US3509937A - Continuous horizontal casting - Google Patents

Description

May 5, 1970 F. J. RADD CONTINUOUS HORIZONTAL CASTING 3 Sheets-Sheet 1 Filed June 2, 1967 I II ."I

INVENTOR.

FREDERICK J. RADD BY I QCQM A 77' DRIVE Y May 5, 1970 F. J. RADD CONTINUOUS HORIZONTAL CASTING 3 Sheets-Sheet 2 Filed June 2, 1967 INVENTOR.

FREDERICK J. RADD Qm a WLZ/QMQQQUL A TTORNEY F. J. RADD CONTINUOUS HORIZONTAL CASTING May 5, 1970 3 Sheets$heet 5 Filed June 2, 1967 fica-E INVENTOR.

Feaaee/cz 1 PA 00 6 A770NEY United States Patent 7 3,509,937 CONTINUOUS HORIZONTAL CASTING Frederick J. Rudd, Ponca City, Okla, assignor to Confinental Oil Company, Ponca City, Okla., a corporation of Delaware Continuation-impart of application Ser. No. 434,867,

Feb. 24, 1965. This application June 2, 1967, Ser.

No. 643,079 The portion of the term of the patent subsequent to Sept. 26, 1984, has been disclaimed Int. Cl. B22d 11/06 U.S. Cl. 16487 4 Claims ABSTRACT OF THE DISCLOSURE A process for continually casting fusible material into a horizontal sacrificial web is modified by removing a substantial portion of the melt superheat in a batch cooling prior to the continuous casting.

This application is a continuation-in-part of application Ser. No. 434,867 filed Feb. 24, 1965, now U.S. Patent 3,343,590 issued Sept. 26, 1967, and assigned to the assignee of this application. This invention relates to continuous horizontal casting. In one aspect, the invention relates to method and apparatus adapted to continuously cast a horizontal rod of a high fusing material, such as steel. In another aspect, the invention relates to a method for continuously casting within a traveling sacrificial web in a substantially horizontal direction. In still another aspect, the invention relates to apparatus adapted to provide a horizontally traveling sacrificial web mold for continuous casting of high melting material.

There has recently been intense activity in the field of continuously casting high melting materials, such as steel. It has been the custom in the production of steel plates or strips, to cast the molten metal, as prepared in the open hearth, into ingots; and subsequently reheating the ingots for reducing in a blooming mill and repeated passes through the rolling mill to reduce the bloom to the desired dimensions for further operations. This requires heavy, expensive machinery which occupies considerable space, and consumes much time and labor.

Attempts have been made to obviate these objections by continuously casting directly from the melt to a semifinished form. These attempts have taken the form of casting in a horizontal or in a vertical direction, and, more recently, downwardly at an angle. The molds have taken the form of conveyors, primarily with such variations as oscillating conveyor segments, electromagnetic melt stirring, etc. All of the problems with which the various methods of continuous casting have been beset cannot be here described. Some of the more obvious difliculties, however, include designing a conveyor tight enough to hold the melt, yet flexible enough and with suflicient temperature resistance to be a continuous 100p, obtaining a cool ing rate which is high enough to provide economical throughput and yet cable of consistently producing the desired grain structure, and providing a continuous mold capable of varying product'dimensions to suit the market.

Accordingly, one object of the present invention is to provide a method and apparatus capable of continuously casting to a uniform product dimension. Another object is to provide method and apparatus for continuous horizontal casting in a liquid-tight and yet flexible mold. Still another object is to provide method and apparatus capable of varying product slab width and thickness during continuous casting without the necessity of major equipment change or process shutdown. Another object of the invention is to provide method and apparatus for adjusting and controlling the temperature of molten material sub- Patented May 5, 1970 jected to continuous horizontal casting in a traveling sacrificial web so as to obtain a relatively short freezing time in the continuous casting which is so produced. Other aspects, objects, and the several advantages of this invention will become apparent upon study of this disclosure, the appended claims and the drawings in which:

FIG. 1 represents a longitudinal vertical section of an apparatus according to my invention, partially in schematic form.

