Resistance spot welding is used frequently as a successful joining method for a variety of work commonly in automotive and other manufacturing. Resistance spot welds are found typically on flanges, staggered in a single row of consecutive welds. Diameter of the electrode contact surface should be. Haz softening caused by martensite tempering is observed under strong welding parameters. The greatest technical requirement of resistance spot welding is to ensure that the process is correctly setup in the first instance. Weld defects and how to avoid them welders universe.
Vehicle manufacturers use resistance spot welding in the factory. Welding defects are easy to occur during resistance spot welding of dp600 steel sheets due to its rich chemistry. This international standard specifies requirements for resistance spot welding in the fabrication of assemblies of uncoated and metallic coated low carbon steel, comprising two or three sheets of metal, where the maximum single sheet thickness of components to be welded is within the range 0,4 mm to 3 mm, for the following materials. The weldhelp resistance welding troubleshooting guide is written for operators and engineers to help diagnose and solve common spot welding defects and issues, projection welding and seam welding applications. Resistance spot welding is a very fast and reliable process that is readily automated and does not require much operator skill. Weld defects and how to avoid them welding jobs, equipment. Low carbon steel is most suitable for spot welding. Cracking phenomenon in spot welded joints of austenitic stainless steel 657.
Analysis of welding defects in spot welding process ui curves. Introduction welding is the process of coalescing more than one material part at their surface of contact by the suitable application of pressure or heat or both at the same time. These defects reduce the mechanical performance of spot welds, in particular under dynamic loads 10. Welding defects are generated in a welding job due to the faulty or poor technique used by the inexperienced or unskilled welder or due to fundamental difficulties in the welding operation. Pdf on apr 12, 2019, bineeth benny and others published weld defects find, read and cite all the research you need on researchgate. One general criterion of resistance spotwelding is that the weld shall have a nugget diameter of 5t 12, t being the thickness of the steel sheet. The main defects in laser welds in both steel and aluminium are solidification cracking also called hot cracking or centreline cracking and porosity. Elements such as sulphur and phosphorous cause solidification cracking to occur, 1 but. Recently the problems of resistance spot welding rsw. Spot and projection welding artech welders private limited took roots in 1994 with the dream of manufacturing capacitor discharge cd projection welding machines. Weld defects in austenitic stainless steel sheetseffect of.
Spot weld nugget is generally hidden between two sheets. In spot welding the welding control and welding parameters are decisive for durability. The fatigue crack appears to be initiated near the weld notch tip. This is the most unwanted defect of all the other welding defects. An ideal weld or good weld should be such that adequate fusion exists between the filler metal and edge preparation together with good penetration. Guidelines for resistance spot welding miller welding. Project title reduced the welding defects using six sigma techniques. This work studies the weld discontinuities and defects that are likely to occur in resistance spot welding of 1gpa transformation induced plasticity steel. Accidental contact of electrode to metal objects can cause sparks, explosion, overheating, or fire. A form of resistance welding, spot welding is one of the oldest welding processes whereby two or more sheets of metal are welded together without the use of any filler material.
Consequently, codes and standards developed by the american welding society specify exactly how a joint must look when the job is completed. The appropriate combination of the spot welding parameter will produce strong joining and good quality of welding. Welding imperfections are classified according to iso 6520 1 while their acceptable limits are specified in iso 5817 2 and iso 10042. Powered by a vision to blend power saving with aesthetics, artech has today germinated into a force to reckon with in the field of resistance welding. In steels, the chemical composition of the parent steel will have an effect on the cracksusceptibility. Welding cracks can be present at the surface, inside of the weld material or at the heat affected zones. Moreover, the numbers of defects were investigated. Spot welding technical information titespot welders. Some of these methods are listed below in order to illustrate how resistance welding differs from the others. Each of the above type of welding can be further classified depending on other micro level characteristics.
Defects of different kinds can be cre ated during the welding of austenitic stainless steels, e. Also caused by shrinkage stresses in high constraint areas. Resistance spot welding is used frequently as a successful joining method for. Pdf analysis of weld defects in similar and dissimilar resistance. What is welding defects types, causes and remedies. Resistance welding is one of many methods of fastening two or more pieces of metal together.
