Advantages of AC Welding

[Music] la a today AC welding equipment can be used for the vast majority of all welding jobs more than 90% of them with AC equipment you can now weld quickly and easily all types of mild Steel Cast Iron stainless steel alloy Steels of all kinds thanks to the Perfection and Universal availability of suitably coated electrodes for example with AC equipment you can now do vertical welding and also overhead welding horizontal as well as flat and you can do it under the wi widest variety of conditions for applications requiring fabrication of light gauge material heavy fabrication maintenance work inside construction outside Construction and as you apply AC welding to this broad varied field of service in so doing you gain six important advantages Advantage number one virtual elimination of Arc blow to visualize this Advantage watch some AC welding equipment at work on jobs hard to do with DC equipment first the case of a poor fit up in a light section not that the operator welds smoothly without having to fight Arc blow or guard against it by complicated timec consuming variations of regular technique observe next a case involving the ends of straight runs in deep grooves here again there is no Arc blow to fight no Arc blow either in the AC handling of fillet welds involving corners or even in the case of a job like this one which calls for welding together an assembly of heavy plates put together like a Dagwood sandwich into a 4x10 by 6t section weighing 8 tons if DC equipment were to be used on this job or on any of the other welding operations that we just watched here's what the operator would have to be constantly on guard against and on repeated occasions would have to fight AR blow Arc blow is a good name for this phenomenon because the magnetic forces which cause it Blow the molten slag and metal during transfer with a wind-like effect and with such violence that frequently when using large diameter electrodes welds of poor external appearance and bad internal quality result with DC equipment Arc blow is an present source of trouble because under welding conditions the magnetic field from DC exerts pressure or blow on the ark continuously in One Direction but with AC equipment as shown here Arc blow is virtually eliminated the fundamental characteristic of alternating current with its continuous rapid polarity reversals and resultant Eddie currents reduces the electromagnetic forces on the arc stream eliminating Arc blow the result is a weld of neat external appearance and good internal quality Advantage number two faster welding on many jobs like this one an average operator using AC equipment in place of DC can increase his welding output from 20 to 30% to understand what makes this increase possible consider what a DC welding operator may have to do in order to overcome an arklow trouble situation before he can go on with his work you may have to do one or more of the following things relocate the ground cable connection to the work reduce electrode size place a small Stringer bead ahead of the weld or he may improvise a coil made up of a few turns of his welding cable wrapping the coil around part of the work seeking a good neutralizing spot needless to say all such methods for overcoming Arc blow with DC equipment take time that's why welding output automatically increases when AC equipment is used larger diameter electrodes at higher currents can be used regularly this makes possible greater welding speeds on all classes of work for example at L and weld incorporated in in Coatsville Pennsylvania 3in plate steel is being successfully welded with 3/8 in electrodes using the larger diameter electrodes made possible by AC equipment increased weld speed 20% another example at the pen boiler and burner Manufacturing Corporation of Lancaster Pensylvania complete replacement of DC welders with AC eliminated Arc blow and and increased welding footage 60% in addition weld defects were lowered from 10 to three per boiler a reduction of 70% Advantage number three High weld quality day in and day out AC welders are able to produce results like these welds that are smooth externally and sound internally welds of X-ray quality even when made in vertical and overhead positions to appreciate why AC equipment is able to produce consistently good welds consider some of the quality impairing factors of Arc blow characteristically encountered with DC equipment when the blow is of such a nature that Arc draft curves the flame up and ahead of the progress of the weld the ark may miss the plate and penetration cannot be obtained the weld metal is then simply plastered to the plate on the other hand when Arc draft is backward toward the finished bead the effect is then to upset the welded metal just as it freezes results a rough unsightly weld in addition a further quality impairment results from failure to preheat properly making it difficult to control penetration and undercut the poor quality of these DC welds is automatically eliminated when AC welding is used here's another Factor contributing to the high quality of AC welds these extremely slow motion Arc pictures were taken by a special camera at the Reed Avery company at dundock