JPH0825786B2 - Refractory for continuous casting and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory for continuous casting suitable for a slide valve plate, a casting nozzle and the like, and a method for producing the refractory.

[0002]

2. Description of the Related Art Generally, alumina / carbon-based bricks are widely used as refractory materials for continuous casting such as slide valve plates and casting nozzles, and their quality characteristics are high corrosion resistance, high strength and high spall resistance. What is needed is excellent.

Alumina-carbonaceous bricks used are prepared by blending a carbon raw material and metallic Si powder in addition to the refractory material, kneading them using a phenol resin as a binder, molding the bricks, and then burying them in coke to form 1300. ~ 150
What has been fired at a high temperature at 0 ° C. is currently common.

However, when this brick is used for a long time or is applied to a steel type having a high oxygen concentration in the steel, the damage to the brick becomes extremely large, and the durability is deteriorated. This is because the influence of the oxygen in the molten steel on the carbon raw material in the brick and the oxidation of the carbon that constitutes the carbon bond is much larger than that of ordinary steel, and the brittle structure becomes significantly brittle, which reduces the corrosion resistance of the brick. Is. Therefore, it is the current situation that the refractory for continuous casting is required to have excellent oxidation resistance and corrosion resistance that can be sufficiently coped with under such use conditions.

In order to improve the oxidation resistance and the corrosion resistance, for example, Japanese Patent Publication No. 1-52349 discloses an aggregate of 55 to 97% by weight of 0.5 to 97% by weight of an aggregate made of one or more refractory inorganic materials. It is composed of an Al alloy having a melting point of 200 to 700 ° C. made of two or more kinds of metals having a particle diameter of 5 mm or less, one or more kinds of Mg alloy of 1 to 30% by weight, and a thermosetting synthetic resin of 2 to 15% by weight, Disclosed is a refractory for treating molten metal, which does not require a firing step at 800 ° C. or higher.

Further, in order to achieve higher strength and higher corrosion resistance, for example, Japanese Patent Application Laid-Open No. 61-41861 discloses a carbon bond characterized by having an aluminum nitride bond and a silicon carbide bond in a matrix. Material sliding ·
Nozzle plate bricks are disclosed. Further, according to the publication, the plate brick is made of refractory raw material 65 to
99% by weight, aluminum content of 51-90% by weight and silicon content of 10-49% by weight, aluminum-silicon alloy powder of 200 mesh or less 0.5-
20 wt% and carbon powder of 200 mesh or less 0.5-
15% by weight of raw material mixture or refractory raw material 65
.About.99% by weight, aluminum powder 0.25 to 18% by weight, and silicon powder 0.05 to 10% by weight 20
A raw material mixture consisting of a mixed powder of 0 mesh or less and 0.5 to 15% by weight of carbon powder of 200 mesh or less is kneaded and molded using an organic binder, and then fired in a nitriding atmosphere. It is manufactured.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Unfired bricks added with a low melting point metal powder as described in Japanese Patent Publication No. 1-52349 have a low melting point metal powder when the brick is in contact with the molten steel. When it reacts with the oxygen in it and becomes an oxide, the brick structure becomes dense due to the volume expansion accompanying the oxide formation, the corrosion resistance is improved, and when a steel type with a high oxygen concentration in the steel is received, the corrosion resistance is superior to conventional bricks. ing.

However, since the unfired brick does not undergo the firing step, carbonization of the phenol resin used as the binder is insufficient, and the binding properties of the raw materials constituting the brick are low. Therefore, the brick strength is lower than that of conventional fired carbon-containing refractory materials for continuous casting, and
There is a drawback that the brittle structure of the brick and the strength embrittlement are large in the intermediate temperature range of 00 to 1000 ° C. This defect is a fatal defect as a plate, such as a large amount of wear and damage on the sliding surface, in some cases, such as a ladle plate that is exposed to an intermediate temperature for a long period of time. Therefore, there is a limit to the use of the brick to which the low melting point metal powder is added.

