Mechanical tools

. purpose of heat treatment . purpose of annealing . difference between the processess of annealing and normalising The properties of steel depend upon its composition and its structure. The properties of steel and its structure can be changed by heating it to a particular temparature and then, allowing it to cool at a definite rate. The process of heating and cooling for changing the structure of steel,and thus obtaining the required properties is called ' heat treatment of steel '. If steel is heated to a suitable temaprature, and then, slowly cooled, the steel will be soft, weak and ductile. If steel is heated to a suitable temaprature, and then, rapidly cooled (quenched) the steel will be hard and brittle. Classification of heat treatments The treatments that produce equilibrium conditions are annealing and normalising. Treatments that produce non-equilibrium conditions are hardening and tempering (usually done in conjunction with each other) Annealing In this process, stee...

.   structural changes of plain carbon steel while heating . the structural changes of plain carbon steel in normal cooling Distinguish between the lower and upper critical temparature during heating and cooling. Heating While heating uniformly a piece of plain carbon steel in a furnace, the temparature will increase uniformly and it will be halted or will fall slightly for a short time although the heat is supplied to the steel. At this point, the heat, is being used to  cause a rearrangement of the iron atoms which, in turn,, causes the formation of a solid solution called austenite. The temparature at which austenite is formed is called the lower critical point (heating ) and is at 723°c. If the steel contains less than 0.83% carbon there will be some ferrite present after the above change also. And if it contains more than 0.83% carbon, there will be some cementite present after this change. If the heating is further continued, the ferrite or cementite present will be grad...

. The different methods of identifying ferrous metals and alloys . state how non ferrous metals and alloys are identified A fitter has to handle different types of metals in his  work. A knowledge about how to recognise and differentiate the commonly used metals will help him in many ways. Ferrous metals and alloys can be identified by Their appearance (colour, texture etc,) Their weight (light or heavy ) The sound Cold hammering The spark test (grinding ) Apart from the above tests steel bars are also identified by the code colours painted on them. Different colours are marked, based on the different composition of materials and grade. Colours charts are available to determine the different metals. Most non ferrous metals and alloys can be identified by their colour. copper colour is distinctive red colour Aluminum colour is  dull  white Lead colour is bluish grey colour Tin colour is silvery white, with a slightly yellowish tinge Brass colour is distinctive yellow colou...

The principle of the L. D converter Name the raw materials used for the charge in L.D process👍 L. D. Process The name L.D. is derived from the initials of two towns,LINZ & DONAWITZ in Austria where this process was first used. The L. D. is converter or the basic oxygen converter is designed to produce high quality steel in a relatively shorter time. The basic raw material used in the process are the molten pig iron from the blast furnace and the steel strap. Fluxing agents are used for reacting with impurities and form a slag on the top of the molten metal. In this process of 👍producing steel, a jet of pure oxygen is blown through a lance which is water cooled.The lance is brought near the molten metal and oxygen is blown at high pressure on the molten metal bath. This leads to the oxidation of carbon and other impurities causing violent agitation which allows all the molten metal to come in contact with the oxygen stream. When the blowing is over,the converter is tipped to remov...

.The different manufacturing processes of steel . manufacturing process of steel by the bessemer process . distinguish between acid process and basic process Manufacturing processes The different manufacturing processes of steel -Bessemer process -L. D process -Electric process -Open hearth process Bessemer process Sir Henry Bessemer, a British engineer invented this process of converting molten pig-iron to steel  using a large pear shaped container. This is called the Bessemer converter. It is a method of producing steel by blasting compressed air through molten iron and burning out the excess carbon and other impurities. This does not use any source of heat other than obtained from the oxidising process used to remove carbon and other impurities. The three stages of this process are -the preliminary stage (The slag formation ) -the boil stage (The brilliant flame blowing period) -the finishing stage (The reddish smoke period ) The molten pig iare from the blast furnace is poured ...