JPS6021168A - Tundish for continuous casting - Google Patents

Abstract

PURPOSE:To decrease the degree of overheating of a molten metal and to form a uniformly and satisfactorily solidified shell by segmenting a tundish to a receiving chamber and a pouring chamber which are communicated with each other via a space and providing a heating means, stirring means, pressurizing means and upward nozzle to the pouring chamber. CONSTITUTION:A tundish is segmented by refractory gates 12, 12' to a receiving chamber 13 having a small volume and a pouring chamber 14 having a large volume which are communicated with each other via a space 28. The chamber 14 is hermetically closed by a cover 15 and is maintained in an inert gaseous atmosphere of a prescribed pressure by a valve 17. A molten metal 25 is conducted to the chamber 13 where nonmetallic inclusions 27 are floated. The molten metal is then moved via the space 28 to the chamber 14 and the molten metal surface is detected with a detector 30. The molten metal is reserved therein up to a prescribed head 29. The temp. of the molten metal 25 is measured with a thermocouple 31 and the molten metal is heated with a heating means 18 and at the same time weak circulating flow 32 is given thereto by a stirring means 19. When the molten metal 25 is heated to the target temp., an inert gas is introduced via a valve 17 to the inside of the chamber 14 to pressurize the same and a slide- type valve 20 is opened to feed the molten metal 25 from an upward nozzle 22 via a casting nozzle 21 toward rolls 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tundish in continuous casting equipment for thin metal sheets.

As an apparatus for continuously casting thin plates of 1 to 10 mm directly from molten metal, a twin belt type or twin roll type synchronous continuous casting machine as shown in Fig. 1h is generally known. In these continuous thin plate casting machines (thin plate continuous casting machines), the casting speed reaches several tens of times that of conventional continuous slab casting machines in order to ensure the same production volume as conventional slab casting machines. Therefore, in continuous thin plate casting, it is important to control the initial solidification state, and it is necessary to appropriately control the solidification shell growth rate. That is, especially in the case of a twin-roll type as shown in FIG. 1, when the molten metal solidifies between the casting rolls 1 and 1, the solidification completion point 5 is upstream of the closest point on the roll surface. If it becomes difficult to pull out the solidified slab 2 and the solidification completion point 5 is located downstream of the closest point to the roll surface, the plate may bulge or break out. Therefore, it is necessary to reduce the degree of superheating of the molten metal 7 and form a uniform solidified shell 3 in a short time. However, with the tan tinshu provided in the conventional continuous casting machine, the thickness of 4JM il, I! It is difficult to maintain a small degree of superheat that allows casting and to control the degree of superheat with high precision.

Furthermore, unlike the mold section of conventional continuous casting machines, the casting nozzle of the Thin & Continuous V4 machine does not have the function of floatingly separating the non-metallic inclusions 6 in the molten metal 7, and the inclusions float and separate. There is not enough residence time for the molten metal to melt.

That is, nonmetallic inclusions introduced into the casting nozzle are trapped in the solidified shell 3 as they are, resulting in product defects. Therefore, there is a need for a tundish that can more effectively separate and remove non-metallic inclusions than conventional tundishes.

Further, the conventional tundish nozzle is a submerged nozzle 8, and the discharge flow 8 from the submerged nozzle receives the molten metal head IO and has a high flow velocity. In the case of continuous thin plate casting, when the discharge stream 9 collides with the solidified shell 3, the shell is partially remelted, causing unrestricted shell development and causing breakout and plate deformation. Furthermore, having a free surface 11 of the molten metal in the casting nozzle causes the discharge flow 8 to entrain scum and the like on the free surface.

The present invention was made in order to solve the above problems, and the degree of superheat and the variation in the degree of superheat are small, and the molten metal in which nonmetallic inclusions are sufficiently floated and separated can be produced at a small static pressure and linear velocity of the molten metal. The object of the present invention is to provide a tundish that can be supplied to a casting nozzle of a continuous thin plate casting machine.

According to the present invention, a weir that divides the molten metal at the surface and communicates it at the bottom is used to divide the molten metal into a small volume receiving chamber that receives the molten metal from the ladle and a large capacity molten metal supply chamber that supplies the molten metal to the continuous casting device. The hot water supply chamber is provided with a heating means and a stirring means for providing a circulating flow, and further has a valve means at the molten metal supply port and a nozzle extending from the bottom of the hot water supply chamber to almost the surface of the hot water in the hot water supply chamber, and further has a fully closed lid. A tundish for continuous metal casting is provided, which is characterized by having a hot water supply chamber pressurizing means. The gist of the present invention is that when supplying molten metal with a low degree of superheating and small variations in the degree of superheating to a continuous casting device, the hot water supply chamber of the tundish is hermetically sealed, and the casting nozzles are arranged in one direction. The idea is to adjust the static pressure of the molten metal in the casting nozzle by offsetting the head and pressurizing the head space.

Hereinafter, one embodiment of the present invention will be described with reference to FIG.

The tandish container consists of an iron shell and a refractory material inside, and is divided into two large and small chambers by a refractory weir 12.12'. There is no need for the weir rising from the bottom. The room with a small volume is the hot water receiving room 13, and the room with a large capacity is the hot water receiving room I4.
It is. The hot water supply chamber 14 is sealed with a lid 15 made of an iron skin lined with refractory material, and inert gas such as Ar is supplied into the hot water supply chamber 14 to pressurize the inside of the hot water supply chamber 14. It is connected to a valve 17 for adjusting pressurization. Note that a backing 38 made of silicone rubber or the like is used between the tundish container and the Qi 15. A channel type induction furnace 18 is installed on the side wall of the hot water supply chamber, and an electromagnetic stirring device 19 is installed on the opposing side wall. A slide valve 20 is connected to the molten metal outlet at the bottom of the hot water supply chamber, and a tundish nozzle 22 that can be closely connected to a casting nozzle 21 of a thin plate continuous caster and capable of DJing is also connected. The hot water receiving chamber 13 is covered with a cheek 23 and has an atmosphere of inert gas such as Ar. Hot water supply room 14, slide valve 20. The casting nozzle 21 of the thin plate continuous casting machine has an electrodeposited structure. Both the tundish nozzle 22 and the casting nozzle 21 are made of refractory material, and are set in a state in which they are electrodeposited together using a tenon. The joint is sealed with plastic refractories, core paste, etc. 24 to prevent outside air from entering. The casting nozzle extends upward.

