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Basic Thermodynamic Processes

Thermodynamics is a branch of physics concerned with heat and temperature and their relation to energy and work. It defines macroscopic variables, such as internal energyentropy, and pressure, that partly describe a body of matter orradiation. It states that the behavior of those variables is subject to general constraints, that are common to all materials, beyond the peculiar properties of particular materials.


Basic Thermodynamic Processes :-

1) Isothermal process
                                            When the system undergoes change from one state to the other, but its temperature remains constant, the system is said to have undergone isothermal process. For instance, in our example of hot water in thermos flask, if we remove certain quantity of water from the flask, but keep its temperature constant at 50 degree Celsius, the process is said to be isothermal process.

2) Isochoric process

                                             The process, during which the volume of the system remains constant, is called as isochoric process. Heating of gas in a closed cylinder is an example of isochoric process.

3) Isobaric process

                                         The process during which the pressure of the system remains constant is called as isobaric process. Example: Suppose there is a fuel in piston and cylinder arrangement. When this fuel is burnt the pressure of the gases is generated inside the engine and as more fuel burns more pressure is created. But if the gases are allowed to expand by allowing the piston to move outside, the pressure of the system can be kept constant.

4) Reversible process

                                             In simple words the process which can be revered back completely is called a reversible process. This means that the final properties of the system can be perfectly reversed back to the original properties. In practical situations it is not possible to trace these extremely small changes in extremely small time, hence the reversible process is also an ideal process.

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Steel Making & Processing

Steel making:-

Molten iron from the blast furnace is sent to a basic oxide furnace, which is used for the final refinement of the iron into steel. High purity oxygen is blown into the furnace and combusts carbon and silicon in the molten iron. The basic oxide furnace is fed with fluxes to remove any final impurities. Alloy materials may be added to enhance the characteristics of the steel.


Steelmaking further refines the iron by removal of carbon, silicon, sulfur, phosphorous, and manganese. In an integrated mill, the molten iron along with a certain amount of scrap is charged into a basic oxygen furnace (BOF) in which oxygen and fluxes are used to oxidize the impurities out of the iron melt. After the steel has been refined, the furnace is tilted (opposite to the charging side) and molten steel is poured out into a preheated ladle. Alloys are added to the ladle during the pour to give the steel the precise composition desired. In some steelmaking applications, further refining is conducted in the ladle to remove oxygen and sulfur from the molten steel. This is a process called "Tapping."

Coke making:-

Coke and coke by-products are produced by the pyrolysis1 (heating in the absence of air) of suitable grades of coal. The process also includes the processing of coke oven gas to remove tar, ammonia (usually recovered as ammonium sulfate), phenol, naphthalene, light oil, and sulfur before the gas is used as fuel for heating the ovens. In the coke-making process, bituminous coal is fed (usually after processing operations to control the size and quality of the feed) into a series of ovens, which are sealed and heated at high temperatures in the absence of oxygen, typically in cycles lasting 14 to 36 hours. 

Iron making:

During iron-making, iron ore, coke, heated air and limestone or other fluxes are fed into a blast furnace. The heated air causes the coke combustion, which provides the heat and carbon sources for iron production. Limestone or other fluxes may be added to react with and remove the acidic impurities, called slag, from the molten iron. The limestone-impurities mixtures float to the top of the molten iron and are skimmed off, after melting is complete.


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Types & Classification Of Furnaces

A furnace:- is an equipment to melt metals • for casting or • for heating materials or • for change of shape (rolling, forging etc) or for change of properties (heat treatment).

Types and classification of furnaces:-

Furnace classification Recuperative Regenerative According to mode of heat transfer According to mode of charging Mode of heat recovery Open fire place furnace Heated through liquid medium Periodical Forging Re-rolling (Batch / continuous pusher) PotContinuous Glass tank melting (regenerative / recuperative) Based on the method of generating heat: combustion type (using fuels) and electric type.

