US3344846A

US3344846A - Apparatus for continuously horizontally casting high melting metals, particularly steel

Info

Publication number: US3344846A
Application number: US483104A
Authority: US
Inventors: Alexander V Rossing
Original assignee: Deutsche Edelstahlwerke AG
Current assignee: Deutsche Edelstahlwerke AG
Priority date: 1964-09-01
Filing date: 1965-08-27
Publication date: 1967-10-03
Anticipated expiration: 1984-10-03
Also published as: CH437661A

Description

Oct. 3, 1967 A. v ROSSING 3,344,846

APPARATUS FOR CONTINUOUSLY HORIZONTALLY CASTING HIGH MELTING METALS, PARTICULARLY STEEL Filed Aug. 27, 1965 4 Sheets-Sheet l PRIOR ART A. v. ROSSING 3,344,846

APPARATUS FOR CONTINUOUSLY HORIZONTALLY CASTING HIGH MELTING METALS, PARTICULARLY STEEL Filed Aug. 27, 1965 4 Sheets-Sheet 2 Oct. 3, 1967 5 we, %M%YMW Oct. 3, 1967 Filed Aug. 27, 1965 Fig. 3a

A. v. ROSSING APPARATUS FOR CONTINUOUSLY HORIZONTALLY CASTING HIGH MELTING METALS, PARTICULARLY STEEL 4 Sheet-Sheet 5 jm emo r: W

Oct. 3, 1967 A. v. ROSSING 3,344,846

APPARATUS FOR TINUOUSLY HORIZONTAL-LY CASTING v HIGH MELT METALS, PARTICULARLY STEEL Filed Aug. 27, 1965 4 She ets-Sheet 4 United States Patent O 1 Claim. (CL, 164281) ABSTRACT OF THE DISCLOSURE In apparatus for horizontally continuously casting high melting metals, especially steel, in which the molten metal enters'an axially reciprocating mold through a pouring spout attached to a stationary pouring vessel and at least partially solidifies in the mold, the feature that the mold has an extension which has a diameter smaller than that of the mold and is rigidly affixed to the entry end of the mold to provide the mold with an end shoulder.

Vertical continuous casting of high melting metals has been developed to industrial maturity within recent years and many steel works today avail themselves of the method to an increasing extent. On the other hand, horizontal continuous casting is still in the experimental stage and, so far, the success of the method has been problematic.

The reason for the unceasing eflforts that have been made to perfect the horizontal continuous casting technique of high melting metals, especially of steel, is to be found in the great advantages the horizontal method olfers over vertical continuous casting. These advantages are commonly known and they need here be only briefly enumerated.

(1) Minimum spatial requirements and low investment cost:

(a) the low structural height of the plant permits it to be installed in steel works in any ordinary foundry shop,

(b) additional hoisting means (such as cranes, inclined elevators) are not required, and

(c) the supporting structure of a horizontal continuous casting plant is simple and uncomplicated;

(2) Minimum number of operating personnel needed:

(a) the entire plant can be operated from the shop floor and elevated working platforms need not be provided;

(b) regulation of the casting level in each individual mold is unnecessary because all the molds together with the pouring vessel form a closed system;

(3) Operational and metallurgical advantages:

(a) the melts need not be significantly overheated because handling times and distances are short, conventional foundry cranes can be used without transferring ladies from one handling device to another, so that the temperature losses prior to pouring are minimised;

(b) temperature losses during the actual casting process are low, because the melt passes through the (protective gas) atmosphere only on its way from the ladle into the pouring vessel, whereafter it is entirely contained in a closed system;

(c) for the same reason as that described in (3) (b) the steel takes up little oxygen on its way from the ladle to the finished casting;

(d) structural and metallurgical problems otherwise involved in deflecting and straightening the casting do not arise.