F FIGS. 2-4 depict vertical transverse sections taken on FIG. 5 represents a longitudinal vertical section similar to FIG. 1 of the drawings, but showing a modified embodiment of my invention which is particularly adapted for the continuous casting of steel and similar materials.

FIG. 6 is a sectional view taken along line 44 of FIG. 3.

FIGS. 7A and 7B are graphs illustrating certain aspects of the process of the invention.

According to the invention, there are provided, broadly, method and apparatus for continuous horizontal casting comprising a flexible sacrificial web and, in cooperation therewith, traveling conveyor means adapted to hold said web in a predetermined desired form. In a more specific aspect of the invention, the flexible sacrificial web and traveling conveyor means thus provided are utilized conjunctively and in combination with apparatus for adjusting and controlling the temperature of the molten material which is to be cast prior to the time at which such material is poured into the continuous traveling sacrificial we I have discovered that high melting materials, such as for example, steel, can be cast into a sacrificial web, such as a sheet of random weave ceramic fibers, the web being suitably supported during freezing of the high melting material and later being discarded. I have devised method and apparatus adapted to cast into such a traveling web, and one important aspect of my invention resides in method and apparatus which control variables in horizontal casting. Another important aspect of my invention resides in maintaining a sacrificial web moving in a constantly horizontal direction, the web being suitably exteriorly supported to provide a channel-like molding zone closed at one end, and in regulating the speed of travel of said web so as to allow the molten material in the molding zone to freeze at a substantially constant locus. Another important aspect of my invention is the provision of method and apparatus for pre-cooling steel and similar high melting materials prior to depositing the molten material in the traveling sacrificial web for casting so that the overall time required to produce the casting is substantially reduced and the uniformity of the product is improved.

The invention will now 'be illustrated by reference to the drawings. In FIG. 1 a roll of web material is adapted to unreel and provide a liner 2 for the traveling mold. The mold comprises a continuous loop conveyor 3, and can be a segmented link, a flexible metal band, or the like. The web 2 is flat as it comes olf roll 1, and is formed into a trough-like liner within conveyor 3, as shown in FIGS. 24. The source of molten material to be cast as shown here as a bottom-dumping ladle 4, although it is understood that the source can also comprise a holding chamber or the like and preferably takes the form illustrated in FIGS. 5 and 6 and hereinafter described in detail. The molten material is poured either continuously or intermittently, as desired, into a pool 5 formed by the web 2 along with the conveyor 3. The conveyor speed is adjusted to provide a residence time in pool 5, taking into consideration the input temperature and the freezing temperature of the material being cast, along with its heat loss rate, to effect freezing of the material near the downstream end of the conveyor in a zone indicated on the drawing as 6. The various adjustments to be described later herein are manipulated so as to maintain the zone of freezing transition 6 at a constant location, and the cross-sectional shape of pool is preferably constant upstream of this freezing zone in order to obtain quiescence of the material just prior to its freezing. The speed of conveyor 3 comprises, in the case of many materials, the primary control over the location of the freezing zone, and can be adjusted responsive to a determination of the location, for example, optically, visually or magnetically. After the material is frozen, as at 7, it is withdrawn and can be treated by any number of devices or methods of the art. For example, it can be exposed to direct or indirect heating or cooling, it can be pulled out with powered draw rolls at a fixed speed relationship with conveyor 3, preferably the same rate, and it can be sheared or otherwise cut into the desired billet lengths. At this point, the web 2 has served its function and will in many instances be quite charred; it can be removed from rod 7 by powered wire brushes or in any other manner as desired, and is discarded.

