CN1978091B - Tubular crystallizer for continuous casting metal - Google Patents

Abstract

The invention relates to a tube mold for a continuous casting metal, wherein at least one partial region of the outer surface (3) of the tube mold is provided with a cooling channel, and wherein the depth and the width of the cooling channel are greatest in the middle of a sidewall of the tube mold (1), and becomes less in the direction of corner regions (4) of the sidewall. Thereby, uniform heat dispersion may be achieved and higher casting speed is possible with said heat dispersing. A ratio of a channel center distance and the width of the cooling channel is within a range of 1.2 to 3. The cooling channel has a depth of 3 mm-8 mm, under the condition that a residual wall thickness should not fall below 6 mm in the cooling channel region. A number of 4-10 cooling channels per 100 mm are provided on side surface of the tube mold tube.

Description

Tubular molds for continuous casting of metals

technical field

The invention relates to a tubular mold for continuous casting of metal.

Background technique

Tubular molds made of copper or copper alloys for casting profiles of steel or other metals with a high melting point are known in many ways from the prior art. Tubular molds generally have a uniform wall thickness in a horizontal cross-section, which increases in the direction of continuous casting due to the internal taper of the tubular mold. This internal taper is adapted to the solidification behavior of the strand and the casting parameters. Shortly after the start of solidification of the continuously cast material, ie directly below the casting liquid level, due to the three-dimensionally manifested heat dissipation in the cross section, a strongly differently manifested cooling behavior of the cast strand occurs. Since a particularly large amount of heat is dissipated at the corners of the tubular mold due to geometrical relations, a particularly strong thickening of the strand shell and thus a particularly strong shrinkage occurs there. The heat dissipation on the side walls of the tubular crystallizer is usually not great, although at the same time a relatively high heat flow occurs. The result of the locally different cooling is an inhomogeneous strand shell thickening, which can lead to material stresses and cracks in the strand shell and thus increases the risk of the strand breaking.

A series of proposals have already been made in order to achieve the greatest possible uniform heat dissipation and thus also the prerequisite for a high casting efficiency. For example, a mold is known from DE 36 21 073 A1, in which only the curved sides and not the corner regions are provided with cooling grooves. First of all, the cooling should be increased in the region of the pouring level, as is also described in DE 34 11 359 A1. EP 1 468 760 B1 also deals with the improvement of cooling efficiency and the increase of casting speed, which document proposes that 65% to 95% of the cooling channels of the outer surface of the copper tube are loaded, wherein the copper tube is simultaneously on the entire periphery and basically on the entire A protective jacket is set on the length. In vertically vibrating continuous casting molds DE 195 81 547 C2 recommends the provision of depressions or dips on the inner surface which are arranged at a distance of 15 mm to 200 mm below the casting level measured in steady state operation. Stable casting should therefore also be allowed at higher speeds. All these documents do not sufficiently consider the actual heat flow distribution.

Contents of the invention

Proceeding from the prior art, the object of the present invention is to provide a tubular mold with which the uniformity of the strand cooling is further increased in order to achieve a higher casting efficiency and better strand quality as a result And thus the mold helps to reduce the stress in the mold walls.

The invention realizes a tubular mold for continuous casting of metal, wherein at least a partial area of the outer surface of the tubular mold is provided with cooling grooves, the depth and width of which are in the middle of the side walls of the tubular mold is the largest and decreases towards the corner region of the side walls, the ratio of the groove center distance to the width of the cooling groove is in the range of 1.2 to 3, with a residual wall thickness not less than 6 mm in the region of the cooling groove , the cooling grooves have a depth of 3 mm to 8 mm, and 4 to 10 cooling grooves are arranged on each 100 mm side surface of the tubular crystallizer.

