Que2.30. Explain principle and working of disunion stir welding with advantages and limitations Answer Friction Stir Welding( FSW) 1. FSW is a solid state joining process and is used for operations where the original essence characteristics must remain unchanged as far as possible. 2. This process is primarily used on aluminium and most frequently a large piece which can not be fluently heat treated post weld to recover temper characteristics. Principle of Operation of Friction Stir Welding 1. In FSW, a spherical, shouldered tool with a penciled inquiry( nib or leg) is rotated and sluggishly plunged into the common line between two pieces of distance or plate material, which are butted together. 2. The corridor have to be clamped strictly onto a backing bar in a manner that prevents a butting common face from being forced piecemeal. 3. Length of nib or pin is slightly lower than the weld depth needed and tool shoulder should be in intimate contact with the work face, nib is also moved against the work or vice versa. Working of Friction Stir Welding 1. Frictional heat is generated between the wear and tear resistant welding tool shoulder and leg and the material of the workpiece. 2. This heat long with the heat generated by the mechanical mixing process and adiabatic heat within the point allowing the covering of the tool along the weldline in a plasticised tubular shaft of essence as the leg is moved profile, forces plasticised material to the reverse of the leg while applying a substantial forging force to consolidate the weld essence. 6. The welding of the material is eased by severe plastic distortion in the solid state, involving dynamic recrystallization of the base material. Advantages of Friction Stir Welding 1. Good mechanical parcels. 2. Advanced safety due to the absence of poisonous smothers or the spatter of molten essence. 3. No need of consumables electrode. 4. Aluminium and no padding or shielding gas is needed for aluminium. 5. fluently automated on simple milling machines lower setup costs and less training. Limitations of the Process 1. Exit hole left when tool is withdrawn. 2. Large down forces needed with heavy duty setting necessary to hold the plates together. 3. Less flexible than homemade bow process, difficulties with consistence variation and non welding fashion. Although these may be neutralize if smaller welding passes are needed. Que2.31. Write short note on aquatic welding. Answer Underwater Welding 1. Aquatic welding is an important tool for aquatic fabrication workshop. 2. In 1946, special leakproof electrodes were developed in Holland by Vander Willingen. 3. In recent times the number of coastal structures including oil painting drilling equipages, channels, platforms are being installed significantly. 4. Some of these structures will witness failures of its rudiments during normal operation and during unpredicted circumstances like storms collisions. 5. Any form system will bear the use of aquatic welding. 6. Problem with aquatic welding is that deep water work is noway easy, because diving operations are dependent on drift and rainfall and the difficulties arising from the colorful positions in which welding has to be done, also add to the problem encountered. 7. An essential demand for aquatic welding is the complete sequestration of the welding circuit. Indeed the electrode coatings are defended by a subcaste of wax, shield or cellulose. Que2.32. Explain type of aquatic welding and their working mechanisms. Answer Types of aquatic welding are as follows Wet Welding 1. In this welding process, the work to be welded is connected to one side of an electric circuit, and a essence electrode to the other side. 2. These two corridor of the circuit are brought together, and also separated slightly. 3. The electric current jumps the gap and causes a sustained spark, which melts the bare essence, forming a weld pool. 4. At the same time, the tip of electrode melts, and essence driblets are projected into the weld pool. 5. During this operation, the flux covering the electrode melts to give a shielding gas, which is used to stabilize the column and guard the transfer essence. 6. The bow burns in a depression formed inside the flux covering which is designed to burn slower than the essence barrel of the electrode. ii. Dry Welding 1. This is carried out in a chamber, sealed around the structure to be welded. 2. The chamber is filled with a gas generally helium( He) containing0.5 bar of oxygen at the prevailing pressure. 3. The niche is sealed onto the channel and filled with a permeable admixture of helium and oxygen, at or slightly above the ambient pressure at which the welding take place. 4. This system produces high quality weld joints that meetX-ray and law conditions. 5. The gas tungsten bow welding process is employed for this process. 6. The area under the bottom of the niche is open to water. 7. therefore welding is done in the dry but at the hydrostatic pressure of the ocean water girding the niche. Que2.33. What do you understand by narrow gap welding? Also write down its advantages and disadvantages. Answer Narrow Gap Welding 1. Narrow gap welding is used to weld thick sections more economically. 2. This welding procedure uses common medications with small included angles generally in the range 2 ° – 20 ° which bear lower weld essence and lower welding time to fill. 3. It have been applied when welding using submerged bow welding, gas shielded essence bow welding and tungsten inert gas welding. 