According to one embodiment of my invention, one control of the final billet thickness, as well as a protection of the billet upper surface, is effected by an additional roll 8 which unreels a web 9 of the same or similar material as Web 2. Web 9 is initially floated on the surface of the molten pool 5 at a height determined by roller 10. This roller 10 is moved upwardly or downwardly by a power unit 11, such as, for example, hydraulic cylinders, and it can be seen that the position of roller 10 will affect the final thickness dimension of billet 7. Power unit 11 can in turn be controlled by sensing means 12, which senses height or thickness of the billet in a suitable manner, as by feelers, light reflection, etc. It is understood that use of the assembly of items 8-12 is optional, but its use allows the billet top surface to obtain a more uniform appearance and to be protected from the atmosphere during cooling by web 9, which is removed later in a manner similar to Web 2.

The apparatus of FIG. 1 exhibits two other types of adjustment by means of conveyor 3, which will now be described. Major adjustments in the volume of pool 5 are useful when molten material source 4 is operated in an intermittent manner, since it will be seen that the final thickness of billet 7 would otherwise be diflicult to maintain at a predetermined constant level. These major adjustments are made by means of power sources 13-22, which can be similar to source 11. Sources 13-22 move the various respective roller sub-assemblies 23-27, which merely comprise structural members on which are mounted conveyor rollers 28. Each of the sub-assemblies, which can total as many as desired depending on the size of the apparatus, can be tilted around a horizontal axis perpendicular to the plane of FIG. 1 and can also be raised or lowered; the tilting can be effected by virtue of pivots 29, for example. It can thus be seen that both the general contour shape and the capacity of pool 5 are adjustable by suitable manipulation of power units 13-22. This rnanipulation can be responsive to a signal from sensing device 12 or a similar sensing device elsewhere on the solidified bar 7 or on the pool 5, for example, sensing means 30. Actuation can be directly in a control loop or can alternately be by an operator observing the output signal of a sensing device. In use, the sub-assemblies 23-27 are preferably operated so as to maintain a constant liquid level in pool 5 during periods of major change in that pool. For instance, when source 4 is pouring additional molten material into the pool, the sub-assemblies are lowered to compensate, and conversely, when no material is being added to the pool, the sub-assemblies are gradually raised at a rate which decreases the pool volume equal to the output rate of material as product 7. As mentioned earlier, the shape of the pool just upstream of the freezing zone 6 is important in that quiescense must be maintained here, and to this end certain of the rollers on downstream sub-assembly 27 are individually adjustable by virtue of power sources 31. These sources 31 allow fine adjustment of the product thickness in conjunction with roller 10, when used, and also allow changing the contour of the pool in the critical zone. Of course,

it will be realized that these adjustments can be eliminated if desired, but their presence is desirable in the best functioning of this invention. According to one em bodiment of my invention, the molten pool 5 can be partially or completely divided into two pools for a desired interval of time, as during addition of large amounts of charge liquid to the pool. This is effected by elevating one or more of the roller assemblies intermediate the length of the pool such that the bottom of the pool takes on the form of a rounded-off Greek W. The two pools can be completely isolated, so that large addition of material to the upstream pool is totally without effect on the downstream pool adjacent the freezing zone, or the two pools can be connected by a shallow amount of liquid. The upstream pool thus serves as a major supply pool, and the downstream pool as a product size control and quiescent zone. After the charge is added, the pools can again be converted into one pool, as shown in the drawing, by suitable manipulation of the roller assemblies.

One unobvious advantage of the practice of horizontal casting by my invention resides in the fact that impurity inclusions in the product can be substantially decreased by proper adjustment of the quiescent zone slope just upstream of the freezing zone 6. Although I do not wish to be so bound, I theorize that this occurs by rejection of the inclusions from the quiescent zone simply by gravity, and they accumulate near the bottom of the pool, where they can be cleaned out either by periodic shutdown of the apparatus and emptying of the pool to produce a tail product with a high inclusions content or by a forcing out of the dirty liquid and then replacing with a fresh liquid of lower impurity content, without process interruption because of the two-pool effect as described.

