WO1994026443A1 - Two-roll continuous casting - Google Patents
Two-roll continuous casting Download PDFInfo
- Publication number
- WO1994026443A1 WO1994026443A1 PCT/GB1994/000993 GB9400993W WO9426443A1 WO 1994026443 A1 WO1994026443 A1 WO 1994026443A1 GB 9400993 W GB9400993 W GB 9400993W WO 9426443 A1 WO9426443 A1 WO 9426443A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- rolls
- bite
- molten metal
- nozzle
- high frequency
- Prior art date
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
- B22D11/0637—Accessories therefor
- B22D11/064—Accessories therefor for supplying molten metal
Definitions
- molten metal is fed into the bite between a pair of counter- rotating cooled rolls.
- the molten metal issuing from a nozzle contacts the cooled rolls it starts to solidify and, by the time the metal reaches the common centre-line of the two rolls, it is completely solid.
- the transition from liquid to solid is characterised by the presence of three distinct regions - the liquid region; the region containing a mixture of solid and liquid, sometimes referred to as the mushy region; and the solid region.
- the demarcation between the mushy region and the solid region is known as the solidus.
- the extent of the mushy region is a function of the freezing range of the alloy in question, whereas the extent of the liquid region is a function of the casting conditions. For example, if the casting speed is increased or the position of the tip of the nozzle is moved closer to the common centre-line of the casting rolls, the solidus will move closer to the common centre-line of the rolls. Conversely, if the casting speed is reduced or the tip of the nozzle is moved away from the common centre-line of the casting rolls, the solidus will move away from the common centre-line of the rolls.
- the position of the solidus lies in a plane substantially normal to the longitudinal axis of the strip , and that it is symmetrical with respect to the thickness of the strip being cast .
- the position of the solidus is much more difficult to maintain i . e . the solidus becomes non-planar and/or asymmetrical .
- a method of casting a metal strip comprises introducing molten metal into the bite between a pair of counter-rotating cooled rolls and the supply of molten metal to the bite is modulated at a uniform high frequency.
- the supp ly o f mo lten meta l to the bite is modulated in a controlled way in order to bring about controlled instability in the mushy region. This can be brought about in a number of ways: for example, the outlet of the feeder nozzle may be subjected to vibration in the direction of casting or a high frequency modulation signal may be applied to a servo valve which controls the gap between the rolls in order to modulate the gap.
- the speed of either or both of the rolls may be modulated. All these methods have the effect of producing a high frequency low amplitude disturbance applied to the molten metal and this results in the position of the solidus which extends across the width of the strip being substantially normal to, and symmetrical about, the longitudinal axis of the strip but the solidus has high frequency low amplitude perturbations. Perturbations of this form are much more desirable than the low frequency high amplitude perturbations which occur with the prior art casters.
- a caster comprises two cooled rolls, drive means for rotating the rolls in counter-rotating manner, means for introducing molten metal into the bite between the rolls and means for modulating the supply of molten metal to the bite, said modulation being at a uniform high frequency.
- Figure 1 is a diagrammatic side elevation of part of a two-roll caster
- Figure 2A is a diagrammatic plan on the line II-II of Figure 1;
- Figure 2B is an alternative plan similar to Figure 2A.
- a pair of liquid cooled rolls 1, 3 are arranged one above the other with a bite between them.
- a refractory nozzle 5 projects into the bite and the rolls are rotated in opposite directions by drive means indicated by reference 1' so that the part of the periphery of each roll adjacent the tip of the nozzle is rotating in the direction away from the nozzle.
- molten metal 9 usually aluminium or aluminium alloy
- molten metal 9 is introduced through the nozzle into the bite and, when the metal comes into contact with each of the cooled rolls, it starts to solidify and to form a skin and the skins are compressed at the position of minimum separation R of the rolls to produce strip 7.
- the molten metal 9 issuing from the outlet of the nozzle 5 passes through a partially molten and partially solidified stage 11, also referred to as a mushy stage. From the mushy stage solidification is completed to form the solid sheet 7.
- the liquid, mushy and solid sections 9, 11 and 7, respectively, are shown in Figure 2A.
- the line separating the mushy section 11 from the solid section 7 is known as the solidus and, desirably, this solidus remains symmetrical (with respect to the thickness of the strip) in the same position across the entire width of the strip being cast. As shown in Figure 2A, however, in use, the solidus is subjected to perturbations indicated by broken lines 13. Where these perturbations occur, there is a defect formed in the surface of the strip material and, consequently, it is desirable that the perturbations should be removed as far as possible.
