US2527545A - Apparatus for continuous castings - Google Patents

Description

Oct. 31,v 1950 N. P. (5088 2,527,545

APPARATUS FOR CONTINUOUS CASTINGS Filed May 2, 1947 2 Sheets-Sheet 1 37 40 INVENTOR NORMAN F. G055 fi a BY Md 74117 61 Fig-3 A ATTORNEYS.

Oct. 31, 1950 N. P. soss APPARATUS FOR CONTINUOUS CASTINGS 2 Sheets-Sheet 2 Filed May 2, 1947 is m w 5 P R. V 0 Z 1 Patented Oct. 31, 1950 UNITED STATES PATENT OFFICE APPARATUS FOR CONTINUOUS CASTINGS Norman P. Goal, Mayfield Heights, Ohio Application May 2, 1947, Serial No. 745,569

' s Claims. (01. 22-512) 1 This invention relates to improvements in the art of continuously casting metal.

One of the objects of the present invention is ,to provide a novel die open at both ends with means for holding the sections always in alined position, thus avoiding the distortion generally brought about by heating of the die. The construction also provides for expansion of the die in the general direction of metal travel so as to prevent distortion of the die due to localized heating and expansion.

Another object of the invention is the sudden or sharp increase in the cross sectional dimensions of the die at a point in the travel of the metal through the die, with the provision at that point of means for introducing lubricant between the surface of the formed metal and the adiacent die wall.

Another object of the invention is the provision of a slight sharp shoulder at any zone in the die passageway whereby at a predetermined horizontal level the cross sectional dimension of the die is increased, substantially entirely around the die, so as to momentarily release the contact between the skin of the congealing metal and the die wall.

Still another object of the present invention is to provide a die having walls completely surrounding a vertical passageway wherein the side and end walls of the die are separate wall portions and there being slight shoulders extending in a horizontal line entirely around all of the wall portions when they are assembled together in the die. 1 My invention also provides gravity actuated feed for feeding lubricant under constant pressure to the zone between the outer skin of the metal being formed and the adjacent die wall. I also provide a means for centering the cast metal in the die, utilizing varying, pressure on the lubricant feeding devices for this purpose.

Other objects and advantages of my invention will be apparent from th accompanying drawthrough one embodiment of my improved apparatus:

Fig. 2 is a transverse sectional view taken along the line 2-2 of Fig. 1;

Fig. 3 is an enlarged fragmental sectional view illustrating a portion of the interior surface of the die in the first chilled section;

Fig. 4 is an enlarged and exaggerated sectiona view of a portion of Fig. 1 illustrating a stepped construction of the die wall; I

Fig. 5 is an enlarged fragmental sectional view illustrating a modification of Fig. 3;

Fig 6 is an enlarged and exaggerated sectional view of a modification of Fig; 4 illustrating a stepped construction of the die wall both at the joints between die sections and at points in the intermediate portion of a section;

Fig. '7 is a fragmental perspective view showing a modification of my invention wherein the stepped construction is applied to a different form of die;

Fig. 8 is a sectional view enlarged taken along the line 8-8 of Fig. 7; while Fig. 9 is a sectional view taken along the line 8-9 of Fig. 8.

In the device of Figs. 1 and 2, molten metal I0 is held in a ladle i I generally of the foundry type and so formed of refractory material that the metal remains molten for the time necessary to teem the same into the casting die. The pouring lip of the ladle is mounted on a fixed pivot 12 and by means of the upward pull on cable 13 the rate of flow of the metal ma be readily controlled. Preferably a partition wall Ila is provided to hold back slag and the like so that clean metal may be poured. An electrical heating element it of the glow bar type is provided to keep the metal molten at the pouring lip.