Melting Practices Melting:- 
is an equally important parameter for obtaining a quality castings. A number of furnaces can be used for melting the metal, to be used, to make a metal casting. The choice of furnace depends on the type of metal to be melted. Some of the furnaces used in metal casting are as following: 
 1-Crucible furnace Cupola.     
 2-Induction furnace.     
 3-Reverberatory furnace .

Crucible furnaces:- 

are small capacity typically used for small melting applications. Crucible furnace is suitable for the batch type foundries where the metal requirement is intermittent. The metal is placed in a crucible which is made of clay and graphite. The energy is applied indirectly to the metal by heating the crucible by coke, oil or gas. The heating of crucible is done by coke, oil or gas. 

Induction furnace : 

Induction heating is a heating method. The heating by the induction method occurs when an electrically conductive material is placed in a varying magnetic field. Induction heating is a rapid form of heating in which a current is induced directly into the part being heated. Induction heating is a non-contact form of heating. The heating system in an induction furnace includes:      
1. Induction heating power supply,      
2. Induction heating coil,      
3. Water-cooling source, which cools the coil and several internal components inside the power supply.

Reverberatory furnace : 

A furnace or kiln in which the material under treatment is heated indirectly by means of a flame deflected downward from the roof. Reverberatory furnaces are used in copper, tin, and nickel production, in the production of certain concretes and cements, and in aluminum. Reverberatory furnaces heat the metal to melting temperatures with direct fired wall-mounted burners. The primary mode of heat transfer is through radiation from the refractory brick walls to the metal, but convective heat transfer also provides additional heating from the burner to the metal. 

Suspension System

Suspension is the system of tires, tire air, springs, shock absorbers and linkages that connects a vehicle to its wheels and allows relative motion between the two.
Suspension systems serve a dual purpose — contributing to the vehicle's roadholding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants comfortable and a ride quality reasonably well isolated from road noise, bumps, and vibrations.

The components of the suspension consist of:
  • Tires
  • Wheels
  • Shock absorbers
  • Mcpherson struts
  • Springs
  • Sway bars
  • Torsion bars
  • A arms
  • Lower control arms
  • Axles
  • Alignment
  • Tire pressure
The various components of the suspension systems of every vehicle are designed to counteraffect the forces of gravity and inertia! Even though every car is different, every system accomplishes the same objective:-
  •  Keeping tires on the road surface. Engineers call this "road holding". It's important for the tires to stay in contact at all times, because friction between the tires and the ground is what lets the car accelerate, stop and corner. The suspension keeps the weight centered to maintain the grip.
  • Stable steering and handling. The suspension keeps the car or truck body from tipping or rolling in a corner.
  • Passenger comfort. Keeps the cabin isolated from the bumps on the road. Suspensions absorb that up-and-down energy and disperse it without too many bobbles.
     How does the Suspension System work?

The suspension system connects your vehicle to its wheels. It is designed to counteract the forces of gravity, propulsion and inertia that are applied to your vehicle as you accelerate, slow down or stop in such a way that all four wheels remain on the ground!

The tires - which are mounted on your vehicle’s wheels (or rims) - are the most important and visible components of the system. They transfer the power of the engine to the ground when your vehicle moves and they counter that motion when it stops.

As you drive over a bumpy road, shocks are absorbed by the combined work of a shock absorber (or damper) and a coil or leaf spring mounted on each wheel. The spring is a device that stores energy in order to supply it later on. It is actually the spring that handles the abuse of the road by allowing the wheel to move up and down with respect to the frame of the vehicle. In return, the shock absorber softens the suspension moves entailed by the spring by “absorbing the shocks”. The shock absorber is a steel or aluminum hydraulic cylinder filled with oil and pressurized with nitrogen. As the suspension moves, a piston is forced to move through the oil-filled cylinder. The energy produced from the motion of the piston is dissipated as heat which in turn is absorbed by the oil.

