JP2011256074A - Closing material for blast furnace taphole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a closing material for a blast furnace taphole capable of satisfying both suppression of generation of a cave at opening the taphole and excellent corrosion resistance to molten pig iron and slag, and capable of stably tapping molten pig iron.SOLUTION: The closing material for blast furnace taphole includes a 2-10 mass% of first carbon black having 60-120 nm of particle diameter and 10-50 mL/100g of DBP oil absorption; and a 0.5-6.0 mass% of second carbon black having 10-50 nm of particle diameter and having 100mL/100g or less of the DBP oil absorption.

Description

  The present invention relates to a tap hole closing material used for filling and closing a tap hole of a blast furnace.

  Conventionally, refractory raw materials such as alumina raw materials, siliceous raw materials, silicon carbide raw materials, silicon nitride raw materials, carbonaceous raw materials, clay raw materials, metal powders, etc., have been called as blast furnace outlet closing materials (mud materials) A material kneaded with a binder (binder) such as tar or phenol resin is used.

  The above-mentioned clayey raw material is used for the purpose of imparting plasticity in order to ensure the filling ability to the tap hole required for the tap hole closing material. However, when the amount of the clay material added is increased, the amount of the binder added is increased, and the moisture content and alkali components in the crystal structure of the clay mineral form a low melting point compound and the corrosion resistance against the slag is lowered.

  In recent years, carbon black has been used as a raw material for imparting plasticity in place of a clay-based raw material (see, for example, Patent Documents 1 to 3). Carbon black is fine spherical carbon generated by thermal decomposition or incomplete combustion of natural gas, hydrocarbons, etc., and is classified into types such as channel black, furnace black, lamp black, and thermal black depending on the production method. These various carbon blacks have different particle sizes, specific surface areas, structures, etc., and properties are also greatly different.

JP 08-119754 A Japanese Patent Laid-Open No. 10-36177 JP 2008-105891 A

With the recent increase in the size of the blast furnace, the increase in the amount of tapping due to high-pressure operation, the reduction of the coke ratio due to the injection of pulverized coal, etc. Has become harsh. Therefore, the characteristics required for the tap hole closing material in the blast furnace are becoming stricter. Particularly important characteristics include the following three points.
(1) Extrudability during construction that allows easy filling of the tap hole with a mud gun, and good openability.
(2) After filling the tap hole closing material, the tap hole closing material sinters in a short time, and cracks (lateral holes) hardly occur when the tap hole is opened.
(3) It must withstand chemical erosion caused by hot metal and slag during use, has no expansion of the diameter of the tap hole, and has corrosion resistance that enables stable tapping for a long time.

  The above-mentioned Patent Document 1 discloses a tap hole closing material containing 3% or less of a clay component and 2 to 20% by weight of carbon black. Further, it is disclosed that the particle size of carbon black is desirably 200 nm or less in order to ensure good slipperiness even when the clay component is reduced. However, as disclosed in Patent Document 1, the particle size of carbon black distributed in the market is usually 200 nm or less. Accordingly, the particle size disclosed in Patent Document 1 does not substantially define the characteristics of a suitable carbon black, and Patent Document 1 simply discloses a spout closing material added with carbon black. It can be said that. According to this configuration, Patent Document 1 says that the addition of carbon black improves the corrosion resistance without impairing the filling property and the openability, but according to the study by the present inventors, the type of carbon black to be added ( The effect varies greatly depending on the particle size. That is, based on the disclosure of Patent Document 1, it is not possible to obtain a sprue hole closing material that satisfies the above-mentioned characteristics (1) to (3).

  Patent Document 2 discloses a tap hole closing material containing 2 to 15% by weight of carbon black having a DBP oil absorption of 100 ml / 100 g or less for the purpose of reducing the amount of binder added. When the added amount of the binder is reduced, the material strength of the tap hole closing material is increased and the corrosion resistance is improved. However, when the strength of the plugging material is high, there are problems that it is difficult to open the hole and that a “lateral hole” is easily generated at the time of opening. A horizontal hole means the crack formed in the obstruction | occlusion material in a blast furnace when the obstruction | occlusion material with which the tap hole was filled and hardened | cured with the heat | fever in a blast furnace was opened with a hole drill (drill). When this horizontal hole is generated, hot metal or hot metal enters the horizontal hole and the drill of the hole puncher is melted, so that a smooth opening operation cannot be performed.

