JPS5827019B2 - Continuous casting method and continuous casting machine for metal strands - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides continuous casting of shrinkage stress sensitive metals, particularly steel, into metal strands in a strand mold having a plurality of mold walls that move with the casting strand. It relates to a method for casting said metal and to a machine for carrying out this method.

According to the long-known continuous casting method for metal strands, a mold wall body formed, for example, by two metal strips with partition walls on the sides or a casting wheel having a coating of metal strips, is used together with the metal strands. By moving the mold wall, a strand is formed in a predetermined continuous casting cross section.

In the latter case, a groove provided around the casting wheel forms part of the strand mold, while a metal band covering this groove and rotating forms the remainder of the strand mold.

The above methods are particularly widespread in the production of copper and aluminum strands.

In this case, it is common practice to lubricate, i.e. add substances such as oil or soot to prevent the molten metal from sticking to the mold walls.

However, the extremely long contact times between the strands being cast and the mold walls moving with the cast strands result in undesirable conditions for longitudinal shrinkage of the strands. , when shrinkage occurs in areas of high friction that are in extensive mutual contact, the shrinkage stress exceeds the permissible elastic elongation of the solidified or solidifying cast strand shell, to the extent that transverse cracking occurs in the material. Stresses along the length of the strands may increase.

Usually such a phenomenon is practically absent in the case of copper and aluminum, but it is observed in materials for which the above-mentioned method has hitherto been mainly employed.

For example, this phenomenon occurs strongly in materials that are sensitive to elongation, such as metals with lower toughness than copper.

This phenomenon is particularly observed in alloys and steels that have a strong tendency to form dendrite or columnar crystal structures.

The problem of the present invention is to solve the problem in the method described in the opening part.
The object of the present invention is to prevent in a simple manner the occurrence of longitudinal stresses in the strands to an unacceptable degree and the consequent occurrence of defects in the cast strands, in particular transverse cracks in the metal strands.

It is also an object of the invention to provide a machine suitable for carrying out the method described above.

The method according to the invention provides for cooling a metal strand while it is being transported longitudinally through a strand mold, at a number of locations on the surface of at least one of a plurality of moving mold walls. The strands are hooked (f
ormschlussig) and the spacing of these holding locations is less than a value at which unacceptable shrinkage stresses occur in the metal strand during cooling.

A continuous casting machine according to the present invention is a continuous casting machine having a strand mold in which a mold wall moves together with a casting strand, in which at least one of the moving wall type walls has a recess and/or a convex part. , characterized in that its spacing in the direction of movement of the mold walls is determined below a value at which unacceptably high shrinkage stresses appear in the metal strands during cooling.

Embodiments of the invention include the following.

According to one embodiment, the spacing of the holding locations may be less than a value at which cracking occurs as a result of unacceptable shrinkage stresses.

According to other embodiments, lubricants can be used to reduce friction between the holding locations.

According to another embodiment, the metal strand can also be held in a hook-like manner by means of straight depressions and/or protrusions extending transversely to the axis of the metal strand.

According to a further embodiment, it is possible to hold the metal strand in place by means of locally distributed depressions and/or protrusions.

The concave part or the convex part has a spherical cross-section shape, a conical cross-section shape, a truncated conical shape,
Preferably, it is grooved or rib-shaped.

At least one mold wall has a continuous stamped recess and/or
Alternatively, it is preferable that the protrusion is a metal covering in the central region of the covering band.

In addition, it is preferable that the central part of the covering body is wavy.

The principle of the invention is to fix the strand adjacent to the mold wall during longitudinal contraction during cooling;
The spacing between these fixing points is selected to be small so that unacceptable elongation and resulting cracking between these fixing points does not occur.

In this way, the longitudinal stresses are evenly distributed over a large length of the strand, thereby avoiding unacceptably high local stresses.

To realize such a mold fixing place or holding place,
It is sufficient to provide some kind of surface shape that is a modification of the smooth surface shape of the strand mold at more than one location on the mold wall.

Therefore, in the case of a casting wheel covered with a metal band, such an irregular surface shape can be provided either on the conical side wall of the inner cylindrical mold wall or on the covering wall. can.

In the case of a strip caster, it can be provided on both sides of the opposing strips or on the side forming walls.

In this case, the irregular surface shape can be realized in the form of wavy grooves, teeth, local depressions and protrusions, etc.

As long as the irregular surface shape is provided on the band side of the strand mold, the band can be manufactured by appropriately pressing the band.

If a surface irregularity is to be achieved by means of a covering band on the casting ring, the strand can be improved by restricting the position of this surface irregularity in the area of the casting cavity so that it does not lie at the extreme ends, viewed transversely to the strand. Care should be taken to seal the mold.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 conceptually shows a side view of a casting machine with a clockwise pivotable casting wheel 1, which is provided with a groove 2 on its periphery.

