KR20030000565A - Materials for Slag Cutting Devices in Steelmaking Process - Google Patents

Abstract

PURPOSE: A composition of slag cutting devices is provided which reduces manufacturing cost and substantially reduces the amount of slag mixing during tapping of a converter and a ladle by preventing slag mixing in steelmaking smelting and manufacturing slag darts and slag check balls using inexpensive raw materials. CONSTITUTION: The composition of slag cutting devices for preventing slag mixing in steelmaking smelting comprises an inner material which is prepared by uniformly mixing a refractory material having a melting point of 1250 deg.C or more that is in the low melting point range in steelmaking process with steel material having specific gravity of 7 or more and particle size of 5 mm or less so that specific gravity of the mixture becomes an ordinary manufacturing level of 3.0 to 5.5; and an outer material comprising an adiabatic and erosion resistant MgO-Al2O3-C based material durable to a high temperature of 1700 deg.C or more, wherein thickness of an object on which the outer material is coated is constructed in such a way that temperature of the inner part of check balls is maintained to less than 1250 deg.C by adiabatic effect even at 1650 deg.C that is an ordinary temperature of the steelmaking process, wherein the outer material comprises 40 to 70 wt.% of MgO, 10 to 30 wt.% of Al2O3 and 3 to 25 wt.% of C so that the material is equipped with adiabatic function as well as slag erosion resistance.

Description

Composition of slag cutting device for preventing slag mixing of steelmaking refinery {Materials for Slag Cutting Devices in Steelmaking Process}

The present invention relates to a composition of various slag cutting mechanisms used for preventing slag incorporation during steelmaking refining process, and more particularly, the slag of the upper layer at the end of the tapping process during the tapping of the molten metal after the converter and ladle refining. In order to prevent slag leakage, the composition of various slag cutting devices put into the converter and ladle is coated with a coating material having excellent insulation and erosion resistance on the surface of conventional general refractory materials, and the inside is generally used in steel refining processes. By using the various by-products generated, the present invention relates to a composition of a slag cutting mechanism for steelmaking refining slag incorporation that does not melt even in the hot tapping process without using the by-products having low melting point.

In general, the steelmaking process consists of preliminary refining, converter refining, and secondary refining. The molten steel obtained through this process is manufactured through a continuous casting process to produce casts desired by demand.

In the steelmaking process, there is always a slag layer on top of the converter and the molten steel in the ladle.

Referring to Figure 1, Figure 1 is a cross-sectional view showing a typical converter tapping operation, the molten steel that has undergone the above refining process is subjected to a secondary refining process to satisfy the final quality standards, wherein the secondary refining in the converter (1) In order to implement the molten steel 4 is tapping on the water-receiving ladle (6), which is a transportation and refining vessel.

In the process of tapping, the free surface of molten steel and slag (5) is formed due to the vortex phenomenon caused by the rotation of the earth, and the vortex phenomenon occurs, and the slag (5) having a small specific gravity on the upper part of the molten steel is generated by the vortex phenomenon. It flows out into the tapping ladle 6 through the pouring port 2. This phenomenon occurs not only in the steel ladle 6 in the steelmaking process, but also in all processes including tapping in various non-ferrous manufacturing and electric furnace operations.

Various methods have been attempted to suppress the mixing process of slag (5) or low specific gravity upper material due to the vortices inevitably generated in the series of tapping process, the molten steel (4) in the middle of tapping during the steelmaking process And the slag (5) has a specific gravity (3.0 ~ 5.5) of medium, and the inside has a spherical slag ball composed of a strong refractory oxide (refractory and slag) and iron for adjusting the specific gravity, in addition to inserting the iron core into the conical shape In order to adjust the specific gravity, the high specific gravity chromium oxide and iron oxide are mixed in an appropriate ratio, and the slag dart which floats between the slag 5 and the molten steel when it is introduced into the furnace, and closes the hot water outlet 2 at the appropriate time. There is. The slag cutting devices have a series of steelmaking processes consisting of exclusion, charging, blowing, and tapping as one cycle to prevent slag 5 from leaking by inserting a slag cutting mechanism at the end of tapping every cycle.

In general, the basic properties of the cutting mechanism introduced to prevent the incorporation of the slag 5 should satisfy the following conditions.

1) Specific gravity should be less than molten steel (about 7.0) and greater than slag (2.5 ~ 3.0).

2) Withstand high temperature molten steel and slag without melting

The refractory material must have a high melting point. (Above 1700 ℃)

3) High strength and easy to carry or handle

Thermal shock must be strong because it must be injected into the high temperature zone.

