US2022178008A1PendingUtilityA1
Line speed dependent control of a furnace for heat treating aluminum alloy sheet
Assignee: ALVANCE ALUMINIUM DUFFEL BVPriority: Apr 23, 2019Filed: Apr 15, 2020Published: Jun 9, 2022
Est. expiryApr 23, 2039(~12.7 yrs left)· nominal 20-yr term from priority
C22F 1/002C21D 9/46C21D 1/26C22F 1/053C22F 1/047C21D 11/00C22F 1/04
28
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Claims
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
Claims
exact text as granted — not AI-modified1 . 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 (T PMT ) 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 v line,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 (v line,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 (v fan,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 (T zone,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 (v line,Set ), the fan speed set points (v fan,Set ), and the zone air temperature set point (T zone,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 v line,act and the line speed set point v line,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:
v line,act is the actual measured line speed, for example in m/min,
v line,Set is the line speed set point, for example in m/min,
v fan,act is the actual fan speed in rpm in the peak metal temperature zone,
x is between 0.6 and 0.95,
v fan,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,
T zone,act is the actual zone air temperature in the peak metal temperature zone,
T zone,Set is the zone air temperature set point in the peak metal temperature zone,
y is between 0 and 0.2.
2 . The method of claim 1 , wherein adjusting fan speed and furnace air temperature when the line speed is adjusted controls peak metal temperature in the furnace peak metal temperature zone within +/−5° C. of set target peak metal temperature (T PMT ).
3 . The method of claim 1 , wherein actual furnace air temperature is reduced relative to the furnace air temperature set point no more than 10° C.
4 . The method of claim 1 , which includes obtaining the at least one furnace air temperature measurement with at least one temperature sensor within the furnace.
5 . The method of claim 1 , wherein the sheet moves along the pathway at least three meters per minute.
6 . The method of claim 1 , wherein the sheet is at peak metal temperature for 1 second to 100 seconds.
7 . The method of claim 1 , comprising:
at least one fan speed controller connected to a sensor measuring the line speed and to the fans in the peak metal temperature zone, said fan speed controller controlling the fans to change respective fan speed from v fan,Set to v fan,act in the event of a change of v line,act to a value different from v line,Set ; at least one burner controller connected to the sensor measuring the line speed of the aluminum sheet; and at least one furnace air temperature controller connected to a temperature sensor measuring the temperature of the furnace atmosphere said furnace air temperature controller controlling the burners to change furnace air temperature from T zone,Set to T zone,act in the event of a change v line,act changing to a value different from v line,Set .
8 . The method of claim 1 , wherein the continuous furnace is heated by means of convective heating means.
9 . The method of claim 1 , wherein the peak metal temperature is 370° C. to 590° C.
10 . The method of claim 1 , wherein the aluminum alloy sheet is heat-treatable AA6000 aluminum alloy sheet and the set peak metal temperature (T PMT ) is in a range of 480° C. to 590° C.
11 . The method of claim 1 , wherein the aluminum alloy sheet is heat-treatable AA7000 aluminum alloy sheet and the set peak metal temperature (T PMT ) is in a range of 430° C. to 560° C.
12 . The method of claim 1 , wherein the aluminum alloy sheet is heat-treatable AA7000 aluminum alloy sheet and the set peak metal temperature (T PMT ) is in the range of 460° C. to 480° C.
13 . The method of claim 1 , wherein the method anneals a non-heat-treatable AA5000-series aluminum alloy sheet,
wherein continuously moving uncoiled non-heat-treatable AA5000-series aluminum alloy sheet moves in the direction of its length through the continuous heat-treatment furnace arranged to heat the moving aluminum sheet to peak metal temperature set peak metal temperature (T PMT ) in the range of 350° C. to 560° C., and wherein the moving aluminum sheet is rapidly cooled from T PMT to below about 150° C. on leaving the furnace.
