Unit 4 joining process
- 1. Sanjivani Rural Education Society’s Sanjivani College of Engineering, Kopargaon-423 603 (An Autonomous Institute, Affiliated to Savitribai Phule Pune University, Pune) NAAC ‘A’ Grade Accredited, ISO 9001:2015 Certified Department of Mechanical Engineering Gujrathi Sonam Assistant Professor Sanjivani College of Engineering, Kopargaon E-mail : gujrathisonammech@sanjivani.org.in Contact No: 8483874906 Subject :- Manufacturing Process I (MP I) S.Y. B.Tech. Mechanical Unit 4- Joining Process
- 2. 2 Contents Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon Surface preparation and types of joints. Welding Classification, Defects and Applications. Gas welding - Oxy acetylene gas welding, Hydrogen gas welding. Arc welding - Metal arc welding(SMAW ), Gas metal arc welding, (MIG, MAG) Tungsten inert gas welding, (TIG) Submerged arc welding,(SAW ) Flux cored arc welding(FCAW ), Electrode slag metal arc welding, etc Resistance welding - Resistance but welding, seam welding, spot welding, percussion welding. Thermite welding - Solid state welding - Forge welding, Friction welding, Pressure welding etc
- 3. 3 Introduction Joining processes are used for joining metal parts and in general fabrication work. • Such requirements are generally occur when large/lengthy sections are required in the structure. • Also these processes are applied when steam or water-tight joints are needed. The commonly used joining processes are - • Welding • Soldering • Brazing • Adhesive bonding Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 4. 4 Introduction • It is joining process used for various metals and their alloys. • In these processes, two or more pieces of metals are joined by application of either heat or pressure or both. • In plastic/pressure welding, the metal pieces to be joined are heated to a plastic state and then forced together by external pressure. • In fusion/non-pressure welding, the metal pieces to be joined are heated to molten state and allowed to solidify. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 5. 5 Classification of welding process 1.Arc welding a) Gas tungsten arc welding (TIG) b) Shielded metal arc welding c) Gas metal arc welding (MIG) d) Submerged arc welding e)Plasma arc welding f) Stud arc welding 2. Gas welding a) Oxy-acetylene welding b) Oxy-hydrocarbon welding c) Air-acetylene welding d) Pressure gas welding 3. Resistance welding a)Spot welding b) Seam welding c) Projection welding d) Percussion welding e) Resistance butt welding Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 6. 6 Classification of welding process 4. Solid state welding a) Cold welding b) Friction welding c) Ultrasonic welding d) Diffusion welding e) Explosion welding f) Roll welding 5. Thermo-chemical welding a) Thermit welding b) Atomic hydrogen welding Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 7. 7 Advantages and disadvantages of welding Advantages • A large number of metals or alloys, both similar and dissimilar can be joined by welding. • It can be mechanized. • Strength of welded joint is more. • It provides leak-proof joint. • Welding equipments are not very costly. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 8. 8 Disadvantages - • It gives harmful radiations, fumes and spatter. • Welding results in residual stresses and distortion of the workpiece. • Heat generated in welding process produces metallurgical changes hence, the structure of welded joint is different than that of parent metal. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 9. 9 Applications of welding process • Aircraft construction (welding of engine parts, turbine frames, ducts, etc.) • Rail-road equipments (Air receiver, engine, front and rear hoods, etc.) • Piping's and pipelines (open pipe joints, oil and gas pipelines, etc.) • Pressure vessels and tanks • Buildings and bridges (column base plates, erection of structures, etc.) Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 10. 10 GAS WELDING • Gas welding is done by burning a combustible gas with air or oxygen in a concentrated flame of high temperature. • It can weld most common materials. • Equipment is versatile, inexpensive and serves adequately in many job and general repair shop. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 11. 11 GAS WELDING Maximum temperature in this process is 32000C Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon Oxy-acetylene welding
- 12. 12 GAS WELDING Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon Gas flames
- 13. 13 GAS WELDING a) Leftward or fore-hand welding Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon Gas welding techniques
- 14. 14 GAS WELDING a) Leftward or fore-hand welding • Welder holds blowpipe/welding torch in his right hand and filler rod in left hand. • Welding flame is directed from right to left. • The welding torch is given a small sideways movement and the filler rod should be moved steadily without sideways movement. • This technique is generally used on thin metals i.e. having thickness less than 5 mm. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 15. 15 GAS WELDING Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon b) Rightward (Backward) welding
- 16. 16 GAS WELDING • Welding torch is held in the right hand of the welder and the filler rod in the left hand. • But, welding flame is directed from left to right. • In this, the welding torch has no lateral movement. • In this process, the welding speed is 20-25 % higher and fuel consumption is 15- 25 % lower than the leftward technique. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 17. 17 GAS WELDING Comparison of Rightward and leftward technique Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon SR NO Rightward (Backward) technique Leftward (forward) technique 1 The quality of obtained weld is better. The weld quality is poor than rightward technique. 2 No bevelling is required for welding up to 8.2 mm plate Bevelling is required for welding above 3mm plate thickness. 3 The welding is done from left hand to right hand. The welding is done from right hand to left hand. 4 The total volume of deposited metal is smaller, which reduces the shrinkage and distortion. The total volume of deposited metal is more.
