VAR - Vacuum Arc Remelting

Pioneers in VAR Technology

Background

Consarc is well known to primary producers of speciality steel, superalloys, and reactive metals. We pioneered commercial ingot production using automated Vacuum Arc Remelting (VAR) furnaces. We were the first to apply load cell weighing of electrodes to improve process control. We developed coaxial furnace designs to minimise uncontrolled stirring. And we fully computerised the controls to optimise reproducibility and ease of operation. Users of Consarc VAR furnaces get proven process technology, state-of-the-art control and fully computerised controls to optimise reproducibility and ease of operation from the industry's most innovative and experienced resource.

Furnace Configurations

Consarc essentially makes two types of VAR furnaces. The first is for speciality steels and superalloys and the second is reactive furnaces for titanium and other highly reactive metals. Both types are available in many sizes and production capacities to around 30,000 kg ingot weights.

The VAR Furnace Process Cycle

Materials to be melted are loaded into the furnace. For speciality steels and superalloys, an electrode is used, previously cast in air or vacuum. For primary reactive metals like titanium, it is material fabricated from compacted sponge and/or scrap. Two major mechanical assemblies combine to form the vacuum vessel in which melting occurs - the movable furnace head and the fixed melt station.

The movable furnace head is the upper section of the vessel. An integral, highly sophisticated ram drive assembly supports and controls the movement of the electrode. The water-cooled ram extends through a vacuum seal in the head; the electrode clamps to its lower end thus becoming the cathode of the arc melting operation.

The fixed melt station, the lower half of the vacuum vessel, consists of a removable copper crucible that is placed into a fixed steel water jacket and guide. Design and construction of the crucible are critical to the successful solidification of the restructured metal ingot.

Once the furnace head with electrode is lowered and secured onto the melt station, a vacuum is established. A controlled, high dc current is applied to the electrode (cathode) and arcing between it and the ingot (anode) remelts the electrode material at a pre-determined rate . The entire melting cycle and all the key operating parameters (Current, Voltage , Melt Rate and Arc Length) are automatically monitored and controlled to a pre-defined melt recipe from start to finish.

Advantages of Consarc VAR furnaces

The Consarc VAR process overcomes serious problems that have been historically associated with conventional VAR operations. Problems such as strong magnetic fields in the electrode melt area that caused uncontrolled metal stirring, uneven solidification, and alloy segregation. Imprecise positioning of the electrode that compromised ingot reproducibility and in the case of titanium, system safety. Consarc has developed and implemented solutions to all of these problems. Solutions that have proven their worth through years of field use.

Ease of operation through full automation:

Consarc has engineered PC / PLC based control systems of such sophistication that for most alloys our VAR process all but run themselves with the operator initiatingteh start of the melt via the PC control screen In fact, continuous operator attendance is not required during the melt cycle. Built-in failsafes and system interlocks provide security of operation.

Melt uniformity by coaxial design:

After pioneering, then innovating, VAR coaxiality, Consarc continues to offer the world's most advanced designs. Our furnaces provide coaxial current paths that close the electrical circuit for the cathode-anode current. Returning the current coaxially prevents the creation of stray magnetic fields that disturb the ingot solidification process.

Quality control by X-Y axis electrode positioning:

To achieve and maintain centring of the electrode within the melt chamber, Consarc uses remote TV viewing and adjustable electrode positioning. The resulting precision has a positive effect on ingot quality. In the case of reactive metals like titanium, it also ensures vastly safer processing.

Consistent yield from electrode to ingot through load cell based hot topping:

Reproducibility is enhanced by this process, which Consarc incorporates into the end of the melt cycle. Hot topping, like the entire VAR process, is fully automated, eliminating the need for operator intervention.

Precision melt control via load cells:

These high accuracy sensors continuously monitor electrode weight throughout the melting process. Automated system control uses the data to compute the melt rate, compare it with the desired rate and adjust the power input to maintain optimum melting conditions.

Reliability assured by proprietary power supply (Reactor or Thyristor based):

Consarc are the only supplier of VAR furnaces that design and produce our own power supplies to meet the exact requirements of the specific melting application The Consarc VAR power source is a rugged, water-cooled, variable reactance transformer or thyristor based DC power supply. These long-life units take up very little floor space and have exceptional reliability and low operating/maintenance costs.