KR20090077925A - Continuous casting die with coolant channel - Google Patents

Abstract

The invention relates to a continuous casting die (1) with a coolant channel (2), which is formed by an inner wall of the die (3) as the hot side, the wall facing the molten metal, an outer wall of the die (4) as the cold side, and a right side wall (5) and a left side wall (6). The coolant channel (2) is provided with turbulence-creating elements (7, 9, 10).

Description

Continuous casting die with coolant channel {CONTINUOUS CASTING DIE WITH COOLANT CHANNEL}

The present invention relates to a continuous casting die comprising a die inner wall portion facing the molten metal on the high temperature side, a die outer wall portion on the low temperature side and coolant channels formed by right and left side wall portions.

The die wall portion of the continuous casting die is known from DE 198 26 522 A1. The die wall portion is comprised of a die inner plate and a reservoir container coupled with the die inner plate via a screw fastener, the die inner plate including webs on its side facing the reservoir container. In between, grooves in which a filling piece is disposed extend. The grooves here are used as cooling channels for cooling liquids, usually cooling water. The filling piece serves to reduce the channel cross section, thereby increasing the flow rate of the cooling liquid in the cooling channel.

DE 198 42 674 A1 discloses a similar filling piece.

In addition, continuous casting dies comprising cooling channels are known from the reference references DE 101 22 618 A1, DE 100 35 737 A1 and DE 101 38 988 C2.

From DE 102 53 735 A1 a die for continuous casting of molten metal, in particular steel, is known. The die includes cooling channels such as cooling grooves, cooling slits or cooling bores at contact surfaces located opposite the die hot side. The heat transfer of the die is characterized by the fact that the geometry of the heat transfer surface of the cooling channel or group of cooling channels is characterized by cross-sectional area, circumference, interface properties, orientation opposite to the contact surface, heat flow density of the contact surface during the casting operation, especially in the meniscus region. And / or by adjusting in the form of an arrangement and / or arrangement density opposite the contact surface for local formation of temperature.

In continuous casting, the liquid melt flows from the continuous casting tundish into a vibrating water cooled copper die through an immersion nozzle. Based on the heat removal amount, the melt temperature drops below the solidus temperature, thereby forming a strand shell oriented in the casting direction. As cooling increases, the thickness of the strand shells increases until the strands are completely solidified. Today, depending on the type and number of strands, casting speeds of 6 m / min or more are achieved. The size of the local heat flow density is typically up to 12 MW / qm.

The heat flow removed by the cooling medium depends in particular on the geometry of the coolant channel, the wall roughness and the flow rate, and thus the turbulence.

The higher the turbulence on the coolant side, the more concentrated the mixing and the more heat is removed. Although the heat transfer surface is enlarged, this expansion is limited to a small range. Especially when the heat flow density is very high, contamination occurs on the heat transfer surface by deposits, often called fouling. Since the deposit has a very low thermal conductivity, fouling raises the copper temperature very strongly in the case of die cooling, thereby reducing the useful life of the die.

Conventional continuous casting dies are formed with rectangular coolant channels, the coolant channels flowing through at a flow rate of about 10 m / s. Within these coolant channels, when the Reynolds number is about 250,000, a turbulent flow is formed in which the main flow component is axially oriented. Basic turbulence increases the mass, pulse and energy exchange between the individual coolant layers. Near the wall is formed a flow and temperature boundary layer, described by the so-called logarithmic wall law. The closer to the wall, the more turbulent the damping. The main disadvantage of the cooling according to the conventional approach lies in such turbulence, in which most components are oriented in the axial flow direction, and only relatively few components are oriented in the radial flow direction.

It is an object of the present invention, in continuous casting dies, to retard the recrystallization process from the die material to the material of the coolant channel wall, depending on the operating temperature and duration of operation, to increase the useful life and turbulence of the die, It is providing the said continuous casting die which achieves mixing.

The above object is a continuous casting die having a die inner wall portion directed toward the molten metal as the hot side, a die outer wall portion as the low temperature side, and a coolant channel formed by right and left side wall portions according to the present invention. This is achieved by the channel being formed with members that create turbulence. More robust coolant mixing is generally achieved by mounting turbulence generating members. At the same time, the turbulence generating members enlarge the heat transfer surface of the coolant channel to the die wall. These two measures, namely the interaction of the turbulence generation and the expansion of the heat transfer surface, improve the local heat transfer consisting of the coolant which dissipates heat from the wall of the coolant channel to the wall of the die.

The basic principle of all turbulence generating members is based on mass, pulse and energy transport which induces turbulence. The heat transfer made in the coolant channel of the continuous casting die is improved according to the invention. By mixing intensively, the turbulence generator further increases the local heat flow density. In other words, the heat removed per surface unit is increased. As turbulence increases in the region of the central flow as well as near the wall, uniform mixing is achieved. Improved mixing of the coolant is achieved through turbulence generating members, the temperature level in copper is lowered, and the process of recrystallization of the material of the die material to the coolant channel wall, which is dependent on the operating temperature and duration of operation, is also delayed. This increases the useful life of the die. The material of the die to die wall portion is, for example, copper, partly copper, or another material. In addition, contaminants and deposits are reduced by increased turbulence and relatively higher shear forces on the hot side of the cooling channel.

