US3874438A

US3874438A - Apparatus for the continuous casting or drawing of an extrusion body through a coolant body

Info

Publication number: US3874438A
Application number: US278383A
Authority: US
Inventors: Keith Phillips; Peter Sahm
Original assignee: BBC Brown Boveri France SA
Current assignee: BBC Brown Boveri AG Switzerland; BBC Brown Boveri France SA
Priority date: 1971-08-30
Filing date: 1972-08-07
Publication date: 1975-04-01
Anticipated expiration: 1992-04-01
Also published as: CH537766A; GB1411977A; DE2146740A1; GB1411976A; FR2150895B1; BE788070A; NL7211678A; FR2150895A1

Abstract

In continuous casting, or drawing, an extrusion body (i.e., a strand or a tube) from a molten mass (e.g., a metal melt) the solidification front is made to occur whilst the body is passing through a shaping station, whereupon the body is introduced into a cooling bath.

Description

United States Patent Phillips et al.

I APPARATUS FOR THE CONTINUOUS CASTING OR DRAWING OF AN EXTRUSION BODY THROUGH A COOLANT BODY Inventors: Keith Phillips, Niederrohrdorf; Peter Sahm, Nussbaumen, both of Switzerland Brown Boveri 8L Company Limited, Baden, Switzerland Filed: Aug. 7, 1972 Appl. No.2 278,383

[73] Assignee:

Foreign Application Priority Data Aug. 30, 1971 Switzerland 12600/71 US. Cl 164/283 S, 164/89 Int. Cl B22d 11/12 Field of Search 164/82, 85, 89, 283 S References Cited UNITED STATES PATENTS 5/1941 Eldred 164/89 [451 Apr. 1, 1975 OTHER PUBLICATIONS Metal Industry, August 1, 1947, TS200.M586, pp. 83-85.

Primary Examiner-R. Spencer Annear Attorney, Agent, or Firm-Pierce, Scheffler & Parker [57] ABSTRACT In continuous casting, or drawing, an extrusion body (Le, a strand or a tube) from a molten mass (eg, a metal melt) the solidification front is made to occur whilst the body is passing through a shaping station, whereupon the body is introduced into a cooling bath.

2 Claims, 5 Drawing Figures PATENTED 1 I975 SHEEI 2 BF 5 Fig.2

APPARATUS FOR THE CONTINUOUS CASTING OR DRAWING OF AN EXTRUSION BODY THROUGH A COOLANT BODY This invention is concerned with the art of continuous casting, and is concerned with a process for the continuous casting or drawing of an extrusion body, especially a metallic body, from a molten mass. Another aspect of the invention is the provision of an apparatus for the practical application of such process where there is provided next to the outlet of a crucible containing the molten mass, a cooling device with the extrusion body passing through it.

Fields of application for metallic materials produced by an extrusion process have a wide range requirements, especially concerning the compliance with predetermined patterns and specific structural characteristics. Therefore, if high-quality work pieces are to be produced, for example work pieces which can sustain heavy mechanical, thermal, or possibly chemical stresses, or which need to possess specific magnetic characteristics, the setting of the solidification specifications, in other words all physical parameters within the zone between molten mass and solid extrusion body, as well as the special distribution of such parameters, will need careful attention. Important, among other features, will be the abruptness of the temperture drop within the zone of the solidification front. Especially for the purpose of the directional solidification, an often required feature, and primarily for the formation of threador fiber-like textures, there will often be a need, in addition to the compliance with specific requirements concerning the shape of the solidification front. for extremely high values of the temperature gradient within the zone of the solidification front. This is already known (US. Pat. No. 3,434,892) in connection with iron-cobalt alloys, with aluminum, antimony, beryllium or the like used as an additional alloy component, which under appropriate conditions including a temperture gradient within the zone of the solidifi' cation front of up to C/cm, will solidify while forming fibrous crystallites with a particularly high magnetic coercitivity.

