TECHNICAL FIELD
This invention pertains to thermal management system for use in a continuous casting molten metal mold, including a heat distribution or temperature management system for larger castparts such as ingots.
BACKGROUND OF THE INVENTION
Metal ingots, billets and other castparts may be formed by a casting process which utilizes a vertically oriented mold situated above a large casting pit beneath the floor level of the metal casting facility, although this invention may also be utilized in horizontal molds. The lower component of the vertical casting mold is a starting block. When the casting process begins, the starting blocks are in their upward-most position and in the molds. As molten metal is poured into the mold bore or cavity and cooled (typically by water), the starting block is slowly lowered at a pre-determined rate by a hydraulic cylinder or other device. As the starting block is lowered, solidified metal or aluminum emerges from the bottom of the mold and ingots, rounds or billets of various geometries are formed, which may also be referred to herein as castparts.
While the invention applies to the casting of metals in general, including without limitation, aluminum, brass, lead, zinc, magnesium, copper, steel, etc., the examples given and preferred embodiment disclosed may be directed to aluminum, and therefore the term aluminum or molten metal may be used throughout for consistency even though the invention applies more generally to metals.
While there are numerous ways to achieve and configure a vertical casting arrangement, FIG. 1 illustrates one example. In FIG. 1, the vertical casting of aluminum generally occurs beneath the elevation level of the factory floor in a casting pit. Directly beneath the casting pit floor 101a is a caisson 103, in which the hydraulic cylinder barrel 102 for the hydraulic cylinder is placed.
As shown in FIG. 1, the components of the lower portion of a typical vertical aluminum casting apparatus, shown within a casting pit 101 and a caisson 103, are a hydraulic cylinder barrel 102, a ram 106, a mounting base housing 105, a platen 107 and a bottom block 108 (also referred to as a starting head or starting block base), all shown at elevations below the casting facility floor 104.
The mounting base housing 105 is mounted to the floor 101a of the casting pit 101, below which is the caisson 103. The caisson 103 is defined by its side walls 103b and its floor 103a.
A typical mold table assembly 110 is also shown in FIG. 1, which can be tilted as shown by hydraulic cylinder 111 pushing mold table tilt arm 110a such that it pivots about point 112 and thereby raises and rotates the main casting frame assembly, as shown in FIG. 1. There are also mold table carriages which allow the mold table assemblies to be moved to and from the casting position above the casting pit.
FIG. 1 further shows the platen 107 and starting block base 108 partially descended into the casting pit 101 with castpart 113 (which may be an ingot or a billet being partially formed. Castpart 113 is on the starting block base 108, which may include a starting head or bottom block, which usually (but not always) sits on the starting block base 108, all of which is known in the art and need not therefore be shown or described in greater detail. While the term starting block is used for item 108, it should be noted that the terms bottom block and starting head are also used in the industry to refer to item 108, bottom block is typically used when an ingot is being cast and starting head when a billet is being cast.
While the starting block base 108 in FIG. 1 only shows one starting block 108 and pedestal, there are typically several of each mounted on each starting block base, which simultaneously cast billets, special tapers or configurations, or ingots as the starting block is lowered during the casting process.
When hydraulic fluid is introduced into the hydraulic cylinder at sufficient pressure, the ram 106, and consequently the starting block 108, are raised to the desired elevation start level for the casting process, which is when the starting blocks are within the mold table assembly 110.
The lowering of the starting block 108 is accomplished by metering the hydraulic fluid from the cylinder at a pre-determined rate, thereby lowering the ram 106 and consequently the starting block at a pre-determined and controlled rate. The mold is controllably cooled during the process to assist in the solidification of the emerging ingots or billets, typically using water cooling means. Although the use of a hydraulic cylinder is referred to herein, it will be appreciated by those of ordinary skill in the art that there are other mechanisms and ways which may be utilized to lower the platen.
There are numerous mold and casting technologies that fit into mold tables, and no one in particular is required to practice the various embodiments of this invention, since they are known by those of ordinary skill in the art.
The upper side of the typical mold table operatively connects to, or interacts with, the metal distribution system. The typical mold table also operatively connects to the molds which it houses.
When metal is cast using a continuous cast vertical mold, the molten metal is cooled in the mold and continuously emerges from the lower end of the mold as the starting block base is lowered. The emerging billet, ingot or other configuration is intended to be sufficiently solidified such that it maintains its desired profile, taper or other desired configuration. In some casting technologies, there may be an air gap between the emerging solidified metal and the permeable ring wall, while in others there may be direct contact. Below that, there is also a mold air cavity between the emerging solidified metal and the lower portion of the mold and related equipment.
