The document discusses the open hearth furnace process used in foundries. The open hearth furnace uses direct contact between fuel and metals to melt iron, aluminum, and other materials. It consists of a shallow bath capable of holding 60-300 tons of metal, with heating chambers on the sides and openings at each end to allow heated gases to burn and escape. The furnace lining depends on the impurities in the metal. Once charged and heated to 1500C, the scrap and pig iron melt over 3 hours as impurities are removed. The molten steel is then tapped and deslagged before being poured into ingots or castings.

1. Open hearth furnace

2. What is furnace?
 Equipment to melt metals
 Casting
Change shape
Change properties
 It is a thermal enclosure used for melting
different materials materials such as iron
aluminum etc.

3. Foundry & Casting
 The place where casting is done is called
foundry.
 Casting is defined as:
 Casting is a manufacturing process by which
molten/liquid material is poured into a mold
containing a cavity of specific shape, and then
allowed to solidify. The solid casting is then
taken out and cleaned to complete the process

4. Furnaces Used In Foundry
 Following some furnaces are used in foundry:
• Blast furnace
• Cupola furnace
• Electric arc furnace
• Pit furnace
• Electric induction furnace
• Direct fuel fired furnace
Direct fuel fired furnace is our concern for presentation
today.

5. Direct Fuel Fired Furnaces
 Direct fuel Fired furnaces are those in which:
• Fuel is in direct contact with charge material
• Charge is heated by combustions products
• Material is heated by the way of heat transfer through a
solid wall.
• Heat transfer takes place through a liquid medium
surrounding the material.

6. Types Of Direct Fired Furnaces
• Important types are:
• Blast furnace
• Cupola furnace
• Open hearth furnace
• Pit furnace

7. Open Hearth Furnace
History:
 William siemens, developed the open hearth
process by preheating the incoming air.
 Pierre martin was responsible for dilution of pig
iron with scrap.
 By combining both siemens-martin open hearth
process is developed.

8. Construction
 Furnace can either tilting or fixed.
 The furnace consists of a shallow bath capable of
holding from 60 to 300 tons of metal at a time.
 There is back wall, doors in the front wall and a roof
over the top.
 On each side of bath is a set of two heating chambers
one is to pre-heat air and other to pre-heat coal
produced gas.
 These chambers are filled with open chequered bricks.

9. Contnd…….
 At each end of the hearth openings are provided.
Openings at one end is to allow the passage of heated
gas and air which burns with flame directed down on
the metal.
 2nd opening allows the burned gases to escape to the
chimney via regenerators.
 These regenerators are a series of chequered brickwork
heating chambers.
 Capacity is 10 to 300 tons.

10. Diagrams

11. Lining Of Furnace
 Lining can be acidic or basic depending
upon the nature of impurities.
 If impurities are acidic then acidic lining is
used like silica bricks and sand.
 If impurities are basic then basic lining is
used like magnesite bricks and dolomite.

12. Charging The Furnace
 Charging can be in cold and liquid state.
 What is mean by cold and liquid state???????
 The charge is pig iron, molten or solid iron and scrap.
 Limestone and iron ore added as required.
 It is charged by mechanical charging machine.
 To charge a basic furnace calcined dolomite or sand is
thrown over the bottom and side walls.
 This operation is called fettling(repairing the lining).

13. Cntnd…….
 After fettling hearth is heated about 1500c.
 Limestone on bottom is followed by iron ore then iron
and scrap.
 After about two hours when scrap has begun to melt
pig iron is added.
 After this melting period begins.

14. Working
 Heat is supplied to the furnace by burning the mixture of
gas and air.
 Melting may takes place in three hours depending upon
the nature and size of the charge.
 During this time some of the carbon and most manganese
and silicon has removed by oxidation.
 These impurities are removed by adding limestone
millscale and also by the oxidizing action of the flame.
 In boil stage last of carbon is removed.
 When melting is completed certain elements are added to
remove remaining impurities like, Si, S, and P.

15. Tapping
 Tapping is removal of molten product from the
furnace.
 When steel is judged for desired carbon content it
is than tapped.
 At this point slag float on the steel and it is
removed.

16. De-slagging
 Slag is removed in two stages;
 Some of the slag flows out of the notch during
the early part of the process.
 Remainder is separated by means of special
ladle.
When steel is poured into ingot molds retain the
slag

17. Uses
 Steel produced by open hearth is either of low (0.15-
o.3% carbon) or medium (0.3-o.7% carbon).
 Alloy steel is also produced by this process.
 Low (0.15-o.3% carbon) steel used in boilers plates,
bridge work, structural work etc.
 Medium (0.3-o.7% carbon) used in axels, hammers,
springs and dies.

18. Steel Castings
 Steel casting is a specialized form of casting involving
various types of steel.
 Steel castings are used when cast irons cannot deliver
enough strength or shock resistance.
 Examples of items that are steel castings
include: hydroelectric turbine,wheels,gears,railroad,tr
uck,frames, valve bodies, pump casings, mining machi
nery, marine equipment, and engine parts.