Mechanical Engineering Community

# saurabhjain

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1. ## What is the difference between topping and bottoming cycle ?

Topping-cycle systems produce electricity first, then recover the excess thermal energy for heating or cooling applications. By contrast, bottoming-cycle systems, also known as “waste heat to power,” are a process whereby waste heat from an existing process is used to produce electricity.
2. ## let all of us be active on Mechanical engineering forum

couple of points your site.. this is site of all members - this is a community... read how every one is writing here on this link When you write the answer .. you are demonstrating your knowledge...

6. ## forging

From the album: Engineering images 10

7. ## constant mesh gearbox.jpg

From the album: Gears

Construction: It is made up of following components: 1. Counter shaft or Lay Shaft: This shaft is in direct contact with the clutch and the main shaft. Keeping in mind according to the gear ratio, the speed of the counter shaft may be less that the speed of the engine. The gear ratio can be defined as the ratio of the teeth of driven gear to the teeth of the driver gear. 2. Main shaft: This shaft operates the speed of the vehicle. The power is made available to the main shaft through the gears from the counter shaft. This is done in accordance with the gear ratio. 3. Dog clutch: Dog clutch is special feature of constant mesh gearbox. It is used for the coupling of any two shafts. This is done by interference. Using a dog clutch, various gears can be locked to the output and input shafts. 4. Gears: The main work of the gears is the transmission of power between the shafts. If the gear ratio is more than one, the main shaft will work at a speed that is slower than the counter shaft, and vice versa. The arrangement of both reverse, as well as forward gears, is present.

9. ## Simple Machines

Quiz author has to click button .. "Allow playing" .. this is because ..he has added 7 questions and the quiz is not ready -- may be he is adding 3 more questions... once he click on allow playing.... the quiz be open for every one .... And I can see - he has added quiz but nit added any questions......
10. ## Plasma Arc Welding

From the album: Engineering images 10

In plasma-arc welding (PAW), developed in the 1960s, a concentrated plasma arc is created and directed towards the weld area. The produced arc is stable and reaches temperatures around 33,000°C. Plasma is an ionized hot gas composed of nearly equal numbers of electrons and ions. The plasma is started between the tungsten electrode and the orifice by a low-current pilot arc. What creates plasma-arc welding unlike other processes is that the plasma arc is concentrated because it is forced through a relatively small orifice Plasma Arc Welding Torch Operating currents generally are below 100 A, but they can be superior for special applications. While a filler metal is used, it is fed into the arc, as is made in GTAW. Arc and weld-zone shielding is supplied by means of an outer-shielding ring and the use of gases like the following argon, helium, or mixtures.
11. ## types of chip.jpg

Type of chips Continuous chips Discontinuous chips Built up Chips
12. ## Types of Clutches

