JPH03146B2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention relates to a break ring for continuous casting,
More specifically, the present invention relates to a break ring for continuous casting that is divided into at least two parts in the circumferential direction.

BACKGROUND ART FIG. 7 is a cross-sectional view of a portion of a horizontal continuous casting facility that forms the basis of the present invention and serves to explain the prior art. The tundish 1 is constructed by lining the inner periphery of an iron shell 2 with a refractory 3. A tundish nozzle 4 is formed in the lower part of the tundish 1. The tundish nozzle 4 includes a front nozzle 6, an intermediate nozzle 7, and a break ring 8 arranged in this order in the flow direction of the molten steel 5. A mold 9 having a horizontal axis is connected to the break ring 8 . When the molten steel 5 from the tundish 1 is introduced into the mold 9 to continuously cast slabs, the mold 9 is cooled. Therefore, the inner surface of the break ring 8 is in contact with the hot molten steel 5, and the outer surface is in contact with the cooled mold 9.
It will be used under extremely harsh conditions, such as contact with

Various materials have been proposed for the break ring 8 used under such harsh conditions, but boron nitride (BN), which has low thermal expansion and excellent machinability, is generally used. , boron nitride (Si ₃ N ₄ ), which has poor machinability but is superior in terms of strength and economy, is used. Further, as the cast shape of slabs becomes larger, break rings 8 divided into a plurality of parts are being put into practical use due to problems such as difficulty in manufacturing break rings 8 and distortion due to thermal expansion.

Problems to be Solved by the Invention It is easy to manufacture a large break ring 8 divided into multiple pieces using boron nitride or the like, but since boron nitride is difficult to sinter, it is necessary to pressurize it while heating it in a vacuum. Since it is necessary to manufacture by a so-called vacuum hot press method, the manufacturing cost is high, and there are economical problems as a material for the break ring 8, which is a consumable item. Therefore, if a split type is used with a hard material such as silicon nitride (Si ₃ N ₄ ), it is difficult to obtain mechanical precision of the split surfaces of the break ring 8, and molten steel leaks between the split surfaces and metal enters the gap. Bullion shavings are likely to occur. This phenomenon occurs not only at the dividing surface of the break ring 8 but also at the joint surface between the break ring 8 and the mold 9 and the joint surface between the intermediate nozzle 7 and the like.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a split-type break ring that prevents leakage of molten steel and metal droplets even when the material is made of a material with large thermal expansion and poor workability.

Means for Solving the Problems The present invention provides a continuous casting method characterized in that an absorbing layer with good workability and large hot deformability is provided on the dividing surface of a break ring divided in the circumferential direction. It's a brake ring. The absorption layer is made of boron nitride (BN) powder or a mixed powder of BN and one or more types of refractory materials such as alumina, zirconia, magnesia, spinel, silicon nitride, etc., and an inorganic material containing sodium phosphate, sodium silicate, and boric acid. They are either kneaded with a BN-based adhesive or pasted with inorganic fibers such as carbon fiber or alumina fiber using the above-mentioned BN-based paste. Since the absorption layer contains BN, it has extremely high lubricity and low hardness, so it has excellent precision machinability. Because it is kneaded with adhesive, it has the property of softening under pressure under hot conditions (500-1600℃).
It has the ability to absorb the thermal expansion of the break ring in hot conditions.

Effects According to the present invention, a layer with good workability and large hot deformability is provided on the split surface of the break ring, so the break ring can be manufactured using a material with large thermal expansion and poor workability. Even in such a case, good mechanical precision can be obtained by the absorption layer provided on the split surface, and the occurrence of leakage of molten steel and occurrence of bullion can be prevented.

Embodiment FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a sectional view taken along the section line - in FIG. 1. The break ring 8 has a generally rectangular tube shape, and is constructed by combining a plurality of divided pieces 24 (four in this embodiment) in the circumferential direction. The divided piece 24 consists of a divided piece main body 20 and an absorbent layer 22 formed on the divided surface 21. The divided piece bodies 20 are manufactured by, for example, heating a silicon powder molded body in a nitrogen atmosphere and sintering the silicon while nitriding it, and each part is coated with 100 parts by weight of boron nitride powder with a particle size of 10 μm or less on the outer periphery of each piece. liquid sodium silicate 40
Apply the paste with the weight part added to a thickness of 2 mm,
After drying, it is a silicon nitride (Si ₃ N ₄ ) ceramic that has been heat-treated at 500°C for 3 hours in a nitrogen atmosphere.
The material of the divided piece main body 20 may be alumina (Al ₂ O ₃ )-based, zirconia (ZrO ₂ )-based, or other ceramics in addition to the silicon nitride (Si ₃ N ₄ )-based ceramic described above. These silicon nitride-based, alumina-based, and zirconia-based semi-metals are relatively inexpensive and have excellent hot strength, but are hard and have poor workability.
The coefficient of thermal expansion is as large as 3 to 7.9×10 ^-6 /°C.