My invention also includes what might be termed a minor adjustment, which can be effected by pivoting all sub-assemblies 23-27 as one assembly 32 around a pivot point axis indicated in the drawing as 33. This point 33 is preferably located in an upstream portion of freezing zone 6, so that manipulation will have the least effect on the quiescent zone. This adjustment can be effected by a power source 34, similar to, e.g., source 11. Operation of source 34 effects a pivoting of the entire upper run of conveyor 3 around point 33, with the net result being a slight tilting upwardly or downwardly of the entire pool 5 around point 33. This has the effect of changing the head of molten material against the freezing zone, and will produce minor changes in the thickness of the product bar 7 without changing the shape of pool 5. Rotation around point 33 is preferably effected in response to measurement of the thickness of solid bar 7.

A final variable in the process is the speed of conveyor 3, which is adjusted so as to maintain the location of freezing zone 6 constant with respect to the apparatus. Draw rolls, not shown, are also preferably operated at the same speed as conveyor 3.

Reference is now made to FIGS. 2-4, which serve the dual function of illustrating the changing cross-sections through the length of pool 5 and also of illustrating various embodiments of conveyor type suitable for practice of my invention. The conveyor 3 illustrated in FIG. 2 comprises an endless flexible band, such as of stainless steel, which is maintained in the desired cross-sectional shape by rollers 28; these rollers are fixed laterally into the desired configuration at any given location along the length of pool 5, but are adjustable up or down as a unit, as described in conjunction with FIG. 1. The sacrificial web 2 is thus supported as desired. In FIG. 3, the conveyor is of the segmented or link type, as known in the art, each segment comprising a bottom plate with side plates hinged thereto. The side plates are held in the desired configuration for a given location along the pool by rollers 28, and the web 3 is thus held in the desired shape. The conveyor in FIG. 4 is very similar to that of FIG. 3, except in the present instance the side sections of a given conveyor segment are slideably held into the bottom section by, e.g., dovetail devices indicated schematically as 35. This latter design has the advantage of providing a rectangular cross-section at all times. The side portions of conveyor sections 3 are urged inwardly against the molten liquid head by fixed rollers 28, and again the web 3 is supported as desired. It is obvious that conveyor 3 can be either heated or cooled, directly or indirectly as desired, as known in the art.

It will also be obvious that the entire device of FIG. 1, or as much thereof as desired, can be enclosed in a suitable chamber for blanketing with inert gas. It is presently preferred that the inert gas blanket, when desired, includes the elements of FIG. 1 with the exception of supply rolls 1 and 8, and liquid source 4. Entry points of webs 2 and 9 into the chamber are easily sealed, and the rolls are readily renewed by splicing when located outside the chamber. Liquid from source 4 can readily be introduced into the inert gas chamber by a suitable door, especially When the liquid is added intermittently. Suitable inert gases for blanketing the casting operation include argon, nitrogen, helium, zenon and krypton.

The present invention is advantageous over both vertical and horizontal continuous casting devices of the prior art for many reasons. Among these are that the present system allows rejection of foreign inclusions from the solidifying slab and into the liquid pool, as previously explained. Also, the present invention produces a freezing zone which traverses the entire length and encompasses the entire width of the product slab Without interruption at a uniform rate during production, which provides uniformity in product properties, as opposed to many prior art horizontal casting processes where the casting is only semi-continuous in large open traveling mold segments. The present invention allows ready adjustment of the cross-sectional size of the final product both as to thickness and width and as to length. The outer surfaces of the product can be screened from atmospheric degradation by the web which lines the conveyor mold in conjunction with the covering web if desired.