Means is provided for introducing the molten metal into the open upper end of the casting die without turbulence and in a manner to prevent formation of air pockets in the upper end of the die. To this end means is provided for holding a small pool or reservoir I! of molten metal just prior to the flow of the metal into the die. Suitable refractory material It is provided to hold this pool, the refractory material being mounted on suitable supports ii. The refractory material is so formed at the point [to as to provide a dam over which the molten metal flows just prior to entering the pre-forming chamber Hi. This dam is heated by a glow bar is and other glow bars 20 are provided for insuring the fluidity of the metal in pool ill. The pre-forming chamber i8 has walls 2| of ceramic material adapted to with- 3 stand high temperatures such as those encountered when dealing with molten steel. The side wall Ma and one parallel thereto (not-shown) extend full height to the level Mb. The side nearer the pool 16 is cut away at lie to provide easy entrance of the molten metal over the dam a and into the top of the pre-forming chamber. The side opposite this is cut away a indicated at lid 'to provide a slag overflow port from which a run-off channel 22 extends. Refractory material completely surrounds the pre-forming chamber as indicated at 23. Glow bar devices 34 are provided tomaintain aneven temperature around the pre-forming chamber, while a g1owbar 25 is arranged in a recess directly above the,

open end of the casting die to insure molten metal at this point.

It should be understood that the cross section of the casting die may be of any desirable form, but for simplicity I have here shown a die for casting a square bar, as shown at 26 in Fig. 2. The cross section of the pre-forming chamber I3 is of almost exactly the same section, but preferably the pre-forming chamber is slightly less in width than the first forming chamber immediately beneath it, as will later appear.

The chilled die is comprised preferably of a plurality of short sections 31a, 21b, 21c and 21d, as shown in Fig. 1. I prefer to build these sections of short strong construction, say not much over nine to eighteen inches in vertical length, so as. to minimize distortion due to the heating of the die walls in operation. These chilledsections of the die may be alike and are of the form generally shown in section in Fig. 2. Here the die section 210 is formed in two L-shaped portions, the division line between the same being indicated at 23 in Fig. 2. The die walls are hollow, as indicated at 29 for the introduction of a cooling fluid.

such as water. Means (not shown) is provided individual to each of the sections 21a, 21b, etc., for the inlet and outlet of cooling fluid for each section.

Means is provided for maintaining vertical alinement of the various sections of the die. As shown in Fig. 2, four ears 30 are provided respectively at the four corners of the die extending diagonally outward and provided with openings 3011 through which pas the vertical alining rods 3|. The lower ends of these rods are mounted in fixed position in a structure 32, which is a portion of the same structure comprising the members l1 previously mentioned. The upper ends of the rods 3! enter suitable pockets 33 for holding the upper ends in alinement. It should be understood that the ears 30 are a fairly snug fit but free to slide along the rods 3|. Therefore the individual sections of the die are held in vertical alinement but are free to move individually and collectively downward on the rods 3| as required when the various sections are heated by the hot metal passing through the die.

Means is provided for holding the various sections of the die 21a, 21b, etc., in contiguous alined position, as shown in Fig. 1, while at the same time permitting expansion in a vertical direction. The means disclosed for this purpose comprises a set of heavy springs 34 which are in compression between the fixed platform 32 and a plate 36 which finishes off the bottom end of the die. The springs 34 are strong enough to-hold the various die sections in abutting relationship during the casting of the metal, but the forces tending toward expansion due to the effects of heat on the metal. of the die are sufficiently great to further compress the springs 34. By this arrangement I avoid distortion of the die walls which would normally take place if the die were held in fixed position between immovable structures both top and bottom.

Means is provided for introducing lubricating material between the skin of the newly formed metal and the die walls. To this end ports 36 are provided at various points along the length of the die and means is provided to feed into these ports lubricating material preferably in the form of finely divided material having lubricating properties, such as graphite, or such material may be provided in the form of a paste or an easily friable briquette. Just outside each of the ports 36 I have shown a feed hopper 31 attached to the wall of the die just above the port 36, as by means of bolts 33. It results from this construction that'as the. die sections expand due to heat, the feed hopper is always alined with its associated port 36. The finely divided lubricating material is placed in one of the hoppers 31, the bottom of which opens into a passageway leading to one of the ports 33. Means is provided for feeding this lubricating material under substantially constant pressure to the port 36. As here shown, such means comprises a plunger 38 having a snug lit in the passageway 31. A bell crank 40 pivotally mounted at 41 has a shorter arm 40a which has a pin and slot connection with the plunger 33. On the longer arm 40b of the bell crank is mounted an adjustable weight 42. The action of gravity on this weight gives a substantially constant pressure on the lubricating material on the passageway 31 and forces it through the associated port 36 so as to fill the interstices between the skin of the forming metal and the adjacent die wall. Referring to Fig. 2.

