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UL Lafayette MCHE 365 - Solid-State Welding Processes

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Chapter 28Cold WeldingUltrasonic WeldingFriction WeldingSlide 5Inertia Friction WeldingLinear Friction WeldingFriction Stir Welding (FSW)Resistance WeldingResistance Spot WeldingSlide 11Resistance Seam WeldingResistance Projection WeldingSlide 14Flash WeldingStud WeldingTHE ENDChapter 28Solid-State Welding ProcessesCold Welding•Pressure is applied to the workpieces through dies or rolls•Preferably both work pieces should be ductile•The work pieces should cleaned thoroughly•Can not join dissimilar metalsFig: The roll bonding or cladding processUltrasonic Welding•Surfaces of the two components are subjected to a static forces and oscillating shearing force•Produces a strong, solid-state bond•Versatile and reliable for joining metalsFig: a) Components of an ultrasonic welding machine for lap welds.The lateral vibration of the tool tip cause plastic deformation and bonding at the interface of the work piece b)Ultrasonic some welding using a roller c)An ultrasonically welded partFriction Welding•Developed in the 1940’s•Parts are circular in shape•Can be used to join a wide variety of materialsFig: Sequence of operation in the friction welding process 1)Left-hand component is rotated at high speed. 2) Right-hand component is brought into contact under an axial force 3)Axial force is increased;the flash begins to form 4) Left-hand component stops rotating;weld is completed.The flash can subsequently be removed by machining or grinding•Process can be fully automated•Can weld solid steel bars up to 250mm in outside diameterFig:Shape of friction zone in friction welding,as a function of the force applied and the rotational speedFriction WeldingInertia Friction Welding•Modification of Friction Welding•Energy is supplied by a fly wheel•The parts are pressed together by a normal force•As friction at the interface increases, the fly wheel slows down•The weld is completed when the flywheel stopsFig : The principle of the friction stir welding process. Aluminum-alloy plates up to 75mm (3in) thick have been welded by this processLinear Friction Welding•Parts are joined by a linear reciprocating motion•Parts do not have to be circular or tubular•In this application, one part is moved across the face of the other part using a balanced reciprocating mechanismFriction Stir Welding (FSW)•New Process for welding aerospace metals•Research is being directed towards using this process for polymers•FSW uses a 3rd nonconsumable tool inserted between the two bodies to heat the material to be joinedResistance Welding•Developed in the early 1900’s•A process in which the heat required for welding is produced by means of electrical resistance across the two components•RW does not requiring the following:–Consumable electrodes–Shield gases–FluxResistance Spot Welding•RSW uses the tips of two opposing solid cylindrical electrodes•Pressure is applied to the lap joint until the current is turned off in order to obtain a strong weldFig: (a) Sequence in the resistance spot welding•Surfaces should be clean•Accurate control of and timing of electric current and of pressure are essential in resistance weldingFig: b)Cross-section of a spot weld,showing the weld nugget and the indentation of the electrode on the sheet surfaces.This is one of the most commonly used process in sheet-metal fabrication and in automotive-body assemblyResistance Spot WeldingResistance Seam Welding•RSEM is modification of spot welding wherein the electrodes are replaced by rotating wheels or rollers•The electrically conducting rollers produce a spot weld•RSEM can produce a continuous seam & joint that is liquid and gas tightFig : (a) Seam-Welding Process in which rotating rolls act as electrode (b) Overlapping spots in a seam weld. (c) Roll spot weld (d) Resistance-welded gasoline tankResistance Projection Welding•RPW is developed by introducing high electrical resistance at a joint by embossing one or more projections on the surface to be welded•Weld nuggets are similar to spot weldingFig: a) Resistance projection Welding b)A welded bracket c) & d) Projection welding of nuts r threaded hosses and stack•The electrodes exert pressure to compress the projections•Nuts and bolts can be welded to sheet and plate by this process•Metal baskets, oven grills, and shopping carts can be made by RPWResistance Projection WeldingFlash Welding•Heat is generated from the arc as the ends as the two members contacts•An axial force is applied at a controlled rate •Weld is formed in plastic deformationFig : (a)Flash-welding process for end-to –end welding of solid rods or tubular parts(b) & (c) Typical parts made by flash welding (d)Design Guidelines for flash weldingStud Welding•Small part or a threaded rod or hanger serves as a electrode•Also called as Stud arc welding•Prevent oxidation to concentrate the heat generation•Portable stud-welding is also availableFig:The sequence of operation in stud welding,which is used for welding bars threaded rods and various fasteners onto metal platesTHE

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