Heretofore, the temperature gradients within the zone of the solidification front could be influenced only by standard means and processes, employed in connection with general extrusion operations, namely the devices for cooling the extruded body upon leaving the melting pot. These means are without exception dietype elements, their hollow section corresponding to the profile of the extruded body. The heat transfer required for the lowering of the temperature within the zone of solidification takes place first in the longitudinal direction of the extruded strand by way of the strand body proper, and secondly radially and outwardly by way of the areas of contact between strand and die. In the case of heat transfer of this type, the setting of a steep temperature drop will usually be difficult, first because of the relatively high resistance to the heat transfer by the two contact surfaces, thus preventing a rapid lowering of the temperature, and secondly due to the comparatively high thermal conductivity in longitudinal direction of the strand within the die elements comprising the solidification front, resulting in a corresponding temperature equalization in longitudinal direction of the strand, and thus in a flattening of the temperature drop.

It is an object of the present invention to provide a process which makes feasible the setting of high temperature gradients within the zone of solidification of a body which is continuously extruded from a molten mass. The process, proposed by the invention as the solution of this problem, is characterized, in combination with the above-mentioned features of the process, by the introduction of the extruded body into a cooling bath, after passing through a shaping station which comprises the solidification front. The apparatus, proposed by the invention to carry out such process, is characterized in connection with the above-mentioned apparatus characteristics by the features that the cooling device comprises a cooling bath, accommodated within a container, with the extruded body dipping into the bath level, said level of the cooling bath being arranged beyond the solidiflcation front of the body emerging from the molten mass. Due to the introduction of the extruded body into a cooling bath beyond the solidification front, as provided by the invention, there is attained not only a greater outflow of heat because of the substantially lower resistance to the heat transfer between body surface and cooling bath, thus causing a stronger longitudinal flow of heat within the extruded body, but also a reduction in the temperaturebalancing heat flow within the media, placed parallel to the solidification front and surrounding the extruded body because these media no longer represent cooling elements but merely shaping elements, the temperature of which, just suffficient for solidification, need to be only slightly below the solidification temperature of the cast material.

Additional features and advantages of the invention will become apparent from the following description of specific examples, taken with the appended drawing, in which:

FIG. 1 depicts a first species of an extrusion apparatus with height-adjustable cooling bath container in the form of a vertical section through the axis of the extruding body;

FIG. 2 shows a second species of an extrusion apparatus with height-adjustable cooling bath level in the same form as FIG. 1;

FIG. 3 shows a third species of an extrusion apparatus for the manufacture of tubing, using cooling fluid, again in a form of vertical section as in FIG. 1',

FIG. 4 depicts a fourth species of an extrusion apparatus for the manufacture of tubing, its cooling device being a modification of the device shown in FIG. 3, and a pass-through track, again as a vertical section through the tubing axis which in this case is curved; and

FIG. 5 shows still another species of an extrusion apparatus with plunge-cooling bath, similar to FIG. 2 but with internal cooling flow for the cooling bath.

The apparatus shown in FIG. I is provided with a crucible 1, accommodating a molten metal mass 2, from which a strand or wire-shaped body 3 continuously extrudes, downward by way of a shaping crucible outlet la. For heating the mass there is provided an inductive heater 4, for example, a high frequency heater with a generator (not illustrated). The temperature distribution within the zone of the crucible outlet is set in correlation with the solidification temperature of the cast material in such manner that the solidification front 3a will be located within the shaping duct of the crucible outlet, and will remain substantially at the same spot within the crucible outlet during the continuously running extrusion process. Heat transfer, which is necessary for the solidification, takes place (in the case of the example shown) primarily in longitudinal direction of the strand. namely by way of the emerging extrusion body 3 proper, which shortly beyond the crucible outlet la enters a cooling device denoted by numeral 5. This cooling device comprising a cooling bath 7, disposed in a cylindrical container 6, with the body 3 entering the bath at level 7a, viz., the level arranged at a short distance from, and below, the crucible outlet. A molten mass of a metal having a low melting point, such as tin, will be an appropriate material for the cooling bath 7. The solidification heat of the cast material, absorbed by this cooling bath, is then transferred by way of the walls of the container 6 to an outer cooling jacket 8 which consists of a liquid flowing to and from connections 9 and I0, and placed within a jacket surrounding the container 6.