4) Because it is in contact with high temperature slag, the fireproof material itself

Must be excellent

On the other hand, looking at the technique for preventing the conventional slag outflow,

In Korean Patent Application No. 2001-12597, there is a slag check ball coated with a powder composed of MgO-CaO-SiO2 oxide on the surface of slag check ball for the purpose of suppressing internal smoke and erosion at the end of tapping. After the MgO component is eluted from the coating material, the main component is to coat the inside of the converter outlet 2 to suppress the erosion of the apparatus. (See FIG. 2 (a).) The slag check ball is spherical in shape. It is composed of refractory and steel, and the specific gravity is adjusted to 4 ~ 6 by adjusting the mixing ratio of steel, and refractory should use high melting point refractory above 1700 ℃.

In addition, Korean Patent Application No. 1999-4406 relates to slag darts for preventing slag outflow and discharging only molten metal at the end of the converter tapping, and the residual water is present after closing the tap opening by making a groove in the slag dart. In order to achieve the above object, the melting point of the refractory material is 1700 ° C because the dart head is in contact with slag of 1700 ° C. or more. It must endure above ℃, and in order to meet the proper specific gravity, it is necessary to mix a large amount of chromium oxide or iron oxide, which is a large specific gravity oxide. In addition, there is utility model registration No. 1990-2443 (see Fig. 2 (c)), and the above-described fire-resistant material of the prior art must use a high melting point refractory of 1700 ° C because it is in direct contact with hot slag during tapping. . On the other hand, in order to adjust the specific gravity, the check ball should be placed inside the steel material in the center, and darts have limitations such as having to mix oxides having high specific gravity (Cr 2 O 3, Fe 2 O 3, etc.).

The common construction of the above-described prior art basically uses a refractory having a high melting point because it must withstand high temperatures, and must be present between a low specific gravity slag and a high specific gravity molten steel or a high specific gravity chromium. Iron oxide is used. Accordingly, the present invention has been made to solve the general constraints of the prior art as described above, and is not subject to the conditions of 2) and 4) of the slag cutting mechanism introduced to prevent slag mixing until now. The inside is to be made of a low melting point oxide, the outer coating layer is coated with a material having excellent thermal insulation on the inner surface to enable the use of secondary low melting point by-products such as various slag and dust generated in the steelmaking process An object of the present invention is to provide a composition of a slag cutting device for preventing slag mixing.

1 is a sectional view of the main part of the converter during a general tapping operation.

Figure 2 is a cross-sectional view showing a conventional slag outflow prevention method.

3 is a cross-sectional view showing a slag dart according to the present invention.

4 is a cross-sectional view showing a test apparatus for use of the embodiment.

5 is a graph showing the temperature measurement results of the prior art and the present invention of the embodiment.

Explanation of symbols on the main parts of the drawings

1: converter 2: tap

3: slag dart 4: molten steel

5: slag 6: water ladle

In order to achieve the above object of the present invention, when manufacturing a slag cutting device for preventing slag mixing in steelmaking refining process, the internal material and the external material are distinguished, but the internal material is steelmaking by-product and specific gravity having a melting point of 1250 ° C. or more, which is a low melting point area in the steelmaking process. 7 or more, steel particles with a particle size of 5mm or less are mixed and manufactured uniformly so that the total specific gravity is 3.0 to 5.5, which is the normal manufacturing level, and the outer material is heat-insulating and erosion-resistant MgO-Al2O3- resistant even at high temperature of 1700 ° C or higher. It is composed of C system, but MgO concentration is 40 ~ 70% by weight ratio, Al2O3 concentration is 10-30%, C concentration is 3-25%, and the thickness of the material composed of the above-mentioned external coating material is the normal temperature of steelmaking process. It is achieved by configuring the inside of the checkball to be less than 1250 ° C even at 1650 ° C due to the effect of thermal insulation (see Figure 3).

Hereinafter, the reason for limitation of the component according to the present invention will be described in detail.

In the above components, the reason for limiting the size of the steel to 5 mm or less is as follows. If it exceeds 5mm, it is preferable to set it to 5mm or less because segregation occurs in the lower part without uniform mixing due to the relative specific gravity difference in the mixing process of steelmaking by-products and steel materials. However, in the case of less than 0.1mm, it is preferable not to use iron less than 0.1mm because a large amount is released into the dust during the mixing process. In addition, in the case of steelmaking by-products, regardless of the basicity (CaO / SiO2 ratio), the melting point of various dusts and slags generated in the steelmaking process was limited to the range of 1250 ℃ or more, which is the melting point of by-products generated in the steelmaking process 1250 ~ 1500 ℃. It is almost lower than the melting temperature of the molten steel at the level, and the results of the inventors of the present invention, when the outside is coated with a coating material of the above conditions, the internal temperature is 1200 ℃ level when the temperature is 1250 ℃ or less when the inner material is melted This is due to the possibility of loss of functionality.

