DE102005023745B4 - Process for producing a continuous casting mold and continuous casting mold - Google Patents

Abstract

Method for producing a continuous casting mold (1), in which at least one surface (2) is mechanically processed which, when the mold is used as intended, comes into contact with molten material, characterized in that in the last work step in the production of the surface (2) the Mechanical processing is carried out on the mold (1), which produces an anisotropically structured surface such that the surface (2) of the mold (1) has a greater roughness in the casting direction (G) than in the direction (Q) transverse to the casting direction (G ) and linearly designed and oriented elevations and depressions, which run in direction (Q) transverse to the casting direction (G) and are designed as waves, the crests and troughs of which run in direction (Q) transverse to the casting direction (G), the the The height (H) of the waves is between 2 µm and 250 µm and the last step is a milling process.

Description

The invention relates to a method for producing a continuous casting mold, in which at least one surface is mechanically processed which has contact with molten material when the mold is used as intended. Furthermore, the invention relates to a continuous casting mold.

Continuous casting molds are known which are characterized by a special surface design in order in particular to influence the heat transfer from the steel into the mold wall in a favorable manner.

the EP 1 099 496 A1 provides for mold plates to be given a surface texture in whole or in part in order to reduce the flow of heat. The texture is preferably produced by sand or shot blasting after the mechanical processing. As a result, the roughness of that surface of the mold which has contact with molten material when the continuous casting mold is used as intended can be increased.

In the JP 10 193 042 A describes a continuous casting mold in which longitudinal grooves are specifically introduced into the surface of the broadside plates. This is to ensure that the heat flow density in the meniscus is reduced in order to avoid longitudinal cracks.

From the JP 02 020 645 A a continuous casting mold emerges in which longitudinal grooves and transverse grooves are introduced into the broadside plates in a predetermined grid. This also aims to reduce the heat flow density in the meniscus and thus reduce the risk of longitudinal cracks. The introduced grooves are in the range of 0.5 to 1.0 mm; the grid spacing is approx. 5 to 10 mm.

From the AT 269 392 a continuous casting mold is known in which a reduction in the heat flow density is also sought, namely in the upper area of the mold. This is achieved by increasing the wall thickness of the mold in its upper area or by using more insulating material in this area. The mold can either consist entirely of this material in its upper area or be coated with this material on the water side.

the FR 2 658 440 describes a continuous casting mold in which a local reduction in the heat flow density is achieved in that grooves are introduced into the hot side of the mold and these grooves are filled with a second material with low thermal conductivity. In addition, the entire surface of the mold is coated with this second material.

In the JP 06 134 553 A and in the JP 03 128 149 A describes the roughening of the surface of casting rolls, which is intended to reduce the heat flow density in this application.

Other solutions reveal the DE 102 56 751 A1 , the DE 42 41 775 A1 , the DE 28 56 472 C2 , the JP H07 - 178 526 A , the DE 40 38 986 A1 and the DE 100 03 827 A1 .

With the previously known measures, an improved thermodynamic behavior of the mold and in particular its walls as well as an improved usability in continuous casting are to be achieved. In general, a good adhesion of the casting powder to the mold plate and an even distribution of the heat flow over the entire mold is aimed at.

The thickness and the structure of the casting powder layer between the mold wall and the strand shell largely determines the amount of heat flow density between the steel and the mold and thus the thermal load on both the strand shell and the mold material. Local and temporal changes in the mold powder layer, especially in the area of the meniscus, can therefore result in strong stresses in the strand shell, which lead to longitudinal cracks, especially in steel grades that are susceptible to cracking. However, the surface of the mold is also exposed to strong mechanical loads due to alternating thermal stresses. Therefore, the maximum heat flow in the area of the meniscus should be low and as uniform as possible in order to reduce the risk of crack formation, especially in steel grades that are sensitive to longitudinal cracks.

In addition, the aim is for the friction between the broad sides and the narrow sides of the mold to be as low as possible during the adjustment of the narrow sides. Finally, the aim is to reduce the thermal load in the meniscus by means of a low heat flow density, which should have a positive effect on the service life of the mould.

