JP3497170B2 - Method and apparatus for double belt casting of strip - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a continuous metal casting method and apparatus, and more particularly to a metal strip casting method and apparatus.

Continuous casting of thin metal strips has been used with little success. In general, the application of conventional continuous metal strip casting processes has been limited to relatively few types of alloys and products. It has been found that as the alloy content of various metals increases, the as-cast surface quality deteriorates. As a result, many alloys have been fabricated using the ingot method.

In the case of aluminum, relatively pure aluminum products such as foils can be continuously strip cast on a commercial basis. Similarly, mainly in the case of building products, building products can also be continuously strip cast, since the surface quality is less critical than other aluminum products such as cans. However, as the alloy content of aluminum increases, surface quality problems emerge,
Strip casting is generally unsuitable for use in making many aluminum alloy products.

Many strip casting machines have been proposed in the past. One conventional system is the double belt strip casting system, but such a system is not widely accepted for casting many metals, especially metal alloys having a wide freezing range. In such a dual belt strip casting facility, two moving belts are provided between the belts to define a moving mold for the metal to be cast. Cooling of the belt is typically effected by contacting the cooling fluid with the side of the belt opposite the side in contact with the molten metal. As a result, the belt is exposed to extremely high thermal gradients. That is, it has a molten metal that contacts the belt on one side and, for example, a water coolant that contacts the belt on the other side. The top and bottom of the belt are neither flat, because the belt is distorted by the dynamically unstable thermal gradient. Therefore, the produced product has areas of segregation and porosity as described below.

Leone says "Proceedings Of The Aluminum Associatio
n, Ingot and Continuous Casting Process Technology
Seminar For Flat Rolled Products, Vol.II, May 10,198
At 9 ", the lack of belt stability and modest heat flow leads to some problems. First of all, solidification of the molten metal begins and strip shell coherency begins. If any distortion of the belt occurs after reaching, the resulting increase in the gap between the belt and the strip at the distortion will cause strip shell reheating, or at least partially. It reduces the shell growth rate, which results in reverse segregation within the strip which produces dendrite eutectic exudates on the surface, and in the case of alloys with medium or long freezing ranges, the liquid metal is strained. Of the strip to the faster solidification portion of the adjacent strip, which causes shrinkage on the surface of the strip. Is allowed to form a bulk area of contracted porous strip. 該塊 shaped area, making subsequent severe surface streaks or rolls surface to generate cracks on the rolling surface.

As a result, the double belt casting process is not generally accepted as alloy casting when surface is important, such as in can manufacturing. Various improvements have been made so far. For example, U.S. Pat.Nos. 3,937,270 and 4,002,197
Belt preheating as described in U.S. Pat. No. 3,79.
A continuously applied and removed aliquot layer as described in US Pat. No. 5,269,5, a moving endless side dam as described in US Pat. No. 4,586,559 and US Pat. No. 4,061,177.
No. 4,061,178 and No. 4,193,440 with improved belt cooling. None of these techniques have been widely accepted.

An additional approach to continuous belt casting of steel is
It is described in US Pat. No. 4,561,487. The approach utilizes a pair of counter rotating belts. Here, one belt is cooled but does not come into contact with the metal being cast. Thus, molten steel is supplied to the surface of the belt just before the metal being cast passes between the belts downwards and around the support pulleys. On the other hand, the approach adopted in the patent avoids thermal distortion effects caused by large thermal gradients when the cooling fluid is supplied to one side of the belt and the other side is in contact with hot metal. But presents another problem. The supply of molten metal to the belt just as it passes around the support pulley means that the molten metal must be cooled very quickly. Otherwise, the molten metal would flow off the belt and into the area around the equipment, endangering the operator. In addition, the '487 patent
Casting the molten metal on a single belt, the second belt
Used only as a "hanger" belt to keep the cast ribbon in contact with the cooled belt.

Another approach to belt casting is U.S. Pat.
293 and published European application 0,181,566. In the techniques described in both publications, the cooling liquid is applied to the belt surface on the side where the metal is cast, whether the belt is in contact with the metal or not. Therefore, the heat transferred from the molten metal to the belt is largely removed by the contact of the cooling fluid when the belt is not in contact with the metal being cast, avoiding the formation of a large thermal gradient.

