Que4.14. What are the welding characteristics of aluminium and its blends? Mention colorful styles for welding aluminium and its blends. Answer Welding Characteristics of Aluminium and its blends 1. The first and the foremost consideration is the effect of the thin film of oxide which is chemically or mechanically removed before welding. 2. Aluminium being a veritably good captain of heat, dissipates heat at a veritably fast rate from the joint being welded. This must be compensated by using bigger snoot size. 3. Aluminium has got high measure of direct expansion. 4. Aluminium is weak when hot and therefore redundant care is needed when welding thinner section which may buckle. 5. Aluminium doesn’t show any colour change on heating and without experience it may be delicate to judge when the essence begins to melts. colorful styles for Welding Aluminium and its blends 1. Oxy- gas welding, 2. MIG or TIG welding, 3. Resistance welding, 4. Metallic bow welding, 5. Solid state welding, and 6. infinitesimal- hydrogen welding. Que4.15. Explain in detail aluminium welding by double driver system. Answer 1. Aluminium welding by double driver system as shown inFig.4.15.1. 2. The oxide of aluminium( alumina Al2O3) which is always present as a face film and which is formed when aluminium is hotted
, has a veritably high melting point, much advanced than that of aluminum. 3. still, If it isn’t removed it would come distributed throughout the weld. performing in weakness and fineness. 4. The work should be gutted of grease and brushed with a line brushsheets below 20 hand can be turned up at right angles and the weld made without a padding rod. 5. Aluminium, when near its melting point is extremely weak, and important trouble can be avoided by seeing that no collapsing can do during the welding operation. 6. The honey is acclimated to have a veritably slight excess of acetylene and also acclimated by neutral and rod of pure aluminium or 5 silicon- aluminium amalgamation should be little thicker also the section to be welded. 7. The double- driver system is used on wastes above 6 mm consistence, the angle of the blow pipes being 50 – 60 ° and the rods 70 – 80 °. 8. This system gives a great increase in welding speed. Que4.16. Write short note on metallic bow welding of aluminium. Answer 1. In the metallic bow welding of aluminium there remains a tendency to illness in the welds. 2. The bow between the electrode and the job is struck by scratching action. 3. Electrode has to be scratched veritably hard against the job to strike the bow because of the sequestration swung by the flux coating on the electrode and the oxide film on the essence. 4. A short bow is maintained, the electrode is held at right angle to the work, the electrode coating nearly touches the molten pool and no weaving is done. 5. The bow is so directed that both edges of the joint to be welded are duly and slightly hotted
. 6. The rate of welding should be invariant. As the essence warms up, the speed of welding must be increased. Que4.17. bandy the colorful ways for welding the different accoutrements . Answer colorful ways for welding the different accoutrements are as follows form & conservation Welding 4 – 16 H( ME- Sem- 5) Resistance Welding 1. It’s frequently easier to make satisfactory joints between different essence by resistance welding than by bow welding, since the problem of liquefying or provision of an inert atmosphere doesn’t arise and the ways available frequently minimize the peril of the conformation of brittle intermetallic composites within the joint. 2. Bobby and aluminium, for illustration, form a series of brittle phases when melted together, but flash- butt welding of the two essence is extensively rehearsed since these phases are forced out of the joint when the worried force is applied. 3. Spot and protuberance welding both are used to weld different essence. ii. Solid- State Welding 1. Solid- state welding processes include Pressure welding with or without controlled atmospheres. ii. Ultrasonic welding. iii. disunion welding. iv. prolixity cling. 2. It’s necessary that the shells should be clean and be in intimate contact. iii. Brazing 1. Brazing is of important significance in joining different essence because in good practice, alloying between the different essence can not do, and no infelicitous phases can be formed. 2. Accoutrements susceptible to intergranular penetration should typically be annealed before brazing. 3. The zinc bearing tableware solders and bobby
– zinc blends may be used for joining bobby
, bobby