As a countermeasure for this problem, a method has been proposed in which a low melting point metal powder is added and a silicon resin is used as a binder. However, the silicone resin is much more expensive than the conventionally used phenol resin, and its improvement effect is insufficient.

Further, as disclosed in JP-A-61-41861, a metal Al powder and a metal Si powder are used in combination, or an alumina having an aluminum nitride bond and a silicon carbide bond using an Al-Si alloy is used.・ For carbonaceous bricks, by adjusting the amount of metallic Al powder added and the amount of carbon component,
Aluminum nitride, which is formed in the brick and acts as a binder, has the same effect as the low melting point metal powder of the unfired brick, and therefore can be applied to special steels such as steel grades having a high oxygen concentration in steel.

However, the aluminum nitride, which is the characteristic of this brick, is produced at a low temperature of around 820 ° C. in a nitrogen gas atmosphere, but in an atmosphere in which three components of oxygen-carbon-nitrogen coexist, nitrogen is produced at a high temperature. It is difficult to generate unless the partial pressure is very high.

Generally, firing of bricks is carried out by embedding it in carbon powder such as coke, or by firing propane, kerosene, or heavy oil incompletely in a CO or CO ₂ atmosphere. When a brick to which metal Al powder is added is fired at a high temperature by these methods, aluminum carbide is usually produced rather than aluminum nitride.

Therefore, in order to obtain an alumina-carbonaceous brick having an aluminum nitride bond and a silicon carbide bond in which a metal Al powder and a metal Si powder are used in combination or an Al--Si alloy is used, suppression of aluminum carbide generation is taken into consideration. It is necessary to control and fire the atmospheric conditions such as a nitrogen gas atmosphere, which is highly influenced by the nitrogen atmosphere. Therefore, it is difficult to manufacture with the current equipment, and the equipment needs to be greatly modified. Further, the production of a large amount of aluminum nitride and aluminum carbide has a problem of reducing the digestion resistance of bricks.

That is, an object of the present invention is a refractory for continuous casting, which is suitable for a slide valve plate, a casting nozzle, etc., which has high corrosion resistance and can be used for a long period of time or a steel type having a high oxygen concentration in molten steel. It is to provide a manufacturing method.

[0015]

That is, the refractory for continuous casting according to the present invention is a metal Al powder (A) having a particle size of 0.2 mm or more.
And metal Al powder (B) having a particle size of 0.2 to 0.1 mm A / B =
The composition ratio of 1 to 3 is 1 to 8% by weight, and the metal Si powder is 0.5 to 0.5.
Amounts in the range of 6% by weight and 40% by weight or more of the total amount of metallic Al powder and metallic Si powder, 3 to 20% by weight of ultrafine powder calcined alumina having a particle size of 10 μm or less, and 2 to 12 carbon raw materials.
The composition is characterized in that it is composed of a refractory composition, which is a weight-resisting material, the balance being a refractory composition and a binder in an amount of 2 to 15% by weight with respect to the refractory composition, and is fired in a non-oxidizing atmosphere.

Further, in the method for producing a refractory for continuous casting according to the present invention, a metal Al powder (A) having a particle size of 0.2 mm or more and a metal Al powder (B) having a particle size of 0.2 to 0.1 mm are used. / B = 1 to 3
In the composition ratio of 1 to 8% by weight, the amount of the metal Si powder is in the range of 0.5 to 6% by weight, and the amount of the metal Al powder and the metal Si powder is 40% by weight or more, and the particle size is 10 μm or less. Ultrafine powder calcined alumina is 3 to 20% by weight, carbon raw material is 2 to 12% by weight, and the balance is 2-1 by external coating on a refractory composition which is a refractory raw material.
After kneading 5% by weight of the binder and molding into a predetermined shape,
It is characterized by firing at a temperature of 850 to 1100 ° C. in a non-oxidizing atmosphere.