Another previously proposed continuous casting method is known as block casting. In this technique, multiple cooling blocks are mounted adjacent to each other on a pair of opposing tracks. Each set of cooling blocks rotates in opposite directions to form a casting cavity between each block. Molten metal such as aluminum alloy is introduced into the nest. The liquid metal in contact with the cooling block is cooled and solidified by the heat capacity of the cooling block itself. Therefore, block casting differs in both concept and approach from continuous belt casting. Block casting relies on the heat transfer provided by a cooling block. Therefore, heat is transferred from the molten metal to the cooling block in the casting area of the facility and extracted on the return loop. Block casters require precise dimensional control and prevent casting burrs (ie transverse metal burrs) caused by small gaps between blocks. Such cast burrs cause lacerations when the strip is hot rolled. As a result, maintaining good surface quality becomes difficult. Examples of such block casting methods are described in US Pat. Nos. 4,235,646 and 4,238,248.

Another technique proposed in continuous strip casting is the single drum casting machine. In a single-drum caster, molten metal is fed to the surface of a rotating drum, which is internally water cooled, and the molten metal is dragged over the drum surface to form a thin metal strip. The metal strip is cooled in contact with the drum surface. Strips are often too thin for many applications, resulting in poor free surface quality due to slow cooling and small shrinkage cracks. Various improvements have been proposed in such a drum casting machine. For example, U.S. Patent Nos. 4,793,400 and 4,9
No. 45,974 suggests drum grooving to improve surface quality. U.S. Pat. No. 4,934,443 recommends metal oxides on the drum surface to improve surface quality.
Various other techniques are also disclosed in U.S. Pat. Nos. 4,771,819 and 4,97.
9,557, 4,828,012, 4,940,077 and 4,955,4
No. 29 is proposed.

Another approach used in the prior art is
Use of a twin drum casting machine, U.S. Pat.No. 3,790,21
6, No. 4,054,173, No. 4,303,181 or No. 4,751,958. Such a device includes a source of molten metal that is fed to the space between a pair of counter-rotating internally cooled drums. The twin-drum casting approach, unlike the other techniques described above, exerts a compressive force on the solidified metal by the drum, reducing the heat of the alloy shortly after freezing. Twin-drum casters are the most widely marketed and used, but have significant drawbacks. That is, not a few twin-drum casters have much lower yields than have been achieved with many of the conventional equipment described above. That is, the twin-drum casting approach provides acceptable surface quality in casting high-purity aluminum (eg, foil), but when used in casting aluminum with high alloy content and wide freezing range, It has the drawback of poor surface quality. Another problem encountered with the use of twin drum casters is that there is centerline segregation of the alloy due to deformation during solidification.

Therefore, there is a need for an apparatus and method for high speed continuous casting of thin metal strips having improved surface quality as compared to currently used methods.

Co-pending application 07/902997 (filed June 23, 1992), incorporated herein by reference, includes continuous casting of metal strips, particularly metal strips formed from aluminum having a high alloy content. A method and apparatus have been described that overcomes many of the limitations of the prior art described above. The method and apparatus described in that application uses the heat sink capability of the belt in a generally horizontal casting zone. Here, substantially all of the heat transferred from the metal being cast to the belt is removed from the belt while the belt is not in contact with the metal being cast. Thus, the method and apparatus described in the aforementioned application minimizes the formation of thermal gradients across the thickness of the belt that would otherwise cause conventional belt distortion. The present invention seeks to further improve this method and apparatus to improve heat transfer and reduce metal cracking.

A particular object of the present invention is to provide molten metal to the curved surface of the belt at the inlet pulley rather than to straight sections, thus eliminating belt distortion when processing metals such as aluminum with high alloy content. A further reduction is to provide an improved method and apparatus for improving heat transfer and strip surface quality.

Another object of the invention is a further improved method in which molten metal is fed to the curved surface of the belt to solidify in front of the nip of the inlet pulley while the nip of the pulley is not replaced by the solidified metal. And to provide a device. Positive control of the gap between the nip of the inlet side pulley, in combination with coagulation before the nip,
The nip creates a compressive force to be applied to the cast strip to minimize belt distortion and reduce metal cracking.

