Double-roller continuous casting machine

Abstract

The utility model belongs to the technical field of steel rolling, and particularly relates to a double-roller continuous casting machine which comprises a pair of casting rollers, the pair of casting rollers can rotate reversely, so that the casting surfaces of the casting rollers advance and pass through a casting pool of molten steel supported on the casting surfaces, and the casting surface of the casting rollers can pass through the casting pool of the molten steel. The two-roll continuous casting machine is provided with a plurality of casting rolls and travels towards and through a nip between the casting rolls to produce a steel strip which exits the nip in a casting area of the two-roll continuous casting machine; a brush capable of rotating in contact with the casting surface of each casting roll after the casting surface passes through the nip and before the casting surface is rotated back to the casting bath, to disengage at least a portion of the solid oxide formed on the casting surface; and a suction device for extracting the detached solid oxide from the casting area. According to the double-roller continuous casting machine, at least the problem that solid oxides are excessively accumulated on the surfaces of the casting rollers can be solved.

Description

Technical Field

[0001] The utility model relates to manufacturing thin steel strips in a twin-roll continuous casting machine and in downstream processing steps.

[0002] The utility model particularly relates to a method and a device for extracting solid oxides from the vicinity of the casting rolls of a twin-roll continuous caster, wherein the solid oxides are usually in the form of dust particles and have been dislodged by a rotating wire brush (or other abrasive options). Background Art

[0003] In a twin roll continuous caster, molten steel is delivered from a delivery system to a casting pool supported on the casting surfaces of a pair of counter-rotating horizontal casting rolls, which are internally water-cooled so that a solidified metal shell forms on the surfaces of the moving casting rolls. The metal shells come together at the nip between them to produce a solidified strip product that is delivered downward from the nip between the casting rolls. The term "nip" is used herein to refer to the approximate area where the casting rolls are closest together.

[0004] The molten steel may be poured from the ladle into a smaller container or a series of smaller containers from which it flows through one or more metal delivery nozzles located above the nip to form a casting pool of molten metal supported on the casting surfaces of the casting rolls, above the nip and extending the length of the nip.

[0005] The casting pool is usually confined between side plates or side guards that are in sliding engagement with the end portions of the casting rolls to limit outflow of the casting pool. The upper surface of the casting pool (usually referred to as the "meniscus" level) is usually above the lower end of the transfer nozzle so that the lower end of the transfer nozzle is immersed in the casting pool.

[0006] When steel strip is cast by a twin roll caster, the thin strip leaves the roll gap, passes through a guide table, through a pinch roll stand, and then through a hot rolling mill where the thin strip is reduced to the desired thickness. The hot rolled strip is then cooled to form a strip having the desired microstructure for the end-use application. The cooled strip is then coiled, where the strip is periodically cut with a shear upstream of the coiler to form the desired length of strip in each coil.

[0007] When casting steel strip in a twin roll continuous caster, the temperature of the casting pool usually exceeds 1500°C, typically 1600°C or more, and very rapid cooling of the molten steel on the casting surfaces of the rolls is required to form a solidified shell in the short time that the casting surfaces are exposed to the casting pool of molten steel during each rotation of the casting rolls.

[0008] In some cases, solid oxides may form on the casting surfaces of the casting rolls as the rolls rotate away from the nip between the rolls.The accumulation of solid oxides is undesirable for a number of reasons.

[0009] One suggestion to minimize solid oxide accumulation on the casting surfaces of the casting rolls and provide oxide thickness control is to provide the twin roll caster with rotating wire brushes (usually stainless steel wire brushes) that are biased to contact the casting rolls and break off at least a portion of any solid oxide that forms on the casting rolls.

[0010] The utility model provides an improvement on the twin-roll continuous casting machine and casting method described in the previous paragraph.

[0011] The above comments are not an admission of common knowledge in China or elsewhere. Utility Model Content

[0012] Applicants have recognized that the use of wire brushes (or other abrasive options) to break solid oxide from the surfaces of the casting rolls of a twin roll continuous caster may result in the accumulation of solid oxide (typically in the form of dust particles) on the casting roll surfaces as the brushes become saturated with dust, and this may be undesirable, for example resulting in poor solidification caused by the influence of excess oxide on the casting roll surfaces.