Once casting is complete, the castparts, billets in this example, are removed from the bottom block.
One of the primary concerns and objectives in continuous molten metal casting is achieving the highest castpart quality and the increased smoothness of the outer surface is certainly a part of the desired quality. Large castparts such as ingots are typically reduced to usable stock by running them through a rolling mill wherein the castpart is rolled through rolling stands until the castpart is reduced to the desired thickness (which may be the thickness for aluminum cans for example). A large castpart will typically be run through numerous rolling operations in order to achieve a metal from which aluminum parts such as cans and other stock can be manufactured. If the outer surface of the ingot starts with undesirably rippled, rough, cracked surfaces and/or other imperfections, those portions of the rolled aluminum are normally removed, resulting in substantial scrap or waste. It has also been found that poor ingot surfaces can greatly increase crack rates in aluminum alloys, especially those used in the aerospace industry, typically 2XXX and 7XXX type alloys. The industry has long recognized that a higher quality castpart, such as one with a smoother outer surface, has reduced cracking and other waste as the castpart is processed through a rolling mill for example.
The generation of excessive scrap during rolling normally requires that the scrap be placed in a furnace, melted back down to molten metal and then run through another casting process. As will be appreciated by those of ordinary skill in the art, the generation of excess scrap increases the cost and energy consumption of the entire industry. It is estimated that hundreds of millions of dollars or more are lost through the generation of excessive scrap during the rolling process due to various imperfections in the castpart.
The industry has been searching for solutions and one of the long-standing teachings in the art is to focus on minimizing mold wall cooling to improve surface quality. For some alloys this cannot always be done effectively. As is described below and in reference to FIG. 2, in the continuous casting of molten metal the molten metal is introduced into the top of a mold cavity until the width of the mold cavity is filled.
The mold cavity includes a framework section where for large castparts, lubricant is dispersed on the mold wall to provide lubrication between the molten metal and the interior wall of the mold cavity. Below this lubricated portion of the mold framework is the chilling zone or section where there are typically numerous water or coolant apertures around the inner circumference of the interior wall of the mold cavity. The coolant may be applied to the castpart emerging at the bottom portion of the mold framework in streams, sheets, in spray and in other ways generally known in the art, thereby solidifying the castpart by chilling.
The area or zone around where coolant or water is applied to the molten metal may be referred to as the chill zone, which may include what the industry refers to as an initial mold chill zone, a slow chill zone and an advanced cooling distance zone. In the initial mold chill zone, some solidification of the molten metal begins to occur, and this is at a location above where the water coolant is applied to the solidified metal.
As shown and described later in FIG. 13, solidification generally begins to occur in the Initial Mold Chill Zone, sometimes referred to as the IMCZ. This is because the temperature of the inner mold wall surface is cooler due to cooling of the bore and the lubrication fluid, and thereby contributes to and creates the Initial Mold Chill Zone. As shown in FIG. 13, cooling from a water coolant freezes metal to some distance above the coolant apertures. This is referred to as the Advanced Cooling Distance.
As metal cools and begins to solidify in the Initial Mold Chill Zone, it shrinks away from the inner surface of the mold wall. At this point the Slow Chill Zone begins. When the metal has pulled from the mold wall it is no longer being cooled and starts to re-melt back to the mold wall where it freezes again. This creates an irregular castpart or ingot surface with varying metallurgical properties.
The applicant is unaware of any significant or successful prior efforts by others to optimize castpart quality and the smoothness of the outer surface of the castpart through the thermal management of the temperature differential on the mold cavity wall between the Initial Mold Chill Zone and the Slow Chill Zone. Again, the primary teaching in the art has been in the direction of attempting to minimize mold wall cooling not optimizing it.
It is therefore an object of some embodiments of this invention to improve the thermal management of the mold framework, and more particularly to thermally manage the mold cavity wall temperature differential between the Initial Mold Chill Zone and the area in and around the lower portion of the Slow Chill Zone to improve surface quality so as to reduce cracking, especially in aerospace type 2XXX and 7XXX alloys.
It has also been discovered that improving the thermal management of the casting mold in the corner sections or zone presents an area of opportunity to improve castpart quality. A material area of imperfections is the corner areas, as illustrated more fully in the examples shown in FIGS. 5 and 6. The prior art devices have generally uniformly distributed lubricant around the perimeter of the mold cavity wall.
