JP6921983B2 - Continuous casting equipment and method - Google Patents

Description

The present invention generally relates to continuous casting of metals, and more particularly to twin belt casting systems and methods for continuous casting of metals.

For example, continuous casting of light metal alloys such as aluminum alloys has usually been carried out in continuous casters such as twin roll casters and twin belt casters. The bi-roll casters generally include a pair of opposing rotating rolls to which the molten metal is fed. The centerline of the roll lies in a vertical or generally vertical plane through the area of the minimum gap between the rolls, called the "nip", whereby the cast strip is formed in a generally horizontal path. However, there are other twin roll casting machines that produce strips in an angled or vertical direction.

On the other hand, as shown in FIG. 1, the twin belt casters such as the twin belt casting apparatus 10 are generally supported by a pair of upper pulleys 16 and 18 and a corresponding pair of lower pulleys 20 and 22. Includes a pair of endless belts 12, 14. (Pulleys 16 and 20 are also referred to herein as nip pulleys or nip rolls. Pulleys 18 and 22 are also referred to herein as downstream pulleys or downstream rolls.) Nip rolls 16 and 18 and above and below. The arrangement of 20, 22 defines the mold zone A, which is bounded by the belts 12, 14. The gap between the belts 12 and 14 determines the thickness of the cast strip 24. The molten metal 26, which is fed directly into the nip via the feeding device 28 having the nozzle 30, is confined between the moving belts 12 and 14 and solidifies as it is carried. The heat from the solidifying metal is drawn to the parts of the belts 12 and 14 adjacent to the metal to be cast by various means known in the art.

Existing twin-roll and twin-belt casting systems are generally suitable for what can be considered normal performance, but with minimal strip thickness and metallurgical quality, including surface quality. Improvements are desired without sacrificing productivity. For example, in the case of double roll casting where metal is cast against opposing nip rolls, the length of the mold is limited to a short distance in front of the contacts of the opposing rolls and the diameter of the mold is used in the feeder. Limited by practical considerations such as space that must be made possible. These limits on roll diameter and perimeter limit casting speed, roll life and metallurgical quality.

In the case of double belt casting as described above, the molten metal is usually at or immediately after the contact where the belt transitions from the curved path defined by the nip roll or pulley to the planar path of the mold region. It is delivered on the belt. The belt allows for an extended mold length compared to double roll casting, but the initial solidification occurs in the zone immediately after the nip, where the belt is the most unstable. In particular, with reference to FIG. 2, this phenomenon is known as belt "takeoff" when the belt 14 transitions from a curved path around the nip roll 20 to a planar path in the mold zone. It can occur in zone 34 (referred to as the belt take-off zone), and in a planar traveling path, belts 12 and 14 are supported by backup rolls 32. As used herein, "belt takeoff" is the natural tendency of a pulled belt to move away from its rounded or flat guide surface when subjected to bending moments or other forces. Point to. As is easily recognized, the metallurgical quality can be adversely affected in areas where the belt is unstable, especially in this zone immediately after the nip, especially when the cast alloy has a wide solidification range. be.

Moreover, in double-belt casting in which the molten metal is fed into substantially parallel sections of the mold, the casting thickness is also limited to thicker sections, usually more than 15 millimeters thick. Therefore, in many cases, additional post-casting work, such as rolling, is required to achieve a thickness of less than 15 millimeters, which increases the overall cost. In addition, the solidification of the inner layers of these relatively thick cast sections is significantly slowed by the thermal resistance of the surface layers, which can be particularly detrimental if the cast alloy has a wide solidification range. ..

With the above in mind, it enables the production of thinner metal strips and provides improved surface quality than previously possible using existing systems and equipment without sacrificing productivity. There is a need for systems and methods of double-belt continuous casting of metals to achieve the metallurgical quality of the casting strips, including.

An object of the present invention is to provide a double belt continuous casting apparatus.
Another object of the present invention is to provide a double belt continuous casting apparatus that improves thermal conductivity over the thickness of the casting strip as compared to existing equipment.

Another object of the present invention is to provide a double belt continuous casting apparatus for producing thinner metal strips than previously possible.
Another object of the present invention is to provide a twin-belt continuous casting apparatus that improves the metallurgical quality of cast strips, including surface quality.

