Bimetallic blanks are thus called because they are made of a base material which acts as support. The inner alloy has a thickness of about 2mm, with specific characteristics according to the needs of the material to be processed.
The adhesion of bimetal to the base material results from a combined process of temperature and centrifugation. Alloy casting inside the base material is possible applying the suitable and controlled temperature. Furthermore, the alloy spreads along the blank by centrifugation and sticks to the base material by fusion.
Process (PCC)
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We start from a solid bar of structural or forged steel.
The exterior will be turned and the interior core perforated in order to convert it in a thick-walled tube.
The chosen alloy will be prepared for “centrifugation”.
The alloy is inserted in the interior of the thick-walled tube, together with some fluxes that protect the oxidation (similar to the welding process).
Both sides of the tube are plugged, leaving a small gas outlet.
The tube enters in the furnace to the melting temperature of the alloy (always less than the melting temperature of steel of the thick-walled tube).
Once the alloy has cast inside the tick-walled tube, it is brought to a “centrifuge”, which rotates the tube at high speed.
Temperature descends while the fused alloy is deposited, by centrifugal force, on the inner walls of the tube.
The tube is cooled by air.
The plugs of both sides are cut.
The interior of the tube is finished by honing, leaving the interior to the whished diameter.
The centrifugated tube is finished.
The process to obtain bimetallic blanks requires a high technological level. This, along with the knowledge gained over 30 years, have given us a high-quality standard, which is recognised by the world’s leading machine manufacturers.
Talleres Pena has 2 complete lines to centrifuge tubes with gas Technology.
Qualities
The base materials (support) used for centrifugation are:
Steel developed by Talleres Pena SL used to withstand high pressures. Usually used as base steel for the centrifugation of injection cylinders.
Steel used as support for extrusion cylinders.
Stainless Steel used for base material of centrifugation in special cases that require applications of high corrosión resistance.
The Bimetallic alloys used for the internal coatings of the cylinders are:
An iron base alloy with a hardness between 62 HRC and 68 HRC. It has excellent abrasion resistance and good corrosion resistance. These characteristics make it suitable for processing abrasive materials with high loads, glass fibres, calcium carbonate, etc. complemented with materials of moderate corrosion resistance like fire retardants.
A Nickel/Cobalt base alloy. It is appropriate for cylinders that process corrosive products such as fluorinated polymers or products that may contain acids.
A Nickel base alloy with chromium, boron, silicon, etc. It is suitable for processing highly corrosive products.
A Nickel base alloy such as PENA-68, with addition of Tungsten Carbide (between 20% and 40% according to the needs). This provides an additional reinforcement against abrasion.
A Nickel base alloy with 80% of Tungsten Carbide. This make it extremely resistant to wear and corrosion. It is mainly used for processing ultra-polymers with high loads of glass and carbon fibres.