A further object of the present invention is to provide a method and apparatus for continuous casting of thin metal strips that provides improved surface quality even when treating metals such as aluminum having high alloy contents.

These and other objects and advantages of the present invention will become more apparent in the detailed description of the invention that follows.

SUMMARY OF THE INVENTION The concept of the present invention is attributed to a continuous belt metal strip casting method and apparatus utilizing a pair of continuous belts formed of thermally conductive materials positioned adjacent to each other to define a casting zone therebetween. To do. The belt is
Mounted on at least two pulley means, each passing around the pulley means. Thus, each belt defines a curved surface which is curved with respect to the pulley means and a substantially flat, preferably horizontal surface after the belt has passed around the pulley means. The apparatus further uses means for supplying molten metal to the curved surface of the belt. Thus, the molten metal solidifies on the surface of the belt in the casting zone to form a cast strip of metal, transferring heat from the molten metal and the cast metal to the belt. Thereafter, the belt remains out of contact with either the molten metal or the cast strip, and substantially all of the heat transferred from the molten metal and the cast strip to the belt is removed from the belt.

Thus, in the concept of the invention, the molten metal is supplied on the curved area of the belt around the pulley means. In the conventional belts according to the state of the art, after the belt has passed around the inlet pulley, the metal is fed to the straight section of the belt, at the same time being cooled from the back side and solidification takes place.
The supply of molten metal to the curved areas of the belt increases mechanical stability and resistance to thermal distortion of the belt during casting, resulting in a more uniform thickness and better thermal contact between the strip and the belt. Has been found to have the effect of maintaining the quality of the cast strip and consequently improving the quality of the surface of the cast strip.

In the most preferred embodiment of the invention, the apparatus includes a pair of belts, each disposed substantially horizontally and one positioned above the other to define a generally horizontal casting zone between the belts. The term "horizontal" as used herein refers to the placement of the belt within an angle of ± 30 degrees. In some instances it may be desirable to orient the belt at an angle within such a range. The molten metal is supplied from a conventional tundish equipped with nozzle means through which the molten metal flows in a generally horizontal flow. Thus, the molten metal from the nozzle means passes within the space defined between the belts ahead of the nip of the pulleys so that it solidifies in the casting zone defined by the nozzle means and the belt passing around each pulley. It flows as a substantially horizontal flow between and. In an exemplary embodiment of the invention, the cast strip substantially solidifies in the time it takes to reach the nip of the pulley on which the belt rests.
The horizontal flow of molten metal flowing into the space between the belts at the end of the nip is maintained so that the molten metal is in constant contact with the surfaces of both belts as the metal is being cast.

The present invention further discloses that the use of a floating backup roll on the top side of the straight portion of the casting zone enhances heat transfer and isolates downstream mechanical obstacles from the critical solidification zone at the casting machine inlet. To do.

Further, the inventive concept appears in a metal strip casting method and apparatus for continuous belt casting. here,
Since the molten metal is cast on the curved surfaces of a pair of opposing belts, the solidification of the metal occurs before the nip between the inlet pulleys in the casting zone, where the inlet pulleys are on the cast metal strip. Apply a compressive force to the strip to elongate it. A characteristic of solidification that precedes the nip and is subsequently subjected to a compressive force by the nip is to improve the surface quality of the cast metal strip and reduce the tendency of the strip to crack.

In an embodiment of the invention, a pair of belts are used that are mounted adjacent to each other, each mounted on at least two pulleys, defining a casting zone therebetween. Since each belt passes around the entrance pulley,
Each belt defines a curved surface that is curved about the pulley and a substantially flat, preferably horizontal surface after the belt has passed around the pulley.

In this embodiment of the invention, means are provided for supplying molten metal to the curved surface of the belt, the molten metal solidifying on the opposite curved surface of the belt in the casting zone preceding the nip of the inlet pulley. , Forming a cast strip of metal having a thickness greater than the thickness of the nip.
As a result, the cast metal strip is advanced to the nip where compressive forces are applied to elongate the cast metal strip, improving the surface properties of the strip and reducing the tendency for cracking.

In the preferred embodiment of the invention, each belt is heated by heat transfer from the cast metal to the belt. Therefore, the heat transferred to the belt is removed almost entirely from the belt while the belt is not in contact with either the molten metal or the cast strip.