[0017]

The present invention pays attention to the fact that metallic aluminum has a low melting point and the sinterability of calcined alumina at high temperature, and the examination of the heat treatment method, the addition amount of metallic Al powder, the particle size and the ultrafine powder calcined alumina. As a result of examining utilization of
The amount of powder added, the particle size and the amount of metal Si powder added are adjusted, ultrafine powder calcined alumina is added, and 850 to 850 in a non-oxidizing atmosphere.
By firing at a firing temperature of 1100 ° C, the strength of the refractory, the oxidation resistance in the intermediate temperature range and the structure embrittlement are improved without impairing the spall resistance and digestion resistance, and the corrosion resistance is improved. .

That is, by firing a refractory material in which the grain size and the addition amount of the metal Al powder are limited at a firing temperature of 850 to 1100 ° C. in a non-oxidizing atmosphere, the added metal Al powder is softened and a fine portion of the matrix structure is formed. Penetrate all the way to make the entire brick structure dense and strong. By this action, the corrosion resistance, the strength of the refractory, the structure embrittlement in the intermediate temperature range and the oxidation resistance are improved.

The reason why the firing temperature is limited here is that when the firing temperature is lower than 850 ° C., the softening and melting of the metal Al powder are insufficient, the carbonization of the binder such as the phenol resin is insufficient, and the structure becomes brittle. This is because the improvement effect described above cannot be seen. Further, when fired at a firing temperature higher than 1100 ° C., the added metal Al powder reacts with the carbon raw material to generate a carbide, whereby a refractory having a very high strength can be obtained, but the fire resistance is high. It is because it is not suitable for use as a refractory for continuous casting, since it causes deterioration of corrosion resistance and spall resistance.

The reason for limiting the particle size and the amount of the metal powder added at the same time as the firing temperature is to balance the spall resistance and corrosion resistance of the refractory material. Although finer grain size and increase of addition of metal Al powder are very effective for improving various properties such as corrosion resistance, strength of refractory, structure embrittlement and oxidation resistance in intermediate temperature range, spall resistance It is unsuitable as the target refractory because its properties are significantly reduced. Also,
On the other hand, if the metal Al powder is coarsened too much, the metal Al powder will soften and the matrix structure will become denser if fired at a limited firing temperature, but the softened metal Al powder will become large holes, The compactness of the structure is impaired and the corrosion resistance is reduced. As a result of various studies, the present invention was able to balance the spall resistance and the corrosion resistance by limiting the particle size of the metal Al powder. Then, the metal Si powder is added to prevent deterioration of the digestion resistance of the metal Al powder-added product. The addition amount of the metal Si powder needs to be adjusted according to the addition amount of the metal Al powder.

During use, the molten steel contact portion of the refractory is
Oxidized by oxygen in molten steel. Therefore, in the carbon-containing refractory, the carbon raw material at the molten steel contact site is oxidized, the structure becomes brittle, and the corrosion resistance decreases. However, when the molten steel contact portion is oxidized by oxygen in the molten steel, the refractory of the present invention is added with metallic Al that has penetrated to the fine portion of the matrix structure even if the carbon raw material on the molten steel contact surface is oxidized. The ultra fine powder calcined alumina with a particle size of 10 μm or less reacts,
By forming a strong alumina sintered layer on the molten steel contact surface, corrosion resistance,
Further improve wear resistance to molten steel flow.

The constitution of the raw materials used in the present invention will be described below. Among the metal powders to be added, the addition amount of the metal Al powder is appropriately 1 to 8% by weight, and if the addition amount of the metal Al powder is less than 1% by weight, the desired effect cannot be obtained, When the amount of the metal Al powder added is more than 8% by weight, corrosion resistance is improved but spall resistance is impaired.

The particle size composition of the metal Al powder to be added is such that the particle size of the metal A is 0.2 mm or more, preferably 0.2 to 0.5 mm.
1 powder (A) and a metal Al powder (B) having a particle size of 0.2 to 0.1 mm are preferably used in combination, and the composition is preferably A / B = 1 to 3 in weight ratio. This is because when A / B = 1 is less than 1, the spall resistance is reduced, and when A / B = 3 is exceeded, the metal Al powder is softened, and when melted, the denseness of the brick structure is impaired and corrosion resistance is reduced. This is because it is easy to invite them.

