JPH09194253A - Carbon-containing basic refractories and melting and refining vessel for molten metal lined with these refractories - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide carbon-contg. basic refractories improved in wear resistance, spalling resistance and hot strength without impairing the corrosion resistance and oxidation resistance thereof and to obtain a melting and refining vessel for molten metal having high durability and long life by lining part or the whole of the heavily wearing section of the melting and refining vessel with these refractories. SOLUTION: An SiC raw material of which the max. grain size [X] (μ) and amt. of addition [Y] (wt.%) in outer per cent satisfy the equation [Y]<=3log[X] is added to 100wt.% compounded compsn. composed of 70 to 94wt.% MgO-based refractory raw material, 5 to 25wt.% C-based refractory material and 1 to 5wt.% Ca-contg. metal. The SiC raw material of a grain size of 0.1 to 0.5mm is otherwise added at <=8wt.% or the SiC raw material having a grain size of 0.5 to 1.0mm is added at <=9wt.% thereto. The mixture is thereafter kneaded and molded by using a binder and is then dried, by which the carbon-contg. basic refractories are obtd. Part or the whole in the furnace is lined with such refractories, by which the melting and refining vessel for molten metal having the high durability and long life is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon-containing material used for lining or completely lining a part of a furnace bottom or a side wall of a melting and refining vessel for molten metal such as a smelting reduction furnace, a scrap melting furnace, and a converter. The present invention relates to a refractory material and a melting / refining vessel for molten metal having a refractory lining.

[0002]

2. Description of the Related Art In recent years, in smelting reduction furnaces, scrap melting furnaces, converters, etc., which are generally used in the pig steel process, in order to improve the melting and refining efficiency, the upper-bottom blowing stirring force and the secondary combustion ratio have been improved. As a result, the refractory linings are exposed to harsh conditions. Melting for these molten metals
MgO-C bricks have been conventionally used as refining vessels. However, especially as the secondary combustion ratio increases, the temperature rises from the slag bath to the atmosphere, and not only the slag reaction at high temperatures but also the oxidation of C in the bricks, molten steel at high temperatures, slag, dust, etc. Wear due to flow or heat spall due to increased temperature change on the working surface of bricks have become noticeable.

Corrosion resistance, oxidation resistance, abrasion resistance, spall resistance, and hot strength are required as properties that a brick must have against the wear caused by these factors.
Instead MgO-C bricks, the use of MgO-Cr ₂ O ₃ brick was attempted. However, the thermal and structural spalls are so severe that satisfactory results have not been obtained.

On the other hand, for MgO-C bricks, electromelted MgO is used for the purpose of improving corrosion resistance, oxidation resistance and hot strength.
It is practiced to use raw materials and increase the amount of added metal. However, on the other hand, there is a problem that the spall resistance is reduced. Further, JP-A-3-208862 describes that SiC is added in an amount of 1 to 6% by weight for the purpose of improving oxidation resistance. However, this amount added is not sufficient for improving the oxidation resistance, and conversely causes a problem that the corrosion resistance decreases.

[0005]

As described above, MgO-
Although there are means to improve the corrosion resistance, oxidation resistance, and hot strength of C bricks, there is a problem that spall resistance is reduced, and there is no means to satisfy all the above five characteristics. Has not been done. The present invention has been made in view of such a problem, corrosion resistance, without impairing the oxidation resistance, wear resistance, spall resistance, carbon-containing refractory improved hot strength, and its fire resistance Provided is a melting and refining vessel for molten metal having a high durability and a long life, in which a product is lined in a part or the whole of a furnace.

[0006]

In order to achieve the above object, according to the present invention, 70 to 94% by weight of MgO quality refractory raw material, 5 to 25% by weight of C quality refractory raw material such as scaly graphite, Ca-Si alloy, Ca -Maximum particle size [X] (μ) and addition amount [Y] (% by weight) with respect to 100% by weight of compounding composition composed of 1 to 5% by weight of Ca-containing metal such as -Si-Mg alloy Provides a carbon-containing refractory material obtained by adding a SiC raw material satisfying the following formula (1), kneading and molding using a binder such as phenol resin, and then drying. [Y] ≦ 3log [X] ……… (1)

In particular, with respect to 100% by weight of the above composition, 8% by weight or less of the SiC raw material having a particle diameter of 0.1 mm to 0.5 mm or 9% of the SiC raw material having a particle diameter of 0.5 mm to 1.0 mm is applied. By adding less than or equal to wt%, the spall resistance of the obtained carbon-containing refractory material is significantly improved. Further, the melting and refining vessel for molten metal, in which the carbon-containing refractory material thus obtained is used for a part or the whole of the lining of the furnace, has a low wear rate and can achieve a long life.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, SiC to be added
Is limited by its maximum particle size in order to suppress deterioration of corrosion resistance. SiC reacts with CO gas that has penetrated into the brick, and produces SiO ₂ by the reactions represented by the following formulas (2) and (3). SiC + CO → SiO + C ……… (2) SiO + CO → SiO ₂ + C ……… (3)