In this embodiment of the invention, the method and apparatus of the invention utilizes positive control means to control the gap in the casting zone at the nip between the inlet pulleys for the double belt. Such control can be achieved by various mechanisms. For example, it is possible to prevent the deviation of one of the shafts from the other by using a means for applying a tension between the shafts of the entrance pulley. Such means are in the form of similar mechanical means, such as a hydraulic cylinder controlling the gap between the shafts of the inlet pulley or a screw jack controlling the relative position of the shaft of the inlet pulley with respect to the other shaft. Good. Alternatively, a spacer block and a tensioning member that prevents dislocation of one shaft mounted on these shafts with respect to the other shaft may be used to obtain the desired space between the shafts of the inlet pulley. .

Thus, in an embodiment of the invention, molten metal is supplied to the belt on a curved area around the pulley means. In a conventional conventional belt caster, metal is fed to the straight section of the belt after the belt has passed through the inlet pulley,
At the same time, it was cooled from the back side and solidified. As already mentioned, the supply of molten metal to the curved areas of the belt increases the mechanical stability and thus the resistance of the cast belt to thermal distortion, thus providing a more uniform thickness and between strip and belt. Has been found to maintain good thermal contact of the cast strip and consequently improve the quality of the surface of the cast strip.

Positive control of the nip between the inlet pulleys in the casting zone provides improved surface quality of the cast strip. Without limiting the invention, positive control of the nip between the inlet pulleys enhances heat transfer as the molten metal solidifies and minimizes the tendency to form such dendroid eutectic leaches.

In addition, positive control of the nip between the inlet pulleys almost eliminates cracks in the cast metal strip. Although this is also not a limitation of the invention, controlling the casting zone at the nip between the inlet pulleys also causes the cast metal strip formed prior to the nip to be subjected to compressive force by the inlet pulley, thus Elongate cast metal strips. Since the cast metal strip is always under a different compression than the tension in the casting zone, tension-induced cracking of the strip is minimized.

The concept of the present invention can be used for strip casting of most metals including steel, copper, zinc and lead, but is particularly well suited for casting thin aluminum alloy strips while solving the drawbacks of the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic explanatory view of a casting method and apparatus according to the present invention.

FIG. 2 is a perspective view of an example of the casting apparatus according to the present invention.

FIG. 3 is a sectional view showing a state in which molten metal enters the apparatus shown in FIGS. 1 and 2.

FIG. 4 is a detailed view of the device for mechanically supporting the belt of the device of FIGS.

FIG. 5 is a top view showing an example of the edge containing means used in the present invention.

FIG. 6 is a schematic explanatory diagram of a casting method and apparatus based on the concept of another feature of the present invention.

  FIG. 7 is a perspective view of the device schematically shown in FIG.

FIG. 8 is a cross-sectional view showing a state where the molten metal of the embodiment shown in FIGS. 6 and 7 enters.

DETAILED DESCRIPTION OF THE INVENTION The apparatus used to practice the invention is best shown in FIGS. 1, 2 and 3. As shown, the device includes a pair of endless belts 10 and 12 mounted on a pair of upper pulleys 14 and 16 and corresponding lower pulleys 18 and 20 of FIG. Each pulley is mounted for rotation about its respective shaft 21, 22, 24 and 26 in FIG. The pulleys are of a suitable heat resistant type and either or both of the upper pulleys 14 and 16 are driven by suitable motor means. The motor means are not shown for simplicity. The same applies to the lower pulleys 18 and 20. Belts 10 and 12
Each of the is an endless belt, preferably made from a metal that exhibits low or no reactivity with the metal being cast. Many suitable metal alloys known to those skilled in the art can be used. Good results are obtained when using steel and copper alloy belts.

The pulleys are positioned one above the other with a casting gap therebetween, as shown in FIGS.
In the preferred embodiment of the invention, the gap is sized to correspond to the desired thickness of the metal strip being cast. Therefore, the thickness of the metal strip during casting is
Determined by the size of the nip between belts 10 and 12 passing over pulleys 14 and 18 along a line passing through the axes of pulleys 14 and 18 orthogonal to 10 and 12. As described in the earlier pending application, the thickness of the strip being cast is limited by the heat capacity of the belt between which the casting takes place.

