JPH01104451A - Brake ring for continuously casting metal - Google Patents

Abstract

PURPOSE:To absorb deformation, etc., of a ceramic caused by heat shock with metallic layer and to reduce crack by having the ceramic part and the metal part in a brake ring and making construction joining the ceramic part and the metal part of the brake ring. CONSTITUTION:An inserted part 5 to a mold of the brake ring is made of plural-layer construction of the ceramic and the metal. The ceramic is made of zirconia ceramic partially stabilized by MgO and the metal is made of copper by casting to join the both material. The casting to join is executed by charging the copper and the ceramic in a crucible and melting the copper at the prescribed temp. and cooled as they are. After that, unnecessary part of the copper is cut off to machine to the prescribed size. By this method, the service life if extended and machining can be facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a break ring used in the continuous casting of industrial metals.

BACKGROUND OF THE INVENTION Continuous casting methods, in which a tundish is directly connected to a mold and a slab is pulled out horizontally or vertically, are being put into practical use as methods for continuous metal casting. FIG. 4 shows an outline of horizontal continuous casting in which slabs are drawn horizontally. In this horizontal continuous casting, a mold 6 is connected to a tundish l holding a molten metal 2 through a nozzle 3 or a break ring 4. Then, the molten metal in the tundish flows into the mold, and the slab 7
be extracted as.

The break ring used to connect the tundish and mold in continuous casting is usually made of ceramic to prevent reaction or fusion with molten metal. However, since one side is in contact with molten metal and the other side is in contact with a water-cooled mold, thermal shock resistance is required, and it is also necessary to withstand corrosion by molten metal. When cracks due to thermal shock or wear due to erosion occur, molten steel flows into the cracks and solidifies, making it impossible to pull out the slab.

Furthermore, break rings require highly precise machining.

If the fit between the mold and the brake ring is loose, molten metal will flow into the gap between the mold and the break ring, which will also cause casting to stop.

Because the mold deforms due to the thermal history caused by casting, the break ring is processed to match the actual mold each time.

For this reason, it is necessary that the break ring be easily machined.

In this way, break rings have thermal shock resistance, corrosion resistance,
Furthermore, workability etc. are required. For these reasons, conventional break rings are MN, BN, and 51311m.

Ceramics such as ZrO2,5i (4) or mixtures thereof are used. However, in general, when ceramics are manufactured densely, their hardness increases and corrosion resistance improves, but thermal shock resistance decreases and processing becomes difficult. In addition, increasing the porosity improves thermal shock resistance and workability, but there are problems such as a decrease in erosion resistance.

There have been several proposals in the past for this kind of problem.
For example, Japanese Patent Publication No. 112-14507, Japanese Patent Publication No. 82-
14508 and Japanese Patent Publication No. 82-14509 contain Cr2O3.

A composition based on TiO2 and CaO and a method for producing the same have been proposed. Furthermore, Japanese Utility Model Application Publication No. 58-147659 proposes a method in which a break ring is divided in the circumferential direction and is fixed within a cylindrical band by shrink fitting or the like.

However, it cannot be said that these methods have sufficiently solved the problem.Also, there are materials such as BN which are soft and have good workability, but in this case, the corrosion by molten metal is large and the lifespan is short.

In addition, conventional break rings cannot be machined with sufficient accuracy, or gaps are created between the break ring and the copper mold due to thermal deformation of the mold or break ring during casting.

For this reason, the break ring had to be attached by inserting it into the mold as shown in Figure 4. Then, a level difference occurs between the break ring and the mold, and due to the level difference, a mark called a cold shut mark or the like is formed on the continuous casting slab using the break ring, and this becomes a surface defect of the slab.

These surface defects in the slab require maintenance such as scraping, which increases maintenance costs and reduces yield. Therefore, it is important to reduce defects on the slab surface caused by these cold shut marks.

Problems to be Solved by the Invention As described above, break rings are required to have thermal shock resistance, corrosion resistance, and good workability, but there is currently no one that fully satisfies these characteristics. We provide a break ring that maintains thermal shock resistance and workability without sacrificing corrosion resistance, and also eliminates the level difference between the mold and break ring on the inside of the mold, reducing defects on the slab surface caused by cold shut marks. It provides a ring.

Means for Solving the Problems The gist of the present invention is to provide a break ring used for continuous metal casting, which has a ceramic part and a metal part,
The break ring for continuous casting of metal is characterized in that the part in contact with the mold or the surrounding area including the part in contact with the mold is made of metal, and the ceramic part and the metal part are integrally joined.

The break ring has a ceramic part and a metal part, and the ceramic part and the metal part are joined to each other, so that the metal layer absorbs deformation caused by thermal shock of the ceramic and prevents cracking. In addition to reducing the cost, the fitting part with the mold can be easily processed by processing the metal layer.

The ceramic part is in contact with the molten metal and its surroundings, and contains Si3N4, ZrO2, MN, SiC, Z
rB2°MgO, AQ, 03. Cab, TiB2, T
A mixture or compound of one or more of metal oxides, carbides, nitrides, borides, etc., such as iN, is preferred because of its high resistance to molten metal penetration, and it is also possible to mix a small amount of metal or C, etc. be.

The metal part should be made of copper or copper alloy, which is ductile and easy to work with, but should not have a melting point of 4, such as solder alloy.
Metals with temperatures below 00°C are unsuitable because they may melt during use.

