CONTINUOUS CASTING PROCESS ( A Type of Permanent Mold Casting)

Continuous Casting is used in general for the production of rods, pipes, sheet metal and other articles known as semi-finished products in an uninterrupted process.

The main feature of the process is the pouring of molten steel through a tower nearly 300m high ; this replaces the casting of ingots, the removal of molds from ingots, the re-heating of ingots, and their primary rolling. To understand what this shortcut means, one has only to go over the principal operations in a conventional plant.

In a conventional plant, after pig iron has been turned into steel- say, first, in a Bessemer Converter and then in what is known as an open hearth furnace- the white-hot molten steel flows into a huge ladle ; The ladle is carried by a crane and the molten steel is poured from it into a number of molds to form ingots, i.e., pieces of steel of manageable size for further processing ; the ingots are then carried to a mill for rolling ; They are first re-heated and then put between rollers ; the products emerge in a uniform, elongated shape, chopped off into convenient lengths, for use in the final fabrication of steel products.

The method of continuous casting dispenses with these separate and somewhat cumbersome stages. Instead of making ingots and then reheating them for rolling , molten steel is poured steadily from the top of a tower into a long mold, cooled by water, and the passage of the steel through the mold is so controlled that the metal emerges from the other end in the shape of the products of primary rolling mill.

The main task is to devise a suitable mold that will withstand the heat and fasten the solidifying steel into desired shape , without obstructing its steady flow. The substance used for mold is copper, with an efficient cooling system.

The method has not yet been developed to such an extent as to lead to its universal introduction; questions of economics and quality are still being examined.

Molten metal is poured into a metal mold which is cooled by water without interruption by appropriate device. Thus, the casting solidifies and is fed still red-hot to a rolling mill or cut into pieces of required length. The pulling plate 1 is used to pull the solid product in the continuous length.

Comments

THROTTLE GOVERNING OF STEAM TURBINES

Steam Pressure at inlet to a steam turbine is reduced by throttling process to maintain the speed of the turbine constant at part load and hence this method of governing is called "Throttle Governing". Construction : Throttle governing system consists of a centrifugal governor, a lever , an oil pump , a pilot piston , control valve , a relay piston and a throttle valve. The throttle valve is moved by a relay piston. The relay piston is actuated by pilot piston control valve. There are two piston valves covering ports in the pilot piston control valve without any overlap. These piston valves are operated by lubricating oil supplied by a gear pump at 2 to 4 bar. The oil returns to the drain from this chamber. Working : When the turbine works on full rated load, the throttle valve will remain open. When the load is decreased, the energy output of the turbine becomes in excess and the turbine shaft speed increases. Hence, governor sleeve will lift. The upward movement of the

ELECTRICAL COMPARATORS AND ITS WORKING

Electrical Comparators are used as a means of detecting and amplifying small movements of a work contacting elements. An electrical comparator consists essentially of a pick-up head or transducer for converting a displacement into a corresponding change in current and a meter or recorder connected in the circuit to indicate the electrical change, calibrated to show in terms of displacement. Generally, an amplifier is needed to provide the requisite sensitivity and to match the characteristics of different parts of the circuit. Electrical comparators can be classified according to the electrical principle used in the pick-up head. Most of the comparators use either a differential transformer, an inductance bridge, a strain gauge or a capacitor as a means of detecting movement of the gauging element. There are different types of electrical comparators. One kind called an electrolimit gauge is used to check or measure the outside diameter of a roll. The object to be checked is place

Advantages And Disadvantages Of Air Refrigeration System :

Advantages Of Air Refrigeration : 1. The refrigerant used namely air is cheap and easily available. 2. There is no danger of fire or toxic effects due to leakages. 3. The weight to ton of refrigeration ratio is less as compared to other systems. Disadvantages Of Air Refrigeration : 1. The quantity of Refrigerant used per ton of refrigeration is high as compared to other systems. 2. The COP of the system is very low. Therefore running cost is high. 3. The danger of frosting at the expander valves is more as the air contains moisture content.

Mechinopedia For Mechanical Engineers

Search This Blog