JPS63252645A - Continuous casting mold with heating function and continuous casting method - Google Patents

Abstract

PURPOSE:To improve the quality of a cast slab by arranging a guiding tube for molten metal over the whole length of inner side of a heating zone and cooling body of a mold and also arranging a temp. detector at the downstream side from a meniscus in the heating zone. CONSTITUTION:An exothermic body of an electromagnetic induction coil 8, etc., is built in the mold 4 to form the heating zone 5 having low electric conductivity, and the guiding tube 7 is arranged over the whole length of the inner side of the heating zone 5 and the cooling zone 6. Further, the temp. detector 9 penetrating the heating zone 5 and the guiding tube 7 is arranged at downstream side from the meniscus in molten steel. The temp. detected by the temp. detector 9 is compared with the aimed setting temp. by a comparator 13 and frequency or power in a power source 15 is controlled, and the detected temp. is maintained to more than melting point of the molten steel. Invasion of the molten steel into gap between the heating zone 5 and the cooling zone 6 is prevented by existence of the guiding tube 7 and rapid variation of the molten steel is restrained. By this method, the development of defect on the surface of the cast slab is prevented and the quality of the cast slab is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a continuous casting mold and a continuous casting method that prevent M-piece surface defects, defects due to non-metallic inclusions, etc. in continuous casting of molten metal. It is.

Conventional technology Continuous PI manufacturing of molten metal is aimed at improving the yield by 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to provide a detailed explanation of the present invention, which is widely used in the production of metal materials such as aluminum, copper, and gold, continuous casting of steel, which is most popular and produced in large quantities, will be taken as an example.

Continuous casting of steel (hereinafter referred to as CC) can be roughly classified into the following two types. One is the slab and H! 1 is a type that performs relative motion and is called an asynchronous CC.It is a method in which molten steel is first received from a ladle into an intermediate container called a tundish, and then continuously poured into a mold from the tundish, and solidification is completed while cooling. This applies to vertical CC1 curved CC, etc., which are separated from the molten steel intermediate container. Since this format is the most productive and widespread, it will be commonly used from now on.
There is also a type of horizontal CC that combines an intermediate container and a mold.

The other type is called synchronous CC, in which the mold has a roll-shaped, belt-shaped, or wheel-shaped mold, and the mold and slab are cooled and solidified while integrally interlocking with each other.

Normally, the main function of pI type CC is to generate a solidified shell, so water-cooled Cu is used as the M type material. However, it is common to use n1 lubricant (powder) to prevent the molten steel from adhering to the mold. For good slabs and stable operation, it is essential to prevent the adhesion of molten steel and to form a lubricating film of powder, and a mold vibration device such as mechanical vibration is required in the casting direction.

However, due to powder casting and mold vibration, surface defects such as pull-out marks called oscillation marks, bubbles, and inclusion defects occur inadvertently, and slab defects occur frequently due to the -F increase in casting speed. Furthermore, there are many problems such as a casting failure called breakout.

These results are due to the fact that the solidification start point of the lagoon t coincides with the solidification start point in principle. In other words, the inclusions observed on the surface or surface layer of the slab are caused by the inclusions brought in from the ladle or tundish penetrating deep into the mold by the discharge flow of molten steel, and the inclusions float away as the discharge flow decreases. This is because it is captured by the slab. In addition, surface defects on the slab surface are caused by changes in the shape of the melt surface near the melt surface or deformation of the initially solidified shell due to the mold lubricant used in casting, and it has been revealed that these defects normally occur unavoidably in the CC method. .

On the other hand, horizontal CC is known to have the advantage of superior quality such as slab inclusions because the molten metal surface and solidification position are separated, but the solidified shell inside the mold is removed using break rings etc. Since the M-type ITT ability is achieved only by sufficiently developing the M type, intermittent drawing and mold vibration are essential, and surface defects called cold shut cracks and cold shut marks occur inadvertently.
2. The method to prevent it has not yet been established.

