JPH0523862B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is directed to a method of injecting molten metal into a sump formed in a part of the peripheral surface of a moving mold such as a cooling drum, for example in a twin drum system. and cool the molten metal,
The present invention relates to a continuous casting method for producing thin slabs by solidification, and particularly to a method for brushing the surface of the moving mold.

[Conventional technology]

Recently, attention has been paid to a method of directly producing thin slabs having a wall thickness of about 1 mm to 10 mm from molten metal such as molten steel using a continuous casting machine. This continuous casting method eliminates the need to manufacture thin plates from thick slabs through a multi-step hot rolling process as in the past, and requires only a light amount of cold rolling to form the slab to its final thickness. In some cases, it is possible to obtain a large economic effect by simplifying the process and equipment, and in many cases it is preferable from the viewpoint of the metal structure.

This type of continuous casting method includes the twin-drum method, in which a pool is formed between a pair of cooling drums that rotate in opposite directions, and the drum-belt method, in which a pool is formed between the cooling drum and the belt. , a single-drum system using one cooling drum, etc.

In both of these methods, the molten metal in the pool is cooled at the part where it contacts the surface of the cooling drum, begins to solidify from the surface, and solidifies gradually toward the center of the thickness while forming a solidified shell. I'll go. Therefore, if molten metal oxides, etc. are partially attached to the surface of the cooling drum, not only will dents remain (transfer) on the surface of the thin slab depending on the thickness of the deposit, but also Because the heat conductivity is different between parts of the kimono and parts without it,
Cooling progresses unevenly on the surface of the slab, which may cause uneven thickness of the slab and, in some cases, wrinkles or cracks.

Therefore, it was considered to use a brush roll to scrape off the deposits on the surface of the cooling drum.
Inventions such as those described in Japanese Patent Application Laid-open No. 60-184449 and Japanese Patent Application Laid-open No. 176650/1983 have been proposed.

[Problem to be solved by the invention]

Brush rolls according to the prior art are provided for the purpose of scraping off deposits on the surface of the cooling drum, but they are not always able to reliably prevent cracking of slabs.
Vertical cracks in slabs due to streak-like deposits that are not completely scraped off by the brush roll, and deposits that remain like axial bands on the surface of the cooling drum due to eccentricity of the brush roll. The kimono causes defects such as periodic wrinkles and horizontal cracks that appear on the slab, and the brush roll causes wear and damage to the plating layer on the surface of the cooling drum, which also causes defects on the slab surface. A new problem is emerging with brush roll systems.

The problem to be solved by the present invention is to solve this new problem faced by the brush roll system and to improve the continuous casting method so that defect-free thin slabs can be efficiently produced. be.

[Means to solve the problem]

As a result of numerous prototypes and experiments conducted at experimental plants, the inventors have discovered that the above-mentioned problems are not necessarily fatal for brush roll systems, and that there are measures that can solve the above-mentioned problems.
Contrary to the conventional method of scraping off as much of the oxide layer of molten metal adhering to the cooling drum as possible to expose the plating surface of the drum, it is possible to smooth out the deposits evenly on the cooling drum and thin them. We discovered that thin slabs with a uniform and defect-free surface can be obtained by forming a film with a constant thickness, and based on this fact, we used a brush roll system to evenly remove deposits. As a result of detailed investigation into what conditions are necessary for smoothing and scraping off excess deposits, the means of the present invention was created.

In order to solve the above-mentioned problems, the present invention aims to reduce the wire diameter to the surface of the moving mold such as the cooling drum.
A brush roll consisting of hard wire rods with a thickness of 0.05 to 0.3 mm and a corrugated shape is applied to the surface of the movable mold in the axial direction of the movable mold at a rate of 0.05 to 0.2 Kg/mm.
To provide a continuous casting method for thin-walled slabs, characterized in that the deposit layer adhering to the surface of the movable mold is leveled by uniformly pressing with a force and rotating at a rotational speed of 500 to 1300 rpm. It is.

[Effect]

In the brushing method of the present invention, instead of scraping off molten metal oxides etc. that adhere irregularly to the surface of the moving mold, on the contrary, the outer diameter of the brush roll is adjusted so that they adhere evenly to the surface of the moving mold. By selecting the wire diameter, material, pressing force, and rotation speed, a uniformly thick layer of deposits is formed on the surface of the moving mold, so that the molten metal that cools on the surface of the moving mold and forms a solidified shell is , there are no parts with different thermal conductivity, so it is cooled uniformly, and there is no local thickness change or distortion.
Defect-free thin slabs with a constant cross-sectional shape and without cracks, dents, wrinkles, etc. are continuously produced.

〔Example〕

Next, an example in which the present invention was implemented in a double-drum system and satisfactory results were obtained will be specifically described.

Figure 1 shows the main parts of a continuous casting machine of this type. 1
and 2 are cooling drums as an example of a moving mold, and have dimensions of 1000 mm in diameter and 800 mm in axial length. Both are supported on bearings (not shown) with an interval of several mm that determines the thickness of the thin slab, and
They are rotated at a speed of 26.5 rotations in opposite directions as shown by the arrows. Reference numerals 3 and 4 denote side weirs provided in contact with both end surfaces of the cooling drums 1 and 2, whereby a pool 5 into which molten steel is injected is formed above the gap between the cooling drums 1 and 2. Ru. 6 is a thin cast steel piece obtained by continuous casting. The cooling drums 1 and 2 are supplied with cooling water through pipes (not shown), and are cooled so that their surfaces have a uniform temperature in the axial direction.

