The Process Of Projection Welding ? What Ever It Is

Any modern construction like a car or a bridge needs nuts and bolts. These nuts and bolts are small in size but play a big role in fastening the parts together and saving the constructions from getting demolished. They are critical for the final products? safety. Projection welding is the most common method for nut and M or T-thread bolt welding. The nuts and bolts have annular projections or three to four separate projections, depending on what use they will be put to. There are separate projections as well but annual projections offer few crack initiation points.
The embossed or machine projection determines the projection welding. The heat required for projection welding is determined by some factors like projection design and location, thickness of the sheet, thermal and electrical conductivities of the welded metals, heating rate and the electrode alloy type. There are three phases involved in this welding process. In the first stage the projection is in contact with the mating sheet. The current heats the projection to welding temperature and thus melting and fusion takes place. The current of projection is generally less than that which is required to produce corresponding spot welds. But the current must be high enough to at least create fusion before the complete collapse of the projection. A less amount of welding time might be needed from the production standpoint view but high amperage will be required. Therefore the welding parameters should be optimized so that overheating and metal expulsion could be prevented. The force applied by the electrodes should also be enough to flatten the projections completely when they reach the welding temperature and to bring the fastener in contact with the sheet metal part. If too much of pressure is applied the projections will prematurely collapse and the weld will have an incomplete fusion in the center. The entire welding process should follow the movements of the electrodes. If the follow up is slow it will result in metal expulsion before the coming together of the parts.

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