Mutual dividing surfaces 21 of the divided piece bodies 20 and the outer circumferential surface 23 of the break ring 8 that joins with the mold 9
An absorbing layer 22 having good workability and high deformability at high temperatures is formed. The absorption layer 22 has, for example, a chemical composition of 50% by weight of boron nitride (BN), 37% by weight of silicon oxide (SiO ₂ ), and 12% by weight of sodium oxide (Na ₂ O), and has a compressive strength of 133% by weight.
Kg/cm ² , and the adhesive strength with the divided main body 20 is 60 Kg/cm ² . Such an absorbing layer 22 is heated (500~
When the pressing force is 100 Kg/cm ² at 1600° C., the volumetric deformation rate (in the pressing direction) is 30 to 80%, and the deformability is large. Since the absorption layer 22 has a large boron nitride content,
Thermal expansion is small, e.g. thermal expansion coefficient 0.2~2×
10 ^-6 /℃. Furthermore, the hardness is 20 to 30 (Shorer)
and has good workability.

Instead of the absorbent layer 22 having the chemical composition described above, commercially available carbon cloth (plain weave 0.4 mm thick, graphitized) was pasted with a paste containing 100 parts by weight of boron nitride powder and 60 parts by weight of sodium silicate, and after drying, It may be packed in a carbon brace and heat-treated at 500° C. for 3 hours to obtain a predetermined size.

Such a break ring 8 is pressed and fixed to a mold 9, and the intermediate nozzle 7 and the break ring 8 are pressed and fixed to each other.

The conditions that this absorption layer 22 should meet are (1)
(2) Since the break ring is press-fitted into the mold, it absorbs the distortion of the break ring due to press-fitting. (3) It is molten steel corrosion resistant. (4) Casting begins. Because it comes into contact with high-temperature gas during the preheating of the tundish, it is oxidation resistant, (5) it has the ability to bond with break rings, and (6) it has good workability.

Boron nitride has excellent lubricity, oxidation resistance, and corrosion resistance for molten steel, and by using an inorganic adhesive, the absorption layer structure does not deteriorate due to oxidation even when heated to over 200℃ in an oxidizing atmosphere, making it possible to use carbon fiber. This is also advantageous in terms of preventing oxidation of the carbon fibers caused by the preheated exhaust gas of the tundish when the tundish is heated. The type of inorganic adhesive used and the mixing ratio of the inorganic adhesive and boron nitride are appropriately selected and adjusted depending on the workability and the type and amount of the refractory powder used. The above paste is applied to the break ring 8 or a carbon cloth is attached with the paste, and then dried and heat treated in a non-oxidizing atmosphere to thermally stabilize the absorbing layer 22. This heat treatment is useful for preventing dimensional changes (especially shrinkage of the absorbing layer 22) caused by heating by the preheated exhaust gas of the tundish 2 or heating by molten steel after the break ring 8 provided with the absorbing layer 22 is crimped and fixed to the mold 9. . This heat treatment temperature may be adjusted as appropriate depending on the type of inorganic adhesive used. The heat-treated break ring 8 with the absorption layer 22 is processed into a predetermined size and used.
Note that the thickness of the absorbing layer 22 may be appropriately set depending on the material and shape of the break ring 8.

In this way, an absorbent layer 22 with good workability and large deformability at high temperatures is provided on the dividing surface 21 of the divided piece main body 20.
Even if a material with large thermal expansion and poor workability is used for the split piece main body 20, the absorption layer 22 can be processed with high accuracy, preventing molten steel leakage at the split surface 21, metal cutting, etc. can be prevented from occurring. Furthermore, the break ring 8 is crimped and fixed to the mold 9, and during use, the break ring 8 is heated by the molten steel 5 and expands, and its outer periphery is restrained by the mold 9.Moreover, the mold 9 is water-cooled and has a small amount of expansion. Break ring 8 connected to mold 9
Stress is generated on the outer peripheral surface 23 and dividing surface 21 of the break ring 8 due to thermal expansion, but the dividing surface 21 of the break ring 8 and the outer peripheral surface 23 of the break ring 8 that joins with the mold 9 have deformability at high temperatures. Since the absorbing layer 22 is provided with a large
2 can be absorbed, the generated stress can be lowered, and breakage of the break ring 8 can be prevented.