- 18. 18 GAS WELDING Gas welding equipment 1. Oxygen gas cylinder • These are black painted and valve outlets are screwed right handed. • The material used for cylinder is generally steel or alloy steel. 2.Acetylene gas cylinder • These are painted maroon and the valves are screwed left handed. • It is made up of steel 3.Oxygen and acetylene pressure regulators • Used to reduce high pressure of gas in the cylinder to working pressure. • Produce a steady flow, if gas pressure is varying. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 19. 19 GAS WELDING Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 20. 20 GAS WELDING 4. Oxygen and acetylene gas hoses • An oxygen hose is coloured blue and has right handed thread connections, whereas an acetylene hose is red and has left handed thread connections. • They are made up of rubber. 5. Welding torch or blow-pipe 6. Gas welding filler rods and fluxes 7. Goggles and gloves 8. Spark lighter Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 21. 21 GAS WELDING Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 22. 22 GAS WELDING Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 23. 23 GAS WELDING Advantages • Operator has control over the temperature of weld zone. • The rate of heating and cooling is relatively slow. • The equipment is versatile, low cost, self-sufficient and generally portable. • Low equipment and maintenance cost. Disadvantages • Refractory and reactive metals cannot be welded. • More time is required than arc welding. • More safety problems are associated with the handling and storing of gases. • Fluxes used in welding produces fumes that are irritating to the eyes, nose, throat and lungs. • Heavy sections cannot be welded economically. Applications • Joining thin materials • Joining most ferrous and non-ferrous metals • In automobile and aircraft industries • In sheet metal fabricating plant Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 24. 24 Arc welding • Arc welding is the most expensive employed method of joining metal parts. • Source of heat is an electric arc. • The arc column is generated between an anode, which is the positive pole of DC power supply, and the cathode, the negative pole. • When these two conductors of an electric circuit are brought together and separated for a small distance of 2 – 4mm such hat the current continues to flow through a path of ionized particles, called plasma, an electric arc is formed. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 25. 25 Arc welding Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 26. 26 Arc welding • It is a fusion welding process in which welding heat is obtained from an electric arc between an electrode and the workpiece. • The temperature produced at the centre of an arc is 6000 to 70000C. • In this, the base metal is melted by the temperature of the arc, forming a pool of molten metal. • Either A. C. or D. C. supply is used. • The electrodes used in the process are of two types i.e. bare and coated electrodes. • The length of electrodes varies from 250 mm to 450 mm. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 27. 27 Advantages • It is most versatile process which can be applied for both thick and thin sections. • Welding of complicated shapes can also be done. • Welding can be done in any position with high weld quality. • Welded parts are neat and smooth. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon Arc welding
- 28. 28 Arc welding Disadvantages • As the electrodes are coated, the chances of slag entrapment and their related defects are more. • Welding control is difficult. • The process needed filler material. • It is a slow process. Applications • Air receiver, boilers, pressure vessels fabrication • Automobile, chemical and aircraft industry • Ship building and bridge construction Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 29. 29 Arc welding • A.C. or D.C. machine • Electrode and holder Bare electrodes Coated electrodes Consumable electrodes Non consumable electrodes • Filler rod and fluxes • Cables and cable connector • Earthing clamps • Chipping hammer • Wire brush • Helmet, safety goggles, hand glove, aprons, sleeves etc. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 30. 30 Arc welding ARC welding Methods - • Gas tungsten arc welding (TIG) • metal inert gas welding (MIG) • Submerged arc welding • Plasma arc welding • Flux cored arc welding • Carbon arc welding • Metal arc welding • Electro slag welding • Atomic hydrogen arc Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 31. 31 Arc welding - TIG Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon • Gas tungsten arc welding (TIG) • Uses intense heat of an electric arc between non consumable tungsten electrode and the material to be welded. • The shielding is obtained from an inert gas such as helium or argon or a mixture of the two. • It produces high quality welds in nonferrous metals. • No weld cleaning is necessary • The arc and weld pool are clearly visible to the welder
