CA1079064A - Production of metal strip - Google Patents
Production of metal stripInfo
- Publication number
- CA1079064A CA1079064A CA285,688A CA285688A CA1079064A CA 1079064 A CA1079064 A CA 1079064A CA 285688 A CA285688 A CA 285688A CA 1079064 A CA1079064 A CA 1079064A
- Authority
- CA
- Canada
- Prior art keywords
- strip
- support surface
- entry
- angle
- section
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
- C21D9/54—Furnaces for treating strips or wire
- C21D9/56—Continuous furnaces for strip or wire
- C21D9/63—Continuous furnaces for strip or wire the strip being supported by a cushion of gas
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/18—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by using pressure rollers
Abstract
ABSTRACT OF THE DISCLOSURE
A floatation table for transporting strip material towards a sinter furnace is provided with a downwardly inclined entry section and an exit section inclined at an angle to the horizontal less than that of the entry section but greater than the angle of friction of the strip which is to travel over the strip support surface. Sensors are positioned at or adjacent the transition between the entry and exit sections of the table to sense the proximity of the strip to the surface of the table.
The speed at which the strip is transported to the table or into the furnace is controlled in response to the sensed proximity.
A floatation table for transporting strip material towards a sinter furnace is provided with a downwardly inclined entry section and an exit section inclined at an angle to the horizontal less than that of the entry section but greater than the angle of friction of the strip which is to travel over the strip support surface. Sensors are positioned at or adjacent the transition between the entry and exit sections of the table to sense the proximity of the strip to the surface of the table.
The speed at which the strip is transported to the table or into the furnace is controlled in response to the sensed proximity.
Description
This invention relates to the continuous production of metal strip or sheet material (hereinaiter reierred to simply as strip) and relates especially to transporting green strip produced by the roll compaction oi metal or ore powder from a compaction mill to a sinter iurnace.
In Canadian Patent No 1013180 there is described and claimed a method and apparatus for the continuous produ~tion of metal strip in which compacted powder in the iorm oi green strip is ied to a sinter ~urnace and is supported by a gaseous cushion as it is transported through the iurnace, the strip transport being controlled to perm~t the strip to shrink linearly as it passes through the iurn~ce.
In order to minimise the tensile stress imposed on the green strip and thereby to permlt the strip to shrink linearly as it passes through the iurnace, it is necessary to ensure that as the strip enters the iurnace it is isolated, so iar as is practicable, ~rom tensile stresses present in the strip upstream o~ the iurnace, and that lt is transported to the iurnace in a substantlally stress ~ree condition.
I It is also necessary to provide within the strip ¦ length a loop in which a sui~icient length o~ strip can be stored to provide a means o~ accommodating any l 25 temporary mismatch between the speeds at which the strip ¦ is supplled to and withdrawn irom the iurnace. Such a I mismatch would occur, ~or example, during changes i~ line speed.
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1~)79064 According to the present invention in one aspect, there is provided apparatus for transporting strip materials comprises a floatation table formed with a strip support s~r~ace having in the intended direction o~ travel of strip over the table surface a downwardly inclined entry section and an exit section inclined at an angle to the horizontal less than that of the entry section but greater than the angle of friction of the strip which is to travel over the strip support sur~ace, means being provided in the vicinity of the transition between the entry and exit sections o~ the support surface for senslng the proximity of or changes ln the proximity of strip passing over the table to said support surface. By 'angle o~ iriction' is meant the angle oi' - inclination at which the strip ~ust slides down the support surface under its own weight.
According to the present invention in a further aspect,apparatus ~or transporting metal strip to and through a sinter furnace comprises means for guiding the strip downwardly on to the support suri'ace oi' a . 20 iloatation table ~ormed, in the intended direction of strip over the table, with downwardly inclined entry anA exit sections oi dii'~ering ~lope, the exit section being inclined at an angle to the horizontal less than I that o$ the entry section, but greater than the angle ¦25 of friction of strip travelling over its support surface, : -meaDs ~or seDsing the proximlty o~ tho strlp to the _ 2 .
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9~:)64 support suriace as the strip passes between the entry section and the exit section o~ the table, means ior propelling the strip through the sinter iurnace and means ior controlling the strip propelling means in r~ dependence upon the sensed proximity to maintain the tensile stress imposed in the strip entering the furnace minimal.