Maryland the camera actually shows the continuous rapid polarity reversals characteristic of an AC Arc these reversals exert a beneficial stirring effect and help gas and impurities to rise so they won't be entrapped in the weld this is another reason why AC welds measure up fully to all requirements of soundness ductility and tensil strength advantage number four ease of operation to illustrate this Advantage let's consider the case of a modern AC welder to put this unit in operation here's all you have to do connect the welder select the amperage strike The Arc and Weld and as you weld weld easily with an ease uncomplicated by arcing trouble even when you work in Corners at edges or in recesses note also that a single hand crank gives quick stepless setting to any desired current over the entire range of current adjustment once you preset this control for the proper welding current you can forget all about it you don't have to readjust it like you'd have to do for example with most DC units after the set has warmed up such a Readjustment in case you are working on a job like this one might force you to make a long climb back up to your work position but not with AC welders there it's a case of preset it and forget it even beginners with little welding experience and only brief preliminary training are able to turn out consistently good AC welds only 65 open circuit volts as shown by this test voltmeter is still another feature of modern AC welders a stabilizing circuit built into the welder itself assures Arc stability at this low voltage over the entire operating range of welding current this device inside the welder not only AIDS in Striking The Arc but is especially designed to maintain a stable Arc during the entire welding cycle however where conditions make an even lower open circuit voltage desirable then AC welders are available with built-in positive action open circuit voltage reducing controls this control automatically reduces the normal no load voltage from 65 to approximately 30 volts during the off Arc period and hence contributes importantly to the overall safety and ease of AC equipment operation while welding in confined areas is for instance Advantage number five economy of operation a Transformer type AC welder as compared with a DC unit of similar rating will use approximately 1/3 less power this greater operating economy is explained by several factors first due to the absence of rotating element windage and friction AC Transformer welders have 85 to 90% electrical efficiency as contrasted with 55 to 65% for DC machines second with AC welding no load losses are only a small fraction of those encountered with DC the small AC no load losses compared to DC means that essentially you pay pay only for the power used during welding this is important because the average welding machine operates at no load more than 2/3 of the time and here's still a third factor that helps account for the economy of AC welding buil-in power factor correction when you add up these considerations it is evident that an AC welder is by far the most efficient type of single operator welding set available today in dollars and cents this means that by replacing a 300 aamp DC welder with an AC on the same job you can save as much as $186 in power costs per year Advantage number six minimum maintenance this Advantage results from the inherent Simplicity of alternating current Transformer design on the contrary with DC welders rotating Parts wear out and need greasing brushes need replacing and commutators must be periodically cleaned and machined down with AC welding you can expect years of maintenance-free service here's proof suppose we let just a few actual case history speak for themselves Pittsburgh de Mo Steel company speaking in this shop we use AC welding equipment for over 90% of our welding work as contrasted with maintenance costs of DC units analysis shows that we save $21 in maintenance on each AC welding set every year Treadwell Manufacturing Company of Beaver Pennsylvania speaking maintenance of what DC welders we have requires weekly inspection and servicing to Ure continuous operation maintenance of our AC welders is negligible we are now using AC welders that are 7 years old not one of them has ever been out of operation for a servicing Bal and locomotive Works speaking approximately 50% of our welding equipment is AC we are steadily replacing DC units because high maintenance costs prohibit their continued use on the contrary our AC welders have been working maintenance-free on a three shift basis for years we soon hope to be operating 100% AC scores of other case histories yield similar evidence in favor of AC welding evidence not only on the score of minimum maintenance but evidence also of eliminated Arc [Music] blow faster welding better welding greater ease of operation and last but not least greater operating economy as well as economy of first cost all of these advantages are backed up by thousands of applications applications that continue to expand with a forward March of technology and research in the Perfection of new ever improved AC electrodes electrodes that continue to widen the already farflung Horizons of AC welding the