[0013] The utility model provides a method and a device for extracting solid oxides. The solid oxides are usually in the form of dust particles. The solid oxides have been separated from the casting surface of the casting roll of a twin-roll continuous casting machine by a rotating brush (or other abrasive options).

[0014] The utility model provides a method for casting a steel strip in a twin-roll continuous casting machine, comprising:

[0015] counter-rotating a pair of casting rolls of the twin roll continuous caster so that casting surfaces of the casting rolls travel through a casting pool of molten steel supported on the casting surfaces and toward and through a nip between the casting rolls to produce a steel strip that exits the nip in a casting region of the twin roll continuous caster;

[0016] rotating a brush that contacts the casting surface of each casting roll after the casting surface passes through the nip and before it rotates back into the casting pool, generally rotating the brush in the same direction as the direction of rotation of the casting rolls, and dislodging at least a portion of the solid oxide formed on the casting surface; and

[0017] Suction is applied and the detached solid oxide is extracted from the casting zone.

[0018] Typically, the method includes applying at least substantially constant suction across the width of each casting roll.

[0019] The method may include applying suction by:

[0020] With respect to each brush assembly housing, the housing at least substantially confines the dislodged solid oxide in the vicinity of the brush, and

[0021] A suction system is actuated to extract the dislodged solids from the vicinity of each brush and transport the solid oxide away from the casting area.

[0022] The utility model provides a method for extracting solid oxides, wherein the solid oxides are detached from a pair of counter-rotating casting rolls of a twin-roll continuous caster by means of a rotating brush (or other abrasive options) during continuous casting of a thin cast steel strip by the twin-roll continuous caster. The method comprises applying suction to extract the detached solid oxides from the casting area of ​​the twin-roll continuous caster.

[0023] Typically, the method includes applying at least substantially constant suction across the width of each casting roll.

[0024] The utility model also provides a twin-roll continuous casting machine, which comprises:

[0025] a pair of casting rolls capable of counter-rotating so that casting surfaces of the casting rolls travel through a casting pool of molten steel supported on the casting surfaces and toward and through a nip between the casting rolls to produce a steel strip that exits the nip in a casting zone of the twin roll continuous caster;

[0026] a brush capable of rotating in contact with the casting surface of each casting roll after the casting surface passes through the nip and before it rotates back into the casting pool, typically in a direction opposite to the direction of rotation of the casting rolls, to dislodge at least a portion of the solid oxide formed on the casting surface; and

[0027] A suction device is provided for extracting the detached solid oxide from the casting zone.

[0028] Typically, the suction apparatus is configured to apply at least substantially constant suction across the width of the casting rolls.

[0029] In one embodiment, the suction device may include:

[0030] a housing that at least substantially confines the detached solid oxide to a volume in the vicinity of each brush, and

[0031] A suction system is operable to extract the dislodged solids from the volume in the vicinity of each brush and transport the solid oxide away from the casting area.

[0032] The housing may comprise at least one suction outlet which may be connected to a suction system.

[0033] In another embodiment, the suction device may include:

[0034] a housing, for example in the form of a metal cowling (or other suitable removable housing), configured to cover each brush to at least substantially confine solid oxide that breaks away from the casting surfaces of the casting rolls to a volume in the vicinity of each brush, wherein the housing has at least one suction discharge port; and

[0035] A suction system includes a fan and an extraction hose connecting the fan and the suction outlet, the suction outlet being configured to remove solid oxide from the volume near each brush by suction and transport the solid oxide away from the casting area.

[0036] Suction equipment may include:

[0037] Control valves to allow regulation of the suction pressure for each volume in the vicinity of each brush.

