On Wednesday April 10, the new VAR furnace was inaugurated in the presence of government representatives, elected officials, partners from the Auvergne-Rhône-Alpes region and employees. After two and a half years of work, the Ugine Framatome site (Fuel BU) is now equipped with an additional VAR (vacuum arc remelting) furnace and a new control cabin, allowing various site alloys to be melted using state-of-the art equipment.
The VAR furnace is at the heart of the industrial plan for the Ugine Framatome site. It transforms zirconium sponge into semi-finished zirconium and titanium alloy products, such as billets, forged bars and extruded blanks, among others. The completion of this new VAR furnace and the new control building represented a major test, with significant challenges for the site and its employees.
This industrial challenge, like any large-scale project, mobilized a dedicated team of 11 people, who worked full time on the project for more than two and a half years. Covering a range of highly varied disciplines, from civil engineering to control PLC programming, they demonstrated their expertise and commitment to the project. Most team members came from the Ugine site originally, and they contributed to all the stages throughout the project, from design right up to equipment installation, strengthening their own expertise and making the project a success. Regular discussions with other industrial sites, as well as the supervisory authorities, helped improve certain key issues for the project, such as occupational and nuclear safety, and the completion deadlines.
During these two and a half years, part of the Ugine site has had to adapt to the work as it progressed, with ongoing production continuing alongside the installation of the new furnace and building. Managing the teams and subcontractors called for strict adherence to the schedule, while the physical challenges included dealing with 208 m3 of concrete, 11.5 km of cables, 800 m of pipework and a weight of 45 metric tons – these figures show the scope of this vast project, as well as the types of challenges the teams faced.
The next phase of the project is now starting, with the lengthy qualification process for the equipment to allow the production of our various alloys in line with very strict standards of industrial safety and quality. The incorporation of operating experience feedback from more than 50 years of operating melting furnaces has helped us obtain equipment at the cutting edge of this field, and the first tests have been completed successfully.
FOCUS ON THE VAR FURNACE
The VAR (vacuum arc remelting) furnace comprises a removable cover resting on a water-cooled copper crucible connected to the positive pole, or anode, of an electrical power supply.
The negative pole, or cathode, is connected to the ram holding the electrode. This moves vertically in and out of the furnace via a “dynamic” (or sliding) vacuum seal. The power supply is a high current rectifier (to obtain a high-intensity direct current).
The arc is struck between the crucible base and the bottom of the electrode. The energy dissipated in this way by the arc causes the electrode to melt and then drip into the crucible. As the electrode is consumed, the “liquid” rises in the crucible and the ram gradually adjusts the height of the electrode using an electrical or hydraulic system, maintaining a constant arc length. This results in the gradual formation of an ingot, which solidifies as it cools in the copper crucible.
This type of furnace is known as a “consumable electrode” or CE furnace.
The diagrams below give a detail view of a VAR furnace and the arc zone during melting.