Apparatus to Control the Total Energy Flux into the Top Ingot Surface During Vacuum Arc Remelting Processes

摘要

A Vacuum Arc Remelting controller apparatus wherein process control is accomplished primarily through control of pool power. Pool power being defined as the total energy flux into a top ingot surface of the VAR ingot. The controller apparatus of the present invention comprises a controller computer that transmits commands to the host furnance through an ethernet connection.

主权项

1. An apparatus for controlling pool power, pool power being defined as the total energy flux into a top ingot surface during vacuum arc remelting processes, the apparatus comprising:
a. a remelting furnace comprising a movable electrode, an electrode drive, and a programmable logic controller; b. an electrical current supply that supplies current to the electrode; c. an ingot pool located beneath the electrode, the ingot pool comprising molten metal from the electrode; d. a controller computer that communicates with the programmable logic controller using a communication protocol comprising an ethernet connection and which sends two separate and distinct controller signals over the connection from two different controllers programmed into the computer; e. a first controller that adjusts current supplied to the remelting furnace based upon a predetermined pool power reference value, the pool power reference value being defined as the sum of a total melt power entering the ingot pool as enthalpy contained in molten metal dripping from the melting electrode plus a fraction, ε, of an electrical arc power, the fraction consisting of the arc power collected by the ingot pool surface, wherein the first controller computer employs the following equation to calculate the adjusted current:I=-VCF2(RI+RGG)+(VCF2(RI+RGG))2+Ppool+αrCSΔAehsupΔ(μCSphsuphm+ɛ)(RI+RGG), wherein Ppool,ref is a pool power reference setpoint, hsup is a volume specific enthalpy at superheat temperature, VCF is a cathode fall voltage, RI is a VAR circuit resistance less an electrode gap resistance, RG is an experimentally determined electrode gap resistance parameter, G is an electrode gap, Ae is an electrode cross-sectional area, αr is a room temperature thermal diffusivity, CSΔ and CSp are material dependent constants, μ is a process efficiency, Δ is an electrode thermal boundary layer, and hm is a volume specific enthalpy at melt temperature; and f. a second controller that adjusts the remelting furnace's electrode drive speed based upon a predetermined electrode gap reference value, Gref, and a predetermined pool power reference value, Ppool,ref, wherein the adjusted electrode drive speed is calculated from the following equation:fG=ahsupAe{Ppool,ref-ɛ[(VCF)I+(RI+RGG)I2]} wherein α is a fill ratio parameter, hsup is a volume specific enthalpy at superheat temperature, ε is an arc power fraction to the pool surface, VCF is a cathode fall voltage, RI is a VAR circuit resistance less an electrode gap resistance, RG is an experimentally determined electrode gap resistance parameter, G is an electrode gap, Ae is an electrode cross-sectional area, and I is a process current.