According to the present invention in a still further aspect, there is provided a method oi transporting strip to a ~urnace through which it is propelled by a pair oi pinch rolls positioned downstream of the iurnace, the method comprising the steps oi transporting the strip to the iurnace over the support surface oi a , downwardly inclined iloatation table formed with an ;, ~5 entry section and an exit section inclined at an angle the horizontal less than that oi the entry section but greater than the angle oi iriction of strip travelling over its suriace, sensing the proximity oi the strip to the support suriace oi the iloatation table as it ~ passes irom the table entry section to the table exit section and controlling the rate at which strip approaches the entry section oi the iloatation table in ¦ dependence upon the sensed proximity to minimise the .1 tensile stiess imposed in the strip as it enters the . 25 i'urnace.
. In one embodiment o~ the invention ior transporting green strip produced by roll compacting metal powder . continuously to a sinter iurnacej the entry section 3 _ ' .
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o~ the support suriace of the iloatation table is inclined at an angle oi between 50 and 80 to the horizontal and the exit section is inclined at an ang~e o~ between 2 and 15 to the horlzontal. In a pre~erred embodiment the entry section is inclined at an angle of between 60 and 70 and the exit section ~rom betweeen 5 and 10 to the horizontal.
The proximity oi the strip to the support sur~ace ~ -o~ the table may be sensed by means o$ one or more pressure sensors located in or on the suriace oi the table at the transition between the entry and exit sections oi the table. Alternatively, the proximity or changes in proximity may be sensed by one or more position transducers located ad~acent the table at the transition between lts entry and exit sections.
i As the strip is transported through the iurnace ` it may be supported on a gas cushion. The gas cushion within the iurnace may consist oi any gas or mixtures oi gases whose physical and chemical properties are compatible with the support system and the strip mate~ial being processed. For example, the gas çushion may consist o~ argon or nitrogen or mixtures oi argon j and nitrogen, oi' nitrogen and hydrogen, or argon, nitrogen and hydrogen, or oi argon/nitrogen and methane. Prei'erably, the gas mixture employed comprises approximately 80% o~ dense support gas ti.e. argon and/
' or nttrogen).
.~ :
1079~64 In a preferred embodiment, green strip produced by roll compacting metal powder is transported to a sinter ~urnace in a manner in accordance with one o~ the aspects oi the invention re~erred to above. The green strip is propelled through the ~urnace by means o~ a pair o~ pinch rolls located downstream o~ the furnace and is supported by means oi a gas cushion during its passage through the ~urnace. In this pre~erred embodiment, the strip is subjected to substantially ]o zero tension during sintering. By 'substantially zero tension' is meant tensile stress applied to the strip whllst in the ~urnace o~ a value which does not exceed a value which permits the sintering strip to shrink linearly. The tensile stresses applied to ~erritic and austenitic stainless steel green strip should be less than 50 and 70 kN/m2 respectively. For both materials the tensile stresses applied may suitably be less than 15 kN/m2 and pre~erably less than 10 kN/m2.
Negative tensile stresses (that is to say compressible stresses) may be applied t~ the strip during sinterlng but only in so ~ar as the application o~ such stresses does not cause the green strlp to buckle as it passes through the iurnace.
The lnvention will now be described by way o~
example with reiterence to the accompanying diagrammatic drawings in which :
Figure 1 is a s~de elevational view partly in section o~ apparatus i?or producing metal strip in accordance with the lnvention, .
-.. ... , ., . . ~ - -~079064 Figure 2 is a section taken through the iurnace illustrated in Figure l, and Figure 3 illustrates an alternative arrangement for carrying out the invention.
The apparatus illustrated in Figures l and 2 includes a hopper l which contains metal powder "P".
The powder may be manufactured i'rom a rerrous material ior example, ferritic or austenitic stainless steels, a non-ferrous material such as aluminium, a metal bearing ore or a metallic oxide. Immediately below the hopper 1 a pair oi compacting rolls 2-2 are arranged so that the powder which leaves the hopper 1 is drawn .
into the nip between the rolls 2-2. As illustrated the rolls 2-2 are constrained to rotate in opposite directions.
lS and the whole assembly oi rolls 2-2 and hopper l . . .
compri~es a compaction mill through which green strip . "S" is produced.
Downstream oi the compaction mill are provided in sequence a iirst guide roll 4, and edge trimming and riveting assembly 5, pinch rolls 6, 7 ror respectively transporting green strip to and irom the assembly 5, a..second guide roll 8, a floatation table 9, a sinter iurnace lO, a pair of take-oii pinch rolls 11 and a coiler assembly 12.
The pinch rolls 7 eiiectively isolate the strip downstream oi the guide roll 8 irom tensile stresses imposed prior to the guide roll 8 and their speed is ,i . . .