In an automobile, the engineproduces power and this power is carry to the wheels by use of power train. The first element of this train isclutch. The main function of the clutch is to engage and disengages the engine to the wheel when the driver need or when shifting the gears. Basically clutch may be classified as follow. Types of Clutches: These may classified as follow: According to the method of transmitting torque: 1. Positive clutch (Dog clutch): In the positive clutch, grooves are cut either into the driving member or into the driven member and some extracted parts are situated into both driving and driven member. When the driver releases clutch pedal then these extracted parts insert into grooves and both driving and driven shaft revolve together. When he push the clutch pedal these extracted parts come out from grooves and the engine shaft revolve itself without revolving transmission shaft. 2. Friction clutch: In this types of clutches, friction force is used to engage and disengage the clutch. A friction plate is inserted between the driving member and the driven member of clutch. When the driver releases the clutch pedal, the driven member and driving member of clutch, comes in contact with each other. A friction force works between these two parts. So when the driving member revolves, it makes revolve the driven member of clutch and the clutch is in engage position. This type of clutch is subdivided into four types according to the design of the clutch. A.) Cone clutch: It is a friction type of clutch. As the name, this type of clutch consist a cone mounted on the driven member and the shape of the sides of the flywheel is also shaped as the conical. The surfaces of contact are lined with the friction lining. The cone can be engage and disengage form flywheel by the clutch pedal. B.) Single plate clutch: In the single plate clutch a flywheel is fixed to the engine shaft and a pressure plate is attached to the gear box shaft. This pressure plate is free to move on the spindle of the shaft. A friction plate is situated between the flywheel and pressure plate. Some springs are inserted into compressed position between these plates. When the clutch pedal releases then the pressure plate exerts a force on the friction plate due to spring action. So clutch is in engage position. When the driver pushes the clutch pedal it due to mechanism it serves as the disengagement of clutch. C.) Multi-plate clutch: Multi-plate clutch is same as the single plate clutch but there is two or more clutch plates are inserted between the flywheel and pressure plate. This clutch is compact then single plate clutch for same transmission of torque. D.) Diaphragm clutch: This clutch is similar to the single plate clutch except diaphragm spring is used instead of coil springs for exert pressure on the pressure plate . In the coil springs, one big problem occur that these springs do not distribute the spring force uniformly. To eliminate this problem, diaphragm springs are used into clutches. This clutch is known as diaphragm clutch. 3. Hydraulic clutch: This clutch uses hydraulic fluid to transmit the torque. According to their design, this clutch is subdivided into two types. A.) Fluid coupling: It is a hydraulic unit that replaces a clutch in a semi or fully automatic clutch. In this type of clutch there is no mechanical connection between driving member and driven member. A pump impeller is blotted on a driving member and a turbine runner is bolted on the driven member. Both the above unit is enclosed into single housing filled with a liquid. This liquid serve as the torque transmitter form the impeller to the turbine. When the driving member starts rotating then the impeller also rotates and through the liquid outward by centrifugal action. This liquid then enters the turbine runner and exerts a force on the runner blade. This make the runner as well as the driven member rotate. The liquid from the runner then flows back into the pump impeller, thus complete the circuit. It is not possible to disconnect to the driving member to the driven member when the engine is running. So the fluid coupling is not suitable for ordinary gear box. It is used with automatic or semi-automatic gear box. B.) Hydraulic torque converter: Hydraulic torque converter is same as the electric transformer. The main purpose of the torque converter is to engage the driving member to driven member and increase the torque of driven member. In the torque converter, an impeller is bolted on the driving member, a turbine is bolted on the driven member and a stationary guide vanes are placed between these two members. This all parts are enclosed into single housing which filled with hydraulic liquid. The impeller rotates with the driven member and it through the liquid outward by centrifugal action. This liquid flowing from the impeller to turbine runner exerts a torque on the stationary guide vanes which change the direction of liquid, thereby making possible the transformation of torque and speed. The difference of torque between impeller and turbine depends upon these stationary guide vanes. The hydraulic torque converter is serve the function of clutch as well as the automatic gear box. According to the method of engaging force: 1. Spring types clutch: In this types of clutches, helical or diaphragm springs are used to exert a pressure force on the pressure plate to engage the clutch. These springs are situated between pressure plate and the cover. These springs are inserted into compact position into the clutch. So when it is free to move between these two members, it tends to expand. So it exert a pressure force on the pressure plate thus it brings the clutch in engage position. 2. Centrifugal clutch: As the name in the centrifugal clutch, centrifugal force is used to engage the clutch. This type of clutch does not require any clutch pedal for operating the clutch. The clutch is operated automatically depending upon engine speed. It consist a weight pivoted on the fix member of clutch. When the engine speed increase the weight fly of due to the centrifugal force, operating the bell crank lever, which press the pressure plate. This makes the clutch engage. 3. Semi-centrifugal clutch: One big problem occur in centrifugal clutch is that they work sufficient enough at higher speeds but at lower speed they don’t do their work sufficiently. So the need of another type of clutch occurs, which can work at higher speed as well as at lower speed. This type of clutch is known as semi-centrifugal clutch. This type of clutch uses centrifugal force as well as spring force for keeping it in engaged position. The springs are designed to transmit the torque at normal speed, while the centrifugal force assists in torque transmission at higher speeds. 4. Electro-magnetic clutch: In the electromagnetic clutch electro-magnate is used to exert a pressure force on pressure plate to make the clutch engage. In this type of clutch, the driving plate or the driven plate is attached to the electric coil. When the electricity is provide into these coils then the plate work as the magnate and it attract another plate. So both plates join when the electricity provides and the clutch is in engage position. When the driver cut the electricity, this attraction force disappear, and the clutch is in disengage position. According to the method of control: 1. Manual clutch: In this type, clutch is operate manually by the driven when he need or when shifting the gear. This type of clutch uses some mechanical, hydraulical or electrical mechanism to operate the clutch. All friction clutches are include in it. 2. Automatic clutch: This type of clutch used in modern vehicle. This clutch has self operated mechanism which control the clutch when the vehicle need. Centrifugal clutch, hydraulic torque converter and fluid coupling includes in it. This type of clutch is always used with the automatic transmission box.