The SiO ₂ thus produced forms a glass film and serves to prevent the oxidation of C. However, in the case of the MgO-C system, the viscosity of the glass film is high, and therefore a sufficient antioxidant effect cannot be obtained unless a large amount of SiC is added. Further, since SiC itself has a high hardness, when a small amount of SiO ₂ is produced, this fills the voids of the structure and the wear resistance is improved. However, when a large amount of SiO ₂ is produced, the corrosion resistance is reduced. As described above, SiC has the side of improving the wear resistance of bricks, but has the side of reducing corrosion resistance, so that sufficient consideration must be taken when adding to bricks.

Generally, the finer the solid, the higher the activity of the particle surface, and the faster the reactions of the above formulas (2) and (3) proceed. Therefore, a large amount of SiO ₂ is produced in the brick. Then, the corrosion resistance decreases. On the contrary, when the solid particles are large, the reactions of the above formulas (2) and (3) are limited only to the surface of the particles and the production of SiO ₂ is suppressed, so that the corrosion resistance is less deteriorated. Therefore, when using fine-powdered SiC, the addition amount should be reduced, and when using medium- to coarse-grained SiC,
It is better to increase the amount used.

In the present invention, various experimental investigations were carried out, and as a result, the maximum grain size [X] (μ) and the addition amount [Y] of the added SiC capable of improving the wear resistance without impairing the corrosion resistance. ] (Wt%) is expressed by the formula [Y] ≦ 31 og [X].

Further, since SiC has a smaller thermal expansion coefficient than MgO, microcracks are formed due to the expansion difference from MgO during heating, the elastic modulus of the brick is lowered, and the spall resistance is improved. In order to form such microcracks, it is preferable to increase the amount of medium-grain to coarse-grain SiC added to promote the reaction of SiC in the particle surface layer and leave the inside unreacted. , Especially particle size 0.1
The spall resistance is most excellent when 8% by weight or less is added to the SiC raw material of mm to 0.5 mm and 9% by weight or less is added to the SiC raw material of 0.5 mm to 1.0 mm in particle diameter. If the particle size is smaller than this, the decrease in elastic modulus is small and the corrosion resistance is large. Further, if the particle size is larger than this, the elastic modulus is largely reduced, but the tissue strength is reduced and the cost is increased, which is not preferable.

On the other hand, in order to improve the hot strength, it has been general to increase the content of metallic Al or Al-Mg alloy. However, since these Al-based metals once become oxides via the carbides represented by Al ₄ C ₃ , volume expansion causes an increase in elastic modulus, a decrease in spall resistance, and easy digestion. There was a problem.

On the other hand, when the Ca-containing metal and SiC are used together as in the present invention, SiO produced by the oxidation of SiC
₂ reacts with CaO and MgO to form a CMS-based compound, which improves the hot strength. Since this reaction does not change in volume and occurs in the vicinity of the Ca-containing metal dispersed in the matrix, it has a large bonding effect and is also useful for strengthening the structure (improving abrasion resistance). The Ca-containing metal is also important from the viewpoint of preventing C oxidation, and the Ca-Si-Mg alloy is most effective. However, any metal can be applied as long as it contains Ca. Metals other than the Ca-containing alloy can be used as needed.

The MgO-based refractory raw material used in the present invention may be either sintered or electro-melted regardless of its purity. The C-type refractory raw material can be any graphite, regardless of its purity, as long as it is scaly graphite, and other amorphous graphite, carbon black, mesophase carbon, etc. are also applicable.

As the SiC raw material, those having a purity of 97% or more are preferable, but those having a purity lower than this are also applicable. Brick can be provided as a non-fired product after kneading and molding using a binder such as phenolic resin, tar, and pitch, and then drying. However, further reduction firing and tar impregnation treatment improve the characteristics. These bricks can be used as the lining material for the melting and refining vessels for molten metal such as smelting reduction furnaces, scrap melting furnaces, converters, etc. as the lining material for the bottom and side walls of the bricks. In particular, the effect is great when it is applied to a site where wear is large.

