Other Welding Processes PDF

Other Welding Processes University of the Philippines Diliman – Department of Mechanical Engineering Thermit Welding (TW) ▪ Thermit Welding Superheated (TW) Steels and cast...

Other Welding Processes University of the Philippines Diliman – Department of Mechanical Engineering Thermit Welding (TW) ▪ Thermit Welding Superheated (TW) Steels and cast irons can be welded molten iron ▪ Thermit is one part aluminum, three parts iron oxide and lit by a magnesium fuse ▪ Target metal melts and flows into the prepared joint (https://youtu.be/ 5uxsFglz2ig) University of the Philippines Diliman – Department of Mechanical Engineering Thermit Welding University of the Philippines Diliman – Department of Mechanical Engineering Electroslag Welding (ESW) ▪ Electroslag Welding (ESW) ▪ For joining thick plates and large sections ▪ heat is derived from the passage of electrical current through a pool of electrically conductive liquid slag ▪ molten slag then melts the edges of the pieces that are being joined, as well as continuously fed solid or flux- cored electrodes https://youtu.be/Ce6IKDDk2u8 University of the Philippines Diliman – Department of Mechanical Engineering Electroslag Welding (ESW) ▪ Solidification control COOLING ▪ ESW has slow cooling ▪ Large heat affected zone (HAZ) ▪ Extensive grain growth University of the Philippines Diliman – Department of Mechanical Engineering University of the Philippines Diliman – Department of Mechanical Engineering Electroslag Welding (ESW) University of the Philippines Diliman – Department of Mechanical Engineering Electron Beam Welding (EBW) ▪ Electron-Beam Welding (EBW) ▪ metal to be welded is heated by the impingement of a beam of high- velocity electrons ▪ For joining metals that cannot be welded through conventional means ▪ For joining dissimilar metals https://youtu.be/grzbTs69wuw University of the Philippines Diliman – Department of Mechanical Engineering University of the Philippines Diliman – Department of Mechanical Engineering Laser Beam Welding (LBW) ▪ Laser-Beam Welding (LBW) ▪ For welding without need for fillers (autogenous welding) ▪ Requires proper preparation and cleaning of surfaces to be welded ▪ Laser-Beam Cutting ▪ Laser Spot Welding University of the Philippines Diliman – Department of Mechanical Engineering University of the Philippines Diliman – Department of Mechanical Engineering Laser-beam Cutting University of the Philippines Diliman – Department of Mechanical Engineering Schematic of Laser Beam Cutting Assist gas used for different metals: ▪ Oxygen → mild steel Cools the workpiece, ▪ Nitrogen → stainless steel minimizes the HAZ and may and aluminum participate in a combustion ▪ Argon → titanium reaction with the material being cut. ▪ Inert gases/ air → nonmetallics Cutting speed- set by the rate at which the lase can melt or vaporize the material. Schematic of laser-beam cutting. The laser provides the heat, and the flow of assist gas propels the molten droplets from the cut. University of the Philippines Diliman – Department of Mechanical Engineering Laser Spot Welding ▪ Non contact process ▪ Can be performed with access to only one side of the joint ▪ Produces no indentations ▪ No electrodes needed ▪ Weld quality is independent of material resistance, surface resistance and electrode condition ▪ No water cooling is required ▪ Total heat input is low University of the Philippines Diliman – Department of Mechanical Engineering Laser Spot Welding University of the Philippines Diliman – Department of Mechanical Engineering University of the Philippines Diliman – Department of Mechanical Engineering Flash Welding (FW) ▪ Used to produce butt welds between similar or dissimilar metals in solid or tubular form ▪ Two pieces of metal are first secured in currentcarrying grips and lightly touched together. ▪ An electric current may be passed through the joint to provide optional preheat, after which the pieces are withdrawn slightly. ▪ An intense flashing arc forms across the gap, which melts the material on both surfaces. ▪ The pieces are then forced together under high pressure University of the Philippines Diliman – Department of Mechanical Engineering University of the Philippines Diliman – Department of Mechanical Engineering Variations of Flash Welding ▪ Percussion welding (PEW) - a rapid discharge of stored energy produces a brief period of arcing, which is followed by the rapid application of force to expel the molten metal and produce the joint ▪ Upset Welding (UW) – similar to flash welding but without the arc. Heating is due to resistance of metal. ▪ https://youtu.be/-uBe5OagetU ▪ https://youtu.be/ApLBfQs958w ▪ https://youtu.be/MMzk5blgtbM University of the Philippines Diliman – Department of Mechanical Engineering Welding-related Surface Treatment Processes ▪ Surfacing or thermal cladding – depositing weld metal onto athe surface of a different material (if base material is softer than the weld metal, this will be hardfacing) ▪ Methods: ▪ Thermal spray coating or thermalizing – molten metal is sprayed onto the surface of the material to be clad ▪ Five different methods University of the Philippines Diliman – Department of Mechanical Engineering University of the Philippines Diliman – Department of Mechanical Engineering University of the Philippines Diliman – Department of Mechanical Engineering University of the Philippines Diliman – Department of Mechanical Engineering