UNIT - II.ppt
- 1. JOINING PROCESSES Fusion welding processes – Types of Gas welding – Equipments used – Flame characteristics – Filler and Flux materials - Arc welding equipments - Electrodes – Coating and specifications – Principles of Resistance welding – Spot/butt, seam welding – Percusion welding - Gas metal arc welding – Flux cored – Submerged arc welding – Electro slag welding – TIG welding – Principle and application of special welding processes - Plasma arc welding – Thermit welding – Electron beam welding – Friction welding – Diffusion welding – Weld defects – Brazing and soldering process – Methods and process capabilities – Filler materials and fluxes – Types of Adhesive bonding.
- 2. Fusion welding The metal at the joint is heated to a molten state and then it is allowed to solidify. E.g. – gas welding , Arc welding, Thermit welding The metal at the joint is heated to a plastic state and are pressed together to make the joint. E.g. – Electric resistance welding, Forge welding Plastic welding
- 3. Types of gas welding 2. Air – Acetylene welding Air taken from the atmosphere and compressed , mixed the acetylene to the required proportion. Temperature is lower than oxy-acetylene welding. 3. Oxy – Hydrogen welding Oxygen and hydrogen gases are mixed with the required proportion. It is used for low temperature welding metals like aluminium, lead. 1. Oxy – Acetylene welding Hottest region - 3200°C Acetylene pressure not more than 1.5atm Oxygen pressure – HP -0.1 to 3.5 bar, LP – 0.5 to 3.5bar,Torch pressure upto 0.06bar. CaC2+2H2O Ca(OH)2+C2H2+127.3 Kj/mol. Metal 2mm to 50mm thick are welded.
- 4. Gas Welding Equipments Oxygen- black (125-140kg/cm2) Acetylene-maroon(16kg/cm2)
- 5. Flame Characteristics 1. Neutral Flame Equal quantity of oxygen and acetylene. Inner cone develops heat to melt the metal. Outer cone are 2. Carburising Flame More acetylene than oxygen. Sharp Inner cone White intermediate cone called feather cone Bluish Outer cone
- 6. Flame Characteristics 3. Oxidising Flame More oxygen than acetylene. Smaller Inner cone Outer cone
- 7. Gas Welding Technique 1. Leftward or Forward Welding 2. Rightward or Backward Welding
- 8. Arc Welding Equipment Heat is developed by an electric arc
- 9. Filler rod – Gas Welding Equipment To supply additional metal to make the joint. Metal rod as a parent metal. D=t/2 + 1 Electrode – Arc Welding Equipment 1. Consumable electrodes It used to produce arc between work and electrode but also provides filler material during welding i. Bare electrode ii.Lightly coated electrode(1-5%) iii. Heavily coated electrode (1to 3mm & 15-30%) 2. Non- Consumable electrodes Made of carbon, graphite which do not consume during welding Arc length remains constant and stable.
- 10. Specification and choice of Electrodes
- 12. 1.0 SPOT WELDING 0.025mm to 1.25mm thickness metal sheats RESISTANCE WELDING
- 13. 2.0 BUTT WELDING 1. Upset butt welding 2. Flash butt welding RESISTANCE WELDING
- 14. 3.0 SEAM WELDING RESISTANCE WELDING
- 15. 4.0 PERCUSSION WELDING RESISTANCE WELDING
- 16. TUNGSTEN INERT GAS WELDING (TIG) GAS TUNGSTEN ARC WELDING (GTAW) Tungsten carbide melting point- 330°c Less than 6.5mm metal thickness
- 17. GAS METAL ARC WELDING (GMAW) MIG – METAL INERT GAS WELDING
- 18. FLUX CORE When the flux is required continuously or where large quantity of flux has to be supplied, on that time the flux is used in the form of wire wound on a rotating drum or reel called as flux core. 1. Submerged Arc welding (SAW)
- 19. 2. Electro Slag welding (ESW) FLUX CORE
- 20. SPECIAL WELDING 2. Thermit welding
- 21. SPECIAL WELDING 3. Electron Beam welding
- 22. SPECIAL WELDING 1. Plasma Arc welding (PAW) a) Non Transferred type
- 23. Power is directly connected to the torch and torch nozzle Tungsten is connected to the negative pole of DC supply and the nozzle to the positive pole. The gas is issued from the nozzle orifice as a high temperature, high velocity plasma jet, cylindrical in shape and of very narrow diameter realizing temperature up to 10000 C The non transferred plasma arc possesses less energy density as compared to transferred arc plasma and used for ceramic or metal plating.
- 25. SPECIAL WELDING 4. Friction welding
- 27. BRAZING Joining of two metal pieces by using a filler metal and the liquid temperature is above 450 deg C. Joining of two metal pieces by using a filler metal and the liquid temperature is below 450 deg C. SOLDERING
- 28. METHODS AND PROCESS CAPABILITES - BRAZING Torch brazing Acetylene, natural gas and butane are combined with air or oxygen. Furnace brazing The heat is supplied by gas or electric heating coils. Induction brazing Heated by placing within the field of high frequency induction coil. Dip Brazing Chemical dip - Filler metal placed in molten bath or flux. Molten metal bath – The assembled parts are first prefluxed and then immersed into molten bath. Resistance brazing Rapid heating minimizes oxidation and the heat affected zone is small Laser brazing and electron beam brazing Laser beam and electron beam are used to join the metal.
- 29. METHODS AND PROCESS CAPABILITES - SOLDERING Hard Soldering The filler metal is silver. Also called as Silver soldering. Soft Soldering Soldering iron is copper rod. Dip Soldering A large amount of solder is melted in a closed tank and parts to be soldered are cleaned and properly dipped in a flux bath. Wave soldering Parts is not dipped into the solder tank but wave is generated in the tank.
- 30. FILLER MATERIALS FLUX MATERIALS 1. Chlorides 2. Borax and boric acid, 3. Borates, 4. Fluorides.
- 31. TYPES OF ADHESIVE BONDING