Another object of the present invention is to provide a double belt continuous casting apparatus that facilitates the use of thicker belts than previously possible.
Another object of the present invention is to provide a method of double belt continuous casting that minimizes belt takeoff.

Another object of the present invention is to provide a method of double belt continuous casting which allows the production of strips less than about 7 mm thick.
Another object of the present invention is to achieve the above object without sacrificing productivity.

These and other objectives are achieved by the present invention.

According to one embodiment of the present invention, there is provided a continuous casting apparatus for casting metal strips. The continuous casting apparatus includes a first belt supported by a first upstream pulley and a first downstream pulley, a second belt supported by a second upstream pulley and a second downstream pulley, and melting. A first mold support section located behind the first belt in the middle of the first upstream pulley and the first downstream pulley in the mold region to which the metal is supplied, and a second upstream pulley. And includes a mold area defined by a second mold support section located behind the second belt in the middle of the second downstream pulley. The first mold support section supports the first belt in the mold region and defines the shape of the first belt, and the second mold support section supports the second belt in the mold region and the second. Define the shape of the belt. At least one of the first mold support section and the second mold support section includes a transition portion and a generally planar portion downstream of the transition portion. The transition portion has a variable radius configured to receive the molten metal from the metal feeding device.

According to another embodiment of the present invention, there is provided a method of continuously casting a metal strip. In this method, the first belt is placed on the first upstream pulley and the first downstream pulley, the second belt is placed on the second upstream pulley and the second downstream pulley, and the first method is performed. A first mold support section is placed behind the first belt in the middle of the upstream pulley and the first downstream pulley, and behind the second belt in the middle of the second upstream pulley and the second downstream pulley. By arranging a second mold support section in the mold region, at least one of the first mold support section and the second mold support section is a first upstream pulley and a second. Forming a mold region with a curved transition portion downstream of the upstream pulley and a generally planar portion downstream of the curved transition portion, and the molten metal on the curved transition portion. Including sending.

According to yet another embodiment of the present invention, there is provided a continuous casting apparatus for casting metal strips. The continuous casting apparatus includes a first belt supported by a first upstream pulley and a first downstream pulley, a second belt supported by a second upstream pulley and a second downstream pulley, and a second belt. A first mold support section located behind the first belt between the 1 upstream pulley and the 1st downstream pulley, and a 2nd intermediate between the 2nd upstream pulley and the 2nd downstream pulley. Includes a mold area defined by a second mold support section located behind the belt. The mold region includes a first zone, a second zone downstream of the first zone, and a third zone downstream of the second zone.

The present invention is better understood by reading the following description of non-limiting embodiments with reference to the accompanying drawings below.

It is a simplified schematic diagram of the twin belt caster of the prior art. It is a detailed schematic diagram of a part of the prior art twin-belt casters showing the phenomenon of belt take-off in the mold zone of the casters. It is a simplified schematic diagram of the twin belt casting apparatus by one Embodiment of this invention. It is an enlarged detailed view of the mold support section of the twin belt casting apparatus of FIG. 3 according to one embodiment of the present invention.

With reference to FIG. 3, a twin belt casting apparatus 100 according to an embodiment of the present invention is shown. As shown in FIG. 3, the casting apparatus 100 includes a first endless belt 112 supported by a first upstream pulley or roll 116 and a first downstream pulley or roll 118, and a second upstream. Includes a second endless belt 114 supported by a pulley or roll 120 and a second downstream pulley or roll 122. Each roll is attached to rotate about its longitudinal axis and acts to rotate, guide, and / or pull the belts 112, 114. Either or both of the upper rolls 116, 118 and the lower rolls 120, 122 can be driven by a suitable motor (not shown). The belts 112, 114 are endless and are preferably formed from a metal that is less or less reactive with the metal to be cast. As shown in FIG. 3, the upstream rolls 116, 120 are positioned up and down at some distance to allow room for positioning the metal feeder 128 in space and rolls. defining a plane _{P 1} extending through the respective tangent 116 and 120.

