A FABRICATION PROCESS PRESENTED BY- RISHABH YADAV 14001001045 WELDING : A FABRICATION PROCESS PRESENTED BY- RISHABH YADAV 14001001045
INTRODUCTION TO WELDING It is a process of joining two similar or dissimilar metals by fusion, with or without the application of pressure and with or without the use of filler metal. The fusion of metal takes place by means of heat. The heat may be obtained from electric arc, electric resistance, chemical reaction or radiant energy.
Types of welding Autogeneous : Joining similar metals without addition of filler metal Homogeneous : Joining similar metals with the help of filler rod of same metal. Heterogeneous : Joining dissimilar metals using filler rod.
Classification of welding (i). Arc welding Carbon arc Metal arc Metal inert gas(MIG) Tungsten inert gas(TIG) Plasma arc Submerged arc Electro-slag (ii) Gas Welding Oxy-acetylene Air-acetylene Oxy-hydrogen (iii) Resistance Welding Butt Spot Seam Projection Percussion (iv) Solid State Welding Friction Ultrasonic Diffusion Explosive (v) Newer Welding Electron-beam Laser (vi) Related Process Oxy-acetylene cutting Arc cutting Hard facing Brazing Soldering
Welding Joints and Weld Positions
Some Basic Joints LAP JOINT : The lap joint is obtained by overlapping the plates and then welding the edges of the plates.
Butt joint : It is obtained by welding the ends or edges of the two plates. Square butt joint Single V-butt joint Double V-butt joint Single U-butt joint
Corner joint : The corner joint is obtained by joining the edges of two plates whose surfaces are at an angle of approx. 90 degrees to each other.
GAS WELDING It is also called an oxy-fuel gas welding, derives the heat from the combustion of a fuel gas such as acetylene in combination with oxygen. It is a fusion welding process wherein joint is completely melted to obtain the fusion. The fuel gas used is acetylene because of the high temperature generated in the flame.
GAS WELDING EQUIPMENT 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 depends upon the thickness of the work pieces welded. 3. Pressure Gauges 4. Hoses 5. Welding torch 6. Check valve
Oxy-Acetylene welding
TYPES OF FLAMES NEUTRAL FLAME : 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) Used for welding steels, aluminium, copper and cast iron
OXIDISING FLAME : If more oxygen is added, the cone becomes darker and more pointed, while the envelope becomes shorter and more fierce is called Oxidizing flame Used for welding brass and brazing operation
CARBURISING FLAME : Oxygen is turned on, flame immediately changes into a long white inner area (Feather) surrounded by a transparent blue envelope is called Carburizing flame.
ADVANTAGES OF GAS WELDING Equipment is having less cost. No electric current is required. Operator is having better control because sources of heat and filler metals are seperate. It can be applied to wide variety of manufacturing and maintenance situations.
DISADVANTAGES OF GAS WELDING Flame temp. is less than the temp. of the arc. Heat affected zone is higher. Gas flame takes a long time to heat up the metal than an arc. Refractory metals (tungsten, molybdenum etc.) and reative metals (titanium and zicronium) cannot be gas welded.
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