14 . The method of claim 1 , comprising
wherein said taking measurements representative of heat transfer to the sheet as the sheet advances through the elongated heat treatment chamber comprises measuring line speed of the sheet through the elongated heat treatment chamber, measuring the fan speeds of fans above and below the moving sheet in each contiguous heat treatment zone and measuring the furnace air temperature in each contiguous heat treatment zone; comparing the measured fan speeds with a preset fan speed range in the form of specified values; comparing the measured furnace air temperature with a preset air temperature range in the form of specified values; providing a plurality of different independently-controllable burners at different positions along the pathway, providing a plurality of different independently-controllable fans above and below the moving aluminum sheet at different positions along the pathway; generating a real-time sheet temperature estimate along the pathway wherein the sheet temperature estimate is established as a function of the sheet line speed in the elongated heat treatment chamber, the furnace air temperature in each contiguous heat treatment zone, and the fan speed in each contiguous heat treatment zone; adjusting the sheet temperature estimate in response to a change in at least one of the sheet line speed, the furnace air temperature in at least one said contiguous heat treatment zone, and the fan speeds in at least one said contiguous heat treatment zone.
15 . The method of claim 14 , wherein the sheet temperature estimates are sheet surface temperature estimates.
16 . The method of claim 1 , wherein said taking measurements representative of heat transfer to the aluminum alloy sheet as the aluminum alloy sheet moves through the elongated heat treatment chamber, comprises from time to time taking measurements including speed of the aluminum alloy sheet through the elongated heat treatment chamber, speed of the fans above and below, and air temperature in each zone,
generating a real-time sheet temperature estimate along the path wherein the sheet temperature estimate is established as a function of speed of the aluminum alloy sheet through the elongated heat treatment chamber, speed of the fans above and below, and air temperature in each zone; wherein said generating the real-time sheet temperature estimate along the path comprises estimating the aluminum alloy sheet temperature in the peak metal temperature zone at the line speed set point v line,Set , and the fan speed set point v fan,Set , adjusting the sheet temperature estimate in response to a change in at least one of the sheet speed, speed of the fans above and below, and air temperature in each zone; comparing the sheet temperature estimate to a desired temperature distribution to determine any differences between the sheet temperature estimate and the desired temperature distribution, wherein the desired temperature distribution includes a plurality of temperature setpoints for the sheet along the pathway, each setpoint representing a target value; for each one of the burners and fans, regulating operation as a function of the differences with a closed-loop, feedback controller; estimating, in real-time, a sheet temperature profile along the pathway for the sheet based on the sheet temperature estimate and the length of the sheet, and visually displaying a real-time representation of the sheet temperature estimate and soak time.
17 . The method of claim 1 , wherein said taking measurements further comprises:
continuously measuring the speeds of the furnace fans above and below the aluminum alloy sheet in one or more additional zones of said contiguous zones, said additional zones being in addition to said peak metal temperature zone, wherein for each additional zone the fan speeds of the fans above and below the aluminum alloy sheet have respective fan speed set points (v fan,Set ), wherein the fan speed set point of each fan above the aluminum alloy sheet may be the same or different from the fan speed set point of each fan below the aluminum alloy sheet; continuously measuring the furnace air temperature in each additional zone, wherein the furnace air temperature in each additional zone has a respective zone air temperature set point (T zone,Set ); and optionally continuously measuring the surface temperature of the sheet, wherein during normal operation the actual measured line speed, measured fan speeds in each additional zone, and measured furnace air temperature in each additional zone simultaneously are respectively in the preset ranges for the line speed set point (v line,Set ), the fan speed set points (v fan,Set ), and the zone air temperature set point (T zone,Set ) in the additional zone; respectively changing the fan speeds and the furnace air temperature in each additional zone, in response to the actual measured line speed v line,act and the line speed set point v line,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:
v line,act is the actual measured line speed, for example in m/min,
v line,Set is the line speed set point, for example in m/min,
v fan,act is the actual fan speed in rpm in the additional zone,
x is between 0.6 and 0.95,
v fan,Set is the fan speed set point in rpm in the additional zone, wherein the set point of the fans above the moving sheet may be the same or different from the set point of the fans below the moving sheet,
T zone,act is the actual zone air temperature in the respective additional zone,
T zone,Set is the zone air temperature set point in the respective additional zone,
y is between 0 and 0.2.
18 . The method of claim 1 , wherein x is between 0.65 to 0.95 and y is between 0 and 0.1.
19 . The method of claim 18 , wherein x is between 0.75 to 0.95.
20 . The method of claim 17 , wherein y is between 0 and 0.1.Join the waitlist — get patent alerts
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