blends, brands of all types, heat- defying blends and nickel blends. Unit- 5 Que5.1. Describe the colorful types of welded joints used in weld design. Answer colorful types of welded joints used in weld design are as follows Butt Joint 1. Forecourt butt joints( with or without gap) are recommended for lower plate density( upto4.8 mm) and important lower lading as compared to single V, U, J or bevel joints. 2. Double joints are preferred over single joints for bigger plate density. 3. Out of colorful joints, V common finds much more expansive use and operations. 4. Bevel joints are preferred for plates with density ranging from 10 mm to 35 mm and subordinated to medium lading. 5. U joints are preferred over V joints when it’s needed to make high quality joints in certain pressure vessel having plate consistence ranging from 10 mm to 20 mm. 6. J joints are recommended for normal lading in some pressure vessels. 7. Among the double joints, double V joint is employed under utmost severe lading conditions. ii. stage common 1. Single fillet and double fillet joints are used on all density. 2. Double fillet joint is better as compared to single fillet joint when common is subordinated to severe lading. 3. Single fillet joints aren’t recommended on plates under bending, fatigue or impact lading conditions. 4. Plug weld is employed to conduct added strength to the structure. This draw weld joint is used where bottom or alternate plate can not be penetrated fluently. iii. T Joint 1. Single fillet T joint is preferred for lower plate density when subordinated to low or no bending cargo conditions. 2. Double T joint is recommended for utmost severe lading conditions. 3. In T joint cost of edge medication increases and electrode consumption diminishments. iv. Corner Joint 1. For lower consistence plates and not subordinated to severe lading, close and half open corner joints. 2. Full open corner joint can be used on plates of all density under severe cargo conditions. 3. The cargo bearing capacity increases when the joint is welded from both sides. Edge Joint 1. Two pieces of essence are lapped, with their edges in line and the pieces are joined by welding the two edges together. 2. Fillet welds( i.e., corner joint, T joint, stage jointetc.) are the cheapest type of welds to make, as no edge medication is needed and setting up is simple. Que5.3. Explain the welding symbol with an illustration. Answer Welding Symbols 1. Welding symbols give the means of placing on delineations, the information concerning the type, size, position,etc., of the welds in welded joints. 2. The introductory symbols used to represent colorful types of welds. Different Welding Symbols Fillet Welds 1. Fillet weld symbol is used to make stage joints, corner joints, and T- joints. 2. The fillet weld is roughly triangular in sampling. ii. Groove or Butt Welds 1. The variety of butt weld symbol depends primarily on the figure of the corridor to be joined and the medication of their edges. 2. Some butt weld symbols are V- butt, square butt,U-butt, Bevel butt, Jbutt iii. Plug Welds 1. Plug welds symbols are used in joining the lapping members, one of which has holes in it. 2. still, the depth to If the hole isn’t to be fully filled with weld essence. which it’s to be filled is given within the weld symbol. 3. Plug welds are generally used with other welds in the rails. iv. Stud Welds 1. Stud weld symbol is used in electric bow process that fleetly joins a fastener to a base essence or substrate. 2. It’s a presto, dependable and accurate system of welding a essence fastener to another essence object. niche Welds 1. niche weld symbol contains analogous information as draw weld symbol except that plug welds don’t have a length element. 2. Size of a draw weld is its periphery while the size of a niche is its range. vi. Seam Welds 1. Seam weld symbol indicates a weld that takes place between the faying shells of a stage joint that may be composed of two or further lapped pieces. 2. It’s used in resistance welding. vii. Edge Welds 1. This symbol is used where the edges of two wastes or plates are conterminous and are in roughly resemblant aeroplanes
at the point of welding. Welds 1. This symbol is used in the process of protuberance welding. 2. protuberance welds must be dimensioned by strength. ix. Backing Strip Welds 1. The symbol is used to signify the welding of tanks. 2. It’s stationed for root runs with single V as well as double V configurations. Spot Welds 1. The symbol is used specifically in resistance spot welding. 2. The process uses two shaped bobby
amalgamation electrodes to concentrate welding current into a small spot and to damp the wastes together.