A wide variety of materials are suitable for the web of my invention, and the choice of material will depend largely on the temperatures to which it is subjected during the process. It is obvious that simple webbing such as a thin kraft paper can be used When casting a relatively low melting material such as wax. On the other hand, casting of, e.g., steel requires a rather more durable web, as, for example, a ceramic fiber mat. An important feature of my invention resides in considering the web to be a sacrificial lining for the mold, with no attempt being made to reclaim it for direct re-use. Suitable web materials for casting steel include various fibrous inorganic cloths, with or Without integral wire reinforcing. One example is Carborundum Company L-144T cloth, which is an aluminum silicate cloth containing stainless steel Wire reinforcing and which contains no organic or combustible materials. The cloth is preferably of a random weave, and can be coated with a glass-forming powder composition to assist in making a liquid-tight web. It can comprise a single or multiple layers. In addition to the aluminum silicate, other inorganic fibers include calcium silicate and aluminum oxide. Although the web must maintain some strength at rather high temperatures in casting steel, it is obvious that the web can be of simpler material for casting lower melting products. For example, sulfur, wax or other materials freezing above ambient temperature can be cast in a kraft paper sheet by the method of my invention.

Several inherent characteristics of the continuous casting of steel in the basic sacrificial web system hereinbefore described make it desirable to preliminarily remove a substantial portion, or preferably all, of the superheat from the molten steel before depositing it in the pool 5. These characteristics result from the relatively high melting point of this material, the large amount of superheat which is imparted to the molten steel during manufacture, and the relatively high density of the molten steel. The high temperatures and high density involved require the provision of a more durable, relatively thicker web than in the case of many other materials, and the web in turn must be provided with adequate mechanical support to retain and shape the heavy body of liquid steel. This construction substantially reduces the heat transfer from the bottom and sides of the pool of molten steel, and thus reduces the overall cooling rate of the steel. Since the large amount of superheat must be dissipated before freezing of the steel can occur, it is highly desirable that the temperature of the molten metal be preadjusted to near the freezing point prior to pouring it into the pool 5. In this way, the continuous casting production rate can be substantially increased since the retention time in the mold can be shortened by a significant amount.

An embodiment of the invention which is particularly well adapted for the continuous casting of steel and similar materials of relatively high melting point and high density is illustrated in FIGURES 5 and 6. Since the traveling mold assembly employed as a portion of this embodiment of the invention is essentially identical to the assembly which has already been described, identical reference numerals will be used to identify identical structural elements where they appear. A horizontal trackway 36 is supported in any suitable manner above the travel ing mold and is characterized in having a central span which extends over the pool 5 of molten steel or similar material. The trackway 36 is preferably constructed at a minimum vertical height above the pool 5- to reduce splashing problems as will be hereinafter further explained.

A carriage designated generally by reference numeral 37 is movably mounted on the trackway 36, and is supported by track engaging wheels 38. The carriage 37 is provided with a pair of trunnion blocks 39 at each end thereof, and a central trunnion block 40 in the center thereof. Two rocker cooler drums 41 and 42 are mounted on the carriage 37 in longitudinally spaced, end-to-end relation. Each of the cylindrically shaped rocker cooler drums 41 and 42 carries a stub shaft 43 at each end thereof, these shafts being positioned on the projected longitudinal axes of the respective drums. The stub shafts 43 of each rocker cooler drum are journaled in the respec tive trunnion blocks 39 and 40 adjacent the opposite ends of each drum, so that each drum can be rotated about its longitudinal axis. Rotation of the rocker cooler drums 41 and 42 in either direction is achieved in the case of each drum by a semi-circular gear segment 44 secured to the periphery of the drum and engaged by a suitable gear 45 driven by a reversible motor 46. Each of the motors 46 associated with the two rocker cooler drums 41 and 42 is mounted on the carriage 37, and the motors are independently and automatically controllable from a remote location by any suitable, conventionally constructed control circuitry.

Before referring to the details of construction of the rocker cooler drurns 41 and 42, and the manner in which they are used, it will be noted that the depicted system further indicates a pair of horizontally spaced, tilting type ladles 47 and 48, which are aligned with the trackway 36 to permit molten steel to be poured from each ladle into one of the rocker cooler drums 41 and 42 as hereinafter explained. Instead of the tilting type ladles, bottomdumping ladles of the type shown in FIG. 1 can be employed if desired.

