JPH0428463A - Submerged nozzle for continuous casting - Google Patents

Abstract

PURPOSE:To execute stable continuous casting by arranging a gas pressure equalizing chamber to a submerged nozzle barrel part or discharging hole side wall part and also forming a submerged nozzle inner wall or discharging inner wall part adjacent to this pressure equalizing chamber with formed refractory including fine penetrating holes at random. CONSTITUTION:The submerged nozzle, which can concentrically inject gas having low activity of argon, etc., from the discharging hole 3 wall part and bottom part with deposit remarkably stuck and further surface in the pressure equalizing chamber 4 at lower part from molten metal surface in a mold, is provided. The gas pressure equalizing chamber 4 is arranged at the side wall part or to the bottom part of discharging hole 3 and the formed refractory 14 including the fine penetrating holes at random and made by adding natural or artificial combustible fiber in formed refractory raw material and burning up at the time of burning is applied to inside material from this pressure equalizing chamber 4. This nozzle is the gas blowing type submerging nozzle, which can concentrically blow a gas to the position substantially mostly needing prevention of sticking and deposition at the side wall part or the bottom part in the discharging hole 3. By this method, the sticking and the deposition of inclusion of alumina, etc., to the discharging hole in the submerged nozzle are not developed, and the stable continuous casting can be executed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a submerged nozzle for continuous casting.

[Prior Art] In continuous casting, it is common to use an immersion nozzle to prevent oxidation of molten steel, prevent scattering, and adjust the flow of molten steel in a mold.

Initially, fused silica was used as the material for the immersion nozzle, but it had a short service life.
Since the disadvantages in steel quality caused by imparting erosion resistance have become more important, alumina-graphite, which has excellent corrosion resistance and spalling resistance, has become mainstream at present.

When such an immersion nozzle is used to cast aluminum killed steel, aluminum-silicon killed steel, etc., alumina precipitates or granular metals adhere to and accumulate on the inner wall of the nozzle, which tends to block the nozzle and prevent the desired flow rate of molten steel from being obtained. It may disappear.

In order to prevent this, a gas blowing type immersion nozzle is used, which is characterized in that casting is performed while blowing out a gas with low activity such as argon gas from the inner wall of the nozzle.

That is, by ejecting a gas with low activity such as argon gas from the inner wall of the nozzle, a gas film is generated, which reduces the contact between the inner surface of the nozzle and the molten steel, and has the effect of preventing the adhesion and growth of alumina and the like.

This is the best known gas blowing type immersion nozzle.

(1) A gas pressure equalizing chamber provided only in a circular shape inside the straight body of the immersion nozzle (JP-A-56-102357, JP-A-5
No. 9-130662).

(2) There is a device (Japanese Unexamined Patent Publication No. 58-9750) in which the gas pressure equalization chamber is extended to the pillar part of the discharge port and the lower part of the discharge port, with the aim of ejecting gas also around the discharge port.

Furthermore, in the example shown in FIGS. 4 and 5, 0, 03 to 3 are integrally formed on the inner wall surface of the nozzle 1 with a rubber press, rather than the gas pressure equalizing chamber 4 provided on the 3° side wall and bottom of the discharge port. 0.5 ■
There is a method (Japanese Patent Application No. 1-49581) in which a plurality of communicating holes 6 of φ are provided to allow stable gas injection. In the figure, 2 is a nozzle hole, and 7 is a gas introduction path.

Furthermore, in the example shown in Fig. 6, natural or artificial combustible fibers are added to the molded refractory raw material around the discharge port below the gas pressure equalization chamber 4 provided only in a cylindrical shape in the straight body part, and are burned out during firing. By doing so, fine through-holes are created randomly,
This is a method of promoting the ejection of gas with low activity such as argon gas toward the inner surface of the discharge port (Utility Application No. 63-84487).
issue). 8 in the figure is a gas blowing metal fitting.

[Problems to be Solved by the Invention] However, these methods still do not have a sufficient effect of preventing the adhesion and accumulation of alumina, etc., and when the nozzle was investigated after casting, the results shown in Figures 7 (a) and (b) were found. As shown, the current situation is that alumina and the like are still attached and deposited on the inner surface of the straight body and around the discharge port. In the figure, 13 is a deposit.