' , ~079064 controlled to maintain a given catenary loop "L" in the green strip between the compaction mill and the iirst guide roll 4. The loop "L" accommodates variations in output from the compaction mill. The rolls 4, 6, 7 and 8 are all driven irom a common drive and their speeds of rotation are controlled through a speed controller 13.
The pinch rolls 6 are employed at start up to ieed ~reen strip initially into the edge trimming and riveting assembly 5. The leading end of the strip is riveted to the tail end oi the strip already present in the assembly 5 to overcome threading problems.
~ reen strip leaving the pinch rolls 7 is ied around the circumierence oi the guide roll 8 and - passes downwardly on to the suriace oi the iloatation table 9.
The iloatation table 9 has a strip support suriace iormed with an entry section 14 and an exit section 15. As will be seen irom Figure 1, the exit section 15 is inclined downwardly at an angle to the horizontal which is less than the angle at which the entry section 14 is incllned. The angle oi inclination oi the entry section conventiently lies between 50 and 80 to the horizontal and that oi the exit section between 2 and 20 to the horozontal. Preierably, these angles lie ;l 25 respectively between 50 and 60 and 5 and 10 to the ~ horizontal. In any event the an~le oi 1nc1lnation oi ' .
the exit section 14 ~s selected to be greater than the angle o~ iriction oi the strip passing over the table.
The support sur~ace oi the table 9 is iormed with a plurality oi round or slot like aperatures through which gas under pressure ilows Upwardly towards the under suriace of the strip to support the strip above the table suriace. The gas supplied to the sections 14 and 15 may either be supplied irom a common source or ~-~rom independent sources. The gas may, ior example, ~e air.
One or more spaced position transducers 16 are positioned above the suriace oi the table at the transition between the entry and exit sections 14, 15 respectively and are operable to sense changes in the proximlty oi the strip to the table suriace. The - transducers 16 provide a measure oi the tensile stress existing within the strip as it passes over the table and are connected to pass common signals to the speed controller 13.
In an alternative unlllustrated embodiment, the transducers 16 are connected to pass comm~nd signals to a speed controller oi the take-oii' pinch rolls 11.
The sinter iurnace 10 has a reiractory lining 18 and is provided with an entry seal 19 and an exit 25 seal 20 located at each respective end oi the ~urnace. ~ -'J, Alternatively the gas entry ports 21 may be spaced along one or both sides oi the iurnace 10.
At least a part oi the gas contained in the iurnace lO may be w1t~drawn through a conduit 22 ~nd return-d to ' 1~79064 the entry ports 21 via a cooler 23, compressor 24 and a gas treatment chamber 25 in which impurities such as oxygen are removed. Additional gas ~rom a source 26 o~ the required composition is added to the recirculating S gas prior to its return to the iurnace. Prior to re-entry to the iurnace, the recirculating and additional gas are heated to a predetermined temperature.
Electrical heatlng elements 27 are incorporated inside the ~urnace 10 together with one or more temperature controllers (not shown). A pair oi lips
In Canadian Patent No 1013180 there is described and claimed a method and apparatus for the continuous produ~tion of metal strip in which compacted powder in the iorm oi green strip is ied to a sinter ~urnace and is supported by a gaseous cushion as it is transported through the iurnace, the strip transport being controlled to perm~t the strip to shrink linearly as it passes through the iurn~ce.
In order to minimise the tensile stress imposed on the green strip and thereby to permlt the strip to shrink linearly as it passes through the iurnace, it is necessary to ensure that as the strip enters the iurnace it is isolated, so iar as is practicable, ~rom tensile stresses present in the strip upstream o~ the iurnace, and that lt is transported to the iurnace in a substantlally stress ~ree condition.
I It is also necessary to provide within the strip ¦ length a loop in which a sui~icient length o~ strip can be stored to provide a means o~ accommodating any l 25 temporary mismatch between the speeds at which the strip ¦ is supplled to and withdrawn irom the iurnace. Such a I mismatch would occur, ~or example, during changes i~ line speed.
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1~)79064 According to the present invention in one aspect, there is provided apparatus for transporting strip materials comprises a floatation table formed with a strip support s~r~ace having in the intended direction o~ travel of strip over the table surface a downwardly inclined entry section and an exit section inclined at an angle to the horizontal less than that of the entry section but greater than the angle of friction of the strip which is to travel over the strip support sur~ace, means being provided in the vicinity of the transition between the entry and exit sections o~ the support surface for senslng the proximity of or changes ln the proximity of strip passing over the table to said support surface. By 'angle o~ iriction' is meant the angle oi' - inclination at which the strip ~ust slides down the support surface under its own weight.