The molten metal to be cast is supplied to the casting zone through suitable metal supply means 28 such as a tundish. The internal width of the puddle 28 corresponds to the width of the product to be cast and has a width up to that of the belts 10 and 12. The puddle 28 includes a metal feed delivery casting nozzle 30 for delivering a horizontal stream of molten metal to the casting zone between the belts 10 and 12. Such a hot water pool
It is conventional in strip casting.

Therefore, the nozzle 30 as best shown in FIG.
With belts 10 and 12 immediately adjacent to nozzle 30,
Define the casting zone. A horizontal stream of molten metal flows into the casting zone. Therefore, the casting zone between the curved surfaces of each belt 10 and 12 is filled to the nip of the pulleys 14 and 18 by the flow of molten metal flowing from the nozzles in a substantially horizontal direction. The molten metal begins to solidify, almost solidifying at the point where the cast strip reaches pulleys 14 and 18. A belt 10 which passes a horizontal stream of molten metal through pulleys 14 and 18 and
By feeding up to the casting zone in contact with 12 curved surfaces, strain is limited, thus maintaining better thermal contact between the molten metal and each belt, and the quality of the top and bottom surfaces of the cast strip. Improve.

According to the concept of the invention, the casting device of the invention comprises:
It includes a pair of cooling means 32 and 34 positioned in the casting gap between the belts 10 and 12 opposite the portion of the endless belt that is in contact with the metal being cast. Thus, the cooling means 32 and 34 cool the belts 10 and 12, respectively, immediately after the belts 10 and 12 have passed over the pulleys 16 and 20 and before contact with the molten metal. In the most preferred embodiment as shown in FIGS. 1 and 2, coolers 32 and 34
Are located on the return routes of belts 10 and 12, respectively. In this embodiment, the cooling means 32 and 34 are conventional cooling means such as cooling fluid nozzles positioned to spray the cooling fluid directly inside and / or outside the belts 10 and 12 to cool the entire thickness of the belts. Means are all right. In the preferred embodiment, the endless belts 10 and 12 have pulleys 14
As they pass over and 18 they frictionally engage endless belts 10 and 12, respectively, to clean metal or other debris from the surfaces of endless belts 10 and 12 prior to receiving molten metal from pool 28. Scratch brush means 36 and 38
May be desirable in some cases.

Thus, in practicing the present invention, molten metal flows horizontally from a puddle through a casting nozzle 30 into a casting zone defined between belts 10 and 12, where belts 10 and 12 are: It is heated by heat transfer from the cast strip to belts 10 and 12. The cast metal strip remains between the belts 10 and 12 and is carried by the belts 10 and 12 until they return beyond the centerlines of the pulleys 16 and 20, respectively. Therefore, in the return loop,
Cooling means 32 and 34 cool belts 10 and 12, respectively,
Almost all of the heat transferred to the belt in the casting zone is removed. The belts pass over pulleys 14 and 18 and after being cleaned by scratch brushing means 36 and 38, again approach each other to define a casting zone.

The most preferred supply of molten metal from the puddle through the casting nozzle 30 is shown in more detail in FIG. As shown, the casting nozzle 30 is formed from an upper wall 40 and a lower wall 42 defining a central opening 44 therebetween, the width of which is that of the belts 10 and 12 as they pass around pulleys 14 and 18, respectively. May extend well beyond width.

The ends of the walls 40 and 42 of the casting nozzle 30 are approximately at the tips of the surfaces of the casting belts 10 and 12, respectively.
Together with 12, a casting cavity or zone 46 is defined. Molten metal flows into the casting zone 46 through the central opening 44. The molten metal in the molten cavity 46 is belt 10
And 12 transfers its heat to the belts 10 and 12 while simultaneously cooling the molten metal to form a solid strip 50 maintained between the casting belts 10 and 12.

In the preferred embodiment of the present invention, it is defined as the distance between the sufficient setback (first contact 47 of molten metal 46 and nip 48 which is defined such that the inlet pulleys 14 and 18 are closest). ) Should be provided prior to nip 48 to allow near complete solidification. In a conventional belt caster, the molten metal contacts the belt after the nip 48 in straight sections. Thus, in the present invention, solidification occurs almost completely before nip 48, whereas in the prior art solidification by the belt caster does not begin until after nip 48.

