Furnaces For Casting Process

Furnaces For Casting Process:

Furnaces are used for heating and melting of metals to be poured into the mold for casting.

The most important thing is the selection of furnaces which depends on:

• Casting alloy melting and pouring temperature.
• Capacity reqiurement of furnace.
• Variety of metals or alloys to be melted.
• Costs of investment.
• Fuel and maintenance.
• Environment Pollution.

Types of Furnace Used in Casting:

There are many furnaces among them we are discussing 5 of them:

1. Cupolas:

A type of furnace which is vertical cylinder furnace equipped with tapping spout near base.

Steps involved in this process are as follows:

• Only used for cast iron.
• It consist of a steel plate lined with refractory.
• The charge consisting of iron, coke, flux, and alloying metal is loaded through a charging door located less than halfway up height of cupola.
• Coke is used as fuel.
• Forced air is introduced for combustion of coke.
• Flux (limestone) is used to form slag.
• 
  

2. Direct Fuel-Fired Furnaces (or Reverberatory Furnace):

• Charge is heated in a small open-hearth by natural gas fuel burners located on the side of furnace.
• Flame is reflecting down by the furnace roof.
• Molten metal is released from the tap hole located at the bottom of hearth.
• Natural gas is used as fuel.
• Only for non-ferrous metal like copper-base alloys and aluminium.

3. Crucible Furnaces (or Indirect Fuel-Fired Furnace):

• Metal is melted without direct contact with burning fuel mixture.
• Container is made of refractory material pr high temperature steel alloy.
• Only for non-ferrous metals like bronze, brass and alloy of zinc and aluminium.
• Oil, gas or powdered coal is use as fuel.

There are three types of Crucible Furnace:

1. Lift-out Crucible Furnace  ➣  molten metal is transfered by hook.
2. Stationary Pot Crucible Furnace   ➣  molten metal is transfered by a pot.
3. Tilting Pot Crucible Furnace  ➣  molten metal is transfered by wheel.

4. Electric-Arc Furnaces:

Furnaces in which heat is generated from an electric arc.

• High power consumption but having melting capacity 25-40 tons/hr.
• Only for steel and ferrous alloys.
• Rapid melting rate.

5. Induction Furnaces:

• It uses alternating current passing through a coil to develop magnetic field in metal.
• Induced current causes rapid heating and melting.
• Only for melting steel, cast iron and aluminium alloys.
• Fast melting rate and high cost operation.

Ladles:

Molten metal is transfered from furnace to other container by ladles or Crucibles.

There are two types of ladles used in Industries:

1. Crane Ladle   ➣   For handling large volumes of molten metal using overhead cranes.
2. Two-man Ladle   ➣   For moving and pouring smaller amounts of molten metal.

Reference:

• University Notes 
• Book Fundamental of Modern Manufacturing 6th Edition by Mikell P. Groover
• Videos from youtube and Google 
• Images from google images