ME 12A8 - WELDING TECHNOLOGY for industries.pptx

welding

1. ME 12A8 - WELDING TECHNOLOGY

2. What is Welding ? • Welding is a process for joining two similar or dissimilar metals by the application of heat is called welding. • It joins different metals/alloys, with or without the application of pressure and with or without the use of filler metal. • The heat may be developed in several ways ie from combustion of gases, electric arc, electric resistance or by chemical reaction Applications S hips , pressure vessels, automobile bodies, off-shore platform, bridges, Railway wagons, aircraft frame, pipelines, sealing of nuclear fuel and explosives

3. Classification of Welding Proces s

4. TIG(Tungsten Inert Gas) Welding Proces s Basic principle It is the fusion welding process in which the arc is generated by non consumable electrode due to the arc the heat is generated in the weld area is sufficient to melt the base metal .The inert gas is used to prevent the weld area from atmospheric contamination.

5. Equipment Description & Working

6. EQUIPMENT DESCRIPTION 1 . Power So urce – AC or DC Rectifier, Generator, Motor (5-300Amp) (OCV 60-80 V),high frequency unit 2. TIG Torch – collet , nozzle(ceramic cup), tungsten electrode (98% W+2% Thoriated ) 3. Shielding Gas Supply Syste m – Regulator 4. Filler Materials

7. Working First, a high OCV high current supply supplied by the power source to the welding electrode or tungsten electrode. Mostly, the electrode is connected to the negative terminal of power source and work piece to positive terminal. This current supplied form a spark between tungsten electrode and work piece. Tungsten is a non –consumable electrode, which give a highly intense arc. This arc produced heat which melts the base metals to form welding joint. The shielded gases like argon, helium is supplied through pressure valve and regulating valve to the welding torch. These gases form a shield which does not allow any oxygen and other reactive gases into the weld zone. These gases also create plasma which increases heat capacity of electric arc thus increases welding ability. For welding thin material no filler metal is required but for making thick joint some filler material used in form of rods which fed manually by the welder into welding zone.

8. Applications: Mostly used to weld aluminum and aluminum alloys. It is used to weld stainless steel, carbon base alloy, copper base alloy, nickel base alloy etc. It is used to welding dissimilar metals. It is mostly used in aerospace industries.   

9. Advantages: TIG provides stronger joint compare to shield arc welding. The joint is more corrosion resistant and ductile. Wide verity of joint design can form. It doesn’t required flux. It can be easily automated. This welding is well suited for thin sheets. It provides good surface finish because negligible metal splatter or weld sparks that damage the surface. Flawless joint can be created due to non-consumable electrode. More control on welding parameter compare to other welding. Both AC and DC current can be used as power supply. Disadvantages: Metal thickness to be weld is limited about 5 mm. It required high skill labour. Initial or setup cost is high compare to arc welding. It is a slow welding process.  

10. MIG(Metal Inert Gas) Welding It works on basic principle of heat generation due to electric arc. This heat is further used to melt consumable electrode and base plates metal which solidify together and makes a strong joint. The shielded gases are also supplied through nozzle which protect the weld zone from other reactive gases. This gives good surface finish and a stronger joint.

11. Equipment Description & Working

12. EQUIPMENTS DESCRIPTION 1. Power Source – Constant Voltage DC Generator or Transformer or Rectifier, Electrode Positive 2. Wire feeder syste m- Driving Motor, Wire Pool Holder 3. Welding To rch- copper contact tube, nozzle, arrangement for cooling, controls 4. Shielding G ases – Argon, helium 5. Regulators - control the flow of shielding gases

13. WORKING First, a high voltage current is change into DC current supply with high current at low voltage. This current passes though welding electrode. A consumable wire is used as electrode. The electrode is connected to the terminal positive and work piece from negative terminal. A fine intense arc will generate between electrode and work piece due to power supply. This arc used to produce heat which melts the electrode and the base metal. Mostly electrode is made by the base metal for making uniform joint.  This arc is well shielded by shielding gases. These gases protect the weld form other reactive gases which can damage the strength of welding joint. This electrode travels continuously on welding area for making proper weld joint. The angle of the direction of travel should be kept between 10-15 degree. For fillet joints the angle should be 45 degree.

