Foundries, Steel Plants, Rotary Kilns and Ferrometal Industries
Article by Dave Thomas - Technical Director - Durocast

Vereeniging-based refractory manufacturer Durocast has adapted high-technology concretes normally used in blast furnace runners and steel plant ladles, to make them suitable for use in foundries.

High-technology refractory concretes have been developed for demanding steel-plant applications and successes have been achieved in blast-furnace slag and metal runners and in large steel ladles.

Two different product ranges – Durotherm and Durapid – have been developed. Durotherm products are mixed with water in a pan mixer and vibrated into place like standard concrete. Durapid products which are designed for use in hot conditions are used in the same way except that the water is replaced by a binder liquid. These castables are manufactured with tight tolerances to give low porosity linings with a very small quantity of fluxing impurities.

The materials have been designed to have a strongly exothermic setting reaction, which partially dries the lining and makes it less likely to be damaged by normal heat up procedures, Thomas says. “In most applications, those linings have been found to have a performance at least equivalent to a brick lining while requiring less skill to install,” he reports.

He says that the long time required to cool furnaces and kilns, install a new lining, cure it and bring it up to operating temperature, is another problem the refractory industry faces.

Maximum use has been made of locally available raw materials to make the products affordable, he says, adding that the sophisticated binder systems have maintained the exceptional corrosion resistance and outstanding cost or performance benefits of the products.

Thomas says that the performance of these materials has been monitored over a period of several years in a number of applications and they have become standard at a number of larger foundries.

“During the trial period, special emphasis has been placed on making the products easy to use so that specialist installation companies are not required,” he reports.

The Durapid range of chemically-bonded concretes has been designed to dramatically reduce the time required. The Durapid materials can be installed at ambient or at temperatures up to several hundred degrees, he reports, adding that setting occurs in less than three hours and that it can then be heated to operating temperatures of accelerated rates.

“The cost of downtime on many units is high and substantial savings have been made by many users,” Thomas says, adding that substantial savings in downtime have been made at Ispat Iscor Vanderbijlpark and Dunswart without having to compromise on the quality of the installed product.

Another application is rebuilding the taphole blocks of ferroalloy furnaces during maintenance periods without fully cooling the furnace. Durapid products have the same high purity and low porosity found in the Durotherm range. These products have found a number of uses in foundries and in production of special metals such as zinc and lead.
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