The applicants have discovered a way to better thermally manage the mold cavity and the emerging castpart all the way around the castpart and particularly in the corner portions. Some embodiments of this invention are directed to thermally managing the entire interior perimeter of the mold cavity by creating a more effective temperature pattern or zones around the perimeter, such as by making the temperature characteristics more uniform around the entire perimeter, particularly in the corner zones thereof.
In the prior art mold cavities, the lubricant distribution around the mold cavity wall is typically uniform and does not alter the thermal pattern or temperature patterns or temperature differentials around the perimeter of the mold cavity wall. For example in the corner areas, due to the increased heat transfer characteristics from the increased mold metal mass per mold wall surface area, more heat may be absorbed by the mass of the mold in the corners. This may result in a reduced temperature or heat transfer pattern in the corner zones of the castparts leading to surface discontinuities and cracking, thus preventing fabrication of a useable castpart.
It is therefore an object of some embodiments of this invention to provide an improved thermal management system which provides a more uniform temperature pattern and temperature distribution around the perimeter of the mold cavity wall. It is also an object of some embodiments of this invention to provide an improved thermal management system around the perimeter of the mold cavity wall by reducing and/or better thermal managing the temperature and temperature patterns around the entire interior perimeter of the mold cavity.
Furthermore in some embodiments of the invention, other means at locations other than the corner zones of the mold cavity wall may be utilized as part of this thermal management system to improve castpart quality and reduce cracking. It is therefore another object of some embodiments of this invention to provide customized thermal management zones above the advanced cooling distance zone to provide a more desired temperature distribution and reduced temperature differentials around the perimeter of the mold cavity wall.
It is also an object of some embodiments of this invention to provide improved thermal management around the perimeter of the mold cavity wall. In some embodiments of the invention, this object may more particularly be to reduce the temperature differential or temperature delta around the perimeter of the mold cavity wall, and in particular between corner zones and other zones around the perimeter.
It is also an object of some embodiments of this invention to provide improved thermal management from the Advanced Cooling Distance Zone through the Initial Mold Chill Zone. In some embodiments this object may more particularly be to reduce the temperature differential or temperature delta from the coolant outlet to above the Initial Mold Chill Zone.
Other objects, features, and advantages of this invention will appear from the specification, claims, and accompanying drawings which form a part hereof. In carrying out the objects of this invention, it is to be understood that its essential features are susceptible to change in design and structural arrangement, with only one practical and preferred embodiment being illustrated in the accompanying drawings, as required.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are described below with reference to the following accompanying drawings.
FIG. 1 is an elevation view of a prior art vertical casting pit, caisson and metal casting apparatus;
FIG. 2 is a perspective view of one example of a mold framework in which embodiments of this invention may be utilized;
FIG. 3 is an elevation cross-sectional view of an exemplary mold framework configuration schematically depicting molten metal solidifying through the mold;
FIG. 4 is a perspective view of a partial section of an upper portion of a mold framework where lubrication may be introduced into the mold cavity through a mold sidewall;
FIG. 5 is a perspective elevation view of a typical castpart and schematically shows a lower zone with wavy or rippled corners compared to an upper portion without the same degree of wavy or rippled corners;
FIG. 6 is detail 6 from FIG. 5 and better illustrates the wavy or rippled corners;
FIG. 7 is a top view of a mold lubrication cover system, showing partially schematically the lubrication cover and lubrication holes in the mold framework with generally evenly distributed lubrication holes around the perimeter of the mold cavity;
FIG. 8 is a top view schematic representation of one example of a thermal management system with thermal management zones identified which may be utilized in practicing some embodiments of this invention;
FIG. 9 is a top view schematic representation of another example of a thermal management system with thermal management zones and exemplary flow rates which may be utilized in practicing some embodiments of this invention;
FIG. 10 is a top view schematic representation of another example of a thermal management system with thermal management zones which may be utilized in practicing some embodiments of this invention;
FIG. 11 is a top view schematic representation of another example, of a thermal management system with thermal management zones which may be utilized in practicing some embodiments of this invention;
FIG. 12 is an elevation detail of one example of a lower portion of a mold framework as molten metal solidifies passing through the mold cavity, illustrating various zones or stages of molten metal solidification;
FIG. 13 is an elevation view of an example of both the upper portion and lower portion of the internal surface of a mold framework, illustrating a thermal management system temperature differential between the Initial Mold Chill Zone and the Slow Chill Zone;
FIG. 14 is a perspective view of a partial section or corner of a mold framework, illustrating an example of one possible embodiment of a thermal management system contemplated by this invention;
FIG. 15 is detail 15 from FIG. 14;
FIG. 16 is a top view of a partial section or corner of the mold framework illustrating another embodiment of a thermal management system contemplated by this invention wherein a thermally dissimilar material is used for a section of the mold framework;
FIG. 17 is a top view of a partial section or corner of the mold framework illustrating another embodiment of a thermal management system contemplated by this invention wherein a unique or different lubrication hole distribution (or size), or a dissimilar oil with different thermal properties, is utilized to thermally manage a corner of a mold framework;
FIG. 18 is a top view of a partial section of the mold framework illustrating another embodiment of a thermal management system contemplated by this invention, wherein water coolant conduits are reconfigured within the mold framework to alter the temperature by altering the heat transfer characteristics of the corner portion of the mold framework; and
FIG. 19 is a top view of a partial section of the mold framework illustrating an example of one embodiment of a thermal management system contemplated by this invention, wherein the addition of heat is utilized to thermally manage a corner portion of the mold framework.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Many of the fastening, connection, manufacturing and other means and components utilized in this invention are widely known and used in the field of the invention described, and their exact nature or type is not necessary for an understanding and use of the invention by a person skilled in the art or science; therefore, they will not be discussed in significant detail. Furthermore, the various components shown or described herein for any specific application of this invention can be varied or altered as anticipated by this invention and the practice of a specific application or embodiment of any element may already be widely known or used in the art or by persons skilled in the art or science; therefore, each will not be discussed in significant detail.