In the case of the mold according to the invention it is essential that the cooling effect of the mold is optimized such that it corresponds to the heat supply of the continuous cast strand, in order thus to achieve uniform cooling. This is achieved in that the depth and/or width of the cooling channels is greatest in the middle of the side walls of the mold and decreases towards the corner regions of the side walls. It is decisive that the cross-sectional area of the cooling groove is greater in the central region of the side wall than in the edge region of the side wall. It has been shown that the maximum equivalent stresses occurring at the side walls can be significantly reduced by providing cooling grooves in the manner according to the invention. Ideal elastic strength calculations have confirmed that the equivalent stress can be reduced by more than 30% from 504MPa to 348MPa. The data relate to a mold cross-section of 130×130 mm, in which a tubular mold without grooves is compared with a tubular mold with grooves designed according to the invention. The reduction of the stresses in the mold tube achieved in this way has an advantageous effect on the lifetime and reduces the thermally induced deflection of the mold tube. In this calculation, the tubular mold according to the invention has eight grooves on each side wall with a distance of 5 mm and an extension length of 200 mm in the casting direction. The central groove has a depth of 5 mm, whereas the outer grooves have a depth of 4 mm at a width of 12 mm or 8 mm. No grooves are provided in the corner regions of the side walls.

For the specific design of the cooling channel with regard to its depth and width, it is decisive that the cooling channel geometry corresponds as well as possible to the heat flow emerging from the inside and thus a temperature field that is as uniform as possible can be achieved, which until now has not been satisfactory. satisfy. It is important that the cooling grooves are deeper and/or wider, ie have a larger cross-section, in the middle of the side walls where the heat supply is highest than in the vicinity of the corner radii.

Preferably, within a distance of 10 mm to 15 mm of the radius corner region, no cooling grooves are provided on the side walls, so that cooling is not increased here and the rigidity of the mold does not have to be reduced. Better results are achieved when the cooling grooves have a depth of 3 mm to 6 mm. At this time, the residual wall thickness between the deepest part of the cooling tank and the inner side of the tubular crystallizer should not be less than 6mm.

The width of the cooling groove can preferably be selected between 5 mm and 20 mm.

In order to adapt the number of cooling channels to the different sizes/formats of the tube mold, it has proven to be advantageous to have 4 to 10 cooling channels per 100 mm of side surface of the tube mold for the designed channel size.

A cooling channel width/depth ratio of between 1 and 4 is considered to be particularly advantageous for flow technology. A ratio different from this has a disadvantageous effect on the flow conditions and thus on the cooling efficiency and rigidity of the tubular mold in the region of the liquid level. The cooling groove preferably has a smaller transition radius at the groove bottom to the groove wall in order to avoid stress concentrations there.

The cooling groove ideally has a radius in the region of the inlet and the region of the outlet, which helps to optimize the flow of the cooling water and to reduce pressure losses.

In one considered advantageous arrangement of the cooling grooves, their relative distance, measured from the center of the groove, is between 10 mm and 25 mm. A ratio of between 1.2 and 3 of the groove center distance to the width of the cooling groove provides surprisingly good results.

In principle, it is desired that the width of the cooling groove is greater in the direction of the middle of the side walls and thus the depth also increase in the direction of the middle. Different cooling channel geometries can be produced by cutting the mold or also by machining without cutting in the shaping of the mold.

It is advantageous if the cooling channel is arranged in an area starting at 50 mm above the set point of the pouring level and extending to about 300 mm below the set point of the pouring level, because a greater heat flux occurs in this area and thus in the The stresses are also greatest in the sidewalls of the crystallizer. Although the deeper regions in the casting direction, i.e. the region at a distance greater than 300 mm below the nominal position of the pouring liquid level, must be cooled in the same way, since the temperature uniformity of the already formed continuous casting strand shell is not greater than that of the trough formed according to the invention, it must be in these The following areas are required. Outstanding results are obtained if the groove according to the invention starts approximately 50 mm above the set point of the pouring liquid level and extends to 300 mm below the set point of the pouring liquid level.