[0038] Suction equipment may include:

[0039] Main control valve to allow total suction pressure regulation of both volumes in the vicinity of the brushes. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to describe the present invention in more detail, some illustrative examples will be given with reference to the accompanying drawings, in which:

[0041] Figure 1 is a schematic side view of an embodiment of a twin-roll continuous casting machine of the utility model;

[0042] Figure 2 yes Figure 1 An enlarged partial cross-sectional view of a portion of a twin-roll continuous casting machine;

[0043] Figure 3 yes Figure 1 and Figure 2 A side view of a housing of an embodiment of a solid oxide extraction apparatus for a twin roll continuous caster; and

[0044] Figure 4 Twin roll continuous casting machine Figures 1 to 3 Schematic diagram of an embodiment of a solid oxide extraction apparatus. DETAILED DESCRIPTION

[0045] The following description of the embodiments of the twin-roll continuous caster and the casting method is not the only embodiment of the twin-roll continuous caster and the casting method suitable for producing steel strip according to the present invention.

[0046] All other embodiments obtained by ordinary technicians in this field based on the described embodiments of the present invention without any creative efforts shall fall within the protection scope of the present invention.

[0047] Unless otherwise defined, technical or scientific terms used in the present disclosure shall have the meanings commonly understood by those of ordinary skill in the art in the field of the present invention.

[0048] Reference now Figure 1 and Figure 2 , a twin roll continuous casting machine is shown, which includes a main frame 10 that rises from the plant floor and supports a pair of counter-rotatable casting rolls 12 mounted in modules in a roll box (not shown). The casting rolls 12 are mounted in the roll box to facilitate operation and movement as described below. The roll box facilitates the rapid movement of the casting rolls 12 ready for casting from a setup position to an operational casting position as a unit in the continuous casting machine, and the rapid removal of the casting rolls 12 from the casting position when the casting rolls 12 are to be replaced. There is no particular configuration of the roll box that is desired, as long as it performs the function of facilitating the movement and positioning of the casting rolls 12 as described herein.

[0049] The twin roll continuous casting machine includes a pair of counter-rotatable casting rolls 12 having laterally positioned casting surfaces 12A to form a roll gap 18 therebetween. Molten metal, more specifically, molten steel described further below, is supplied from a ladle 13 to a metal delivery nozzle 17 (core nozzle) located between the casting rolls 12 and above the roll gap 18 by a metal delivery system (14, 16 described further below). The molten metal so delivered forms a casting pool 19 of molten metal supported on the casting surfaces 12A of the casting rolls 12 above the roll gap 18. The casting pool 19 is closed at the ends of the casting rolls 12 by a pair of side closure plates or side baffles 20 (at Figure 2 The upper surface of the casting pool 19 (often referred to as the "meniscus" level) can be raised above the lower end of the delivery nozzle 17 so that the lower end of the delivery nozzle 17 is immersed in the casting pool 19. The casting zone includes the addition of a protective atmosphere above the casting pool 19 to inhibit oxidation of the molten metal in the casting zone.

[0050] The ladle 13 is generally of conventional construction supported on a rotating turret 40. For metal delivery, the ladle 13 is positioned above a movable tundish 14 in a casting position to fill the tundish 14 with molten metal. The movable tundish 14 may be positioned on a tundish car 66 that is capable of transferring the tundish 14 from a heating station (not shown) to the casting position where the tundish 14 is heated to approximately casting temperature.

[0051] The movable tundish 14 may be equipped with a sliding door 25 that can be actuated by a servo mechanism to allow molten metal to flow from the tundish 14 through the sliding door 25 and then through the refractory outlet shield 15 to a transition piece or distributor 16 in the casting position. From the distributor 16, the molten metal flows to a transfer nozzle 17 located between the casting rolls 12 and above the roll gap 18.

[0052] The side dams 20 may be made of a refractory material, such as zirconia graphite, graphite alumina, boron nitride, boron nitride-zirconia, or other suitable composite materials. The side dams 20 have a face surface capable of physically contacting the casting rolls 12 and the molten metal in the casting pool 19. The side dams 20 are mounted in side dam holders (not shown) that are movable by side dam actuators (not shown), such as hydraulic or pneumatic cylinders, servo mechanisms, or other actuators, to engage the side dams 20 with the ends of the casting rolls 12. In addition, the side dam actuators are capable of positioning the side dams 20 during casting. The side dams 20 form an end closure for the molten metal pool on the casting rolls 12 during the casting operation.

