Que4.1. What’s hardfacing? What are the objects and principle of operation of hardfacing? citation advantages and operations of hardfacing. Answer Hardfacing 1. In hardfacing, essence is deposited over another face to increase the hardness of the face, and to make the face of material resistant to bruise, complication, impact, corrosion,etc. 2. One of the most important operations of hardfacing is bruise resistance. 3. In general purpose three layers of hardfacing blends are deposited as effectiveness of the hardfacing reduces inordinate dilution. objects of Hardfacing 1. To extend the service life of critical corridor and assemblies in machines and mechanisms by depositing on them similar essence or blends that will conduct to them resistance to wear or bruise, erosion, heat, impact, corrosion, cavitation, forging, and indentation. 2. To rebuild a worn or scratching out inaptly cast part. 3. To repair a element. Principle of Operation of Hardfacing 1. Determine the exact composition of the base essence because it influences the success and quality of the surfacing system. 2. Determine the type and degree of wear and tear of the base essence. 3. Determine the welding position of the job. 4. Estimate the area that needs to be hardfaced. 5. elect an applicable hardfacing amalgamation. 6. elect an applicable hardfacing system. 7. Prepare the face to be hardfaced. 8. Apply the hardfacing amalgamation on the base essence. 9. conduct proper face finish to the hardfaced base essence element. Advantages 1. This increases the service life of the product. 2. This imparts the erosion resistance. 3. The cost of this process is less as compared to other processes. 4. lower professed worker is needed. Applications of Hardfacing 1. This is considerably used in construction accoutrements including bulldozer blades, scraper blades, cloth diligence accoutrements and machine stopcock facing. Que4.2. What do you mean by cladding? Explain principle of operation of cladding. Answer Cladding 1. Cladding is the covering of one material with another. In metallurgy, cladding is the relating together of different essence. 2. It’s distinct from welding or clinging as a system to fasten the essence together. 3. Regarding optic fibre in telecommunication, cladding is one or further layers of material of lower refractive indicator in intimate contact with a core material of advanced refractive indicator. 4. Cladding is frequently achieved by banishing two essence through a bones or pressing wastes together under high pressure. 5. Cladding has been furnishing high technological coating for a variety of end druggies to enhance functional performance whether it’s to be medical, artificial or automotive. 6. Other diligence use essence cladding to enhance their product performance. This is used To form new corridor, ii. To apply a harder face onto a part, and iii. To resurface the worn or damaged corridor. 7. This is used in product of vessels for chemical, paper shop, petroleum refining and nuclear power factory. Principle of Operation of Cladding 1. Cladding is generally performed by attaching plates of fairly thick essence together similar as by welding and also rolling them down together. 2. The centre core and plating essence retain their proportions as the cross section is reduced. 3. In hot extrusion process, lubricants should be used between the billet, die and vessel, not only to reduce the work cargo but also to keep the inflow laminar. As a result, the external subcaste is also a case of cladding. 4. The temperature range of the billet during the hot extrusion of brands is 1200-1500 °C. The bones must be kept at a lower temperature around 200 °C to avoid inordinate wear and tear rate. 5. Glass fibres are typically used as lubricants since the density of glass is sensitive to temperature. therefore, the density is high at the bones face, furnishing a good protection to die wear and tear and easing the conformation of a glass skin on the product. 6. At the same time, the work cargo is reduced since the density of glass is much lower at the billet- vessel interface. Que4.3. Explain the term essence surfacing. What are the colorful styles of depositing essence? Answer Metal Surfacing 1. Metal surfacing is a deposit process. In this process essence is deposited over another essence to ameliorate the wear and tear resistance parcels of essence like resistance to bruise, erosion, disunion or for achieving dimensional control as well as metallurgical demand. 2. Common processes used for surfacing are emulsion welding process similar as bow welding, oxy- acetylene welding and thermal spraying. 