The document defines various terms used in the puddling process such as pig iron, blast furnace, slag, and cast iron. It then describes the puddling process which involves charging pig iron into a heated furnace, melting and stirring the iron to separate impurities into slag, and forming balls of purified wrought iron called blooms. The puddling furnace was developed by Henry Cort in 1784 and was widely used in the UK in the 19th century to produce high-grade bar iron, before being replaced by open-hearth furnaces.

1. Done by Donella Long-David
PUDDLING FURNACE PARTS &
PROCESS

2. Wrought iron – a tough malleable form of iron suitable for forging or rolling
rather than casting, obtained by puddling pig iron while molten. It is nearly
pure but contains some slag in the form of filaments. Wrought is one of two
forms in which iron is obtained by smelting; the other is cast iron.
TERMS USED TO UNDERSTAND
PUDDLING PROCESS.

3. Pig iron – crude iron as first obtained from a smelting furnace, In the form of
oblong blocks.
CONTINUATION OF TERMS USED
TO UNDERSTAND PUDDLING
PROCESS.

4. Blast furnace – the purpose of a blast furnace is to chemically reduce and
physically convert iron oxides into liquid iron called “hot metal”.
Slag – stony waste matter separated from metals during the smelting or
refining or ore.
CONTINUATION OF TERMS USED
TO UNDERSTAND PUDDLING
PROCESS.

5. Tap Cinder – slag produced during the process of puddling.
Smelting – extract (metal) from its ore by a process involving heating and
melting.
CONTINUATION OF TERMS USED
TO UNDERSTAND PUDDLING
PROCESS.

6. Cast iron – a hard, relatively brittle alloy of iron and carbon which can be
readily cast on a mould and contains a higher proportion of carbon than steel.
Industrial revolution - was the transition to new manufacturing process from
about 1760 to sometime between 1820 and 1840. This transition included
going from hand production methods to machines.
CONTINUATION OF TERMS USED
TO UNDERSTAND PUDDLING
PROCESS.

7. Puddling was one step in one of the
most important process of the first
appreciate volumes of high-grade bar
iron (malleable wrought iron) during
the industrial revolution. – developed
by Henry Cort.
The puddling furnace is a metal
making technology used to create
wrought iron or steel from the pig
iron produced in a blast furnace.
Developed by Henry Cort.
1st Definition of puddling 2nd Definition of puddling
WHAT IS PUDDLING?

8. IMAGE OF A PUDDLING FURNACE

9. Having prepared the hearth and brought the furnace to a good heat, a charge of
about 1500 lbs. of pig iron is thrown in at the working door, and with it is a
charged quantity of cinder or squeezer scale.
1. The door is closed tightly, and the heat is so regulated that the iron and
cinder become pasty and melt down together. The requires about 30
minutes, and is called the melting-down stage.
2. After the charge has been melted and the iron and cinder well mixed, the
clearing stage follows. The puddler’s helper uses an iron bar with a bent end
to stir the whole charge thoroughly, working through the hole in the door.
The stirring brings the impurities of the iron into contact with the oxides of
the hearth and of the charge, and these, assisted by any oxygen coming from
the air which enters through the fire box, oxidize the remaining silicon,
manganese and a further amount of the phosphorus. During this stag, the
furnace is kept very hot. A slag is formed, containing the oxidized impurities
and much iron oxide.
PROCESS OF PUDDLING FURNACE

10. 3. The next step is the boil, from which this whole process gets its name of “pig
boiling” phosphorus. During this stage the chimney damper is lowered and
the working door opened to reduce combustion and produced an oxidizing
flame. The charge is stirred thoroughly and constantly with the hoe or rabble
(or, to use the expression of puddling, is rabbled). This action brings the
carbon of the metal in contact with the iron oxides of the heart and the
charge, causing carbon and oxygen to unite, forming CO, which bubbles
violently from the surface of the molten charge. This bubbling causes the
lighter slag to boil over the side of the basin and flow from the furnace ,
carrying with it many of the oxidized impurities, Sulphur is eliminated mostly
as iron pyrites in the slag boil. As the carbon burns, the charge becomes more
and more quiet.
The removal of the carbon having lowered greatly the melting temperature of the
iron, small masses of plastic metal begin to collect. Just as butter collects in the
churn. The iron is said to “come to nature” in thus collecting.
CONTINUATION OF PROCESS OF
PUDDLING FURNACE

11. 4. In the final stage, the puddler gathers these into balls of about 150 lbs.
each, called blooms, or puddle balls. The furnace temperature is gradually
raised, and the puddle balls are bought to a welding heat. The puddler
presses them sufficiently to make them hold together and they are then
removed from the furnace. After their removal the excess of slag is
tapped out and the furnace is ready for a new charge.
Each heat requires about two 2 or 2 ½ hours.
CONTINUATION OF PROCESS OF
PUDDLING FURNACE

12. Puddling furnace is often termed by chemists a highly basic silicate of iron,
for it contains a very large proportion of oxide of iron and a small proportion
of silica, but it always contains much phosphorus and Sulphur extracted from
the iron, these being present, respectively, in the forms of phosphate and
sulphuret of iron. The results of the analysis of a sample are subjoined.
PROPERTIES OF PUDDLING
FURNACE

13. Iron 54.33%
Oxygen 16.87%
Silica 8.32%
Phosphoric acid. 1. Phosphorus 3.18%, 2. Oxygen 4.11% 7.29%
Sulphuret of Iron. 1. Sulphur 2.57%, 2. Iron 4.50% 7.07%
Lime 4.70%
Oxide of Manganese 0.78%
Magnesia 0.26%
Total 99.62%
COMPOSITION OF TAP CINDER
FROM THE PUDDLING FURNACE

14. • Invent in 1784
• Not currently operated
• Replaced with the open-hearth furnace
• Was widely used in United Kingdom in the 19th century.
• Puddling has not been used in USSR since 1930’s.
FACTS ABOUT PUDDLING
FURNACE

15. 1. Metals: Their properties and treatment. 5th Edition, Page 60-61
2. An elementary outline of mechanical processes by G.W. Danforth.
Chapter 108.
3. The theory and practice of Metalwork. Third edition by George Love.
4. The Motivate Series – Metalwork Technology.
REFERENCES