Testing your welds

So, you are feeling kind of secure and smug about your new found welding skills? Do your friends think you need a little whack to your confidence to bring you down? Well, having your welds tested may just be the cure! Does this sound like an ad on late night television? Honestly, it's the truth. Its hard to judge a weld by its looks. Sure, a nice looking weld will probably hold better than the one with holes and visible iceburgs of slag sticking out of the weld will, but will it hold when it counts? You can never tell what is under the surface. For beginners, the goal is often to get to the point of making a "slick" looking weld, that could rival a machine made weld. Yes, every welder wants that for his welds, even advanced ones. But there are some important foundational checks that should be performed along the way to see if the welder's technique is truly sound and progressing. This includes a method known as destructive testing. This type testing is popular in the certification process of a welder. There a couple of ways to do this to be sure, but for the beginner, the equipment may not be available to do it. There are alternative ways that can get the welder close to determining the true integrity of the weld.

One way is to weld up a 6 or 8 inch long piece of ¼"x 2" angle iron, starting in the bottom of the V and working out, laying bead upon bead. As the welding progresses, the slag is cleaned from each pass, and another is laid beside it. As the weld is built up and out, the V is slowly filled in. Once enough material has been laid in, or at least the V has been mostly filled. The V can be cut lengthwise down the middle of the welds so that the saw cuts in the middle down to the bottom, center of the V. This type cut will reveal any flaws or entrapments in the weld, and will give you a good idea of average soundess of the welds.

Another way is to try to devise a testing stand that is similar to the standard destructive testing devices that are used during certification tests. This test makes you test the weld by bending the plate across the center of the weld along the length of it. Usually a small hydraulic cylinder has a piece of rounded steel attached to the end of the piston. The cylinder moves downward between two rollers and continues to push down past the rollers. The plate is cut to fit into the press and is laid on top of the rollers. The cylinder comes down with the head in-line with the weld and begins to bend it in a shape of a horseshoe. There are many ways to mimic this type of tester, including, using a hydraulic press, or a metal bender that "wraps" the metal into a horshoe. Another crude, but efficient way of doing it is to put the plate in a vise up to the weld area, and then bend the plate in half by hammering the top edge of the plate. In destructive testing, a 3/8" plate is usually " veed " out at a 60 degree angle and welds are laid in, pass by pass, beginning with one singular weld at the bottom. The two plates are slightly separated about the width of the welding rod and ground slightly flat where they would meet or in the case of tig, barely touching with the edge sharp as a knife. This "open root" stick weld is required to achieve a 100% penetration weld. After the welds are finished, the plate is then cut into several 2 ½" wide pieces and placed in the testing device. One weld should be bent down the face side of the weld, and the other should be bent down the back side of the weld. Any breakeage, tearing or defect will appear.

Another way of testing is non destructive testing, using ultrasound or X-ray technology. This will often be reserved for critical welds, that have to be evaluated before work can proceed to the next joint. Likely you'll not have the money or the experience to buy a ultrasounding or X-ray technology...And unless your Doctor is a welder himself, you'll not get to use his equipment unless you swallowed the plate.

In all seriousness, though, take notes of what you see in your tests, on how far it was bent before failure, or how long the tear was or the number of voids that are made visible. These will help you gauge your progress, and build your confidence back. More than one smug welder has had his feelings hurt on his first weld test. You won't be alone. At least if you are at home testing your welds, only you will see them...not the whole class.