  Furthermore, Patent Document 3 uses a carbon black of 3 to 10% by weight of DBP (dibutyl phthalate) oil absorption of 10 to 80 ml / 100 g and ultrafine silica powder, and a ratio of 10 to 17% by weight with an organic binder as an outer shell. The potting hole blocking material blended in (1) is disclosed. According to this configuration, although the corrosion resistance of the tap hole closing material is improved, since the material strength is increased, a horizontal hole is likely to be generated as in the technique of Patent Document 2.

  As described above, none of the conventional techniques can satisfy all the above-mentioned characteristics (1) to (3) required for the tap hole closing material.

  The present invention has been proposed in view of the above-described conventional circumstances, and is capable of achieving both suppression of horizontal hole generation during opening and excellent corrosion resistance against hot metal and slag, and enables stable tapping. It is an object to provide a spout closing material.

  The inventors of the present application have intensively studied a method for suppressing the material strength of the tap hole closing material for suppressing the occurrence of the horizontal hole while maintaining the corrosion resistance against the hot metal and the slag, and reached the present invention. Conventionally, as disclosed in the above patent documents, one type of carbon black raw material having a particle size range has been used. However, the inventors of the present application can combine at least two types of carbon black raw materials having different particle sizes. It has been found that it is effective for realizing a sprue hole closing material with reduced material strength while maintaining corrosion resistance.

  That is, the blast furnace tapping hole plugging material according to the present invention has a particle size of 60 to 120 nm, a DBP oil absorption of 10 to 50 ml / 100 g of first carbon black of 2 to 10% by mass, and a particle size of 10 to 10%. 2nd carbon black 0.5-6.0 mass% of 50 nm and DBP oil absorption is 100 ml / 100g or less is contained.

  In addition, in this specification, a particle size means the arithmetic mean diameter calculated | required based on the observation with an electron microscope employ | adopted as a general manufacturer catalog value. The particle size of carbon black, which is generally distributed on the market and is readily available, is 10 to 150 nm. The DBP oil absorption is a value measured in accordance with JISK6221.

  According to the present invention, by using at least two types of carbon black having different particle diameters, it is possible to provide a brewing hole blocking material that has a small amount of added binder and that can achieve both corrosion resistance and openability. Become.

The figure for demonstrating the shape of the stainless steel sample holder used in order to measure extrusion resistance pressure. The figure for demonstrating the measuring apparatus used in order to measure extrusion resistance pressure.

  The blast furnace tapping hole plugging material according to the present invention has a particle size of 60 to 120 nm, a DBP oil absorption of 10 to 50 ml / 100 g of first carbon black of 2 to 10% by mass, a particle size of 10 to 50 nm, And it contains 0.5-6.0 mass% of 2nd carbon black whose DBP oil absorption is 100 ml / 100g or less, It is characterized by the above-mentioned.

  First, the first carbon black will be described. As described above, carbon black can impart plasticity equivalent to that of a clayey raw material to a blast furnace outlet hole closing material. Therefore, the use of the first carbon black can also reduce the clay-based raw material added for the purpose of imparting plasticity and suppress the deterioration of the corrosion resistance. In addition, since the first carbon black has a relatively low DBP oil absorption of 10 to 50 ml / 100 g, the amount of binder such as tar can be reduced during kneading.