Against this background, various reforms have been attempted. For example, JP-A-54-15424 and JP-A-80-145.
No. 249 considers a heating device for generating solidified shells in water fCC only within the mold. In other words, in JP-A No. 54-15424, an induction heating device is installed in the conduit on the mold entry side in order to prevent abnormal solidification (referred to as hot mass) occurring on the mold entry side and stabilize the operation. be. However, this technology does not take into account the fact that molten steel is inserted into the gap between the joint between the mold and the conduit located immediately before it, and the high temperature molten steel in the conduit is cooled by the cooling mold placed immediately after it. Therefore, the temperature difference causes rapid cooling, which is unfavorable in terms of quality.

In JP-A No. 60-145249, the heating device and the mold body are arranged in this order, and a temperature sensor is provided in between to control the start of solidified shell formation at a desired position. And, the installation position of the temperature sensor is on the heating device!
The end portion on the side of the Type 6 main body is shaped like a sleeve and is provided in this portion.

However, this method also has the same drawbacks as described above. In other words, if the solidification start point moves from the tip of the sleeve to the mold body side for some reason, there is a concern that molten steel may enter from the connection between the sleeve and the mold body, and the mold is used for cooling from a high-temperature heating device. When moving to the main body, the rapid temperature change adversely affects the quality of the slab surface.

In addition, a temperature sensor is installed between the heating section and the mold body, which is the cooling section, but since a solidified shell has already formed at this temperature detection position, the temperature is measured through the solidified shell. , the sensitivity is extremely reduced due to the heat transfer resistance of the solidified shell, making it difficult to control the solidified position. Furthermore, due to the nature of the electric heating coil, it is common for the longitudinal center of the coil to exhibit the highest temperature, so it is clear that the temperature measured downstream of the electric heating coil will show a lower value than the actual molten metal temperature. However, if we take into account that the temperature is measured through a solidified shell as mentioned above, the indicated temperature will show a significantly different value, which is impractical.

For example, in order to improve slab segregation, it is necessary to minimize the degree of superheating of molten steel, but it is difficult to identify the solidification position due to poor detection sensitivity and dynamic changes in the temperature field due to drawing. It is difficult to do so, and heating is performed more than necessary, leading to high overmaturity casting, resulting in quality deterioration and making it impossible to achieve the purpose.

Furthermore, in Japanese Patent Application Laid-Open No. 61-Ei3348, there are
In, casting 41! Disclosed is a means for preventing solidification in the molten steel meniscus by providing a heater in a part of the molten steel.

However, this technique also has exactly the same difficulties as the former two.

Problems to be Solved by the Invention The present invention has been made in view of these circumstances.
In order to fundamentally solve the problem of slab surface defects and inclusions in the molten metal casting process, we control the formation of an initial solidification shell in the mold, stably separating the molten metal surface and the solidification start point, and
The purpose of the present invention is to provide a continuous PI casting mold and a casting method that have excellent slab surface properties and operability.

Means for Solving the Problems The present invention has been made with the aim of completely preventing surface defects in slabs and preventing the intrusion of inclusions, which have been difficult with conventional methods. is a continuous P
In a mold for I-making, a heating zone with low conductivity and a cooling zone are formed from the molten metal entry side, and the entire inside of the mold is preferably filled with molten metal made of explosive conductive material 4. A continuous casting mold is characterized in that an inlet pipe is arranged to form an integral structure, and a temperature detector is installed downstream of the meniscus of the heating zone. A continuous #JJ manufacturing method characterized in that the temperature detected by the molten metal temperature detector is maintained at 1 - below the molten metal liquidus temperature, and the solidification start point is located downstream from the installation position of the molten steel temperature detector. is the basic invention.

The electric power 81 is the heating source for the heating zone of the mold of the present invention.
A structure is provided in which a plurality of induction coils are provided and the frequency can be changed to any value for each induction coil.

It also includes appropriately selecting and utilizing the characteristics of the heating power and the melt w4 stirring power, which vary depending on the power frequency of the electromagnetic induction coil that is the heating source.