Many proposals have already been made to reduce the structural height of vertical continuous casting plant. The first step in this direction was to deflect the vertically issuing casting into the horizontal, but the reduction in structural height thus achieved is only slight. The next step involves casting the metal into arcuate molds. Although this idea appears to permit substantial reductions in structural height it nevertheless presents structural difliculties apart from metallurgical problems, which tend to have an unfavourable effect on the cost of installation and maintenance of such equipment. Moreover, this latter process is still in the experimental stage and its development for industrial use has not yet been completed.

The effort to reduce the overall height of the plant continuously crops up everywhere in the development of the vertical continuous casting technique. Undoubtedly the problem will not be finally solved until a way has been found of continuously casting high melting metals such as steel in horizontal casting molds.

The most favourable procedure, both with regard to the cast surface obtained and the rate of casting achieved (i.e. output), which for the above described reasons several producers have experimentally used, is as follows:

The stationary pouring vessel has a pouring spout which projects into the oscillating mold, closing the entire cross section of the entry end of the mold. The continuouscasting is withdrawn from the mold in conventional manner at a constant rate by carrying it on a live roller bed, and the casting is finally cooled to complete solidification in a subsequent cooling stage in which it is sprayed with water.

One major reason why, despite the above listed major advantages, this horizontal continuous method of casting could not be used for the industrial production of steel is that at short irregular intervals the castings always exhibit so-called transverse seams. These transverse seams are faults extending around the entire casting perpendicularly to its axis and they considerably weaken the casting. It is often possible to break a continuous casting at a seam with one blow of a hammer. These faults not only constitute a danger, because the casting behind the mold may burst, they also render the casting quite useless for further processing, even if it is otherwise flawless.

It is the object of the present invention to provide an apparatus and a method for the production of continuous castings of high melting metals, particularly steel, of any length, by a horizontal continuous casting technique in which the above faults in the casting do not arise.

The proposed apparatus as well as the method will be more readily understood by reference to FIGS. 1 to 3 of the accompanying drawings. FIGS. la to 1d first of all schematically illustrate the method which has in the past been unsuccessfully used for continuously casting steel to produce horizontal castings of circular section. The individual drawings in FIGS. 1a to 1d show consecutive stages in the casting procedure and they illustrate how and why the above mentioned transverse seams form.

A longitudinal section of the horizontal mold 1 which has a cylindrical internal cross section is shown in FIG.

1a. The mold is cooled in a manner well known in the art and oscillates in the horizontal direction. 2 is a longitudinal section of the pouring spout which projects into the front end of the mold. A dummy billet 3, in the same way as in vertical casting, permits the casting to be withdrawn when a casting cycle begins and the leading end of the casting to be pulled on to a live roller bed. The head of the dummy billet 3 carries a heavy machine screw 4 as well as between one and three sealing plates 5 which may be asbestos. Between the end face 6 of the pouring spout 2 and the sealing plates is the actual casting chamber 7. When casting begins the molten steel enters this chamber and solidifies by exposure to the cooling effect.

of the cold or cooled casting mold in the manner indicated by shading. The solidified steel embraces the head of the machine screw 4 and thus forms a withdrawing head 8. At the same time an annular region 9 of solidified steel forms adjacent the end face 6 of the pouring spout 2 due to the additional heat the pouring spout extracts from the metal, and this solidified zone adheres more or less firmly to the end of the spout.

As soon as chamber 7 is full of molten steel the dummy billet 3 is slowly withdrawn in the direction of arrow 10. Meanwhile solidification continues and proceeds from the withdrawing head 8 and from the end of the spout 2 along the wall of the mold. The further extraction of heat proceeds exclusively through the latter while the core of the steel remains liquid. The front end of the casting at 8 is finally withdrawn from the mold with the aid of the dummy 3. The rate of withdrawal must depend upon the existing cooling conditions inside the mold in such manner that the solidified shell 11 of the casting adjoining the solidified head at 8 when it emerges is sufiiciently strong to contain its liquid interior 12 (FIG. 1b).

