# US 5,331,661 A · Method and apparatus for controlling electroslag remelting

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- Number: US 5,331,661 A
- Document ID: US5331661A
- Status: Granted
- Kind: A
- Application number: 07/843,870
- Filed: 1992-02-27
- Granted: 1994-07-19
- Earliest claimed: 1992-02-27
- Assignees: Sandia Corporation
- Inventors: Michael C. Maguire; Frank J. Zanner; Brian K. Damkroger; Mark E. Miszkiel; Eugene A. Aronson
- Web page: https://patentgrep.com/patent/US5331661A

## CPC

- H05B 7/148: Automatic control of power (electrode feeding arrangements H05B7/109; automatic feeding of electrodes for spot or seam welding or cutting B23K9/12; disposition of electrodes in or on furnaces F27D11/10; control of position in general G05D3/00; regulating electric characteristics of arcs in general G05F1/02; regulating electric power in general G05F1/66)
- Y02P 10/25: Process efficiency
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

Method and apparatus for controlling electrode immersion depth in an electroslag remelting furnace. The phase difference of the alternating current circuit established in the furnace is calculated in real time and employed to more accurately control immersion depth than possible with voltage-swing systems.

## Claims

### Claim 1

A method for controlling electrode immersion depth in a slag pool of an electrode melting furnace, the method comprising the steps of:
a) immersing the electrode in the slag pool;
b) passing a current through the electrode and the slag pool;
c) measuring at time intervals values of voltage and current to obtain power spectrum data for the current;
d) using a control computer means to obtain a measure of phase difference based from imaginary and real components of said power spectrum data; and
e) adjusting the electrode immersion depth in the slag pool according to the measured phase difference.

### Claim 2 (depends on 1)

The method of claim 1 wherein the obtaining step d) comprises obtaining a measure of the phase difference from a selected frequency of the power spectrum data.

### Claim 3 (depends on 1)

The method of claim 1 wherein the adjusting step e) comprises comparing the measure of phase difference to a predetermined phase difference.

### Claim 4 (depends on 3)

The method of claim 3 additionally comprising the step of adjusting the predetermined phase difference at predetermined time intervals.

### Claim 5 (depends on 1)

The method of claim 1 wherein the adjusting step e) comprises determining an adjustment by an adaptive bang-bang algorithm.

### Claim 6 (depends on 1)

The method of claim 1 wherein the adjusting step e) comprises adjusting a voltage set point signal.

### Claim 7 (depends on 1)

The method of claim 1 wherein the adjusting step e) comprises adjusting an electrode drive velocity signal.

### Claim 8 (depends on 1)

The method of claim 1 wherein the adjusting step e) comprises maintaining the electrode immersion depth at a depth greater than 25 mm.

### Claim 9

An apparatus for controlling immersion depth of an electrode in a slag pool of an electrode melting furnace, the apparatus comprising:
means for measuring at time intervals values of voltage and current to obtain power spectrum data of an electrical circuit through the electrode and the slag pool;
control computer means for obtaining a measure of phase difference based from imaginary and real components of spectrum data; and
means for adjusting the electrode immersion depth in the slag pool according to the measure of phase difference.

### Claim 10 (depends on 9)

The apparatus of claim 9 wherein said means for obtaining a measure of phase difference comprises means for obtaining a measure of phase difference from a selected frequency of the power spectrum data.

### Claim 11 (depends on 9)

The apparatus of claim 9 wherein said adjusting means comprises means for comparing said measure of phase difference to a predetermined phase difference.

### Claim 12 (depends on 11)

The apparatus of claim 11 wherein said adjusting means additionally comprises means for adjusting said predetermined phase difference at predetermined time intervals.

### Claim 13 (depends on 9)

The apparatus of claim 9 wherein said adjusting means comprises means for determining an adjustment by an adaptive bang-bang algorithm.

### Claim 14 (depends on 9)

The apparatus of claim 9 wherein said adjusting means comprises means for adjusting a voltage set point signal.

### Claim 15 (depends on 9)

The apparatus of claim 9 wherein said adjusting means comprises means for adjusting an electrode drive velocity signal.

### Claim 16 (depends on 9)

The apparatus of claim 9 wherein said adjusting means comprises means for maintaining the electrode immersion depth at a depth greater than 25 mm.

### Claim 17 (depends on 9)

The apparatus of claim 9 wherein said adjusting means comprises software.

### Claim 18 (depends on 9)

The apparatus of claim 9 wherein said adjusting means comprises firmware.

### Claim 19 (depends on 9)

The apparatus of claim 9 wherein said adjusting means comprises a central processing unit.

### Claim 20 (depends on 9)

The apparatus of claim 9 wherein said adjusting means is operably connected to an electrode melting furnace control panel.