US3324931A - Method of deflecting towards the horizontal a curved continuously cast descending billet - Google Patents

Description

June X3, 1967 A. BUNGEROTH ET AL 3,324,931 METHOD OF DEFLECTING TOWARDS THE HORIZONTAL A CURVED CONTINUOUSLY CAST DESCENDING BTLLET Filed May 4, 1964 2 Sheets-Sheet i 7km Amway h H I June 13, 1%?

A BUNGEROTH ET AL 3,32433 METHOD 0? DEFLECTING TOWARDS THE HORIZONTAL A CURVED ENDING BILLET CONTINUOUSLY CAST DESC 2 Sheets-Sheet 2 Filed May 4, 1964 i? mmm: da/ iv mm! a 4 s Mme-m. 37 72ml M me;

United States Patent 3,324,931 METHOD OF DEFLECTING TOWARDS THE HORI- ZONTAL A CURVED CONTINUOUSLY CAST DE- SCENDING BILLET Adolf Bungeroth and Hans Schrewe, Duisburg, Germany,

assignors to Mannesmann Aktiengesellschaft, Dusseldorf, Germany, a corporation of Germany Filed May 4, 1964, Ser. No. 364,566 Claims priority, application Germany, May 3, 1963, M 56,686 3 Claims. (Cl. 164-82) The invention relates to continuou casting, and relates more particularly to methods of and machines for deflecting towards the horizontal a continuously cast descending billet.

It is well known to use in continuous casting smooth molds and to deflect the billet that emerges downwardly from the mold by sideward deformation, and to bend the billet straight after the deflection into the horizontal, throughout the arcuate path, has been completed.

It is furthermore known to utilize curved molds, for the continuous casting of steel and metals, to shift the descending billet to the horizontal plane at a lower required plant height.

It has furthermore been proposed to straighten the billets after they have run through a curved path that is formed along the periphery of a circle along one-fourth of the entire periphery.

Reference is had to the application Speith et al., Ser. No. 319,004, filed Oct. 25, 1963, now abandoned, in which the instant two applicants were joined by a third.

In practice, for the sake of the quality of the billets, the aforesaid methods require, or at least favor, to deform, namely to bend and thereafter to straighten the billet only after the core of the billet is no longer liquid and the billet thus throughout its thickness has completely been solidified.

In dimensioning a continuous casting plant of this type, the height and the curvature of the deflecting path is a function of the time required for solidification of the billet and of the casting speed for the desired casting cross section.

The transport rolls, the cutters and the straightening devices usually are disposed at a point that is beyond the reach of any liquid portion of the core at any possible casting speed for that machine. Similarly, at arcuate casting machines where the billet passes through a circular arc, which is characterized by the selection of such a small radius of curvature that the liquid core projects past the one-fourth of the entire periphery of the circular arc into the horizontal, the transport rolls and cutters are also arranged only at a point where the billet is throughout its thickness completely solidified. The straightening devices, however, exert their deformation forces at a point of the billet where the billet is only partially solidilied on the interior. This has the disadvantage that the solidification of the billet is constantly being disturbed, and as this deformation surpasses a tolerable limit of the partially solidified billet, there sometimes result damages to the billet, for instance in the form of breaks. This disadvantageous tendency is aggravated by the fact that in changing from a curved section into a straight horizontal section, the billet is subjected throughout a very short zone to the deformation forces of the straightening device; in other words, the necessary straightening of the billet will suddenly in full force be applied practically in a single cross-sectional plane.

Furthermore, there are continuous casting machines known in which the metal is cast in straight smooth molds, and the billet thereafter is bent sidewardly away from the mold, and transport rolls are arranged near the lead- 3,324,931 Patented June 13, 1967 ice ing point of the sump of the billet. This method of the prior art roposes to maintain small the degree of deforming during bending by making the radius of curvature large enough so as to be at least thirty times the width of the billet. This method, of course, requires large radii of curvature, and accordingly leads to great heights of plants. Furthermore, this method is not usable for all steel qualities.

It is accordingly among the objects of the invention to avoid the drawbacks of the prior art and to provide improved methods and means for the controlled curving and straightening of continuously cast billets.

It is a further object of the invention to provide for casting of billets free from breaks.

It is another object of the invention to provide for continuous casting of metal billets at low height of plant.

It is still another object of the invention to provide for continuous casting of metal billets dispensing with the need for costly straightening devices.

With the above and other objects of the invention in view, the invention consists in the novel methods, construction, arrangement and combination of various devices, elements and parts, as set forth in the claims hereof, certain embodiments of the same being illustrated in the accompanying drawings and described in the specification.