' the ports 36 are indicated in dotted lines as being substantially coextensive with the sides of the billet or bar 43 which is formed in the die. Thus, lubricant is supplied along the full width of the bar 43 around its entire periphery at each point where the ports 36 are provided. It will be noted in Fig. 2 that there is a small square 44 at each corner of the die wall between ports 36. It is these small square portions at each corner which.

v the die will withstand less pressure than when it is cooled by further progress down the die. Also, as is well understood, the metal, as it becomes cooler, will contract more, allowing a. slightly greater space between the skin of the metal and the interior wall of the die near the lower end of the latter.

Another form of lubricant may be supplied near the outlet end of the die, as is illustrated directly beneath the die section 2102. Here four ports 46 are provided similar to the ports 36 above described. A block of friable lubricating material 46 is placed in each port 46 and a plunger 41 in each port is used to apply pressure to the block of lubricating material actuated by a weight 42 on a bell crank 40, as described in connection with the pressure applying means previously described.

As the metal emerges from the bottom of the die, it has a skin strong enough to support the metal in the center even though the latter has not yet completely solidified. It is preferable in the case of metals of high melting point to supply water sprays 48 at this point to hasten the solidincation of the metal. A pair of coacting pinch rolls 4! is usually supplied for withdrawing the formed metal from the die. The rolls shown in Fig. l have V-shaped surfaces forming a 90 angle on each roll 50 that the two rolls together embrace the four sides of the bar 43. In spite of the best efforts to withdraw the bar 43 with uniform lateral pressure, there is a tendency at times for the metal forming in the die to travel toward one of the die walls oif center, thus tending to scrape and scratch against one side of the die.

It will be noted that no bulk lubricant is supplied to the metal in the section 210 which is the chilled forming chamber which is below the ceramic pre-forming chamber 18. If lubricant is freely supplied to steel in molten condition, it would either burn and disappear or it would chemically unite with the metal to carburize it. My theory of the action which takes place at the upper end of the die is that solidification begins to occur at approximately the zone indicated at 55 near the top of section 21a. At first there is only a very thin skin formed on the congealing metal, but as the metal progresses downwardly through section No this skin becomes strong enough to shrink away from interior walls of the die and to exert some confining effect upon the congealing metal in the center of the die. Where a skin of this thickness is formed, I desire to begin the introduction of external lubricant as soon as possible. To this end, I desire to form the section 21a relatively short. It may be as short as two inches when casting a steel billet four inches by four inches in a mold four feet long.

Somewhere near the bottom of section 21a I believe that the hydrostatic head of the molten metal in the top of the die is tending to press the newly formed skin of the congealing metal against the inner walls of the die, while at the same time the contact of the hot metal with the cold die causes the congealing metal to tend to shrink away from the die wall. Therefore, at this point, which is at the lubricant feeding ports 36 at the level 53 indicated in Fig. 4, I introduce a lubricant such as the finely divided graphite shown at 51. As l'ater described in connection with Fig. 4, the cross-sectional dimension of the die increases slightly as the metal passes from section 21a to section 21b. Thus at the zone 53 I suddenly relieve the friction of the congealing metal pressing against the inner walls of the die while supplying lubricant through the ports 38. and this aids greatly in moving the congealing metal through the die.

According to the above explanation, there is a short distance in the section 21a wherein it is desired that the newly forming metal should not stick to the walls of the die but where it is impractical to supply the type of lubricant furnished at the ports 36 later on. I have discovered two ways for solving this problem. In Fig. 3 I have illustrated in greatly exaggerated fashion a fragmental portion of the interior surface of the die section 21a. wherein the surface 5| is in contact with the bar 43. I prefer to form the section 21a of a metal with high heat conductivity, such as copper. This copper is given a rough cut 5!, after which colloidal graphite 50 is applied to the rough surface of the copper and forced into the pores of the copper b tarnishing. I find that a surface formed in this fashion will retain its lubricating qualities next to molten or hot metal for a long period of time, while at the same time interfering only slightly, if at all, with the heat conducting qualities of the section 21a, which is water cooled through passageway 29, as previously mentioned. I believe that the successful use of this thin layer of graphite 50 at this point rests on the fact that there is practically no temperature gradient in the graphite layer. In other words, the graphite is substantially at the same temperature as the metal of the chilled section 21a and at this low temperature there is substantially no chemical reaction between the hot metal and the graphite.

