The size and kind of weld, edge preparation, metal thickness, reinforcing members, and distortion are the most essential aspects. Each of the aforementioned parameters can influence and vary the welding process. Distortion, for example, is one of the most typical problems encountered in welding manufacturing. It may occur as a result of thermal expansion or contraction, or simply because the materials being joined are different in temperature when they're placed into the joint.
Welding is the joining of two pieces of material by melting their surface layers together and allowing them to re-solidify. The heat required for this process is supplied by an electric arc or gas flame. The welding process can be divided up into several categories depending on which type of metal is being joined: steel, stainless steel, aluminum, copper, and other metals.
The quality of the weld depends on many factors such as the experience of the welder, accuracy of the equipment used, and proper selection of welding procedures. However, with knowledge of the basic principles behind welding techniques, any competent welder can produce acceptable results.
Welding is a critical technique for the joining of materials in the nation's major manufacturing industries. On the eve of the twenty-first century, the welding industry is defining its vision of the issues and opportunities that it will face in 2020. To do so, it needs to look back at how it arrived at these positions over the past decade. The following pages describe some of the significant events in this history.
Welding has been essential to the success of many American manufacturers. It provides a strong foundation for high-quality products that last longer and require less maintenance than competing technologies. In addition, welding allows manufacturers to reduce inventory costs by avoiding product redesigns after initial production runs are completed. Finally, welding is a key factor in reducing labor expenses by eliminating the need for additional employees to perform manual labor tasks.
Welding's importance to the economy is also reflected in the number of jobs it creates. In 2016, the welding industry accounted for more than 1 million jobs across all sectors of the economy. This represents about 5% of the total U.S. workforce. Welders work on assembly lines as well as in research labs and at other locations where multiple jobs have to be done quickly for projects to meet their deadlines. They also work independently, using their own skills and tools to create custom products for customers.
The following are the basic welding quality standards that must be met in order to produce such high-quality products:
Weld distortion is caused by the expansion and contraction of the weld metal and nearby base metal throughout the welding process's heating and cooling cycles. When all of the welding is done on one side of a part, the distortion is substantially greater than when the welds are alternated from one side to the other. The amount of distortion depends on several factors such as the type of metal being welded, its thickness, and the number of times it is heated and cooled.
Weld distortion is classified according to whether it increases or decreases the diameter of the tube. For example, if the tube is stretched then it is called "overetched" or "overdrawn". If the tube is compressed then it is called "undrawn". Undrawn areas may be visible after welding but they can be smoothed out during finishing operations like rolling or grinding. Overdrawn areas cannot be smoothed out this way and require further processing (such as cutting away the excess metal) before they will fit inside their parent tubes.
Overdrawing is usually not a problem unless you need to draw very small amounts of fluid into your tubes. Then, the oversize area would prevent the required amount of flow through the tube. Underdrawing is also undesirable because you will get less-than-expected yield pressures if the tube is too small. Also, if the base metal is very soft due to heat treatment or alloying elements then it may collapse under its own weight causing a hole in the tube.
The majority of welding faults are caused by poor welding methods. Once the root causes are identified, the operator may quickly resolve the issue. Incomplete penetration, incomplete fusion, undercutting, porosity, and longitudinal cracking are common defects. They can be seen using optical microscopy or scanning electron microscopy.
In this article, we will discuss four common types of weld defects: incomplete penetration, incomplete fusion, porosity, and longitudinal cracking.
Incomplete penetration is the failure to penetrate all of the layers being joined. This can cause a weak spot in the joint where the layers don't connect together. If one or more of the layers being joined is thicker than the others, then the lack of penetration into the thicker layer(s) will appear as a hollow area inside the joint. Thickness differences can also cause incomplete penetration if the welder doesn't have enough reach with their torch. Thicker materials require more heat to melt them so they should never be heated above their melting points during welding.
Incomplete fusion is the failure of some of the molten metal to completely mix with other molten metal or to completely solidify within the joint. This can cause a weak spot in the joint where the material that didn't fully fuse together creates a void inside the joint.