Entry of the extrusion body 3 into the cooling bath just beyond the solidification front results in a steep temperature drop extending into the region of the solidification front. The steepness of the temperature drop is still further enhanced by the absence, within the region next to the solidification front, of elements which are good conductors of heat. The front itself is located within the region of the comparatively poorly heat-conducting crucible wall, while the strand itself in the small space between crucible outlet and cooling bath level is surrounded by air, also a poor heat conductor, or possibly by an inert gas.

In the interest of temperature constancy within the cooling bath, it is advantageous to select an eutectic molten metal mass, for example an eutectic galliumindium mass. The thermal arrestation point during the cooling process of such mass offers the advantage of some temperature barrier in case of a fluctuating accrual of heat which might occur especially during the initial stage of the extrusion process until operations become stabilized.

The container 6 of the cooling bath is mounted for vertical movement within the housing of the cooling device by means of scaled guide points 11 and 12 above and below the cooling jacket 8, so that the distance between the cooling bath level 7a and the crucible outlet la, or the solidification front 30 respectively, and thus the temperature gradient within the zone of the solidifi' cation front, can be varied and adjusted. For this purpose, the lower cover 14 of the cooling bath container 6 is coupled to the piston rod 15 of a double-acting hydraulic cylinder 17. The piston 16 of this cylinder can be loaded by a pressure source (not illustrated) by way of

control fittings

18 and 19 to effect a lowering or rais ing of the cooling bath container. Piston rod 15 is provided with a central perforation 20 for passage of the extrusion body 3. At the exit point of the cooling bath container 6 there is arranged a duct 13 which surrounds the extrusion body liquid-tight. A suitably designed species of this duct, provided with a scraping edge 13a, insures that there will be no loss of cooling bath liquid during the continuous pass-through operation.

The species shown by FIG. 2 is identical with the species illustrated by FIG. I, so far as crucible l with molten mass 2, body 3 emerging by way of crucible outlet la, and solidification front 3a, located within the crucible outlet, are concerned. These components are denoted by like numerals for this reason. Different, however, is a cooling device 25 which is provided with a cooling bath 27 that is placed in a stationarily mounted container 26. The height adjustment of the cooling bath level 27a is accomplished with the aid of a device 21 for adding or removing increments of the cooling medium, its essential component being a header tank 23 which is in communication with the cooling bath container 26 by way of a flexible hose pipe 22 and which is mounted vertically movable within a fixedly mounted cylinder 24. The height adjustment of the header tank, and thus the height adjustment of the cooling bath level 27a, can be accomplished by means of a hydraulic cylinder 28, its piston rod being coupled to the header tank in a manner such as is illustrated in FIG. 2. The height adjustment of the cooling bath level by the addition, or removal, of cooling bath liquid, and especially the specific design illustrated with its vertically adjustable header tank, is distinguished by its simplicity in construction and wide range of adjustment, but is preferred only in connection with coolants which will remain in the liquid state without benefit of heat supplied by the solidifying extruding body.

All of the above-discussed species have the advantage that an indicator and, if desired, an automatic control of the level of the cooling bath, can be established in a simple manner. Basically, it only is necessary to connect an indicator to the height-determining component, for example to the piston rod 15 of FIG. 1 or to the header tank 23 of FIG. 2, and to arrange a suitable reference/actual value comparator, its output controlling in obvious manner the regulating part, for example the hydraulic cylinder I7, or 28, respectively, in order to maintain a predetermined level of the cooling bath. With the aid of a reference data emitter, known per se, which furnishes an adjusted reference value after a predetermined period of time, it becomes also feasible with the aid of the devices illustrated to change the distance between the exit point of the body from the molten mass and the entry point into the cooling bath in a precise manner, for example after a predetermined periodic time sequence. In this manner it becomes possible to attain corresponding changes in structure throughout the length of the extruded body being produced if these changes are functionally related to the steepness of the temperature drop within the zone of the solidification front.

