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pulsed dc weldingpulsed dc involves the repetitive variation in arc current from a background low value to a peak value adjustments of the pulse
direct currentusing direct current the tungsten electrode may be connected to either the negative or the positive terminal of the supply of power in
gas lensesgas lenses are used to provide a laminar flow of shielding gas all these attachments have a porous barrier diffuser and are fitted around
limitations of gas tungsten arc welding gtawit produces lower deposition rates than consumable electrode arc welding processesit requires slightly
advantages of gas tungsten arc welding gtawproduces high quality low distortion weldsfree from spatterthe process can be used with or without filler
weld defectsthe common defects encountered in submerged arc welding area slag inclusionb porosityc cracking of welds a slag inclusion slag
welding variablesthe following major process variable play an important role in shaping the weld bead and the resultant weld metal in submerged arc
flux feeding amp recovery systemthe flux is fed by gravity from the flux delivery hopper mounted on the welding head through a tube into the welding
mounting systems for the welding head-boom mounted typethese are the most versatile type of welding systems normally the boom is supported by
mounting systems for the welding head-carriage mounted typein this set up the welding head is mounted on a movable carriage the carriage is
fixed typein this set up the welding head is kept fixed and the movement required during welding is provided through in the jobs to be welded a
mounting systems for the welding headsubmerged arc welding head may be mounted by one of the following three methodsa fixed typeb carriage
wire feed systemthe submerged arc welding machine of the wire feed control may be of the following types1 voltage sensitive system2 constant wire
welding headsubmerged arc welding head consists of the wire spool wire feed system flux delivery hopper and electrical contact nozzle the electrode
principle of submerged arc weldingin submerged arc welding the arc zone is submerged beneath the molten flux and hence there is no visible signature
submerged arc weldingthe optimum performance of welded vessels and structures in service have led to the full exploitation of automatic welding
storage and handling of electrodesit is recommended that the electrodes should be stored in a warm and dry place generally conditions of storage in
inconel electrodesthese electrodes are used in the industries like petrochemical fertiliser etc the weld composition contain small percentage of
cast iron electrodesthere are three types of electrodes for welding of cast ionsa monel-cored electrodes 30 ni 70 cub fe-ni 40 nic ni-electrodes
hardfacing electrodesthere are many types of hard facing electrodes these electrodes are mainly useful in the maintenance and repair of machinery
stainless steel electrodesa variety of stainless steel electrodes are now being manufactured to produce weld metal similar to composition of most
low alloy creep resisting electrodes and electrodes for cryogenic applicationsthe flux coating contains small amount of alloying elements like cr mo
low hydrogen electrodeslow hydrogen electrodes are so called because their covering is low in hydrogen bearing compounds and only traces of hydrogen
iron powder electrodesiron powder is a widely used covering ingredient it is incorporated in certain coverings to the extent of one half of the total
rutile electrodethis type has thicker coating than cellulosic coated and the flux is mainly composed of rutile titanium di - oxide and silicates with