3G And 4G Welding Test – Mastering Vertical And Overhead Plate
The 3G and 4G welding tests are structural certifications for vertical (3G) and overhead (4G) groove welds, typically performed on 3/8″ or 1″ steel plates. Passing these tests demonstrates a welder’s ability to manage the molten puddle against gravity, often qualifying them for multiple welding positions in structural steel work.
To pass, you must ensure perfect root penetration, avoid slag inclusions between passes, and maintain a clean “cap” with no undercut. Most tests are evaluated via visual inspection followed by a destructive bend test to check for internal defects.
Stepping up to a 3g and 4g welding test is a major milestone for any metalworker. It marks the transition from basic hobby welding to professional-grade structural competence. If you can handle the molten metal when gravity is trying to pull it out of the joint, you have truly mastered the puddle.
We all know that welding on a flat workbench is comfortable, but the real world isn’t flat. Whether you are repairing a trailer frame or building a workshop mezzanine, you will eventually have to weld vertically or reach above your head. These tests prove you have the technical skill and the steady hand to do it safely.
In this guide, I will walk you through everything you need to know to prepare for, execute, and pass these certifications. We will cover the specific plate setups, the best rod techniques, and the common pitfalls that cause coupons to fail the dreaded bend test. Let’s get your booth ready and your welding machine dialed in.
Understanding the Mechanics of 3G and 4G Positions
In the world of the American Welding Society (AWS), “3G” refers to a vertical groove weld. This is a vertical uphill or downhill weld on a plate, though most certification tests require the uphill progression. Uphill welding provides much deeper penetration, which is critical for structural integrity.
“4G” refers to the overhead groove weld. In this position, the plates are horizontal, but you are welding from underneath them. This is often considered the most difficult test because the molten slag and metal want to drip directly onto your hands and face.
When you take a 3g and 4g welding test, you are usually working with a V-groove joint. This involves two plates beveled at an angle to create a “V” shape. You fill this gap with multiple passes, starting with a root pass and ending with a decorative but strong cover pass.
Why These Positions Matter
Passing a 3G test often qualifies you to weld in the 1G (flat), 2G (horizontal), and 3G positions. If you pass the 4G test alongside it, you are frequently certified for all plate positions. This “combo” is the gold standard for structural welders entering the workforce.
For the DIYer or garage tinkerer, practicing these positions is about safety. If you are welding a critical bracket on a vehicle or a structural support in your shop, you need to know that your vertical and overhead welds aren’t just “sticking” but are actually fused to the base metal.
Gravity is your biggest enemy here. In the 3G position, the puddle wants to sag downward, creating a “shelf.” In 4G, the puddle wants to fall out of the joint. Learning to use arc force and travel speed to counteract these forces is the key to success.
Essential Tools and Materials for the Test
You cannot just grab scrap metal from the bin and expect to pass a formal 3g and 4g welding test. You need standardized materials to ensure the results are consistent. Most tests use ASTM A36 steel plates, which are a common mild steel used in construction.
The plates are typically 3/8 of an inch thick for a “limited thickness” test. You will also need a backing strip, which is a flat bar tacked to the back of the “V” to catch the root pass. This makes the test slightly easier than an open-root test but still requires precision.
Your choice of electrode is also vital. Most structural tests use the E7018 rod. This is a low-hydrogen electrode that produces very strong welds. Sometimes, an E6010 rod is used for the root pass to ensure deep penetration, followed by 7018 for the fill and cap.
Preparation Tools Checklist
- Angle Grinder: Use a hard stone for beveling and a wire wheel for cleaning.
- Chipping Hammer: Essential for removing slag between every single pass.
- Fillet Weld Gauge: To check the height of your reinforcement and the size of your beads.
- C-Clamps or Locking Pliers: To secure your plates to the test stand without them warping.
- Square and Protractor: To ensure your 22.5 or 37.5-degree bevels are exact.
Safety gear is non-negotiable. For 4G welding, you need a leather welding jacket or heavy-duty sleeves. Hot sparks will fall directly on you, and a standard cotton shirt will burn through in seconds. Ensure your helmet lens is clean so you can see the leading edge of the puddle.
Step-by-Step Plate Preparation
Failure often happens before the arc is even struck. If your plates are dirty or the bevel is inconsistent, you are setting yourself up for slag inclusions. Start by grinding the mill scale off the face and the edges of your plates until you see shiny silver metal.