The terms “a”, “an”, and “the” as used in the claims herein are used in conformance with long-standing claim drafting practice and not in a limiting way. Unless specifically set forth herein, the terms “a”, “an”, and “the” are not limited to one of such elements, but instead mean “at least one”.
It is to be understood that this invention can be utilized in connection with various types of metal pour technologies and configurations. It is further to be understood that this invention may be used on horizontal or vertical casting devices.
A mold or mold framework which may be utilized in embodiments of this invention therefore must be able to receive molten metal from a source of molten metal, whatever the particular source type is. The mold cavities in the mold must therefore be oriented in fluid or mold metal receiving position relative to the source of molten metal.
It will also be appreciated by those of ordinary skill in the art that embodiments of this thermal management system may and will be combined with existing systems and/or retrofit to existing operating casting systems, all within the scope of this invention.
In order to achieve the thermal management goals in some embodiments of the invention, a different or dissimilar lubricant or oil may be used in the corner portion to achieve certain of the objectives of this invention.
The utilization of thermal management zones as contemplated by this invention may provide for increased or decreased mold wall temperatures and/or heat transfer characteristics at and above the Initial Mold Chill Zone and the Slow Chill Zones, as compared to a typical mold framework. This may be through the alteration of the location of lubricant apertures and supply, altering the number of lubricant apertures in respective mold cavity wall zones, changing lubricant heat transfer values in specific areas around the mold cavity, changing the heat transfer characteristics of the mold cavity wall by the addition of heat or heat absorbing characteristics of particular zones (such as heat sinks), providing a mold cavity wall material which is dissimilar to that material around other portions of the mold cavity wall perimeter, and others.
In one of many possible examples, it may be desirable to provide increased ingot or castpart temperature in one or more of the corner zones. This may for example be accomplished by reducing or eliminating lubricant supply apertures in that corner to reduce the heat transfer away from the corner zone. This would result in a higher temperature than would otherwise be expected in that corner zone and reduce the temperature differential between the corner zone and a more central or intermediate portion of the castpart or ingot perimeter. In another embodiment of this invention, the corner zone of the mold cavity wall may be provided of a dissimilar material to alter the heat transfer characteristics and temperature at the corner portion. This would also result in a higher temperature than would otherwise be expected in the targeted corner zone, reduce the temperature differential between the corner zone and a more central or intermediate portion of the castpart or ingot, and provide improved thermal management around the mold.
In another embodiment, a supplemental source of heat may be provided to a targeted zone such as at one or more of the corner zones, or in the alternative or in combination, the proximity of the coolant may be reduced at or near the targeted corner or other zones, thereby reducing the heat transfer away from the inner mold cavity surface and achieving a more desired temperature profile.
FIG. 1 is described above in the Background of the Invention section, which will not be repeated here.
FIG. 2 is a perspective view of one of the numerous mold frameworks with which embodiments of this invention may be utilized. FIG. 2 illustrates mold 130, oil retention or lubrication cover 124, fasteners 125 in the lubrication cover, mold cavity 126, mold framework outer sidewall 127 and schematically showing lubrication apertures 129 with lubricant 128 dripping down the mold cavity wall. Item 132 shows the height of mold cavity wall 123 which may also be referred to as the mold framework. It is down the mold cavity wall 123 that the lubricant drips and at the bottom portion or lower portion 131 of mold cavity wall 123 is approximately near where the water coolant is sprayed on the molten metal (as shown and described in later figures below).