  In addition, it is preferable that the particle size of the first carbon black is less than 60 nm because the DBP oil absorption amount is relatively larger than the specific surface area is increased, and the amount of the binder to be added is increased and the corrosion resistance is decreased. Absent. In addition, if the particle size of the first carbon black exceeds 120 nm, the sintering suppressing effect is reduced, and side holes are easily generated, which is not preferable. A more preferable range of the particle size of the first carbon black is 70 to 90 nm. Further, if the DBP oil absorption of the first carbon black is less than 10 ml / 100 g, the sintering suppressing effect is reduced, which is not preferable. On the other hand, if the DBP oil absorption amount of the first carbon black exceeds 50 ml / 100 g, the corrosion resistance decreases, which is not preferable. The DBP oil absorption of carbon black used in the present invention is more preferably in the range of 20 to 35 ml / 100 g. Further, if the amount of the first carbon black added is less than 2% by mass, the effect of addition becomes small, which is not preferable. Moreover, when the addition amount of 1st carbon black exceeds 10 mass%, since an intensity | strength fall becomes remarkable, it is unpreferable. As for the addition amount of 1st carbon black, 3-6 mass% is more preferable.

  Although not particularly limited, for example, thermal black can be used as the first carbon black. Thermal black, which is one type of carbon black having a particle size of 60 nm or more, is produced by repeatedly burning and decomposing gas in a heat storage furnace. Thermal black has a coarser shape than furnace black, which occupies most of the carbon black in circulation. Thermal black has a DBP oil absorption less than other carbon blacks (furnace black, etc.) and has no developed structure, so it tends to exist as isolated spherical particles. Therefore, it is possible to further suppress the addition amount of a binder such as tar for ensuring the smoothness (fillability) of the tap hole closing material, and to reduce the porosity of the tap hole closing material. Further, improvement in corrosion resistance can be expected. Carbon black other than thermal black can be used as long as the particle size is 60 to 120 nm and the DBP oil absorption is 10 to 50 ml / 100 g.

  Next, the second carbon black will be described. Similar to the first carbon black, the use of the second carbon black can also reduce the clay-based raw material that lowers the corrosion resistance. Moreover, the addition of a small amount of the second carbon black has an effect of suppressing the sintering of the structure of the tap hole closing material, blocking the pores of the tap hole closing material structure, and reducing the porosity. That is, the first carbon black described above has a lower sintering suppression effect than carbon black having a finer particle diameter, such as the second carbon black. Therefore, when only the first carbon black is used, there is a possibility that high strength is obtained due to oversintering and it is difficult to make holes. However, this can be prevented by using the second carbon black. That is, by using together the 1st carbon black which can reduce the amount of tar addition, and has an effect in the improvement of corrosion resistance, and the 2nd carbon black which has the effect of closing up the pore between occlusion material organization and reducing the porosity. It is possible to provide a tap hole closing material that is a low-strength material that is easy to open and has excellent corrosion resistance.

  Since the second carbon black has a larger specific surface area than the first carbon black, conversely, when only the second carbon black is used, the amount of a binder such as tar increases remarkably. As the amount of binder added increases, the porosity increases and the corrosion resistance decreases. However, by using the first and second carbon blacks in combination, it is possible to suppress sintering of the structure of the tap hole closing material while suppressing an increase in the amount of binder added. In particular, carbon black of 20 to 30 nm is extremely effective in improving the corrosion resistance against slag by closing pores distributed in the pore-sealing material structure due to the fineness of the particle size, lowering the porosity.

  It should be noted that if the particle size of the second carbon black is less than 10 nm, the amount of tar added is remarkably increased, and if the particle size exceeds 50 nm, the effect of reducing the porosity is reduced, which is not preferable. The particle size of the second carbon black is more preferably 20 to 30 nm. Further, if the DBP oil absorption amount of the second carbon black exceeds 100 ml / 100 g, the tar addition amount is remarkably increased, which is not preferable. The DBP oil absorption amount of the second carbon black is more preferably 40 to 60 ml / 100 g. Furthermore, if the amount of the second carbon black added is less than 0.5% by mass, the effect of addition is reduced, which is not preferable. On the other hand, if the amount of the second carbon black added exceeds 6.0% by mass, the amount of tar added is remarkably increased. The addition amount of the second carbon black is more preferably 1 to 3% by mass.

