JP2727266B2 - Nozzle for continuous casting for steelmaking - Google Patents

Description

BACKGROUND OF THE INVENTION [0001] BACKGROUND OF THE INVENTION This invention is a Oite <br/> ladle in the continuous casting of steel, long nozzle which is used between the mold from a tundish and tundish More particularly, the present invention relates to a continuous casting nozzle for steelmaking which prevents non-metallic inclusions from adhering and accumulating in the nozzle hole during casting, thereby narrowing or closing the nozzle hole. 2. Description of the Related Art Conventionally, in the conventional continuous casting method of steel, molten metal is sequentially transferred from a ladle to a tundish and from a tundish to a mold and cast. During this time, a long nozzle and an immersion nozzle are used to cover and connect the molten metal to prevent oxidation of the molten metal. As the pouring time of these nozzles increases, non-metallic inclusions intervening in the molten metal gradually adhere to the inner surface of the hole, the deposition gradually progresses, the inside of the nozzle hole is narrowed, and the casting speed is reduced. Eventually, normal casting cannot be performed, and operation becomes impossible. Even if the casting operation can be managed, even if the immersion nozzle has two or more discharge ports, the uniform flow rate can be maintained due to the difference in the amount of non-metallic inclusions deposited and deposited on each discharge hole. Instead, a drift occurs and the flow in the mold is disturbed, and the uniformity of the solidified shell formed by the sidewalls in the mold is lacking, and the non-metallic inclusions deposited and separated by the flow of the molten metal flow out. It becomes entangled in the billet and appears as sand flaws, which adversely affects the operation, quality and yield, and develops into serious problems. [0003] In order to solve these problems, a hole is formed in the tip of the tundish stopper or the inside of the hole of the nozzle body, or a slit is formed inside the nozzle body. Inert gas is blown through the gas to suppress the adhesion and deposition by the effect of the gas, and the structure is improved. Also, in terms of material, conventional high alumina-graphite material to zirconia-graphite material or calcia material is used.
Improvement measures such as the use of zirconia-based materials, such as partial use of materials that can maintain high corrosion resistance and reduce adhesion, have been adopted on the inner wall surface of the nozzle hole to adopt a multi-layer structure. At present, it is not enough to solve the current problems. By adopting this method, the bubbling phenomenon sometimes occurs in the mold due to the suction gas depending on the quality of the operation, and the level of the molten metal is changed abnormally, causing problems in operation and quality. What you have to do
Work for this introduction is required, equipment costs and labor costs are increased, and production costs such as gas costs are increased. Therefore, there is a strong demand for solving these problems. [0004] In view of the above situation, the present invention provides safe operation and quality without nonmetallic inclusions and deposits on the inner wall surface of the nozzle hole even when the operation is continuously performed for a long time. Has a high reactivity with non-metallic inclusions to produce a continuous casting nozzle that does not incur high production costs.
The present invention has been completed by paying attention to the fact that the main component of the reaction is a material having a low melting point. In the present invention, since the main component of the deposit is Al ₂ O ₃ (alumina), a CaO— SiO ₂ —B ₂ O ₃ based refractory material having high reactivity with Al ₂ O ₃ (alumina) is continuously used. It is used as a part of a casting nozzle material. That is, at least the discharge hole portion on the inner wall of the nozzle hole is made of a CaO—SiO ₂ —B ₂ O ₃ refractory material of CaO: S
The content of iO ₂ is in a molar ratio of _2: 1~3: _B 2 in 1 material
O _3, consists of 1 to 5 wt%, CaO, _SiO 2, B
_By using a refractory material in which the total amount of the three components of ₂ O ₃ is 95% by weight or more as a graphite material mixed with 5 to 50% by weight, Al ₂ O ₃ ( (Alumina), and found out a nozzle material that is effective as a low-melt material to flow out as a low-melt material to suppress adhesion and deposition on the inner wall of the nozzle hole. (Reasons for _{limitation) CaO-SiO 2 -B 2 O} 3 based refractory materials CaO: S
The reason that the content of iO ₂ was 2: 1 to 3: 1 in molar ratio. When the molar ratio of CaO: SiO ₂ is 2: 1 or less, fire resistance is degraded, and there is a problem in corrosion resistance. When the molar ratio is 3: 1 or more, free CaO, so-called free lime, is contained. This is because a serious problem arises due to hydration reaction on storage. 2CaO The _B 2 _{O 3} (boric acid) is desired CaO-SiO ₂ based materials which contain _B 2 _{O 3} to the content was 1 to 5% by weight of a main component at 725 ° C. in heating and cooling processes and SiO ₂ crystal can be easily converted from β type to γ
Transforms into a mold and becomes γ2CaO-SiO ₂ crystal, about 12%
Is contained in order to suppress this transition phenomenon, which causes a powdering phenomenon and collapses with an increase in the volume of the alloy. When the content is less than 1% by weight , the effect is small and unstable. If the content is more than 5% by weight , a problem occurs that heat resistance is not reduced. _CaO-SiO 2 _-B 2 _{O 3} system CaO in the refractory material, S
The three components of iO ₂ and B ₂ O ₃ are essential and the total amount is 95% by weight .
