JPS6015426B2 - Electromagnetic stirring device in continuous slab casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an electromagnetic method for continuous casting of molten metal, especially continuous casting of molten steel. It is related to. A first object of the present invention is to provide a sound material with fewer skin holes by applying a uniform flow to the vicinity of a flawed surface when casting rimmed or semi-killed steel in continuous steel casting. The second purpose is to help the inclusions of the injected molten metal float up, and to reduce defects by allowing the molten metal to act on the surface of the molten metal at a uniform temperature. In general, many ideas have been published regarding the application of electromagnetic casters to continuous casting, but most of them are aimed at applying them to blooms and billets. It is a recent example that was designed for slabs, and was built in the 1970s.
No. 554 proposed improving the coagulation structure by applying parallel flow in a uniaxial direction, and U.S. Pat. It is said that Next, Mochikai Sho 47-33
No. 027 attempts to install an electromagnetic device on the upper surface side of the secondary cooling zone of the curved coin equipment to help float the inclusions. The first purpose of performing electromagnetic light azagation using these methods is to reduce the polarization of the solidified ends and to change the solidified structure from columnar crystals to equiaxed crystals (as disclosed in Japanese Patent Application Laid-Open No. 47-33027). (There are also methods that try to help the inclusions float up, as shown in the above). This invention is disclosed in US Pat. No. 36565.
Similar to No. 37, it applies a magnetic field perpendicular to the direction of travel, but
The purpose and implementation are different from this, and the ultimate goal is to form a uniform flow on the wound surface and apply the washing liquid flow to the shell at the beginning of solidification to prevent the adhesion of air bubbles and inclusions. They differ fundamentally in that their purpose is to impart a superior surface to steel. Now, the inventors put a low melting point alloy made of blue lead-lead-tin into a 18-18 stainless steel tank that is four times as tall as the medium one.
In order to understand the flow situation of the molten metal, we conducted an electromagnetic rope test using a coil that generates a magnetic field moving in the middle direction. As a result, it was found that when the position of the coil, that is, the position in the height direction where the coil is arranged, changes, the flow velocity of the molten metal changes even at the melt surface position and near the coil position. The present invention is based on the inventor's knowledge of electromagnetic systems and the discovery of the dependence of flow velocity on the coil position described herein, and from these, it is possible to obtain the optimum flow condition (flow velocity, etc.) in continuous slab casting. This was considered in the First of all, Figure 1 is a diagram of a model experimental tank made of a low melting point alloy in order to understand the relationship between the coil position and the flow situation of this molten metal, especially the flow velocity. A low melting point alloy E is placed in a corresponding tank D, and the tank has a double shell and is heated with steam to melt the low melting point alloy. The coil is placed at the center C in the height direction of the rice cake, and the speed is measured by placing pitot tubes at measurement points A and B at different heights. This figure shows that when a unidirectional electromagnetic rope flow is applied to the inside of the slab, a large circulating flow is basically formed near the same depth as the inside of the tank, and the position of the coil is It can be seen that at a position shallower than the middle dimension, significant flow interference occurs and the flow velocity decreases even at the wound surface and coil position. It was thus found that the relationship between the flow velocity measured at measurement points A and B and the change in the height direction of the coil position is as shown in Fig. 2A. The inventor filed a patent application No. 48-8004.
In No. 8, he submitted ``Electromagnetic lighting device for continuous slab casting'' and acknowledged the effect of forcibly forming a circulating flow within the slab surface using multiple coils. In this way, it was discovered that a good circulation flow can be formed when the shape of the slab matches the shape of the slab. In addition, the present inventor has submitted a method for continuous casting of rimmed steel and semi-killed steel in Tokusho No. 48-40642, and such steels are particularly easy to manufacture under the action of a rotating magnetic field, such as scales and slabs. It was shown in 2013 that although it is possible to manufacture a device that is quite good even in a moving magnetic field, it cannot be said to be completely good. Based on the above-mentioned knowledge, it is now possible to present a complete solution. Basically, in the present invention, the coil that generates the moving magnetic field is placed in sufficient contact with the mold so that the moving magnetic field acts in the middle direction, and the inside of the coin is L.