The proposed measures achieve this goal only partially or with a relatively high production cost.

The invention is therefore based on the object of creating a method for producing a continuous casting mold and a continuous casting mold with which or with which the mentioned are desired properties are achieved as well as possible, and this should be achieved with the least possible manufacturing effort and thus at low cost.

The solution to this problem by the invention is characterized in that the last step in the production of the surface of the mold is mechanical processing, which produces an anisotropically structured surface such that the surface of the mold has a greater roughness in the direction of casting than in the direction transverse to the casting direction and line-shaped and oriented elevations and depressions, which run in the direction transverse to the casting direction and are designed as waves, the crests and troughs of which run in the direction transverse to the casting direction, the height of the waves being between 2 µm and 250 µm and the last step is a milling process.

Anisotropy means that surface characteristics change depending on the surface direction in which they are determined. In the case of the surface of the mold in question, this means in particular that parameters such as B. Roughness measured in the casting direction have different values than perpendicular to it, d. H. in the transverse direction to the pouring direction.

The continuous casting mold, which has at least one mechanically processed surface which, when used as intended, comes into contact with molten material, is characterized according to the invention in that the surface at least partially has an anisotropic structure such that the surface of the mold has greater roughness in the casting direction than in the direction transverse to the casting direction, with the surface having linearly formed and oriented elevations and depressions that run in the direction transverse to the casting direction and are formed as waves, the crests and troughs of which run in the direction transverse to the casting direction and the height of the waves between 2 µm and 250 µm.

In this case, the corrugations preferably have a substantially rounded shape in cross section. It has proven itself when the height of the waves is between 10 µm and 50 µm.

The height of the waves on the surface can remain constant in the pouring direction and/or transversely to the pouring direction or can be adjusted variably.

The proposal of the invention is therefore based on the fact that the desired anisotropic surface structure is produced in the last step of the shaping, mechanical processing of the mold surface. The machined surface can advantageously be designed in such a way that a different macroscopic structure is produced in the casting direction than transversely to the casting direction. Equally, the microscopic roughness of the surface in the casting direction and transverse to it can also be different.

Greater roughness in the casting direction and a macroscopic structure of the surface with lines of elevations running transversely to the casting direction ensure that the mold powder layer adheres better to the mold plate, especially in the area of the meniscus, and is not easily rubbed off the strand - completely or only locally. At the same time, both the increased roughness and the macroscopic structure of the surface lead to a reduction and smoothing of the heat flow, which also leads to a reduction in the tendency for longitudinal cracks. By reducing the heat flow density in the meniscus, the thermal load on the mold plate is also reduced, which results in a longer service life of the mold plates.

It is also advantageous that the desired surface structure is created during the mechanical, chip-removing processing of the mold surface. This means that further processing steps, such as B. the introduction of grooves in the surface, the coating of the surface in the meniscus area or the roughening of the surface by sand or shot blasting, are not required, which makes the proposed invention economical. In this way, the advantageous anisotropic surface structure can be produced without great effort not only during manufacture of the molds, but also whenever the mold surface is reworked, which has to be done at certain time intervals.

Due to the design of the mold surfaces in the manner described with macroscopic elevations oriented transversely to the casting direction or through a roughness that is greater in the casting direction than transversely to it, in the case of molds that consist of individual mold plates (e.g. slabs, thin slabs) in addition, the friction between the wide and narrow sides is reduced when the narrow side is adjusted.

In the drawing an embodiment of the invention is shown.

• 1 schematisch eine Kokillenplatte mit anisotroper Oberfläche sowie die Oberflächentopologie in vergrößerter Darstellung,
• 2 schematisch das Profil der Oberfläche der Kokillenplatte in dreidimensionaler Darstellung und
• 3 den vergrößert dargestellten Schnitt A-B gemäß 1.