Molten metal 126 is to be cast, as described in detail herein below, horizontal flow device 100 of the mold in the region of the molten metal at a point 129 located downstream from the plane P ₁ It is supplied through a feeder 128 having a nozzle 130 positioned to deliver to. In one embodiment, the molten metal is confined at and across the mold inlet, or across the mold inlet, or across the mold region, using edge confinement means that eliminates the need to move the edge damming block. Can be done. For example, as described below, using a static edge dam located between the first belt 112 and the second belt 114, a first of the mold regions of the device. Adjacent to at least one of a zone, a second zone and a third zone can result in side confinement of molten metal.

As further shown in FIG. 3, the casting apparatus also includes a pair of opposing mold support sections 132, 134 positioned along the path of the moving belts 112, 114, which include the belts 112, 114. In addition to supporting each, at least a part of the traveling path of the moving belts 112 and 114 is defined. Mold supporting section 132 and 134, between them, define a mold area 136 located downstream from the _{P 1.} Importantly, the mold region 136 is not in close proximity to the nip rolls 116, 120, but away from the upstream rolls 116, 120 and downstream rolls 118, 122, upstream rolls 116, 120 and downstream rolls 118, It is formed by separate mold support sections 132, 134 located approximately intermediate between 122. As described herein below, one or both of the mold support sections 132, 134 shall include a large radius curved section supporting the belts 112, 114 to which the molten metal 126 is fed. Can be done. This structure substantially provides an effective pressing force that adapts the shape of the belt to the shape of the curved mold support sections 132, 134, even when the belt is lightly pulled around the mold support sections 132, 134. Allows you to add to. Embodiments herein show a support structure that supports the moving belt and defines the shape of the moving belt in the mold region 136 as a solid "mold support section", but is a broader aspect of the invention. Other support devices, such as backup rolls or an array of platens, are also used to define the support of the moving belts 112, 114 and to define the shape of the moving belts 112, 114 in the mold region 136, without departing from. Can be done.

Referring to FIG. 4, one or both of the mold support sections 132, 134 are adjacent to a first small radius portion 138, a small radius portion 138 that defines a first zone (zone I) of belt passage. Along with, a second large radius transition portion 140 defining a second zone of belt passage (Zone II) and a third zone of belt passage (Zone III) adjacent to and defining a large radius portion 140. A third substantially planar portion 142 can be included. In one embodiment, the small radius portion 138 and the large radius portion 140 can have a radius of about 0.4 meters to about 1.5 meters, in which case the large radius portion 140 is of the small radius portion 138. Unlike the radius, it has a radius greater than the radius of the small radius portion 138. In one embodiment, the small radius portion 138 can have a constant or variable radius of curvature of about 0.3 meters to about 1 meter, and the large radius portion 140 can have about 0.5 meters to about 25 meters. Can have a constant or variable radius of curvature of. In one embodiment, the large radius portion 140 can have a radius of curvature that gradually increases (ie, as the gradient decreases) from the small radius portion 138 to the planar portion 142 (ie, variable or variable). curvature radius). In one embodiment, the large radius portion 140 defining Zone II through the belt can have a radius of curvature that changes continuously from the upstream end to the downstream end.

Importantly, the presence of a large radial portion or section 140 (ie, Zone II) near the planar portion of the mold 136 or the transition to section 142 causes the belt to transition from a curved path to a planar path, comparison. The device at the mold inlet point 129, where the molten metal is first supplied, eliminating or substantially reducing the possibility of belt takeoff at the tangent of a small, constant radius roll 120 (or equivalent thereof). At least separate from any of the 100 areas of potential belt takeoff. In addition, the geometry of the curved portions of the mold support sections 132, 134 functions to support the belt 114 (or 112) in the previously unsupported belt takeoff region 34. As a result, the molten metal is fed, the very stable properties of this mold inlet region (including the mold inlet point 129) are orders of magnitude thinner than normally possible with existing twin belt casters. Allows casting. For example, the structure of the twin-belt casting apparatus 100 of the present invention allows casting of thin casting sections with a thickness of less than about 7 mm, more preferably less than about 5 mm, which is the existing double-belt casting. The device has not been successfully achieved so far.