4. It requires technical outfit because of the limited availability to the root of the medication. Advantages of Narrow Gap Welding 1. The process offers better frugality. 2. There’s low angular deformation. 3. lower time consuming process. Disadvantages of Narrow Gap Welding 1. The weld is more prone to blights. 2. It’s delicate to remove any blights. Que2.34. Explain in brief about tandem or binary line welding. Answer 1. Tandem welding involves high performance MIG/ diurnal welding using two line electrodes. 2. It’s only used in completely automated( robot) operations and is ideal for adding welding speed as well as deposit rate. 3. During tandem welding, two line electrodes are melted at the same time. These are routed through two electrically insulated contact tips, i.e., the capabilities are separate. 4. As a result, the bends can be controlled singly and despite differing products can be precisely coordinated. 5. It can be performed in both directions performing in high degree of inflexibility. 6. Tandem welding can be used to weld both thin and thick sections. 7. Tandem welding is used in construction ministry, unsalable transport vehicles, automotive diligence,etc. Que2.35. Describe in detail about magnetically impelled bow butt MIAB) welding. Answer 1. Magnetically impelled bow butt( MIAB) welding is a solid state welding process involving gyration of bow around the tube to prop the invariant heating of faying shells. 2. MIAB welding process is a single shot process and can readily be automated as no homemade skill is involved, and is veritably fast with a welding time of 22 sec for a pipe consistence of 6 mm. 3. It produces a solid state cling which is conducive to excellent mechanical parcels. It also opens up to the possibility of different essence joints. 4. MIAB welding requires no part gyration unlike disunion welding, and hence is important simpler and less precious. 5. Other implicit benefits of MIAB welding include less internal flash, shorter weld time, less metal loss, livery heating and reduced machine conservation. 6. MIAB welding process is characterized in six stages furnishing bow inauguration, morning of bow gyration, bow temporary gyration, bow stable gyration with each other bow instable gyration and tube disturbing. 7. MIAB welding process is extensively used in power, defence, oil painting and gas sectors and is seen as an effective relief to disunion, flash, resistance and butt welding. Que2.36. What do you understand by welding robotization? Answer 1. Welding robotization is a specific type of manufacturing gospel and therefore, represents one of the types of manufacturing robotization. 2. Since its thing has always been to replace conduct of a homemade welder with those of a machine, its description can be drawn through an analysis of conduct demanded to effectively perform the welding operations. 3. Welding operations, when performed manually, are generally associated with three introductory functions of the welder Physical function requires the welder’s muscular energy or any kind of power to perform the operation. ii. Programming function is associated with development of the welder’s action instructions. iii. Control function is associated with supervision of the established program of a welder’s conduct that are demanded under abnormal conditions( variations in common figure, welding settings, position of the welding head,etc.). 4. When in addition to the physical function, one or both intelligent functions are transferred to a machine, the man- machine system and the group of operations served by this system may be called an automatic welding system and automatic welding operations. 5. The process, or the result of relief of the operations associated with welder’s intelligent sweats by that grounded on the intelligent conduct of a machine, is called welding robotization. Que2.37. What are the operations of robot in welding? Also give its advantages and disadvantages. Answer Applications of Robot in Welding 1. The typical bow welding operation for a robot is one in which the amounts of product are medium or high. 2. A robot cell can be justified which consists of a welding robot and a part holder or part manipulator. 3. The part holder is used to institution the factors and place them for welding. 4. A part manipulator provides an fresh capability in the form of 1 or 2 degrees of freedom to position and orient the factors relative to the robot. 5. The robot is equipped with a welding rod or line feed system, and the needed power source to give the electric current for the operation. 6. The workcell regulator is used to coordinate the robot stir, the welding current, the line feed, the part manipulator and any other conditioning in the cell. Advantages of Robot in Welding 1. Advanced productivity. 2. Advanced safety and quality of work life. 3. Greater quality of product. 4. Process vindication. Disadvantages of Robot in Welding 1. There are significant specialized and profitable problems encountered in applying robot to bow welding. 2. Arc welding is frequently performed in confined areas that are delicate to access, similar as the inside of tanks, pressure vessels, and boat shells. 3. The presence of variations in the factors that are to be welded. 4. rather of being straight and regular, the edges are generally irregular.