CARBON GRAPHITE REFRACTORIESANDCERAMIC GRAPHITEREFRACTORIESPRESENTATION BY : PRAVEEN KUMAR

S5 , MTG ROLL NO : 23 AJCE

Materials which withstand high temperature and do not fuse even at very high temperature.

WHAT IS A REFRACTORY ?

Types of refractories

There are three type of refractories

Acidic refractories

Basic refractories

Neutral refractories

CARBON GRAPHITE REFRACT-ORIES

CARBON GRAPHITE REFRACTORIES

Graphite is a crystalline form of carbon and its natural deposit is known as “Plumbago”.

Coke has been used as a cheap substitute for graphite but not satisfactory. Bonding materials for carbon refractories are usually tar or pitch (free from

ammonia or light oils). Graphite is found in Karnataka, Bihar and Orissa.

The basic definition…

CARBON GRAPHITE REFRACTORIES

How its made?

Cool the mould

Moulded in wood

Shovel thor-

oughlyAdd hot tar/pitch

Spread it on floorStored dryCoke is

crushed

CARBON GRAPHITE REFRACTORIES

Precautions while manufactur-ing…

The coke used must contain less than 8% ash. Crushing or grinding must reduce the size of coke to 1-2mm size. While mixing with shovels, be quick so as to avoid formation of lumps. The moulds used (wooden or iron) must be oiled before use. The bricks must be cooled in ventilated rooms. Exposure to sunlight can make them soft.

CARBON GRAPHITE REFRACTORIES

Graphite is infusible and sublimes at 3600°C. It is not attacked by any slag or chemicals except in the presence of oxygen as it

oxidises at elevated temperatures. It is resistant to thermal shocks. Have high thermal as well as electrical conductivities. Porosity value vary from 20% – 25%. They are light grey in colour and give a ringing sound when struck. Cold crushing strength is about 350 Kg/Cm2.

Properties…

CARBON GRAPHITE REFRACTORIES

Extensively used in lining the hearth and bosh of the Blast furnace. Also used in furnaces where temperature is high and the atmosphere is non-oxid-

ising. They may be also used in the lower stack wall of the Blast furnace also. Iron and slag runners are also lined with carbon refractories due to lower shrink-

age. Graphite crucibles of varied sizes are used for melting cast iron, aluminium, cop-

per etc. Carbon is used as a ramming mixture with tar for construction of electrolytic cells.

Uses…

CARBON GRAPHITE REFRACTORIES

How does it look like?

CERAMIC -GRAPHITE RE-FRACTORIES

CERAMIC -GRAPHITE REFRACTORIES

New class of carbon refractories. Examples are magnesia graphite and alumina graphite. Composition of Magnesia Graphite Bricks, C = 5-20% CaO = 2.2-2.4% SiO2 = 0.7-1.5% Fe2O3 = 0.3-0.4% Al2O3 = 0.3-0.4%

The basic definition…

CERAMIC -GRAPHITE REFRACTORIES

High thermal spalling resistance. Reduced specific refractory consumption. Resistance to action of slags. Cold crushing strength after tempering varies from 323-633 Kg/Cm2. Bulk density after coking is 2.76-2.99 gm/cc. Bulk density after tempering is 2.80-3.04 gm/cc. Very high fusion point.

Properties…

CERAMIC -GRAPHITE REFRACTORIES

How does it look like?

THANK YOU…