In the present invention, the importance of freezing in front of the nip 48 is that the belts 10 and 12 are much more stable when tensioned on the curved surface of the pulley and, as in the prior art, the molten metal in straight sections. Belt 46 at the beginning 10
And the strain is much less than it would be in contact with 12 and 12. Further, in the practice of the invention, the belt
If 10 and 12 initially contact the molten metal 46, the belt
An instantaneous high thermal gradient occurs above 10 and 12. Tension is applied to each belt, and the pulley 14 and
Being well supported by 18, the belt is even more stable against distortions resulting from momentary thermal gradients. In addition, the space between the belts when they first contact the molten metal is much larger than the gap corresponding to the thickness of the cast strip. As a result, any distortion in the belt at this position does not significantly affect the metal being cast. Before the belts 10 and 12 reach the nip 48, the high thermal gradient is sufficiently dissipated that the strain that would have occurred as the belts approached the nip is reduced.

As will be appreciated by those skilled in the art, the thickness of strip that can be cast is related to the thickness of belts 10 and 12, the return temperature of the casting belt and the exit temperature of the strip and belt. In addition, the strip thickness depends on the metal being cast. Use 0.08 inch thick steel belt
The 0.100 inch thick aluminum strip has a return temperature of 300 ° F and an outlet temperature of 800 ° F. The relative relationship between belt and strip thickness and exit temperature is described in detail in co-pending application 07 / 902,997. For example,
To cast a 0.100 inch thick aluminum strip using a 0.06 inch thick steel belt, the exit temperature is 900 ° F and the return temperature is 40 ° C when the return temperature is 300 ° F.
At 0 ° F, the outlet temperature is 960 ° F.

One of the advantages of the method and apparatus of the present invention is that it does not require the use of a thermal barrier coating on the belt typically used in the prior art to reduce heat flow and stress. Eliminating the use of fluid cooling on the backside of the belt as it contacts hot metal in the casting zone significantly reduces the thermal gradient and results in films that occur when the critical heat flux is exceeded. Eliminates the problem of boiling (thin film boiling). The method and apparatus of the present invention further comprises a cold framework, a cold belt area (1)
Minimize the state before the metal enters and (2) in three positions on each of the two sides of the casting zone of the belt.
These conditions cause significant belt distortion.

In addition, the concept of the present invention eliminates the need to use a sizing agent that was used in the prior art to prevent sticking of cast metal strips to either belt.

For certain applications it is desirable to use one or more belts having longitudinal grooves in the surface of the belt that contacts the metal being cast. Such grooves are described in U.S. Pat. No. 4,934,44.
Used in single-drum casting machines as described in No. 3.

In the preferred embodiment of the invention, belts 10 and 12
Is supported by a plurality of pulleys positioned to maintain both belts in a manner such that the belts are substantially flat, at least in a first position in the casting zone. This is shown in FIG. 4, where pulley 18 and belts 10 and 12 face each other and define a casting cavity defining solid strip 50. Thus, the lower pulley 52 supports the belt 12 as it passes over the pulley 18.
As shown in FIG. 4, each of these pulleys is mounted for rotation about an axis that extends parallel to and below belt 12 and maintains belt substantially flat. However, it helps support both the weight of the belt and the weight of the metal strip 50 during casting.

Corresponding set of backup roll 54, upper belt
Mounted in contact with the belt 10, it exerts sufficient pressure on the belt 10 to act to maintain the belt 10 in contact with the strip 50 when the molten metal is transformed into a solid strip. In a preferred embodiment of the invention, the backup roll is in contact with the upper belt but is not fixed, but rather floats. Depending on the application, some backup rolls 54 may be used in a floating state and other backup rolls 54 may be used in a fixed state.

In the preferred embodiment, the upper set of backup rolls 54 are set in vertical slots so that gravity closes the gaps and causes belts 10 and 12 and the cast strip to roll.
It acts to maintain thermal contact with 50. These backup rolls isolate the solidifying metal from mechanical vibrations in the downstream equipment and improve heat transfer, thus cooling and strengthening the strip 50.