[0053] As in Figure 2 As can be best seen in FIG. 1 , the twin roll continuous caster also includes a pair of stainless steel wire brushes 51 disposed adjacent respective rolls 12 of the pair of casting rolls 12 such that they can contact respective casting surfaces 12A of the casting rolls 12 at the side opposite to the roll gap 18 before the casting surfaces of the casting rolls further rotate and enter the casting pool 19 of molten metal. The brushes 51 are arranged to rotate in the same direction as the direction of rotation of the casting rolls 12. Each brush 51 is configured to at least partially clean the casting surface 12A of the casting rolls 12 during the casting phase. In particular, the brushes 51 are configured to disengage at least a portion of any solid oxide formed on the casting surface 12A of the casting rolls 12 and provide oxide thickness control on the casting surface. The brushes 51 may be segmented if desired, but typically one brush extends across the casting roll surface 12A of each casting roll 12. The brushes 51 are described in more detail in U.S. Patent 7,299,857 in the name of the applicant, and the disclosure in the U.S. Patent is incorporated herein by cross-reference.

[0054] Figure 1A twin roll continuous caster is shown producing a cast strip 21, wherein the cast strip initially moves downward, then travels upward through a hot box to a guide table 30, the hot box containing a controlled protective atmosphere, such as containing nitrogen, to minimize strip oxidation, and the cast strip moves through the guide table 30 to a pinch roll stand 31 including pinch rolls 31A. Upon leaving the pinch roll stand 31, the cast strip 21 may pass through a hot rolling mill 32, which includes a pair of work rolls 32A and backup rolls 32B, forming a gap capable of hot rolling the cast strip 21 delivered from the casting rolls 12, wherein the cast strip 21 is hot rolled to reduce the strip to a desired thickness, improve the strip surface, and improve strip flatness. The work rolls 32A have working surfaces on the work rolls 32A that are associated with a desired strip profile. The hot rolled cast strip 21 is then transferred to a run-out table 33 within a cooling station 97 where it can be cooled by contact with a coolant (such as water) supplied via a spray nozzle 90 or other suitable device and by convection and radiation. In any case, the cooled hot rolled cast strip 21 passes through a second pinch roll stand 91 having a pair of rollers 91A that provide tension to the cast strip 21 during strip cutting. Finally, the cooled hot rolled cast strip 21 is then coiled, where a shear at a shearing station 98 periodically cuts the strip upstream of the coiler to form a desired length of strip for each coil.

[0055] As described below, the casting rolls 12 are internally water-cooled so that as the casting rolls 12 rotate in opposite directions, the shell solidifies on the casting surface 12A as the casting surface 12A moves into contact with and through the casting pool 19 with each rotation of the casting rolls 12. The shell is brought together at the nip 18 between the casting rolls 12 to produce a cast strip product 21 that is conveyed downwardly from the nip 18. The cast strip product 21 is formed from the shell at the nip 18 between the casting rolls 12 and is conveyed downwardly and moves downstream as described above.

[0056] In operation, the cast strip exits the roll gap at a temperature of about 1400°C or higher. To prevent oxidation and scaling of the strip, the metal strip is cast downwardly into a housing 27 that supports a protective atmosphere just below the casting rolls in the casting position. The housing 27 may extend along the path of the cast strip up to the first pinch roll stand 31 and may extend along the path of the cast strip up to the hot rolling mill 32 to reduce oxidation and scaling.

[0057] After the hot rolling mill 32, the rolled thin strip then enters a cooling station 97 where the strip is cooled by water as it moves on an output table 33 in the cooling station 97, the water being delivered by a spray nozzle 90 of a plurality of rows of water spray assemblies extending across the output table 33. Although the spray nozzles atomize the coolant to produce a spray, any other coolant discharge port may be employed in place of the spray nozzles in any embodiment. In addition to producing a spray, other types of coolant discharge ports may discharge a non-atomized coolant stream.

[0058] Finally, the cooled hot-rolled strip is coiled in a coiler 92 .

[0059] about Figure 1 and Figure 2 Further details of the described twin-roll continuous casting machine can be found in the specification of Chinese Patent Application No. 201780029304.2 in the name of the applicant, and the disclosure in this specification is incorporated herein by cross-reference.