In Fig. 5 I have shown another method of treatin the interior surfaces of the die section 21a to obtain long life and satisfactory results. Here the interior wall of the section 21a is given a thin plating 58 of a metal which is non-alloying with respect to the metal being cast. In the case of steel, a plating of silver is satisfactory. In the case of copper, the plating might be molybdenum. The plating 58, while not a lubricant, nevertheless provides a non-wetting and non-sticking surface at this point.

I have stated earlier that I find it very important for the easy advance of certain metals through my improved die to slightly increase the internal dimensions of the die at several points along its length. In Fig. 4 I have greatly exaggerated this condition for the sake of illustration. The change in dimension between the ceramic pro-forming section 2i and the top die section 21a at the level 52 is optional and may be practically anything from zero to one-half inch increase in over-all dimension in the case of a steel billet approximately four inches by four inches in section.

A change in the cross sectional area of the die is of greater importance at the level 53 where the metal passes from section 21a to 211). Here the increase in the cross-sectional dimensions of the die is preferably of the order of one-thirty-second to one-eighth inch in the over-all dimension of a steel billet such as mentioned above. This structure may be repeated at the levels 54 and 55 if desired. It results from this construction that lubricant is supplied through ports 36, say at the level 53, where the cross-sectional area of the die suddenly increases. Thus the friction resisting the movement of the metal through the die is suddenly released at the level 53 and at the same time lubricant is supplied through the ports 36 between the skin of the metal and the inner wall of the die to insure good lubrication and protection of the die walls.

I find that apparatus constructed as above described will continuously cast a metal bar which is free of blow holes and free of slag if the level in the pre-forming chamber l 8 is occasionally raised to run off the slag through the passageway 22. The hydraulic head provided by the molten metal in the preforming chamber is sufilcient to form a very dense metal in the first chilled section 21a and by pre-forming the metal in chamber [3 to substantially the cross section of the rest of the die, the metal enters easily into the chilled portion of the die because of the slight increase in sectional dimensions at the level 52. The metal movement is further facilitated in the rest of the die by means of the stepped constructions at the level 52, 53, 54, etc., and by the introduction of lubricant through the ports 36. The result is a continuous bar 43 of metal having a controlled crystalline structure and very fine surface characteristics, as well as freedom from internal imperfections, as previously pointed out. At the same time, the short strong die sections 21a, 21b, etc., are subject to very little distortion, are held in permanent alinement by the guide rods 3|, while the individual die sections may expand longitudinally as the ears 30 slide along the guide bars 3|.

In Fig. 6, I have shown a view similar to Fig. 4 illustrating a modified construction including all of the features of Fig. 4 including the stepped back construction at the zones 52, 53' and 54 in all respects similar to that just described at 52, II, and 54. In addition, however, stepped back construction is shown at 59a in section 59, at 60a in section 60 and at GM in section 6|. At each of these points 59a. 60a and Gla there is a horizontal shoulder extending entirely around the interior die wall of the order of a few thousandths of an inch so as to slightly increase the crosssectional dimensions of the die as the metal passes that horizontal zone on its travel downwardly. This stepped construction is necessarily exaggerated in Fig. 6 as it was in Fig. 4. Obviously, where the cross-section of the die is anywhere from two inches to several feet, a shoulder of the order of say three thousandths of an inch would not show on the drawings at all. While the drawing gives the impression of a taper, there is no such appearance in the finished die. It appears to be of one cross-sectional dimension for its entire length. There is a very important function performed by the slight offsets indicated at 52', 63, 54', 59a, 60a and Ma whether or not lubricant is introduced at the same zone where the shoulder occurs. I have discovered that the first outer skin which forms on the metal as its starts through the hollow die is very thin and easily ruptured. Such an accident will spoil the surface of the steel and the quality of the metal in the interior of the section. In a mold section having the same cross-sectional dimension throughout the vertical passageway or gradually tapered so as to increase the cross-sectional dimension of the die passageway as the metal moves downwardly, the f errostatic pressure of the molten interior continuously presses the tender outside skin against the die wall and this creates sufficient friction to hold up the even movement of the metal through the die with consequent occasional rupturing of the tender skin. By the use of the slight shoulders indicated, each time the die wall is sudden y increased in cross-sectional dimension, the friction between the tender skin and the wall of the mold is suddenly relieved at all points around the horizontal zone, and the advance of the congealing metal is facilitated. The shoulder dimension at the various points indicated should not be so great as to cause a breakage of the thin skin of the congealing metal.