V *7 The principle of operation of the rocker cooler drums 41 and 42 is known in the art and is employed, for example, in a device known as the Detroit rocking arc furnace. In apparatus of this general type, a rockable container is provided and contains in the walls thereof, suitable heating and cooling elements, such as carbon or graphite electrodes and coolant carrying pipes. Temperature adjustment and control of a molten material contained within the container is achieved by control of the described heating elements conjunctively with a controlled rocking motion of the container. The rocker cooler drums 41 and 42 used in the embodiment of the present invention depicted in FIG. are double walled, refractory lined drums. Each drum is of two part construction, having a frusto-cylindrically shaped lid portion 50 which is connected by a suitable hinge 51 along a longitudinal parting line to a frusto-cylindrical base portion 52. Intertfitting lap joints are provided at the parting lines between the lid portion 50 and the base portion 52 to provide a seal against the escape of molten steel from the rocker cooler drum when the lid portion is closed. Any suitable type of latching mechanism (not shown) can be provided for the purpose of locking the lid portion 50' in its closed position at certain times during the use of each rocker cooler drum as hereinafter explained. There is also provided mechanism (not shown) for automatically pivoting the lid portion 50 of each rocker cooler drum about its respective hinge 51 to an open position at such time as the drum moves to a position beneath one of the ladles 47 or 48. The same mechanism, which can be a cam and crank arrangement, or the like, can be made to automatically close the lid portion 50 of each drum as the carriage moves the'respective drum away from one of the ladles 47 and 48 and toward a central position over the pool 5.

As depicted in FIG. 6, the lid portion 50 of the drum contains suitable heating elements 53, which in the illustrated embodiment, are retractable, radially extending carbon or graphite rods for electric arc heating of the drum contents. The base portion 52 can also be provided with heating elements disposed in the refractory material between the walls if further temperature control is desirable... It will be noted that, in the illustrated embodiment, the lid portion 50 extends through only about 120' to 150 of the entire circumference of the drum. This reduces its weight and permits it to be more easily opened, and also allows a larger amount of molten steel to be deposited in the base portion 52 of each rocker cooler drum.

The lid portion 50 of each of the rocker cooler drums 41 and 42 is provided with a pouring lip 54 constructed of a high melting point metal, and includes an internal baflie 55 extending across the opening in the lid portion to the pouring lip. A seepage collector tray 56 is provided on the base portion 52 and extends therealong just beneath the lap joint formed between the lid portion 50 and the base portion 52 when the lid portion is closed.

The function of the system depicted in FIG. 5 as including the trackway 36, the carriage 37, the rocker cooler drums 41 and 42 and the ladles 47 and 48 is broadly to permit the molten steel to be brought to an optimum temperature for continuous casting prior to depositing it in the pool 5. More specifically, the rocker coolers 41 and 42 are used to remove from the molten steel received from the ladles 47 and 48 as much of the superheat as possible prior to pouring the molten steel into the continuous mold. To better understand this objective and the way in which it is accomplished with the depicted apparatus, reference is made to FIGS. 7A and 7B, which graphically illustrate respectively (a) the general manner in which thetemperature, T, of a body of molten steel decreases with passing time, t, as heat is removed from the body at a substantially constant rate, and (b) the general manner in which the viscosity, 7], of the molten steel increases with passing time, t, as heat is removed from the body of molten steel at a constant rate.

Assuming that at zero time, t or the outset of the process, steel is retained in the ladles 47 and 48 at a temperature, T which will, under present conventional practices, be several hundred degrees F above the freezing point of this material, removal of heat at some constant rate over a period of time results in the molten steel being brought to its freezing point T at a time t At this stage of the process, the latent heat of fusion must be removed from the body of the molten steel in order to convert it to the solid state and this occurs over a time interval t t in which no change occurs in the temperature of the steel. After complete solidification by freezing, the temperature of the solid steel will, of course, continue to drop with passing time as additional heat is dissipated.