- the high amplitude low frequency perturbations shown in Figure 2A are replaced by low amplitude high frequency perturbations shown by reference 13' in Figure 2B.
- This low amplitude high frequency arrangement produces a macroscopically planar interface which is much more acceptable than the interface shown in Figure 2A.
- a vibrator 15 may be connected to the tip of the nozzle 5 in order to vibrate the tip.
- the molten metal contained within the nozzle can be agitated with ultrasonic or electromagnetic means.
- a servo-valve (not shown) which controls the position of one or both of the rolls to thereby adjust the gap between the rolls of the caster may be operated at high frequency to modulate the roll gap and this too brings about the arrangement of the solidus which is shown in Figure 2B.
- the substantially uniform solidus position across the width of the strip can also be obtained by modulating at high frequency the operating speed of one or both of the rolls of the caster, for example by modulating the speed of the drive means 1' .
- the uniform high frequency at which the supply of molten metal to the bite is modulated is within the frequency range 15-25HZ, typically 20Hz.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Continuous Casting (AREA)
Abstract
A strip caster has a pair of counter rotating spaced apart cooled rolls (1, 3) and a nozzle (5) by which molten metal (9) is introduced into the bite between the rolls (1, 3), and steps are taken to modulate the supply of molten metal introduced into the bite to produce a more satisfactory solidus with a uniform and symmetrical shape.
Description
TWO-ROLL CONTINUOUS CASTING In the two-roll continuous casting process, molten metal is fed into the bite between a pair of counter- rotating cooled rolls. When the molten metal issuing from a nozzle contacts the cooled rolls it starts to solidify and, by the time the metal reaches the common centre-line of the two rolls, it is completely solid. The transition from liquid to solid is characterised by the presence of three distinct regions - the liquid region; the region containing a mixture of solid and liquid, sometimes referred to as the mushy region; and the solid region. The demarcation between the mushy region and the solid region is known as the solidus. The extent of the mushy region is a function of the freezing range of the alloy in question, whereas the extent of the liquid region is a function of the casting conditions. For example, if the casting speed is increased or the position of the tip of the nozzle is moved closer to the common centre-line of the casting rolls, the solidus will move closer to the common centre-line of the rolls. Conversely, if the casting speed is reduced or the tip of the nozzle is moved away from the common centre-line of the casting rolls, the solidus will move away from the common centre-line of the rolls.
For the production of cast sheet with good surface quality it is essential that the position of the solidus
lies in a plane substantially normal to the longitudinal axis of the strip , and that it is symmetrical with respect to the thickness of the strip being cast .
Any variation or perturbation in the solidus position will result in local differences in heat transfer conditions . The consequences of this are variations in microstructure and, in more severe cases , surface defects in the cast sheet.
As the casting speed is increased and as the gauge of the cast strip is decreased, the position of the solidus is much more difficult to maintain i . e . the solidus becomes non-planar and/or asymmetrical .
In practice , it is found that high amplitude perturbations can occur non-unif ormly at a low frequency across the width of the strip and thus the position of the solidus across the full width of the strip is not uniform.
It is an obj ect of the present invention to provide a method of , and apparatus for , overcoming this problem.
According to a f irst aspect of the present invention a method of casting a metal strip comprises introducing molten metal into the bite between a pair of counter-rotating cooled rolls and the supply of molten metal to the bite is modulated at a uniform high frequency. The supp ly o f mo lten meta l to the bite is
modulated in a controlled way in order to bring about controlled instability in the mushy region. This can be brought about in a number of ways: for example, the outlet of the feeder nozzle may be subjected to vibration in the direction of casting or a high frequency modulation signal may be applied to a servo valve which controls the gap between the rolls in order to modulate the gap. Alternatively, the speed of either or both of the rolls may be modulated. All these methods have the effect of producing a high frequency low amplitude disturbance applied to the molten metal and this results in the position of the solidus which extends across the width of the strip being substantially normal to, and symmetrical about, the longitudinal axis of the strip but the solidus has high frequency low amplitude perturbations. Perturbations of this form are much more desirable than the low frequency high amplitude perturbations which occur with the prior art casters.
According to a second aspect of the present invention a caster comprises two cooled rolls, drive means for rotating the rolls in counter-rotating manner, means for introducing molten metal into the bite between the rolls and means for modulating the supply of molten metal to the bite, said modulation being at a uniform high frequency.
In order that the invention may be more readily
understood, it will now be described, by way of example only, with reference to the accompanying drawings, in which:-
Figure 1 is a diagrammatic side elevation of part of a two-roll caster;
Figure 2A is a diagrammatic plan on the line II-II of Figure 1; and
Figure 2B is an alternative plan similar to Figure 2A.
