Index• Introduction• Classification of Metal Joining Process• Welding Process• History Of Welding• Classification of Welding Process• Metal Joining Process In Body Shop• Methods Of Testing
What is Metal Joining Process? Metal Joining is defined as joining of two metal parts either temporarily with or with out the application of heat or pressure. Classification Rivetting Bolting Welding
RivettingIts is metal joining Process in which thetwo metallic parts are joined by the rivets.In this process, the mettalic parts to bejoined do not undergo any change in theirphysical structure or atomic structure.Rivetting is used widely in automobileindustry and in many other applicationswhere we do not require permanentbonding
BoltingIn this metal joining process, the metallic partsare joined together by means of Bolt and nut.This Process is widely used in assembling ofparts are to be joined temporarily orpermanently. WeldingIn this metal joining process the two parts are tobe welded are fused together by application ofheat and pressure.The welding processes depends on many factorsdepending on the type of welding process.
Welding ProcessDEFINITION: Welding is a process of joining materials. Welding joinsdifferent metals/alloys with a number of processes, in which heat issupplied either electrically or by means of a torch. Welding is doneby application of heat or both heat and pressure. The most essentialrequirements is Heat. Pressure may be employed, but this is not inmany processes essential.CONCEPT OF WELDING: The welding process evolves applying heat to the workpiece. The heat applied should be such that the work piece shouldmelt, i.e. the temperature at which welding is done, should be morethan the melting point of the work piece to be welded.
… cont. welding processBasic Requirements of Welding Processes 1. The Two Metal (work pieces) should be in contact with each other. 2. The weld Surface should be free from oxides, paint, oil,dirt,grease etc. 3. Energy Source. 4. Shielding: During Welding if the metal is exposed to air directly the Oxygen in air reacts with the metal to form oxide which results in poor welding. In order to avoid the shielding gas is used.
… cont. welding processParameters of Welding 1. Heat: The source of heat is very important. It may be provided by different methods depending on the composition of the parts to be joined, the application of the joints etc. 2. Pressure: The pressure may or may not be required, depending on the source of heat used for the welding and the quality or the strength of the joint required. 3. Surface Preparation: It is the basic necessity of the welding process. The parts to be joined by the welding process should be free of oil, grease, paint, dust etc. so as to get a very good quality weld.
History of Welding:S.No Welding Country Discoverer 1 Gas Welding France Henry Louis Le- Chatelier England Davy England Auguste de meritens 2 Arc Welding Sweden Oscar Kjellberg USA Strohmenger 3 Stud Welding England Martin 4 Resistance Welding Philadelphia Elihu Thomson
Classification of Welding Processes There are 35 different welding and brazing processes andseveral methods are being used by the industry today. Thewelding processes may be classified on the basis of a. Source of heat.i.e. flame, arc etc. b. Type of interaction.i.e. liquid/liquid (fusion welding ) or solid/solid (solid state welding). The classification is shown in the chart.
Classification of Welding Processes Welding Processes Gas Arc Resistance Solid State Thermo-chemical Radiant- EnergyWelding Welding Welding Welding Welding WeldingAir – Carbon Arc Spot Cold Electron BeamAcetylene Thermit Welding Welding SMAW Seam ExplosiveOxy- Atomic Hydrogen Laser BeamAcetylene SAW Projection Friction Welding WeldingOxy- GTAW Flash Butt Rollhydrogen MIG R DiffusionPressure Electroslag Forgegas Plasma Arc Hot Pressure Ultrasonic Welding
Gas Welding Gas Welding is a fusion welding process. It joins metals,using the heat of combustion of oxygen/air and fuel gas mixture.The intense heat thus produced melts and fuses together the edgesof the parts to be welded, generally with the addition of a fillermetal.Application of Gas Welding i. For joining thin metals. ii. For joining materials in whose case excessively hjgh temp. or rapid heating and cooling of the job would produce unwanted or harmful changes in the metal iii. For joining most ferrous and non-ferrous metals, i.e. Al, Cu, Ni, Mg, and its alloys etc.
Arc Welding Arc Welding is a group of welding processes, whereinfusion is produced by heating with an electric arc or arcs, mostlywithout the application of pressure and with or without the useof filler metal depending upon the base plate thickness.Resistance Welding Resistance welding is a group of welding processes where in fusion is produced by the heat obtained from flow of electric current in a circuit of which the work is a part and by application of pressure. No filler metal is used.
Solid State Welding A solid state welding process produces fusion at temperatures essentially below the melting pointy of the base materials being joined, without the addition of a filler metal. Pressure is always applied.Thermo chemical Welding Thermo chemical welding process comprises of producingfusion by heating with superheated liquid metal and slag resultingfrom chemical reaction between a metal oxide and aluminum,with or without the application of pressure. The liquid metal actsa filler metal too. Thermo chemical welding is used chiefly in repair ofassembly of large parts such as fractured rails, large fracturedcrankshafts, replacing broken teeth on large gears, etc.
Radiant Energy Welding Radiant Energy consists of fusion by focusing an energybeam on the work piece. The heat is generated when the energybeam strikes the work piece. It is used for joining highly reactive materials liketitanium, zirconium etc. In this process, welds can be made evenat those points that are virtually inaccessible for other weldingprocesses. It is used for welding airplane, aerospace and othertypes of equipments where especially low distortion is desired.