14. ## saurabhjain

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15. ## Overhead Cam Engine & Pushrod

From the album: Engineering images 10

Overhead valve, also commonly called pushrod, engines are a simplified V-style design. These are built to be compact and resistant to oil contamination and are often used in small displacement racing.In consumer automotive, however, the pushrod engine has largely been replaced by the SOHC and DOHC designs....

Extrusion is a metal forming process in which metal or work piece is forced to flow through a die to reduce its cross section or convert it into desire shape. This process is extensively used in pipes and steel rods manufacturing. The force used to extrude the work piece is compressive in nature. This process is similar to drawing process except drawing process uses tensile stress to extend the metal work piece. The compressive force allows large deformation compare to drawing in single pass. The most common material extruded are plastic and aluminum. Extrusion Process: Working Principle: Extrusion is a simple compressive metal forming process. In this process, piston or plunger is used to apply compressive force at work piece. These process can be summarized as follow. First billet or ingot (metal work piece of standard size) is produced. This billet is heated in hot extrusion or remains at room temperature and placed into a extrusion press (Extrusion press is like a piston cylinder device in which metal is placed in cylinder and pushed by a piston. The upper portion of cylinder is fitted with die). Now a compressive force is applied to this part by a plunger fitted into the press which pushes the billet towards die. The die is small opening of required cross section. This high compressive force allow the work metal to flow through die and convert into desire shape. Now the extruded part remove from press and is heat treated for better mechanical properties. This is basic working of extrusion process. Types of Extrusion: Extrusion process can be classified into following types. According to the direction of flow of metal Direct Extrusion: In this type of extrusion process, metal is forced to flow in the direction of feed of punch. The punch moves toward die during extrusion. This process required higher force due to higher friction between billet and container. Indirect Extrusion: In this process, metal is flow toward opposite direction of plunger movement. The die is fitted at opposite side of punch movement. In this process, the metal is allowed to flow through annular space between punch and container. Hydrostatic Extrusion: This process uses fluid to apply pressure on billet. In this process, the friction is eliminated because the billet is neither contact with cylinder wall or plunger. There is a fluid between the billet and plunger. The plunger applies force on fluid which further applied on billet. Normally vegetable oils are used as fluid.This process accomplished by leakage problem and uncontrolled speed of extrusion. According to the working temperature Hot Extrusion: If the extrusion process takes place above recrystallization temperature which is about 50-60% of its melting temperature, the process is known as hot extrusion. Advantages: Low force required compare to cold working. Easy to work in hot form. The product is free from stain hardening. Disadvantages: Low surface finish due to scale formation on extruded part. Increase die wear. High maintenance required. Cold Extrusion: If the extrusion process takes place below crystallization temperature or room temperature, the process is known as cold extrusion. Aluminum cans, cylinder, collapsible tubes etc. are example of this process. Advantages: High mechanical properties. High surface finish No oxidation at metal surface. Disadvantages: High force required. Product is accomplished with strain hardening. Application: Extrusion is widely used in production of tubes and hollow pipes. Aluminum extrusion is used in structure work in many industries. This process is used to produce frames, doors, window etc. in automotive industries. Extrusion is widely used to produce plastic objects. Advantages and Disadvantages: Advantages: High extrusion ratio (It is the ratio of billet cross section area to extruded part cross section area). It can easily create complex cross section. This working can be done with both brittle and ductile materials. High mechanical properties can achieved by cold extrusion. Disadvantages: High initial or setup cost. High compressive force required.
17. ## Types of Nozzle in IC Engine

