These are some of the commonly detected defects in typical weld. All defects are discontinuities, but not all discontinuities are defects. This needs to be removed by grinding and there will be metal loss. The weld defect tolerance study presupposes that introduction of discontinuities into welds is unavoidable, regardless of type of process used or degree of care. Hobart institute welding discontinuities and defects. A discontinuity could be the result of a defect, but isnt necessarily a. Used for detection of surface and internal discontinuities drawing from welding inspection technology, fourth edition, american welding society. Improper welding technique possible cures initiate arc inside the weld joint possible causes cold welding procedures travel speed too slow travel speed too fast improper joint detail possible cures increase current use proper travel speed possible causes improper welding technique possible cures maintain constant travel speed possible causes. Hobart institute of welding technology 400 trade square e.
These interruptions may occur in the base metal, weld material or heat affected zones. Defects in rolled products a general b operational a general the defects may arise due to isurface irregularities. The various types of external defects with their causes and remedies are listed below. Defects in weld joints could result in the rejection of parts and assemblies, costly repairs, significant reduction of performance under working conditions and, in extreme cases, catastrophic failures. To obtain reliable resistance spot welds that guarantees their satisfactory mechanical performance and improved crashworthiness in the vehicle autobody, it is vital to study the causes, conditions, and welding parameters resulting in the formation of defects and discontinuities in the welds. Welding cracks can be present at the surface, inside of the weld material or at the heat affected zones. The first step toward understanding weld discontinuities is to examine some welding terminology.
As further examples of some of the reasons discontinuities and defects in metals the processing of iron ore to make still is shown in the following slides. It is however under the responsibility of the person in charge of a welding operation to strive to reduce to the minimum such occurrences what are weldingdefects. Defects in weld joints could result in the rejection of parts and assemblies, costly repairs, significant reduction of performance under working. Defect a flaw or flaws that by nature or accumulated effect render a part or product unable to meet minimum applicable acceptance standards or specifications. Weld discontinuities are interruptions ofthe typical structure ofa weldment such as a lack ofcontinuity in its physical, metallurgical or mechanical characteristics discontinuities may be found in the weld metal, the heat affected zone and the base metal. The book includes a glossary of welding terms, welding inspector responsibilities, identification and. This work studies the weld discontinuities and defects that are likely to occur in resistance spot welding of 1gpa transformation induced. Recognize the appearance of common discontinuities and the variables involved with interpretation.
Discontinuity an interruption of the typical structure of a material, such as a lack of homogeneity in its mechanical, metallurgical, or physical characteristics. Welding discontinuities defects imperfection youtube. However, a surface irregularity or weld discontinuity is not a rejectable defect when it is within the permissible range of extent according. Defects and discontinuities tim turner elizabethtown technical college. Discontinuities are interruptions in the typical structure of a material. A phenomenological study of weld discontinuities and. Various types of flaw occur in the weld metal and the heat affected zones of welded joints. This is a short clip to demonstrate welding discontinuities and defects. Visual inspection will show most large discontinuities and will generally point to other discontinuities that must be detected by another method. Wjm technologies excellence in material joining 1 discontinuities and defects in welding material joining processes such as welding, soldering, and brazing depend on temperature excursion from room to operating temperature and back to room temperature for completion of the joining process. Discontinuities, which do not meet the requirements of the codes or specifications used to invoke and control an inspection, are referred to as defects. Jul 16, 2012 this is a short clip to demonstrate welding discontinuities and defects. Weldingdefects are excessive conditions, outside the acceptance limits of deviations, which risks to compromise the stability or the functionality of the welded structure they are also called rejectable.
The handbook is arranged by discontinuity type, including appli. Weld defect free download as powerpoint presentation. This work studies the weld discontinuities and defects that are likely to occur in resistance spot welding of 1gpa transformation induced plasticity steel. The differences between discontinuities and defects. Weld defects and how to avoid them welding jobs, equipment. Apr 02, 2020 these gmaw welding defects may be the results of any of the following. Be careful of deep grind marks that run transverse to the load.
Discontinuities are rejectable only if they exceed specification requirements radiographic standards used for evaluation of weld defects. This is the most unwanted defect of all the other welding defects. Understanding the difference will let you know if you need to scrap a part, repair it or simply add more weld. The process uses shielding from an externally supplied gas to protect the molten weld pool. Some examples of welding discontinuities are shown below. Porosity, one of the most common mig welding defects, is the result of gas becoming trapped in the weld metal. The soundness of any weld depends on the type of defects and its analysis in respect to the end use of the weldments. Welding defects can be defined as weld surface irregularities, discontinuities, imperfections, or inconsistencies that occur in welded parts. Save my name, email, and website in this browser for the next time i comment. Any weld would be a defect if the welder or the quality control department rejects it and blacklists the product.