  The types of refractory raw materials other than the first and second carbon blacks used in the tap hole closing material according to the present invention are the same as those of the conventional tap hole closing material. As the main material, for example, an alumina material, a clay material, a silicon carbide material, a silicon nitride material, a carbon material and the like can be used. In addition, silica fume, clayey raw material, and the like can be added in order to further impart plasticity at the time of plugging and filling as long as desired characteristics are obtained. In addition, in this invention, since the addition amount of a binder is prescribed | regulated with an external coating with respect to the other raw material except a binder as mentioned later, a binder shall not be included in a refractory raw material for convenience.

Examples of the alumina raw material include bauxite, clay soil shale with an Al ₂ O ₃ content of 80% by mass or more, or fused alumina, sintered alumina, temporary alumina with an Al ₂ O ₃ content of 95% by mass or more in order to improve corrosion resistance. Use baked alumina. The alumina material is preferably added in an amount of 30% by mass or less in the refractory material. If it exceeds 30% by mass, the corrosion resistance against slag is lowered, which is not preferable. In particular, a preferable range is 20 to 30% by weight. In addition, in order to ensure corrosion resistance, it is preferable to use an alumina raw material as a refractory raw material, but it is also possible to employ no addition of an alumina raw material as a composition of the refractory raw material. In this case, rholite, which is a siliceous raw material, can be used instead of the alumina raw material. Further, rholite may be added to the refractory raw material in addition to the alumina raw material in the above range.

  Here, the clay-based raw material is mainly used for the purpose of imparting the slipping property required for workability when filling the blast furnace exit hole with the exit hole closing material. The clay material is preferably added in the range of 2 to 10% by mass in the refractory material. If the clay raw material is less than 2% by mass, the slipping property when filling the tap hole closing material into the tap hole decreases, and if it exceeds 10% by mass, the corrosion resistance decreases, such being undesirable.

  A silicon carbide raw material can be used as needed. The use of a silicon carbide raw material is particularly preferable because it is effective for corrosion resistance to slag. The silicon carbide raw material is preferably added at 30% by mass or less in the refractory raw material. This is because if it exceeds 30% by mass, the corrosion resistance to hot metal tends to be inferior.

  Examples of the silicon nitride-based material include silicon nitride and silicon iron iron, and one of them or a mixture of both can be used. The silicon nitride material is preferably added in an amount of 10 mass% or more in the refractory material. When the silicon nitride material is less than 10% by mass, the effect of addition is small, and the original effect of adding the silicon nitride material (formation of SiC bond) cannot be exhibited.

  As the carbonaceous raw material, in addition to the carbon black listed in the present invention, one or more of carbon coke, coal coke, anthracite, natural graphite, artificial graphite and the like having a carbon content of 80% by mass or more are used as a carbon source. Can be used as required.

Furthermore, various metal powders may be added as necessary to achieve a strength development effect. As the metal source, aluminum, silicon, ferrosilicon, titanium, Al—Si alloy, magnesium diboride (MgB ₂ ), or the like is applicable.

  As the binder (binder), thermoplastic carbonaceous resins such as tars, pitches and phenol resins can be used. The addition amount is preferably in the range of 5 to 30% by mass with respect to the refractory raw material. If necessary, a solvent such as creosote can be added to these binders.

  Note that the blending of the refractory raw materials other than the first and second carbon blacks described above is an example of a particularly preferred blending, and can be changed as appropriate within the scope of the effects of the present invention.

  Examples of the present invention and comparative examples will be presented below to describe the tap hole closing material of the present invention.