Referring to Figure 1, a pair of liquid cooled rolls 1, 3 are arranged one above the other with a bite between them. A refractory nozzle 5 projects into the bite and the rolls are rotated in opposite directions by drive means indicated by reference 1' so that the part of the periphery of each roll adjacent the tip of the nozzle is rotating in the direction away from the nozzle.
In use, molten metal 9, usually aluminium or aluminium alloy, is introduced through the nozzle into the bite and, when the metal comes into contact with each of the cooled rolls, it starts to solidify and to form a skin and the skins are compressed at the position of minimum separation R of the rolls to produce strip 7. The molten metal 9 issuing from the outlet of the nozzle 5 passes through a partially molten and partially solidified stage 11, also referred to as a mushy stage. From the mushy stage
solidification is completed to form the solid sheet 7. The liquid, mushy and solid sections 9, 11 and 7, respectively, are shown in Figure 2A.
The line separating the mushy section 11 from the solid section 7 is known as the solidus and, desirably, this solidus remains symmetrical (with respect to the thickness of the strip) in the same position across the entire width of the strip being cast. As shown in Figure 2A, however, in use, the solidus is subjected to perturbations indicated by broken lines 13. Where these perturbations occur, there is a defect formed in the surface of the strip material and, consequently, it is desirable that the perturbations should be removed as far as possible.
In accordance with the present invention, the high amplitude low frequency perturbations shown in Figure 2A are replaced by low amplitude high frequency perturbations shown by reference 13' in Figure 2B. This low amplitude high frequency arrangement produces a macroscopically planar interface which is much more acceptable than the interface shown in Figure 2A.
To bring about the arrangement shown in Figure 2B, a vibrator 15 may be connected to the tip of the nozzle 5 in order to vibrate the tip. The molten metal contained within the nozzle, can be agitated with ultrasonic or electromagnetic means. As an alternative, a servo-valve
(not shown) which controls the position of one or both of the rolls to thereby adjust the gap between the rolls of the caster may be operated at high frequency to modulate the roll gap and this too brings about the arrangement of the solidus which is shown in Figure 2B. The substantially uniform solidus position across the width of the strip can also be obtained by modulating at high frequency the operating speed of one or both of the rolls of the caster, for example by modulating the speed of the drive means 1' .
The uniform high frequency at which the supply of molten metal to the bite is modulated is within the frequency range 15-25HZ, typically 20Hz.
Claims
1. A method of casting a metal strip in which molten metal is introduced into the bite between a pair of counter- rotating spaced-apart cooled rolls and characterised in that the supply of molten metal to the bite is modulated at a uniform high frequency.
2. A method as claimed in claim 1 characterised in that the supply is modulated by modulating the position of one or both of the rolls in the direction towards and away from the other roll to modulate the gap between the rolls.
3. A method as claimed in claim 1, characterised in that the supply is modulated by modulating the speed of rotation of one or both of the rolls.
4. A method as claimed in claim 1 in which the molten metal is introduced through a nozzle into the roll bite and characterised in that the position of the nozzle is modulated.
5. A method as claimed in claim 4 characterised in that the nozzle is vibrated in the direction of its length.
6. The method as claimed in any preceding claim characterised in that the high frequency is within the range 15-25HZ.
7. The method as claimed in claim 6 characterised in that the high frequency is typically 20Hz.
8. A strip caster comprising two spaced-apart cooled rolls, drive means for rotating the rolls in counter- rotating manner, means for introducing molten metal into the bite between the rolls and characterised in the provision of means for modulating the supply of molten metal to the bite, said modulation being at a uniform high frequency.
9. A strip caster as claimed in claim 8 characterised in the provision of means for vibrating the nozzle.
10. A strip caster as claimed in claim 9, characterised in that the means causes the nozzle to vibrate in the direction of its length.
11. A strip caster as claimed in claim 8 characterised in that the gap between the rolls is adjustable and means are provided for modulating the position of one or both of the rolls to modulate the roll gap.