FIG. 1b shows that after an indeterminate number of oscillations of the oscillating mold 1 the solidified shell 13 which extends from the solidified annulus 9 finally detaches itself from the face 6 of the spout 2. At 14 this part of the solidifying shell joins the part of the shell 11 which extends from the casting head and the whole is finally withdrawn from the mold. A fresh shell 15 begins to form adjacent shell 13 and progressively continues to extend along the mold wall. Since the rear end of shell 13 has already considerably cooled when it becomes detached from the spout 2 the joint at 16 is not a very good weld and thus gives rise to the formation of the transverse seam 16.

As illustrated in FIG. a fresh solidified annulus 17 of steel forms on the end face of the pouring nozzle 2 and the process described above will therefore repeat itself. However, sometimes the circumstances illustrated in FIG. 1d may arise. The circumferential shell which originates at and grows from the solidified annulus at 17 may detach itself rather later from the end of the pouring nozzle 2. The weakest point 18 between the shell and annulus 17 will then have moved into such close proximity to the end of the mold that it cannot become very much thicker before emerging therefrom. Bursting of the casting is then hardly avoidable, particularly since it is impossible to determine the course of events during the casting procedure and to control the casting rate in accordance therewith.

It has been found that the only possible way of avoiding these grave defects which consist in the formation of the transverse seams and in the possibility of the casting bursting, is to cause the solidified annuli 9 and 17 to detach themselves from the spout 2 at regular and the briefest possible intervals.

The invention therefore proposes apparatus for horizontally continuously casting, particularly steel, in which the metal enters a cooled axially oscillating mold through a pouring spout, which is characterised by an extensionat the entry end of the mold having an inside diameter which is less than that of the mold itself. This novel mold extension consists of a metal or metal alloy of good ther- 4 mal conductivity, such as copper or a copper alloy, and it is cooled in the conventional manner casting molds are cooled.

An embodiment of the proposed casting machine for continuous casting of circular sections is first of all illustrated in FIG. 2. The entry of the horizontal mold which is cooled in conventional manner is indicated in this drawing at 19. The proposed entry extension which here consists of a copper sleeve 20 and a steel shell 21 is attached to the entry end of the mold. A suitable coolant is circulated through the annular gap at 22, the coolant entering say at 23 and leaving at some other appropriate point not specially shown in the drawing. The inside diameter of the extension sleeve 20 or of a single-part extension must be between 2 and 20% smaller than the internal diameter of the mold itself, according to the diameter of the continuous casting, the smaller value applying to large cross sections and the greater to castings of smaller cross section. The extension forms a shoulder 24 at the entry end of the mold. The presence of this shoulder 24 ensures that the solidified steel is entrained by the motion of the mold and lifted off the end face of the pouring nozzle 25.

In order to reduce the friction between the extension sleeve 20 and the pouring nozzle 25 the sliding surfaces are supplied with a suitable lubricant through channels 26. The inside surfaces, that is to say the sliding surfaces of the extension sleeve 20, may also be hardened or chormised. The steel shell 27 which carries the pouring spout 25 and which is attached to the pouring vessel 28 need not necessarily be cooled because the end face of the pouring spout 25 transmits most of the heat it extracts from the liquid metal to the extension sleeve 20.

The molten metal from the pouring vessel 28 enters the casting chamber 30 through channel 29. Channel 29 is insulated by a refractory lining 31 from the pouring spout 25 and the steel shell 27.

The procedure used for preventing the development of the transverse seams with the aid of the mold extension proposed by the present invention consists in cyclically axially reciprocating the mold and its extension during the casting process. Unlike the method of oscillation conventionally used the proposed reciprocation of the mold proceeds in the following three stages:

1st stage: the mold is moved from its starting position in casting direction,

2nd stage: the mold is returned in the opposite direction into starting position,

3rd stage: the mold remains in starting position for a brief period before beginning the movement of the first stage of the cycle again. The speed of the 1st stage movement is roughly equal to the casting rate. The return movement (stage 2) is at a higher speed.