According to the present invention in a further aspect,apparatus ~or transporting metal strip to and through a sinter furnace comprises means for guiding the strip downwardly on to the support suri'ace oi' a . 20 iloatation table ~ormed, in the intended direction of strip over the table, with downwardly inclined entry anA exit sections oi dii'~ering ~lope, the exit section being inclined at an angle to the horizontal less than I that o$ the entry section, but greater than the angle ¦25 of friction of strip travelling over its support surface, : -meaDs ~or seDsing the proximlty o~ tho strlp to the _ 2 .
. .
' : ' ' . ~ ' . - :. ~
9~:)64 support suriace as the strip passes between the entry section and the exit section o~ the table, means ior propelling the strip through the sinter iurnace and means ior controlling the strip propelling means in r~ dependence upon the sensed proximity to maintain the tensile stress imposed in the strip entering the furnace minimal.
According to the present invention in a still further aspect, there is provided a method oi transporting strip to a ~urnace through which it is propelled by a pair oi pinch rolls positioned downstream of the iurnace, the method comprising the steps oi transporting the strip to the iurnace over the support surface oi a , downwardly inclined iloatation table formed with an ;, ~5 entry section and an exit section inclined at an angle the horizontal less than that oi the entry section but greater than the angle oi iriction of strip travelling over its suriace, sensing the proximity oi the strip to the support suriace oi the iloatation table as it ~ passes irom the table entry section to the table exit section and controlling the rate at which strip approaches the entry section oi the iloatation table in ¦ dependence upon the sensed proximity to minimise the .1 tensile stiess imposed in the strip as it enters the . 25 i'urnace.
. In one embodiment o~ the invention ior transporting green strip produced by roll compacting metal powder . continuously to a sinter iurnacej the entry section 3 _ ' .
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-' ' . ~ .
o~ the support suriace of the iloatation table is inclined at an angle oi between 50 and 80 to the horizontal and the exit section is inclined at an ang~e o~ between 2 and 15 to the horlzontal. In a pre~erred embodiment the entry section is inclined at an angle of between 60 and 70 and the exit section ~rom betweeen 5 and 10 to the horizontal.
The proximity oi the strip to the support sur~ace ~ -o~ the table may be sensed by means o$ one or more pressure sensors located in or on the suriace oi the table at the transition between the entry and exit sections oi the table. Alternatively, the proximity or changes in proximity may be sensed by one or more position transducers located ad~acent the table at the transition between lts entry and exit sections.
i As the strip is transported through the iurnace ` it may be supported on a gas cushion. The gas cushion within the iurnace may consist oi any gas or mixtures oi gases whose physical and chemical properties are compatible with the support system and the strip mate~ial being processed. For example, the gas çushion may consist o~ argon or nitrogen or mixtures oi argon j and nitrogen, oi' nitrogen and hydrogen, or argon, nitrogen and hydrogen, or oi argon/nitrogen and methane. Prei'erably, the gas mixture employed comprises approximately 80% o~ dense support gas ti.e. argon and/
' or nttrogen).
.~ :
1079~64 In a preferred embodiment, green strip produced by roll compacting metal powder is transported to a sinter ~urnace in a manner in accordance with one o~ the aspects oi the invention re~erred to above. The green strip is propelled through the ~urnace by means o~ a pair o~ pinch rolls located downstream o~ the furnace and is supported by means oi a gas cushion during its passage through the ~urnace. In this pre~erred embodiment, the strip is subjected to substantially ]o zero tension during sintering. By 'substantially zero tension' is meant tensile stress applied to the strip whllst in the ~urnace o~ a value which does not exceed a value which permits the sintering strip to shrink linearly. The tensile stresses applied to ~erritic and austenitic stainless steel green strip should be less than 50 and 70 kN/m2 respectively. For both materials the tensile stresses applied may suitably be less than 15 kN/m2 and pre~erably less than 10 kN/m2.
Negative tensile stresses (that is to say compressible stresses) may be applied t~ the strip during sinterlng but only in so ~ar as the application o~ such stresses does not cause the green strlp to buckle as it passes through the iurnace.
The lnvention will now be described by way o~
example with reiterence to the accompanying diagrammatic drawings in which :
Figure 1 is a s~de elevational view partly in section o~ apparatus i?or producing metal strip in accordance with the lnvention, .