It will be appreciated by those of ordinary skill in the art that there are any one of a number of different mold framework configurations with which this invention may be utilized, with no one in particular being required to practice this invention. It will also be appreciated that the lubrication apertures 129 and lubrication 128 are for illustration and location, but not necessarily representative of actual lubrication flow patterns or spacing.
FIG. 3 is an elevation cross-sectional view of the exemplary mold framework configuration schematically depicting molten metal solidifying through the mold. FIG. 3 illustrates mold framework 141, water coolant aperture 135, molten metal 133 moving relative to mold framework 141 in the direction indicated by arrow 138. The molten metal 133 in the zone 137 is generally still more molten whereas the metal in zone 139 is or is becoming generally more solidified as the water coolant 136 chills the molten metal. The line 139 between the two zones is a very simplistic schematic representation of molten metal 139 versus more solidified metal after direct chilling in the chilled metal zone 134; whereas a more detailed depiction of one way that a solidification pattern may develop in a given mold is shown and described below relative to FIG. 13.
FIG. 4 is a perspective view of a partial section of an upper portion 140 of a mold framework where lubrication 145, 146 may be introduced into the mold cavity through a mold sidewall 141b. FIG. 4 shows a partial section of the mold framework at a corner section of a mold which would produce ingot shaped cast parts, illustrating partial mold framework 141, with fastener apertures 144 utilized to receive fasteners to attach the lubrication cover (shown in other figures), corner portion 141a of partial mold framework 141, lubrication apertures 143 and lubrication 145, 146 dripping down the mold cavity wall 141b portion of the partial mold framework 141. The partial mold framework portion 140 shown in FIG. 4 may typically be integral or one piece with the lower portion of the framework and mold sidewall in and around the chill zone (not shown in FIG. 4). For illustration purposes, the lubrication in the corner portion 141a is separately identified from the lubrication 146 in the more central wall portion as one aspect of the thermal management system described below is to thermally manage the corner portions of the mold from the more central portions.
FIG. 5 is perspective elevation view of a typical castpart 150 which shows a lower zone 152 with wavy or rippled corners 155 compared to an upper portion 153 without the same degree of wavy or rippled corner. The castpart 150 is to illustrate the difference between the lower zone 152 which has undesirable rippling 155 in the corners as compared to a smoother portion 153 shown without said rippling; however in a typical ingot castpart you would more typically see a consistent rippling pattern through the length of the castpart 150. This is especially true on aerospace type alloys such as aluminum series 2XXX and 7XXX.
FIG. 6 is detail 6 from FIG. 5 and further shows or illustrates the wavy or rippled corners 155 of castpart 150. As described above, the ripples or less smooth corners are less desirable and lead to more scrap due to formation of “J” cracks in aerospace type alloys.
FIG. 7 is a simplified top view of a mold framework 160, with lubrication cover 158, lubrication apertures or holes 162 generally evenly distributed around the perimeter of the mold cavity 161. Corner lubrication apertures 163 are also shown as part of the relatively even distribution of the lubrication apertures 162 and 163 around the perimeter of the mold cavity. Lubrication cover apertures 159 (bolt or fastener holes) are also shown in FIGS. 7 and are generally for securing lubrication cover 158 to attach it to the mold framework 160.
FIG. 8 is top view schematic representation of how one embodiment of a thermal management system contemplated by this invention may identify thermal management zones 180, 181, 182, 183, 184, 185, 186, 187, 188, and 189 around a mold framework 170, as part of thermally managing the mold process above the direct chill zone. The thermal management zones 180, 181, 182, 183, 184, 185, 186, 187, 188, and 189, are examples of zones which may be utilized in practicing some embodiments of this invention, around mold cavity 176. FIG. 8 schematic further shows corner portions 171a.
FIG. 9 is a top view schematic representation of another example of a thermal management system around a mold framework 200 and defining a mold cavity 201. FIG. 9 illustrates numerous thermal management zones 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229 and 230. Shown adjacent to the thermal management zones are potential exemplary thermal management areas that correspond to each zone for optimizing the quality of a castpart. The corresponding exemplary thermal management need areas in the various zones illustrated in FIG. 9 may be met through any one or more of the thermal management tools or means identified herein, such as altered lubrication flow, the distribution of lubrication apertures in said zones, and in other ways in practicing some embodiments of this invention. It will be appreciated by those of ordinary skill in the art that there are no particular number of thermal management zones which may be utilized in practicing embodiments of this invention.