The instant invention provides for the continuous casting of a metal billet which is discharged from a mold downwardly in partially solidified form and the billet later on will be solidified completely at a distance from the mold; the deformation in accordance with the invention takes place already within the orbit of that part of the billet in which the core is still liquid, so that the billet is only partially solidified; for arcuate deflecting throughout an arc of the instant invention provides for commencing the deformation already in the arc in such a manner that the rolls of the deflector mechanism, such as the deflector cage are not disposed along a single circular arc of steady radius but along a more complex curve. The rolls define a continuous curved path which is composed of continuous arcuate portions or arcuate segments that are formed each along a circular arc that is described each by a different radius; and the different radii stepwise increase or decrease proportionally, somewhat in the nature of an elliptic or parabolic segment. The radii thus change proportionally with increasing distance of the path from the mold, but such proportional change need not be linearly proportional, but may be proportional in accordance with a different and more complex mathematical relationship, and includes direct proportionality as well an inverse'proportionality. Putting it differently, the path proceeds along a continuous curve, but the successive portions thereof are circular arcs formed by different describing radii, and the radii change proportionally successively as one proceeds along the curved path.

In an arcuate casting device the selection of the successive radii depends, of course, from the radius of curvature of the curved mold.

The deforming, namely stressing or swaging must, however, not surpass a harmless degree. By providing a fairly large amount of small deformation steps, the instant invention accomplishes a total deformation of the billet deflecting it into the horizontal within a wide range, and yet all damage to the core is avoided although the deformation takes place at points of the billet which are not completely solidified. The degree of deformation for each step preferably should be the same, but may vary among the steps.

The deformation of a billet upon bending for curving and, respectively, upon straightening involves stressing and, respectively, swaging of the most-deformed fiber as compared to the neutral fiber of constant length. This deformation may be expressed in percent of the change in length. Even though in the ensuing description it will be assumed that the neutral fiber even in billets which are only partially solidified, coincides with the longitudinal axis of the billet, and the most-deformed fiber is the outermost fiber, all the following explanations will be valid for the actual position of the neutral and the critically deformed fiber of the billet. The term billet as used herein includes strands of circular, square and rectangular cross section.

A billet that is formed in a straight vertical mold, and continues thence on a straight vertical path of solidification is, of course, not subjected to any deformation. The same can be said about a billet that is formed in an arcuate mold and continues thence in a circular peripheral path of solidification, which path is described by the same radius as that of the arcuate mold. Deformation occurs only during bending upon transition from a straight path into an arcuate path and, vice versa, during rectification or straightening of the same billet, and also during transition of the billet from an arcuate path with one radius into other arcuate paths with different radii.

Where there is a good cradling of the billet by means of a deflector mechanism, such as a deflector cage with deflector rolls with the rolls arranged closely together, the deformations of the billet will be restricted to a short deformation zone which is related to the mutual distance of the pairs of deformation rolls. The restrictions to short deformation zones are rendered possible by the relatively slow billet speed upon high recrystallization speed.

In such a situation it would be possible, even for use with thick billets which are cast in an arcuate mold, to provide a small circular are which would lead directly into a straight horizontal path without any intermediate step; this, however, would lead to a deformation that would be strongly damaging to the material. These damages may, on the other hand, be avoided by the provision of a stepwise continuous transition from the circular arc of smallest radius into arcs with increasing radii and hence of small deformation between the steps. In this manner it is possible, in accordance with the invention, to deflect even thick billets from a vertical or arcuate or inclined mold into the horizontal or oblique position within a curved path of a hitherto unattainable smallness and a considerable saving of space and height of plant.

The foregoing and other objects of the invention will be best understood from the following description of exemplifications thereof, reference being had to the accompanying drawings, wherein:

FIG. 1 is a schematic elevational view, partly in section; and

FIG. 2 is a schematic elevational view showing a series of interrelated diagrams.

In carrying the invention into effect in the embodiments which have been selected for illustration in the accompanying drawings and for description in this specification, and referring now particularly to FIG. 1, there is provided :1 schematically indicated arcuate mold with an arcuate path a-e for the billet of ellipsoid paraboloid shape. FIG. 1 shows the construction of this path which is formed for example by rolls 11, and is composed of a series of successive continuous arcuate portions a-b, b-c, cd and d-e, and each arcuate portion is formed along a circular arc that is described by a radius. The radii of the succeeding arcuate portions differ from each other. Thus, the path commences at the mold with a circular arc of small radius a1, b1, which may, as shown in FIG. 1, coincide with that of the mold. The circular arc runs from a to b peripherally about the same center 1, so that the billet will proceed from a to b without deformation.