On the other hand, the ratio of steelmaking by-products to steel materials does not need to be specified in order to make the specific gravity of internal materials 3.0 to 5.5, and steel materials are appropriately adjusted to meet the necessary weight in each process or other nonferrous and electric furnace operations. What is necessary is just to mix and use it uniformly. In addition, the outer material was composed of MgO-Al2O3-C system as described above, and limited to each weight ratio, which is in contact with the slag when the MgO concentration is less than 40% and Al2O3 is more than 30% to form a low melting interface layer. This is because there is a phenomenon that the dart coating layer is melted to form, and the coating layer is peeled when the MgO concentration exceeds 70% and the Al 2 O 3 is less than 10%. In addition, the reason for limiting the concentration of C is that less than 3% of the CO layer in the surface layer is insufficient generation of heat insulation effect is insufficient, and if it exceeds 25%, it is difficult to adjust the specific gravity of the above dart due to the low specific gravity of C itself. Because.

Hereinafter, the present invention will be described in detail through examples.

(Example)

In order to confirm the thermal insulation effect of the present invention, the slag dart prepared by the conventional method using the 150kg induction furnace and the slag dart prepared by the present invention were subjected to the experiment as shown in FIG. The molten steel used here is a molten steel having a similar component range after the refining of the converter, and C is used at the level of 0.05%, Mn 0.1%, P 0.012%, and S 0.008%. Stirring conditions were applied, and the slag dart was immersed into the molten steel from the hearth using the up and down immersion apparatus as shown in FIG. 4 after maintaining the molten steel at 1700 ° C. 5 minutes. The composition ratio and specific gravity of the conventional materials and the present invention used at this time are shown in Table 1. Here, in the case of the present invention, the inner material is a case where the converter slag and iron are mixed and used at a 75:25 ratio.

TABLE 1

division Composition ratio (% by weight) Cr ₂ O ₃ Al ₂ O ₃ MgO Fe ₂ O ₃ CaO SiO ₂ Fe C importance Conventional 24.6 25.2 8.6 39.6 - - 3.31 Invention Out - 28.4 56.2 - - 15.4 3.58 inside - 2.6 7.2 19.3 35.2 10.3 25.4 -

Meanwhile, in order to measure the thermal insulation effect of the slag dart, a thermocouple was inserted at intervals of 20 mm from the bottom of the slag dart, and the temperature was measured in each section. The temperature comparison between the conventional and the present invention was performed.

5 is a graph schematically showing the results of temperature measurement by the above method. As shown in the drawing, in the conventional case, heat transfer to the inside of the present invention is larger, so that the temperature of the center of the dart rises to 1550 ° C. and also shows a nearly linear temperature drop inside the dart. Due to the effect, the temperature in the center of the dart was obtained as low as 1200 ℃, and also showed a sharp temperature drop at the level of 1240 ℃ inside the dart surface coating layer, and then the temperature drop occurred slowly. From this, the conventional heat transfer showed an average level of 15 ° C./mm, and in the case of the present invention, it was able to prove that the inner material can use various by-products generated in the steelmaking process because the blocking effect of the coating material is superior to the conventional material. .

From this fact, the thermal insulation effect of the coating material according to the present invention was proved. After 10 minutes of immersion, the slag dart was taken out and the surface layer of the dart was visually observed. In both cases, the erosion degree was not large. Partial observation was made, but in the case of the present invention, it was confirmed that the surface layer was kept in a clean state.

As described in detail above, slag dart and slag using a low-cost raw material in addition to preventing slag mixing by steelmaking by providing a composition of a slag cutting mechanism that is added to prevent slag mixing when the converter and ladle tapping are carried out by the present invention. As it is possible to manufacture a check ball and the like, the cost reduction and slag mixing amount can be greatly reduced.

Claims (2)

In the slag cutting mechanism used to prevent the incorporation of slag in the tapping process of molten metal during the steelmaking refining process, and to tap the molten metal only, the inner material and the outer material are distinguished, but the inner material is the low melting point region in the steelmaking process. A refractory material with a melting point of 1250 ℃ or more and a steel material with a specific gravity of 7 or more and a particle size of 5mm or less are uniformly mixed and manufactured so that the overall specific gravity is 3.0 to 5.5, which is a normal manufacturing level, and the external material is at a high temperature of 1700 ℃ or more. The thickness of the material composed of MgO-Al2O3-C system, which is resistant to heat and corrosion, and the external coating material, is less than 1250 ℃ due to the effect of heat insulation even at 1650 ℃, which is the normal temperature of steelmaking process Composition of the slag cutting mechanism for steelmaking refining slag incorporation, characterized in that the. According to claim 1, the composition of the outer coating material MgO concentration in the weight ratio of 40 to 70%, Al 2 O 3 concentration 10 to 30%, C concentration is composed of 3 to 25 so as to have a thermal insulation function and slag corrosion resistance at the same time Composition of the slag cutting mechanism for steelmaking refining slag incorporation, characterized in that the.