JPS58138546A - Continuous casting method of steel - Google Patents

Abstract

PURPOSE:To supply ingots of high temp. having less surface cracks to a rolling stage and to improve the quality of products by incorporating heat pipes which operate at specific temp. or above with rolls or forming the rolls into heat pipe construction. CONSTITUTION:Heat transfers from an ingot C through a roll 1 to the heat medium packed in the cavity part 3 of the roll, and when the heat medium attains >=300 deg.C high temp., the heat medium boils to a gaseous state and transfers axially to the end parts of the roll. Cooling water W is applied on the sides nearer the end parts than the positions where the flanges 4 of the roll 1 are fixed. The vapor phase heat medium in said parts is liquefied and is migrated and returned axially on the inside wall surface of the roll 1 by the capillarity of wicks 2. The surface temp. in the central part in the transverse direction than the positions where the flanges 4 of the roll 1 are fixed is thus maintained at about 400-500 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous casting method for molten metal, such as molten steel.

Continuous casting machines are equipped with rolls that contact two or four sides of the slab's cross section to prevent bulging of a piece and to smoothly pull out the slab.

On the other hand, in order to effectively utilize the sensible heat possessed by a piece after casting without releasing it, and to reduce or omit the heating energy in the process of pressing the slab, it is necessary to start from the continuous casting process. It is necessary to keep the temperature of the output slab as high as possible.

On the other hand, when continuously casting molten steel, etc. (the following explanation will be based on the process of continuously casting molten steel), it is necessary to prevent surface cracks from occurring in the resulting piece.

One way to prevent surface cracks from occurring in the slab after continuous casting is to maintain the surface temperature of the slab at a high and uniform level during the continuous casting process.

As mentioned above, in order to effectively utilize the sensible heat possessed by the piece after -1 and to prevent surface cracks from occurring in the piece after casting, the surface temperature of the slab in the continuous casting process must be kept high and uniform. 'It is necessary to keep it at '.

To maintain slabs at high temperatures during continuous casting processes,
It is effective to reduce the amount of cooling water injected onto the slab surface in the secondary cooling zone of a continuous casting machine. On the other hand, in order to make the surface temperature of the slab uniform, it is effective to uniformly spray the cold comb 1j water over the entire surface of the slab.

In this way, the surface temperature of the blast slab can be made high and uniform, but in the conventional continuous casting process, the rolls for supporting and guiding the slab or for drawing it are
Because it is water-cooled (internally or externally cooled), its temperature is low, and the surface temperature of the slab in contact with this roll is the first.
It descends rapidly as shown in the figure.

Therefore, in order to make the surface temperature of the slab high and uniform (σ), it is necessary to solve the problem of the sudden drop in the surface temperature of the hook due to the rolls.

This invention was made with the aim of solving the above-mentioned problems in the conventional continuous casting process. The gist of this is that when continuously casting molten steel, there is a built-in heat pipe that operates at a temperature of 300°C or higher. It is a continuous steel casting method characterized by the use of rolls with a heat chimney structure to support, restrain, guide, or pull out the slab.

This invention will be explained in detail below.

In the conventional continuous casting process, the rolls used to support and guide the slab and to pull it out are water-cooled, so the surface temperature of the rolls reaches 10°C just before they come into contact with the slab surface.
The temperature is around 0°C.

In this invention, the surface temperature of the roll for supporting and guiding or pulling out the slab is set to 300°C or higher. A heat pipe that operates at a temperature of 300 to 400° C. or higher is applied to the roll. By applying this heat pipe, the temperature of the roll surface immediately before contact with the slab can be increased to at least 400
It becomes possible to maintain the temperature at 500°C.

In order to maintain roll strength above the required level and to keep roll wear to the lowest possible level, and to achieve the objectives of this invention, the roll surface temperature should be kept at 4.
It is optimal to maintain the temperature between 00 and 500°C.

Several examples of the application of heat pipes to rolls will be described when carrying out this invention.

FIG. 2(a) shows the roll itself having a heat pipe structure. In FIG. 2(a), 1 is a roll,
It has a sleeve-like structure. 2 is a wick,
The heat medium, such as Na or naphthalene, is conveyed along the axial direction of the inner wall surface of the roll (sleeve) by the capillary action.

Reference numeral 3 denotes a roll inner cavity, which is filled with a heat medium and serves as a moving path for the heat medium, thereby forming a heat wave.

FIG. 2(b) shows an embodiment in which a heat pipe is built into the roll. In FIG. 2(b), 11 is a roll and 13 is a heat pipe. Although not shown in the drawings, the heat pipe 13 is lined with a wick on its inner wall surface.

Figure 3 shows the state when the roll having the heat pipe structure shown in Figure 2(a) is applied as a roll for a continuous casting machine. In Figure 3 (&), C is the slab (
1 is a roll, 3 is a roll inner cavity, and 4 is a 7-lunge, which is fixed near the axial end of the roll l. W is cooling water, which is applied to the outer surface of the roll on the end side in the roll axis direction than the flange 4, and is applied to the roll inner surface 3.
The heating medium (Naz naphthalene, etc.) filled in the tank is cooled.

To explain the operation of the embodiment shown in FIG. 3(a), heat is transferred from the slab C through the roll 1 to the heat medium (Na% naphthalene, etc.) filled in the roll inner cavity 3. When the heat medium reaches a high temperature (300 to 400°C), the heat medium boils and becomes gaseous, and moves toward the end in the axial direction of the roll. Cooling water W is applied to the end side of the roll (sleeve) 1 from the part where the flan: Sleeve) 1 The inner wall surface is moved in the axial direction to cause reflux. In this way, Roll IQ Fra/J4
The surface temperature of the central part in the width direction is maintained at 400 to 500°C compared to the part where is fixedly installed.

Further, the operation of the embodiment shown in FIG. 3 will be explained. In this example, the heat pipe]3 is the roll 1
1, and the heat pipe 13 is built in the roll 11.
Cooling water W is applied to the outer side of the axial end.

The heat from the slab C passes through the roll 11 and is transferred to the heat pipe 13.
is transferred to the heat medium inside. The behavior of the heat medium is shown in Figure 3 (a
) is similar to the case of the embodiment shown in ). The cooling water at the axial end of the roll 1 or the heat pipe 13 may be supplied not only by water W but also by an air current such as an air current.

In this way, the temperature of the roll surface is 400-500℃
is maintained uniformly.

Since the present invention is constructed and operated as described above, it is possible to improve the strength of the rolls that guide and hold the slab, pull it out, or straighten the slab in the continuous casting process of steel, etc. Continuous casting is possible by maintaining the temperature above the new standard and maintaining the temperature in the 400 to 500°C range to keep wear and tear low, so it is possible to supply high-temperature slabs with extremely few surface cracks to the rolling process. It has excellent effects in terms of energy saving and product quality.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the roll position and slab surface temperature in the prior art, and Figures 2 (a) and (b) are diagrams showing the relationship between roll position and slab surface temperature in the conventional technology, and Figures 2 (a) and (b) show the relationship between roll position and slab surface temperature in the continuous casting process of the present invention. Explanatory diagram showing an example, FIG. 3(a),
(b) is a sectional view showing an embodiment in which a heat pipe is applied to a roll in a continuous casting process according to the present invention. 1.11: Roll 3: Roll inner cavity 13: Heat pipe C: Slab

Claims (1)

[Claims] When continuously casting molten steel, the cast slab is supported, constrained, guided, or pulled out using a roll that has a built-in heat pipe or has a heat pipe structure that operates at a temperature of 300°C or higher. Continuous casting method for steel.