Testing Your Welds
Not everyone has access to a welding school or a local union hall to get experience in welding. But nearly every one that has enough to scratch together a welder and a few shop tools can begin to learn how to weld, even if formal education is unavailable.
One of the things that is necessary for you to learn is devise some way to determine if the welds you are making are sound and trustworthy. Obviously in school classes, and training centers, they have all the testing equipment they could ask for. But in most people’s lowly shop conditions, there is limited testing equipment available. However, there is more than meets the average eye. Most hobbyists tend to have the basic tools needed to perform satisfactory tests on their own welds. Test plates (also referred to as coupons) only need to be made out of flat bar either ¼” or 3/8” by two inches wide. A traditional test plate is either 6 or 10 inches long. Simply cut the flat bar into one of these two lengths. Grind and bevel one edge to at least a rough 30 degrees, and tack weld two plates together with the edges pointed to each other so that the plates form a V groove. Be sure to leave a slight open space between the two plates. Typically, the width of the electrode itself, not counting the flux is a good starting point. This plate can be welded up, not all at once, but in a series of multiple welds. Once the test plates are welded, a good hammer and a sound vise is all that is required to perform a test.
Simply cut the plate in to two- 2” wide strips leaving edges out of the welded area. Grind the plates smooth on the front and back so the welds are flush with the metal, and the sharp edges of the plate are gently chamfered. Check to see if you have any visible flaws that are apparent. At this point it is important to look closely for any porosity or slag peeking through. Then tighten the first coupon in the vise until the weld is just above and parallel to the jaws. Begin to hammer the edge of the coupon and begin to bend the weld toward the top side of the weld. Bend it until it folds half way over or until you see cracks or tears in the metal. Take the next coupon and bend it the opposite way. Examine the plates for flaws and defects in the weld.
Though this is not an official coupon for testing welds, you can determine whether or not the coupon passed by looking at the total amount of inclusions, tears etc, and seeing if you have more than 1/8” of an inch total flaw. If you do, then you should examine the weld to see what type of flaws you have, and redo the test plates until you have less than 1/8” of total flaws. If this is difficult or you are unable to get a decent bend, try placing the coupons in a band saw and cut one coupon across the length of the weld, (down the middle of the weld). Then cut the other in several strips (if possible) at a 90 degree angle to the weld. You can then see any pockets of trapped slag or visible inclusions in the weld.