FIG. 10 is a top view schematic representation of an example of a thermal management system within a mold framework 250 around a mold cavity 252. It will be appreciated that this figure, being in schematic form, is not showing representative dimensions, numbers of apertures, and the like, but instead is illustrating lubrication aperture distributions around a mold cavity 252. Other figures herein more accurately show how and where such lubrication apertures may be located relative to the inner mold cavity walls.
The thermal management system illustrates a plurality of exemplary thermal management zones 251a, 251b, 251c, 251d, and 251e with corresponding numbers and distributions of lubrication apertures 247, 248, 249 and 258, in various of the thermal management zones. It can be seen from FIG. 10 that some of the thermal management zones repeat depending on their location around the perimeter of the mold cavity 252. Again, it will be appreciated that this is merely one of a number of different potential configurations that may be utilized all within the scope in contemplation of different embodiments of this invention.
More particularly, FIG. 10 illustrates lubrication apertures of different locations and configurations, depending upon the zone that the lubrication apertures are located in. For example, thermal management zone 251c includes a pattern and configuration of lubrication apertures 249, thermal management zones 251d include a pattern and configuration of lubrication apertures 248, and thermal management zone 251b includes a pattern and configuration of lubrication apertures 247. It will be observed that the three corner thermal management zones 251e do not include lubrication apertures, whereas the corner of thermal management zone 251a does include a single lubrication aperture 258. Identifying thermal management zones allows such particularized applications and more precise thermal management in specific applications in this embodiment of the invention.
FIG. 11 is a top view schematic representation of another example of a thermal management system relative to mold framework 260 and mold wall 261, and includes thermal management zones 261a, 261b, 261c, 261d, and 261e. It will be appreciated that this figure, being in schematic form, is not showing representative dimensions, numbers of apertures, and the like, but instead is illustrating lubrication aperture distributions around a mold cavity 262. Other figures herein more accurately show how and where such lubrication apertures may be located relative to the inner mold cavity walls.
In the example shown of this embodiment of the invention in FIG. 11, lubrication apertures 265 correspond to thermal management zones 261e; lubrication apertures 263 correspond to thermal management zones 261c; lubrication apertures 264 correspond to thermal management zones 261d; lubrication apertures 266 correspond to thermal management zones 261b; and lubrication apertures 270 correspond to thermal management zone 261a. It will be appreciated by those of ordinary skill in the art that the number and location of lubrication apertures as well as the number and location of thermal management zones shown in FIG. 11, are merely exemplary for an embodiment of this invention and this invention is not limited thereto.
FIG. 12 illustrates one way that a solidification pattern may develop in a given castpart from the chilling or cooling of the molten metal in and around the water coolant outlet, it is more of a schematic representation of one example of how solidification may look. FIG. 12 illustrates mold framework 301, coolant aperture 329, coolant 302, Initial Mold Chill Zone 320 (sometimes referred to as the “IMCZ”), Slow Chill Zone 321, Advanced Cooling Distance Zone 322, semi-solid or mushy zone 323, where a mixture of solidified and molten elements/phases are present. Area or zone 324 is solidified metal that has been chilled. At the interface between the mold cavity wall 325a at the top of the IMCZ 320, it shows how the molten metal tends to shrink. The initial shrinkage is indicated in the area of solidification 324a and an air gap 304 is shown between the solidified metal 324a and the mold cavity wall 325a in that upper portion of the Slow Chill Zone near the Initial Mold Chill Zone 320. There is additional shrinkage in the Slow Chill Zone 321 as the solidification process continues. The atmosphere zone 327 is shown above the initial mold chill zone.
The upper portion of any mold framework will generally be at a particular steady state temperature during the casting process. In some embodiments of the invention and to increase castpart smoothness or quality, it may be desirable to eliminate any castpart or ingot temperature differential between the upper portion of mold framework wall 325 and a lower portion of mold framework wall 325c, which is right at the advanced cooling distance zone where water coolant is applied to the solidifying molten metal. Thermally managing by eliminating or greatly reducing the temperature differential will affect the shrinkage characteristics of the molten metal preventing corner cold folding or waves which lead to cracking.
FIG. 13 is an elevation view of a simplified example of both the upper portion and lower portion of the internal surface of a mold framework 330, and schematically illustrates a temperature delta or differential 309 from the Initial Mold Chill Zone 331 to the bottom of the Advanced Cooling Distance Zone 332. This illustrates the thermal management of a mold framework above the advanced cooling distance zone through the control (elimination or reduction) of the temperature differential. This thermal management and control will affect the shrinkage characteristics of the molten metal preventing corner cold folding or waves which can lead to cracking.