The amount of the metallic Si powder added is adjusted in accordance with the amount of the metallic Al powder added in terms of digestion resistance. Metal S
As the amount of i powder added, 40% or more of the total amount of added metal powder of metal Al powder and metal Si powder is appropriate, and preferably 40%.
~ 80%.

Next, the addition amount of the ultrafine powder calcined alumina having a particle size of 10 μm or less is appropriately 3 to 20% by weight. If the amount added is less than 3% by weight, the effect of adding ultrafine powder calcined alumina cannot be obtained. When the addition amount exceeds 20% by weight, corrosion resistance and wear resistance to molten steel flow are improved, but on the other hand, spall resistance of the molten steel contact portion is decreased, so that cracks frequently occur in the molten steel contact portion, and the molten steel contact portion Brick damage is expected to increase due to peeling and intrusion of metal into the brick, which is not appropriate.

As the carbon raw material to be used, known carbon raw materials such as scaly graphite, artificial graphite, carbon black, coke powder and pitch powder can be used. The amount of carbon raw material added is preferably 2 to 12% by weight based on the total amount of refractory material. The reason for limiting the addition amount is that when the carbon raw material is less than 2% by weight, the slag infiltration resistance and spall resistance of the carbon-containing refractory material deteriorate, and the addition amount exceeding 12% by weight is sufficient for strength. This is because the wear resistance is not obtained and the oxidation of the brick structure due to oxygen in the steel is significantly increased when the steel comes into contact with molten steel, and the characteristics of the carbon-containing refractory cannot be obtained.

The refractory raw material used is one or two kinds of alumina-silica-based natural raw materials such as bauxite and andalusite, and alumina-based synthetic raw materials such as sintered alumina, fused alumina, spinel and mullite. Use more. However, it is necessary to select the refractory raw material according to the usage conditions of the brick, and the refractory raw material is not particularly limited.

The refractory material of the present invention contains a phenolic resin as a binder in an amount of 2 to 15% by weight (a ratio of external coating to the weight of the refractory material) in the refractory material obtained by blending the above-mentioned raw materials in a predetermined amount. ) Using a kneading machine such as a wet pan, a pressure kneader, a high speed mixer, etc., and molding into a predetermined shape using a friction press, an oil press, a vacuum friction press, a vacuum oil press, or a rubber press in some cases. To do. Next, the obtained molded body is dried and then fired in a non-oxidizing atmosphere at 850 to 1100 ° C. As a firing method, a molded body is embedded in coke and fired in a tunnel kiln or a shuttle kiln, or propane, kerosene, and heavy oil are incompletely burned to produce CO, CO.
₂ Examples include a method of firing in an atmosphere.

[0029]

EXAMPLES The refractory material for continuous casting of the present invention will be further described below with reference to examples. Example 1 The firing temperature and utilization of metal Al powder were examined. For the examination, alumina-carbonaceous bricks were trial-produced and the corrosion resistance and spall resistance were evaluated. The results of the examination are described below. The sample was prepared by blending predetermined raw materials, kneading and molding using a phenol resin as a binder, and drying the obtained molded body. Then, the dried compact was embedded in coke and reduction-fired at a predetermined firing temperature to obtain a sample. At this time, the atmosphere during firing is a non-oxidizing atmosphere with oxygen blocked by coke. The corrosion resistance was evaluated by performing a slag erosion test on converter slag, and indexing the amount of erosion after the test with the comparative product as 100. For the evaluation of spall resistance, the sample surface was rapidly heated by a burner, and the presence or absence of cracks was visually observed.

