Welding Classification, Welding technology is a materials joining process which produces coalescence of materials by heating them to suitable temperatures with or without the application of pressure or by the application of pressure alone, and with or without the use of filler material.
Welding is used for making permanent joints. It is used in the manufacture of automobile bodies, aircraft frames, railway wagons, machine frames, structural works, tanks, furniture, boilers, general repair work and ship building.
For those of you who are interested in learning about welding, it is better to know first the types of welding that exist in the world of welding. In this article, we have summarized the types of welding methods that are widely used by the world welding community.
Weld joint
There are 5 basic joint types in welding
• Butt joint: Two materials are in the same plane, joined from the edges.
• Corner joint:The corners of two materials form a right angle and joined.
• Lap joint: Two parts overlaps.
• Tee joint: One part is perpendicular to the other, making a T shape.
• Edge joint: Edges of the two materials joined.
Types of weld
1. Fillet weld: Used in T joints,corner joints, lap joints.
2. Groove weld:Used in butt joints.
3. Plug weld: Used in lap joints.
4. Slot weld: Used in lap joints.
5. Spot weld: Used in lap joints.
6. Seam weld: Used in lap joints.
7. Flange weld:Used in edge joints.
8. Surfacing weld:Not a joining process, it is used to increase the thickness of the plate, or provide a protective coating on the surface
Welding Classification, Weldability is the ease of a material or a combination of materials to be welded under fabrication conditions into a specific, suitably designed structure, and to perform satisfactorily in the intended service
Brazing and Soldering
Brazing
Welding Classification, It is a low temperature joining process. It is performed at temperatures above 840º F and it generally affords strengths comparable to those of the metal which it joins. It is low temperature in that it is done below the melting point of the base metal. It is achieved by diffusion without fusion (melting) of the base
Depending upon the method of heating, brazing can be classified as
1. Torch brazing
2. Dip brazing
3. Furnace brazing
4. Induction brazing
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Advantages
Ø Dissimilar metals which canot be welded can be joined by brazing
Ø Very thin metals can be joined
Ø Metals with different thickness can be joined easily
Ø In brazing thermal stresses are not produced in the work piece. Hence there is no distortion
Ø Using this process, carbides tips are brazed on the steel tool holders
Disadvantages
Ø Brazed joints have lesser strength compared to welding
Ø Joint preparation cost is more
Ø Can be used for thin sheet metal sections
Soldering
Welding Classification, Soldering It is a low temperature joining process. It is performed at temperatures below 840ºF for joining.
Soldering is used for,
• Sealing, as in automotive radiators or tin cans
• Electrical Connections
• Joining thermally sensitive components
• Joining dissimilar metals
In general, welding is divided into 4 groups, namely, Gas Welding, Arc Welding (Electric Welding), Press Welding, and high-Energy beam welding. The 4 welding groups still have other types of welding in each group, such as the Arc Welding group which is most commonly used by individuals and industry which has several types of methods, including; Shielded metal arc welding (SMAW), Gas-tungsten arc welding (GTAW), Plasma arc welding (PAW), Gas-metal arc welding (GMAW), Flux-cored arc welding (FCAW), Submerged arc welding (SAW), Electro Slag welding (ESW).
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1. Welding Classification, Gas welding:
a. Oxyacetylene welding (OAW)
Welding Classification, Acetylene welding or Oxyacetylene Welding, commonly called gas welding, is a process that uses oxygen and acetylene combustion. When the two are mixed together in the correct proportions in a torch , it will produce a relatively hot flame with a temperature of around 3,200 degrees Celsius. The oxyacetylene flame can be regulated by changing the ratio of the volume of oxygen to acetylene.
b. 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
7. Non return valve
c. TYPES OF FLAMES
• When acetylene is burned in air, it produces a yellow sooty flame, which is not enough for welding applications
• 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)
• This flames are used for hardening the surfaces
• 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)
• Most commonly used flame because it has temperature about 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
Advantages
– Equipment has versatile
– Same equipment can be used for oxy acetylene cutting and brazing by varying the torch size
– Heat can controlled easily
Disadvantages
– Slower process
– Risk is involved in handling gas cylinders
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GAS CUTTING
• Ferrous metal is heated in to red hot condition and a jet of pure oxygen is projected onto the surface, which rapidly oxidizes
• Oxides having lower melting point than the metal, melt and are blown away by the force of the jet, to make a cut
• Fast and efficient method of cutting steel to a high degree of accuracy
• Torch is different from welding
• Cutting torch has preheat orifice and one central orifice for oxygen jet
• PIERCING and GOUGING are two important operations
• Piercing, used to cut a hole at the centre of the plate or away from the edge of the plate
• Gouging, to cut a groove into the steel surface
2. Welding Classification, Arc welding (Electric Arc Welding):
a. Shielded metal arc welding (SMAW)
Welding Classification, This is the most popular welding process capable of producing a wide variety of welds. This welding uses electrodes coated with a protective flux of a suitable composition. The flux melts together with the metal core of the electrode to form gas and slag. The flux cleans the metal surface, supplies some of the alloying elements to the weld, protects the molten metal from oxidation and stabilizes the arc.
b. Gas-tungsten arc welding (GTAW)
Welding Classification, This type of welding is also known as tungsten inert gas or TIG welding. In the process, metal smelting is produced by heating with an arc between the base metal and the tungsten electrode, the tungsten electrode does not melt because it only serves to maintain the arc. The shielding gas used is usually helium or argon.
c. Gas-metal arc welding (GMAW)
Welding Classification, This type of welding is also called Metal Inert Gas (MIG) welding, the welding process is heat generated by an electric arc equipped with a continuously melting electrode protected by an external gas, the external gas used is usually helium, argon, or carbon dioxide.
d. Flux-cored arc welding (FCAW)
Welding Classification, Flux cored arc welding (FCAW) is a center core flux electric arc welding / center core shielding. This type of welding is a combination of SMAW, GMAW and SAW processes. Welding energy sources use AC or DC electric current from power plants or through transformers and or rectifiers. FCAW is a type of electric welding that supplies the filler electrode mechanically to the electric arc formed between the filler electrode tip and the parent metal. The shielding gas also uses carbon dioxide CO2
e. Submerged arc welding (SAW)
Welding Classification, Submerged Arc Welding (SAW) is a joining process that involves the formation of an electric arc between a continuously fed electrode and the workpiece to be welded. Welding in which an arc is generated between the filler rod electrode and the workpiece covered with flux grains which are used to protect against atmospheric contamination.
f. Electro Slag welding (ESW)
Welding Classification, This type of welding is used to connect metal that has a thickness of > 30 mm.
3. Welding Classification, Welding Press:
a. Friction Stir Welding (FSW)
b. Resistance Spot Welding (RSW)
4. Welding Classification, High-energy beam welding:
a. Electron beam welding (EBW)
b. Laser beam welding (LBW)
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