Que2.12. Explain in brief about electroslag welding? Also mention advantages and disadvantages of electroslag welding. Answer Electroslag Welding Electroslag welding is a type of bow welding wherein the coalescence is produced by molten sediment which melts the padding essence and the face of the work to be welded, electroslag welding is relatively analogous to perpendicular submerged bow welding. In electroslag welding process a grainy flux is placed in the gap between the plate being welded and as the current is turned on, welding takes place in a watercooled bobby
shoes that bridge the gap of the joint as the flux melts, a sediment mask from25.4 to38.1 mm consistence is formed, high resistance of the sediment causes utmost of the heating for the remainder of the weld therefore electroslag welding is a progressive process of melting and solidification from the bottom to overhead. The maximum consistence that can be weld by this process is upto 100 mm. Molten essence and sediment are retained in the joint by means of bobby
shoes that automatically move overhead as the weld progresses by means of a temperature sensitive medium. Advantages of Electroslag Welding common medication is relatively simple as compared to other welding processes. veritably high consistence plate can be veritably fluently welded in a single pass more economically. It gives extremely high deposit rate. deformation and thermal stresses are in veritably low chance. Flux consumption is veritably low. Disadvantages of Electroslag Welding Process is only limited to perpendicular position. Electroslag welding tends to produce rather large grain size. Complex shape joint can not be welded by this process. further chances of hot cracking and notch perceptivity in the heat affected zone. Que2.13. Explain the resistance welding and its types. Also write advantages and disadvantages of it. Answer Resistance Welding Resistance welding is a group of welding processes wherein coalescence is produced by the heat attained from resistance of the work to the inflow of electric current in a circuit of which the work is a part and by the operations of pressure. No padding essence is demanded. Resistance welding is also one of the types of pressure welding process during which the pressure is applied. Basic working principle of resistance welding depends upon. Types of Resistance Welding Spot welding, Confluence welding, protuberance welding, Percussion welding, and Flash butt welding. Advantages of Resistance Welding No padding rod or electrode is needed. High rate of product. Semi-skilled driver can perform welding veritably fluently. No part deformation. No need of edge medication. Metallurgy of workpiece isn’t so important change. Disadvantages of Resistance Welding All types of essence can not be welded. Complex shapes and bigger jobs can not be joined. Welding joint isn’t so strong. original cost of outfit is high. Applications of Resistance Welding This is used for joining wastes, tubes, aircraft and machine corridor, energy tank, line fabrics, grills and holders. Que2.14. Write a short note on the following types of resistance welding Spot welding, ii. Confluence welding, and iii. protuberance welding. Answer Spot Welding In resistance spot welding, the lapping essence corridor are held between two bar type essence electrodes which apply pressure, while an electric current is passed through them. When the current is switched on and applied for as destined number of cycles, the lapped pieces of essence are hotted
in a confined area. The generated heat melts the face subcaste of essence in the central, more largely heated, area of contact with the electrodes, and the conterminous layers of essence are softened to a plastic state. also the current is switched off and the electrodes are pressed and the pressure is released only after weld nugget has solidified. ii. Confluence Welding To gain a series of spot welds along a line by this system, an interrupted work movement will be necessary. The same result can be achieved much more accessibly and fleetly in confluence welding where the electrodes are in the form of rotating slice electrodes, with the work being welded moving continuously by the electrodes. Breakers may vary in periphery from 40 to 350 mm. Welding currents range from 2000 to 5000 A, while the force applied to the breakers may be as high as 5 to 6 kN and welding speed is from0.5 to m/min. In utmost cases of confluence welding, a sluice of water is directed over the slice electrodes except the joint interface. In this welding the current is concentrated at the spots to be welded, when small protrusions are embossed on one of the wastes. When the current is applied, the protrusions soften and are pushed back in place by the electrode pressure as the weld nuggets form. Also, because larger periphery electrodes can be used with a lesser heat capacity, the need for water cooling is frequently excluded. The protrusions tend to localize the heat, permitting thicker accoutrements to be welded performing in a stronger weld structure. This is used in machine assiduity for joining nuts, bolts and superstuds to sword plates in auto bodies. Que2.15. Explain the principle and operation of disunion welding process. Also give its advantages and disadvantages. Answer Principle and Operation of Friction Welding disunion welding is defined as, a solid state welding process wherein coalescence is produced by heat attained from mechanically convinced sliding stir between the rubbing shells. The corridor are held together under pressure. One part is rotated at fairly high speed and under pressure against the alternate part which is held stationary. The frictional work at the reaching shells is converted into heat. The reaching shells are therefore hotted
to a high temperature below the melting temperature. At this point, the relative stir between the two is stopped. The weld is also completed due to the pressure which still continues or fresh pressure may be necessary to produce a solid state weld. This system is most suitable for indirect corridor, i.e., butt welding of round bars or tubes. Advantages of Friction Welding Low original capital cost and power demand. Annealing of weld zone isn’t necessary. veritably little loss of material through rejections. The process welds the whole face of contact. No flux, gas padding essence or sediment present to beget fault in weld, no bank too. Heat affected zone is veritably narrow. Disadvantages