The final IJI will be further explained below using figures. The drawings show an embodiment of the present invention, and Fig. 1 is an overall configuration diagram of the device;
Figures 2 and 3 are explanatory diagrams of the casting method, Figure 4 is an explanatory diagram of another embodiment, and Figure 5 is the relationship between the power frequency, heating power applied to molten steel, and stirring power in the present invention. FIG.

In FIG. 1, l is a ladle (or intermediate container), 2 is an immersion nozzle, 4 is a mold, and is composed of a heating zone 5, a cooling zone 6, and a molten steel introduction pipe 7. Preferably, the heating zone 5 has a heating element such as an electromagnetic induction coil 8 built therein, and the material of the heating zone 5 itself is made of a poorly conductive material to prevent absorption of the electromagnetic force of the electromagnetic induction coil 8.

The cooling zone 6 is preferably internally water-cooled and made of steel, which is commonly used. The introduction pipe 7 shall be provided along the entire length inside the heating zone 5 and the cooling zone 6, and its material is t? ! Preferably, for the same reason as the heating zone 5, it should be fi conductive. Specifically, corrosion resistance can also be achieved by using one or a mixture of two or more of oxides such as zirconia, alumina, silica, and magnesia, graphite, carbides, nitrides, borides, and the like.

In addition, the part of the introduction pipe 7 that comes into contact with the heating zone 5 is made to have poor conductivity.
Most preferably, the portion in contact with the cooling zone 6 is electrically conductive. Introducing t'rf7 into heating zone 5. By providing the cooling zone 6 over the entire length, it is possible to prevent molten steel from entering the gap between the heating zone 5 and the cooling zone 6 and to prevent sudden transition of slabs or molten steel from the heating zone 5 to the cooling zone 6. It can prevent temperature changes (rapid cooling) and is effective in preventing surface defects in slabs.

Reference numeral 9 denotes a temperature detector, which penetrates the heating zone and the introduction pipe and is installed downstream of the molten steel meniscus (lower in the figure).

IO represents a guide roller, 11 represents a cooling water spray, and 12 represents a solidified slab.

Figures 2 and 3 are illustrations of the continuous casting method of the present invention.
A comparator 13 compares the temperature detected by the temperature detector 9 shown in FIG. , change the frequency or power of the power source 15,
Input to 7ft magnetic induction coil 8. That is, the temperature sensor 9
The temperature at the detection point shall be higher than the melting point of molten steel.

As a result, the solidification start point of the slab can be controlled to be located at the position shown in the figure from the position where the temperature detector 9 is installed. In other words, the solidification start point can be positioned at one point from the meniscus, thereby preventing the occurrence of defects on the surface of the slab.

Fig. 3 shows an example of the method described in 1i1 over the course of one hour. After preheating the heating zone, the input power is changed according to the detected temperature of the molten steel casting width, and the molten steel temperature is constantly maintained in the liquid phase. The temperature is controlled to be above the linear temperature (melting point).

In FIG. 4, a plurality of sets of IT electromagnetic induction coils built into the heating zone 5 are provided, and the heat generation of each coil is controlled by connecting each set to a different power source.

That is, the -h part temperature detector 9-1 is installed near the -h part coil 8-1.
1, and connect it to L part comparison 'jA13-1,
[Partly station wave number controller 14-1, partly provided with power supply 15-1.

Separately from these, a lower temperature detector 9-2 is provided near the lower coil 8-2, and connected to this, the lower part comparator +
3-2, lower frequency control: Al1-2, lower power supply 15
-2 is provided.

With this configuration, the temperature distribution in the length direction of the heating zone can be set to a desired value. In particular, in the case of a set of electromagnetic induction coils 8 as shown in FIG.
The temperature is relatively low.

On the other hand, by adopting the structure shown in FIG. 4, it is possible to make the temperature uniform in the longitudinal direction of the heating zone, and it is also possible to obtain an arbitrary temperature at the -L portion and the lower portion.

FIG. 5 shows the degree of heating that can be applied to molten steel when the mold of the present invention is used, and the stirring force of the molten steel that is generated as a secondary effect by using an electromagnetic induction coil.