At b, the path proceeds from b to c as a circular arc with a radius b2, c-2 about the center 2; the transition at the point b is continuous, with the tangents of the two radii b1 and b-2 coinciding at b. The radius b2 is larger than the radius b1.

In a similar manner the path continues through the arcuate portion c-d with the increased radius c3, continuously from b-c to cd, and again in a similar manner through the arcuate portion de with the greatly increased radius d-4, continuously through the point d. The center 1 is disposed on the radius b2, the center 2 on the radius c-3, and the center 3 on the radius d-4, so that there is smooth continuation owing to the coinciding of tangents not only as previously described at the point b, but also at the points 0, d and e. The curvatures for the individual arcuate portions flatten out in the direction from a to e. The prolongation of the path from e to f is straight, substantially horizontal, and again at e there is a continuous transition.

The billet proceeding from the mold to its horizontal section at e thus starts with a small radius curvature and ends in a straight substantially horizontal path.

If the path had been continued throughout one-fourth of a full circle with the radius a1 about the center 1 leading thereafter directly into the horizontal direction, the deformation for straightening would have been four times larger than the four individual deformations at the points b, c, d and e.

In the examples set out below there are shown the correlation between the thickness of billet, radius of curvature, deformation of the billet and height of the plant. Reference is had to Table 1 below and item I of FIG. 2.

EXAMPLE I Item I demonstrates the path of a billet O-ab-cd-e-f, from right to left with a radius R of 3.00 m. as set out in the radius scale shown leftmost in FIG. 2, calibrated in meters. The increasing radii of the arcs a-b, b-c, c-d and d-e in accordance with Table 1 are 3.75, 5.00, 7.50, and 15.00 m., respectively. As the difference y in length of the outer fiber of the billet at the inner side of the arc relative to the neutral fiber which is assumed to coincide with the axis of the billet in the segment O-a amounts to 5%, at a-b to 4%, at b-c to 3%, at c-d to 2%, at d-e to 1%, and at the subsequent straight line ef amounts to 0%, there occur where the billet proceeds through. the path I from O- at each of the points a, b, c, d and 2 only small individual partial deformations of the magnitude Ay=l%.

It will be noted that, depending on the circumstances, higher partial deformations up to about 4% may be selected. The angles x of the circular arcs may be gleaned from Table 1. The sum of all the angles x amounts to when the billet has been deflected from the vertical head 0 to the horizontal foot e.

If the length of the arcuate portions between a and e are selected at a length of only .4 m., which in this example is twice the normal distance of about 200 mm. between pairs of deflector rolls in the cage, and if the initial arc O-a in accordance with its angle x of 74.7" would have a length of about 3.9 m., then the length of the path for the billet between 0 and e amounts to merely 5.5 m. and the difference in height between the top of the mold and the horizontal section of the path, as defined by the transport rolls is approximately only 3.00 in.

EXAMPLE II Another example is shown in item II of FIG. 2, reference being had to Table 2. It illustrates the modification where a straight mold (instead of an arcuate mold) is being used. In this modification the same method may be used for bending the billet through small increments or partial deformations in each of a series of steps, though at first the series is reversed in order to bring the billet stepwise onto a curvature of only 3.00 m.; thereafter, with the use of a continuous curved .path of the aforesaid type the deflection to the horizontal is completed.

In order to avoid damage of the initially thin outer skin of the billet in the mold by upwardly directed reaction forces when the billet proceeds in the curved stretch e'a, the example item II provides, for the sake of safety, for a straight stretch O'-e of about 2.00 m. in which there occurs no deforming.

It is, of course, possible to put instead the deformation stretch ea' immediately below the mold.

In this example the distance between the upper edge of the mold and the horizontal section e] of the path amounts to about 6.00 m.; and the partially solidified billet at each step is again deformed only for the small increment of 1%. This distance is still for about 2.00 m. smaller than a conventional peripheral path that extends throughout one-fourth of the periphery of an entire circle, shOWn in item III of FIG. 2 which illustrates a prior art device. The length of arc of that prior art path has been chosen in accordance with the greatest length of sump and where at the point a" there occurs the deflection from the peripherally curved portion of the path into the straight portion of the path at a deformation of 1.9% with the billet entirely solidified.

At certain widths of billet, which may be entirely solidified within the Zone of straightening, the prior art has taught that straightening may also be carried out in a single step. This prior art device is shown in item IV of FIG. 2. The difference in height between that prior art device, where the bending as well as the straightening occurs with the billet completely in solidified state at a deformation of about 2.5% at the points a', and the casting machines items I and II of FIG. 2 is strikingly large. The height of machine plants in accordance with the invention amounts to from about one-sixth to about onethird of comparable installations of the prior art.

