by Jason Becker
Let's face it, welding discontinuities are all a part of the learning process. We have all made them at one point in our lives while learning to weld and possibly even after we have learned.
We sit down and discuss 3 more welding discontinuities that are pretty common. Although these discontinuities are easy to avoid once you know what you are doing, it's good to know what causes them so that we can avoid them. This time we are talking about lack of fusion, slag inclusion and overlap. The first one I would like to discuss is lack of fusion, this discontinuity can be considered a defect and cause an automatic rejection during a welding qualification test. Lack of fusion is usually caused by improper work angle, we demonstrate this defect and its cause on a 3G Complete Joint Penetration (CJP) weldment. During the welding, I favor the left side of the plate as we are running the root. We demonstrate both, the proper technique as well as the most common culprit of lack of fusion.
Upon completion of the weld and after a quick cleanup, we can see that the areas where we favored the left side, of the joint we have lack of fusion on the right side of the plate. This is very common when first learning to weld and can be remedied rather quick by adjusting our work angle.
Because we are using SMAW and it is a slag producing process, we end up with slag in the area that we had lack of fusion. The slag can easily be cleaned out but if we do not clean it out, it will get trapped in the weld area and can cause a defect once the weld is inspected by RT, UT, or a bend test. It is always best to clean any and all slag out of the welding area. Most people think that they can just burn slag out of their weld, but they cant, they just cover it up. The inclusion will rear it's ugly head again during the testing process. Avoiding slag inclusions can be mitigated by adjusting your work angle just like in the lack of fusion example. Slag inclusions are not an automatic defect though, it all depends on what the specific code you are welding to allows.
The last discontinuity is overlap, this one was difficult to recreate but once again, it comes down work angle, if our work angle is exaggerated too far one way or another, we run the possibility of getting overlap. Overlap is an automatic defect and causes the weld to be rejected. This is because it can create a stress point in the weldment and lead to a crack once a load is placed on it.
As you can see, work angles play a huge role in the overall structural integrity of a weld. Focus on making the correct work angles and maintaining them throughout the weld and you should be able to alleviate these three common welding discontinuities. The video shows some great arc shots of both the proper and improper techniques as well the as the outcomes as well. Hopefully this will help you out along your way and give you a few things to think about. Until next time, Make Every Weld Better Than Your Last.