Description of drawings

The invention is explained in more detail below on the basis of the exemplary embodiments depicted in the drawings.

Figures 1a and 1b show a tubular crystallizer in a perspective view and an enlarged perspective view.

Detailed ways

FIGS. 1 a and 1 b show a perspective view and an enlarged perspective view of a tubular crystallizer 1 , which is positioned in a tank in a manner not described in detail. Special features in this tubular crystallizer 1 are specially designed cooling channels 2 , which are formed on the outer surface 3 of the tubular crystallizer 1 . The cooling channels 2 do not extend over the entire length of the tubular crystallizer 1 , but are only present in the region of the upper injection side of the tubular crystallizer 1 . In this embodiment, the length of the cooling groove 2 is 200mm. The cooling trough 2 is present in the region of the set point of the fill level, the set point of the fill level being in the upper quarter of the cooling trough 2 described. The peculiarity in the cooling channels 2 of the tubular mold is that they are not all of the same width and depth, but are different in width and depth. In the present exemplary embodiment, the outer cooling grooves 2 a and 2 b near the corner regions 4 are narrower than the cooling grooves 2 c on the corresponding side walls in the central region. The central cooling groove 2 c has, for example, a width of 12 mm, while the four outer cooling grooves 2 a and 2 b may have, for example, a width of 8 mm. All cooling channels 2a, 2b, 2c have the same length. However, not only the width of the cooling grooves 2a, 2b, 2c is changed, but also their depth. This follows from the fact that the cooling grooves 2 a , 2 b , 2 c have a radius 5 in the inlet and outlet regions, ie in each case at the end faces. The transition from the radius 5 to the deepest part of the respective cooling groove 2a, 2b, 2c is visible by a horizontal line. In the middle cooling channel 2c the depth is seen to be greatest. The cooling grooves 2b adjacent to the outside have a slightly smaller depth. The depth is smallest in the outer cooling grooves 2 c near the corner regions 4 .

No cooling channels are provided in the corner area 4 . The tubular crystallizer is fixed to a water guide plate not described in detail in the water tank, so that the cooling water is pressed into each cooling channel 2a, 2b, 2c. The water deflectors are arranged in such a way that the tubular crystallizer is held in the middle of the water gap.

Claims (8)

1. A tubular crystallizer for continuous casting metal, wherein at least a partial area of the outer surface (3) of the tubular crystallizer is provided with a cooling groove, it is characterized in that: the depth and width of the cooling groove are within the range of the tubular crystallizer The middle of the side wall of the device (1) is the largest and decreases towards the corner area of the side wall, the ratio of the groove center distance to the width of the cooling groove is in the range of 1.2 to 3, in the area of the cooling groove When the residual wall thickness is not less than 6mm, the cooling grooves have a depth of 3mm to 8mm, and 4 to 10 cooling grooves are arranged on every 100mm side surface of the tubular crystallizer. 2. The tubular mold as claimed in claim 1, characterized in that no cooling grooves are provided on the side walls within a distance of 10 mm to 15 mm of the radius of the corner region (4). 3. The tubular crystallizer according to claim 1 or 2, characterized in that the distance between the centers of the two cooling tanks is in the range of 10 mm to 25 mm. 4. The tubular mold as claimed in claim 1, characterized in that the ratio between the width and the depth of the cooling channels is in the range of 1 to 4. 5. The tubular crystallizer as claimed in claim 1, characterized in that the cooling channels have a width in the range of 5 mm to 20 mm. 6. The tubular mold as claimed in claim 1, characterized in that the cooling channel is arranged in a region starting at 50 mm above the set point of the filling level and extending to 300 mm below the set point of the filling level. 7. The tubular crystallizer according to claim 1, characterized in that the cooling tank is provided with a transition radius at the tank bottom to the tank wall. 8. The tubular crystallizer as claimed in claim 1, characterized in that the cooling channels have a radius (5) in their inlet and outlet regions.

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