Engineering 

Heat Treatment of Tools

General purpose tools like chisel, hammer, file, punch, lathe tools etc. are manufactured by forging. These tools are normalized immediately after forging to restore their original structure and to relieve stresses and strains set up while forging. Hardening is carried out to induce hardness at the working end and simultaneously tempering is carried out to make the body tough to absorb shock while working. Hence heat treatment has got unique importance in the field of production industry as it helps to induce desired qualities which enable the tools to serve…

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Heat Treatment of Non – Ferrous Metal

Generally annealing is carried out on non-ferrous metals. Annealing makes the metal soft. This property enables the worker to work upon the metal easily, and also prevents the metal to crack or fracture while being hammered, forged or rolled. Copper Copper tends to become hard and brittle, when hammered or cold worked. It can be softened by annealing. All plates, rods, tubes etc of copper are thoroughly annealed before use. Annealing is done by heating to a dull red colour (650°C), keeping the pieces at this temperature for a few…

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Iron-Carbon Equilibrium Diagram

Alloys of the Iron carbon system are of the most vital importance to the modern industry due to their extensive, versatile applications. The Iron carbon system provides the most prominent example of heat treatment and property alteration based on the transformation from one form to other on application of heat and eutectoid decomposition. Because of its outstanding importance, the heat treatment of the iron-carbon system has been studied in more details than most alloy system. Types of steels and cast iron depend upon the percentage of carbon present in the…

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Purpose and Sequence of Case Hardening

Steel components are used in many applications that require a hard and strong surface to resist wear and abrasion combined with a tough core to withstand shock and fatigue. This condition can be obtained by an alteration in the composition of the surface layer of a steel component followed by the application of a suitable “heat treatment. The surface region in which the properties and composition have been altered is known as the case, and the production of a hard surface is known as case hardening. In this process, the…

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Methods of Case Hardening

Various types of surface hardening or case hardening processes are. (a)       Carburising (b)       Cyaniding (c)        Nitriding Carburising The formation of a high carbon case is carried out by heating the steel in contact with a carbonaceous material. Carbon diffuses on to the surface layers of the metal, and the case is subsequently hardened by a suitable heat treatment. According to the nature of the carbonaceous material, three processes are recognized. (a)       Pack (solid) carburizing. (b)       Gas carburizing. (c)        Liquid carburising. Pack Carburising.  The steel components are packed in a…

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21 Useful Key Terms of Heat Treatment

Heat treatment is a process applied to metals to achieve certain desired properties. It is carried out by heating to a definite temperature, soaking for a specific period and cooling the metal at a prescribed rate as well as in a prescribed media. Terms pertaining to heat treatment are defined below. Key Terms With Their Definition Eutectic.The word Eutectic is used to indicate the lowest possible freezing or melting point of any combination of two metals or elements. It corresponds to a definite proportion of two substances and has a…

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Soft Soldering and Its Glossary of Terms

Soft soldering is the process of joining metal parts by heating and running a low-melting point alloy between the two surfaces being joined. As cooling takes place, the alloy solidifies and results in a secure joint.  For most purposes, the low- melting point solder alloy is a composition of lead and tin.  Solder melts at a temperature less than 3000C, which is far below the melting temperature of the metal being joined and produces a low strength joint. Soft soldering is used extensively in sheet metal work for joining parts…

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Composition and Types Soft Solders

The solders generally used in industry are alloys of tin, lead and zinc. Tin-lead solders are used to join most of the metals as they have good corrosion resistance to most of the metals. Sometimes silver, cadmium, antimony and bismuth are also added to solders. It is essential that solders must have a lower melting point than the parent metals. The melting point of a solder should be as near as possible to the parent metal to be joined so that a more tenacious joint is affected. Composition of Soft Solder…

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Flux Used in Soft Soldering

The operation of brazing, soldering and welding has brought out the use of fluxes in service. Flux is a chemical substance, which is made for cleaning the surface of the job and preventing oxidation in operations, such as welding, soldering and brazing. It is rather difficult to have satisfactorily brazed or soldered joints without the use of fluxes. Therefore it is very essential to use flux in soldering, brazing and welding. Soldering flux may be defined as a substance (solid or liquid) applied to a metal to make solder flow…

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Types of Soldering Iron

In most cases of soft soldering process, direct application of heat is avoided as it is difficult to control. It is to avoid damage to electrical connections, melting away of thin sheets and damage to other equipment where application of direct heat can cause distortion. It can also interfere with the heat treatment given to the job for a specific purpose. Hence a hand tool called soldering iron is used for indirect application of heat. The soldering iron is used to melt the solder in the soldering process. The bit…

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