In addition, a small radius portion 138 (Zone I) preceding the large radius portion 140 (Zone II) accommodates the metal feeder 128 and associated support structures.
Zone III, defined by the planar portions 142 of the mold support sections 132, 134, serves its role as mold force control, cooling control and stabilization of the belt from thermomechanical forces.

In one embodiment, the radii of the respective zones of the mold support sections 132, 134 can be based on mathematical functions such as parabolas, hyperbolas or other higher order functions. In one embodiment, connecting several sections can include using variable radii, continuous radii and intermittent straight sections to fit different shapes together like a tangent. .. In one embodiment, the shape and contour of the mold support sections 132, 134 can be designed to fit the natural contour of the belt in the belt take-off zone 34 during operation (this is the level of heat input). , Velocity / dynamics, tension level, belt thickness, belt material, alloy / solidification nuances, etc.). In certain embodiments, the mold 136 can be configured so that its physical shape can be changed during casting of the metal or between casting campaigns. In one embodiment, the upper mold support section 132 may have a different shape, contour or structure than the lower mold support section 134.

The radius of the converging belts 112, 114 is increased or decreased (by increasing or decreasing the radius of the rounded portion 138 of the mold support sections 132, 134) to further consolidate the solidification zone within the apparatus 100. It is further intended to be able to accommodate moving or bringing the solidification zone closer to the metal feed chip 130. In one embodiment, the generally parallel planar portions of the mold 136, defined by the opposing planar portions 142 of the mold support sections 132, 134, do not guide the hot work to the cooling metal. As the strip 124 shrinks, it can be slightly tapered and adjusted as needed to provide uniform cooling from both belts. In one embodiment, the upper mold support section 132 or the lower mold support section 134 is spring-loaded or otherwise (eg, mechanical) towards the other of the upper mold support section or the lower mold support section. Target, fluid, electrical, etc.) can be biased. The outlet end of the mold can also be adjusted to shorten or extend the effective cooling region of the casting apparatus 100 without the need to change the casting rate.

In connection with the above, during operation, the molten metal 126 is fed onto the belt in a zone where the pulled belts 112, 114 converge, which are supported on a relatively large radius by means other than nip rolls. For example, in one embodiment, the molten metal 126 is fed over a large radius portion of the belt path defined by a large radius portion 140 (zone II) of the mold support sections 132, 134. The combination of belt tension and belt curvature provided by the support profiles of mold support sections 132, 134 provides a very stable belt condition in the zone where initial solidification occurs. Therefore, thinner strips can be cast at faster solidification rates, achieving metallurgical improvements compared to existing twin-belt casting machines, especially for alloys with a wide solidification range. In addition, the ability to cast thinner strips reduces or eliminates the need for subsequent rolling to the finished gauge, which reduces both capital and operating costs.

In addition to the advantages described above, the casting apparatus 100 of the present invention is much more than the casting belts used in existing belt casters with relatively small, constant diameter nip pulleys or their equivalents. It also allows the use of thick cast belts. In particular, the actual belt thickness is limited by the minimum radius that must fit under tension. Generally this means that the diameter of the pulleys (or their equivalents) in the belt casting machine should be approximately 400-600 times the thickness of high-strength low-alloy steel belts at ambient temperature. Any smaller proportions of belts and outer fibers can be stressed beyond their yield point. For a belt with a thickness of 1.2 mm, this is converted to a pulley diameter of 600 mm (0.6 m). Under conditions of high thermal conductivity, the outer fibers of the steel belt are more stressed and require a larger pulley radius.

Thicker than previously possible by using mold support sections 132, 134 with large radius portions 140 and feeding over such large radius portions 140 rather than smaller radius pulleys or nip rolls. A belt can be used. This is especially desirable because thicker belts have higher heat capacity and promote higher thermal conductivity, which is especially helpful when casting alloys with a wide solidification range. Typical in existing belt casters, for example by using a thick belt of about 2 mm or more, while maintaining belt stability, for example by combining thin cast sections with a thickness of less than about 7 mm. It is possible to achieve thermal conductivity that is orders of magnitude higher than that. In one embodiment, the belt can be in the range of about 1 mm to 4 mm thick. This also allows alloys with a very wide solidification range to be cast at high production rates in twin belt casters, with excellent metallurgical and surface qualities.

