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Energy savings by application of electromagnetic field in production of al-alloy billets by dc casting method

Espal's goal is to achieve significant energy savings during the production of al-alloys billets and ingots by use of dc casting method in combination with electromagnetic field while improving the technological properties of alloys obtained by modifying their structure.

More than 80 % of the aluminium (Al) used worldwide in extruded sections are aluminium alloys. The production of billets for aluminium extrusion requires a certain degree of homogeneity. In DC casting process (standard semi-continuous casting process) there are segregated particles inside the cast structure of the billets. The billets cast with ECT (Electromagnetic Casting Technology) have smooth surface, the structure is very fine and amazing homogeneity with small globular grain without boundary segregation. Also ECT eliminates macro porosity and has good influence on grain refining. When alternating current flows through a coil, a varying electromagnetic field is generated. The varying electro-magnetic field induces eddy current in the conducting materials. In the Electromagnetic Casting process, the alternating current generates time varying electromagnetic field in the melt and billets. The forces caused by the interaction of the induced current and the electromagnetic field resulting flow in the melt and potential forces which is balanced by static pressure of the melt. The consequence of this is the formation of a convex surface (meniscus) and decrease in the contacting pressure on the mould (soft contact). This results in good surface. Application of varying electro-magnetic field on casting Al billets and ingots significantly improves the microstructure, surface quality and decrease grain boundary segregations. The ring shaped mould is made of an Al alloy. A graphite ring is embedded in the top side of the Al -alloy mould. The electromagnetic field is applied through the induction coil with the number of ampere turns 18,000 At and frequency from 1 to 100Hz. Compared with billets cast in the standard casting process, microstructure of billets cast in electromagnetic field is fine and uniform so there is no need for the long heat treatment. Accordingly, energy savings are significant and modification operations are reduced to minimum. Therefore advantages are as follows: * Smooth surface. Thus the need for the surface machining is reduced to minimum. * The structure is very fine with very good homogeneity and small globular grain. * Segregation zones absence. * ECT eliminates macro porosity and has good influence on grain refining. * All these points indicate homogeneity within structure and absence of segregation, so extrusion without heat treatment is possible. * Better structure induces better mechanical properties of the casting. * By eliminating long homogenous heating treatment energy savings is significant.
Acronym: 
ESPAL
Project ID: 
6 735
Start date: 
02-04-2011
Project Duration: 
27months
Project costs: 
600 000.00€
Technological Area: 
Process optimisation, waste heat utilisation
Market Area: 
Steel / Metalwork

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