The casting machine is covered with a steel sheathing band 4 in the peripheral region of the casting wheel indicated by angle 3, so that in this peripheral region a strand mold 5 is formed by a moving mold wall.

The coating strip 4 is guided by deflection and tensioning rolls 6 and is pressed onto the outside of the casting wheel 1.

The necessary cooling is effected in a known manner on the inside and outside of the casting wheel by means of fountain nozzles (not shown).

The molten metal is continuously fed from the pouring tank 7 via the pouring nozzle 8 to the pouring end of the strand mold 5, cooled in the cooperating mold walls, solidified and poured into the strand mold 5 as a solidified metal strand 10. Leave the exit end.

When steel strands are cast using known casting machines of the type described above, transverse cracking can occur in the strands due to unacceptably high shrinkage stresses in the steel due to casting and cooling rates.

In order to avoid this drawback, in the casting machine according to the invention, at least one of the possible walls has a convexity or a concavity, which allows the solidified strand to adjust the relative position between the strand and the corresponding mold wall. It remains fixed in place until it leaves the outlet end 11 of the mold 5.

The distance between fixing locations of such a strand in the direction of mold wall movement, that is to say in the circumferential direction of the casting wheel in the case currently being described, is determined by the permissible longitudinal stress in the strand.

FIG. 2 is an enlarged scale cross-sectional view taken along the line ■-■ in FIG. There is.

That is, the cylindrical inner wall 12 of the strand mold, that is, the inner wall of the strand mold 5, has a local recess 13, and the side wall 12 of the strand mold 5, that is, the casting wheel 1.
There is a wedge-shaped projection 14 in the groove 2 around the covering band 4
There are locally convex portions 15 on the cylindrical outer wall of the strand mold.

The concave portions or convex portions are arranged in the circumferential direction of the casting wheel so as to satisfy the above requirements.

The allowable spacing can be determined by experiment.

To determine the degree of non-flatness of the forming walls of the strand mold, the strands should not be able to deviate longitudinally with respect to the mold walls at a given location, but at the exit end 1 of the strand mold.
1 so that release of the strand from the circumferential groove 2 is not substantially difficult.

Therefore, a rounded shape is advantageous for convex and concave portions, and if it seems necessary to hold the strand on the side wall, the side wall should be designed with a non-contoured shape so as not to impede the movement of releasing the strand from the surrounding groove. A flat shape is advantageous.

In the conceptual diagram of the band casting machine shown in Fig. 3,
The strand mold is formed by two rotating steel strips 30, 31 and side partitions 32.

33 indicates a direction change/tension roll, and 34 indicates a support roll.

Liquid metal is supplied by a casting bath 35 to the inlet end 36 of the strand mold, whose mold walls move together with the cast strand and exit as solidified metal strand at the outlet end 3.
Leave 7.

In this case too, in order to eliminate the above-mentioned drawbacks when casting steel or similar materials, the mold walls are provided with recesses and/or projections.

Copper strip 30 or steel strip 31 or both are particularly suitable for this purpose.

Methods for retaining cast strands may be specific as described in the Examples below.

In the case of the casting wheel shown in side view and partial plan view respectively in FIGS. 4 and 5, local recesses 43 are provided which are distributed in the bottom surface 42 of the circumferential groove, corresponding to the embodiment according to FIG. ing.

In this case, the recess is embodied as a cross section of a sphere, but other recess shapes such as a truncated spherical shape, a truncated pyramid shape, a groove shape, etc. may be selected as long as the above requirements are met.

In this case, the requirements are that the strand is fixed in position relative to the mold wall in the direction of movement of the mold wall as long as the strand is in the area of the strand mold, and that the strand is substantially blocked at the exit end of the strand mold. This is a point of liberation.

5, the spacing between the fixed points 43 is indicated by 44.

This spacing must not exceed the above-mentioned dimensions, ie at most those which avoid unacceptably high longitudinal stresses when the strands solidify in the mold.

In the case of the casting wheel 61 shown in a side view and a partial plan view in FIGS. 6 and 7, respectively, local convex portions 63 are distributed on the bottom surface of the surrounding groove, and intervals in the direction of movement of the mold wall body are formed. 64 also satisfies the above requirements.

These local protrusions may also have a different shape from that shown and may therefore be embodied in the shape of a truncated sphere, a truncated pyramid, or the like.

In the embodiment of the casting machine of the present invention equipped with the covering band embodied in FIGS. 8 to 10, FIG. 9 shows an enlarged sectional view of FIG. - The X-ray cross section is shown in FIG. 10 and shows the wavy surface structure on the base surface 82 of the peripheral groove of the casting ring 81.

Therefore, the recesses 83 or the protrusions 8 constituting a wavy surface structure
The direction 4 intersects with the four circumferential directions of the casting ring within the inner cylindrical mold wall.