Show it:

• 1 schematic of a mold plate with an anisotropic surface and the surface topology in an enlarged view,
• 2 schematically the profile of the surface of the mold plate in three-dimensional representation and
• 3 according to the section AB shown enlarged 1 .

In 1 is the view of that surface of a mold plate of a continuous casting mold 1 that has contact with molten material (steel) or the solidified strand shell when the continuous casting mold 1 is in use. The strand shell passes the mold plate in casting direction G. In order to achieve the advantages explained above, surface 2 has a special structure: The surface topology, in particular the roughness, of surface 2 is anisotropic, i.e. in casting direction G and different roughness values in direction Q perpendicular to the casting direction G.

The mold plate is provided with a large number of elevations and depressions, which 1 are shown only very schematically. The production of these elevations and depressions takes place during the last mechanical machining process in the manufacture of the mold plate. The surface of the mold plate is milled in the last processing step using the line milling process. For this z. B. used a milling tool with a diameter of 100 to 150 mm, with conventional indexable inserts such. B. made of hard metal is provided. The material removal during the last processing step is less than 1 mm, preferably less than 0.5 mm. The characteristics and structure of the elevations and depressions on the mold surface can be specifically adjusted according to the selected removal and the other milling parameters such as rotational speed, feed rate, cutting speed, distance between the milled lines, coolant, milling direction and the angle of the tool to the plate surface (camber).

Alternatively, the desired surface structure can also be produced using a grinding process. Similar to milling, the surface can be sanded in rows for this purpose. The shape of the wave-like elevations and depressions can be generated by the surface contour of the grinding wheel or by the angle of the grinding wheel to the plate surface.

2 shows the profile of the finished surface in three-dimensional view. Here it can be seen that the roughness of the surface is greater in the casting direction G than across the casting direction Q. The mold plate is therefore provided with a large number of elevations and depressions, which 1 are shown only very schematically. The production of these elevations and depressions takes place during the last mechanical processing operation in the manufacture of the mold plate.

The height H of the linearly oriented elevations and depressions is in 3 can be seen and is typically in the range of 2 µm to 250 µm, which can be influenced by the choice of the milling parameters.

reference list

1

continuous casting mould

2

surface

3

wave structure

G

pouring direction

Q

Direction transverse to the pouring direction

H

height of the waves

Claims (6)

A method for producing a continuous casting mold (1), in which at least one surface (2) is mechanically processed which, when the mold is used as intended, comes into contact with molten material, characterized in that in the last work step in the production of the surface (2) the Mechanical processing is carried out on the mold (1), which produces an anisotropically structured surface such that the surface (2) of the mold (1) has a greater roughness in the casting direction (G) than in the direction (Q) transverse to the casting direction (G ) and linearly designed and oriented elevations and depressions, which run in direction (Q) transverse to the casting direction (G) and are designed as waves, the crests and troughs of which run in direction (Q) transverse to the casting direction (G), the the The height (H) of the waves is between 2 µm and 250 µm and the last step is a milling process. Continuous casting mold (1) which has at least one mechanically processed surface (2) which, when used as intended, comes into contact with molten material, produced using the method according to claim 1 , characterized in that the surface (2) at least partially has an anisotropic structure such that the surface (2) of the mold (1) has a greater roughness in the casting direction (G) than in the direction (Q) transverse to the casting direction (G ), wherein the surface (2) has line-shaped and oriented elevations and depressions, which run in direction (Q) transverse to the casting direction (G) and are designed as waves, the crests and troughs of which extend in direction (Q) transverse to the casting direction (G ) and the height (H) of the waves is between 2 µm and 250 µm. continuous casting mold claim 2 , characterized in that the corrugations have a substantially rounded shape in cross-section. continuous casting mold claim 2 or 3 , characterized in that the height (H) of the waves is between 10 µm and 50 µm. Continuous casting mold according to one of claims 2 until 4 , characterized in that the height (H) of the waves is constant in the casting direction (G). Continuous casting mold according to one of claims 2 until 4 , characterized in that the height (H) of the waves is variable in the casting direction (G).

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