The invention furthermore proposes to deform with rolls for bending or straightening, which rolls are not driven, so that the billet essentially will be drawn through the deflector mechanism, such as an adjustable deflector cage or the like; the main pull will be executed by the transport rolls although the deforming rolls may also be energized for aiding in an auxiliary manner the driving pull of the transport rolls.

It is, however, possible to transfer, instead, the entire driving pull from the transport rolls to the deforming rolls.

TABLE 1.(FIG. 2, ITEM I) NUMERICAL EXAMPLE FOR WIDTH or DIAMETER or 300 MM.

1 Deviati0n of length of the deformation fiber from the neutral fiber of the billet in percent.

AyDeformation of the billet at the transition points between the areuate portions, in percent.

Rye-Radius (neutral fiber) oi the individual arcuate port1onscircular segments, in meters.

:tAngle of the individual arcuate portions in degrees.

B-Rectified length of the individual arcuate portions in meters.

TABLE 2.(FIG. 2, ITEM II) y, percent Ay,pereent RN, m. 1', deg. B,

0e 0 0.00 2.0 ed' 1 1 15.00 1. 53 0. 4 -c 2 i v 7. 50 3.06 0. 4 cb 3 5. 00 4. 59 0. 4 ba 4 1 3. 75 6.12 0. 4 aa 5 l 3. 00 59. 40 3. 1 a-b 4 i 3. 75 6. l2 0. 4 b-c 3 5.00 4. 59 0. 4 ed 2 i 7. 50 3.06 0.4 d-e 1 15.00 1. 53 0. 4

Sum 90. 00 8. 3

NUMERICAL EXAMPLE FOR WIDTH or DIAMETER or 300 MM.

1 Deviation of length of the deformation fiber from the neutral fiber of the billet in percent.

Ag De[ormation of the billet at the transition points between the arcuate portions, in percent.

R.-rRadius (neutral fiber) of the individual arcuate portions circular segments, in meters.

x-Angle of the individual arcuate portions in degrees.

BRectified length of the individual arcuate portions in meters.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

Having thus described the invention, what 'we claim as new and desire to be secured by Letters Patent, is as follows:

1. A method of continuously casting metal bars in an open-ended, relatively highly curved mold, the bar leaving the mold being shifted into the horizontal along a curved path, said method comprising deforming the bar in a series of continuous steps commencing with the relatively high curvature of the mold, the amount of curvature being decreased in the following steps and the degree of straightening of any step being below any amount that may be damaging to the bar.

2. In a method, as claimed in claim 1, the degree of deformation varying among the steps.

3. In a continuous casting machine, the combination of a continuous open-ended relatively highly curved casting mold operable for discharging downwardly and sidewardly a partially solidified continuous metal billet, said billet solidifying completely at a distance from said mold, and means connected with relation to said mold and operable for deforming the descending billet in a series of continuous steps deflecting it in said sideward direction towards the horizontal and defining a continuous path for said billet, said path commencing with the curvature of the mold and including a series of successive arcuate portions interconnected in continuous transition, each arcuate portion being formed along a circular arc described by a radius, the radii of the succeeding arcuate portions differing from each other increasing proportionally successively with increasing distance of the path from the mold, whereby the amount of curvature is decreased in the successive steps after the billet leaves the mold and the billet is being straightened gradually, said radii being so dimensioned that the degree of straightening of any step being below any amount that may be damaging -to the billet.

(References on following page) 7 References Cited UNITED STATES PATENTS 1/1955 Tarquinee et a1.

8/ 1960 Schneckenburger et a1.

FOREIGN PATENTS 2/ 1963 France. 2/1963 France.

8 929,335 6/ 1963 Great Britain. 941,290 11/1963 Great Britain.

I. SPENCER OVERHOLSER, Primlary Examiner.

R. A. SANDLER, R. S. ANNEAR, Assistant Examiners.

Claims (1)

1. A METHOD OF CONTINUOUSLY CASTING METAL BARS IN AN OPEN-ENDED, RELATIVELY HIGHLY CURVED MOLD, THE BAR LEAVING THE MOLD BEING SHIFTED INTO THE HORIZONTAL ALONG A CURVED PATH, SAID METHOD COMPRISING DEFORMING THE BAR IN A SERIES OF CONTINUOUS STEPS COMMENCING WITH THE RELATIVELY HIGH

Images