Another advantage of the sudden increase in the sectional dimension of the die as indicated at the points 59a, 66a and Ma is due to the peculiar action of the freshly formed skin of the congealing metal. Wherever this skin touches the cold die wall it tends to shrink away. However. the ferrostatic pressure of the molten interior tends to hold the thin skin against the cold wall which often causes local cold spots in the newly formed skin. At these points the congealing metal tends to cling to the die wall. By the use of m invention, the contact of the skin with the die wall is suddenly released at all points around a hori- I are provided of which only two are indicated at 62 in Fig. '7. The die illustrated is for casting .a slab section which comprises a longer side wall 63 and a shorter end wall 64. Each of these walls is formed by a plurality of sectional wall portions arranged vertically one above the other as ex plained in my above-mentioned copending application. Each wall portion at its upper edge has radially extending ears 63a and 64a by means of which the wall portions are suspended in the corner posts. Each of the wall sections is hollow as shown in Figs. 8 and 9 and a provision is made for supplying cooling water in the hollow central portions 63b and 64b respectively.

In this modified form of die, the present invention is applied by forming a slight sharp shoulder 65 in the wall portion 63 and a similar shoulder 66 at the same horizontal level in the wall portion 64. It will be understood that the opposite side and end wall portions have been omitted for clearness, but similar shoulders are formed in these wall portions so that a continuous slight shoulder of the order of a few thousandths of an inch is provided entirely around the four die walls at the horizontal level selected. Therefore, in the zone 61 below the shoulders 65 and 66 the crosssectional dimensions of the die are a few thousandths of an inch greater than in the zone 66 above the shoulders. It will be understood by those familiar with machining operations that it would be very difficult to machine the shoulders 59a, 60a and Hz: in the mid portion of an integral four-wall die section. In the construction shown in Fig. 7, however, an end mill may be utilized in the zone 61 so as to accurately machine the portion 61 to leave an accurate shoulder at the level Or at the level 66. If curved cornc-rs or fillets are provided at the points 69 as indicated, this may be done by grinding an appropriate curved face on the end mill. Obviously. the shoulders 65 and 66 have been exaggerated in the drawings as it would be impossible to show a few thousandths of an inch on the scale of the drawing. With this form of my invention therefore, I am enabled to provide the slight sharp shoulder with great ease and accuracy and the wall portions, when assembled, will exactly aline the shoulders 65 and 66 by engagement of the ears 63a and 64a in the notches 62a of the corner posts.

This application is a continuation in art of my copending application Serial No. 528,045, filed March 25, 1944, for Method and Apparatus for Continuous Casting, now abandoned.

What I claim is:

1. Apparatus for continuously forming metal comprising a die having cooling walls completely surrounding a central vertically extending passageway through which metal passes downwardly as it congeals, and a sharp shoulder of a few thousandths of an inch depth and extending substantially uninterruptedly about the interior faces of said walls at a horizontal level and providing a slight but sudden increase in cross-sectional dimensions of said passageway below said level.

2. Apparatus as in claim 1 wherein said die comprises vertically alined sections, and said sharp shoulder is provided at a level intermediate the top and bottom of one of said sections.

3. Apparatus as in claim 1 wherein said die comprises vertically alined sections, and said sharp shoulder is provided at the level where two of said sections meet.

4. Apparatus as in claim 1 including means for introducing a lubricant between said metal and said interior faces of said die walls at the level where said sharp shoulder is provided.

5. Apparatus as in claim 1 including means for introducing a lubricant between said metal 10 and said interior faces of said die walls below the level where said shar shoulder is provided.

NORMAN P. GOSS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 1 Number Name I Date 152,040 Lavroff June 16, 1874 388,336 Boulton Aug. 21, 1888 2,225,373 Goss Dec. 17, 1940 2,276,657 Junghans Mar. 17, 1942 15 2,284,704 Welblund et a1. June 2, 1942 2,363,695 Ruppik Nov. 28, 1944

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