According to another embodiment of the present invention, the inlet pulley 14 and
Means for engaging 18 to prevent relative displacement of these pulleys. Any device suitable for rigidly fixing the relative positions of the pulleys 14 and 18 can be used. 5 and 6 show a simple mechanism including sleepers 45 and 47 on each shaft 21 and 24 of inlet side pulleys 14 and 18, respectively, secured to each other by a tensioning member 49. The tension member may be fixed or adjustable. Good results are obtained by simply using the turnbuckle 49 as a tensioning member to prevent relative displacement of the shafts 21 and 24. As will be appreciated by those skilled in the art, various other more sophisticated tensioning members may be used as well. For example, a hydraulic cylinder can be used as a tension member for preventing relative displacement of the shafts 21 and 24. The use of such a hydraulic cylinder offers the advantage of being more adjustable, so that the tension can be conveniently changed depending on the metal being applied and cast.

As in the previous embodiments, the importance of freezing in front of the nip 48 in the present invention is that the belts 10 and 12 are more stable when held in tension on the curved surface of the pulley, It is much less strained than if the belts 10 and 12 and the molten metal 46 first contacted in a straight section as in the prior art. Further, in an embodiment of the present invention, a high instantaneous thermal gradient occurs on belts 10 and 12 when first contacting molten metal 46. Each belt has a pulley 14
Being well supported under tension by 18 and 18, the belt is more stable against distortions resulting from the instantaneous thermal gradients. In addition, the space between the belts when they first contact the molten metal is much larger than the gap between the belts which corresponds to the thickness of the cast strip. As a result, belt distortion does not significantly affect the metal being cast at this location. The high thermal gradients are well dissipated before the belts 10 and 12 reach the nip 48, eliminating the distortion that would occur as the belts approach the nip.

The importance of freezing or solidification in front of the nip 48 can also be seen from the fact shown in FIG. The metal that solidifies between the curved surfaces in the casting zone prior to the nip has a size and thickness greater than the size and thickness of the corresponding nip itself. Since the metal has a larger dimension than the nip as the solidified metal is advanced to the nip 48, the nip 48 exerts a compressive force on the cast metal strip to lengthen it and improve the surface properties as well as the strip. It also reduces the tendency for cracking. In addition, after coagulation,
During the solidification point and nip, the compressive force itself exerted on the cast metal strip also provides good thermal contact between the cast metal strip and the belt.

The amount of compressive force is not critical to the invention. It has been found that the compression force must be high enough to provide good thermal contact between the cast metal strip and the belt as well as high enough to elongate the cast metal strip. The lengthening is preferably sufficient to ensure that the cast metal strip is in a compressed state separate from the tensioned state as it is conveyed from the nip 48 through the remaining casting zones.
As mentioned above, maintaining the cast strip under compressive force has been found to act to minimize the cracks that would have occurred if the cast strip were kept under tension. Generally, it is desirable that the lengthening rate is relatively small, generally 15% or less, most preferably
It is 10% or less. Good results are obtained when the lengthening rate is 5% or less.

As will be appreciated by those skilled in the art, the thickness of strip that can be cast is related to the thickness of belts 10 and 12, the return temperature of the casting belt and the exit temperature of the strip and belt. In addition, the strip thickness depends on the metal being cast. Use 0.08 inch thick steel belt
The 0.100 inch thick aluminum strip has a return temperature of 300 ° F and an outlet temperature of 800 ° F. The relative relationship between belt and strip thickness and exit temperature is described in detail in co-pending application 07 / 902,997. For example,
To cast a 0.100 inch thick aluminum strip using a 0.06 inch thick steel belt, the exit temperature is 900 ° F and the return temperature is 40 ° C when the return temperature is 300 ° F.
At 0 ° F, the outlet temperature is 960 ° F.

In addition, the concept of the present invention eliminates the need to use a sizing agent that was used in the prior art to prevent sticking of cast metal strips to either belt.

For certain applications it is desirable to use one or more belts having longitudinal grooves in the surface of the belt that contacts the metal being cast. Such grooves are described in U.S. Pat. No. 4,934,44.
Used in single-drum casting machines as described in No. 3.