Also, metal does not necessarily need to be bonded to the entire ceramic periphery, but only at the insertion part into the mold or around the insertion part, and the use of metal in the parts that come into contact with molten metal prevents fusion with the molten metal. Therefore, cooling is limited to areas where sufficient cooling occurs, that is, within or near the mold.

Ceramic and metal joining methods include casting, which involves heating and melting copper etc. and pouring it around the ceramic, fitting metal into the outer periphery of the ceramic and joining by hot pressing, and brazing, which uses an appropriate intermediate material to join. ``If the ceramic bonding surface is cast-in or hot-press bonded, there is no particular problem with roughness, and this aspect also makes processing easier.

In addition, if a break ring with metal bonded as in this example is used, processing accuracy will be improved, and since the ceramic and metal parts are bonded, gaps may be formed between the ceramic part and the metal joint due to thermal deformation during casting. As shown in FIG. 3, the break ring and mold can be connected without any difference in level. This is effective in reducing surface defects in the slab.

The connection portion between the metal of the break ring and the mold should be located beyond the area where the metal starts solidifying.

By doing this, if a metal with high thermal conductivity such as copper is used, although it is not particularly bonded, it will be possible to
Even when casting high-melting point metals exceeding 350°C, the temperature of the connection part is 350°C.
℃ or less, and no voids will be formed due to thermal deformation.
In addition, the cast metal has already started to solidify in this area, and if there is a small gap, the slab will not be restrained by insertion.

Examples Table 1 shows an overview of the examples. Example No. 1.2 is a comparative example, and Example Nos. 3, 4, and 5 are examples of the present invention. R-made metal is stainless steel equivalent to 5O83G4, tundish capacity 120 kg, tundish internal molten metal temperature 148
A water-cooled copper mold with an inner diameter of 1O layer was used. The casting method has a withdrawal amount of 30 to 40 per stroke.
The casting was carried out by horizontal continuous casting in which horizontal drawing was performed intermittently at a rate of 80 to 100 times/min. Average slab drawing speed 3.5
m/min.

In Example No. 1, the casting apparatus shown in FIG. 4 was used, and the break ring was made of zirconia ceramic. As a result, the casting was stopped due to the slab being restricted after approximately 13 kg of casting. After casting, the part of the brake ring that was fitted into the mold was damaged, and metal protruded out of the mold.This protruding metal restrained the casting, causing the casting to stop.Also, when the break ring was manufactured, the zirconia ceramic was extremely hard. Grinding was done using a diamond tool, which was costly and time consuming.

Implementation No. 2 was cast using a BN break ring. Since BN is soft, there were no problems when processing it.

However, the work was stopped after casting about 32 kg due to slab restriction. The break ring after casting was damaged by abrasion, and sufficient casting could not be achieved due to the low corrosion resistance of BH.

Implementation No. 3 is an example of the present invention, in which a break ring having a multilayer structure of ceramic and metal was used for the mold-fitting part of the break ring, as shown in FIG. Ceramic is not implemented
Similar to o and l, zirconia ceramic is partially stabilized with MgO, and the metal is copper cast and joined. For casting joining, copper and ceramic were placed in a crucible, the copper was melted at 1250°C, and then cooled. After that, unnecessary parts of the torso were cut away and processed to the specified dimensions.

In this example, about 120 kg could be cast without any problem, and no damage was observed in the break ring after casting.

The break ring could also be easily machined using a regular metal cutting tool.

Embodiment No. 4 is also an example of the present invention, and as shown in FIG. 2, the mold fitting portion is tapered so that the outer peripheral metal of the break ring can be made thicker. A mixture ceramic of 30% Si3!14, 50% BN, M, 03, etc. was used, and a pattern was brazed on the outside. As in Example No. 3, approximately 120 kg could be cast, and the break ring was easy to process.

Implementation No. 5 is also an example of the present invention, the outline of which is shown in FIG. 3, with 60% BN and 30% ZrB2. In addition, a ceramic mixed and fired with ZrO2 is used, and the outside is heated at 950℃ for 1 hour.
Copper was hot isostatically pressed in an Ar atmosphere of 0,000 atm. Approximately 120 kg could be cast without any problems, and the surface defects of the slabs were significantly less than those in Examples 1 to 4. Furthermore, the break ring was easy to process.

(Leaving space below) Table 1 - Effects of the Invention As shown in the examples, according to the present invention, the life of a break ring for continuous metal casting can be extended, and its processing becomes easier. It is also possible to reduce defects on the surface of the cast slab, which has a great effect on industry.

[Brief explanation of the drawing]

FIG. 1.2.3 is a sectional view showing an outline of horizontal continuous casting of metal according to an example of the present invention. FIG. 4 is a sectional view showing an outline of horizontal continuous casting of metal in the prior art. 1. Fist tongue dish, 2. Molten metal, 3. ΦΦ nozzle, 4. φ. Break ring (ceramic), 5.
・Break ring (metal part), 6...mold, 7-...
Solidified metal (slab).

Claims (1)

[Claims] A break ring used for continuous metal casting has a ceramic part and a metal part, and the part in contact with the mold or the surrounding area including the part in contact with the mold is made of metal, and the ceramic part and the metal part are made of metal. A break ring for continuous metal casting, characterized in that these are integrally joined.