At the rear edge of the turbulence generating members, the water flow is separated and an unsteady and swirling, ie turbulent, recirculation zone is created. The first embodiment of the turbulence generating members consists of horizontal steps which are arranged in a coolant, for example formed in a rectangular profile extending over the entire width or partial region of the coolant channel. The second and third embodiments of turbulence generating members take the form of triangular pyramids and winglets. In this form, inwardly rotating wake turbulence is induced, which causes more concentrated coolant mixing. Rear turbulence is observed, for example, at the end of the airfoil vane, or at the rear of the vehicle, which corresponds to a position which is basically undesirable to occur. The turbulence generating members are arranged, for example, in a continuous offset manner on the hot side, and the spacing is determined by the volume expansion of the recirculation zone, which is located mostly in the upper direction of the flow. According to an alternative embodiment to this, since the recycling action extends to the high temperature side, the turbulence generating members can also be installed on the low temperature side. It is also possible to combine the steps mounted horizontally on the hot side of the cooling channel and the triangular pyramid on the cold side. Likewise, to limit the costs associated with manufacturing technology, one may consider installing turbulence generating members only at the inlet of the coolant channel, or only at the height of the meniscus. In addition to the flow technology related effects described above, the heat transfer surface is also slightly increased by turbulent members, for example about 6% in the triangular pyramids described above. In this way the local heat flow density is increased. Therefore, the pressure loss can be kept extremely small by selecting the dimension of the turbulent members not very large.

The basic mode of operation of the coolant channel according to the invention can be assigned according to numerical simulations of flow (CFD-computational fluid dynamics).

Embodiments of the present invention are described in more detail according to a very schematic drawing.

1 is a three-dimensional view of a portion of a continuous casting die.

FIG. 2 is a front view of a continuous casting die cut with turbulence generating members according to a first embodiment. FIG.

FIG. 3 is a front view of a continuous casting die cut with turbulence generating members according to a second embodiment. FIG.

FIG. 4 is a front view of a continuous casting die cut with turbulence generating members according to a third embodiment. FIG.

5 is a side view of a continuous casting die cut with turbulence generating members.

<Description of main parts of drawing>

1: continuous casting die

2: refrigerant channel

3: inner wall of die

4: die outer wall

5: right side wall

6: left side wall

7: triangular pyramid

8: flow direction

9: horizontal staircase

10: winglet

11: row

1 shows a coolant channel formed by a die inner wall portion 3 facing the molten metal on the high temperature side, a die outer wall portion 4 on the low temperature side, a right side wall portion 5 and a left side wall portion 6. A part of the continuous casting die 1 including (2) is shown in three-dimensional view. The turbulence generating members 7, 9, 10 are mounted on the die inner wall portion 3 on the hot side in the flow direction 8 and protrude into the coolant channel 2.

FIG. 2 shows a front view of the coolant channel 2 in which two rows 11 of turbulence generating members 7 are mounted to the die inner wall 3 in the form of a triangular pyramid. The triangular pyramid has its vertex directed in the direction opposite to the flow direction 8. This arrangement creates a structural resistance. Behind the triangular pyramid coolant behaves in the form of turbulence. The triangular pyramid can also be arranged in an offset manner.

3 shows the turbulence generating members 9 in the form of a horizontal step. This horizontal step is formed, for example, by a rectangular rod (see FIG. 5) extending over the entire width of the coolant channel 2.

A further form of turbulence generating members 10 is shown in FIG. 4. These turbulence generating members 10 take the form of winglets. The winglets known from the aircraft wing, for example, are aligned in rows 11 and fixed to the die inner wall 3 or distributed and fixed to the inner wall of the die, such as the winglets shown below.

All turbulence generating members 7, 9, 10 are configured to protrude from the die inner wall 3 into the coolant channel 2 or vice versa recessed into the die inner wall 3, and the coolant As it flows in the flow direction 8 through the coolant channel 2, it affects the coolant.

Claims (9)

Coolant channel 2 formed by die inner wall portion 3 facing the molten metal on the high temperature side, die outer wall portion 4 on the low temperature side, right side wall portion 5, and left side wall portion 6 In the continuous casting die 1 comprising: The coolant channel (2) is characterized in that it is formed with a turbulence generating member (7, 9, 10). A continuous casting die (1) according to claim 1, characterized in that the turbulence generating member (7) is formed in the form of a triangular pyramid. A continuous casting die (1) according to claim 1, characterized in that the turbulence generating member (9) is formed in the form of a horizontal step. A continuous casting die (1) according to claim 1, characterized in that the turbulence generating member (10) is formed in the form of a winglet. 5. Continuous casting die (1) according to any one of the preceding claims, characterized in that the turbulence generating member (7, 9, 10) is arranged on the die inner wall portion (3). 5. Continuous casting die (1) according to any one of the preceding claims, characterized in that the turbulence generating member (7, 9, 10) is arranged on the die outer wall (4). 5. Continuous casting die (1) according to any of the preceding claims, characterized in that the turbulence generating members (7, 10) are arranged in rows (11). 5. Continuous casting die (1) according to any one of the preceding claims, characterized in that the turbulence generating members (7, 10) are arranged in an offset manner in rows (11). 9. Continuous casting die (1) according to any one of the preceding claims, characterized in that the turbulence generating member (7, 9, 10) is arranged in the meniscus region.

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