Line speed dependent control of a furnace for heat treating aluminum alloy sheet
OwnerJohan Petrus Mariette Guido ARRAS, Jason P. LODZIK +2inventors
InventorsJohan Petrus Mariette Guido ARRAS, Jason P. LODZIK, Jamaal D. HARRIS, Christopher ELWELL
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Abstract
A method for controlling continuous heat treating and annealing of heat-treatable and non-heat-treatable aluminum alloy sheet at final thickness continuously moving in a floating state horizontally through a continuous convection floating furnace arranged to heat the moving aluminum sheet to a set peak metal temperature. The controlling including controlling fan speeds and furnace air temperature to accommodate variations in line speed of the aluminum alloy sheet continuously moving in the floating state horizontally through the continuous convection floating furnace
Claims20
A method for continuously heating aluminum alloy sheet at final thickness in a continuous heat-treating furnace having an entry section and an exit section, wherein the heat-treating furnace is a continuous convection floating furnace, comprising
- continuously horizontally moving uncoiled aluminum alloy sheet in a floating state in a path along a direction of its length through a plurality of contiguous heat treatment zones of an elongated heat treatment chamber of the continuous heat-treating furnace arranged to heat the moving aluminum sheet to a set peak metal temperature (TPMT) in the temperature range of 350° C. to 590° C.;
- wherein the contiguous heat treatment zones have independently controllable convection heaters along the path for heating the aluminum alloy sheet and independently controllable fans blowing above and below the aluminum alloy sheet along the path for guiding the aluminum alloy sheet along the path as the aluminum alloy sheet horizontally moves through the elongated heat treatment chamber,
- wherein at least one said contiguous heat treatment zone is a peak metal temperature zone which has a target aluminum alloy sheet temperature which is the peak metal temperature of the aluminum alloy sheet in the elongated heat treatment chamber;
- taking measurements representative of heat transfer to the aluminum alloy sheet as the aluminum alloy sheet moves through the elongated heat treatment chamber, the measurements including speed of the aluminum alloy sheet through the elongated heat treatment chamber, speed of the fans blowing above and below the aluminum alloy sheet, and furnace air temperature, and optionally surface temperature of the sheet,
- wherein said taking measurements comprises:
- continuously measuring the line speed of horizontal movement of the aluminum alloy sheet through the furnace and generating a speed signal proportional to the actual measured line speed vline,act of the aluminum alloy sheet through the furnace, wherein the line speed of the aluminum alloy sheet through the furnace has at a line speed set point (vline,Set),
- continuously measuring the speeds of the furnace fans above and below the aluminum alloy sheet in said peak metal temperature zone, wherein the fan speeds of the fans above and below the aluminum alloy sheet have respective fan speed set points (vfan,Set), wherein the fan speed set point of the fans above the aluminum alloy sheet may be the same or different from the fan speed set point of the fans below the aluminum alloy sheet;
- continuously measuring the furnace air temperature in said peak metal temperature zone, wherein the furnace air temperature in said peak metal temperature zone has a zone air temperature set point (Tzone,Set);
- and
- optionally continuously measuring the surface temperature of the sheet,
- wherein during normal operation the actual measured line speed, measured fan speeds in said peak metal temperature zone, and measured furnace air temperature in said peak metal temperature zone simultaneously are respectively in the preset ranges for the line speed set point (vline,Set), the fan speed set points (vfan,Set), and the zone air temperature set point (Tzone,Set) in said peak metal temperature zone;
- changing the fan speeds and the furnace air temperature in said peak metal temperature zone, in response to the actual measured line speed vline,act and the line speed set point vline,Set according to equation (I) and equation (II):
- v
- fan
- ,
- act
- =
- (
- v
- line
- ,
- act
- v
- line
- ,
- Set
- )
- x
- ×
- v
- fan
- ,
- Set
- (
- I
- )
- T
- zone
- ,
- act
- =
- (
- v
- line
- ,
- act
- v
- line
- ,
- Set
- )
- y
- ×
- T
- zone
- ,
- Set
- (
- II
- )
- wherein:
- vline,act is the actual measured line speed, for example in m/min,
- vline,Set is the line speed set point, for example in m/min,
- vfan,act is the actual fan speed in rpm in the peak metal temperature zone,
- x is between 0.6 and 0.95,
- vfan,Set is the fan speed set point in rpm in the peak metal temperature zone, wherein the set point of each fan above the moving sheet may be the same or different from the set point of each fan below the moving sheet,
- Tzone,act is the actual zone air temperature in the peak metal temperature zone,
- Tzone,Set is the zone air temperature set point in the peak metal temperature zone,
- y is between 0 and 0.2.
Dependencies are inferred from the claim text.