     Types of suspension system for independent system
  • MacPherson strut type
  • Double wishbone type
  • Semi trailing arm type
MacPherson strut type :
This system is usually use for most widely in independent suspension system for small and medium sized cars.These type are so popular so in FF(Front engine and front wheel transmission)type of car,used as the rear suspension.
Characteristic for MacPherson: The construction of the suspension is relatively simple. MacPherson type,have small number of parts,so when it component is less,then less weight.The effects is unsprung can be reduce.

The space for the suspension is small,the usable space in the engine compartment can be increased. Since the distance between suspension support point is great,there is a little disturbance of the front wheel allingment due to installation error or part manufacturing error.Therefore, except for toe-in,allingment adjustment ordinarily unnecessary.

Double wishbone type:
This is usually used for front suspension for small trucks and for front and rear suspension for passenger cars. Characteristic for double wishbone: Wheels are mounted to the body via upper and lower arm. Suspension geometry can be designed as desired according to the length of the upper and lower arm and their mounting angles.

For example if upper and lower arm are parallel and have equal length,the tread and the tire-toe ground camber of the tire will change.As a result,it is not possible to obtain adequate conering performance.In addition, in the tread will cause excessive tire wear.

To solve this a design is normally employed in which the upper arm is made shorter than the lower arm so that the tread and the tire-to-ground camber of the tire fluctuate less.

Semi trailing arm type:-

Is used for the rear suspension in a few models.With this suspension,the amount by which the toe angle and camber change(due to the up-and-down motion of the wheels) can be controlled at the design stage, in order to determined the handling characteristics of the vehicle.

Signs of troubles related to the Suspension System:
  • Excessive tire wear
  • Poor steering control or off-center steering wheel
  • Excessive bouncing over road bumps
  • Loss of control during sudden stops
  • Excessive swerving while changing lanes
  • Front-end nose diving during quick stops
  • Vehicle sag in front or rear

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Casting process & it's Types

Casting:-
is a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process”  Casting materials are usually metals or various cold setting materials that cure after mixing two or more components together; examples are epoxy, concrete, plaster and clay. Casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods.


Types of casting…!!! 
 Following are the basic types of casting:-
 1-Sand casting :-
also known as sand molded casting, is a metal casting process characterized by using sand as the mold material. The term "sand casting" can also refer to an object produced via the sand casting process. Sand castings are produced in specialized factories called foundries. Over 70% of all metal castings are produced via a sand casting process ,Sand casting is relatively cheap and sufficiently refractory even for steel foundry use. 


 2-Die casting :-
Die casting Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process.

 3-Shell mold casting :-
is an expendable mold casting process that uses a resin covered sand to form the mold.  As compared to sand casting, this process has better dimensional accuracy, a higher productivity rate, and lower labor requirements. It is used for small to medium parts that require high precision.

 4-Permanent mold casting :-
 is metal casting process that employs reusable molds ("permanent molds"), usually made from metal. The most common process uses gravity to fill the mold, however gas pressure or a vacuum are also used. A variation on the typical gravity casting process, called slush casting, produces hollow castings. 

 5-Investment casting (lost wax casting) :-
is an industrial process based on and also called lost-wax casting, one of the oldest known metal-forming techniques .From 5,000 years ago, when bees wax formed the pattern, to today’s high-technology waxes, refractory materials and specialist alloys, the castings allow the production of components with accuracy, repeatability, versatility and integrity in a variety of metals and high-performance alloys.

 6-Lost-foam casting:-
is a type of evaporativepattern casting process that is similar to investment casting except foam is used for the pattern instead of wax. This process takes advantage of the low boiling point of foam to simplify the investment casting process by removing the need to melt the wax out of the mold

7-Centrifugal casting:-
Centrifugal casting or roto-casting is a casting technique that is typically used to cast thinwalled cylinders. It is noted for the high quality of the results attainable, particularly for precise control of their metallurgy and crystal structure. 
 
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