Cast basalt

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Cast basalt is a mineral material for plant components in which the conveyed material mainly causes abrasive wear - e.g. B. bunkers, chutes, troughs, trough chain conveyors, mixers, separators, pipes, pipe bends, cyclones, etc.

Manufacture of cast basalt

The starting product for the production of cast basalt is dense, selected basalt , which occurs in various external shapes and different mineralogical compositions.

The appropriately selected basalt is broken down to a grain size of 20/50 mm and melted at a temperature of approx. 1250 ° C. In continuous operation, the liquid basalt first flows from a hearth furnace into the forehearth with various installations for refining. From there, the cast basalt then flows into sand molds, permanent molds or centrifugal molds. After the cast parts have solidified, the fittings or pipes are placed in a tempering and cooling furnace. At this point in time, the castings still have an uneven structure and tensions, which are relieved by controlled temperature control in an approx. 24-hour process. The result is molded parts which, due to their structure and hardness, are suitable as highly wear-resistant linings.

Properties and technical data

Bulk density 2.8 .... 2.9 kg / dm³ according to DIN 51065
Compressive strength 450 N / mm² according to DIN 52105
Thermal conductivity 1 ... 1.16 W / m * k according to DIN 52612, part 1
Mohs hardness about 8 (diamond 10)
Electrical resistance 10,000 ohms
Specific heat capacity 0.8kj / kg * K

Cast basalt is a mineral material with high compressive strength and high modulus of elasticity , with very high abrasion resistance, although at the same time there is a certain impact sensitivity. In addition to its wear resistance, cast basalt also has the advantage that it does not rust and is acid-resistant. This guarantees a smooth sliding surface at all times. Even with moist material to be conveyed, blockages and bridging are largely avoided after a standstill.

history

In France, in the laboratories of the Technical University in Paris, the first attempts were made to smelt basalt, but these attempts did not get beyond the laboratory stage. In 1909, the French doctor Dr. Francois Ribbe with carrying out smelting tests on a larger scale with basalt. He soon realized that pure melting gave him a kind of black glass, which however did not have the properties of natural basalt , was under great tension and easily shattered.

With the support of the Technical University of Paris, the Compagnie Générale du Basalte finally succeeded in producing a usable material after very lengthy attempts. Towards the end of the First World War , this material was used on a larger scale in France in the electrical industry for insulators, but above all in the operation of the famous Parisian subway, the metro, in which cast basalt was placed between the guide rails and a normal rail.

These successes of the French company led to a German-French group joining forces and starting the production of fused basalt in Vettelschoss-Kalenborn. However, the product was different than in France. This was due to the diversity of the raw basalt and also to the melting and tempering technology. The cast basalt had a higher iron content and was therefore not suitable for insulators like the one in France. So they looked for new areas of application and from 1937 onwards it was possible to use cast basalt as wear protection in coal mining and in the metallurgical industry.

During the Second World War , cast basalt replaced iron and steel in many places in industry. B. in hard coal and potash mines, in ore mining, in coking plants and in the then very important fuel plants for synthetic gasoline.

To this day, cast basalt is used to line plant components that are subject to heavy wear.

See also