14. Applications: Generally all available metals can be weld through this process. It can be used for deep groove welding. Advantages: It provide higher deposition rate. It is faster comparing to arc welding because it supply filler material continuously. It produce clean weld with better quality. There is no slag formation. Minimize  weld defects . This welding produces very little slag. It can be used to make deep groove weld. It can be easily automated.  Disadvantages: It cannot be used for welding in difficult to reach portions. Higher initial or setup cost. It cannot be used for outdoor work because wind can cause damage of gas shield. It required high skilled labour.    

15. (SAW) Submerged Arc WELDING In this process welding arc is developed in between consumable welding electrode and the base metal . The welding arc is fully protected by flux power from atmosphere. Some amount of flux is melt and form the slag to give good surface finished weld.

16. Equipment Description & Working

17. EQUIPMENTS DESCRIPTION Power Source – DC Generator or Rectifier, AC Transformer of,200 -1000 Amp Wire Feeder – DC wire drive motor, Reduction gear box, Four roll drive mechanism, Wire pool holder.(1.2-7.5 m/min) Torch with Flux hopper Carriage

18. WORKING It is also called as sub arc welding or hidden arc welding Electric arc is produced between consumable bare electrode and work piece. But arc is completely submerged ie hidden under the flux powder. Arc is not visible outside The metal electrode is fed continuously from the reel by a moving head. The flux powder is feed in front of moving head, supplied from hopper. When the arc is produced in the welding zone at the end of electrode and arc is completely covered by flux powder. So there will not be any defect in the weld due to atmosphere effect Some of the flux melts and form slag on the weld. The unused flux is sucked by a pipe.

19. Advantage • Very high quality weld produced • It is very fast method • Deep penetration can be obtained • Shielding accessory for eye is not need Disadvantages • It is not suitable for welding work which is inclined and vertical • The welding zone is not seen. So it is difficult to guide the electrode movement

20. ELECTROSLAG WELDING This method is combination of both arc welding and resistance welding because at starting, heat is generated by establishes an arc between electrode and base metal (as in arc welding). This heat leads to melt flux and create a molten metal pool between the electrode and base metal. Now the current flow through this molten metal pool and heat is developed due to electric resistance (as in resistance welding). Due to this reason, this is called combination of arc welding and resistance welding. This heat further tends to melt filler metal which is continuously fed from the roller.

21. Equipment Description & Working

22. Equipment Description Power Source – Constant Voltage rectifier AC or DC (750 -1000 Amp) with 100% duty cycle and OCV of 60V Wire Feeder & oscillator – Motor driven, 17-150 mm/sec for 2.4 or 3.2mm wire , wire straightened , rack &pinion mechanical setup Guide Tube - Guiding the wire to the slag bath, electrical contact to the wire Retaining shoes – Two copper made water cooled retaining Shoes move &vertical upward, provide outside contour by accelerating solidification of the weld joint Welding Head with Control – control for power source, wire feeder, oscillator

23. First current is flow between welding electrode and base plate. This establishes an arc between electrode and base plate which heat the flux or filler wire. This heat leads to melt the filler metal and deposits into the weld cavity. Now the cooled copper shoe comes into action and start solidified this filler metal into weld cavity. This will made to avoid flowing out the weld metal. As the filler metal solidified into weld cavity, the current flow through it. It will generate heat due to electric resistance. This heat is further use to continuous melting down the filler metal into weld Cavity. The filler metal continuously provide through roller arrangement as shown in figure. During welding both the copper shoe and feed mechanism moving upward unlit the whole cavity is formed. This will create a strong joint in single pass. The single or multi-pass weld is used according to plate thickness.

