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gas welding

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just keep some basic in mind, its give u enough information about this topic.

just keep some basic in mind, its give u enough information about this topic.

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  • 1. GAS WELDING
  • 2. Gas Welding • Gas welding is a welding process that melts and joins metals by heating them with a flame caused by a reaction of fuel gas and oxygen. • The most commonly used method is Oxyacetylene welding, due to its high flame temperature. • The flux may be used to deoxidize and cleanse the weld metal. • The flux melts, solidifies and forms a slag skin on the resultant weld metal.
  • 3. Oxyacetylene Welding • Utilizes oxygen and a fuel gas to heat metal until it is in a molten state and fuse multiple pieces of metal together. Can be used with or without a filler rod. • Great for brazing dissimilar metals together. • Older technology that can be replaced by GTAW
  • 4. Oxyacetylene Welding •Also known as “oxyacetylene welding” •Uses an oxyfuel gas flame •Can be applied with or without pressure •Can be applied with or without the use of filler materials
  • 5. Gas Welding • Oxy-acetylene Welding: CaC2 + 2H2O = Ca (OH) 2 + C2H2 C2H2+2.5O2= 2CO2+H2O(vapour)+ 306.800 cal /mol
  • 6. Chemical reactions and temperature distribution in a neutral oxyacetylene The secondary combustion is also called the protection envelope since CO and H2 here consume the O2 entering from surrounding air, thereby protecting the weld from oxidation.
  • 7. Oxyacetylene Welding • Flame formed by burning a mix of acetylene (C2H2) and oxygen • Fusion of metal is achieved by passing the inner cone of the flame over the metal • Oxyacetylene can also be used for cutting metals
  • 8. Oxyacetylene Welding Uses a high-temperature flame from the combustion of acetylene and oxygen
  • 9. Gas Welding Oxyacetylene welding (a) overall process, (b) welding area.
  • 10. GAS WELDING • Sound weld is obtained by selecting proper size of flame, filler material and method of moving torch • The temperature generated during the process is 33000c • When the metal is fused, oxygen from the atmosphere and the torch combines with molten metal and forms oxides, results defective weld • Fluxes are added to the welded metal to remove oxides • Common fluxes used are made of sodium, potassium. Lithium and borax. • Flux can be applied as paste, powder,liquid.solid coating or gas.
  • 11. TYPES OF FLAMES
  • 12. Types of Flame • There are three types of flames in oxyacetylene welding: • Neutral flame - Acetylene (C2H2) and O2 are mixed in equal amounts and burn at the tip of the welding torch. The inner cone gives 2/3 of heat whereas the outer envelope provides 1/3 of the energy. • Reducing flame - The excess amount of acetylene is used, giving a reducing flame. The combustion of acetylene is incomplete (greenish) between the inner cone and the outer envelope. Good for welding aluminium alloys, high carbon steels. • Oxidizing flame - The excess amount of O2 is used, giving an oxidizing flame. Good for welding brass.
  • 13. Three types of flame in oxyacetylene welding
  • 14. TYPES OF FLAMES • Oxygen is turned on, flame immediately changes into a long white inner area (Feather) surrounded by a transparent blue envelope is called Carburizing flame (30000c) • Addition of little more oxygen give a bright whitish cone surrounded by the transparent blue envelope is called Neutral flame (It has a balance of fuel gas and oxygen) (32000c) • Used for welding steels, aluminium, copper and cast iron • If more oxygen is added, the cone becomes darker and more pointed, while the envelope becomes shorter and more fierce is called Oxidizing flame • Has the highest temperature about 34000c • Used for welding brass and brazing operation
  • 15. Three basic types of oxyacetylene flames used in oxyfuel-gas welding and cutting operations: (a) neutral flame; (b) oxidizing flame; (c) carburizing, or reducing flame.
  • 16. Three basic types of oxyacetylene flames used in oxyfuel-gas welding and cutting operations: (a) neutral flame; (b) oxidizing flame; (c) carburizing, or reducing flame.
  • 17. Types of Gas Welding • 1. Leftward Welding • 2. Rightward Welding
  • 18. Gas welding two types
  • 19. GAS WELDING EQUIPMENTS
  • 20. GAS WELDING EQUIPMENTS 1. Gas Cylinders Pressure Oxygen – 125 kg/cm2 Acetylene – 16 kg/cm2 2. Regulators Working pressure of oxygen 1 kg/cm2 Working pressure of acetylene 0.15 kg/cm2 Working pressure varies depending upon the thickness of the work pieces welded. 3. Pressure Gauges 4. Hoses 5. Welding torch 6. Check valve 7. Non return valve
  • 21. Oxy-Acetylene welding
  • 22. Gas welding Apparatus 1. Oxygen cylinder 2. Acetylene cylinder 3. Pressure gauges 4. Valves 5. Hose pipes 6. Torch 7. Welding tip 8. Pressure regulators 9. Lighter 10. Goggles
  • 23. Gas welding torch
  • 24. Gas Welding - Advantages • Simple equipment • Portable • Inexpensive • Easy for maintenance and repair
  • 25. Gas Welding - Disadvantages • Limited power density • Very low welding speed • High total heat input per unit length • Large heat affected zone • Severe distortion • Not recommended for welding reactive metals such as titanium and zirconium.