- 32. 32Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon • Metal inert gas welding (MIG) Uses a high heat of an electric arc between a continuously fed, consumable electrode wire and the material to be welded. • In this process the wire is fed continuously from a reel through a gun to constant surface which imparts a current upon the wire. • The current ranges from 100 – 400 A depending upon the diameter of the wire • The welding gun can be either air or cooled depending upon the current being used. • Advantages – no flux is required, high welding speed, increased corrosion resistance, easily automated welding, high economy, welds all metals including aluminum and stainless still Arc welding - MIG
- 33. 33 Arc welding - MIG Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 34. 34 Arc welding – Submerged arc • Sometimes called hidden arc or subarc welding • The arc is formed between the end of a continuous depositing surface, under the layer of protective mineral powder flux or melt, which can also be used to add alloying elements to the joint ahead of the welding wire and while the weld is being made the arc is submerged under the powder and is invisible Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 35. 35 Arc welding - Plasma arc welding Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon • Plasma is high temp ionized gas and occurs in any electric arc between two electrodes • The main function of the plasma gas is shielding the body of the torch from the extreme heat of the cathode. • In this process the penetration is deep and through, and much work can be done without filler metal. • Any known material is melted, even vaporized by the plasma arc process • Results are clean and 2 – 5 times as fast as TIG welding with same equipment cost • It requires automatic control and is not practical for short welds.
- 36. 36 Arc welding - Plasma arc welding Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 37. 37 Arc Welding - Flux cored arc welding • The inner core type welding is an inside out wire with the flux inside a tubular electrode. • The equipment needed is simple : a constant voltage dc power source, a wire feeder and a lightweight gun, which is like the MIG holder without gas and cooling attachment. So continuous welding is possible. • The welds are strong and tough Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 38. 38 Arc Welding - Carbon arc welding • In this method, a rod of carbon is used as negative electrode and the work being welded as positive. The reason to use carbon rod as negative electrode is that less heat will be generated at the electrode tip than that at the workpiece and carbon from the electrode will not fuse and mix up with the job. • The process is best to the joints which need to be melted without the addition of filler. • The process is used for welding sheet steel, copper alloys, brass, bronze and aluminium Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 39. 39 Arc Welding - Metal arc welding • A melt rod is used as one electrode while the work being welded is used as another electrode. • Both AC and DC may be used. • A welding shows different bead characteristic under different conditions : • Welding current too low – excessive pilling of the metal • Welding current too high – causing excessive splatter • Welding too high – bead too small • Welding speed too slow – cause excessive pilling up of weld metal • Proper current and timing – create smooth, regular, well formed bead. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 40. 40 Arc Welding - Electro slag welding • It produces coalescence through electrically melted flux which melts both the filler metal and the surface of the workpiece to be melted. • The consumable wire electrode may be solid or flux coated but most or all of the shielding is provide by an argon and co2 gas mixture injected into the gap. • It is used particularly for welding thick (25mm or over) plates and structures for turbine shafts, boiler parts and heavy presses Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 41. 41 Arc Welding - Atomic hydrogen arc • An AC arc is maintained between the two non consumable tungsten electrodes while a stream of hydrogen gas under a pressure of about 0.5 kgf/cm2 is passed through the arc and around the electrode. • It is capable of producing smooth, uniform, strong and ductile welds. • For welding of stainless steel, non ferrous metal, alloy steel Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 42. 42 Difference Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon SR NO TIG MIG 1 Non-consumable electrodes are used Consumable wires are used 2 Tungsten or tungsten alloys electrode are used. Bare welding wire is made of desired composition. 3 Electrode generate only arc. Electrodes generates arc and melt also. 4 Easier for thin and small parts Widely used for thick plates. 5 Welding torch is water cooled. Welding torch is air or water cooled. 6 Used for joining dissimilar metals. Used for joining similar metals. 7 It is a slow process. Fast process.