24. Application: It is used in heavy industries where plate thickness up to 80mm to be joint. This process is used to joint large casting and forging to produce very large and composite structure.  Welding of thick walled large diameter pipes, pressure vessels, storage tanks and ships etc. Advantages: Cooling rate is very low so there is no problem of cold cracking. There is no problem of slag inclusion or porosity in electroslag welding. The process is semi-automatic and faster. Heavier section can be welded in single pass. High productivity can be achieved. Low cost for joint preparation. Disadvantages: Too high heat input to base. High temperature of welding needs cooling arrangement. Slow rate of cooling give columnar grain in weld.  

25. Resistance Welding Basic Principle The amount of heat generated in the work pieces depends on the magnitude of the current, the resistance of the current conducting path and time for which the current is flow. This is expressed in terms of joule heating H = IVT = I(IR) T Resistance Welding is a method of joining metals. To join two metals by resistance welding, it is necessary only to clamp them together under pressure and pass through them an electric current for a specific time. The heat generated creates a plastic state and produces fusion at the interface surfaces .

26. Equipment Description & Working

27. Equipment Description Power Source – Both AC or DC with 50 – 60 Hz,1000- 100000 Amp,1-25 V Welding Electrode – copper, conduct the welding current, transmit the desired pressure Pointed tip(truncated cone),Flat, domed

28. Squeeze Time is the welding process time interval between the initial application of the electrode force on the work and the first application of weld current.. Squeeze Time is necessary to delay the turn on of weld current until the electrode force has built up to the required welding force. If welding current is turned on before the required force is attained, there will be metal expulsion. If welding current is on before the electrodes meet the workpiece , the resulting arcing will cause extreme metal expulsion and may cause damage to the tooling and create a possible hazard to personnel. Weld Time is the time during which welding current is applied to the work in making a weld. Weld Time is measured in cycles of line voltage, as are all timing functions. One cycle is 1/60 of a second in a 60Hz power system. In the U.S. the line frequency is universally 60Hz (60 cycles per second). In other parts of the world, 50Hz is more common. Know the material to be welded so that a proper weld time can be selected. Hold Time is the time during which electrode force is maintained on the work after the last cycle of welding current ceases. Hold Time is necessary to allow the weld nugget to solidify before releasing the welded parts. This is a forging process. For some metals, Hold Time may be critical, for example, HSLA steels and aluminum. Off Time is the time during which the electrodes are off the work in a repeat cycle. The term is only applicable where the weld sequence is repetitive (control set to “REPEAT”). Off Time is the time necessary to move the work between weld sequences.

29. Advantages of Resistance Welding High welding rates; Low fumes; Cost effectiveness; Easy automation; No filler materials are required; Low distortions. Disadvantages of Resistance Welding High equipment cost; Low strength of discontinuous welds; Thickness of welded sheets is limited - up to 1/4” (6 mm); Applications - joining vehicle body parts, fuel tanks, domestic radiators, pipes of gas oil and water pipelines, wire ends, turbine blades, railway tracks. The most popular methods of Resistance Welding are: 

30. RESISTANCE BUTT WELDING First edges of the work piece should be cleaned perfectly. Flatten parts to be welded are clamped in copper jaws as shown. The jaws acts as electrode. Their may be some gap between the parts, but it should be such that no arcing take place. Then the jaws are brought together in a solid contact when current flows through the point of contact of jaws to form a locality of high electric resistance. At this point applied pressure forges the part together

31. UNIT 2 UNCONVENTIONAL WELDING PROCESS

32. Electron Beam Welding Electron beam welding is a liquid state welding process. Liquid state welding are those welding processes in which, the metal to metal joint form in liquid or molten state. This is also classified as a new welding process because it uses electrons kinetic energy to fuse two metal work pieces. This process uses kinetic energy of electrons to produce heat. This heat is further used to weld two welding plates. When a high jet of electrons strike at welding plates, its kinetic energy converts into heat energy. This heat energy is sufficient to fuse two metal plates together to form a weld joint. .  