Types of Nozzle in IC Engine : Pintle Nozzle, Single Hole Nozzle, Multihole Nozzle, Pintaux Nozzle Nozzle is that part of an injector through which the liquid fuel is sprayed into the combustion chamber. It is used in Diesel engine in which fuel is drawn separately through injector at end of compression stroke and air is drawn into cylinder in suction stroke. The nozzle used in IC engine should follow following functions. It should automizate fuel. This is a very important function since it is the first phase in obtaining proper mixing of the fuel and air in the combustion chamber. Distribute the fuel in require area within the combustion chamber. To prevent fuel from impinging directly on the walls of combustion chamber or piston. This is necessary because fuel striking the walls decomposes and produces carbon deposits. This causes smoky exhaust as well as increase in fuel consumption. To mix the fuel with air in case of non-turbulent type of combustion chamber. Types of Nozzle in IC Engine: The design of nozzle must be such that the liquid fuel forced through the nozzle will broke up into fine droplets, or atomize, as it passes into the combustion chamber. This is the first phase in obtaining proper mixing of the fuel and air in the combustion chamber. Various types of nozzles are used in IC engines. These types are as follow. The Pintle Nozzle: In this type of nozzle the stem of nozzle valve is extended to from a pin or Pintle which protrudes through the mouth of the nozzle. The size and shape of the Pintle can be varied according to the requirement. It provides a spray operating at low injection pressures of 8-10MPa. The spray cone angle is generally 60 degree. The main advantage of this nozzle is that it avoids weak injection and dribbling. It prevents the carbon deposition on the nozzle hole. The Single Hole Nozzle: In this type of nozzle at the center of the body there is a single hole which is closed by the nozzle valve. The size of the hole is usually of the order of 0.2 mm. Injection pressure is of order of 8-10MPa and spray cone angle is about 15 degree. One of the major disadvantages of this nozzle is that they tends to drible. Besides, their spray angle it too narrow to facilitate good mixing unless higher velocities are used. The Multi Hole Nozzle: This nozzle consists of a number of holes bored in the tip of the nozzle. The number of holes varies from 4 to 18 and the size from 35 to 200 micro meters. The hole angle may be from 20 degree upwards. These nozzles operate at high injection pressure of the order of 18 MPa. Their advantage lies in the ability to distribute the fuel properly even with lower air motion available in open combustion chambers. Pintaux Nozzle: This type of nozzle is a type of Pintle nozzle which has an auxiliary hole drilled in the nozzle body. It injects a small amount of fuel through this additional hole which is called pilot injection in upstream direction slightly before the main injection. The needle valve does not lift fully at low speeds and most of the fuel is injected through the auxiliary hole. The main advantage of this nozzle is better cold starting performance. A major drawback of this nozzle is that its injection characteristics are poorer than the multihole nozzle.
18. ## Difference between Hot Working and Cold Working