"For an explanation of the manner in which the pro- F posed machine functions by the method according to the r cooled extension. In FIG. 3a the mold is assumed to be in starting position and the pouring spout 34 projects far enough into the extension for its end face 35 to be substantially flush with the annular shoulder 36 formed by the end of the extension 33 in virtue of its smaller internal diameter than that of the casting chamber 37.

When casting begins the steel solidifies in a manner similar to that illustrated in FIG. la. An annular solidified zone of steel marked 38 in FIG. 3a again forms. However, during the forward movement of the mold in the first stage of the reciprocatory cycle this solid annulus is lifted off the end face 35 of the pouring spout by shoulder 36 which entrains the steel that has solidified and attached itself to the spout at 38. The space previously occupied by the annulus immediately fills with liquid steel which forms a fresh solid annulus indicated in FIG. 312 by 39. During the second phase (return) of the mold the weakest point 40 at the end of the freshly formed solid annulus melts, or it is torn by the uniformly advancing casting. The annular space 41 which opens up as shown in FIG. 30 fills with liquid steel and this immediately begins to solidify as indicated in FIG. 3d, coalescing with the two

solid annuli

38 and 39 whilst the mold remains stationary during the third phase of the cycle. Hence the position illustrated in FIG. 3a is reconstituted and, during the following first stage of the next oscillatory cycle of the mold, the solid annulus 39 is again lifted off the end face of the pouring spout, followed by a repetition of the above described process.

In View of the rapidity with which consecutive stages take place, the joints, of which one is indicated at 42 in FIGS. 3d and 3e, fuse together without a fault.

The explanations hitherto givenas already mentionedrelated to the horizontal continuous casting of billets of circular cross section. It is naturally a matter of similar interest to be able to produce square, rectangular or even slab-shaped castings in the same way. This would be practically impossible to do by the conventional methodquite apart from the difficulties that have 'been describedbecause it is also a matter of the greatest difliculty to fit a pouring spout of any other than circular cross section sufliciently accurately in a mold of corresponding cross section and to achieve the necessary tight seal at the mold entry end. Moreover, the irregular thermal expansion of such pouring spouts leads either to leakage or to interference with the freedom of movement of the mold when the fit becomes too tight.

The proposed mold extensions which has a cross section smaller than that of the mold itself also affords the possibility of horizontally casting other than circular sections. To this end a pouring spout and an extension of circular section are used and only the mold corresponds to the non-circular section it is intended to cast. Embodiments of such arrangements are shown in FIGS. 4a to 7b which schematically represent possible ways of casting square or rectangular sections. The mold 43, the extension 44 and the pouring spout 45 in each of the following drawings are seen in the direction A in FIG. 4a.

For casting flat rectangular sections (slabs) having cross sectional aspect ratios exceeding 2:1 it is advisable to provide two or more pouring spouts and a mold extension provided with the necessary holes, as schematically shown in FIGS. 6a to 7b.

In each case, and as illustrated in FIGS. 4a to 7b the internal diameter of the extension(s) must be smaller than the minimum internal diameter of the mold itself.

What I claim is:

Apparatus for continuously horizontally casting high melting metals, especially steel, comprising a horizontally disposed axially reciprocable continuous casting mold and a pouring spout attached to a stationary pouring vessel and by way of which the molten metal can enter and at least partly solidify in the mold, said mold having rigidly aflixed to its entry end an extension having a channel which is axially aligned with the mold and has a diameter to form with the internal surface of the mold a shoulder.

References Cited UNITED STATES PATENTS 1,088,171 2/1914 Pehrson 2257.2 2,779,073 1/1957 Osborn 2257.2 X 3,040,396 6/1962 Hudson 2257.2 X 3,045,299 7/ 1962 Steigerwald 2257.2

FOREIGN PATENTS 1,281,701 12/ 1961 France. 1,136,796 9/ 1962 Germany.

I. SPENCER OVERHOLSER, Primary Examiner.

R. S. ANNEAR, Assistant Examiner.