33. Equipment Description & Working

34. Equipment Description Power Supply: This process uses a power source to supply continuous beam of electrons for welding process. The voltage range of welding is about 5 – 30 kV for low voltage equipment’s or for thin welding and 70 – 150 kV for high voltage equipment’s or for thick welding. Electron Gun: It is heart of electron beam welding. It is a cathode tube (negative pole) which generates electrons, accelerate them and focus it on a spot . This gun is mostly made by tungsten or tantalum alloys . The cathode filament heated up to 2500 degree centigrade for continuous emission of electrons.  Anode: Anode is a positive pole which is just after the electron gun. Its main function is to attract negative charge, (in this case electron) provide them a path and don’t allow them to diverge from its path. 

35. Magnetic Lenses: There are a series of magnetic lenses which allows only convergent electrons to pass . They absorb all low energy and divergent electrons, and provide a high intense electron beam . Electromagnetic lens and deflection coil: electromagnetic lens used to focus the electron beam on work piece and deflection coil deflect the beam at required weld area. These are last unit of EBW process.  Work holding device: EBW uses CNC table for hold work piece which can move in all three direction. The welding plates are clamped on CNC table with the use of suitable  fixtures . Vacuum Chamber: As we know, whole this process takes place in a vacuum chamber. Vacuum is created by mechanical or electric driven  pump . The pressure ranges in vacuum chamber is about 0.1 to 10 Pa.

36. WORKING First the electron gun, which is a cathode, produces electrons. These electrons move towards anode which is positive charged and placed right after electron gun. The anode accelerates the electrons and forma electron jet which is further move towards magnetic lenses. The magnetic lenses are a series of lenses which are used to absorb low energy electrons and does not allow to divergent electron to passes through it. It provides a high intense electron jet. Now this electron beam passes through electromagnetic lens and defecting coil which are used to focus and deflect the electron beam at the required spot. This unit direct high velocity electron beam to the weld cavity where its kinetic energy converts into heat energy due to collision. This heat energy is used to create weld by fusion. This whole welding process carried out in a vacuum chamber otherwise the electrons collides with air particle in the way and loses its energy.

37. Application: It is used in aerospace industries and marine industries for structure work It is used to join titanium and its alloy. This  type of welding  is widely used to join  gears ,  transmission system ,  turbocharger etc . in automobile industries. It is used to weld electronic connectors in electronic industries. This process is also used in nuclear reactors and in medical industries Advantages: It can weld both similar and dissimilar metals. It provides high metal joining rate. Low operating cost because no filler material and flux are used. It provide high finish welding surface. It can used to weld hard materials. Less  welding defects  occur due to whole process carried out in vacuum. Disadvantages: High capital or set up cost. High skilled labor required. Frequently maintenance required. Work pieces size is limited according to vacuum chamber. It cannot do at site due to vacuum.

38. Laser Beam Welding Laser(Light Amplification by simulated emission of radiation) beam welding process the heat is obtained from the application of a concentrated coherent light beam which striking upon the weld metal and melt the metal, such this weld joint is obtained, this welding process is called laser welding. In laser beam, the lights are coherent, i.e. light rays are identical and parallel. The laser device is generates the concentrating light wave into narrowly and gets the highly intense beam which can imparts tremendous amount of heat energy on a small area, this heat energy can fuse the metals, which we are using for welding purpose .