- 43. 43 Resistance Welding • In this process, coalescence is produced by the heat obtained from resistance offered by the workpiece. Factors involved in resistance welding • Current • Pressure • Time • Area of electrode tip • 𝑯=𝑰2Rt • Copper electrodes are used Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 44. 44 Resistance Welding Advantages • Rate of production is high. • Filler rod is not required. • The equipments used are semi-automatic. • Less-skilled operators are required for the operation. • Both similar and dissimilar metals can be welded. • High reliability and reproducibility of welding joints are obtained. Limitations • High initial cost. • Skilled persons are required for maintenance of equipment. • In some materials, special surface preparation is required. • Workpieces of higher thickness cannot be welded. Applications • Joining of sheets, bars, rods and tubes. • Making of tubes and furniture. • Welding of aircraft and automobile parts. • Making of cutting tools, fuel tanks of cars, tractors, etc. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 45. 45 Resistance Welding Types of Resistance welding • Spot welding – Applications • Used in automobile and aircraft industries • For joining sheet metal stampings Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 46. 46 Resistance Welding • Types of Resistance welding • Seam welding - Applications Welding of low carbon, high carbon and low alloy steels, Al, Ni, Mg and their alloys These welds can be done in square, round or rectangular parts Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 47. 47 Resistance Welding Types of Resistance welding • Projection welding Applications – • Mostly used in automobile industries • Small fasteners, nuts can be welded to large components • Welding of Naval brass alloys, stainless steel and titanium alloys Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 48. 48 Types of welded joint Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon Lap or fillet weld 1. Lap joint or fillet joint 2. Butt joint A – single transverse fillet B – double transverse filet C – parallel fillet
- 49. 49 Welding defects Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 50. 50 Solid state welding • Interatomic bonds may be established by bringing atoms of two surfaces in close enough proximity to assure adhesion • Relative movement of the surfaces under pressure and controlled roughness are helpful in breaking through surface films. • While theoretically no pressure would be required for bonding, in practice pressure is necessary to assure conformity with the contacting surface. • Solid state welding is often applied when other techniques fail. • It include : friction, ultrasonic, diffusion Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 51. 51 Solid state welding • Diffusion – • It needs two kinds of surfaces that can come into intimate contact under pressure. This pressure is applied for a period of hours. • This process makes it possible to join metal to metal, metal to ceramic with intermediate bonding materials. Temp that approaches is approximately 900 degree Celsius Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 52. 52 Solid state welding • Ultrasonic welding • Ultrasonic welding will join similar or dissimilar metals by the introduction of high frequency vibratory energy into overlapping metals into the area to be joined. • No flux, filler metal, electric current and heat • High frequency vibratory energy is then transmitted into the weld area for a brief interval • The maximum thickness by this process may vary from 0.38 – 2.5 mm depending upon metal Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 53. 53 Solid state welding • Friction welding • The frictional energy generated when two bodies slide on each other is transformed into heat ; when the rate of movement is high and the heat is contained in a narrow zone, welding occurs. • Dissimilar metals are easily joined Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 54. 54 Brazing • A process that uses a metal alloy that melts above 840°F, but less than the melting point of the base metal. • Brazing relies on capillary action to draw the filler metal into the joint or to keep it in the joint. • The capillary effect is a function of the ability of the liquid to wet a particular material. • Requires very small gap between metal surfaces, clean surfaces and flux. • In case of brazing joining of metal pieces is done with the help of filler metal. • Filler metal is melted and distributed by capillary action between the faying surfaces of the metallic parts being joined. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 55. 55 Brazing • The filler metal is drawn through the joint to create this bond is capillary action. In a brazing operation, you apply heat broadly to the base metals. The filler metal is then brought into contact with the heated parts. It is melted instantly by the heat in the base metals and drawn by capillary action completely through the joint Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 56. 56 Soldering • Soldering is very much similar to brazing. • The major difference lies with the filler metal, the filler metal used in case of soldering should have the melting temperature lower than 450°C. • Soldering is normally done by melting the solder with a soldering iron and applying it to the two metals that are going to be joined together. • The filler metal used in the process is called solder, which distributes between the closely fitted surfaces. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 57. 57 Advantages of Brazing & Soldering • Joining dissimilar metals and non-metals. • Low temperature compared to welding. • less thermal distortion. • Less chance of damage • Speed of joining. • Less manual skills. Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 58. 58 Braze Welding • Also called as bronze welding • Bronze welding does not mean the welding of bronze but it is welding using bronze filler rod. • It is a method of welding where a groove, fillet, plug or slot is made by using a non ferrous filler material having a melting point below that of the parent metal but above 427 ° C Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 59. 59 Comparison points • Write down comparison points between – soldering and brazing • Soldering, brazing and welding • Arc welding, gas welding and resistance welding • Comparison between all types of arc welding Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
- 60. 60 Thank You Gujrathi S.M. Department Of Mechanical Engineering, Sanjivani COE, Kopargaon