The following two points can be considered as factors for the adhesion of alumina, etc. In other words, the area above the molten metal level in the mold inside the straight body is not filled with molten steel, but rather has a negative pressure due to the ejector effect, so argon gas etc. is preferentially ejected from the inner surface of the pressure equalizing chamber 4 above the molten metal level in the mold. This results in less ejection from the inner surface of the pressure equalizing chamber below the molten metal surface in the mold, where molten steel fills and alumina etc. tend to adhere and accumulate. In the case of the example shown in FIGS. 4 and 5, a hole of 0.03 to 0.5 mmφ is provided that communicates with the gas pressure equalization chamber 4 and the inner wall surface, so only the part where the hole is open is filled with argon gas. This is because gas and the like do not blow out, and alumina and the like progress from the parts where gas and the like do not blow out.

In addition, in the case of the type polymer shown in Fig. 6, which has fine through holes randomly all around the discharge port below the cylindrical pressure equalizing chamber 4, argon gas, etc. leaks to the outer surface of the immersion nozzle. The original amount cannot be effectively ejected from the side wall or bottom of the outlet 3, where prevention of adhesion and accumulation is required.

Furthermore, since this material has fine through-holes randomly contained therein, the apparent porosity tends to increase and the physical properties such as compressive strength tend to decrease slightly. For this reason, cracks are likely to occur in the pillar portion of the discharge port.

[Means for Solving the Problems] The present invention has been made to solve the above problems. The present invention provides a submerged nozzle that can eject a gas with low activity such as argon.

That is, as shown in FIGS. 1 to 3, a gas pressure equalization chamber 4 is provided up to the side wall or bottom of the discharge port 3, and the material inside the pressure equalization chamber 4 is made of natural or artificial combustible fibers. It is necessary to apply a molded refractory 14 in which fine through holes are randomly incorporated by adding it to the raw material and burning it out during firing, and also to prevent the original amount from adhering to the side wall or bottom of the discharge port 3. This is a gas blowing type immersion nozzle that can blow gas intensively from one area to another.

In the example shown in FIG. 1, a molded refractory material 14 in which minute through holes are randomly incorporated only in the inner material of a pressure equalizing chamber 4 provided in a cylindrical shape in the straight body of the nozzle body 1 is applied.

In the example shown in FIG. 2, the pressure equalizing chamber 4 is extended inside the column part, and a molded refractory material 14 in which minute through holes are randomly included is applied as the inner material.

In the example shown in FIG. 3, the pressure equalizing chamber 4 is extended to the bottom of the immersion nozzle, and a molded refractory 14 in which minute through holes are randomly incorporated is applied as the inner material.

By applying the molded refractory 14 having random through holes only in the material inside the pressure equalization chamber 4, the following advantages can be expected.

A. Advantage-1: Gas can be blown in intensively from the side wall or bottom of the discharge port 3 from inside the pressure equalization chamber 4, where prevention of adhesion and accumulation is originally required the most. That is, for example, in the case where the molded refractory 14 is provided with minute through holes randomly located around the discharge port below the cylindrical pressure equalizing chamber 4 shown in FIG. 6, argon gas etc. There were also cases where it leaked to the outside. However, according to the present invention,
Since the outside of the pressure equalization chamber 4 is made of a material that does not promote air permeability, argon gas and the like will not leak to the outer surface of the immersion nozzle.

B. Advantage-2 Furthermore, in the conventional method shown in Fig. 6, for example, the apparent porosity increases;
Since physical properties such as compressive strength tended to decrease, cracks and the like sometimes occurred on the side wall of the discharge port 3.

However, according to the present invention, since the outside of the pressure equalization chamber 4 is made of a type of material that does not promote conventional ventilation, there is almost no decrease in strength of the side wall of the discharge port 3, and troubles such as cracks occur. can be avoided.

[Example 1] As shown in Fig. 3, a gas pressure equalization chamber 4 is extended to the bottom through the side wall of the discharge port 3, and random through holes are incorporated only in the material inside the pressure equalization chamber 4 to improve ventilation. An example of an immersion nozzle to which a molded refractory material 14 is applied will be described.