When the content of the refractory material is 5% by weight or less with respect to the addition of 5 to 50% by weight, the reaction amount is small, and
Little improvement effect of sedimentation phenomenon. b When the content is 50% by weight or more, the corrosion resistance is reduced and the durability is reduced. Carbon and Graphite Material 10 to 35% by Weight The purpose of addition of carbon and graphite material is to improve (a) corrosion resistance and (b) heat spalling resistance. a When the content is 10% by weight or less, corrosion resistance and heat spalling resistance are obtained. b When the content is 35% by weight or more, the strength of the nozzle itself decreases. If the ratio is out of this range, the required characteristics in use cannot be sufficiently satisfied. It is also effective to add a carbide or nitride material other than these raw materials in order to prevent oxidation of the carbon material by sintering. [Table 1] [Table 3] [0007] in the raw materials used in EXAMPLE, CaO - SiO ₂ -
Table 1 chemical composition values of the material to produce a B ₂ O ₃ refractory material and CaO-ZrO ₂ refractory material, also shown in Table 2. blending ratio of the raw material. Table 3 shows the chemical component values of the raw materials used in the examples. In the raw materials shown in Table 3, CaO-SiO ₂ - B
₂ O ₃ refractory material and CaO - preparation of ZrO ₂ based refractory material, the raw materials shown in Table 1, respectively pulverized into a particle size of less than 74Myu, nonhydrogen resins by wet pan performs blended at ratios shown in Table 2 6m after mixing with a briquette machine
After granulating to a size of mx 6 mm x 8 mm, drying, melting this using an electric furnace, tilting the furnace and transferring to a ladle,
After cooling, produce this test material and use it. The refractory materials within the scope of the present invention are shown in Table 2 in the Examples.
As shown in the figure, CaO, SiO ₂ , B ₂ O ₃ having high reactivity with alumina which is a main component of nonmetallic inclusions in molten steel
It has to form a three-component as an essential component. And Ca
The molar ratio of O : SiO ₂ is 2: 1 to 3: 1 and B ₂
By limiting the content to O ₃ 1 to 5%, heat resistance, digestion resistance and stability of the crystal form are excellent, and even when heating and cooling are repeated, 2CaO · SiO ₂ crystal and the like have no crystal form transition and γ 2CaO · reactivity at the interface between the alumina has sufficiently provided with characteristics as such refractory material different crystal body at all generation is not observed in the SiO ₂ crystals such also has the function of a very high like. The _CaO-SiO 2 _-B 2 O used in the present invention
_{Since the 3} series refractory material is produced by cooling after being melted electrically, a homogeneous material can be obtained and has high crystallinity, the stability of the material is high, and the quality as a refractory material and Materials with high quality stability can be obtained. Table 4 shows the results of the substitution test of the immersion nozzle material of the high alumina-graphite material with the fused alumina using the C material in the above-mentioned prototype materials, and Table 5 shows that the C material was 25% by weight . added material shows the test results for the addition amount of the graphite material as a reference. Table 6 shows that CaO—SiO ₂ —B ₂ O
Comparison and conventional materials of component value difference of ₃ refractory material, and shows the comparative test results of the comparative material. The test materials were manufactured by mixing the materials based on the mixing ratios shown in Tables 4, 5, and 6,
After heating to 30 ° C , kneading, standing in a room, cooling, hogging, press-molding with a rubber press at a pressure of 1000 kg / cm ² , in a tunnel kiln at a maximum temperature of 1350 ° C, in a coke breeze After burying and firing , machine processing is performed to produce an immersion nozzle having a predetermined shape. The erosion test and the adhesion test were carried out from the immersion nozzle material produced by 40 × 40 × 25.
