Module 10 weld discontinuities and causes flashcards. Weld discontinuities part 3 cracking alcotec wire corporation. Undercutting gmaw welding defects may be caused by any of the following. These interruptions may occur in the base metal, weld material or heat affected zones.
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. Introduction when discontinuities are discovered in aluminum welds, the question of whether or not to repair weld must b e addressed. Surface profile induced cracking welds that are concave are susceptible to centerline cracking due to their reduced effective weld throat. Weld metal alloyed as much as, or more than, parent steel, usually in thick sections with insufficient consumable drying or preheat. Fillet weld a weld of approximately triangular cross section that joins two surfaces approximately at right angles to each other in a lap joint, tjoint, or corner joint.
Hi i have been welding 2 pieces of stainless steel 304l with the thickness of 0. Below is a representation of a convex fillet weld without discontinuities. Aug 19, 2014 cracking can be caused by a multitude of conditions, but the more common causes are. Defects hydrogen cracks in steels identification twi. A welding defect is any flaw that compromises the usefulness of a weldment. Underbead cracks are cold cracks that form in the haz when three conditions are met. Welds may contain porosity, slag inclusions or cracks. This leads to both the heat affected zone haz and the weld metal corroding faster or slower than the base metal. This problem is time consuming and costly in most cases. Thin parts discontinuities show up darker most exposed and weld reinforcement shows up as a lighter region figure 43. Effect of weld discontinuities on fatigue of aluminum butt joints. Poor fitup excessive root gap in fillet welds markedly increases the risk of cracking. Weld discontinuities part 1 porosity incomplete fusion incomplete penetration x this site uses cookies and other tracking technologies to provide you with our services, enhance the performance and functionality of our services, analyze the use of our products and services, and assist with our advertising and marketing efforts. Causes include instantly reducing the welding power which causes the puddle to cool too quickly and removing the filler rod too quickly at the end of the weld.
This can range from grinding and wire brushing to merely wiping the part with a rag moistened with the cleaner remover. Henry june 14, 2005 discontinuities, or flaws, can often occur in the welds used to manufacture welded tubular products. When tig welding, you want to choose torch consumables that offer both consistency and durability. Weld discontinuities part 3 cracking cracks in a weldment are probably the most dreaded of all the weld discontinuities. In fact several codes and hydrogen procedures call for the inspection of the part hours or days after the weld was performed to allow for creep and hydrogen. Weld discontinuities part 2 unacceptable weld profiles. 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. Contact information telephone 4078804945 consulting is only available for customers fax postal address electronic mail general. For the purposes of this section, cracking will be dis. Crosscheck cracks on some hardfacing applications may be ok, but in general, if a weld cracks its a big problem. I got these cracks that i want to know why, and what should i do differently next time.
Aws defines a discontinuity as an interruption of the typical structure of a weldment. Discontinuities are interruptions in the typical structure of a material. The examples have been chosen to illustrate the defects, and do not indicate. Defects and discontinuities 1 defects and discontinuities tim turner elizabethtown technical college 2 defect. The surface needs to be free of dirt, rust, scale, paint, oil, and grease, and be smooth enough to wipe off the. Residual stress in a weld can be larger than expected if it contains weld discontinuities such as incomplete fusion, incomplete joint penetration, overlap, undercut, slag inclusions, and porosity. The differences between discontinuities and defects. To fully understand weld discontinuities, we must first examine some welding terminology. A weld s ductility may decrease with a high carbon equivalent and a high cooling speed after solidification.
Conversely, if the weld is excessively convex the surface of the weld will. The likelihood of discontinuities occurring depends on a number of factors. Apr 28, 2020 n ot all weld discontinuities are weld defects, but all weld defects are discontinuities. Detecting discontinuities through weld inspection matching the inspection method to the welding process by sharon m. Discontinuities, which do not meet the requirements of the codes or specifications used to invoke and control an inspection, are referred to as defects. The first step toward understanding weld discontinuities is to examine some welding terminology.
Detecting discontinuities through weld inspection matching. There are many codes depending on what type of product you are welding on. Defects and discontinuities tim turner elizabethtown technical college 2. Both solidification cracking and hot cracking refer to the formation of shrinkage cracks during the solidification of weld metal, although hot cracking can also refer to liquation cracking solidification cracks can appear in several locations, and orientations, but most commonly are longitudinal centreline cracks coincident with the intersection of grains growing from opposite. 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. Residual stress in a weld can be larger than expected if it contains weld discontinuities such. Globular, volumetric, 3d discontinuities, porosity, or inclusions usually are found deep inside the weld. A flaw or flaws that by nature or accumulated effect render a part or product unable to meet minimum applicable acceptance standards or specifications.
Ppt defects and discontinuities powerpoint presentation. The generation or introduction of the discontinuities in a welded structure can result when the. Porosity is a collective name describing cavities or pores caused by gas entrapment in molten metal during solidification. N ot all weld discontinuities are weld defects, but all weld defects are discontinuities. We will examine some basic theory and characteristics of different types of cracking in welded connections. Cracks will occur in the weld metal when localized. Structural discontinuities in the weld or on the surface defective properties mechanical or chemical dimensional defects happen because of poor. Codes and standards define the quality necessary to achieve the integrity and reliability of the weldment. In rt, you pass gamma rays or x rays through the material. It is caused by the diffusion of hydrogen to the highly stressed, hardened part of the weldment. Overlap the protrusion of weld metal beyond the weld toe or weld root.