[0060] from Figure 2 As best seen in the Figure 1 , the twin roll caster also includes an embodiment of an apparatus for extracting solid oxide, typically in the form of dust particles, from the vicinity of the casting rolls of the twin roll caster (hereinafter referred to as a solid oxide extraction apparatus), which has been dislodged from the casting surfaces 12A of the casting rolls 12 by the rotating wire brushes 51. As described above, when the brushes 51 become saturated with dust, the dislodged solid oxide may cause the solid oxide to accumulate on the surfaces of the casting rolls 12, and this may be undesirable, for example resulting in poor solidification caused by the influence of the excess oxide on the casting roll surfaces.

[0061] refer to Figures 2 to 4 , the solid oxide extraction equipment includes the following components.

[0062] A housing that covers each wire brush 51, for example in the form of a metal fairing 53 (or other suitable removable housing). The purpose of the fairing 53 is to at least substantially confine solid oxide (typically in the form of dust particles) that is dislodged from the casting surface 12A of the casting roll 12 by the wire brush 51 to a volume near the wire brush 51, while allowing axial wire brush movement and helping to promote uniform suction over the length of the wire brush 51.

[0063] The fairing 53 includes at least one suction exhaust port 55 for removing air (with entrained solid oxide) from the volume, with typically up to 12 exhaust ports present along the length of the fairing 53 .

[0064] A suction system, including a fan 57 (typically up to 45 kW) and an extraction hose 59 or other suitable conduit connecting the fan 57 and the suction exhaust 55 together. In use, the suction system disengages solid oxides (typically in the form of dust particles) from the volume near the wire brush 51 at a temperature below 300°C and transports the solid oxides to a solid capture system, such as a baghouse (not shown). The suction volume and pressure are typically 1 to 6 kPa and up to 10,000 m 3 / hr, which is combined in a pipe size of 8-16". Typically, the suction system is configured to apply at least substantially constant suction across the width of each casting roll.

[0065] A damper control valve 61 allows regulation of the suction pressure both entering and leaving the extraction, and a main control valve 63 allows regulation of the total suction pressure. Manual Differential pressure gauges 64 are located at both the inlet and outlet pipes, and a main line analog differential pressure sensor 65 is used for suction pressure control and monitoring.

[0066] The above-described embodiments of the solid oxide extraction apparatus of the present invention are effective and robust apparatus for removing dislodged solid oxide from the vicinity of the casting rolls.

[0067] While the principles and modes of operation of the present invention have been explained and illustrated with respect to particular embodiments, it must be understood that the invention may be practiced otherwise than as specifically explained and illustrated without departing from the spirit or scope of the invention.

Claims

1. A twin-roll continuous casting machine, characterized in that: include: a pair of casting rolls capable of counter-rotating so that casting surfaces of the casting rolls travel through a casting pool of molten steel supported thereon and toward and through a nip between the casting rolls to produce a steel strip that exits the nip in a casting zone of the twin roll caster; a brush capable of rotating in contact with the casting surface of each casting roll after the casting surface passes through the nip and before the casting surface rotates back into the casting pool to dislodge at least a portion of the solid oxide formed on the casting surface; and A suction device is provided for extracting the detached solid oxide from the casting zone.

2. The twin-roll continuous casting machine according to claim 1, characterized in that: The suction device comprises: a housing that confines the detached solid oxide to a volume in the vicinity of each brush, and A suction system is operable to extract the dislodged solids from the volume adjacent each brush and transport the solid oxide away from the casting area.

3. The twin-roll continuous casting machine according to claim 1, characterized in that: The suction device comprises: a housing in the form of a metal fairing configured to cover each brush to confine solid oxide that breaks away from the casting surfaces of the casting rolls to a volume proximate each brush, wherein the housing has at least one suction discharge port; and A suction system includes a fan and an extraction hose connecting the fan and the suction outlet, the suction outlet being configured to remove solid oxide by suctioning the solid oxide from the volume near each brush and transporting the solid oxide away from the casting area.

4. The twin-roll continuous casting machine according to claim 2 or 3, characterized in that: The suction device comprises: Control valves to allow regulation of the suction pressure for each volume in the vicinity of each brush.

5. The twin-roll continuous casting machine according to claim 4, characterized in that: The suction device comprises: Main control valve to allow total suction pressure regulation of both volumes in the vicinity of the brushes.

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