39. Equipment Description &Working

40. Equipment Description Power Supply The capacitor is provided for storage the electrical energy and supply the high voltage to flash tube for performed appropriately It provides the energy for excitation of electron from lower energy level to higher energy level Flash Tube A flash tube is placed around the Ruby Crystal, which is filled with xenon inert gas. The flash is specially designed such as which is made flash rate about thousands flashes per seconds. The electrical energy is converted into light energy, this is worked by flash tube Laser Discharge Tube &Laser Material The laser material filled in lased discharge tube. The excitation of electron and come back to its original state process takes place in it. It’s one side is partially transparent for laser opening and other side is 100% reflected. It is situated between flash lamp. The Ruby Crys tal is made of aluminium oxide with chromium dispersed throughout it. Which is forming about 1/2000 of crystal, this less than natural ruby.Co2 , Nd - YAG ( Neodymium doped Yttrium Aluminum Garnet Focusing Lens: A focusing lens is used in laser welding operation. It is a convex lens which focused at base metal

41. Working First laser material (Ruby Laser) filled into laser discharge tube. Now switch on the power supplied which is connected by flash lamp. These lamps produce light energy which used to excite electrons of atom. The atoms of laser material absorb energy from the light energy produced by flash lamp. It leads jump of orbital electron of atom form low energy level to high energy level. This is unstable condition of atom. This energy initially build up in laser material. When the atoms absorb sufficient energy it start emit energy continuously. This is high amplified same frequency and same wavelength coherent light. This laser light collected by the focus lens and directed toward the work piece.

42. Advantage of laser beam welding A different type of material can be welded, which material can not be weld by ordinary welding process that also be welded by laser welding process. High melting point and hard material can be weld. By laser welding process different thickness and different diameter materials are welded. Due to its high beam energy both operation welding and cutting can be made very effortlessly. This can be used for micro welding purposes

43. Plasma Arc Welding Plasma arc welding is a liquid state welding process in which, the metal to metal joint forms in molten state. The hot ionized gases are known as Plasma. These hot ionized gases used to heating the work plates, and the joint is created due to fusion. This welding process is same as TIG welding process except plasma is used to weld the work pieces instead of  arc . Filler material may or may not be used in this  type of welding . One big advantage of plasma arc welding is that, it uses less current input compare to  TIG or MIG  processes for produces same heat.

44. Equipment Description &Working

45. Equipment Description Power Source PAW process needed a high power DC supply to generate electric spark in between tungsten electrode and welding plates (For transferred PAW Process) or in between tungsten electrode and discharge nozzle (For Non-transferred PAW process). One of the main features of plasma arc welding which make it different from TIG, is its low ampere welding capability. This welding can weld at low ampere of about 2 amp and maximum current which it can handle is about 300 amp. It needs about 80 volts for proper working. The power source consist transformer and rectifier.

46. Plasma arc torch: This is most important part of PAW process. This torch is quite similar as used in TIG welding but too complex. It consist four main parts which are tungsten electrode, collets, inner nozzle, and outer nozzle. The tungsten electrode is hold by the collet . The collet is available in varying diameters. The inner gas nozzle supply inert gases inside the torch to form plasma. The outside nozzle supply shielding gases which protect the weld area from oxidation.  These nozzles wear out rapidly. PAW torches are water cooled because arc is contained inside the torch which produces high heat, so a water jacket is provided outside the torch.  

47. Shielding and Plasma Gas Supply: Generally, plasma gas is same as shielding gas which is supplied by a same source. Mainly inert gases like argon, Helium etc. are used as both inert and shielding gases. This gas is supplied at both inert and outer nozzles.   Filler Material: Mostly no filler material is used in this welding process. If filler material is used, it is directly feed into weld zone.  

48. Working First the work pieces are properly cleaned. The power source supply power which produces arc between tungsten electrode and nozzle, or tungsten electrode and workpiece . The tungsten electrode gives a high intense arc which is used to ionization of gas particles and converts orifice gases into plasma. This hot ionized gas is supplied to the welding plates from a small orifice. The shielding gases like argon etc. are supplied through pressure valve and regulating valve to the outer nozzle of welding torch. These gases create a shield around the welding area which protect it from atmospheric gases like oxygen, nitrogen etc. The plasma strikes the welding plates and fuses it into one piece. Next the welding torch is moved in the direction of welding. If the welding required filler material, it is fed by the welder manually.

