Passing the 3G and 4G Stick Plate Tests

The 3G and 4G plate tests are where a lot of stick welders either move up or get stuck. A 3G coupon is welded in the vertical position, and a 4G coupon is welded overhead. Together they open the door to all-position plate work. Both test whether you can put sound metal into a groove when gravity is working against you, with someone watching the clock. Most failures are not bad luck. They come from lack of fusion and trapped slag you could have found in practice.

This is a plan for preparing for those tests. Passing a test still requires a witnessed test at a real facility, under a real code, and your record only covers what you actually tested. Test details vary by code, facility and employer. Limits below reflect published summaries of AWS D1.1, and you should confirm them against your facility's test document and the current edition.

What You Will Be Able to Do

• Explain what 3G and 4G cover, and what they do not.
• Plan a coupon pass by pass.
• Build a practice routine that matches the real test.
• Read a failed bend strap and trace it to a cause.
• Handle test day, and know what your options are after a failure.

What the Tests Cover

Under AWS D1.1, a 3G plate groove test generally covers flat, horizontal and vertical. A 4G test covers flat and overhead. Holding both covers all positions on plate. Other codes differ. ASME Section IX, for example, has its own coverage tables.

Thickness matters as much as position:

So if your employer welds 1 inch plate, a 3/8 inch test may not be enough. Backing matters too. A test with backing usually does not qualify you for open-root joints with no backing. Before you book a test, write down what your employer actually needs: process, rod, position, thickness and backing. Then match the test to that list.

Know the Test Before You Practice

Ask your test facility these questions up front:

1. Which code and edition applies?
2. Which plate thickness, bevel and root opening will I use?
3. Is it with backing, or open root?
4. Which rod and size? Can I use more than one size?
5. Is the test graded by bend test or radiography?
6. May I grind? On which passes?
7. May I use a stop-and-start plan, or is there a rule on restarts?
8. What is the time limit?
9. What happens if I fail?

A common D1.1 coupon with backing uses a 22.5 degree bevel on each plate, for 45 degrees included. It has a 1/4 inch root opening, no land and a backing strip. Check this against your test document, and practice on exactly that joint.

Pass Planning

Do not just start welding and see what happens. Write a plan for your coupon, and keep notes on it. Here is an example for a 3/8 inch coupon with backing, using 1/8 inch E7018. Your count may differ.

The last fill is the key to a good cap. If you fill the groove to the top, you lose the edges that guide you, and the cap comes out high and wide. Leave a little room.

Keep each pass flat or slightly hollow. A humped bead leaves sharp valleys at the sides. Slag packs into those valleys, and the next pass cannot melt it out. If a pass comes out humped, grind it down if you are allowed.

The 3G Coupon

1. Tack and set it. Position the coupon at the height you can work at, and do not move it again.
2. Root. Reach both bevel corners and the backing. The bevel corner is where lack of fusion hides.
3. Clean each pass. Chip, brush and look. Any slag you can still see will be there after the next pass.
4. Watch your weave. Pause at the sides, and move quickly through the middle.
5. Plan your rod changes. Stop at a spot you can reach well, and restart with care.
6. Keep the heat under control. A hot plate makes the puddle run. Let it cool if the rules allow. Check for an interpass limit.

The most common 3G fault is an arc that drifts away from the bevel wall. If you do not put the arc on the sidewall, you get a bead sitting on cold steel. It looks fine, and it opens up on the bend.

The 4G Coupon

1. Set your body first. Get your feet, shoulder and lead right. Support your arm if you can. Practice the full length of the coupon without an arc.
2. Root. Run a stringer on each bevel corner, or as your plan calls for. Keep the puddle small.
3. Build with stringers. Overlap by about half, and work across the groove in an order that keeps each bead tied to the last.
4. Clean every bead. With more beads come more places to trap slag.
5. Cap. Use overlapping stringers, and keep them even. Run the outer beads first if that helps you hold the groove edge.

The most common 4G fault is too much rod feed and heat, which gives a sagging, ropy bead with slag trapped at the toes. Keep the puddle small, and keep moving.

Warning: Overhead practice drops hot slag and spatter on you. Wear leathers, a cap and closed cuffs and collar. Protect your ears, and keep your head out of the rising fume.

Practicing Like the Test

• Use the same stand. Clamp the coupon at the true angle and at a working height. Practicing a 3G flat on the bench does not count.
• Use the same material and rod. Practice with the same thickness, bevel and rod size.
• Keep a coupon log. Record the date, settings, weather or shop conditions, and the result.
• Time yourself. Do at least some practice under the real time limit.
• Bend your coupons. A good-looking cap tells you little. If you have access to a jig, bend your practice coupons.
• Have someone watch you. Another welder may see a habit you cannot.
• Practice bad days. Weld when you are tired, or with a stiff lead. Test day rarely goes as planned.