In addition to the advantages described above, using the mold support sections 132, 134 to support the moving belt and to form the mold region 136 downstream of the upstream pulley supports it virtually without friction. Allows the belt to expand and contract on the mold support section. This is in stark contrast to existing devices where expansion and contraction of the moving belt at the rotating inlet / upstream pulley can contribute to instability. In fact, the present invention substantially separates the mold region 136 from the upstream pulley or roll that drives the belt.

The embodiments described above disclose that the mold sections 132, 134 include a first rounded portion and a second rounded portion leading to a generally planar portion, although the mold sections 132, 134 However, it is intended that they may optionally be formed with a single curved or rounded portion upstream of the generally planar portion to which the molten metal is fed. In one embodiment, this rounded transition portion can have a radius that gradually increases from the upstream end of the mold section to the planar portion of the mold section. In yet another embodiment, the mold sections 132, 134 have two or more having a constant or variable radius, such as three, four, five or more rounded portions leading to a generally planar portion. Can have a separate radius-shaped or curved portion of.

In connection with the above, certain combinations of thicker belts and thinner casting strips use the belt's natural thermal capacitance as a conductive cooling means at a much higher level than experienced in existing casting systems. Allows, which allows for faster solidification of cast strips. In prior art systems, heat is generated in the mold zone due to the limited ratio of heat capacity of thinner belts (eg, less than about 1.2 mm) to thicker strips (eg, more than about 15 mm). Actively removed from the belt in and in close proximity to the mold zone. On the contrary, as intended by the present invention, a thicker belt (up to about 4 mm) casting thinner strips (about 2 mm to 6 mm) provides a more favorable ratio of heat capacity, which is The heat conduction of the belt allows the initial solidification of the cast strip to be achieved more rapidly. Thus, in this case, heat removal from the belt can be achieved by a combination of both belt cooling near and away from the mold region, or completely away from the mold region.

Although the present invention has been shown and described with respect to its detailed embodiments, those skilled in the art will be able to make various modifications without departing from the scope of the invention and will be able to use equivalents for that element instead. It is understood that it can be done. In addition, modifications can be made to the teachings of the invention to adopt specific circumstances or materials without departing from the essential scope of the invention. Accordingly, the invention is not limited to the particular embodiments disclosed in the description detailed above, and the invention is intended to include all embodiments that fall within the scope of the present disclosure.

Claims (13)