They both are the metal forming processes. When plastic deformation of metal is carried out at temperature above the recrystallization temperature the process, the process is known as hot working. If this deformation is done below the recrystallization temperature the process is known as cold working. There are many other differences between these processes which are described as below. Difference between Hot Working and Cold Working: S.No. Cold working Hot working 1 It is done at a temperature below the recrystallization temperature. Hot working is done at a temperature above recrystallization temperature. 2. It is done below recrystallization temperature so it is accomplished by strain hardening. Hardening due to plastic deformation is completely eliminated. 3. Cold working decreases mechanical properties of metal like elongation, reduction of area and impact values. It increases mechanical properties. 4. Crystallization does not take place. Crystallization takes place. 5. Material is not uniform after this working. Material is uniform thought. 6. There is more risk of cracks. There is less risk of cracks. 7. Cold working increases ultimate tensile strength, yield point hardness and fatigue strength but decreases resistance to corrosion. In hot working, ultimate tensile strength, yield point, corrosion resistance are unaffected. 8. Internal and residual stresses are produced. Internal and residual stresses are not produced. 9. Cold working required more energy for plastic deformation. It requires less energy for plastic deformation because at higher temperature metal become more ductile and soft. 10. More stress is required. Less stress required. 11. It does not require pickling because no oxidation of metal takes place. Heavy oxidation occurs during hot working so pickling is required to remove oxide. 12. Embrittlement does not occur in cold working due to no reaction with oxygen at lower temperature. There is chance of embrittlement by oxygen in hot working hence metal working is done at inert atmosphere for reactive metals.

20. ## Cam Terminology and Displacement Diagram

A cam is a mechanical member used to impart desired motion or displacement to a follower by direct contact. It is widely used inautomobile industries to direct opening and closing of inlet and exhaust valves at desire time. Cams are either in rotary or reciprocating or oscillating motion. The driver member in cam follower mechanism is called cam and driven member is called follower. Cam mechanism belong to higher pair mechanism because the cam and follower makes point contact. When we study about cam follower mechanism, some common terminology like prime circle, base circle, pressure angle etc. are used to describe a cam. These are as follow. Cam Terminology and Displacement Diagram: Terminology: Base Circle: Base circle is the smallest circle that can be drawn tangentially to the cam profile. Trace Point: A trace point is a theoretical point on the follower. It’s motion describing the movement of the follower. For example a knife edge follower, the trace point is at the knife edge. Pitch Curve: It is the curve drawn by the trace point assuming that the cam is fixed and the trace point of the follower rotates around the cam. Pressure Angle: It represents the steepness of the cam profile. The angle between the direction of the follower movement and the normal to the pitch curve at any point is called pressure angle. Pitch Point: A pitch point correspond to the point of maximum pressure angle. Its Pitch Circle: A circle drawn with its center at the cam center and pass through the pitch point is known as the pitch circle. Prime Circle: The prime circle is the smallest circle that can be drawn from the center of cam and it is tangential to the pitch curve. Displacement Diagram: Angle of Ascent: It is the angle through which the cam turns during the time the follower rises. Angle of Dwell: Angle of dwell is the angle through which the cam turns while the follower remains stationary at the highest or the lowest point. Angle of Descent: Angle of descent is the angle through which the cam turns while follower returns to the initial position. Angle of Action: This is the total angle moved by the cam during the time between the beginning of rise and the end of return of the follower.
21. ## Difference between Forging vs Casting

Casting and forging are both industrial processes of metal forming and shaping. Different process used in different conditions. The main difference between casting and forging is that the metal is compulsory to heat and convert into liquid stage in casting but in forging metal is converted into desire shape by applying pressure with or without applying heat. If the metal is preheated into forging it does not convert into liquid stage. But before differentiate this both terms; you have to know about what is casting and what is forging What is casting? Casting is a process in which metal is heated until molten stage and pour this liquid metal into a mold or cavity where it is allow solidifying. This process converts the metal into desire shape. It is useful to make complex structure. Most of the industrial structures parts are like lathe machine bed, milling machine bed make big base of other machinery part, IC engine components etc. are made by this process. Advantages of Casting This process can form very large structure which is impossible to form by other process. It can make any complex and unsymmetrical structure. The structure formed by this process has high compressive strength. It can attain wide range of properties. This process can attain high accuracy. What is forging? On the other hand forging is the process of converting metal into desire shape by applying pressure and with or without heat. When the metal is heated before applying pressure the process is called hot forging. In forging metal is heated before below critical temperature or below molten stage. Rolling, pressing, Wire drawing etc. is various types of forging. All sheets, small component, wire etc are formed by this process. Advantages of Forging: It produces tougher product compare to other. The product made by forging has high impact or tensile strength. Tabular form of Difference between Forging vs Casting S. No. Casting Forging 1. The metal is heated until it converts into molten stage. The metal is heated below recrystallization temperature. 2. The product produce by it have high compressive strength compare to forging. It has low compressive strength. 3. It has low fatigue strength. It has high fatigue strength. 4. Imperfection or directional defecates does not improve in casting. Directional defect are refined in forging. 5. It is less reliable or has low strength. It is high reliable. 6. It is costly sometime and has high lead time. It has low lead time and cheap compare to casting. 7. The product has low tensile strength. This produces high tensile strength. 8. It required a secondary finishing operation. It does not require a secondary operation.
22. ## Difference between MIG and TIG Welding

