Discontinuities may or may not be considered defects. Aug 04, 2010 this feature is not available right now. Set your store to see local availability add to cart. Undercut causes a stress concentration point stress riser that is a potential starting point for weld cracking. Therefore, weld beads with a small depthtowidth ratio, such as formed in bridging a large gap with a wide, thin bead, will be more susceptible to solidification cracking, as shown in fig. The maximum distance from the face on a convex fillet weld perpendicular to a line joining the weld toes. Of more importance is the determination of the effect of weld discontinuities.
Methods to obtain weld discontinuities in spotwelded joints made of advanced highstrength steels article in welding in the world, le soudage dans le monde 551112. The differences between discontinuities and defects. Module 10 weld discontinuities and causes flashcards. May 08, 2019 a sound weld means that theres uniformity with a very little variation tolerance everywhere you see, either on weld surface or in subsurface. The examples have been chosen to illustrate the defects, and do not indicate. Mar 22, 20 those discontinuities in form of cracks might be an initial start of cracking in the spotwelded joints regarding fatigue loads. Undercut a groove melted into the base metal adjacent to the weld toe or weld root and left unfilled by weld metal. Whereas there are acceptable limits for slag inclusions and porosity in welds, cracks are never acceptable. Isolated discontinuities like clusters with sum of dimensions not to exceed chart and gap part 3 cracking cracks in a weldment are probably the most dreaded of all the weld discontinuities. Overlap the protrusion of weld metal beyond the weld toe or weld root. It is the welding inspectors function to identify these discontinuities through visual inspection and often to evaluate their acceptance, or rejection, through the use of the.
If the specified range for root opening for joint b is 3 16, what is the range of root opening permitted for this joint. Weld line occurrence in plastic injection molded parts weld lines, also commonly known as knit lines, may be present in a plastic molded part depending on the parts geometry. The crack begins at a void in the welding crater, caused by the solidi. A sound weld is the best form of the weld, it will have the ability to withstand its designed stress, which means that the quality of fusion between the weld metal and the parent metal is topnotch. Welds may contain porosity, slag inclusions or cracks. Improper welding technique arc length too long oscillation too abrupt, not spending enough time on the sides of the puddle. Defects and discontinuities tim turner elizabethtown technical college 2.
A flaw or flaws that by nature or accumulated effect render a part or product unable to meet minimum applicable acceptance standards or specifications. The everyday pocket handbook for visual inspection and. Weld cracking several types of discontinuities may occur in welds or heat affected zones. Because of the wide range of applications and the many types of materials welded, cracking is an extremely complex subject. A complete treatise on weld quality is offered in chapter of the aws welding handbook, 9th edition, volume 1, pages 534 577. The likelihood of discontinuities occurring depends on a number of factors. Weld defects and discontinuities free download as powerpoint presentation. Weld on ceramic weld metal support at high currents.
How to prevent weld solidification cracking welpedia. Joint discontinuities are shown and discussed indepth. Weld discontinuities part 3 cracking cracks in a weldment are probably the most dreaded of all the weld discontinuities. Convexity results in added stress risers at the toes of the fillet weld and increased heat input from the additional weld metal deposited assuming poor leg size, causing increased distortion. This pocket handbook provides a convenient source for the most common base metal and weld metal discontinuities found by. Module 10 weld discontinuities and causes flashcards quizlet.
Ppt defects and discontinuities powerpoint presentation. Deep narrow welds, with high depth to width ratios, are prone to centreline cracking, fig. Of the three, cracks are by far the most detrimental. A sound weld means that theres uniformity with a very little variation tolerance everywhere you see, either on weld surface or in subsurface. Structural failures precipitated by weld discontinuities fig. Will the discontinuity influence the weldment in its intended service and thus be termed a defect. Henry june 14, 2005 discontinuities, or flaws, can often occur in the welds used to manufacture welded tubular products. Since the solidification starts from fusion line to centerline, the low melting components in composition of molten weld puddle remains liquid in the center even at low temperature and as a result stresses are developed due to contraction of. Acceptance criteria of weld defects as per different codes. I have only pulled a few welds probably 10 in the last day, and messed around with 6010 and 60 cig rods, both 332. Green berets ultralight bug out bag with gear recommendations duration. Weld discontinuities part 2 unacceptable weld profiles the profile of a completed weld may have considerable affect on the performance of that weld in service. Discontinuities in weldscause and effect journal article. Weld pass a single progression of welding along a joint.
