Craters and cracks can occur at the end of a weld stopping point. This article describes some of the most common mig welding defects, such as porosity, lack of fusion and burn through and how to identify them by weld bead appearance. Welding defects can be defined as the irregularities formed in the given weld metal due to wrong welding process or incorrect welding patterns, etc. However, tig welder parts, such as the welding electrode, still need to be properly cleaned and polished between usesespecially when welding stainless steel. Tig welding is performed on stainless steel and other corrosionresistant metal alloys. With robotic welding equipment, tig welding can be a bit lowermaintenance, since the welding electrode isnt being constantly consumed by the welding process. Porosity in welding porosity, one of the most common mig welding defects, is the result of gas becoming trapped in the weld metal. Arc welding processes 4 welding terms 5 migmag welding 6 tig welding 10 plasma welding 17 welding sheet 18 welding plate 20 welding pipes 22 defects in welds 24 the right gas. Rework robs the company of precious time and material that is, money, so prevention is the primary concern. A welding defect is any flaw that compromises the usefulness of a weldment.
Like another welding process, mig welding has some complications. In mig mag welding, use a sufficiently high welding current level which is supported by the appropriate arc voltage for the application when using a joint configuration with a root gap, make sure it is of adequate width and does not close up during tacking and subsequent welding. The starting and stopping points are common areas for weld defects to arise. Of the three, cracks are by far the most detrimental. It can occur in weld metals and the heataffected zone. On this channel you can get education and knowledge for general issues and topics. Some of the most common weld defects are porosity, lack of fusion and burn through, with aluminum presenting a few more welding challenges than steel. The solution to this mig welding defect is to slow down your rate of travel as when get to the end of your joint. It happens when you pull from the weld prior to the weld crater becoming solid. If defects are detected, adjust the welder and welding technique, and repeat the test welds before welding on the vehicle. The size of a fillet weld is determined as shown in page 5. Common mig welding defects, their causes and solutions. During phase changes and thermal shrinkages, diverse parts of the weld joint cool at different rates and introduce strain. Another potential solution is to reduce the arc gap.
In mig welding, always check the flowmeter setting before starting your first weld, and make sure the gas mixture argon, co2, etc. Welding defects can be welding processprocedurerelated, or related to the chemical composition or metallurgy of the alloys being welded. The metal inert gas mig or metal active gas mag welding is a semiautomated process, widely used in many sectors of industry, such as shipbuilding, railroad construction and the production of heavy plants and machinery. Get solution for your common weld defects mainly in gmawmigmag welding. Crater cracks occur when a welding arc is broken, a crater will form if adequate molten metal is available to fill the arc cavity. There are some that are morelikely to appear than others but that is depending on the gas and power range that is being applied.
What happens is the weld puddle goes into the base metal that has not been welded yet. In this short article we will discuss some mig welding defects that occur frequently and also how to avoid or fix these problems. Weld cracking several types of discontinuities may occur in welds or heat affected zones. Almost all metals such as carbon steel, lowalloy steel, austenitic stainless steel, nickel alloy. It saves time and money including the use of remote visual inspection rvi, xrays, ultrasonic testing and liquid penetration testing. However, knowing these complications will help you to protect the machine from problems and their solution. What is the welding defects for mig welding answers. Gas metal arc welding gmaw, sometimes referred to by its subtypes metal inert gas mig welding or metal active gas mag welding, is a welding process in which an electric arc forms between a consumable mig wire electrode and the workpiece metals, which heats the workpiece metals, causing them to melt and join. Kemppi welding technology course weld defects, their. In a previous post, we discussed how the tensile strength test of the weld metal would generate the same result regardless of using mig or tig welding techniques. Cracks are the most severe of all weld defects and are unacceptable in most circumstances. A cold lap occurs when when the base metal is not melted well enough. The overriding cause of solidification cracking is that the weld bead in the final.
The uni en 65201 standard specifies that there are two types of errors. Porositygas flow too low or too highblocked nozzleleaking gas lines. Porosity, one of the most common mig welding defects, is the result of gas becoming trapped in the weld metal. This assumes there are no weld defects in either method. But first, i hope by now you have enough mig welding tips to get started welding properly. When a weld defect appears, its important for welders to have the knowledge to fix the situation as quickly as possible. Weld defects and how to avoid them welders universe. Welding defects may occur either outside or inside the weld metal. Radiographic testing of welds principle and procedure. How to compare and choose between mig and tig welding. Mig welding common welding defects engineer student. According to the american society of mechanical engineers asme, causes of welding defects can. Hic in the haz is often at the weld toe, but can be under the weld bead or at the weld root.