Clean at least one inch back from the weld zone. Any oil, rust, or scale left on the metal can release gases that cause porosity (tiny holes) in your weld. Once the metal is clean, grind your bevels. A 22.5-degree bevel on each plate creates a 45-degree included angle.
Next, set your root opening. For most 3/8″ plate tests, a 1/4″ gap is standard. Use a spacer (like a piece of 1/4″ plate) to keep the gap consistent from top to bottom. Tack the plates to the backing strip securely at both ends to prevent the gap from closing as it heats up.
The Importance of Fit-Up
A sloppy fit-up makes the welding process unpredictable. If the gap is too narrow, the root won’t penetrate. If it is too wide, you will struggle to bridge the gap without burning through the backing strip. Take your time with the square and the clamps.
Once tacked, check the plates for “draw.” The heat from the tacks can pull the plates out of alignment. If they aren’t flat, your final bend test coupons might be rejected before they even get to the press. Ensure everything is straight and rigid.
Finally, mark your “start” and “stop” points. In a formal test, you often have to demonstrate a restart in the middle of a pass. This proves you can tie two weld beads together without leaving a weak spot or a crater.
Mastering the 3G Vertical Uphill Weld
When you begin the 3G portion of the 3g and 4g welding test, your machine settings are critical. For a 1/8″ 7018 rod, try starting around 110-120 amps. You want enough heat to flow the metal but not so much that the puddle becomes uncontrollable.
Start at the bottom of the plate. Use a slight side-to-side motion, pausing briefly at the edges of the bevel. This “weave” or “stringer” technique helps the metal tie into the side walls. Pausing at the sides prevents “undercut,” which is a groove melted into the base metal that isn’t filled by the weld.
Keep your arc length short. If you pull the rod too far away, the voltage increases, and the puddle becomes erratic and hot. A tight arc concentrates the heat exactly where you need it. Watch the “shelf” of the weld; you are essentially building a staircase of metal all the way to the top.
Managing the Heat
As you move up the plate, the base metal gets hotter. You may need to speed up your travel or slightly lower your amperage if your machine allows for remote adjustment. If the metal gets too hot, the puddle will start to sag or “drip,” ruining the bead profile.
Between passes, let the plate cool slightly. You don’t want it cold, but “interpass temperature” management is vital. Use your wire brush and chipping hammer to remove every speck of slag. If you weld over slag, it stays trapped inside, leading to an automatic failure during the bend test.
The “cap” or cover pass should be slightly higher than the base metal but not more than 1/8″. It should be smooth and uniform. A ragged cap with inconsistent ripples is a sign of poor travel speed control and will likely be flagged during visual inspection.
Conquering the 4G Overhead Weld
The 4G test is a mental game as much as a physical one. Gravity is working against you, and the fear of sparks can make you rush. Position yourself so you are comfortable and your welding lead isn’t pulling on your arm. Drape the cable over your shoulder to take the weight off your hand.
For overhead, you generally want your amperage slightly lower than for vertical. This keeps the puddle “stiff.” A stiff puddle stays in the joint better. Use stringer beads (straight lines) rather than wide weaves for the fill passes. Stringers are easier to control overhead.
Keep the rod pointed almost straight up, with a very slight drag angle (5 to 10 degrees). If you angle the rod too much, the arc force will push the metal out of the groove. You want the arc force to push the molten metal up into the root of the joint.
Body Positioning and Safety
Never weld directly over your head. Position yourself slightly to the side so the sparks fall past your shoulder rather than onto your helmet or chest. Wear a leather cap under your hood to protect your hair and ears from stray “berries” of molten steel.
Focus on the “tie-in.” In overhead welding, it is easy to get cold lap, where the weld metal just sits on the surface without actually fusing. Ensure you see the edges of the bevel melting into the puddle before moving the rod forward.
The cap pass on a 4G test is the most visible part. It should be flat or slightly convex. If it is concave (sucked in), it means you moved too fast or didn’t have enough filler metal. Take a deep breath, keep a steady hand, and move with purpose.
## Why You Might Fail the 3g and 4g welding test
Even experienced welders can fail a 3g and 4g welding test if they get complacent. The most common reason for failure is slag inclusions. This happens when the glass-like coating on the weld isn’t fully cleaned off before the next layer is applied.
