1.Welding cables
Cables to be used for welding must be flexible,well-insulated, and the correct size for the job.Most welding cables are made from stranded copper wire.Some manufacturers sell a newer type of cable made from aluminum wires.The aluminum wires are ligther and less expensive than copper.Because aluminum as a conductor is not as good as copper for a given wire size, the aluminum wire should be one size larger than would be required for copper.
The insulation on welding cables will be exposed to hot sparks,flames,grease,oils,sharp edges,impact, and other type of wear.To withstand such wear, only specially manufactured insulation should be used for welding cable.
(Welding principles and applications 3rd edition LARRY JEFFUS P.52)
2.lAP JOİNT
A lap joint is made by overlapping the edges of the two plates.The joint can be welded on one side or both sides with a fillet weld.
As the fillet weld is made on the lap joint, the buildup should equal the thickness of the plate.A good weld will have a smooth transition is abrupt, it can cause stresses that will weaken the joint.
Penetration for lap joint does not improve their strength. complete fusion is required.The root of fillet welds must be melted to ensure a completely fused joint.İf the molten weld pool shows a notch during the weld, this is an indication that the root is not being fused together.
(Welding principles and applications 3rd edition LARRY JEFFUS P.76)
3.Hot pass
The hot pass is used to quickly burn out small amount of slag traped along the edge of the root pass.This is slag that can not be removed easily by chipping or wire brushing.The hot pass can also be used to reshape the root pass by using high current settings and a faster than normal travel speed.
Slag is mostly composed of silicon dioxide, which melts at about (1705 c ).Steel melts at approximately 1440 c.
A temperature of more than 270c hotter than the surrounding metal is required to melt slag.The slag can be floated to the surface by melting the surrounding metal.A high curront will quickly melt enough surface to allow the slag to float free, a fast travel speed will prevent burnthrough.The fast travel speed forms a concave weld bead that is easy to clean for the welds that will follow.
(Welding principles and applications 3rd edition LARRY JEFFUS P.92)
4.Nozzle tip
The nozzle tip has a small, cone-shaped,constricting,orifice in the center.The electrode setback space, between the electrode tip and nozzle tip, is where the electric current forms the plasma.The preset close fitting parts provide the restriction of the gas in the presence of the electric current so the plasma can be generated.The diameter of the constricting orifice and the electrode setback are major factors in the operation of the torch.As the diameter of orifice changes, the plasma jet action will be affected.When the setback distance is changed, the arc voltage and current flow will change.
(Welding principles and applications 3rd edition LARRY JEFFUS P.165)
5.Standoff distance
The standoff dıstance is the distance from the nozzle tip to the work.This distance is very critical to producing quality plasma arc cuts.As the distance increases, the arc force is diminished and trends to spread out.This causes the kerf to be wider, the top edge of the plate to become rounded, and the formation of more dross on the bottom edge of the plate.However, if this distance becomes too close, the working life of the nozzle tip will be reduced.in some cases an arc can form between the nozzle tip and the metal that instantly destroys the tip.On some new torches, its possible to drag the nozzle tip along the surface of the work without shorting it out.This a large help when working on metal out of position or on thin sheet metal.Before you use your torch in this manner, you must check the owners manual to see if it will operate in contact with the work.This technique will allow the nozzle tip orifice to become contaminated more quickly.
(Welding principles and applications 3rd edition LARRY JEFFUS P.169)
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