49. Application: This welding is used in marine and aerospace industries. It is used to weld pipes and tubes of stainless steel or titanium. It is mostly used in electronic industries. It is used to repair tools, die and mold . It is used to welding or coating on  turbine  blade. Advantages: High welding speed. High energy available for welding. It can be easily used to weld hard and thick work pieces. The distance between tool and work piece does not effects the arc formation. Low power consumption for same size weld. More stable arc produced by PAW method. High intense arc or high penetration rate. It can work at low amperage. Disadvantages: Higher equipment cost. Noisy operation. More radiation. High skill labour required. High maintenance cost.  

50. Friction Welding Basic Principle Friction welding works on basic principle of friction. In this welding process, the friction is used to generate heat at the interference surface. This heat is further used to join two work pieces by applying external pressure at the surface of work piece. In this welding process, the friction is applied until the plastic forming temperature is achieved. It is normally 900-1300 degree centigrade for steel. After this heating phase, a uniformly increasing pressure force applied until the both metal work pieces makes a permanent joint. This joint is created due to thermo mechanical treatment at the contact surface.

51. Equipment Description&Working

52. Working First both the work pieces are prepared for smooth square surface. One of them is mounted on a rotor driven chuck and other one remains stationary. The rotor allows rotating at high speed thus it makes rotate mounted work piece. A little pressure force is applied on the stationary work piece which permits cleaning the surface by burnishing action. Now a high pressure force applied to the stationary work piece which forces it toward rotating work piece and generates a high friction force. This friction generates heat at the contact surface. It is applied until the plastic forming temperature is achieved. When the temperature is reached the desire limit, the rotor is stopped and the pressure force is applied increasingly until the whole weld is formed. This welding is used to weld those metals and alloys which cannot be welded by other method.  

53. Application For welding tubes and shafts. It is mostly used in aerospace,  automobile , marine and oil industries. Gears, axle tube, valves,  drive line  etc. components are friction welded. It is used to replace  forging  or  casting  assembly. Hydraulic piston rod, truck rollers bushes etc. are join by friction welding. Used in electrical industries for welding copper and aluminum equipment’s. Used in pump for welding pump shaft (stainless steel to carbon steels). Gear levers, drill bits, connecting rod etc. are welded by friction welding. Advantages: It is environment friendly process without generation smoke etc. Narrow heat affected zone so no change in properties of heat sensitive material. No filler metal required. Welding strength is strong in most cases. Easily automated. High welding speed. High efficiency of weld. Wide variety of metal can be weld by this process. Disadvantages: This is mostly used only for round bars of same cross section. Non-forgeable material cannot be weld. Preparation of work piece is more critical              High setup cost. Joint design is limited.

54. Friction Stir Welding Basic Principle Friction stir welding works on same principle of friction welding. In this process, friction is used to generate heat at interface surface. This heat starts  diffusion  process at the mating surface. A high pressure force applied at these mating surfaces which accelerates metal diffusion process and form a metal to metal joint. This is basic principle of  friction welding . In friction stir welding, a rotating tool is used to applied friction and pressure force at the plates. This tool rotates at its own axis and move longitudinally at the plates interface which generates heat by friction between rotating tool and work piece. This heat deformed the interface surface and diffuses the two piece of work piece into one another by applying a high pressure force. This joint is created due to thermo mechanical treatment at the interface surface. One big advantage which makes it versatile welding process is that, it can be easily automated and gives higher metal joining rate. It is mostly used to join aluminium alloy.