Another common culprit is lack of fusion. This occurs when the weld metal doesn’t properly bond with the side of the bevel. It often looks like a thin black line on an X-ray or a crack during a bend test. It is usually caused by incorrect rod angle or low amperage.
Undercut is a visual failure. If you leave a “trench” at the edge of your weld cap, the plate is weakened at that point. Most codes, like AWS D1.1, only allow a very small amount of undercut (usually 1/32″). Anything deeper is an automatic rejection.
The Danger of Porosity
Porosity is caused by gas trapped in the weld. If you are using 7018 rods, they must be kept dry. If they absorb moisture from the air, the hydrogen will cause internal bubbles. Always pull your rods from a sealed tin or a rod oven if you are aiming for a certification.
Excessive reinforcement is also a problem. Some welders think “the bigger the weld, the better,” but if the cap is too tall, it creates a stress riser. This makes the joint more likely to snap under pressure. Stick to the height requirements specified in your test procedure.
Lastly, don’t forget the restarts. If you have a “cold start” where you didn’t get the metal hot enough at the beginning of a rod change, you will leave a void. Always start your arc about an inch ahead of the previous crater, move back into the crater to fill it, and then proceed forward.
Post-Weld Inspection and the Bend Test
Once you finish the 3g and 4g welding test, the plates are allowed to cool slowly. Do not quench them in water! Rapid cooling can make the steel brittle and cause it to fail the bend test instantly. Once cool, the inspector will perform a visual inspection.
If the visual inspection passes, the plates are cut into strips called “coupons.” Usually, you will have two coupons for each test: a root bend and a face bend. The backing strip is machined or ground off until the coupon is a uniform thickness.
The coupons are then placed in a hydraulic press and bent into a “U” shape. This stretches the weld metal to its limit. If there are any hidden defects—like slag or lack of fusion—the weld will “open up” or crack. A crack larger than 1/8″ usually results in a failure.
Preparing Your Coupons
- Radius the Edges: Use a file or grinder to slightly round the corners of your coupons. Sharp corners are where cracks start.
- Smooth Finish: Ensure there are no deep grinder marks running across the coupon. Grinding marks should run lengthwise (parallel to the bend).
- Identify Your Work: Mark each coupon clearly so the inspector knows which is the root and which is the face.
Watching your coupons go into the press is nerve-wracking. However, if you followed the proper welding procedures and kept your joint clean, the steel should stretch like taffy without breaking. A successful bend test is proof of your skill.
## Frequently Asked Questions About the 3g and 4g welding test
What is the difference between 3G and 4G welding?
3G is a vertical position weld, usually performed uphill for better penetration. 4G is an overhead position weld where the plates are above the welder. Both are groove welds, but they require different techniques to manage gravity’s effect on the puddle.
Can I take the 3g and 4g welding test with a MIG welder?
Yes, though it is less common for structural certifications than Stick (SMAW) or Flux-Core (FCAW). If using MIG (GMAW), the test usually requires a spray-transfer mode or a specific gas mix to ensure deep penetration, as short-circuit MIG is prone to “cold lap” defects.
What happens if I fail the bend test?
If a coupon fails, you usually have to wait a certain period before retesting, or you may be allowed an immediate “proctor-supervised” retest depending on the facility’s rules. It is a learning opportunity to analyze the break and see exactly where the slag or lack of fusion occurred.
Do I need to be a professional to take these tests?
No, many hobbyists take the 3g and 4g welding test to benchmark their skills or to qualify for insurance purposes on certain projects. You can find local community colleges or private testing labs that offer these certifications to the public.
Final Thoughts on Mastering the Test
Passing a 3g and 4g welding test is a badge of honor in the metalworking community. It proves that you have the patience to prep your materials correctly and the skill to control a molten puddle in the most challenging positions. It’s not just about “sticking metal together”—it’s about structural integrity.
Remember that consistency is your best friend. Practice your travel speed and rod angles until they become second nature. If you can stay calm while sparks are falling around you in the 4G position, you are well on your way to becoming a master welder.
Take your time, keep your plates clean, and don’t rush the cooling process. Whether you’re doing this for a career move or just to level up your DIY game, the discipline you learn will make every project you touch stronger and safer. Now, get out to the shop, grab some 7018s, and start practicing!
