ABB Metallurgy, Inc.

Melting Furnaces

In terms of induction furnace design at ABB, the past is truly a prologue to both the present and the future.

When ABB pioneered modular furnace packaging in the 1960s, it not only set a universal trend in furnace design that continues today, but created the ideal platform for subsequent breakthroughs in solid-state power electronics, component miniaturization and microprocessor control.

In the totally modular lineup of ABB coreless induction melters, power ratings and densities continue to escalate while the physical systems become steadily more compact.

A packaged system now being readied for shipment to a major domestic car company will put an unprecedented power of 10,000 kW on a 20-ton furnace. By a wide margin, it is the most powerful medium-frequency power supply yet built, and doubles the usual power rating for this size furnace.

In ABB furnaces of all sizes, electronic control and automation grows progressively more comprehensive and user-friendly. State of the art in this trend is represented by the ABB Micromatic |TM~, a fully digital small melting system just introduced by ABB in ratings up to 1000 kW. In the Micromatic, all measurement, control, protection and display functions are performed by an integral computer module. The computer is accessed by means of a liquid crystal display and a touch-sensitive keypad, literally putting monitoring and command of the system at the fingertips of the furnace operator.

With its rationalized circuitry and minimum number of components, the Micromatic combines reduced first cost with great flexibility, savings in time and energy, and vastly simplified operation, troubleshooting and maintenance.

The seeming "magic" that can be worked with digital electronics is typified by the new ABB Multimatic |TM~ furnace power supply system. Based on an elaboration of the same programmable computer module system that controls the Micromatic melter, the Multimatic solves a longstanding problem in meltshop operations, with a resulting boost in efficiency.

An inherent limitation in connecting multiple furnaces to a common power supply is reduced utilization, which imposes penalties in both production rate and efficiency. For example, where the objective is a continuous metal supply to the casting lines, the typical arrangement is "butterfly" batch melting. Two furnaces and a single power supply are utilized, with the furnaces alternating in melting and pouring modes. In the past, it was necessary to turn off the power periodically on the melting unit and switch it mechanically to the pouring furnace to maintain temperature.

With the Multimatic, synchronous melting and holding at temperature are performed without power switching. Power is applied to each furnace in the required amounts, simultaneously and continuously. Holding power at the appropriate level is applied to the furnace in tapping mode, while simultaneously the full balance of the available power is applied to the second furnace for melting. Power utilization is maintained at 100% at all times, resulting in increased production from the same power rating and substantial cost savings.

The flexibility of the Multimatic system opens up other options in meltshop operations. For example, metal can be held overnight without switching power back and forth between furnaces. Melting can be carried out simultaneously in two furnaces, with the power level in each furnace matched to production needs.

Operation of the system is simplicity itself: the operator turns two power setpoint knobs, assigning each furnace the desired power level. Total power input, of course, is matched to the rated power. There is also a demand-limiting feature which makes it possible to set the total input at a level below the rated power of the system. Multimatic systems come in a complete range of furnace sizes and power ratings from 100-10,000 kW.

Taking computer control to its full potential is the ABB Melt Processor, available on all ABB furnaces incorporating PLCs, either new installations or as a retrofit in existing plants.

Meltshop productivity, quality and cost management are all augmented by the Melt Processor. Automatically, the control system cycles the furnace through sintering, cold starting, melting sequences for various alloys, temperature monitoring, fault detection and energy consumption tabulation.

A popular option today is to set the furnace on load cells whose output data are fed to the Melt Processor. In this way, the system can provide continuous calculated temperature readout and control. An optional chemistry program calculates and monitors the additions needed to keep bath chemistry on target.

Furnace utilization can be further increased by interfacing the Melt Processor with support systems such as charge makeup or hot metal delivery. Programming is available to integrate all melt department cost and functions into a total management information system. All operating data are displayed graphically on a color monitor and can be fed to a printer. Using a modem, the Melt Processor can connect with the ABB furnace service center for realtime status analysis.

ABB Metallurgy, Inc., 1460 Livingston Ave., North Brunswick, New Jersey 08902; 908/932-6134; fax [phone].