Defect a defect is a rejectable discontinuity, which occurs in. A response or evidence of a response disclosed through nde that requires. Weld may fail due to overstress, underdesign or fatigue. When a weld defect appears, its important for welders to have the knowledge to fix the situation as quickly as possible. As the presence of imperfections in a welded joint may not render the component defective in the sense of being unsuitable for the intended application, the preferred term is imperfection rather than defect. The defects in the weld can be defined as irregularities in the weld metal produced due to incorrect welding. Discontinuities that exceed established acceptance standards are termed. Evaluation of the discontinuity will determine if the discontinuity is a defect or an acceptable condition. Depending on the application, other groups may have a say. Iiw standards astm standards acceptance standards vary. Understanding the difference between welding defects and.
In this booklet, various weld defects and their origin is described at length. To purchase a copy of the complete training curriculum for this program, go to the bookstore at. Gas metal arc welding gmaw, by definition, is an arc welding process which produces the coalescence of metals by heating them with an arc between a continuously fed filler metal electrode and the work. A discontinuity is not necessarily a defect but all defects are discontinuities. Kemppi welding technology course weld defects, their causes. This work studies the weld discontinuities and defects that are. Weld defects are often caused by improper technique, parameters or equipment settings. Kemppi welding technology course weld defects, their. Imagine the many places that discontinuities and defects could be generated in this process.
Hence discontinuities defects do arise during welding. Pdf a phenomenological study of weld discontinuities and. The everyday pocket handbook for visual inspection and. Welding discontinuities and defects hobart institute of. Welding inspection handbook 4th edition details this handbook is a collective effort of many volunteer technical specialists to provide information to assist welding inspectors and supervisors in the technology and application of visual and nondestructive examination. Sep 25, 2015 most common in weld discontinuities or weld defects or weld imperfections or weld faults, or weld irregularities in weld examples lack of fusion, porosity, slag inclusion, cracks, side wall. Consequently, codes and standards developed by the american welding society specify exactly how a joint must look when the job is completed. Overlap must be removed to blend smoothly into the base metal. The guide is generally focused on the types of defects that are likely to arise in steels in strength grades up to s355 that are welded using the following welding processes. A weld defect is defined as an imperfection or group of imperfections which is outside the limits stated in the appropriate application standard whereas weld. Visual inspection can detect and aid in eliminating discontinuities that might become defects in the completed weldment. The book includes a glossary of welding terms, welding inspector responsibilities, identification and definition of weld discontinuities and defects, and common causes of. Common causes of faults in welds made by the conventional arc welding processes are briefly described.
This pocket handbook provides a convenient source for the most common base metal and weld metal discontinuities found by effective vt. Hobart institute welding discontinuities and defects youtube. Incomplete fusion a weld discontinuity in which fusion did not occur between weld metal and fusion faces or adjoining weld beads. Hobart institute of welding technology 400 trade square e troy, oh 45373. Weld with smaller electrode, sometimes must be low hydrogen with preheat. Jun 12, 2003 the first step toward understanding weld discontinuities is to examine some welding terminology. Jamaluddin, in comprehensive materials processing, 2014.
A phenomenological study of weld discontinuities and defects. Welding defects and discontinuities can form due to several reasons. Defects and discontinuities maritimeexpert website. Weld defects and how to avoid them welders universe. A defect can be considered a rejectable discontinuity. But considering the metal components, these complications can still arise. Check use of correct polarity for the consumable in question. Use correct welding technique possible causes insufficient weld metal possible cures reduce travel speed possible causes travel speed too slow. The ingot or the raw material may be having irregularities due to scaling which will get trapped in the metal and remain inside the metal surface as laps.
This workbook provides an explanation of welding discontinuities and defects in relation to welding procedure variables and will benefit welding students and professionals. Weld defects and discontinuities linkedin slideshare. Reinforcement narrow and steepsloped pointed narrow and pointed reinforcements may be caused by the following gmaw. Visual inspection costs less than any other nondestructive inspection. There are many codes depending on what type of product you are welding on. Defects and discontinuities tim turner elizabethtown technical college 2. Iiw standards astm standards acceptance standards vary with service requirements 16062015 15. These gmaw welding defects may be the results of any of the following.
Also be careful of fusion discontinuities hidden by grinding. Not all weld discontinuities are weld defects, but all weld defects are discontinuities. Most common in weld discontinuities or weld defects or weld imperfections or weld faults, or weld irregularities in weld examples. Understand the origin and nature of common discontinuities.
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