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Heat treatment Assignment PDF

   

Added on  2021-06-16

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TASK 1Heat treatment is an operation which is costly and time-consuming. It can affect the welded joint,its corrosion resistance and the level of residual stress. Without heat treatment method, there are no means of ensuring that the metal manufactured are of high quality and durable.The heating and cooling rate of the metal greatly determine the quality of the metal and this takes place by decreasing the metal temperature to its initial level. The thicker the metal, the more prone the metal will be to falling prey to residual stresses. This isbecause welding together of two different materials allows their assemblies to possess the capacity of changing the structure of the base metal. Introduction of hydrogen during the process of welding, causes the metal to become prone to cracking and rusting while the shattering and corrosion increase in case the welded region is tougher than the rest of the steel. Task 2Methods of manufacturing crankshaftCrankshaft material needs to be machined, heat treated and shaped in order to possess suitable strength, stiffness, hardness and high fatigue strength. The manufacturing of crankshaft is done from steel either by casting or forging[CITATION Ste \p 324 \l 1033].a)Forging method Forging is a manufacturing process involving the shaping of metal by applying localized compressive forces and they are mostly grouped based on temperature at which they operate. The forging of materials into a useful shape is done by pressing or hammering and most

operations involving forging is done in a hot situation though certain materials are cold forged[CITATION Kar13 \p 109 \l 1033]. The forging machines have the ability to make machines between the size from the bolt to the rotor of the turbine. This process simply involves deformation of plastic substantial between two dies in order to achieve the desired configurations. The process of forging is done as open or closed die forging depending on the complexity.The compression of material repeatedly and manipulation of its shape manually is done in open die forging while in closed die forging, the workpiece is squeezed between the two shaped and closed dies in order to obtain the desired configurations. The die cavity gets completely filled during squeezing thus making extra materials to find their way out around the periphery of the dying flash. Both the close and open die forging processes are carried out in cold as well as a hot state.There are two popular methods in closed die forging, namely, drop forging and press forging. In press forging, the mechanical or hydraulic press is used in squeezing the metal slowly and production of components is done in a single closing of die thus better dimensional accuracy compared to drop forging. The forged articles got the outstanding grain structures and the best combination of mechanical properties. Advantages of forgingA piece produced by forging is usually stronger compared to the machined part.Forging targets a lower total cost when compared to the fabrication or casting.Improved microstructure.Continuous grain flow.

Better fatigue resistance. Disadvantages of ForgingHigh cost and high residual stress produced.The cost of making dies makes the forging process to be expensive, so long production runs are normally necessary for reduction of the cost.Forging involves high residual stresses which are often released when they are machined and cause warping when heavy cuts are taken b)Casting methodThe process of casting simply involves pouring of molten metal for producing the desired product. The heating of metal is firstly done at a required temperature then poured into the mold. After knockout finishing is done by machining, the crankshaft made of casting has the lowest strength and it tends to be brittle so that it can be strengthened by some post process heat treatment and surface treatment process. The procedure for casting process includes; Lobe hardening, Machining, Heating, Melting, Pouring Molding, Knockout. Advantages of the casting process In this particular method, the cost of material in the crankshaft and machining are minimized since the crankshaft can be manufactured almost to the essential size and shape including the counterweights.Cast crankshaft can handle loads from all the directions as the metal grain structure is uniform and random throughout.

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