In the use of the apparatus depicted in FIG. 5, molten steel at temperature T, is ladled into one of the rocker cooler drums 41 or 42 from either the ladle 47 or 48, respectively. When the drum is filled to about the level shown in FIG. 6, the lid portion 50 is closed and latched and the carriage 37 is shifted on the trackway 36 by any suitable remotely controlled drive system to bring the newly filled rocker cooler drum to the central position over the continuous mold, and specifically the pool 5 of molten metal. Concurrently, the other rocker cooler drum 41 or 42 will be moved beneath its respective ladle for refilling. From each rocker cooler drum 41 or 42, molten steel is delivered to the pool 5 by rocking the drum about its axis until the molten steel can pour out through the pouring lip 54.

The time required to fill each rocker cooler drum 41 and 42 and to shift the drum to its dumping position over the pool 5 is correlated with the rate of heat loss from the molten steel in the drum so that at the instant that the steel is poured from the drum into the pool 5, its temperature is very close to the melting point, or is in fact at the melting point. In other words, substantially all of the superheat will have been removed by this time, and the flat or zero slope portion of the curve depicted in FIG. 7A will be approached or entered.

The rocker cooler drums 41 and 42 are especially well adapted to achieve the necessary cooling effect. Thus, the interval of time over which the lid portion 50 is left open is one available control over the rate of heat loss from the molten steel in the drum. A finer control is provided by the rocking characteristics of the drums. Thus, by the provision of suitable temperature sensing devices in the drums and connected to automatic controls which respond to sensed temperatures for controlling the energization of the motors 46, the drums may be rocked about their axes to bring the molten steel into contact with the cool upper portions of the drums. The baffle plate 55 provided in each drum prevents molten steel from sloshing out of the pouring lip 54 during the rocking motion used to effect cooling. Finally, if the rate of removal of heat should for some reason be higher than optimum, so as to bring the steel too close to its point of solidification, the same automatic sensing and control apparatus can be utilized to energize the rods 53 to strike an arc to the metal and restore a small amount of heat to the molten steel thus assuring retention of a desired state of fluidity until it is released into the pool 5.

By this control of the temperature of the molten steel, it can be delivered to the pool 5 of the continuous mold with enough residual heat to prevent its solidification until it reaches point 7 in the continuous mold. More importantly, however, the superheat has substantially all been removed from the steel so that no undesirably large holding time in the pool 5 is required, and the production rate is greatly increased.

As contrasted with control of heat removal on the basis of sensed temperature alone, a preferred procedure additionally utilizes the viscosity of the molten metal as a final and more sensitive control of the rocking motion of the rocker cooler drums 41 and 42, and of the times when these devices are rocked by a sufficient amount to permit the molten steel to flow through the pouring lip 54 and into the molten pool 5. In referring to FIG. 78 it will be noted that the slope of the viscosity 1; vs. time 1 curve isat a minimum value over an extended period of time between two inflection points, A and B. This portion of the curve corresponds to the period of time during which the molten steel is at its freezing point, but is losing its latent heat of fusion after all of the superheat has been removed. Crystals of solid steel are forming in the molten body and gradually increasing its viscosity. By continuously monitoring the temperature and determining therefrom the viscosity, the rocker cooler drums 41 and 42 can be dumped at a time when the steel is losing its latent heat of fusion, which time is just far enough in advance of the time of complete solidification to permit the continuous mold to be operated at maximum speed to achieve the optimum production rate commensurate with mechanical limitations of the system.