Business case improvement in saw welding process will reduced copq, nonproduction idle hours, delay in delivery of jobs. A small change of one parameter will affect all the other parameters. Experience gained from user contact and welding training of crewmembers showed that. A new resistance spot welding process will be setup to. Congratulations on acquiring your new pro spot i4 welder. The fusion zone is symmetrical about the axis of the laser beam and no welding cracks. Resistance welding bolting, riveting, soldering and arc. The purpose of the welding handbook for maritime welders is to provide guidance in modern welding and related processes and to provide the welder with a source of practical information on the right solution to specific onboard welding problems. Low porosity in cast magnesium welds by advanced laser twin.
In addition to brittleness, other common weld defects like cracks, porosity, lack of penetration and distortion can compromise the strength of the base metal, as well as the integrity of the weld. Check and be sure the area is safe before doing any welding. Process planning of resistance spot welding oscar an dersson licentiate thesis in production engineering stockholm, sweden 20 oscar andersson process planning of resistance spot welding kth 20 issn. Use lowhydrogen welding consumables from moisture protective packagings or rebake welding consumables. Marlin steel on july 20, 2016 resistance welding is an excellent way to join two pieces of stainless steel wire to create a strong, durable bond without relying on a separate welding material. Cracks at the site of a spot weld may indicate a low tensile strength for the weld, as the two pieces of metal werent properly joined. Bad welding technique can cause undercuts or incomplete penetrations of one kind or another. Powered by a vision to blend power saving with aesthetics, artech has today germinated into a force to reckon with in the field of resistance. The flying sparks, hot workpiece, and hot equipment can cause fires and burns. These parameters will determine the quality of the welds. Oct 28, 2008 weld defects happen for a host of reasons.
Its induced by hydrogen absorbed into the weld via the weld puddle. Asymmetrical spot weld marks the vast majority of the time, a wellexecuted resistance spot weld mark should have a perfectly round shape, or at least conform to the shape of the welding heads used to. High carbon content and alloy steels tend to form hard welds that are brittle and could crack, though this tendency can be reduced by tempering. The process involves applying pressure and heat to the weld area using shaped alloy copper electrodes which convey an electrical current through the weld pieces. You have a welder and support group that will increase your productivity. Analysis of weld defects in similar and dissimilar resistance seam welding of aluminium, zinc and galvanized steel. Lower electrode force, larger welding current and longer welding time all contributed to the easier occurrence of welding defects. This document contains general information about the topics discussed. It was found that the first welding pass decomposed the magnesium hydroxide into magnesium oxide and water while the second pass helped the vaporized water to escape, and thereby produced a pore free weld. Spot welding or resistance spot welding is a type of electric resistance welding used to weld various sheet metal products, through a process in which contacting metal surface points are joined by the heat obtained from resistance to electric current. Arc welding uses an electric arc to coalesce metals arc welding is the most common method of welding metals electricity travels from electrode to base metal to ground 7. Cracking phenomenon in spot welded joints of austenitic. Thus, a spot weld made in two sheets, each 1 mm in thickness, would generate a nugget 5 mm in diameter according to the 5t. These joints created by resistance spot welding form a button or fused nugget.
Due to the concentration of high pressure on a relatively small area, within a very short time and high energy in the form of electrical current up to 40,000 a, a very strong joint is produced by spot welding. Ppt spot welding powerpoint presentation free to download. Consider it an experienced second opinion in a specialized field. The spot welding process parameters have their own importance. There are many different types of steel which require different types of welding tools and techniques, assuming it can be welded in the first place. Welding defects occurrence and their effects on weld quality in. The presence of welding defects in weld nugget has been reported in some investigations. A welding defect is any flaw that compromises the usefulness of a weldment. Various factors contribute to weld problems, but many lead back to the same place. Often, the crack forms along the axis center of the joint as the two sides pull apart. Pdf a phenomenological study of weld discontinuities and.