Study A The firing temperature was examined for the Al metal powder added product. A in Table 1
The examination results are shown in. As a result, A1 to A4 (A3 and A
4 is the product of the present invention) is more excellent than the comparative product 1 in the corrosion resistance. Further, as the firing temperature increases, the corrosion resistance improves, but when the firing temperature exceeds 1100 ° C (A5),
On the contrary, the corrosion resistance tends to decrease. Next, 600 ℃
The oxidation resistance in the intermediate temperature range of A1 to A5 was evaluated. Evaluation is compressive strength after oxidation (MPa)
Was measured and the state of collapse of the formed oxide layer was observed. As a result, the strength after oxidation at 600 ° C. is improved by increasing the firing temperature as shown in FIG. In the strength measurement, the oxide layers of A1 and A2 baked at 650 ° C. and 800 ° C. were brittle and crumbled, whereas A baked at 800 ° C. or higher.
3 to A5 are A1 and A baked at 650 ° C. and 800 ° C.
No "brittleness" of the oxide layer such as 2 was observed. Therefore, by adding the Al metal powder, by firing at a firing temperature higher than 800 ° C., it is possible to solve the “brittleness” of the oxide layer in the intermediate temperature region, which was a problem in the non-fired plate with the addition of the Al metal powder. You can From the above results, from the corrosion resistance, the oxidation resistance in the intermediate temperature range and the like, the firing temperature is 850 ° C to 1
It has been found that 100 ° C is desirable.

[0031]

[Table 1]

Study B The amount of Al metal powder added was investigated. The examination results are shown in B of Table 1. As a result, due to the increase of Al metal powder addition,
Corrosion resistance is improved. However, the increase of the addition amount tends to increase the elastic modulus and decrease the spall resistance.

Study C The grain size composition of the Al metal powder was investigated. The examination results are shown in C of Table 1, where the metal Al having a grain size of 0.2 mm or more.
Powder (A), a metal Al powder with a particle size of 0.2 mm to 0.1 mm
(B). As a result, the corrosion resistance decreases due to the increase of the weight ratio (A / B) of (A) and (B), and when A / B = 3 is exceeded, the corrosion resistance becomes almost the same as that of the comparative product. Further, when A / B is less than 1, the finer the particle size of the metal Al powder is, the more the corrosion resistance is improved, but the spare resistance is remarkably reduced, and therefore it cannot be said to be suitable for the intended use. Therefore, it is understood that the composition of the metal Al powder is preferably within the range of A / B = 1 to 3 when added.

Example 2 The relationship between firing temperature and digestion resistance when Al metal powder and Si metal powder were used together was investigated. As shown in Table 2, a sample was prepared by blending predetermined raw materials, kneading with a phenol resin as a binder, and then applying φ5 at a pressure of 1000 kgf / cm ^2.
It was molded into a shape of 0 mm × 50 mm. Then dry,
It was embedded in coke and fired at each temperature of 800 ° C to 1500 ° C.

[0035]

[Table 2]

The digestion test was performed on the sample using an autoclave under the conditions of water vapor pressure of 980 MPa and 105 ° C./3 hours, and the evaluation was conducted by visually observing the crack generation state of the sample after the test. The results of the digestion test are shown in FIG. As a result, as shown in FIG. 2, when the amount of Si metal powder is less than 40% in the total metal addition amount of Al metal powder and Si metal powder (A, B, C),
Digestion resistance is very poor regardless of firing temperature. But,
When the amount of Si metal powder is 40% or more (D, E and F), some cracks are observed depending on the firing temperature, but it is possible to prevent degradation of digestion resistance by firing at an appropriate firing temperature. I understand.

Example 3 The effect of adding ultrafine calcined alumina was investigated. The examination method is the same as that of the first embodiment. Table 3 shows the examination results.

[0038]

[Table 3]

As a result, it can be seen that the corrosion resistance is improved as the amount of the ultrafine powder calcined alumina added is increased, and the use of the ultrafine powder calcined alumina is effective in improving the corrosion resistance. However, since the spall resistance tends to decrease due to the increase in the amount of addition, it can be said that addition of more than necessary is not desirable.