12. A strip caster as claimed in claim 8 characterised in the provision of means associated with the drive means of one or both rolls to modulate the speed of rotation of the or each roll.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9309809.3 | 1993-05-12 | ||
GB939309809A GB9309809D0 (en) | 1993-05-12 | 1993-05-12 | Two-roll continuous casting |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1994026443A1 true WO1994026443A1 (en) | 1994-11-24 |
Family
ID=10735366
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1994/000993 WO1994026443A1 (en) | 1993-05-12 | 1994-05-09 | Two-roll continuous casting |
Country Status (2)
Country | Link |
---|---|
GB (1) | GB9309809D0 (en) |
WO (1) | WO1994026443A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001096047A1 (en) * | 2000-06-15 | 2001-12-20 | Ishikawajima-Harima Heavy Industries Company Limited | Strip casting |
US6988530B2 (en) | 2000-06-15 | 2006-01-24 | Castrip Llc | Strip casting |
CN101239358B (en) * | 2008-03-06 | 2010-06-30 | 张明 | Double-roller casting rolling-hot continuous rolling method and equipment |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2140721A (en) * | 1983-06-01 | 1984-12-05 | Alusuisse | Process for feeding molten metal |
US4694886A (en) * | 1985-05-28 | 1987-09-22 | Hitachi Zosen Corporation | Horizontal continuous casting apparatus |
DE3624114A1 (en) * | 1986-07-17 | 1988-01-21 | Max Planck Inst Eisenforschung | DEVICE FOR PRODUCING ROLLABLE SHEET FROM MELTING METAL |
JPS63126654A (en) * | 1986-11-14 | 1988-05-30 | Nkk Corp | Continuous casting method for cast slab |
JPS63171251A (en) * | 1987-01-10 | 1988-07-15 | Nippon Steel Corp | Method and apparatus for producing continuously cast metal strip |
JPS63290654A (en) * | 1987-05-22 | 1988-11-28 | Nisshin Steel Co Ltd | Strip continuous casting method |
JPS63303655A (en) * | 1987-06-01 | 1988-12-12 | Hitachi Zosen Corp | Device for controlling roll gap in continuous casting equipment |
JPS6448643A (en) * | 1987-08-17 | 1989-02-23 | Nippon Kokan Kk | Shifting mold type continuous casting apparatus |
-
1993
- 1993-05-12 GB GB939309809A patent/GB9309809D0/en active Pending
-
1994
- 1994-05-09 WO PCT/GB1994/000993 patent/WO1994026443A1/en active Application Filing
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2140721A (en) * | 1983-06-01 | 1984-12-05 | Alusuisse | Process for feeding molten metal |
US4694886A (en) * | 1985-05-28 | 1987-09-22 | Hitachi Zosen Corporation | Horizontal continuous casting apparatus |
DE3624114A1 (en) * | 1986-07-17 | 1988-01-21 | Max Planck Inst Eisenforschung | DEVICE FOR PRODUCING ROLLABLE SHEET FROM MELTING METAL |
JPS63126654A (en) * | 1986-11-14 | 1988-05-30 | Nkk Corp | Continuous casting method for cast slab |
JPS63171251A (en) * | 1987-01-10 | 1988-07-15 | Nippon Steel Corp | Method and apparatus for producing continuously cast metal strip |
JPS63290654A (en) * | 1987-05-22 | 1988-11-28 | Nisshin Steel Co Ltd | Strip continuous casting method |
JPS63303655A (en) * | 1987-06-01 | 1988-12-12 | Hitachi Zosen Corp | Device for controlling roll gap in continuous casting equipment |
JPS6448643A (en) * | 1987-08-17 | 1989-02-23 | Nippon Kokan Kk | Shifting mold type continuous casting apparatus |
Non-Patent Citations (5)
Title |
---|
PATENT ABSTRACTS OF JAPAN vol. 12, no. 376 (M - 750) 7 October 1988 (1988-10-07) * |
PATENT ABSTRACTS OF JAPAN vol. 12, no. 437 (M - 765) 17 November 1988 (1988-11-17) * |
PATENT ABSTRACTS OF JAPAN vol. 13, no. 100 (M - 805) 9 March 1989 (1989-03-09) * |
PATENT ABSTRACTS OF JAPAN vol. 13, no. 140 (M - 810) 6 April 1989 (1989-04-06) * |
PATENT ABSTRACTS OF JAPAN vol. 13, no. 237 (M - 833) 5 June 1989 (1989-06-05) * |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001096047A1 (en) * | 2000-06-15 | 2001-12-20 | Ishikawajima-Harima Heavy Industries Company Limited | Strip casting |
US6536506B2 (en) | 2000-06-15 | 2003-03-25 | Castrip Llc | Strip casting |
US6988530B2 (en) | 2000-06-15 | 2006-01-24 | Castrip Llc | Strip casting |
CN101239358B (en) * | 2008-03-06 | 2010-06-30 | 张明 | Double-roller casting rolling-hot continuous rolling method and equipment |
Also Published As
Publication number | Publication date |
---|---|
GB9309809D0 (en) | 1993-06-23 |
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