As a general rule, the coil should be installed at the depth of the sound from the wound surface. Naturally, the installation range is within a certain range, so that range is (o-7 to 1-3) X poison. If this tin fitting position is set to blue, the frame Azusa flow will be symmetrical to Naka-Naka'〇. For this reason, if the flow forms one rotating flow, it may be allowed to be somewhat deep, but if two rotating flows form, the depth cannot be made too deep because of mutual interference. The reason why the lower limit is limited to 0.7 in the present invention is due to the following reasons. That is o. Shobyoman (
If the coil is installed in a river (less than 70mm river), the flow velocity will drop significantly and it will be difficult to form a uniform flow.Furthermore, when measuring at point B as shown in Figure 2, there will be some counterflow due to eddies. This is because it is known that it is formed. Furthermore, if the upper limit is .--, pinholes may occur, and this may remain as a defect in the finished product. By installing the coil at a specific position in this way, a uniform flow acts near the hot water surface. When casting under conditions where such a flow acts, the solidified shell in the area where this flow acts is likely to be uniformly washed, but there are very few inclusions or bubble defects on the inner surface. I understand. In order to apply the above basic research to an actual machine, we decided to install an electromagnetic coil with a length of 2100 kites and a 3-phase 6-pole linear moving magnetic field that generates a linearly moving magnetic field into a continuous casting machine that is capable of casting up to 220 moulds. This type of coil is already well known. However, in order to install the coil, the coil needs to be placed sufficiently close to the coin coin, so it is now necessary to support the coin coin with a structure different from that which normally uses guide rolls. Ta. In addition, since the inside of a slab generally changes significantly, the coil mounting position can be changed accordingly and can be changed at will. In order to satisfy these conditions, the front surface of the coil is placed below a pure brocade mold in which a non-magnetic steel skid or a water-cooled mold (cooling plate) made of non-magnetic steel is water-cooled. The coil body is suspended by a beam or spray zone supporting a mold vibrator,
Moreover, the mounting position can be moved up or down by the screw according to the dimensions of the mold. FIG. 3 shows an example of such an embodiment. Namely, 1 is a regular tundish, 2 is a tundish car, 3 is a vibrating device, 4 is a mold vibrator frame, 5 is a mold, 6 is an electromagnetic lamp lifting device such as a screw, 7 is an electromagnetic flywheel device, and 8 101 is an apron frame of the guide roller shown, 9 is a non-magnetic steel cooling skid, and 11 is a coin coin. Therefore, the thickness of the present invention is 150 to 25 mm x medium 1500 to 2 mm.
It was installed on Kenkyoku-type Hironaka continuous slab casting equipment made by 000 Hada.
The length of the mold is 70 ribs, and in contact with the mold, skids 9 made of 18-8 stainless steel with a thickness of 15 sides, a middle 45 fence, and a length of 80 ribs are arranged at intervals of 2 ribs. Water is injected into this gap by a spray nozzle (not shown). The support body of the present skid 9 has a rigid support mechanism as a whole, and is not directly connected to the mold 5, and its position can be adjusted in accordance with the thickness of the mold together with the spray zone.
The electromagnetic thick clothing layer 7 is mounted on a frame 8 in the spray zone, and has a lifting device 6 such as a screw so that it can be moved over the entire 80-length length of the main skid 9. When casting rimmed steel using the above-mentioned equipment, when a moving magnetic field is applied along the middle direction of the slab and applied to each half of the slab using the electromagnetic caster 7 of the present invention, and the molten steel is cast, as shown in Fig. 4. A symmetrical flow is formed. The coil used in the present invention is a 3-phase, 6-pole coil, and is wired so as to generate a symmetrical flow. Note that 12 in the figure indicates the hot water level. Naturally, as a result, the fly azusa flow became as shown in Fig. 5, but in order to make use of the characteristics of the fly azusa flow for casting, new innovations were naturally required. In particular, when a unidirectional flow is formed, the problem is that the heat field becomes asymmetric with respect to the slab. FIG. 5 shows an injection scheme in which such precautions have been taken. Fig. 5 shows the injection method for Fig. 4, in which 12-1 is a bulge of hot water, 13 is an injection flow, 14 is scum, 15 is molten metal, and 16
17 is a powder, and 17 is an immersion nozzle. In FIG. 5, the injection flow was placed at the center of the two circulation flows, and the injection was performed using a immersion nozzle. Rimmed steel was actually injected using this injection method. The equipment is as described above.
Now, two types of copper with the following components were produced using an oxygen top-blown converter. ．． ○ Si Mn P S
A ○ Molten steel [1] 0.053 0.013
0.28 0.008 0.008 0.028
88ppm (component) [n] 〇. 〇57 0.028
0.35 o. o12 o. o13 Tr 212
[1] is aluminum killed steel, and [b] is silicon semi-killed steel. In the case of [1], sliver behavior occurs due to alumina clusters during normal injection.

[0] has thin pinholes with a diameter of about 0.5 skin on the surface, making it unusable. Thickness 2 for both steel types
The molten metal was coated with powder slag using the pouring method shown in Figure 5 using a slab mold with a diameter of 0.0 and 188.
