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Figure 1: Shielded Metal Arc Welding.
The manual metal arc welding is also known as shielded metal arc welding or metal arc welding process. It is an arc welding process, wherein the welding is done by heating the workpiece with an electric arc set up between a flux coated electrode and the workpiece.
The Eddy Current Heating effect is produced due to eddy currents induced in the mass to be heated. Alternating current cutting the conducting substance induces eddy currents in it and the loss of energy due to eddy currents is “eddy current loss” which appears to be in the form of heat. This eddy current loss,
We = K × B2 × f2 × volume
where,
k is constant
f is supply frequencty
B is magnetic fied intensity.
Since We ∝ B2 and also We ∝ f2 and hence eddy currents principle is used in heating a conducting substance.
Angle Dekkor is an angle comparator which measures angle and deviation with the help of another device, may be a sine bar or angle gauges. It is a type of autocollimator which calibrates vertical and horizontal angular measurements. It consists of microscope eyepiece, collimating lens, glass screen, illuminating scale, datum scale. lamp, prism and workpiece as shown in figure 1.
It is the process of welding without the use of flux or flux coated electrode, which are generally highly corrosive. The heat for welding is produced by an arc struck between non-consumable tungsten electrode and the work.
The process involves the welding of metals using a consumable metal electrode in an inert gas atmosphere. The arc is struck between the metal electrode and workpiece (see Fig. 1). The electrode is in the form of continuous wire, which is fed by adjustable feed motor to the weld continuously.
This process is a modification of spot welding, in which the current and pressure are localised at the weld points. In this process, the projections are formed In the sheets to be welded by embossing in a punch press. The welding is done in a press type machine with electrodes in the form of platens which can distribute the current and pressure equally on the sheets. The advantage of this type of welding is that a number of spot welds can be made simultaneously (see Fig. 1).
Fig. 1: Projection Welding.
The spot welding method is used to weld on spot. Sheets to be welded are held between electrodes made of copper or alloy of copper or tungsten. This process is used to join overlapping sheets or plates. The sheets to be welded are held between the electrodes. The pressure is applied and the current is passed through the metal.