55. Equipment Description & Working

56. Working First both the work plates are clamped together same as in butt joint. These both plate's weldable surfaces are in contact with one another. Now a rotating tool pin is inserted into work pieces at the interface surfaces until tool shoulder touched the work piece. This will deform the material plastically due to heating by friction force. This is state of the joining process in which, inter molecular diffusion will deform the material plastically due to heating by friction force.  Now the rotating tool is move forward along the joint line. This will form a joint behind the tool. The tool continuously move unlit the whole weld is form. After the joining process, tool is separated from the work piece. The hole created by tool pin remains in the welding plates.

57. Application: FSW is mostly used in aircraft industries for welding wings, fuel tanks, aircraft structure etc. Used in marine industries for structure work. Used in automotive industries to weld wheel rims, chassis, fuel tanks and other structure work. It is used in chemical industries for joining pipelines, heat exchanger,  air conditioner  etc. Friction stir welding is also used in electronic industries for joining bus bar, aluminum to copper, connectors and other electronic equipment’s. It is widely used in fabrication indust Advantages: It is a solid state welding so does not use flux, filler metal etc. FSW can be used to weld both similar and dissimilar metals. Fine grain size and quality weld can be obtain by this process Lower power consumption due to absence of external heating. Highly automated. Little maintenance required. Large welding joint design available and it can weld in all direction. Easy to operate and does not involve any environmental pollution. Disadvantages: Complicated or special  fixture  arrangement required. It creates a visible hole in welding plates. High initial or setup cost. It is less flexible compare to  arc welding process . FSW cannot make filler joints.  Non Forgeable material cannot be weld. 

58. Ultrasonic Welding Basic Principle Ultrasonic means those vibration waves which have frequency above the normal hearing range. It is about 20000 to 30000 Hz.  It is a solid state welding process. Solid state welding is a welding process in which no external heat is added for welding. It works on the basic principle of energy of ultrasonic wave. Ultrasonic vibration creates a dynamic shear stress between the contacts of two work piece.   Due to local plastic deformation and heat generate due to friction between contact surfaces, joint formation will take place at the interface.  

59. Equipment Description & Wor king

60. Power Supply: The ultrasonic welding needs high frequency and high voltage power supply. This power is needed by the transducer to generate vibrations. Transducer : Transducer is a device which can convert high frequency electric signal into high frequency mechanical vibration. This is connected with the welding head. The converter or piezoelectric transducer used in this welding process. Booster and Horn : The mechanical vibration created by the transducer is supplied to the booster which amplifies this vibration and supply to the horn. Horn is a device which supply this amplified vibration to the welding plates. Fixture or clamping devices: This device is essential in the ultrasonic welding. This uses either electrical, hydraulic, pneumatic or mechanical energy to hold the plates into desire location.

61. Working At the start, high frequency current passes through a piezoelectric transducer. This transducer converts high frequency electrical signal into mechanical vibration. This vibration further supplied to the booster which amplify its frequency. The amplified high frequency vibration passes through horn which is in contact with welding plate. This welding creates lap joint. One plant of the weld is fixed into fixture and other one is in direct contact with horn. These plates are fixed under moderate pressure force. The horn supply high frequency mechanical vibration to the welding plate. Due to this vibration, oscillation shear force act at the interface between welding plates which result electoplastic deformation at interface. It also create a localize temperature rise due to mechanical force and friction. This heat helps in plastic deformation at interface and makes a strong joint without melting of work piece or using filler metal

62. Advantages: This welding can be easily automated and fast. This produces high strength joint without applying external heat. This is clean and provides good surface finish after welding. Ultrasonic process used to weld wide variety of dissimilar metal. It does not develop high heat so there is no chance of expel molten metal form joint. Disadvantages: It does not weld thick harder metal. The thickness of welds about 2.5 mm for aluminium. Tooling cost for fixture is high and they also need special design.  The vibration generates through transducer, can damage electronic component.  Applications: This welding is used in fabrication of nuclear reactor components. It is used in automotive industry for key, head lamp parts, button and switches etc. Ultrasonic is used in electronic industries like armature winding, switches etc. This is clean welding process so it is used in medical industries to make parts like filters, masks etc.