I-CAR Welding Qualification Test basics: Quality welds

The I-CAR WQT

Part 1 of 3:

PLUG WELD ON LAP JOINT

Welding is the most important skill every metal technician should possess. While the sheet metal gaps may be perfect, corrosion protection restored, the wheels properly aligned and the paint buffed to perfection, if the welds aren't high quality, the repair is substandard.

Understanding the importance of welding to the metal technician, I-CAR has provided a means for metal technicians to prove their welding skills in a performancebased test for several years. The I-CAR Welding Qualification Test (WQT) requires technicians to perform three different types of welds in both the vertical and overhead positions.

The weld types are:

* Plug weld on lap joint;

* Fillet weld on lap joint;

* Butt joint with backing.

When you sign up for the test, you will receive a CD-ROM containing a detailed overview of the testing process and an I-CAR Steel GMA (MIG) Welding Gauge.The disc also provides detailed information on the requirements necessary to pass each weld and items that should be brought by the technician on the day of the test.

Reviewing the CD-ROM is critical to understanding the testing process and to facilitate practice. According to Chris Kipp, a certified welding instructor and inspector with the Career Institute of Technology in Easton, Pa.,-an I-CAR WQT site-taking the test seriously and doing a little homework prior to arriving at the test site is critical to passing the test.

"While the technician will have time to practice before the test begins, if they have practiced at their shop, they can use the time at the test site to familiarize themselves with the equipment and perform more test welds," Kipp says.

Audie Swedeen, I-CAR's welding qualification test manager, echoes Kipp's sentiment regarding preparation prior to arriving at the test site. Swedeen says, "Most technicians fail because they don't take the test seriously and don't prepare. We also have been able to identify that many technicians have trouble with their vision and need to use reading glasses or a cheater lens in their welding hood. If you can't see the joint you can't weld it."

The following is an overview of the requirements for the plug weld on lap joint. In February's and March's issues of ABRN, we will examine the fillet weld on lap joint and butt joint with backing.

Plug Weld on Lap Joint

The I-CAP WQT requires that technicians perform a 5/16 in. (8mm) plug weld on lap joint using Gas Metal Arc (MIG) welding equipment.The plug weld is performed in both the vertical and overhead position. Technicians taking the test will be provided the necessary coupons with holes punched to perform the test.

For the plug weld in the vertical position:

1. Locate a coupon that has one 5/16 in. (8mm) hole punched in the corner.

2. Hold the coupon with the hole with the long edge horizontally and the other coupon vertically and lap the coupon with the hold over the other coupon. Clamp the coupons together.

3. Secure the coupons you assembled into the holder in the vertical position. Note that tack welds are not allowed.

4. Perform the weld.

5. Visually inspect the completed weld joint.

During the examination, you will perform each of the three welds in the vertical position, then you will be given additional coupons and time to perform the same three welds in the overhead position. For the plug weld in the overhead position, the procedure is the same except that the coupons you assemble will naturally be put into the holder with the hole facing down.

Visual Inspection

Visual inspection is the first step used to determine if the weld meets the requirements of the qualification test.When practicing, perform a visual inspection and keep the specifics mentioned below in mind. If a weld fails visual inspection, it fails...no destructive test will be performed.

First, remember that size matters. On the face side of the assembled coupons, the plug weld must completely fill the hole in the coupon. The plug weld nugget must be from 3/8 in. (10mm) to 1/2 in. (13mm) in diameter. A plug weld too small or too large will fail the visual inspection. Use the gauge provided by I-CAR to check the diameter of your weld.

Also, the face of the weld should not exhibit any undercut, cracks, porosity, skips or voids. The height of the bead on the face of the weld should be no greater that 1/18 in. (3mm) above the surface. To check height, use the gauge provided.

On the backside of the weld, ensure there is no burn-through that creates a hole.There should be no melt-through greater than 3/8 in. (10mm) in diameter or 1/16 in. (1.5mm) on the bottom side. There should be a ripple in the bottom coupon that is an indicator of good penetration.

Destructive Testing

Providing your weld passes visual inspection, it will then be tested destructively. To do this during your practice sessions, position the completed assembly in a vise with the weld facing away from you. The long edge of the top coupon should be placed in the vise so that the bottom coupon just touches the top of the vise.

Hammer the coupon away from you, forming a 90 degree bend along the length of the coupon.

Remove the coupons from the vise and reposition them with the weld facing to the front and the top coupon pointing up. Again, hammer the coupons away from you forming a 90 degree bend.

Next, use both hands to twist the top coupon off of the bottom one, keeping the coupon parallel to the bench. The nugget hole it the bottom coupon should measure at least (5mm) 3/16 in. to pass the test.

Next month, we will examine the step-by-step procedures to produce the fillet weld on lap joint.

[Author Affiliation]

By Russell Thrall III

Editor In Chief