Cracks dont always happen immediately after welding, and certain cracks, such as the underbead variety, may not be open to the weld surface. What is welding defects types, causes and remedies. The defect may differ from the desired weld bead shape, size, and intended quality. Arc energy plasma spread across the conical region to make the edge of the weld be clean, but it also causes defects due to lack of flow for the weld edge. While they can occur with all arc welding processes, they are more prevalent with processes that are capable of higher deposition rates and producing larger weld puddles i. The cause of this defect is usually deformities in the structure of steel. Typical minimum fillet weld details for slipon flanges and socketwelding components are also shown on page 5.
Typical weld defects found in mig welding are lack of fusion, burn through, crater crater cracks, undercut and porosity in the weld metal. Whereas there are acceptable limits for slag inclusions and porosity in welds, cracks are never acceptable. Cracks cracks can occur just about everywhere in a weld. We will provide full details and deep knowledge of every defect, like its definition, how to detect and identify the defect, acceptancenon acceptance, root cause reason of defect prevention and repairing. It is an approach to testing that involves evaluating the weld without causing damage. Here you can also check out our guide on mig welding defects troubleshooting. Certified welding inspectors often find these little holes in xrays and ultrasound testing. These gmaw welding defects may be the results of any of the following. They are a common, and costly, cause of downtime and lost productivity. Oerlikon can provide a wide range of migmag welding inverter and step controlled power sources citowave, citosteel.
Here im going to tell you about some common mig welder troubleshooting, you can boast the quick fix to your welding defects. Defects of welding defects are those which can be theoretically eliminated, such as cracks, lack of fusion, slag inclusions, porosity and undercuts only when we understand the nature of these defects and why they occur, can we eliminate them 4. Manual welding is a technique which requires significant skill and dexterity. In fillet welds cracks are normally parallel to the weld run but in butt welds cracks can be transverse to the welding direction. Mig welder troubleshooting guide know the troubles and. In this video we will discuss about welding defects. The most common mig weld defects on aluminum and steel and. Inadequate shielding gas coverage is among the biggest culprits, and this can be addressed in several ways.
These materials are very sensitive to the presence of hydrogen, air, water, and oxygen. Migmag welding 30 flux cored electrodes 33 tig welding 34 oxyfuel gas cutting 37 plasma cutting 44 safety always 46. The penetration depth of this type of deformation is deeper than that of welding with the same grade but lower than that of a higher. Yet one thing holds true regardless of the application or material on which they occur. Weld metal porosity is a cavitytype of welding defect formed by gas entrapment during solidification as a result of contamination by certain gases, such as hydrogen, oxygen, or nitrogen. Our welding consumables were widely used in pressure vessels, bridges, ships, vehicles, petroleum and chemical industries, heavy. Hot crack can be defined as cracking formed at high temperatures near the solidus of the metal, where the metal has coherence but is completely brittle. Cold cracks can occur in both butt welds and fillet welds. Thus, as welding progresses the welding electrode becomes shorter. The electrode rod is melted at the tip of the arc and metal droplets fall into the weldpool. The welder is responsible for the defect when it is due to his or her skill level or weld deposition technique. In most welds, quality is tested based on the function for which it is intended.
The most serious type of welding defect is a weld crack and its not accepted. These impurities in the atmosphere can interact with a weld puddle and cause defects such as cracks, reduced corrosion resistance, carbide precipitation, and brittleness. How to do dye penetrant testing of welds welding defects. Welds may contain porosity, slag inclusions or cracks. First, check the regulator or flow meter for adequate gas flow, increasing it as necessary. Again, these weld crater shrinkage cavities are a naturally occurring phenomenon found in arc welding. The operational control and the skill of the operator make the difference in the welds.
There are several common gmaw welding defects including. Classification of welding defects using gray level histogram techniques via neural network article pdf available december 2014 with 2,235 reads how we measure reads. Weld defects are often caused by improper technique, parameters or equipment settings. We mainly export various of welding electrodes,migtig welding wire, fluxcored welding wire,submerged arc welding wire flux, welding consumable production line etc. This turbulence allows air to penetrate the shield, this then means you do not have an adequate gas shield around the weld pool. Classification of welding defects one of the iiw documents classifies all welding defects into six groups according to their appearance.
Metal inert gas mig and metal active gas mag welding are gas metal arc welding gmaw processes that use heat created from a dc electric arc between a consumable metal electrode and a workpiece which melt together to create a weld pool that fuses to form a join. These cracks appear after the weld has been completed and the temperature of the metal has gone down. We01a uniform gma mig plug weld procedures for upcr. Typical cold cracks that can occur in fillet welds are illustrated in figure 1. Porosity in welds leads to cracks, sometimes visible, sometimes not. Some of the defects may be allowed if the defects are under permissible limits but other defects such as cracks are never accepted.
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