visual inspection alone can't confirm what's happening beneath the surface. Suspected subsurface lack of fusion requires ultrasonic (UT) or radiographic (RT) testing to verify.3 Cracks are never permitted under any circumstance, and any surface lack of fusion is rejectable on sight.1
Inspection Sequence
Before judging any defect, clean the interpass area thoroughly.4 Visual inspection (VT) catches surface-breaking flaws like undercut and wagon tracks. Dye penetrant (PT) reveals fine surface cracks invisible to the eye. Radiographic (RT) and ultrasonic testing find subsurface incomplete fusion and porosity. After any repair, re-run the same inspection sequence. A ground and reworked surface can look perfect and still hide an unsound weld underneath before you move on to cap welding techniques.
Did you know that first-time pass rates for 6G pipe welder qualification testing often fall under 30 percent at top shipyards, according to a ClarUP career guide? Hot pass problems, including trapped slag and incomplete fusion, rank among the leading causes of failure, making clean hot pass technique essential before you ever attempt the cap.
Related Articles
Delayed hydrogen cracking in carbon steel welds can appear up to 72 hours after welding, per TWI Global research, which is why many codes require inspection be delayed 16 to 48 hours. A properly heated hot pass lowers cooling rates and helps bake out hydrogen, reducing crack risk.
Frequently Asked Questions About Hot Passes
These answers cover common questions about hot pass technique, amperage, electrode selection, and defect prevention. Always follow the qualified welding procedure specification for your job.
- What is the difference between a root pass and a hot pass?
- The root pass fills the bottom of the joint and creates full penetration through the open root. The hot pass is the next pass made while the joint is still warm. Its job is to remelt the root surface, burn out trapped slag and porosity, and improve sidewall fusion before fill and cap passes.
- How much amperage should I use for a hot pass with 7018?
- There is no single hot pass amperage. For a common 1/8 inch E7018 electrode, 100 to 130 amps is a reasonable starting range when the procedure permits.2 A typical adjustment is 10 to 20 percent above root pass current, but thickness, fit-up, position, and manufacturer limits can move that number higher or lower.
- Can I use 7018 for a hot pass over a 6010 root?
- Yes, but only when your qualified welding procedure allows it.3 E6010 is often used for the open root because of its arc characteristics, while E7018 provides low-hydrogen fill and cap passes. Clean the 6010 root thoroughly, remove slag, and use careful arc control and correct polarity.
- How do you avoid wagon tracks in a hot pass?
- Clean the entire root before the hot pass and remove visible slag from both bevel toes.4 Keep the root flush without pronounced shelves or undercut. Use enough heat to remelt the root and tie into both bevels without washout. Hold a short, controlled arc directed at the toes and use a travel speed that wets both sides.
- Is a hot pass always the second weld pass in pipe welding?
- No.1 In open-root multi-pass pipe welds it is commonly the second pass, but hot pass is a function rather than a fixed pass number. Some procedures use a separate hot pass, others combine root and hot pass with the same electrode, and some designs have no distinct hot pass. The weld procedure specification, code, joint design, electrode, position, and interpass temperature govern this.
- What does API 1104 say about hot pass limits?
- API 1104 does not define hot pass or set separate hot pass limits. In pipeline work governed by that code, hot pass practice follows the approved welding procedure, which may specify electrode, current, travel speed, and other parameters. Always check the procedure before changing technique, amperage, or electrode.