Brush rolls 7 and 8 rotate behind the cooling drums 1 and 2 in sliding contact with their surfaces, and have a length of 800 mm and a diameter of 150 mm. Each of these rotating shafts 9 and 10 is pivoted by a fulcrum shaft 13 on the bases 11 and 12 of the brush roll and is connected to each other by a pair of arms 14 and 14, respectively.
It is supported so that it can revolve. The horizontal rod connecting each pair of arms 14 has bases 11 and 12.
Compression springs 16, 17 supported at one end above
The other ends of the brush rolls 7 and 8 are engaged to apply an optimum pressing force selected from a range of 50 to 150 kg to the brush rolls 7 and 8. The magnitude of the pressing force is very important in the case of the present invention, and it is important to consider the structure and dimensions of the brush roll, the relative speed of the cooling drums 1, 2 and the brush rolls 7, 8, etc. The size is such that deposits are evened out and a thin layer is formed uniformly on the surface. This state is on the contact line between the brush rolls 7 and 8 and the cooling drums 1 and 2, and
It has been found that this can be obtained when a surface pressure in the range of 0.2 kg/mm is applied.

As shown in FIG. 2a, the brush rolls 7 and 8 are made by winding a brush band 19 with thin wires 18 in a spiral shape around a flange 20 and fixing the brush band 19 with spot welding 21 in some places. The one shown in FIG. b is preferable, but it may also be one in which many disc-shaped brushes are laminated, or one in which wires are directly planted on the flange 20.

The wire 18 to be planted is a hard rope wire such as SWRH72A, and since the purpose is to level the deposits rather than scrape it off, it is better to make it as thin as possible, so the diameter of the wire 18 is 0.15 mm, Use a material with fine bends formed in a wavy or zigzag shape before cutting. The wires 18 of the brush rolls 7 and 8 must not be uneven in density and must be uniformly distributed. The length of the wire 18 is
44.8 mm, and when the brush rolls 7 and 8 are pressed against the cooling drums 1 and 2 with a predetermined pressing force and rotated relative to each other, the wire 18 is slightly bent in the bending direction, and the surface of the cooling drums 1 and 2 is The length should be long enough not to damage the

As shown in Figure 4, when the rotational speed of the brush roll is set to 1,300 rpm or more for the spiral type and 1,750 rpm or more for the disc type, the centrifugal force causes the strands to rise from the fluttering shape and to rise due to elongation from the wave shape, making it appear as if it were rigid. As if using bare wire, the drum may be damaged or rebound, resulting in uneven brushing. On the other hand, we tested the brushing performance by coating the cut plate with boron nitride (BN) to determine the lower limit of rotation speed for obtaining effective brushing performance.
A good brushing effect was obtained above 500 rpm.

An example of applying this method to the actual machine shown in Figure 1 is shown in Figure 4.
Indicated by an arrow in the figure. The conditions at that time were a spiral type brush roll, and the rotation speed was 600 rpm.
It is said that As shown in Fig. 3, the direction of rotation is the same as that of the cooling drum with which the brush roll 7 or 8 comes into sliding contact. Make sure that any deposits are scraped downward.

The drive of the brush rolls 7, 8 is, in the embodiment shown in FIG.
A belt 24 is placed between the pulley 22 attached to the motor 10 and the compound pulley 23 which rotates freely on the fulcrum shaft 13, and a belt 24 is placed between the pulley 26 attached to the rotating shaft of the motor 25 and the compound pulley 23. 27
Although this is carried out using a transmission device constructed by multiplying the above, it is of course possible to use other transmission devices.

In the illustrated embodiment, a twin-drum type movable mold having cooling drums 1 and 2 is used as the movable mold, but the present invention can also be applied to movable molds of other methods.

〔Effect of the invention〕

By carrying out the present invention, it is now possible to easily produce thin slabs with a uniform thickness of about 1 to 10 mm, even for metals such as stainless steel, which are difficult to cast thinly continuously. Furthermore, defects such as vertical cracks, horizontal cracks, wrinkles, and dents can be almost completely prevented.

Furthermore, unlike conventional brush roll systems, the main purpose of the brush roll system of the present invention is not to scrape off deposits on the surface of the moving mold;
Since the surface is not strongly rubbed, the plating layer on the surface of the mold is not damaged, and the life of the mold can be extended.

[Brief explanation of drawings]

Figure 1 is a perspective view showing the main structure of a twin-drum continuous casting machine, and Figure 2 is a perspective view showing the manufacturing process of a spiral type brush roll, with a showing the winding process and b showing the finished product. show. Fig. 3 is a conceptual diagram showing the sliding contact between the cooling drum and the brush roll and each direction of rotation, and Fig. 4 is a diagram showing the relationship between the number of rotations of the brush roll and the floating amount of the tip of the brush. It is. 1, 2...Cooling drum (moving mold), 3, 4...
...Side weir, 5... Water pool, 6... Thin cast (rope) piece, 7, 8... Brush roll, 13... Fulcrum shaft, 14... Arm, 16, 17... Compression spring, 18... ...Wire, 19...Brush band, 20...
...Flange, 21...Spot welding, 25...Motor.

Claims (1)

[Claims] 1. A continuous casting method in which molten metal is injected into a sump formed on a part of the peripheral surface of a moving mold, and the molten metal is cooled and solidified to produce a thin-walled mold,
A brush roll constituted by implanting hard wire rods having a waveform shape with a diameter of 0.05 to 0.3 mm is placed on the surface of the movable mold in the axial direction of the movable mold.
A continuous casting method for thin-walled slabs, characterized in that the deposit layer adhering to the surface of the movable mold is leveled by pressing with a force of 0.2 Kg/mm and rotating at a rotational speed of 500 to 1300 rpm.