ADVANCE WELDING: Repair and Maintenance Welding Unit 4 Part 2 Notes

Que4.6. Write short note on recovery welding. Answer 1. recovery welding is the simplest form of recovery where the metallic factors are joined together, if cracked broken, with the use of suitable electrode using bow welding. 2. During this process, there’s possibility of veritably high localised temperatures, which could affect in deformation of the factors, therefore the process requires great care while being performed. Que4.7. Define weldability of accoutrements and mention the factors on which weldability depends. Answer Weldability of Accoutrements 1. Weldability is the capacity of a material to be welded under the fabrication conditions assessed into a specific suitably designed structure and to perform satisfactorily in the willed service. Factors Affecting the Weldability Metallurgical comity 1. This implies that the base essence and weld essence can be combined within the degree of dilution encountered in a specific process without the product of any dangerous ingredients or phases. ii. Mechanical parcels 1. The mechanical parcels must meet parcels conditions and normal engineering norms. iii. utility 1. utility is concerned about the capability of the welded structure to work under low and high temperatures and impact loadsetc. Que4.8. Explain the effect of colorful alloying rudiments on weldability. Answer 1. Alloying rudiments increase or drop hardenability of the HAZ. C, Mn, Mo, Cr, V, Ni and Si have topmost effect on the hardenability of sword. 2. Alloying rudiments give grain refinement. Al, V, Ti, Zr and N are the grain pollutants for carbon and low amalgamation brands. 3. Alloying rudiments control ductile to brittle metamorphosis temperature. 4. Alloying rudiments form substitutional blends and strengthen the essence by solid result hardening. 5. Alloying rudiments form interstitial blends to increase mechanical parcels by chassis deformation. 6. Alloying rudiments form carbides, age hardening effects and reduce isolation. 7. Alloying rudiments also give grain refinement. 8. Alloying rudiments give deoxidation of molten essence without loss of primary alloying rudiments. Ti, Zr, Al, Si have affinity for oxygen than iron and therefore act as deoxidizers in carbon and low amalgamation brands. Que4.9. Explain the effect of alloying rudiments( S, P, and Mn) in parent essence on the weld and explain how the weldability of sword can be increased. Answer Effect of Alloying rudiments( S, P and Mn) in Parent Essence on the Weld Effect of Sulphur( S) Sulphur imparts free machining parcels. ii. Effect of Phosphorus( P) Phosphorus improves irradiation stability and creep parcels. iii. Effect of Manganese( Mn) Mn contributes to strength and hardness. Mn also lowers both rigidity and weldability, if present in high chance with high carbon content in sword. Weldability of Steel can be Increased by 1. For low carbon sword, flux shielded essence bow welding is used. Both mild sword and low hydrogen electrodes are employed for this purpose. 2. For medium carbon sword, flux shielded essence bow welding is used and low hydrogen electrodes may be employed to reduce weld cracking. 3. Preheating( between temperatures 150 °C to 260 °C) is done to exclude and reduce the hard and brittle areas after welding, the workpiece should be allowed to cool to room temperature sluggishly by being buried in beach. Post heating of the job( between temperatures 595 °C to 675 °C) is done for 1 hour per 25 mm of section consistence. 4. For high carbon sword, oxy- acetylene welding can be used. Que4.10. Write a short note on carbon fellow. Answer 1. Carbon fellow is an empirical value in weight percent, relating the combined goods of different alloying rudiments used in the timber of carbon brands to an original quantum of carbon. 2. In terms of welding, carbon original governs the hardenability of the parent essence. 3. It’s a standing of weldability related to carbon, manganese, chromium, molybednum, vanadium, nickel and bobby
