ELECTROSLAG REMELTING OF METAL

1,246,676. Casting processes. TSENTRALNAYA LABORATORIA AVTOMATIKI. 8 Oct., 1968, No. 47641/68. Heading B3F. [Also in Divisions G2-G3] An electroslag remelting process is carried out in accordance with a predetermined programme which continuously specifies a predetermined resistance between the consumable electrode and the ingot and a predetermined ingot build-up rate, the process being automatically controlled so that the voltage and/or current between the electrode and ingot is continuously varied to obtain the predetermined resistance and to simultaneously vary the heat within the slag bath to cause the ingot build-up rate to approach the predetermined value. In the described embodiment a programme control unit 1, containing an optimum programme of experimentally-compiled values of resistance and build-up rate relating to the mould size, type of electrode and slag grade, supplies reference signals to:- (1) The setting unit 3 of a voltage regulator 2 which controls the transformer power supply 12 to maintain the voltage across the mould at a predetermined value. (2) The setting unit 5 of a current regulator 4 which controls an electrode-moving mechanism 7 to maintain the current through the mould at a predetermined value. (3) A counting comparison element 15 which compares the signal from an electrode feed-rate senser 10 with the signal from unit 1. (4) A pulsed timer 13 which sets a predetermined time period for the element 15 to compare the actual advance of the electrode 8 during this period with the predetermined value from unit 1. The element 15 controls a command correction unit 14 whose output signals are passed to the setting units 3, 5 during the remelting stage of the process. Prior to this, when the slag 18 in the mould 11 is being diluted and heated, the voltage and current are maintained at values set by the unit 1 through operation of regulators 2, 4. During remelting a periodic comparison is made by the element 15 and the unit 14 alters the settings of units 3, 5 to gradually change the rate of heat generation in the mould 11 and hence the rate of electrode melting, whilst maintaining the mould resistance at the predetermined value. Thus the remelting stage is divided into a number of periods during each of which the voltage and current are varied in accordance with the comparison made by element 15 at the end of the previous period, so that the actual electrode feed rate may be kept nearly equal to the predetermined rate set by the unit 1.