[0017]

An embodiment will be described below with reference to the drawings. As a sample, 99% pure electrofused MgO clinker, 99% pure scaly graphite, and a Ca-Si-Mg alloy were mixed in a predetermined range, and then a 99% pure SiC raw material was added, and phenol resin was used as a binder. A molded product was provided. Corrosion resistance is 170 C / S = 1.2 using slag
The size of the melt-damaged by the rotary erosion method performed under the condition of 0 ° C. × 3 Hrs was expressed as an index. Abrasion resistance is 1600 ° C x 1H
The amount of reduction when MgO particles were sprayed by a thermal spray burner under the condition of r was measured, and the value was evaluated. Further, the elastic modulus was evaluated by measuring the kinetic elastic modulus after reduction firing under the condition of 1400 ° C. × 3 Hrs. Further, the hot strength was obtained by measuring by a three-point bending method in a reducing atmosphere at 1400 ° C.

FIG. 1 shows the relationship between the maximum grain size and the amount of added SiC with respect to corrosion resistance. Corrosion resistance was significantly deteriorated in the region above the straight line shown in the figure. The wear resistance was improved for all of the samples to which SiC was added, but the wear resistance was particularly improved as the particle size of the added SiC was smaller and the addition amount was larger.

On the other hand, the dynamic elastic modulus is such that the particle diameter of the added SiC is 1
If it is 44μ or less, it does not change much, and it is 200μ or less and 5
In the case of 00 μ or less, there was a tendency for the amount to decrease as the addition amount increased, but it was not so remarkable. FIG. 2 shows the relationship between the particle size of SiC added, the amount added, and the dynamic elastic modulus. When medium-sized SiC is added (0.1-0.5 mm
And 0.5 to 1 mm), the dynamic elastic modulus decreased significantly as the addition amount increased, the corrosion resistance did not deteriorate, and the abrasion resistance improved. However, 0.5mm including fine powder less than 0.1mm
When the following SiC was added, the change in the dynamic elastic modulus was slight and the abrasion resistance was improved, but when the addition amount exceeded 8% by weight, the corrosion resistance deteriorated.

Thus, the straight line and the region below it are suitable for improving the corrosion resistance and the wear resistance, and for improving the spall resistance, SiC (0.
It is effective to add 8% by weight or less for 1 to 0.5 mm and 9% by weight or less for 0.5 to 1 mm.

When neither SiC nor Ca-Si-Mg alloy was added, the hot strength at 1400 ° C was 10 MPa, but when only 3% by weight of Ca-Si-Mg alloy was added, 12 MPa, When only 4% by weight of SiC is added, the pressure becomes 11 MPa, 4% by weight of SiC, Ca-Si
-Up to 15 MPa when 3 wt% of Mg alloy was added. Among the bricks invented this time, a refractory obtained by adding 3% by weight of Ca-Si-Mg alloy and medium-sized SiC (0.1 to 0.5 mm: 4% by weight) was used as an ironworks 170T.
As a result of performing a partial tension test as an inner lining material in the trunnion of the drawing furnace of the melting furnace, it became possible to reduce the melting loss rate by about 35% as compared with the conventional product.

[0022]

INDUSTRIAL APPLICABILITY The present invention improves the hot strength in addition to the wear resistance and spall resistance of a carbon-containing refractory, and melts and refines molten metal in a smelting reduction furnace, scrap melting furnace, converter, etc. It becomes possible to remarkably improve the durability of the refractory used for the bottom of the vessel and the lining of the side wall, which not only reduces the cost of furnace materials and repairs but also contributes to the stabilization of production.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the maximum grain size of SiC and the addition amount with respect to corrosion resistance.

FIG. 2 is a diagram showing a relationship between a particle diameter of added SiC, an added amount, and a dynamic elastic modulus.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Yamada 5-3 Tokai-cho, Tokai-shi, Aichi New Nippon Steel Co., Ltd. Nagoya Steel Works

Claims (3)

[Claims] 1. A MgO-based refractory raw material 70 to 94% by weight, C
Quality refractory raw material 5-25% by weight, Ca-containing metal 1-5% by weight
To 100% by weight of the composition of the composition, a SiC raw material whose maximum particle size [X] (μ) and addition amount [Y] (% by weight) satisfy the following equation is added to the binder, and the binder is added. A carbon-containing refractory material obtained by kneading, molding, and drying. [Y] ≦ 3log [X] 2. A SiC raw material having a particle diameter of 0.1 mm to 0.5 mm is 8% by weight or less, or a particle diameter of 0.5 mm to 1 outside.
9. A 0 mm SiC raw material is added in an amount of 9% by weight or less, and the mixture is kneaded and molded using a binder, and then dried to obtain.
The carbon-containing refractory described. 3. A molten metal melting / melting material in which the carbon-containing refractory according to claim 1 or 2 is lined in a part or the whole of a furnace.
Refining vessel.