A continuous casting machine that casts metal strips.
A first belt (112) supported by a first upstream pulley (116) and a first downstream pulley (118), and
A second belt (114) supported by a second upstream pulley (120) and a second downstream pulley (122), and
A mold region (136) to which the molten metal is supplied, which is located behind the first belt (112) in the middle of the first upstream pulley (116) and the first downstream pulley (118). It is located behind the second belt (114) in the middle of the first mold support section (132) and the second upstream pulley (120) and the second downstream pulley (122). With a mold region (136) defined by a second mold support section (134),
The first mold support section (132) supports the first belt (112) and defines the shape of the first belt (112) in the mold region (136).
The second mold support section (134) supports the second belt (114) and defines the shape of the second belt (114) in the mold region (136).
Each of the first mold support section (132) and the second mold support section (134) has a transition portion (140) and a planar portion (142) downstream of the transition portion (140). Including
The transition portion (140) has a variable radius for receiving molten metal from the metal feeding device, and the variable radius of the transition portion (140) is opposite to the planar portion (142). From the upstream end of the transition portion (140) to the downstream end of the transition portion (140),
The planar portion facing (142) is Ri tapered der,
The continuous casting device is a horizontal casting apparatus, wherein the first mold support section (132) is you positioned vertically above the second mold support section (134), the continuous casting apparatus. The continuous casting apparatus according to claim 1, wherein the variable radius of the transition portion (140) gradually increases from the upstream end of the transition portion (140) to the planar portion (142). At least one of the first mold support section (132) and the second mold support section (134) further comprises a first rounded portion (138) having a constant radius of curvature.
The transition portion (140) is positioned between the first rounded portion (138) and the planar portion (142).
The transition portion (140) extends over the entire range of the transition portion (140) from a point adjacent to the first radius-shaped portion (138) to a point adjacent to the planar portion (142). The continuous casting apparatus according to claim 1, which has a radius larger than the rounded portion (138) of 1. At least one of the first mold support section (132) and the second mold support section (134) further comprises a first rounded portion (138) having a constant radius of curvature.
The transition portion (140) is positioned between the first rounded portion (138) and the planar portion (142).
The transition portion (140) extends over the entire range of the transition portion (140) from a point adjacent to the first radius-shaped portion (138) to a point adjacent to the planar portion (142). The continuous casting apparatus according to claim 2, which has a radius larger than that of the rounded portion (138) of 1. The continuous casting apparatus according to claim 3, wherein the radius of the first rounded portion (138) is 0.3 meters to 1 meter. The first belt (112) and the second belt (114) have a thickness of 1 mm to 4 mm, respectively.
The continuous casting apparatus according to claim 1, wherein the metal strip has a thickness of less than 7 mm and at least one of them. It is a method of continuously casting metal strips.
A step of arranging the first belt (112) on the first upstream pulley (116) and the first downstream pulley (118), and
A step of arranging the second belt (114) on the second upstream pulley (120) and the second downstream pulley (122), and
A first mold support section (132) is placed behind the first belt (112) in the middle of the first upstream pulley (116) and the first downstream pulley (118), and the second mold support section (132) is arranged. A mold region (136) is provided by placing a second mold support section (134) behind the second belt (114) between the upstream pulley (120) and the second downstream pulley (122). In the step of forming, each of the first mold support section (132) and the second mold support section (134) is the first upstream pulley (116) and the second upstream pulley (120). ), A curved transition portion (140) downstream of the curved transition portion (140), and a planar portion (142) downstream of the curved transition portion (140). Is tapered, with steps to form the template region (136),
A step of feeding the molten metal onto the curved transition portion (140) is provided.
Each of the first mold support section (132) and the second mold support section (134) further includes a first rounded portion (138) having a constant radius of curvature.
The curved transition portion (140) is positioned between the first rounded portion (138) and the planar portion (142).
The curved transition portion (140) is positioned downstream of a plane extending through the tangents of the first upstream pulley (116) and the second upstream pulley (120).
The curved transition portion (140) changes from the upstream end of the curved transition portion (140) to the downstream end of the curved transition portion (140), which is the opposite of the planar portion (142). It has a radius,
The method utilizes a horizontal casting apparatus, in which the first mold support section (132) is located vertically above the second mold support section (134) . The method of claim 7, wherein the radius of the curved transition portion (140) gradually increases from the upstream end of the curved transition portion (140) to the planar portion (142). The method according to claim 7, wherein the radius of the first rounded portion (138) is 0.3 meters to 1 meter. A continuous casting machine that casts metal strips.
A first belt (112) supported by a first upstream pulley (116) and a first downstream pulley (118), and
A second belt (114) supported by a second upstream pulley (120) and a second downstream pulley (122), and
A first mold support section (132) located behind the first belt (112) in the middle of the first upstream pulley (116) and the first downstream pulley (118), and said. A mold defined by a second mold support section (134) located behind the second belt (114) between the second upstream pulley (120) and the second downstream pulley (122). With area (136)
The mold region (136) includes a first rounded portion (138), a transition portion (140) downstream of the first rounded portion (138), and a downstream portion of the transition portion (140). The flat portion (142) includes a flat portion (142) in the shape of a taper.
The first rounded portion (138) has a constant radius of curvature and has a radius of curvature.
Said transition portion (140) opposite to said planar portion (142), from the upstream end of the transition portion (140), have a curvature radius varying from the downstream end of the transition portion (140),
The continuous casting apparatus is a horizontal casting apparatus, and the first mold supporting section (132) is located above the second mold supporting section (134) in the vertical direction . The continuous casting apparatus according to claim 10, wherein the changing radius of curvature of the transition portion (140) gradually increases from the upstream end of the transition portion (140) to the planar portion (142). The continuous casting apparatus according to claim 11, wherein the radius of the first rounded portion (138) is 0.3 meters to 1 meter. The continuous casting apparatus according to claim 12, wherein the radius of the transition portion (140) is 0.5 to 25 meters.

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