Do not book the test on the strength of one good coupon. Wait until you pass bend tests in a row.

How the Coupon Is Judged

Visual first. Published summaries of D1.1 list these limits for qualification test welds. Your test document governs.

If you fail visual inspection, the coupon is usually not bent.

Then the bend test. Straps are cut and bent around a mandrel so that the weld stretches. Thinner coupons usually get a root bend and a face bend, and thicker coupons get side bends. The stretched surface is checked for open discontinuities.

Worked Example: Judging a Bent Strap

Published D1.1 summaries give these limits for the stretched surface:

• No single open discontinuity over 1/8 inch.
• Discontinuities over 1/32 inch and up to 1/8 inch add up to no more than 3/8 inch.
• Corner cracks are limited to 1/4 inch, or 1/8 inch if they are tied to slag or lack of fusion.

Strap A shows openings of 3/32, 1/16 and 1/32 inch.

• None is over 1/8 inch.
• The 1/32 inch opening is not over 1/32 inch, so it does not count.
• 3/32 + 1/16 = 5/32 inch, which is under 3/8 inch.
• Strap A passes.

Strap B shows one opening of 5/32 inch.

• 5/32 inch is over 1/8 inch, or 4/32 inch.
• Strap B fails, even though its total matches Strap A.

Size and total are separate tests. One large flaw can fail a strap that would pass on total length.

Reading a Failed Strap

A failed strap is useful data. Look closely at what broke, and where.

Check where the flaw sits against your pass plan. If it lines up with a rod change, the problem is your restart and not your overall technique.

Test Day

1. Bring what the facility allows. Tools, chipping hammer, wire brush, and approved rods if you supply them.
2. Stamp or mark your coupon. Do it as the facility tells you.
3. Check the machine. Run a scrap plate if you are allowed. Machines and leads differ.
4. Follow the rod rules. Use only rods from the facility's oven or from a fresh sealed can, as instructed.
5. Keep the coupon in position. Moving it, or welding it in the wrong position, can void the test.
6. Stick to your plan. This is not the day to try a new technique.
7. Ask before you grind. If the rules are unclear, ask the inspector first.

If You Do Not Pass

Find out the retest rules in advance. Older D1.1 text allowed an immediate retest of two welds of each failed type, and all retest specimens had to pass. Otherwise, a complete retest followed further training or practice, with evidence of that training. Some facilities do not offer an immediate retest at all. Check your current edition and your facility's policy.

Whatever the rule, do not rush back in without knowing why you failed. Get the straps if you can, read them, and practice the fix.

After You Pass

Your record lists what you tested, and it is limited to those conditions. Keep your own copy. Many codes require you to keep using the process, and a gap of more than about six months can lapse your qualification. Log your work so that you can prove it. If you lead a crew, check each welder's record against the actual joint before they start.

Common Mistakes

• Booking the wrong test. Thickness and backing matter as much as position.
• Skipping bend tests in practice. You find out about fusion on test day.
• Filling the groove to the top before the cap. The cap gets high and wide.
• Humped passes. They trap slag in the valleys.
• Moving the coupon. It can void the test.
• Retesting without a cause. You can fail again the same way.

Check Your Understanding

You hold a 4G test on 3/8 inch plate with backing. Your new job needs overhead fillets on 1 inch plate. What do you check?

Your record's thickness range, as well as your position coverage. A 3/8 inch test generally stops at 3/4 inch, so you need to check whether fillets are covered differently, or if a thicker test is needed.

Your strap has openings of 1/8, 1/8, 1/8 and 1/16 inch. Does it pass under the limits above?

No. None is over 1/8 inch, but they add up to 7/16 inch, which is over 3/8 inch.

Three straight practice straps open along the same bevel, on the same side. What does that tell you?

The same bevel is getting too little heat, so you probably have a lack of fusion from your body position or rod angle on that side. Change how you reach that wall and bend another coupon.

Your cap on a 3G practice coupon keeps coming out too high. What should you change first?

Your last fill pass. Leave it about 1/16 inch below the surface, so that you can see the groove edges and the cap has room.

Key Takeaways

• Match your test to the position, thickness and backing that your job needs.
• Plan the coupon pass by pass, and keep each pass flat.
• Practice in the true position, on the same joint, and bend your coupons.
• Leave the groove edges showing for the cap.
• Read a failed strap to find the real cause.
• Keep your record, and keep your qualification active.