Example 4 Based on the examination results of Examples 1 to 3, alumina-carbonaceous bricks were prototyped and tested in an actual furnace. Table 4 shows the quality of prototype bricks. For the trial production, the raw materials shown in Table 4 were blended and kneaded using a phenol resin, and 230 mm x 1
After being molded into a 14 mm × 65 mm shape and dried, it was fired at a firing temperature of 900 ° C. in a non-oxidizing atmosphere (embedded in coke). As shown in Table 4, the product of the present invention is superior in quality to the comparative product. The hot strength characteristics of the present invention product 1 and the comparative products 3 and 4 were investigated. Comparative product 3 is a non-fired plate material added with Al metal powder, and comparative product 4 is a conventionally used firing plate material.

[0041]

[Table 4]

As a result, as shown in FIG. 3, the hot strength characteristics of the conventional materials tend to decrease in strength at high temperatures, but the Al metal powder added products (Invention product 1 and Comparative product 3) are There is no reduction in strength at high temperature, and the product 1 of the present invention is the product of comparative product 3
Higher strength than Therefore, it can be seen that the product of the present invention improves and improves the conventional hot strength property. Further, the product 1 of the present invention and the comparative products 3 and 4 were used as ladle slide valve plates by Company A, which often operates with steel types having a high oxygen concentration in steel (oxygen concentration 100 to 200 ppm). As a result, the comparative products 3 and 4 had severe melting loss at the molten steel contact portion, and the maximum service life was 3 charges (hereinafter referred to as ch), but
The product 1 of the present invention has less surface damage than the comparative product, enables stable use of 4 channels, and has improved durability. Next, the product 2 of the present invention was used as a slide valve lower nozzle for a ladle of Company B. As a result, Comparative product 5 had a large melting loss, and the limit of use was 3ch. However, by applying the product 2 of the present invention, 4
The stable use of ch has become possible.

[0043]

EFFECTS OF THE INVENTION The refractory for continuous casting of the present invention has high corrosion resistance and spall resistance that can be used for a long period of time or a steel type having a high oxygen concentration in molten steel, and has a slide valve plate, a casting nozzle, etc. It is a refractory suitable for.

[Brief description of drawings]

FIG. 1 Firing temperature of the refractory material obtained in Study A of Example 1
2 is a graph showing the relationship between (° C.) and the compressive strength (MPa) after oxidation at 600 ° C. for 3 hours.

FIG. 2 shows the relationship between the ratio (%) of metal Si powder in the total amount of metal Al powder and metal Si powder of refractories A to F obtained in Example 2 and the digestion resistance for each firing temperature (° C.). This is the summary result.

FIG. 3 is a graph showing hot bending strength (MPa) at each measurement temperature (° C.) of the refractory material obtained in Example 4.

Claims (2)

[Claims] 1. A / B = 1 for a metal Al powder (A) having a particle size of 0.2 mm or more and a metal Al powder (B) having a particle size of 0.2 to 0.1 mm.
1 to 8 wt% in composition ratio of ~ 3, 0.5 to 6 of metal Si powder
An amount of 40% by weight or more of the total amount of the metal Al powder and the metal Si powder in an amount in the range of% by weight, 3 to 20% by weight of ultrafine powder calcined alumina having a particle size of 10 μm or less, and 2 to 12% by weight of carbon raw material. %, The balance being composed of a refractory composition which is a refractory raw material and a binder of 2 to 15% by weight on the basis of the refractory composition, which is fired in a non-oxidizing atmosphere. Refractories for. 2. A / B = 1 of a metal Al powder (A) having a particle size of 0.2 mm or more and a metal Al powder (B) having a particle size of 0.2 to 0.1 mm.
1 to 8 wt% in composition ratio of ~ 3, 0.5 to 6 of metal Si powder
An amount of 40% by weight or more of the total amount of the metal Al powder and the metal Si powder in an amount in the range of% by weight, 3 to 20% by weight of ultrafine powder calcined alumina having a particle size of 10 μm or less, and 2 to 12% by weight of carbon raw material. %, The balance is 2 to the external refractory composition
A method for producing a refractory for continuous casting, which comprises kneading 15% by weight of a binder, shaping the mixture into a predetermined shape, and then firing the mixture in a non-oxidizing atmosphere at a temperature of 850 to 1100 ° C.