Carbon Based Refractories...

Carbon Based Refractories Carbon based refractories behave differently than the typical ceramic refractories, primarily because carbon based refractories are conductive rather than insulating. All carbon based refractory lining systems perform as a ‘conductive cooling system’ as opposed to a classic definition of a refractory lining that is typically an ‘insulating system’. Consequently, proper cooling must always be utilized with any carbon based refractory lining system to assist in maintaining refractory temperatures that are below the critical chemical attack temperature for mechanisms such as oxidation, alkali, CO degradation, or dissolution of the carbon by liquid metal. The words ‘carbon’ and ‘graphite’ are often used inter-changeably, but the two are not synonymous. Additionally, the words ‘semi-graphite’ and ‘semi-graphitic’ are also similarly misused. Carbon based refractories are basically classified¬† in three categories namely (i) carbon refractories, (ii) carbon containing basic refractories, and (iii) carbon containing non basic refractories. (Fig 1) Fig 1 Carbon based refractories ¬†Within the area of carbon based refractories, phenol-formaldehyde (Phenolic) resins have found a multitude of uses. One significant attribute of phenolic resins is their ability to form a carbon bond. This, to a large extent, contributed to their initial use in this Industry, as cleaner alternatives to the traditional pitch and tar binders. Also as the industry increased usage of carbon bonded products, phenolic resin bonded products have replaced more and more the traditional ceramic bond in many areas of liquid metal contact. Phenolic resins can also dramatically improve production rates and consistency of refractories. Their low temperature curing characteristics give dimensional stability, and in many applications, the final heating of the product to form the carbon bond, can be carried after the product has been installed at the customer.¬† They have excellent compatibility with many refractory raw materials, and give good...