The area that requires internal ventilation from the immersion nozzle pressure equalization chamber 4 (
In this example, A) is 240 cB'', and the required ejection amount of argon gas (B) is based on the knowledge obtained so far.
ION Q/win. Furthermore, from the spout surface,
Considering the average distance (C) 10.6+ui to pressure equalization chamber 4, the required ventilation rate is approximately 46 (0m3 cm)/(c112·l1in·(k) from the formula of BXC-4-A.
g/C112)) was obtained.

Therefore, the fibers added to this refractory were 1.0% by weight of artificial organic fibers with a thickness of ≦100 μm and a length of 2 to 3 m, taking into consideration prevention of molten steel intrusion.

The composition and physical properties of the organic fiber additive product are shown in Table 1 in comparison with the additive-free product.

Using a submerged nozzle with the structure shown in Figure 3, 250 tons/heat of molten steel was continuously poured for 10 minutes while spouting argon gas.
A total of 2500 tons of molten steel was cast for 500 minutes. As a result, it was possible to cast with almost no adhesion or deposition of alumina or the like.

Table 1 Comparison of composition and physical properties of example materials and conventional products Umbrella 1... (CIl13・CIl/c!12・1-k
g102) On the other hand, by preventing alumina deposition at the discharge hole of the immersion nozzle, the discharge hole angle is always maintained constant even at the end of casting, which stabilizes the surface properties of the slab and prevents the adhering alumina from forming during casting. It was possible to prevent the steel from flaking off, getting caught up in the molten steel, and becoming inclusions in the steel, thereby improving the quality of the steel material. In addition, unlike in the past, the cross-sectional area of the discharge hole does not decrease over time, so the set casting speed can be maintained throughout, contributing to stabilizing the process time of the entire factory.

[Effects of the Invention] As described above, according to the present invention, inclusions such as alumina do not adhere or accumulate in the immersion nozzle discharge hole during casting, and
This has the remarkable effect of being able to perform stable continuous casting over a long period of time.

[Brief explanation of the drawing]

Figure 1 shows one of the present invention, in which a molded refractory 14 in which fine through holes are randomly incorporated only in the inner material of the pressure equalizing chamber 4 provided in a cylindrical shape in the straight body of the immersion nozzle body 1 is applied. Figure 2 is a diagram in which, in the present invention, the pressure equalizing chamber 4 is extended also inside the column part, and a molded refractory 14 in which fine through holes are randomly included as the inner material is applied. Fig. 3 is a diagram in which the pressure equalizing chamber 4 is extended to the bottom of the immersion nozzle, and a molded refractory 14 in which minute through holes are randomly incorporated is applied as the inner material. In the conventional gas blowing type immersion nozzle, the 0 port is made of refractory material inside the pressure equalization chamber 4, and has multiple communication holes of 0.03 to 0.511 IIaφ integrally molded with a rubber press. An illustration of an example of material application, Figure 5, is
FIG. 3 is a diagram of another example of a conventional gas blowing submerged nozzle. Figure 6 shows that among the conventional gas blowing type submerged nozzles,
Figure 7 is a diagram of an example of a conventional type immersion nozzle in which minute through holes are randomly built around the discharge port 3 below the pressure equalization chamber 4 provided in a cylindrical shape inside the straight body. , A diagram showing the state of alumina adhesion and accumulation on the inner surface of the straight body and around the discharge port in a conventional gas blowing type submerged nozzle. 1: Nozzle body, 2: Nozzle hole, 3: Discharge port, 4:
Gas pressure equalization chamber, 5: Ventilation porous section, 6: Communication hole, 7:
Gas introduction path, 8: Gas blowing fitting, 9: Upper gas blowing fitting, 10: Gas introduction passage, 13: Deposits, 14: Molded refractory. Chest diagram diagram diagram diagram diagram (a) (b) diagram diagram diagram diagram diagram (a) (b)

Claims (1)

[Claims] In a gas blowing submerged nozzle for continuous casting of molten steel, a gas pressure equalizing chamber is provided in the straight body of the submerged nozzle or the side wall of the discharge port, and the inner wall of the submerged nozzle or the inner wall of the discharge port adjacent to the gas pressure equalizing chamber is 1. An immersion nozzle for continuous casting, characterized in that the nozzle is formed of a molded refractory material having random through-holes therein.