-.. ... , ., . . ~ - -~079064 Figure 2 is a section taken through the iurnace illustrated in Figure l, and Figure 3 illustrates an alternative arrangement for carrying out the invention.
The apparatus illustrated in Figures l and 2 includes a hopper l which contains metal powder "P".
The powder may be manufactured i'rom a rerrous material ior example, ferritic or austenitic stainless steels, a non-ferrous material such as aluminium, a metal bearing ore or a metallic oxide. Immediately below the hopper 1 a pair oi compacting rolls 2-2 are arranged so that the powder which leaves the hopper 1 is drawn .
into the nip between the rolls 2-2. As illustrated the rolls 2-2 are constrained to rotate in opposite directions.
lS and the whole assembly oi rolls 2-2 and hopper l . . .
compri~es a compaction mill through which green strip . "S" is produced.
Downstream oi the compaction mill are provided in sequence a iirst guide roll 4, and edge trimming and riveting assembly 5, pinch rolls 6, 7 ror respectively transporting green strip to and irom the assembly 5, a..second guide roll 8, a floatation table 9, a sinter iurnace lO, a pair of take-oii pinch rolls 11 and a coiler assembly 12.
The pinch rolls 7 eiiectively isolate the strip downstream oi the guide roll 8 irom tensile stresses imposed prior to the guide roll 8 and their speed is ,i . . .
' , ~079064 controlled to maintain a given catenary loop "L" in the green strip between the compaction mill and the iirst guide roll 4. The loop "L" accommodates variations in output from the compaction mill. The rolls 4, 6, 7 and 8 are all driven irom a common drive and their speeds of rotation are controlled through a speed controller 13.
The pinch rolls 6 are employed at start up to ieed ~reen strip initially into the edge trimming and riveting assembly 5. The leading end of the strip is riveted to the tail end oi the strip already present in the assembly 5 to overcome threading problems.
~ reen strip leaving the pinch rolls 7 is ied around the circumierence oi the guide roll 8 and - passes downwardly on to the suriace oi the iloatation table 9.
The iloatation table 9 has a strip support suriace iormed with an entry section 14 and an exit section 15. As will be seen irom Figure 1, the exit section 15 is inclined downwardly at an angle to the horizontal which is less than the angle at which the entry section 14 is incllned. The angle oi inclination oi the entry section conventiently lies between 50 and 80 to the horizontal and that oi the exit section between 2 and 20 to the horozontal. Preierably, these angles lie ;l 25 respectively between 50 and 60 and 5 and 10 to the ~ horizontal. In any event the an~le oi 1nc1lnation oi ' .
the exit section 14 ~s selected to be greater than the angle o~ iriction oi the strip passing over the table.
The support sur~ace oi the table 9 is iormed with a plurality oi round or slot like aperatures through which gas under pressure ilows Upwardly towards the under suriace of the strip to support the strip above the table suriace. The gas supplied to the sections 14 and 15 may either be supplied irom a common source or ~-~rom independent sources. The gas may, ior example, ~e air.
One or more spaced position transducers 16 are positioned above the suriace oi the table at the transition between the entry and exit sections 14, 15 respectively and are operable to sense changes in the proximlty oi the strip to the table suriace. The - transducers 16 provide a measure oi the tensile stress existing within the strip as it passes over the table and are connected to pass common signals to the speed controller 13.
In an alternative unlllustrated embodiment, the transducers 16 are connected to pass comm~nd signals to a speed controller oi the take-oii' pinch rolls 11.
The sinter iurnace 10 has a reiractory lining 18 and is provided with an entry seal 19 and an exit 25 seal 20 located at each respective end oi the ~urnace. ~ -'J, Alternatively the gas entry ports 21 may be spaced along one or both sides oi the iurnace 10.
At least a part oi the gas contained in the iurnace lO may be w1t~drawn through a conduit 22 ~nd return-d to ' 1~79064 the entry ports 21 via a cooler 23, compressor 24 and a gas treatment chamber 25 in which impurities such as oxygen are removed. Additional gas ~rom a source 26 o~ the required composition is added to the recirculating S gas prior to its return to the iurnace. Prior to re-entry to the iurnace, the recirculating and additional gas are heated to a predetermined temperature.
Electrical heatlng elements 27 are incorporated inside the ~urnace 10 together with one or more temperature controllers (not shown). A pair oi lips
2~ are mounted one on each vertical wall oi the iurnace and extend lengthwise hori~ontally through the iurnace.