content. 5. The capability to form hard metallurgical ingredients similar as martensites or any other hard phases is dependent on the carbon fellow and the cooling rate of the sword involved in cooling from the metamorphosis temperature. 6. The advanced the carbon original value, the briskly the cooling rate, the advanced the tendency for hard, brittle phases to form during cooling. Que4.11. Explain the welding of low carbon brands. Answer 1. Low carbon sword is most extensively used for welding in diligence because of its strength, its plasticity under fabricating styles and its fairly low price. 2. Low carbon brands may be welded by any of the generally used welding processes, the choice depending upon section consistence and quality conditions. 3. Plate density above 25 mm need preheat, controlled interpass temperature and postwelding stress relief to avoid cracking and to maintain durability, strength and rigidity. 4. Welding processes employed for welding low carbon brands are as follows Oxy- acetylene welding, ii. Flux shielded essence bow welding, iii. Submerged bow welding, iv. Gas essence bow welding, Gas tungsten bow welding, vi. Tube bow welding, vii. Thermit welding, viii. Resistance welding, ix. Electroslag welding, and Brazing. 5. Flux shielded essence bow welding is generally used for welding low carbon brands. Both mild sword and low hydrogen electrodes are employed for the purpose. 6. Oxy- acetylene welding is also constantly used to weld low carbon brands. 7. The selection of padding rod depends upon the base essence composition. A neutral honey is used for welding. Backhand fashion is preferred and no flux is demanded. Que4.12. Write down colorful process used for welding pristine sword. Explain any bone
. Answer colorful Process Used for Welding Stainless Steel 1. Oxy- acetylene welding, 2. Arc welding, 3. Resistance welding, and 4. Brazing. Oxy- Acetylene Welding 1. For gas welding of pristine sword i. A flange- type joint is stylish for thin wastes. ii. wastes up to 3 mm thick may be butted together. iii. For plates thicker than 3 mm, their edges are scratched to give a vee to gain emulsion entirely to the bottom of the weld. 2. Before welding, the plate shells are gutted with fine beach paper, pristine sword hair, line encounteretc. 3. During welding, arsonist is kept at an angle of 45 ° to the work and the tip of the inner cone of honey is kept within1.5 mm of the molten billabong
to avoid oxidation. 4. The honey is played on the work until the edges melt and mingle with the essence from the padding rod. 5. Welding speed is kept livery. 6. The forehand fashion is preferred on thinner wastes and the cacography fashion is employed when welding thicker wastes. 7. At no time, the padding rod is withdrawn from the honey, as else there is certain to be some oxidation of the metallic driblets. 8. The success of welding depends upon keeping the heat to a minimal and completing the weld in one pass. Que4.13. Explain the welding procedure of cast iron. OR Compactly bandy the welding of cast iron. What kinds of blights are anticipated in similar welding and what are their remedies. Answer Welding of Cast Iron 1. There are different types of cast iron. Then we bandy the welding procedure of argentine cast iron, it contains, 2. The welding of argentine cast iron can be done by the following processes Metal Arc Welding 1. A V- joint with included angle of 60 ° to 90 ° may be formed by dicing or machining. 2. The joint is precisely gutted of all dust, dirt, oil painting, grease and makeup. 3. Electrodes of cast iron, mild sword, austenitic pristine sword may be employed for welding argentine cast iron. 4. The bow is struck by touching the electrode with the job. As the molten pool forms, the welding is carried out in the normal way. 5. In order to minimize the stresses set up in the workpiece, the weld may be laid in the short run and also each be allowed to cool. ii. Brazing 1. Brazing of argentine cast iron is done to repair casting blights where strength and colour match aren’t of primary significance. 2. Brazing of cast iron requires specialpre-cleaning styles to remove graphite from the face of iron because the presence of graphite on the cast iron face would help wetting and adhesion of the brazing amalgamation. 3. It carried out at temperature as low as doable, in order to avoid reduction in the strength of iron. 4. Brazing is generally done with an oxy- acetylene arsonist and a neutral or slightly carburizing honey. 5. Preheating between 205 °C to 427 °C before arsonist or induction brazing may produce better results. blights and Remedies in Welding of Cast Iron Undercut 1. Undercut is a kind of weld disfigurement which forms a groove in the parent essence along the sides of the weld blob. 2. Groove reduces the consistence of the plate and also reduces the strength of the weld. Remedies of Undercut 1. Use proper bow current. 2. Use proper electrode. 3. Weaving should be proper and as per demand. ii. Hot Tear 1. In this welding disfigurement the deposited essence being hot, starts developing crack from the near edge so that after it has been solidified the crack increases. Remedies of Hot Tear 1. elect proper electrode material. 2. Welding current should be optimum as per the demand. 3. Electrode consistence should be optimum and according to the base essence to be welded.

Leave a Comment