The mechanisms shown in FIGS. 3 and 4 are suitable for the manufacture of

tubular extrusion bodies

33, or 43, respectively. For this purpose there is inserted into the outlet of the crucible, accommodating the molten mass, a shaping

die

31, or 41, respectively, in accordance with the desired inner profile of the tube, with suitable supporting parts 310, or 41a, respectively.

In the case of the species illustrated in FIG. 3, the construction of the device for cooling the body emerging from the molten mass is indentical with the design sign in FIG. 2, so that there will be no need for specific explanations or reference numerals. This applies also to the adjustment in height of the cooling bath level by the device for the addition and removal of the coolant, omitted in FIG. 3, to be assumed as being connected with the cooling bath container by way of the fitting 32. The extruded body 33, emerging downwardly from the cooling bath container, is seized by

drive rollers

34, 34 and is moved at a preset advance speed into a pressuregas chamber 35 which is closed off during operations and is provided with a lower part 350 which extends in the shape of a tube. The length of this lower part corresponds to the foreseen strand length for one continuous phase of operations. This lower part can be swiveled about a lower axis of rotation 35b in direction of the arrow A, away from the upper part of the pressuregas chamber, and then swiveled back again. A drive cylinder 36 is provided to carry out this swiveling motion. When swiveled back, i.e., in the position illustrated in FIG. 3, the areas of contact between the upper part and the lower part of the pressure-gas chamber are connected with each other in gas-tight manner by means of a deformable gasket 35c.

At the lower end of the emerging body 33 there is inserted a one-way valve 33b which allows the pressure gas from the chamber 35 to enter the tube while preventing a filling 33a of coolant, placed inside the tube, from leaving. The gas pressure, acting from below, supports the fluid level against gravity and raises it to such degree that an intensive cooling effect is exerted from the tube interior upon the solidification zone of the ex' truded body. The heat dissipation is therefore not limited to the relatively thin tubular walls of the body but extends over the entire inner profile of the tube and the coolant, present therein, down to the lower tube areas where the heat compensation is accomplished due to the large-area tube contact with the cooling bath.

Thus, a steep temperature drop within the zone of solidification becomes possible even in the case of thin tubular walls. Furthermore, the liquid filler can come into contact with the shaping die 31 and influence the zone of solidification in this way also. This arrangement will at the same time have a cooling effect on the shaping die itself, which circumstance is another desirable feature.

The one-way valve 33b, placed at the lower end of the extrusion body, facilitates the starting of the drawing process. For this purpose a tube which acts as initial body and which is provided with the one-way valve, the profile of said valve corresponding to the profile of the body to be produced, is inserted, after being filled with the proper amount of coolant, from below through the still empty cooling bath container into the outlet of the still empty crucible, while the lower part 35aof the pressure gas chamber is swiveled outwardly. Part 35a is then swiveled back into position and the gas pressure is adjusted in such manner that it will hold the cooling liquid in place. The cooling bath and the crucible are filled, and the drawing operation is begun, the drawing being influenced by the drive roller 34, with the solidification front of the downflowing cast material forming at the upper end of the tubular initiating body. Gas pressure within chamber 35 is kept constant by means of a governor 38a in combination with a servomotor 38b and a two-way-acting valve 386, the latter connecting chamber 35 by means of a flexible hose 37 either with a pressure gas supply line 39a or a pressure gas drain plug 39b, depending on the fluctuation from the pressure valve required.