FIG. 14 is a perspective view of a partial section or corner of a thermal management system 350 imposed on mold framework 351, illustrating an example of one possible embodiment of a thermal management system contemplated by this invention. FIG. 14 illustrates lubrication apertures 352, 353 and 354, a corner portion 351a of mold framework 351 and elongated grooves 355 imposed in the corner portion to accomplish the desired thermal management. The grooves are shown in more detail in FIG. 15.
In focusing on the thermal control or management of the corners of the mold framework above the direct chill zone or above the Advanced Cooling Distance Zone, castpart characteristics and quality may be better controlled and improved. For example, grooves 355 would alter the surface interface between the solidifying molten metal and the inner wall of the mold cavity, thereby affecting shrinkage characteristics of the molten metal during the early stages of solidification (in or around the Initial Mold Chill Zone). Utilizing grooves 355 as shown in FIGS. 14 and 15, will also allow further thermal control of the heat transfer and temperature characteristics of the inner mold cavity wall in the corners relative to the zones or portions more central to the mold cavity perimeter. The grooves 355 may, in the practice of a given embodiment of this invention, be utilized in combination with other thermal management techniques, such as without limitation, those shown in FIGS. 16, 17, 18 and 19.
FIG. 15 is detail 15 from FIG. 14. FIG. 15 illustrates mold framework 351 and corner portion 351a of mold framework 351, lubrication apertures 354. FIG. 15 illustrates a series of grooves 357 that may be machined or imparted into the mold cavity wall surface to alter the thermal characteristics and heat transfer characteristics of the corner portion 351a. The grooves 357 may be used to affect heat transfer and/or the temperature patterns and differentials around zones around the perimeter of the inner wall of the mold cavity, and in other ways to achieve better thermal management above the Advanced Cooling Distance Zone. It will be appreciated by those of ordinary skill in the art that the grooves 357 shown in FIG. 15 are illustrative and any one of a number of different groove patterns and configurations may be utilized within the contemplation of this invention.
FIG. 16 is a top view of a partial section or corner of the mold framework 370 illustrating another embodiment of a thermal management system contemplated by this invention wherein a thermally dissimilar material is used for a section of the mold framework. Mold cavity sidewall 371 is shown with a dissimilar corner portion 372 with a dissimilar material, such as a ceramic, refractory or other material which may be utilized as part of the corner section and as part of the mold cavity wall to provide a thermal management system to maintain a desired temperature in the corner portion (which may be a temperature higher than would otherwise be experienced if the same material were utilized around the entire perimeter of the mold cavity). The use of a dissimilar material for improved thermal control may be utilized to more particularly determine the temperature of the mold cavity wall in the corner such as by controlling it to result in it being the same temperature as the more central portions of the perimeter of the mold cavity inner walls.
It will be appreciated by those of ordinary skill in the art that any one of a number of different types of dissimilar materials may be utilized in order to achieve a higher temperature in the corner portion of the mold framework 371, with no one in particular being required to practice this invention. One example of which may be to add an insulated refractory cloth to the mold bore in the corner portions or segments to thermally affect the heat transfer characteristics.
FIG. 17 is a top view of a partial section or corner of the mold framework 380 illustrating another embodiment of a thermal management system contemplated by this invention. In FIG. 17 a unique lubrication aperture distribution is utilized to thermally manage a corner of a mold framework 381. The corner portion 382 is shown with lubrication apertures 383 whereas lubrication apertures 384 are more utilized in an intermediate or adjacent portion to the corner portion 382. Similarly, lubrication apertures 385 are shown adjacent the other side of corner portion 382 to provide the desired thermal management effect and temperature distribution.
FIG. 17 further illustrates an example of another embodiment of this invention wherein a first lubricant source 378 is configured for and operably connected to the lubrication apertures 383 in the corner portion and a second lubricant source 379 is configured for and operably connected to the lubrication apertures 384. In this example the first lubricant source would have a first type of lubricant, and be configured to provide it to the lubricant apertures 383, and the second lubricant source 379 would have a second type of lubricant provided and it is configured to provide the second type of lubricant to lubricant apertures 384. The use of different lubricants in this embodiment would be selected to create different heat transfer characteristics as the lubricant is provided to the corner portion versus the other portion(s). In another example of an embodiment, the first lubricant source may provide a higher flow of lubricant to lubricant apertures 383 than the second lubricant source 379 would provide to lubricant apertures 384, thus creating different heat transfer characteristics in the corner portion. The lubricant sources may be any one of a number known in the art, including reservoirs coupled with lubricant pumps, or others, with no one in particular being required to practice this invention.