Each lip is inclined laterally towards the centre line o~ the iurnace. In an alternative arrangement the lips ~8 are inclined downwardly at a small angle in a lengthwise as well as lateral sense.
; On leaving the sinter furnace 10, the strip is cooled, passes through the take-oii pinch rolls ll and is coiled by a strip coiler 12.
In operation oi the apparatus illustrated, steel powder "P" irom the hopper 1 is drawn into the nip between the compaction rolls 2-2 and emerges as green strip "S". The str~p is guided around the circumierence o~ the guide roll 4 and transported through the assembly 5 by the pinch rolls 6, 7. Aiter leaving the assembly 5 the green strip is ied around the circum~erence oi the guide roll 8 and passe~ downwardly onto the suriace ' 1~7~64 of the iloatation table 9 by which it is guided into the iurnace 10 through the entry seal 19. When in the furnace, the strip is supported by means of gas supplied under pressure through the gas inlet ports S 21. Gas losses through the entry and exit ports are compensated ior by addition oi gas from a source - external to the iurnace.
As the strip passes irom the entry section 14 oi the iloatation table 9 on to the exit section 15 a shallow loop or catenary i5 iormed in the strip. The coniiguration oi this loop or catenary provides a control oi the tensile stress existing within the green strip passing irom the guide roll 8 and the entry vestible oi the iurnace and the coniiguration oi the loop or catenary is determined by the rotation oi speed oi the guide roll 8. In addition to providing a control oi the tensile stress, the loop provides a suiiicient stored strip length to accommodate any temporary mismatch between the speeds at which strip is supplied to and withdrawn irom the iurnace 10 as may occur during changes in line speed.
The rate at which the strip is transported through the iurnace 10 is determlned by the speed oi rotation oi the pinch rolls 11 and the tensile stress ' exist~ng in the strip is caused in part by tension in the strip upstream oi the iurnace and irictional drag between the strip and furnace hearth at local points oi contact along the length of the iurnace.
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1C~79~64 Back tension applied upstream of the pinch rolls 7 is isolated from the strip by the pinch rolls 7. Tensile stress within the strip at the entry to the ~urnace are minimised by controlling the speed at which strip approaches the entry section 14 of the ~loatation table so as to maintain a given strip path between the guide roll 8 and the ~urnace. This desired path is maintained by sensing changes in the proximity of the strip to the table surface by means of the transducers 16 and controlling the rotational speed oi' the rolls 4, 6, 7 and 8 through controller 13 in dependence on any sensed changes.
Thus, the strip being sintered within the ~urnace is e~rectively isolated ~rom accelerations or decelerations caused by operation o~ the control following command signals received rrom the transducers 16. Tensile s~resses imposed in the strip within the ~urnace ch~mber are minimised by controlling the ~low o~ gas into the strip support systems so as substantially to eliminate ~riction between the strip and the furnace hearth.
In the embodiment illustrated ln Figure 1 the ~loatation table comprises two straight sections 14, 15 joined together in any convenient manner. In the embodiment illustrated in Figure 3 the ~loatation table comprises a single curved surrace having a steeply inclined entry section and a more shallow inclined exit section, the transition between these two sect-ions taking the i'orm o~ a curved sur~ace.
~079064 Also, as illustrated in Figure 1 the section 15 o~ the iloatation table terminates ~ust upstream oi the entry seal 19. In an alternative arrangement the exit section 15 oi the table may protrude through the seal 19 and terminate ~ust inside the iurnace 10.
In an unillustrated embodiment the iloatation table 9 may comprise more than two diiierently inclined sections. For example, an additional sloping suriace may be provided between the entry and exit sections of the table illustrated in Figure 1 the angle of inclination oi this intermediate section lying between those oi the entry and exlt sectlons.
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Each lip is inclined laterally towards the centre line o~ the iurnace. In an alternative arrangement the lips ~8 are inclined downwardly at a small angle in a lengthwise as well as lateral sense.
; On leaving the sinter furnace 10, the strip is cooled, passes through the take-oii pinch rolls ll and is coiled by a strip coiler 12.
In operation oi the apparatus illustrated, steel powder "P" irom the hopper 1 is drawn into the nip between the compaction rolls 2-2 and emerges as green strip "S". The str~p is guided around the circumierence o~ the guide roll 4 and transported through the assembly 5 by the pinch rolls 6, 7. Aiter leaving the assembly 5 the green strip is ied around the circum~erence oi the guide roll 8 and passe~ downwardly onto the suriace ' 1~7~64 of the iloatation table 9 by which it is guided into the iurnace 10 through the entry seal 19. When in the furnace, the strip is supported by means of gas supplied under pressure through the gas inlet ports S 21. Gas losses through the entry and exit ports are compensated ior by addition oi gas from a source - external to the iurnace.
