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Iserlohn / Rodengo Saiano, March 22, 2021

HybroHeat® furnace technology for aluminum extrusion lines

Combination of gas furnace and induction heating is cost-efficient and allows precise temperature setting of aluminum and light metal logs

In the field of aluminum extrusion, HybroHeat® furnace technology combines the advantages of cost-efficient preheating of log material in a gas furnace and precise temperature setting by means of induction technology. This new development is a result of a joint effort between IAS GmbH and OMAV S.p.A.. Since the end of September 2020, OMAV is part of SMS group as a wholly owned subsidiary.

The concept is based on proven technologies from both companies in which it joins efficient gas furnaces and saws from OMAV with high-performance induction plants from IAS in a single line. The advantages for the operator are, among others, lower investment cost resulting from a compact design and less operating costs achieved by reduced idle times.

Gas preheating for lower energy cost

In a HybroHeat® furnace, basic aluminum log heating takes place in a gas furnace developed by OMAV S.p.A. on the basis of the high-performance billet furnace HP7. It is characterized by high thermal efficiency of 75 percent and low average consumption of less than 18 Nm³ natural gas per ton of log material and it is therefore the market leader in this segment. This can be achieved particularly by a preheating zone where the logs are preheated by means of exhaust air of the combustion zone. “A preheat zone is provided on the entry side of the direct combustion zone equipped with a burner. The preheating system uses powerful fans to blow  outlet fumes of the combustion zone into the preheating zone for heating up the logs to 200 degrees Celsius. Besides, the fumes pass through a heat exchanger for preheating combustion air which is temperature-controlled and always achieves by PLC controlled, electronic valves an optimal air/gas ratio. The thermocouple for measuring the log temperature is designed in such a way that it is mounted at the top of the log and it is air-cooled in standby mode“, explains Massimo Marinelli, Managing Director at OMAV.

Moreover, in term of cost reduction, the rollers play an important role.  A long life up to 10 years is ensured by a special design with an external ball bearing support.

Induction heating for precise temperature setting

The final heating zone is realized by an induction coil following the combustion zone of the gas furnace almost seamlessly. Before the log is pushed to the fully-electric  operated saw arranged in the runout section and cut to extrusion length, a defined temperature profile is set in the induction furnace. After the cutting process an electrically driven cylinder pushes the remaining log back to the induction respectively gas furnace where the end of the log is again heated to extrusion temperature and provided with a taper.

In order to prevent rejects the saw is equipped with a buffer station for temporary reception of the log end, so that the logs can be processed completely – provided the  extrusion process allows the extrusion of a two-piece billet. The entire process is managed by sophisticated software and is executed fully automatically without manual interventions of the operator.

“For induction heating a coil developed by IAS GmbH is used reaching an efficiency of up to 70 percent due to its multilayered structure and the use of a copper profile particularly matched to the process. The entire coil length is divided into several zones depending on the billet length and which can be charged with power ranging from 0 to 100 percent. This enables a temperature profile setting over the length of the billet and thus creates the conditions for an isothermal extrusion process. In each zone, the billet temperature is monitored by means of thermocouple tips and the heating process is controlled by an inverter based on IGBT technology, so that temperature tolerances of < 3K are achieved,” explains Torsten Schäfer, Head of Sales at IAS.

The same technology is also applied for stand-alone inductive solutions. By using high power densities the required extrusion temperature is reached quickly. Apart from a friction-free transport of the billets for optimum surface and thus profile qualities, a high temperature accuracy and process reproducibility, this solution creates an environmentally friendly workplace for customer staff since no CO2 emissions arise.