As described elsewhere herein, it may be preferred in some embodiments to eliminate lubrication apertures in the corner portions of the mold framework, all within the contemplation of different embodiments of this invention.
FIG. 18 is a top view of a partial section of the mold framework 400, illustrating another embodiment of a thermal management system contemplated by this invention. In the embodiment illustrated in FIG. 18, water coolant conduits 405 are distributed or reconfigured within the mold framework 401 in an application-desirable way to better thermally manage corner zone temperature or heat transfer patterns or characteristics. FIG. 18 illustrates corner portion 420 of mold framework 400, schematically representing lubrication apertures 403 corresponding to the corner portion of the mold framework.
FIG. 18 illustrates how, in a more typical mold framework 400, the water conduits 405 are configured and extended further into the corner portion 420 as indicated by hidden lines 404. In order to better thermally manage the corner portion 420 (such as to result in a higher inner mold cavity wall temperature than would otherwise be experienced), the water coolant conduits can be relocated or terminated further away from the corner portion 420, thereby resulting in a higher temperature in the corner portion 420 of the mold framework by altering the heat transfer characteristics in an identified corner zone.
FIG. 19 is a top view of a partial section of another embodiment of a thermal management system contemplated by embodiments of this invention. FIG. 19 illustrates a thermal management system imposed on the mold framework 420 which utilizes the addition of supplemental heat 425 schematically shown applied to the corner portion of the mold framework 420. The addition of heat would be designed to increase the temperature of the corner portion 422 of the inner cavity wall of the mold framework 420, thereby resulting in a more desirable castpart quality. Water coolant conduits 424 are also shown in their normal position and lubrication apertures 423 are depicted adjacent the corner portion 422.
As will be appreciated by those of reasonable skill in the art, there are numerous embodiments to this invention, and variations of elements and components which may be used, all within the scope of this invention. In one embodiment for example, a continuous casting mold thermal management system to thermally manage the pre-chill portion of a mold cavity inner wall, is disclosed comprising a continuous casting mold configured to produce a castpart, the mold comprising: a mold framework with a mold cavity disposed to receive molten metal, the mold cavity including a molten metal entry and a castpart exit; an inner wall within the mold framework, the inner wall generally defining the perimeter of the mold cavity, the inner wall including a direct chill portion and a pre-chill portion upstream from the direct chill portion; and wherein one or more identified perimeter corner sections in the pre-chill portion of the inner wall are configured to reduce heat transfer as compared to other portions of the inner wall around the inner wall perimeter.
In addition to the embodiment disclosed in the preceding paragraph, the invention may further include: the one or more identified perimeter sections providing dissimilar heat transfer characteristics correlated to perimeter sections on the castpart; the dissimilar heat transfer characteristics including providing less lubricant to the one or more identified perimeter sections; the dissimilar heat transfer characteristics include providing supplemental heat to the one or more identified perimeter sections; the one or more identified perimeter sections in the pre-chill portion of the inner wall are identified for dissimilar heat transfer characteristics to provide a more uniform temperature around the castpart perimeter; the one or more identified perimeter sections include a series of grooves in the corner portions of the perimeter of the inner wall; further wherein less lubricant is provided to the one or more identified perimeter sections which are corner portions of the inner wall; wherein the one or more identified perimeter sections in the pre-chill portion of the inner wall are configured to provide dissimilar heat transfer characteristics than other portions of the inner wall around the inner wall perimeter to provide a lower temperature differential between the pre-chill portion and the direct chill portion of the inner wall in the one or more identified perimeter sections.
A still further embodiment from that disclosed in the preceding paragraph may be further wherein the one or more identified perimeter sections in the pre-chill portion of the inner wall are configured to provide dissimilar heat transfer characteristics than other portions of the inner wall around the inner wall perimeter to provide a lower temperature differential between the pre-chill portion and the direct chill portion of the castpart in the one or more identified perimeter sections.
In a still further embodiment of that described in the second preceding paragraph, another embodiment may be further wherein a first lubricant supply is operably connected to the one or more identified perimeter corner sections and a second lubricant supply is operably connected to other portions of the inner wall; and further wherein the first lubricant supply provides one of a dissimilar lubricant or an increased lubricant flow to the one or more identified perimeter corner sections compared to that supplied by the second lubricant supply to the other portions of the inner wall.
In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.
Patent Application
20120186772