According to the species shown in FIG. 4, the tubular body 43 is also conducted directly into a cooling bath 43 by way of a guide member 42, but is subsequently guided from the cooling bath by way of an upwardly curved conduit. This guidance is accomplished by a roller 44 having a comparatively large diameter, with the extruded body curving around the roller. A set of straightening rolls 45, 45 follows this arrangement to straighten the emerging body. This species in a particularly simple manner permits an operation by the use of a cooling fluid 43a which can be held in place without additional means inside the tube and which can be advanced close to the solidification zone, or to the shaping die 41, respectively. On the other hand, the apparatus and the technique shown in FIG. 4 is suitable only in connection with relatively flexible extrusion bodies, that is, especially for tubes and the like with comparatively small diameters.

The species shown in FIG. 5 provides a plungecooling bath 57, again in combination with a crucible 1, into which bath a solid body 3 is drawn from its outlet la. However, the solidification heat of the body is removed from this cooling bath not by an external but by an internal cooling flow, in the form of a coiled pipe 58, with a suitable coolant flowing through it. Also provided, in the area between the cooling bath level 57a and the outlet 1a of the crucible, is a low pressure or vacuum chamber 51, which causes a heat insulation at the circumference of the extrusion body 3 leaving the crucible outlet, and thus a substantially axially directed heat flow with a correspondingly level solidification front 3a within the region of the crucible outlet. The low pressure chamber 51 is connected by way of conduits 52 with a low pressure chamber 53 which we rounds the entire crucible l and which is provided with an exhaust line 54. A removable, air-tight, cover 55 to chamber 53 permits access to crucible 1 for charging it with molten mass. Heating the mass is accomplished through the walls of the low pressure chamber 53, of poor electric conductivity, and the crucible l by means of an electric induction heater 56.

We claim:

1. Apparatus for the continuous casting or drawing of a tubular extrusion body from a molten mass, which comprises a crucible for holding such molten mass, said crucible having a bottom outlet,

a cooling device provided next to the outlet of the crucible through which such extrusion body runs, said cooling device comprising a cooling bath positioned in a container, with such extrusion body immersing into the level of the bath, and

means for adjusting the distance between the crucible outlet and the cooling bath level which means are arranged beyond the solidification front of such extrusion body emerging from the molten mass,

there being provided within such tubular extrusion body a column of cooling liquid and a filling of pressure gas which loads this column counter to the running direction of such extrusion body.

2. Apparatus for the continuous casting or drawing of an extrusion body from a molten mass, which comprises a crucible for holding such molten mass,

a cooling device next to the outlet of the crucible through which the extrusion body runs, said cooling device comprising a cooling bath, consisting of a molten mass of an eutectic gallium-indium alloy, placed in a container, with the extrusion body immersing into the level of the bath,

means for adjusting and maintaining the cooling bath level which means are arranged beyond the solidification front of the extrusion body, emerging from the molten mass, and

means for adding and removing coolant to and from said bath comprising a header tank which is connected with the cooling bath container and which is height adjustable.

Claims

1. Apparatus for the continuous casting or drawing of a tubular extrusion body from a molten mass, which comprises a crucible for holding such molten mass, said crucible having a bottom outlet, a cooling device provided next to the outlet of the crucible through which such extrusion body runs, said cooling device comprising a cooling bath positioned in a container, with such extrusion body immersing into the level of the bath, and means for adjusting the distance between the crucible outlet and the cooling bath level which means are arranged beyond the solidification front of such extrusion body emerging from the molten mass, there being provided within such tubular extrusion body a column of cooling liquid and a filling of pressure gas which loads this column counter to the running direction of such extrusion body.

2. Apparatus for the continuous casting or drawing of an extrusion body from a molten mass, which comprises a crucible for holding such molten mass, a cooling device next to the outlet of the crucible through which the extrusion body runs, said cooling device comprising a cooling bath, consisting of a molten mass of an eutectic gallium-indium alloy, placed in a container, with the extrusion body immersing into the level of the bath, means for adjusting and maintaining the cooling bath level which means are arranged beyond the solidification front of the extrusion body, emerging from the molten mass, and means for adding and removing coolant to and from said bath comprising a header tank which is connected with the cooling bath container and which is height adjustable.