The molten metal 25 is guided from the ladle 26 to the receiving chamber 13, and the nonmetallic inclusions 27 at this point are floated. The molten metal 25 is the weir 12,
12' and moves to the hot water supply room 14 through the gap 28. Before starting casting, the slide valve 20 is closed, and the molten metal is stored until a predetermined head 28 is reached. The hot water level in the tundish is detected by a hot water level detector 30 installed on the side wall of the tundish.

There, the temperature is measured continuously or intermittently using a thermocouple 31, and the material is heated in a channel type induction furnace 18 until it reaches a giant temperature. Thereafter, the temperature measurement results are also fed-punctured for power control of the channel type induction furnace 18. In order to prevent the temperature of the molten metal in the hot water supply chamber from becoming non-uniform depending on the position, a weak circulating flow 32 is uniformly applied to the molten metal by an electromagnetic stirring device 19. At this time, the mixture should be stirred weakly so as not to re-involve the inclusions. Since the amount of molten metal accommodated in the hot water supply chamber 14 is sufficiently large, the residence time of the molten metal in the hot water supply chamber is long enough for inclusions to float and separate. Furthermore, by having a heating device, the molten metal can stay for a long time without worrying about the temperature of the molten metal decreasing. When the molten metal temperature reaches the target temperature, the slide valve 20 is opened to start casting. However, if only the slide valve 20 is opened, the molten metal level in the casting nozzle 21 is set so that it does not reach the height that can be cast, so the hot water supply chamber 1
4 through the Ar gas supply valve 17, the inside of the hot water supply chamber is appropriately pressurized, the hot water level in the casting nozzle is raised by t, and casting is started.

However, excessive pressure should not be applied, since leakage is likely to occur from the gap 33 between the No. 14 nozzle and the roll or between the belt of the casting nozzle ('p, in the case of a belt type).

In this embodiment, the linear velocity of the molten metal discharged from the tundish nozzle 22 is determined by the casting speed and the cross-sectional area of the tundish nozzle, so by increasing the cross-sectional area of the tundish nozzle, the flow velocity of the discharge stream 34 can be freely adjusted. can be made smaller. As a result, the collision between the solidified shell and the discharge flow is alleviated, and uniform shell growth is achieved.

Note that the valve at the molten metal outlet may be a stopper shown in FIG. 4, 35. By heating the tundish nozzle and/or the casting nozzle using a heating means such as the high frequency induction coil 37, clogging of that portion can be prevented. In addition, the close connection between the dandy nozzle 22 and the casting nozzle 21 is
As shown in FIG. 5, a backing 36 made of a refractory material such as poron nitride having good moldability may be interposed between the two.

Further, the tundish nozzle 22 and the casting nozzle 21 may be integrally formed in advance.

According to the present invention, it has become possible to supply molten metal with a small degree of superheating and small variations in the degree of superheating to the casting nozzle of a continuous thin plate casting machine at a small static pressure of the molten metal and a small linear velocity. In addition, a clean molten metal with few nonmetallic inclusions can be obtained at the same time. In particular, by adjusting the discharge speed of the molten metal from the tundish nozzle, a uniform and good solidified shell Jk and length can be achieved, the shape of the plate can be improved, and the occurrence of breakout can be prevented.

The tundish of the unmade J can be applied not only to twin-roll continuous casting machines that cast upward, but also to horizontal twin-roll continuous casting machines and horizontal and vertical twin-belt continuous casting machines.

[Brief explanation of the drawing]

Figure 1 shows the conventional twin-roll type thin plate! Fig. 2 is a conceptual diagram of a casting machine, Fig. 2 is a conceptual diagram showing a longitudinal section of an apparatus according to an embodiment of the present invention, Fig. 3 is a cross-sectional view of the apparatus of Fig. 2, and Fig. 4 is a conceptual diagram of a stopper. FIG. 5 is a conceptual partial cross-sectional view showing a high-frequency induction heating means of a tundish nozzle and a tundish nozzle, and FIG. In these figures, 13: Hot water receiving room 14: Hot water supply room 12.12': Weir] 3: Stirring means 18: Heating means 3o: Hot water level detection means 16: Pressurizing means Patent applicant Nisshin Steel Co., Ltd. Agent Patent attorney Masahiro Matsui (1 other person)

Claims (1)

[Claims] 1. A weir that divides the molten metal at the surface and communicates it at the bottom,
It is divided into a small volume receiving chamber that receives the molten metal from the ladle and a large volume hot water supply chamber that supplies the molten metal to the continuous casting equipment. A tan-in unit for continuous metal casting, characterized in that the molten metal supply port has a valve means and an upward nozzle reaching from the bottom of the hot water supply chamber almost to the surface of the hot water in the hot water supply chamber, and further includes a sealing lid and a pressurizing means for the hot water supply chamber. . 2. The tamper ash according to claim 1, characterized in that the nozzle is equipped with heating means. 3. A tundish according to claim 1, which is provided with a valve means at the molten metal supply port that can adjust the cross-sectional area of the molten metal supply port.