In accordance with another embodiment of the present invention, at times, along each edge of the belt, it is provided with a metal containing means for preventing the metal from flowing laterally outward from the belt. desirable. Therefore, conventional edge dams, such as those used in twin drum casting machines, can be used for this purpose. A suitable edge dam is shown in Figure 5.
Shown as a pair of edge dam members 56 positioned adjacent the edges of belts 10 and 12. The edge dam member 56 comprises a pair of walls extending from the surfaces of the belts 10 and 12 at substantially right angles to prevent molten metal from flowing outwardly from the casting zone defined between the belts. For this reason, the edge dam member 56 is such that the molten metal supplied by the casting nozzle 30 faces the belts 10 and 12.
It has a leading edge member 58 placed in front of the casting nozzle 30 so as to be confined between. Other edge dams may be used as well, as will be appreciated by those skilled in the art.

It will be understood that various changes and changes in detail of construction may be made without departing from the spirit of the invention and particularly within the spirit defined in the appended claims.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-248749 (JP, A) JP-A-50-157225 (JP, A) JP-A-1-150442 (JP, A) Actual development Sho-63- 29650 (JP, U) Actual development Sho 62-6953 (JP, U) Patent 3260487 (JP, B2) US patent 4817702 (US, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B22D 11 / 06 340 B22D 11/00

Claims (8)

(57) [Claims] 1. A strip casting apparatus for metal strips by continuous belt casting, comprising: (a) a pair of continuous belts made of a heat conductive material, one placed on top of the other; and (b) for each belt. At least 2 including the inlet side pulley
One pulley means, each belt being mounted on said pulley means and passing around said inlet side pulley, such that each belt has a curved surface curved with respect to said inlet side pulley and each belt A substantially flat surface after passing around the entrance pulley for the belt, the curved surface and the flat surface of each belt defining a casting zone between the belts and each A belt, a pulley means defining a nip therebetween; and (c) means for supplying molten metal to the curved surface of each belt in the casting zone between the belts before the metal reaches the belt nip. A means for solidifying the molten metal to form a cast strip of metal having a thickness greater than the distance between the nips; and (d) controlling the spacing of the nip and the direction in which the cast strip moves after exiting the nip. Compression of A means for applying a compressive force to the cast strip at the nip sufficient to extend the substantially solidified cast strip so as to receive and minimize cracking of the cast strip; and (e) positioned adjacent the belt, Cooling means for cooling the belt when the belt is not in contact with either the molten metal or the cast metal, the cooling means including the molten metal and the cast metal when the belt is not in contact with either the metal or the cast strip. Metal strip casting equipment that reduces the temperature of the belt by removing almost all of the heat transferred from the casting metal to the belt. 2. The apparatus of claim 1, wherein the means for supplying molten metal comprises a substantially horizontal nozzle positioned to deposit a substantially horizontal stream of molten metal on the curved surface of the endless belt. An apparatus having a bathing means. 3. The apparatus of claim 1 including edge containment means for preventing molten metal from flowing past the edge of the belt. 4. The apparatus according to claim 1, wherein each belt defines a substantially flat and horizontal surface after passing around the pulley means, and the flat and horizontal surface is maintained in a tensioned state. Equipment. 5. In a metal casting method by continuous belt casting, (a) a pair of endless belts made of a heat conductive material is in a plane defined by an axis of an inlet pulley substantially perpendicular to the belts. Moving the nip around a pair of inlet pulleys defining therebetween to define a casting zone between the belts and defining curved surfaces that are curved as each belt passes over the inlet pulleys; (B) supplying molten metal to the curved surface of each belt and solidifying in the casting zone to form a strip of cast metal having a thickness greater than the distance between the nips; (c) casting Advancing the strip to the nip and applying sufficient compressive force in the nip to cause the length of the almost solidified cast strip to minimize cracking of the cast strip after it exits the nip. A step of compressing the cast strip in the transverse direction as, and before the belt when the belt is not in contact with any of the molten metal or cast metal receives additional molten metal,
Cooling the belt to remove substantially all heat transferred from the molten metal and cast metal. 6. The method according to claim 5, wherein the molten metal is fed to a substantially horizontal melting zone. 7. The method of claim 5, wherein the molten metal is fed to the melting zone as a substantially horizontal stream. 8. The method according to claim 5, wherein the metal is an aluminum alloy.