As the strip passes irom the entry section 14 oi the iloatation table 9 on to the exit section 15 a shallow loop or catenary i5 iormed in the strip. The coniiguration oi this loop or catenary provides a control oi the tensile stress existing within the green strip passing irom the guide roll 8 and the entry vestible oi the iurnace and the coniiguration oi the loop or catenary is determined by the rotation oi speed oi the guide roll 8. In addition to providing a control oi the tensile stress, the loop provides a suiiicient stored strip length to accommodate any temporary mismatch between the speeds at which strip is supplied to and withdrawn irom the iurnace 10 as may occur during changes in line speed.
The rate at which the strip is transported through the iurnace 10 is determlned by the speed oi rotation oi the pinch rolls 11 and the tensile stress ' exist~ng in the strip is caused in part by tension in the strip upstream oi the iurnace and irictional drag between the strip and furnace hearth at local points oi contact along the length of the iurnace.
_ I0 -.
1C~79~64 Back tension applied upstream of the pinch rolls 7 is isolated from the strip by the pinch rolls 7. Tensile stress within the strip at the entry to the ~urnace are minimised by controlling the speed at which strip approaches the entry section 14 of the ~loatation table so as to maintain a given strip path between the guide roll 8 and the ~urnace. This desired path is maintained by sensing changes in the proximity of the strip to the table surface by means of the transducers 16 and controlling the rotational speed oi' the rolls 4, 6, 7 and 8 through controller 13 in dependence on any sensed changes.
Thus, the strip being sintered within the ~urnace is e~rectively isolated ~rom accelerations or decelerations caused by operation o~ the control following command signals received rrom the transducers 16. Tensile s~resses imposed in the strip within the ~urnace ch~mber are minimised by controlling the ~low o~ gas into the strip support systems so as substantially to eliminate ~riction between the strip and the furnace hearth.
In the embodiment illustrated ln Figure 1 the ~loatation table comprises two straight sections 14, 15 joined together in any convenient manner. In the embodiment illustrated in Figure 3 the ~loatation table comprises a single curved surrace having a steeply inclined entry section and a more shallow inclined exit section, the transition between these two sect-ions taking the i'orm o~ a curved sur~ace.
~079064 Also, as illustrated in Figure 1 the section 15 o~ the iloatation table terminates ~ust upstream oi the entry seal 19. In an alternative arrangement the exit section 15 oi the table may protrude through the seal 19 and terminate ~ust inside the iurnace 10.
In an unillustrated embodiment the iloatation table 9 may comprise more than two diiierently inclined sections. For example, an additional sloping suriace may be provided between the entry and exit sections of the table illustrated in Figure 1 the angle of inclination oi this intermediate section lying between those oi the entry and exlt sectlons.
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Claims (12)
1. Apparatus for transporting strip materials comprising a floatation table formed with a strip support surface having, in the intended direction of travel of strip over the table surface, a downwardly inclined entry section and an exit section inclined at an angle to the horizontal less than that of the entry section but greater than the angle of friction of the strip which is to travel over the strip support surface, means being provided in the vicinity of the transition between the entry and exit sections of the support surface for sensing the proximity of or changes in the proximity of strip passing over the table to said support surface.
2. Apparatus for transporting metal strip to and through a sinter furnace comprising means for guiding the strip downwardly on to the support surface of a floatation table formed, in the intended direction of strip over the table, with downwardly inclined entry and exit sections of differing slope, the exit section being inclined at an angle to the horizontal less than that of the entry section, but greater than the angle of friction of strip travelling over its support surface, means for sensing the proximity of the strip to the support surface as the strip passes between the entry section and the exit section of the table, means for propelling the strip through the sinter furnace and means for controlling the strip propelling means in dependence upon the sensed proximity to maintain the tensile stress imposed in the strip entering the furnace minimal.
3. Apparatus as claimed in claim 1 wherein the entry section of the support surface is inclined at an angle of between 50° and 80° to the horizontal.
4. Apparatus as claimed in claim 1 wherein the exit section of the support surface is inclined at an angle of between 2° and 15° to the horizontal.
5. Apparatus as claimed in claim 3 wherein the entry section of the support surface is inclined at an angle of between 60° and 70° to the horizontal.
6. Apparatus as claimed in claim 4 wherein the exit section of the support surface is inclined at an angle of between 5° and 10° to the horizontal.