These are two main types of welding. The term MIG is stand for Metal inert Gas welding and TIG is stand for Tungsten Inert Gas welding. These are widely use for joining a verity of shapes and material. MIG WELDING TIG WELDING 1. This welding is known as metal inert gas welding. 1. This is known as tungsten inert gas welding. 2. Metal rod is used as electrode and work piece used as another electrode. 2. Tungsten rod is used as electrode. 3. It is gas shielded metal arc welding. 3. It is gas shielded tungsten arc welding. 4. Continuous feed electrode wire is used which are fast feeding. 4. Welding rods are used which are slow feeding. 5. The welding area is flooded with a gas which will not combine with the metal. 5. Gas is used to protect the welded area form atmosphere. 6. MIG can weld materials such as mild steel, stainless steel and aluminum. A range of material thicknesses can be welded from thin gauge sheet metal right up to heavier structural plates. 6. TIG weld things like kitchen sinks and tool boxes. Pipe welding and other heavier tasks can also be performed, you just need to have a unit that is capable of putting out the amount of power that you need. 7. MIG requires consumable metallic electrode. 7. It used non consumable tungsten electrode 8. Electrode is feeded continuously from a wire reel. 8. It does not require electrode feed. 9. DC with reverse polarity is used. 9. It can use both A.C and D.C. 10. Filler metal is compulsory used. 10. Filler metal may or may not be used. 11. It can weld up to 40 mm thick metal sheet. 11. Metal thickness is limited about 5 mm. 12. MIG is comparatively faster than TIG. 12. TIG is a slow welding process.
23. ## How Many Types of Boilers?

A boiler may be defined as a closed vessel in which steam is produced from water by combustion of fuel. Boiler is used in many industries such as in steam power generation, in sugar industries, in textile industries for sizing and bleaching etc. and in many other chemical industries. Earlier it was mainly used in power generation in steam engine. Boiler is also known as steam generator. The primary requirement of boilers is the water, which must be contained safely and the steam must be safely delivered in desired condition. In a boiler, many parts and fittings of mounted, which are mounted on the boiler for its proper and safe functioning. These are as follow 1. Water level indicator 2. Pressure gauge 3. Safety valves 4. Stop valve 5. Blow of cock 6. Feed check valve 7. Fusible plug Types of boilers: Boiler may be classified in following types. According to the axis of boiler 1. Horizontal boiler: If the axis of boiler is horizontal, it is known as horizontal boiler. Example Babcock and Wilcox boiler 2. Vertical boiler: If the axis of boiler is vertical, it is known as vertical boiler. The main advantages of vertical boiler that it is easy to maintain. Example : Cochran boiler 3. Inclined boiler: If the axis of boiler is inclined, it is known as inclined boiler. According to fire of boiler: 1. Externally fire boiler: If the furnace is outside of the boiler shell, it is known as externally fired boiler. Example Babcock and Wilcox boiler 2. Internally fire boiler: If the furnace is inside the shell, it is known as internally fired boiler. Example Lancashire boiler According to pressure of boiler: 1. High Pressure boiler: If the boiler pressure is above 80 MPa, the boiler is known as high pressure boiler. Example Benson boiler 2. Low pressure boiler: If the boiler pressure is below 80 MPa, the boiler is known as low pressure boiler. Example Cochran boiler According to Circulation of water 1. Forced circulation boiler: If the circulation of water is done by a feed pump, the boiler is known as forced circulation boiler. Example Velox boiler 2. Natural circulation boiler: If the circulation of water is done by natural convection, this is known as natural circulation boiler. Example Lancashire boiler According to circulation of gases: 1. Fire tube boiler 2. Water tube boiler 1. Fire tube boiler: In this types of boiler water flow surrounding the tubes and the hot flue gases flow through the tubes. The heat passes form the tube to surrounding water which is used to heat the surrounding flowing water and convert it into steam. Example Lancashire boiler 2. Water tube boiler: In this boiler, water flow through the tubes which are surrounded by hot flue gases. These flue gases used to heat the water and convert it into steam. Example Lamont Boiler