The maximum distance from the face on a convex fillet weld perpendicular to a line joining the weld toes. The design strength of a fillet weld is always based on the throat dimension because. Definitions discontinuity an interruption crack, forging lap, seam, inclusion, porosity, etc. Weld discontinuities can prevent a weld from meeting the minimum quality requirements.
These weld deficiencies may be caused by any of the following. 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. Weld defects and discontinuities 1 weld defects and discontinuities 2 defect. Weld cracking several types of discontinuities may occur in welds or heat affected zones.
Cracks are perhaps the only discontinuity for which there is no allowance. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Internal stresses will place the weld under tension which, with its reduced throat, may not be able to resist the stresses imposed by the adjacent base metal and crack. The toe of the 1438 fillet weld let go and cracked the entire length of the weld. Cases of uniform corrosion across the base metal and weld metal, or the base metal corroding and the weld metal remaining unaffected. Consumables comprise only a small portion of the total cost of tig welding, but they are an important factor in creating quality welds. Visual inspection and weld discontinuities causes and. Discontinuity is defined as an interruption of the typical structure of a material, such as a lack of homogeneity in its mechanical, metallurgical, or physical characteristics.
Any weld would be a defect if the welder or the quality control department rejects it and blacklists the product. Cold cracks are formed along the weld and fusion line, as a rule, after welding. Weld discontinuities part 1 porosity incomplete fusion incomplete penetration as a welding inspector, in order for you to successfully conduct your profession, it is important to understand weld discontinuities. Weld discontinuities weld discontinuities are interruptions ofthe.
Start studying module 10 weld discontinuities and causes. Above are several different representations of weld cracking. Craters, such as the one shown in figure 5a, typically occur at the end of the weld, and they often lead to cracking. Incomplete fusion a weld discontinuity in which fusion did not occur between weld metal and fusion faces or adjoining weld beads. Whereas there are acceptable limits for slag inclusions and porosity in welds, cracks are never acceptable. Of the three, cracks are by far the most detrimental. Metallurgical discontinuities cracks fracture type discontinuities characterized by a sharp tip and a high length to depth ratio fissures small cracklike discontinuities with only slight separation of the fracture surfaces fisheye discontinuity found on the fracture surface of a steel weld consisting of a. Visual inspection and weld discontinuities causes and remedies. Root cracks start at the root and extent part way into the weld. Im a cwi working at a company for less than 3 months. They use primarily saw, which i have pretty limited experience with. Cracking that occurs in the basemetal or heat affected zone of restrained weld joints 9.
I have had it drilled in my head over the years that repairing of weld discontinuities should always be done with a lowhydrogen process. Understanding why your welds crack part i welding answers. A sound weld means that theres uniformity with a very little variation tolerance everywhere you see, either on weld surface or in subsurface. Pdf a phenomenological study of weld discontinuities and. Understanding the difference will let you know if you need to scrap a part, repair it or simply add more weld. Effect of weld discontinuities on fatigue of aluminum butt. Weld discontinuities part 1 porosity incomplete fusion. The generation or introduction of the discontinuities in a welded structure can result when the delicate balance of welding variables. A radiographic film is placed on the opposite side of the joint to provide a picture of the inside of the weld. Learn how to weld pipe, structural steel, mig, tig, stick, flux core and more. Contaminants, moisture, or inadequate shielding may be the cause.
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. As a welding inspector, in order for you to successfully conduct your profession, it is important to understand weld discontinuities. Several types of discontinuities may occur in welds or heat affected zones. This work studies the weld discontinuities and defects that are likely to occur in resistance spot welding of 1gpa transformation induced plasticity steel. As shown by experiments and calculations, some defects can be permitted. Undercut a groove melted into the base metal adjacent to the weld toe or weld root and left unfilled by weld metal. Cracking can be caused by a multitude of conditions, but the more common causes are. Typically show up in firstpart manufacture or after service failure. There are three factors which combine to cause cracking.
Aug 04, 2010 this feature is not available right now. Module 10 weld discontinuities and causes flashcards quizlet. Following are descriptions of some of the basic weld discontinuities. Crater and weld incomplete penetration incomplete fusion porosity. Weld face, toes attop andbottom ofphotograph 10 11 i. Most common in weld discontinuities or weld defects or weld imperfections or weld faults, or weld irregularities in weld examples. 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.
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. In this case, the centre of the weld which is the last part to solidify, is a narrow zone with negligible cracking resistance. In low alloy steels, the cracks can be transverse to the weld, perpendicular to. Jun 12, 2003 the first step toward understanding weld discontinuities is to examine some welding terminology. Weld discontinuities part 1 porosity incomplete fusion incomplete penetration. Discontinuities in weldscause and effect journal article. 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. Preparation and fit up the size and shape of completed welds the finished. The crack starts at the fusion line and extends up through the weld.
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