7. Apparatus as claimed in claim 1 wherein pressure sensors are located adjacent the strip support surface at the transition between its entry and exit sections.
8. Apparatus as claimed in claim 1 wherein position transducers are located adjacent the strip support surface at the transition between its entry and exit sections.
9. Apparatus as claimed in claim 2 wherein the strip is transported through the sinter furnace on a gaseous cushion.
10. Apparatus as claimed in claim 9 wherein the gas cushion consists of argon or nitrogen or mixtures of argon and nitrogen or nitrogen and hydrogen or argon, nitrogen and hydrogen or of argon, nitrogen and methane.
11. Apparatus as claimed in claim 2 wherein a pair of pinch rolls is located downstream of the furnace to propel the strip through the furnace.
12. A method of transporting strip to a furnace through which it is propelled by a pair of pinch rolls positioned downstream of the furnace, the method comprising the steps of transporting the strip to the furnace over the support surface of a downwardly inclined floatation table formed with an entry section and an exit section inclined at an angle to the horizontal less than that of the entry section but greater than the angle of friction of strip travelling over its surface, sensing the proximity of the strip to the support surface of the floatation table as it passes from the table entry section to the table exit section and controlling the rate at which strip approaches the entry section of the floatation table in dependence upon the sensed proximity to minimise the tensile stress imposed in the strip as it enters the furnace.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB36100/76A GB1568222A (en) | 1976-09-01 | 1976-09-01 | Production of metal strip |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1079064A true CA1079064A (en) | 1980-06-10 |
Family
ID=10384968
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA285,688A Expired CA1079064A (en) | 1976-09-01 | 1977-08-29 | Production of metal strip |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS6043401B2 (en) |
| BE (1) | BE858312A (en) |
| CA (1) | CA1079064A (en) |
| DE (1) | DE2739203A1 (en) |
| FR (1) | FR2363504A1 (en) |
| GB (1) | GB1568222A (en) |
| IT (1) | IT1083614B (en) |
| LU (1) | LU78056A1 (en) |
| NL (1) | NL7709659A (en) |
| SE (1) | SE7709774L (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3406036A1 (en) * | 1984-02-20 | 1985-08-22 | Mannesmann AG, 4000 Düsseldorf | METHOD AND DEVICE FOR PRODUCING THIN METAL STRINGS FROM METAL MELT, IN PARTICULAR. OF STEEL STRIPS |
| CN105253674B (en) * | 2015-09-28 | 2017-04-12 | 宁波市岭登电器有限公司 | Steel belt transmission device, and system and method for controlling steel belt transmission device |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3122434A (en) * | 1960-06-03 | 1964-02-25 | Republic Steel Corp | Continuous process of producing strips and sheets of ferrous metal directly from metal powder |
| GB1039548A (en) * | 1963-10-24 | 1966-08-17 | Davy & United Eng Co Ltd | Production of metallic strip |
| IE39215B1 (en) * | 1973-05-03 | 1978-08-30 | British Steel Corp | Improvements in or relating to the production of metal strrip from powder |
-
1976
- 1976-09-01 GB GB36100/76A patent/GB1568222A/en not_active Expired
-
1977
- 1977-08-29 CA CA285,688A patent/CA1079064A/en not_active Expired
- 1977-08-30 FR FR7726331A patent/FR2363504A1/en not_active Withdrawn
- 1977-08-31 DE DE19772739203 patent/DE2739203A1/en not_active Withdrawn
- 1977-08-31 IT IT68945/77A patent/IT1083614B/en active
- 1977-08-31 SE SE7709774A patent/SE7709774L/en unknown
- 1977-08-31 LU LU78056A patent/LU78056A1/xx unknown
- 1977-08-31 BE BE180607A patent/BE858312A/en unknown
- 1977-09-01 NL NL7709659A patent/NL7709659A/en unknown
- 1977-09-01 JP JP52105375A patent/JPS6043401B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| BE858312A (en) | 1977-12-16 |
| LU78056A1 (en) | 1978-01-11 |
| GB1568222A (en) | 1980-05-29 |
| IT1083614B (en) | 1985-05-21 |
| FR2363504A1 (en) | 1978-03-31 |
| DE2739203A1 (en) | 1978-03-02 |
| NL7709659A (en) | 1978-03-03 |
| SE7709774L (en) | 1978-03-02 |
| JPS6043401B2 (en) | 1985-09-27 |
| JPS5352218A (en) | 1978-05-12 |
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| MKEX | Expiry |