puddling furnace

Done by Donella Long-David

PUDDLING FURNACE PARTS & PROCESS

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.

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.

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.


Tap Cinder – slag produced during the process of puddling. Smelting – extract (metal) from its ore by a process involving heating and melting.


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.


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.

1 s t Definition of puddling 2n d Definition of puddling

WHAT IS PUDDLING?

IMAGE OF A PUDDLING FURNACE

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

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

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

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

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

• 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

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

puddling furnace

Engineering