  A blend of refractory raw materials was prepared at the blending ratio shown in Table 1, the obtained blended material was kneaded for about 5 minutes, a binder kept at 60 ° C. was added and kneaded for about 30 minutes. In Examples 1 to 6 and Comparative Examples 1 to 7, anhydrous coal tar was used as a binder. The amount of anhydrous coal tar added was adjusted to about 350 kgf (total load by our testing machine) by measuring the extrusion resistance (Marshall test). This extrusion resistance was measured using a measuring apparatus 5 shown in FIG. 2 after filling a stainless steel sample holder 1 shown in FIG. As shown in FIG. 1, the sample holder 1 has an inner diameter taper portion whose inner diameter decreases downward and the same inner diameter portion above the inner diameter taper portion, an outer diameter L1 = 90 mm, and the same inner diameter portion inner diameter L2. = 60 mm, total length L3 = 260 mm, inner diameter taper portion length L4 = 120 mm, inner diameter taper portion lower end inner diameter L5 = 20 mm. The measuring apparatus 5 shown in FIG. 2 has a lower end of the inner diameter taper portion of the sample holder 1 when the cylinder head 2 fitted to the same inner diameter portion of the sample holder 1 is inserted from the upper end side of the same inner diameter portion of the sample holder 1. Extrusion resistance is measured as the total load applied to the face plate 4 for extruding the sample that is disposed on the side facing the pedestal 3. The extrusion speed of the cylinder head 2 is 10 mm / second.

  In each of the examples and comparative examples, the bending strength and the apparent porosity are measured for a specimen molded to 40 × 40 × 160 mm at a molding pressure of about 5 MPa and reduced and heated at 1500 ° C. for 3 hours. . Furthermore, the corrosion resistance test was conducted using a rotating arc furnace erosion test method using pig iron and blast furnace slag as an erodant, tested in a reducing atmosphere at 1550 ° C for 6 hours, then cutting the specimen and measuring the erosion dimensions. And the erosion dimension when the erosion dimension of the comparative example 1 is set to 100 is indexed to obtain a erosion index. The smaller the melting index, the better the corrosion resistance. These results are shown in Table 1. Symbols ◎, ○, Δ, and × in the table are evaluation items for bending strength, apparent porosity, and corrosion resistance. ◎ is very good, ○ is good, △ is not enough, and × shows a defect.

  Uses fire-resistant aggregate containing alumina, rholite, silicon carbide, silicon nitride iron, coke powder, clayey raw material, and carbon black with a particle size of 30 nm and DBP oil absorption of 110 ml / 100 g, and anhydrous coal as binder (binder) Compared to Comparative Example 1 using tar, Example 1 adds 1% by mass of carbon black (second carbon black) having a particle size of 47 nm and 4% by mass of carbon black (first carbon black) having a particle size of 80 nm. It is a combination. In Example 1, compared with Comparative Example 1, the bending strength after heating at 1500 ° C. is about the same, but the apparent porosity is lowered and the erosion index is also lowered. That is, Example 1 shows that the high strength is suppressed and the corrosion resistance is improved.

  In Example 2, 1% by mass of carbon black having a particle size of 24 nm (second carbon black) and 4% by mass of carbon black having a particle size of 80 nm (first carbon black) were added. In Example 2, the porosity is further reduced compared to Example 1, and the corrosion resistance is improved.

  In Example 3, 3% by mass of carbon black having a particle size of 24 nm (second carbon black) and 6% by mass of carbon black having a particle size of 80 nm (first carbon black) were added. In Example 3, the porosity is further lowered than in Example 2, and the corrosion resistance is improved. However, since carbon black is expensive, it is considered that the formulation of Example 2 may be more beneficial than Example 3 in consideration of cost.

  In addition, Example 4 which is a formulation in which 1% by mass of carbon black having a particle size of 24 nm (second carbon black) and 2% by mass of carbon black having a particle size of 80 nm (first carbon black) is added, having a particle size of 24 nm Example 5 in which 1% by mass of carbon black (second carbon black) and 8% by mass of carbon black having a particle size of 80 nm (first carbon black) were added, and carbon black having a particle size of 24 nm (second carbon black) In the same manner as in Example 6 in which 5% by mass of carbon black) and 2% by mass of carbon black having a particle diameter of 80 nm (first carbon black) were added, comparison was made by adding two types of carbon black. Compared to Example 1, an improvement in corrosion resistance is observed.

  Hereinafter, each of Comparative Examples 1 to 7 will be briefly described.