In this case, the centre of the weld which is the last part to solidify, is a narrow zone with negligible cracking resistance. Sometimes useful improvement to the weld metal composition can be obtained by selecting a wire that is particularly low in carbon, sulphur and phosphorus, so as to reduce the risk of cracking. It is of great interest to figure out, if, in comparison to specimens without weld discontinuities, the crack initiating point changes and if the fatigue resistance might be reduced by the discontinuities. Readers involved in quality are urged to obtain the book. Below is a representation of a convex fillet weld without discontinuities. Ips weldon 3 acrylic plastic cement with weldon applicator. Weld on 3 is a waterthin, nonflammable cement formulated to quickly develop high strength, clear bonds to many thermoplastic substrates, particularly acrylic.
Any weld would be a defect if the welder or the quality control department rejects it and blacklists the product. Weld discontinuities weld discontinuities are interruptions ofthe. Weld discontinuities part 2 unacceptable weld profiles. Defect a flaw or flaws that by nature or accumulated effect render a part or product unable to meet minimum applicable acceptance standards or. More information about weld discontinuities can be found in the following resources. In other cases the code states the weld with discontinuities exceeding given perameters is to be repaired. Another section of the defective weldment shown in fig. Those discontinuities in form of cracks might be an initial start of cracking in the spotwelded joints regarding fatigue loads. Weld discontinuities 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. Oct 03, 2015 the reason behind that the hot weld metal lose the required ductility and may be subjected to cracking. I have only started to stick weld yesterday and i know the basics behind rods, flux and materials. Structural failures precipitated by weld discontinuities. Intermediate weld discontinuities methods steel cwb group.
Methods to obtain weld discontinuities in spotwelded. If the specified range for root opening for joint b is 316, what is the range of root opening permitted for this joint. Weld defects and discontinuities linkedin slideshare. Weld defects and discontinuities 1 weld defects and discontinuities 2 defect. Weld pool the localized volume of molten metal in a weld prior to its solidification as weld metal. The term designates rejectability discontinuity an interruption of the typical structure of a material, such as a lack of homogeneity in its mechanical, metallurgical, or physical characteristics. This intermediate course is intended for managers, engineers, inspectors, welding supervisors, welders and other personnel responsible for the quality of welded steel products. Whip and pause opinions non structural by poland308. Weld reinforcement weld metal in excess of the quantity required to fill a joint. Crater cracks causes the welding ended far too abruptly. Solidification cracking risk reduction in submerged arc weld. The reason behind that the hot weld metal lose the required ductility and may be subjected. Weld line occurrence in plastic injection molded parts.
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. Welding discontinuities and defects hobart institute of. Table 2 discontinuities commonly encountered with welding processes incomplete incomplete joint weldingprocess porosity slag fusion penetration undercut overlap cracks. Contact information telephone 4078804945 consulting is only available for customers fax postal address electronic mail general. Weldon 3 is a waterthin, nonflammable cement formulated to quickly develop high strength, clear bonds to many thermoplastic substrates, particularly acrylic. Discontinuity an interruption of the typical structure of a material, such as a lack of homogeneity in its mechanical, metallurgical, or physical characteristics. Incomplete fusion a weld discontinuity in which fusion did not occur between weld metal and fusion faces or adjoining weld beads. Aug 04, 2010 green berets ultralight bug out bag with gear recommendations duration. All defects are discontinuities, but not all discontinuities are defects. Since the line between discontinuities and defects varies from one industry to another, only a generalized explanation can give a good guide to isolating defects from discontinuities. Some weld discontinuities, such as porosity, have acceptable limits.
Above are several different representations of weld cracking. The generation or introduction of the discontinuities in a welded structure can result when the delicate balance of welding variables is upset. The bond is achieved by first softening the surfaces to be joined and then fusing them together with dissipation of the solvent. The objective is to be able to identify and define various types of discontinuities and defects in addition to identifying and determining the common causes of those.
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