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US 10,422,584 B2Granted
Apparatus to control the total energy flux into the top ingot surface during vacuum arc remelting processes
AssigneeSpecialty Metals Processing Consortium
InventorsRodney L. Williamson, David K. Melgaard, Joseph J. Beaman
Life of this patent
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Abstract
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 furnace through an ethernet connection.
Claims5
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, the programmable logic controller being a digital hardware device that sends current and drive speed commands to the furnace;
- 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 pool power control 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 a first controller and a second controller programmed into the computer;
- e. the first controller that adjusts the current supplied to the remelting furnace based upon a predetermined pool power reference value by sending new current commands to the programmable logic controller, 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 comprising the arc power collected by the ingot pool surface, wherein the first controller employs the following equation to calculate the adjusted current:
- f
- I
- =
- -
- (
- V
- CF
- +
- 〈
- V
- ^
- b
- 〉
- )
- 2
-
- (
- R
- I
- +
- R
- G
-
- 〈
- G
- ^
- 〉
- )
- +
- (
- (
- V
- CF
- +
- 〈
- V
- ^
- b
- 〉
- )
- 2
-
- (
- R
- I
- +
- R
- G
-
- 〈
- G
- ^
- 〉
- )
- )
- 2
- +
- 〈
- P
- pool
- ,
- ref
- 〉
- +
- α
- r
-
- C
- S
-
-
- Δ
-
- A
- e
-
- h
- sup
- 〈
- Δ
- ^
- 〉
- (
- 〈
- μ
- ^
- 〉
-
- C
- Sp
-
- h
- sup
- h
- m
- +
- ɛ
- )
-
- (
- R
- I
- +
- R
- G
-
- 〈
- G
- ^
- 〉
- )
- ,
- wherein Ppool is a pool power reference setpoint, 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, ar 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, Vb is a voltage bias, a circumflex over a variable indicates that it is an estimated value supplied by a nonlinear remelting estimator, and the angular brackets indicate variables supplied to the equation as opposed to constants, and
- f. the 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, by sending electrode drive speed commands to the programmable logic controller, wherein the adjusted electrode drive speed is calculated from the following equation:
- f
- G
- =
- a
- h
- sup
-
- A
- e
-
- {
- 〈
- P
- pool
- ,
- ref
- 〉
- -
- ɛ
-
- [
- (
- V
- CF
- +
- 〈
- V
- ^
- b
- 〉
- )
-
- I
- C
- +
- (
- R
- I
- +
- R
- G
-
- 〈
- G
- ^
- 〉
- )
-
- I
- 2
- ]
- }
- wherein a 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, Vb is a bias 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, I is a process current, a circumflex over a variable indicates that it is an estimated value supplied by a nonlinear remelting estimator, and the angular brackets indicate variables supplied to the equation as opposed to constants.
169 more elements
Dependencies are inferred from the claim text.