  Comparative Example 1 is a blend in which 5% by mass of carbon black having a particle size of 30 nm and a DBP oil absorption of 110 ml / 100 g is added, and contains 2 to 20% by weight of carbon black disclosed in Patent Document 1. Compared with Examples 1-6, there was much tar addition amount, the porosity was high, and the fall of corrosion resistance was recognized. Therefore, when carbon black having a DBP oil absorption amount larger than 100 ml / 100 g is used, the tar addition amount is remarkably increased. Therefore, it can be said that the DBP oil absorption amount of the carbon black to be used is desirably 100 ml / 100 g or less.

  Comparative Example 2 is a blend in which only 5% by mass of carbon black having a particle size of 80 nm and a DBP oil absorption of 28 ml / 100 g is added. Compared with Comparative Example 1, the tar addition amount is reduced, but the strength is increased, and there is a concern about the decrease in the pore opening property.

  Comparative Example 3 is a formulation in which only 5% by mass of carbon black having a particle size of 24 nm and a DBP oil absorption of 53 ml / 100 g is added, and is included in the contents disclosed in Patent Document 2. When only carbon black having such a fine particle size of 24 nm is used, the amount of tar added is large and the corrosion resistance is low as compared with Examples 1-6.

  Comparative Example 4 is a blend containing 5% by weight of ultrafine silica powder disclosed in Patent Document 3 and 5% by weight of carbon black having a particle size of 80 nm and a DBP oil absorption of 28 ml / 100 g. Compared with Examples 1-6, intensity | strength is high and we are anxious about the fall of openability.

  Comparative Example 5 is a blend in which 4% by mass of carbon black with a particle size of 24 nm and DBP oil absorption of 53 ml / 100 g and 1% by mass of carbon black with a particle size of 80 nm and DBP oil absorption of 28 ml / 100 are added. Compared with Examples 1 to 6, the tar addition amount is large, and no obvious improvement in corrosion resistance is observed.

  Comparative Example 6 is a blend in which 4% by mass of carbon black with a particle size of 24 nm and DBP oil absorption of 53 ml / 100 g and 12% by mass of carbon black with a particle size of 80 nm and DBP oil absorption of 28 ml / 100 are added. Similar to Comparative Example 5, the tar addition amount is large, the strength is remarkably lowered, and the corrosion resistance is also lowered.

  From the results of Comparative Example 5, Comparative Example 6 and Examples 1 to 6, it can be said that 2 to 10% by mass of carbon black having a particle size of 80 nm and a DBP oil absorption of 28 ml / 100 is effective.

  Comparative Example 7 is a blend in which 7% by mass of carbon black having a particle size of 24 nm and DBP oil absorption of 53 ml / 100 g and 4% by mass of carbon black having a particle size of 80 nm and DBP oil absorption of 28 ml / 100 are added. Similar to Comparative Example 1, the tar addition amount was remarkably increased, and a clear decrease in corrosion resistance was observed as compared with Examples 1-6. From this result, it can be said that the effective addition amount of carbon black having a particle size of 24 nm and a DBP oil absorption of 53 ml / 100 g is 6% by mass or less.

  From the above results, by using carbon black with different particle sizes in combination and defining the addition amount, the strength is suppressed (maintains moderate strength), the tar addition amount is reduced, and the corrosion resistance is improved. Is considered possible.

  Further, in the above examples, an example in which anhydrous coal tar is used as a binder has been described, but other tars, pitches, and thermoplastic carbonaceous resins such as phenol resins can also be used. It is possible to obtain the same result as in the example.

  According to the present invention, it is possible to provide a tap hole closing material having a small binder addition amount, excellent corrosion resistance, and excellent hole opening property, and a smooth hole opening operation at the time of taping can be expected.

1 Sample Holder 2 Cylinder Head 3 Base 4 Sample Extruding Face Plate 5 Extrusion Resistance Pressure Measuring Device

Claims (2)

2 to 10% by mass of a first carbon black having a particle size of 60 to 120 nm and a DBP oil absorption of 10 to 50 ml / 100 g;
0.5 to 6.0% by mass of a second carbon black having a particle size of 10 to 50 nm and a DBP oil absorption of 100 ml / 100 g or less,
A blast furnace tapping hole plugging material characterized by comprising:   The blast furnace tapping hole plugging material according to claim 1, wherein the first carbon black is thermal black.

Images