Some hobbyists may observe defects, such as inclusions, after they have welded a metal. Such defects may be traced to the use of an incorrect number of passes when that particular item was being welded. This article discusses some of the factors that can guide you to decide whether to use fewer or more passes as you weld.
The Travel Speed
You should match the number of passes to the travel speed that you are using. For example, a slow travel speed allows more molten metal from the welding wire to pool at a given welding site. Consequently, it may not be necessary for you to make many passes in order to be certain that the joint will fuse fully. Conversely, a fast travel speed reduces the material that is available for a strong joint to be made. More passes are therefore needed to complete the weld. Refer to the data sheets available on different welding techniques. Adjust the number of passes to suit the metal that you are working with.
The nature of the joint that you are welding can also determine how many passes you will need to make in order to form a strong weld between the pieces. For example, a V-joint can be adequately welded with fewer passes when compared to a bevel joint. This is because the V-joint has a smaller surface area to be covered when compared to a bevel joint that is larger. In other words, all the molten metal is focused in one area if it is a V-joint.
Consider the dimensions of the electrodes that you use as you weld when you are deciding how many passes will be sufficient during a welding project. Electrodes with a wider diameter deposit more material than do electrodes with smaller diameters. Thus, more passes are needed to achieve the same weld strength if a smaller-diameter electrode is used than the number of passes that can create a strong joint if a larger-diameter electrode is used.
The base metal's thickness can also influence how many passes you can make as you weld. The general rule is that thicker metals require more passes so that the weld joint can be heated sufficiently until it melts and fuses with the molten metal from the welding wire. Thin metals need fewer passes because they can easily absorb heat and fuse effectively.
As you can see, each welding task may require you to make a different number of passes from what was suitable in a previous task. Keep trying different numbers of passes until you intuitively know how to change those numbers with each task. You can also opt to reach out to a welding professional for your projects.