25. ## Types of Welding

Welding is a process of joining similar and dissimilar metals or other material by application of heat with or without application of pressure and addition of filler material. It is used as permanent fasteners. Welding is essential process of every manufacturing industries. In fact, the future of any new metal may depend on how far it would lend itself to fabrication by welding. The weldability has been defined as the capacity of being welded into inseparable joints having specified properties such as definite weld strength proper structure. The weldability of any metal depends on five major factors. These are melting point, thermal conductivity, thermal expansion, surface condition, and change in microstructure. Types of welding: Basically welding may be classified into three types. 1. Plastic welding: In plastic welding or pressure welding process, the pieces of metal to be joined are heated to a plastic state and then forced together by external pressure. These welding are also known as liquid-solid welding process. This procedure is used in forge welding and resistance welding. 2. Fusion welding: In the fusion welding or no pressure welding process, the material at the joint is heated to a molten state and allowed to solidify. These welding are also known as liquid state welding process. This includes gas welding, arc welding, thermite welding etc. 3. Cold welding: In this welding process, the joints are produced without application of heat, but by applying pressure which results diffusion or inter-surface molecular fusion of the parts to be joined. It is also known as solid state welding process. This process is mainly used for welding nonferrous sheet metal, particularly aluminum and its alloys. This includes ultrasonic welding, friction welding, Explosive welding etc. 4 Main Welding Processes: 1. Arc Welding (Fusion Welding): In this type of welding process, weld metal melted from the edges to be joined and allow to solidifies from the liquid state and usually below the recrystallization temperature without any applied deformation. Arc welding is most extensively employed method of joining metal parts by fusion. In this welding the arc column is generated between an anode, which is the positive pole of 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 such that the current continues to flow through a path of ionized particles called plasma, an electric arc is formed. This ionized gas column acts as a high resistance conductor that enables more ions to flow from the anode to the cathode. Heat is generated as the ions strike the cathode. This heat used as melting of metal to be joined or melting the filler metal which further used as joining material of welding metal. The electrode is either consumable or non-consumable as per welding requirement. The temperature at the center of the arc being 6000 OC to 7000OC 2. Gas Welding: The gas welding is done by burning of combustible gas with air or oxygen in a concentrated flame of high temperature. As with other welding methods, the purpose of the flame is to heat and melt the parent metal and filler rod of a joint. It can weld most common materials 3. Gas Metal arc welding (MIG): This welding is also known as metal inert gas welding. In this type of welding a metal rod is used as one electrode, while the work being welded is used as another electrode. It is a gas shielded metal arc welding which uses the high heat of an electric arc between a continuously fed, consumable electrode wire and the material to be welded. Metal is transferred through protected arc column to the work. In this process the wire is fed continuously from a reel through a gun to constant surface imparts a current upon the wire. In this welding the welding area is flooded with a gas which will not combine with the metal. The rate of flow gas is sufficient to keep the oxygen of the air away from the hot metal surface while welding is being done. 4. Gas Tungsten Arc Welding (TIG): This welding is also known as tungsten inert gas welding is similar to the MIG in that is uses the gases for shielding. This arc welding process uses the intense heat of an electric arc between a no consumable tungsten electrode and the material to be welded. In this process the electrode is not consumable during welding process and gas is used to protect the weld area form atmospheric air.
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