GB1303542A - - Google Patents

Abstract

1303542 Casting processes LEYBOLDHERAEUS-VERWALTUNG GmbH 3 Dec 1970 [4 Dec 1969] 57587/70 Heading B3F [Also in Divisions G3 and H5] A consumable electrode 1 of electroslag remelting apparatus is maintained at a desired depth in the slag layer 16 corresponding to optimum operation of the process by sensing the fluctuations in voltage or current which are superimposed on the fundamental voltage across br the fundamental current through the slag layer, comparing a signal representative of these fluctuations with a reference signal representative of the desired depth and using the error signal so obtained to control the driving motor 11 of the electrode adjusting means 3, 5, 6. In the described embodiment the A.C. voltage across supply loads 21, 22 is taken to be representative of the voltage across the slag layer and is applied to a circuit comprising members 27... 30 to produce a smoothed rectified voltage free from supply harmonics but including the fluctuations to be sensed. Application of this voltage to members 32, 33 removes the D.C. component and produces across a resistor 34 an A.C. voltage representative of the fluctuations, which voltage is rectified by a diode 35. The resultant voltage is applied to an integrating circuit 37, 38, 39 whose output is applied to a resistor 40 for comparision with a reference voltage U # applied to resistor 43. The error signal developed across resistor 44 is applied to a regulator 47 which controls the driving motor 11 to vary the feed speed of the electrode 1 or, in extreme cases, to reverse the direction of feed. A current transformer 26 may be used if the current through the slag layer is to be the control parameter. Fig. 3 shows the fluctuations for the electrode (a) insufficiently immersed, (b) correctly immersed and (c) over-immersed, these fluctuations appearing across capacitor 33 and having an amplitude and frequency dependent on fixed parameters such as construction and size of the furnace, the nature of the slag and electrode 1 and the depth of immersion. A signal representative of these fluctuations may be obtained by integrating the whole waveform or positive or negative portions thereof, by counting positive and/or negative pulses or only pulses above a predetermined amplitude, in which case limiters may be employed in the control circuit. Application of the invention to D.C.-supplied electoslag apparatus is envisaged.