A 0 mm sample was cut out and placed in a molten metal of a high frequency induction furnace.
The immersion is performed while rotating at a rate of 1 minute, and the holding is performed for 120 minutes. The erosion test was carried out under conditions in which 3% of Al was added to the molten metal (steel) and the temperature of the molten metal was controlled at 1580 ° C. ± 10. Incidentally shows the practical test results using an actual in Table 7. Stable _CaO-SiO 2 _-B 2 _{O 3} refractory used in the present invention as shown in practical tests results of the series of basic tests and actual
Depending on the material , the adhesion of nonmetallic inclusions is very small and good. In particular, as shown in the results of practical tests using actual machines, the comparative product in Table 6 as a conventional product and Table 6 as the present invention were used as immersion nozzles of the same tundish, respectively. There are irregularities, 1
The present invention product is 1 to 3 mm for 2 to 20 mm,
1.5 to 3.5 mm, which is very small, the surface is smooth, and non-metallic inclusions adhered to the surface are not separated and run off. Also, there is no drift due to the accumulation of the attached matter, and it is large in terms of work, steel quality, yield, etc. An improvement effect is obtained. In Table 2, (hydration resistance) The electric melt was pulverized and adjusted to 3 to 2 mm to prepare a sample. This sample is placed in water, and after boiling time, dried in a thermostat at about 105 ° C. for 10 hours. a. Weight gain (digestion) b. Powdering ratio (amount reduced to 2 mm or less (weight percent)) (Heat resistance) The state after cooling in a holding furnace at a predetermined temperature for 3 hours is shown. A sample is cut out from the melt to a size of 30 × 30 × 30 mm and made. (Functional test) The molten material is pulverized, and 3 to 1 mm 45%, 1 to 0.1 mm
After blending with 15% and 0.1% or less of 40%, adding and kneading 5% of the resin, press-molding at a pressure of 1000 kg / cm ² , and baking at 1550 ° C. to obtain a sample. Sample size 5
Alumina with a particle size of 44 μm or less is added to 0 × 50 × 20 mm.
This figure shows the state after coating at a thickness of 2 mm, holding at 1550 ° C. for 30 minutes and cooling in the furnace. Table 7 shows the results of the comparison test using the actual machine. Usage conditions 1. 1. Steel type, low carbon aluminum killed steel Slabs of size 220 × 1,150-1,500 mm Material Table 6 Comparative Example Table 6 present invention product is ready to use [Table 1] [Table 2] [Table 3] [Table 4] [Table 5] [Table 6] [Table 7]

Claims (1)

(57) Claims: _CaO, SiO _2, B ₂ and 3 components of _{O 3} was essential components _CaO-SiO 2 _-B 2 _{O 3} system Ca in refractory material
Refractory material 95 having a molar ratio of O: SiO ₂ of 2: 1 to 3: 1
99% by _weight, containing ₂ O 3 1 to 5 wt% B, Ca
_O, and SiO _2, B ₂ 5~50 wt% of the refractory material that the total amount of 3 component contains more than 95 wt.% Of _{O 3} and 10 to 35 weight percent carbon and graphitic material and the remainder of oxide refractory materials A nozzle for continuous casting for steelmaking, comprising: kneading and molding after adding an organic binder;