According to the experimental results of the present inventors, the absorption layer 22
With the break ring 8 provided with this, slabs could be cast without any problems. The break ring 8 after casting has no corner chips or internal cracks, and the absorbing layer 22 absorbs the expansion of the break ring 8, preventing the break ring 8 from being damaged.

FIG. 3 is a sectional view of still another embodiment of the present invention, and FIG. 4 is a sectional view taken along the section line - in FIG. In this embodiment, the break ring 8 has a cylindrical shape, and is constructed by combining a plurality of (four in this embodiment) divided pieces 24a. This embodiment differs from the embodiments shown in FIGS. 1 and 2 in that only the shape of the cross section perpendicular to the axis is changed, and the other configurations are the same as those of the previous embodiment, with corresponding parts. shall have the same reference sign. Even in such embodiments, the present invention can be suitably implemented.

The present invention is particularly advantageously implemented in connection with a large break ring 8, and an embodiment relating to the large break ring 8 is shown in FIGS. 5 and 6. FIG. 5 is a sectional view of another embodiment of the present invention, and FIG. 6 is a sectional view taken along the section line - in FIG. As shown in FIG. 5, in this embodiment, the break ring 8 is constructed by combining a plurality of divided piece bodies 25 to 32 (8 in this embodiment), and the inner surface of the break ring 8 is The cross section is rectangular. The break ring 8 has three main body parts 25, 26, 27 forming one side wall.
and split piece main bodies 28, 29, 3 forming the other side wall.
0, a divided piece main body 31 forming an upper wall, and a divided main body 32 forming a lower wall. Split piece body 25-30
The mutual dividing planes 21 of are parallel to the inner surfaces 31a, 32a of the divided piece bodies 31, 32, and the divided piece bodies 2
The dividing surface 21a between 5 and 28 and the dividing piece main body 31 and the dividing surface 21b between the dividing piece bodies 27 and 30 and the dividing piece main body 32 are the dividing surfaces 25 to 27 and the dividing piece 28.
~30 parallel to the inner surface. Dividing planes 21, 21
The above-mentioned absorbent layer 22 is formed on a and 21b, and the divided piece bodies 25 to 32 are combined with each other by the absorbent layer 22 to form the break ring 8. Furthermore, the dividing surfaces 21, 21a, and 21b may be provided at arbitrary positions on the plane. An annular recess 35 to which the mold 9 is joined is formed in the outer peripheral surface 23 of the break ring 8, and an absorbent layer 22a is formed in this annular recess 35.

In the embodiment shown in FIGS. 1 and 2, the mutual dividing surfaces 21 of the divided piece bodies 20 and the mold 9
Although the absorbing layer 22 is formed on the outer circumferential surface 23 of the break ring 8 which is joined to the intermediate nozzle 7 and the break ring 8, a similar absorbing layer 22 may be formed on the joining surface between the intermediate nozzle 7 and the break ring 8. In this case, as the material for the intermediate nozzle 7,
For example, zirconia (ZrO ₂ ), alumina (Al ₂ O ₃ )
It is also possible to use a hard material with a high coefficient of thermal expansion, such as ceramics, which is hard and has poor workability. Further, the absorbing layer 22 may not be formed on the mutual dividing surfaces 21 to be joined, but may be formed on either one of the dividing surfaces 21. These matters are not limited to the embodiments shown in FIGS. 1 and 2, but also apply to the embodiments shown in FIGS. 3 to 6.

Although the above-mentioned embodiments are described in relation to the horizontal continuous casting method, the present invention is not limited to the horizontal continuous casting method, but can be suitably carried out in relation to the conventionally used vertical continuous casting method. be able to.

Effects As described above, according to the present invention, an absorbent layer with good workability and high deformability under hot conditions is provided on the split surface of the split piece main body, so it is possible to use a material with poor workability for the split piece main body. Even if the absorbing layer is processed with high precision, it is possible to prevent molten steel from leaking or leaking from metal.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the present invention, FIG. 2 is a sectional view taken from the cutting plane line - of FIG. 5 is a sectional view of another embodiment of the present invention; FIG. 6 is a sectional view taken from the cutting plane line of FIG. 5; FIG. 7 is a cross-sectional view that forms the basis of the present invention and illustrates the prior art. 7...Intermediate nozzle, 8...Break ring, 9
...Mold, 21, 21a, 21b...Divided surface, 22, 22a...Absorption layer.

Claims (1)

[Claims] 1. A break ring for continuous casting, characterized in that a layer with good workability and large hot deformability is provided on the dividing surface of the break ring divided in the circumferential direction.