3. This process is extensively used for all outfit especially in chemical diligence to increase the life of accoutrements against wear and tear and chemical action. 4. Since the bond between the base essence and the deposited essence is purely mechanical, it’s essential that the face of the base essence should be set duly so that a good mechanical interlocking between the scattered essence and base essence can be attained. 5. The first step in surfacing is to clean the base essence face by removing all foreign substances similar as oxides, oil painting, water,etc. 6. Oxide and other coatings may be removed by using mechanical styles similar as machining, grinding, grinding,etc. 7. Grease and oil painting can be chemically removed from the base essence face. 8. The coming step is to scuff the base essence by forming keys or openings on it so that the scattered essence penetrates in them thereby performing in a cling or conciliating action. colorful styles of Depositing Essence 1. Cladding, 2. Hardfacing, 3. make up, and 4. Buttering. Que4.4. Explain in detail the advantage of hardfacing with oxyacetylene arsonist. Answer 1. Oxy- acetylene welding process can be used for surfacing purpose with the adjunct of movable and low cost outfit. 2. In this surfacing process heating and cooling rates for parent essence are veritably slow which leads to veritably little dilution performing in smooth, precise and extremely high quality surfacing deposits. 3. Groove, narrow gap and recesses can be fluently filled and veritably thin layers may be easily applied. 4. Preheating and slow cooling nature of oxy- acetylene surfacing system tends to minimized cracking indeed with largely wear resistance but brittle over types of welding honey and size of tip. 5. During surfacing no flux is demanded, a typical operation of the process is the deposit of a low melting point high carbon padding essence. 6. This process also can be done by powdered material; in this case welding arsonist is fitted with hopper( a greasepaint feeding device). 7. Oxy- acetylene surfacing process can be done in asemi-automatic manner where a large number of identical corridor, which can be arranged in methodical manner are present. 8. The process can be fluently employed in the field and veritably thin layers of hardfacing amalgamation can be applied. Que4.5. State the principle and working of metallizing process. Also write down its advantages, disadvantages and operations. Answer Principle of Metallizing Process 1. The material to be scattered is taken in greasepaint or line form and fed into the oxy- acetylene honey. There it melts by the heat of the neutral honey, gets comminuted and blown by a sluice of compressed air onto the base essence face where it spreads around and interlocks with protrusions bedded in recesses, and freezes snappily upon contact with the base essence face. 2. Separate patches lap and intertwine with one another to form a coherent structure. 3. The scattered material is generally applied in layers lower than mm thick. Working of Metallizing Process 1. This consists of a line type spray gun which resembles an oxy- energy gas arsonist with a hole for the line through the centre of its tip. 2. The gun also has an arrangement to drive a brace of knurled rolls to feed the line into the honey, for this line roll and straighteners are used. 3. An air cap encloses the tip of the gun and directs a blast of compressed air to pick up the molten essence, and design it, completely comminuted, onto the base essence. 4. A dry compressed air forms an air envelope around the outside of the honey and the liquid essence atomizes the molten line essence that has been melted by oxy- acetylene honey and cools the substrate therefore maintaining its temperature below 205 °C. 5. Compressed air also accelerates the molten essence patches on its path to the base essence and therefore deposits them there. Advantages of Metallizing 1. This is roughly 70 lower expensive than honey spraying. 2. No combustion feasts are needed therefore barring all problems and troubles associated with these feasts. 3. This can be intruded and proceeded at any time by simply engaging and releasing the line feed medium. 4. This requires lower face medication than honey spraying. Disadvantages of Metallizing 1. The bow scattering haste is lower than that of honey spraying. 2. Coatings don’t repel high temperatures. 3. Acceptable resistance to wear can be achieved, but the performance can not be compared to a face erected- up by welding. 4. The process creates smothers, dust and odours around the work. Applications of Metallizing 1. This is used in product of movable water tanks, islands, cinches and levee gates, oil painting platforms, power transmission polesetc.