It was cast at a casting speed of n. When the obtained thin plate was inspected, the sliver tendency, which is known to be caused by alumina clusters, was significantly reduced, and the surface condition was found to be very good. In addition, the copper cast slab in [B] had a few pinholes only at the edges, but it was found that it was sufficiently usable when made into a thin plate. In this experiment, the coil was placed 103 feet (1
．． 1 x Zu・22o Rib (・-3chi),・4 Misaki (・-5 too)
It was installed under three conditions. There was no significant difference in defects in the thin plate between the first and second conditions, but under the third condition, 1.5×1, an increase in defects caused by pinholes was seen at both ends and in the center of the thin plate. . As described above, according to the present invention, surface inclusions in killed steel can be reduced, and pinholes in semi-killed steel can also be removed. One of the effects of the present invention is that it has made it possible to manufacture rimmed steel, semi-killed steel, etc. There was an idea to make rimmed and semi-killed steel using electromagnetic lighting, but it was realized that excellent materials could only be made by using the present invention to form a uniform floating flow near the wound surface. It became. In the present invention, the coil can be placed under the mold. This creates a strong Junhai style. As seen in some proposals (for example, Japanese Patent Laid-Open No. 47-26332), it is impossible to use the mold as a field for the electromagnetic coil. The reason for this is that continuous casting places a high heat load on the mold, so materials other than materials with high thermal conductivity, such as steel, cannot be used. This is because the conductive current that is generated to generate the mold is consumed in the mold. Therefore, with this method, it is not possible to form a hawk flow of 0.2 to 0.5 skin/s or more, which is effective in reducing inclusions and inclusions in rimmed and semi-killed steel. The present invention is an excellent solution to solve these electrical problems and fluid shape problems.
It should be noted that the electromagnetic coil for inducing a traveling magnetic field as used in the present invention is already well known from many documents, so a detailed explanation is omitted. Embodiment of the present invention {1} A coil that generates a traveling magnetic field by multiphase alternating current is installed at right angles to the orthogonal direction of the mirror piece, and the position of this coil from the moat surface is (〇 -7～・-3)X
A method for arranging an electromagnetic casing device in continuous slab casting, which is characterized by applying a strong and uniform casing flow near the hot water surface by being poisonous. [2' A continuous slab casting facility having an electromagnetic flywheel device, which is installed so that the coil position can be changed depending on the slab so that the embodiment {1} can be realized. Lake Coil dimensions are within the maximum medium Lmax of the applied slab, and are approximately 1/2 symmetrical according to the medium L of the slab for each casting.
Method (○) or device (■) using an electromagnetic lamp whose wiring can be changed to form a moving magnetic field in the section. '41 The electromagnetic coil is placed at the bottom of a mold with a water-cooled pure copper cooling surface, and a water-cooled non-magnetic steel shoe is placed directly or indirectly between the mirror piece and the coil body, allowing the coil to move freely. The device according to item (1) above, characterized in that the device is installed so that the distance from the mirror piece to the mirror piece is shortened. '51 [1] A pouring method characterized in that when casting is performed while applying a unidirectional circulation flow, the Rakuyo pouring flow is placed asymmetrically on the upstream side.

[Brief explanation of the drawing]

Figure 1A, the opening is a plan view and front view of a model experimental tank made of a low melting point alloy, which the inventor manufactured in order to understand the relationship between the coil position and the flow situation of the molten metal, and Figure 2A, the opening is the 1st A chart showing the relationship between the flow velocity at measurement points A and B in the figure and changes in the height direction of the coil position, FIG. 3 is an explanatory diagram showing an embodiment of the present invention, and FIG. FIG. 5 is a cross-sectional explanatory diagram showing the injection method for obtaining the fly-azus flow shown in FIG. 4, and FIG. 6 is a macroscopic structure diagram of the slab obtained by the present invention. . A, B...Measurement point, C...Coil position, D...
...Boat, E...Low melting point alloy, 1...Tundish, 2...Tundish car, 3
... Vibration device, 4 ... Frame, 5 ...
... Mold, 6... Lifting device, 7...
Electromagnetic crossing device, 8...Apron frame, 9"
"" skid, 10""" guide roller, 11... money piece, 12... wound surface, 13... injection flow, 1
4... Scum, 15... Molten metal, 16.
...Powder, 17. ．． ．． ...Immersion nozzle. Figure 0 Figure l Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. When applying a moving magnetic field that moves in the slab width direction to a slab half width 1/2L using an electromagnetic coil that generates a moving magnetic field in continuous slab casting, the center position of the electromagnetic coil is located within the mold. Below the surface of the molten metal (0.7~1.
3) An electromagnetic stirring device for continuous casting, characterized in that it is installed so that the ratio is xL/2. 2. In the electromagnetic stirring device according to claim 1, the electromagnetic coil that generates the moving magnetic field is installed in sufficient contact with the mold, and this electromagnetic coil controls the progress of the slab based on conditions limited by the slab size. An electromagnetic stirring device for continuous casting of slabs, characterized in that the device is movably mounted so that the mounting position in the direction can be changed.