It should be pointed out that though the illustrated embodiment of the invention proposes the use of two ladles and two rocker cooler drums, additional ladles and drums, as well as parallel trackways could as well be provided, and would perhaps afford better continuity in the operation. Further, the specific construction of the rocker cooler drums which is adapted for a given installation is subject to considerable variation is design detail, heating controls and the like, and the cooler diums here depicted are intended to be considered only as exemplary.

Further understanding of the invention will be gained from consideration of the following specific examples.

Example 1 A melt was made up in proportion of about 6 kg. ingot iron, 100 g. standard ferromanganese and 40 g. ferrosilicon. This melt was cast into channel-shaped molds made from Carborundum Company L144T cloth, suitably supported on the outside to maintain the channel shape. The steel was poured at about 300 F. The product ingots had the shape of the mold, and were clean and uniform on the bottom and side surfaces where they contacted the cloth web. Their upper surfaces showed some oxidation, since they were not protected by either a top web or an inert atmosphere. The cloth web held its shape throughout the pour for a sufficient time to allow complete cooling of the ingots.

Example 2 An SAE 1020 carbon steel formulation containing 0.2

percent carbon, 0.3 percent manganese, and about 0.045

phosphorus and sulfur is retained in two horizontally spaced ladles at a temperature of 3010 F. A pair of alternately shifted rocker cooler drums similar to those shown in FIG. 5 are provided for alternately receiving the liquid steel from these ladies and then moving to a point over the pool of molten steel retained in a continuous mold of the sacrificial web type. The steel initially enters each rocker cooler drum at a temperature of about 2960 F. As each rocker cooler is moved to its dumping point, it is automatically rocked in a controlled fashion to bring the temperature in the rocker cooler drum to a temperature of 2830 F., 50 F. above its freezing point. Upon reaching this temperature, the rocker cooler drum is rotated about its longitudinal axis by a sufiicient amount to permit the molten steel to be discharged through the pouring spout into the molten pool of steel in the continuous web. The cooling effect of the surrounding air on the cascading steel results in it being cooled about 30 P. so that it enters the pool at a temperature of 2800 F., 20 F. above its freezing point. The continuous mold is operated to produce solid carbon steel rods or slabs at a relatively high rate.

Having thus described the invention by providing specific examples thereof, it is to be understood that no undue limitations or restrictions are to be drawn by reason thereof and that many variations and modifications are within the scope of the invention.

I claim:

1. In the method of continuously casting a fusible material which comprises:

(a) providing a source of said material in molten form,

(b) continuously passing a sacrificial web of heat-resistant material in a substantially horizontal direction, said web being externally supported so as to define a molding zone open at the topand one end thereof,

(0) passing molten material from said source to said molding zone, and

(d) regulating the speed of travel of said web so as to maintain at a constant predetermined locus a transition of said molten material from the molten to the solid state, the improvement in said providing of step (a) which comprises batch-wise cooling of said material in molten form so as to remove substantially all of the superheat therefrom prior to said passing of step (c).

2. The method of claim 1 wherein all of said superheat and a portion of the latent heat of fusion of said material in molten form is removed therefrom prior to said passing of step (c), and further characterized to include the step of measuring the temperature and deter mining therefrom the viscosity of said molten material to determine the optimum time for said passing.

3. The method of claim 1 wherein said cooling is effected by partially filling a container With said molten material and rocking said container to bring said molten material into contact with exposed surfaces of said container which are cooler than said material.

4. The method of claim 3 wherein the rocking of said container is correlated with the viscosity of the molten material in the container as determined by temperature measurement whereby an optimum predetermined viscosity characterizes the material at the time it is passed into said molding zone.

References Cited UNITED STATES PATENTS 2,242,350 5/1941 Eldred 164125 X 2,285,740 6/1941 Merle 16428l 3,343,590 9/1967 Radd 16487 OTHER REFERENCES Iron Age (Reprint), Aug. 26', 1948,,TS 200. I 8.

J. SPENCER OVERHOLSER, Primary Examiner R. S. ANNEAR, Assistant Examiner US. Cl. X.R.

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