When used as the low-inductivity heating zone and inlet pipe of the present invention, both heating power and stirring power are larger than those of conventionally used copper molds. Both the heating power and the stirring power draw a unique curve. Therefore, when you want to raise the molten steel temperature higher, operate the power supply frequency at a higher value, so that the molten steel temperature goes below the target value and the heating is not done too much. When you no longer feel safe, set the power frequency to a low value and increase the PIl agitation force to promote floating of nonmetallic inclusions.

Effects of Problem II As explained above, according to the present invention, (1) Providing an inlet pipe prevents molten steel from entering the fl++ gap between the heating 1' IF and the cooling zone, and also prevents high temperature The rapid temperature change during the transition of molten steel and slabs from the cooling zone to the low-temperature cooling zone can be alleviated by the introduction pipe, and the quality of the slab surface can be improved.

(2) By providing the temperature detector downstream of the meniscus at the 8-1), the temperature of the molten steel before solidification can be detected, and the solidification start point can be reliably located downstream of the meniscus.

(3) When the heating zone and the introduction pipe are made to have low conductivity, the heating power and stirring power for molten steel can be increased;
The changing characteristics of heating power and stirring power that change depending on the power supply frequency can be utilized, and the necessary heating and stirring can be obtained when desired.

4. [The theory behind the scenes II] The drawings show an embodiment of the present invention, and Fig. 1 is an overall configuration diagram of the apparatus of the present invention, Fig. fS2, and Fig. 3 are explanations of the casting method of the present invention. Figure 4 is an explanatory diagram of an example using multiple sets of electromagnetic coils, and Figure 5 is an explanatory diagram showing the relationship between the heating power and stirring power applied to the source frequency steel when the mold of the present invention is used. be.

l... - ladle (or intermediate container), 2... immersion nozzle,
4. Fist mold, 5. Φ heating zone, 6 Φ. cooling zone, 7.
Introductory pipe, 8. Electromagnetic induction coil, 8-1. Shoribe coil, 8-2. Lower coil, 9. Fist temperature detector, 9-1.-E cloth temperature detection. 9-2 Lower temperature detector, 10 +1φ guide roller, 11-- Cooling water spray, 12-- 21 pieces, 13-- Fist comparison.
device, 13-1... (two-part comparator, 13-2...'F
Part comparator, 14...φ frequency controller, 14-1...
1 Part station wave number controller, 14-2...Do part frequency controller, 15...Electrolytic erosion, 15-1-φ/L part power supply, 15-2
...Do part power supply.

Attorney 1-: Masao Inoue Dye 1 ■

Claims (4)

[Claims] (1) In a continuous casting mold, a poorly conductive heating zone and a conductive cooling zone are formed from the molten metal entry side, and a molten metal introduction pipe is arranged along the entire length inside the heating zone and cooling zone. A continuous casting mold having a heating function, further comprising a temperature detector provided downstream of the meniscus of the heating zone. (2) An electromagnetic induction coil is used as a heating source for the heating zone, and a plurality of electromagnetic induction coils are provided, each connected to a separate power source, and the power frequency can be changed for each electromagnetic induction coil. A continuous casting mold having a heating function according to claim 1. (3) From the side where the molten metal enters, a poorly conductive heating zone is followed by a conductive cooling zone, and a molten metal introduction pipe is arranged along the entire length inside the heating zone and cooling zone. In a continuous casting mold configured with a temperature detector installed downstream of the meniscus, the molten metal is heated by a heating zone so that the temperature detected by the molten metal temperature detector is always equal to or higher than the liquidus temperature of the molten metal. A continuous casting method with a distinctive heating function. (4) From the molten metal entry side, a poorly conductive heating zone is followed by a conductive cooling zone, and a molten metal introduction pipe is arranged along the entire length inside the heating zone and cooling zone, and the heating zone In a continuous casting mold configured with a temperature detector installed downstream of the meniscus, the heating power to the molten metal changes depending on the power frequency of the electromagnetic induction coil, which is the heating source of the heating zone.
A continuous casting method having a heating function, which is characterized by appropriately selecting and utilizing the changing characteristics of stirring force.