The covering strip 85 shown in FIGS. 9 and 10 is likewise corrugated, specifically in its central region 86 (see FIG. 10).

The maximum width of this central region 86 is determined by the width of the peripheral groove in the outer diameter region of the cast ring.

The reason for this is that the outer regions of the covering strips that follow on both sides of the central region 86 must be able to fit closely against the outer surface of the casting wheel.

In the case of such a non-flat shape, the release at the outlet end of the strand mold is particularly good.

The formation of corrugations by stamping in the central region of the covering strip 85 makes it possible to reduce the manufacturing costs of this strip.

FIG. 11 conceptually illustrates the shrinkage behavior within the strand during cooling and shrinkage when the strand is in the strand mold.

Note that the specific structure of the surface structure of the strand mold corresponds to that shown in FIGS. 8 to 10.

It should be noted that, for clarity, the size relationships are greatly distorted in the drawings.

The stresses developed in the strand 87 are shown at 88 to 91, and in the region between arrows 88 and 89 shrinkage creates longitudinal stresses in the strand 87, which are caused by adjusting the spacing between the support points appropriately. The selection is such that it is kept below acceptable limits.

[Brief explanation of drawings]

Figure 1 is a conceptual side view of a continuous casting machine with casting wheels;
Figure 2 is an enlarged view of the casting wheel taken along the line ■-■ in Figure 1;
The figure is a conceptual side view of a band casting machine, Figures 4 and 5 are side and partial plan views, respectively, of a casting wheel having dotted depressions on its cylindrical inner surface, and Figures 6 and 7 are its cylindrical inner surface. A side view and a partial cross-sectional view of a cast ring having point-shaped convex ridges,
Fig. 8 is a partial cross-sectional view of a casting wheel in which the bottom wall on the cylinder radial side exhibits a transversely wavy shape, and Fig. 9 is an enlarged view of the casting ring in Fig. 8, in which the central region is also formed in a wavy shape. 10 is a cross-sectional view taken along the line X-X of FIG. 9, and FIG. 11 is a concept explaining the stress situation occurring in the cast strand when the method according to the invention is used. It is a diagram. 10, 87... Metal strand, 5, 38...
...Strand mold, 2, 4, 30.31.
32,42゜62.82,85...mold wall,
13, 14, 15゜43.63, 83, 84...
・Fixing location, 83... recess, 84...
Convex part.

Claims (1)

[Claims] 1. When continuously casting metals sensitive to shrinkage capacity, especially steel, into metal strands, the metals are cast in a strand mold having a plurality of mold walls that move together with the casting strand. In the method of casting, cooling the metal strand while it is being transported longitudinally through a strand mold, the strand is cooled at a number of locations on the surface of at least one of a plurality of moving mold walls. a series of metal strands, characterized in that they are held in a hook-like manner, and the spacing between these holding locations is less than a value that causes unacceptable shrinkage stresses in the metal strand during cooling of the metal strand. Casting method. 2. A continuous casting method according to claim 1, characterized in that the spacing between the holding locations is less than a value at which cracking occurs as a result of unacceptable shrinkage stress. 3. The continuous casting method according to claim 1 or 2, characterized in that a lubricant is used to reduce friction between the holding locations. 4. Any one of claims 1 to 3, characterized in that the metal strand is held in a hook-like manner by a straight recess 83 and/or protrusion 84 extending across the axis of the metal strand. Continuous casting method according to item 1. 5. Any one of claims 1 to 4, characterized in that the metal strand is held in a hook-like manner by the locally distributed concave portions 13, 43 and/or convex portions 14, 15, 63. Continuous casting method according to item 1. 6. In a continuous casting machine having a strand mold in which the mold wall moves together with the casting strand, at least one of the moving wall mold walls has a recess and/or a convex part, and the mold wall moves in the direction of movement of the mold wall. Continuous casting machine for metal strands, characterized in that the spacing is determined below a value at which unacceptably high shrinkage stresses appear in the metal strand during cooling. 7. The continuous casting machine according to claim 6, wherein the recesses 83 and/or the protrusions 84 are arranged straight and across the direction of movement of the mold wall 82. 8 Localized recesses 13 distributed over the mold wall surface
, 43 and/or a convex portion 63, the continuous casting machine according to claim 6 or 7, characterized in that the continuous casting machine is provided with a convex portion 63. 9. The continuous casting machine according to claim 8, wherein the concave portion or the convex portion has a spherical cross-sectional shape, a conical cross-sectional shape, a truncated conical shape, a groove, or a rib shape. 10 At least one mold is in the central region 8 of the covering strip 85
10. The continuous casting machine according to any one of claims 6 to 9, wherein the continuous casting machine is a metal covering body having a concave portion and/or a convex portion stamped in a shape of 6. 11. The continuous casting machine according to claim 10, wherein the central portion of the covering band is wavy.