JPH0354155A - Method for producing graphite-containing bricks for lining molten metal containers - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is for manufacturing graphite-containing bricks used for lining molten metal containers such as ladles, pig iron trucks, pig iron mixing furnaces, vacuum degassing furnaces, converters, etc. Regarding the method.

(Prior Art) In recent years, with the aim of producing high-grade steel, so-called hot metal pretreatment, which removes Si, P, and S from hot metal in the molten metal container, has become popular. This treatment significantly reduces the life of the lining refractory due to the addition of a large amount of flags such as Cab, CaF2, MnO, and Na2GO3 to the hot metal and the temperature increase due to oxygen injection. Furthermore, the conditions for use of steel ladle for storing molten steel, such as receiving high temperature steel and using it for a long time, are becoming stricter.

The refractories lined in these molten metal containers are alumina-silicon carbide-carbon materials (for example, JP-A-63-11795
1) or unburned bricks made of magnesia carbonaceous material (for example, Japanese Patent Application Laid-open No. 117947/1983) are generally used. This brick has excellent corrosion resistance and spalling resistance because it contains carbon. Additionally, since it is a non-burnable product, it has the advantage of lower production costs and faster delivery dates.

(Problem to be solved by the invention) The carbon material used in the production of the carbon-containing brick described above is:
It is mainly phosphorous graphite. This is because the effect of imparting corrosion resistance and durable polling property is greater than that of amorphous carbon powder such as pitch coke.

However, on the other hand, since phosphorous graphite is a carbon material with high thermal conductivity, it has the disadvantage that it increases the thermal conductivity of bricks. It is undesirable for the thermal conductivity of the lining brick to increase in terms of preventing a drop in the temperature of the molten metal, saving energy, and preventing damage to the shell of the molten metal container. For this reason, conventional measures have been taken such as reducing the proportion of phosphorous graphite and replacing part or all of the phosphorous graphite with amorphous carbon. I was forced to do it.

(Means for Solving the Problems) In order to fully utilize the characteristics of phosphorous graphite, the present inventors have repeatedly studied methods for obtaining bricks with low thermal conductivity without reducing the proportion of phosphorous graphite. Ta. As a result, they learned that the desired purpose could be achieved by adding a heat-dissipating material during the manufacture of bricks to form countless fine voids in the bricks, which led them to complete the present invention.

That is, the present invention has a weight ratio of 1.0 to 10% of fine heat-disappearing substances for a 100% composition containing 3 to 20% of phosphorous graphite as a carbon raw material and the remainder being refractory aggregate. %
This is a method for producing graphite-containing bricks for lining molten metal containers, which comprises adding, kneading, molding, and then drying.

It is common knowledge in the art that the voids in bricks have an insulating effect. This is also the reason why insulation bricks are porous. However, since the voids in the bricks are the cause of a decrease in corrosion resistance due to penetration of molten metal, it has conventionally been thought that it is better for bricks for lining molten metal containers to have a dense structure. Furthermore, no heat-disappearing material was added.

However, in the case of bricks containing a relatively large amount of phosphorous graphite, no decrease in corrosion resistance was observed even when a fine heat-dissipating material was added, and the increase in the amount of phosphorous iA lead actually improved the corrosion resistance and scratch resistance. It was found that polling performance was improved. This means that even if voids are created in the brick structure due to heat-disappeared substances,
If the amount is fine and within a certain range, the molten metal is thought to be prevented from penetrating into the voids due to the property of phosphor-like graphite being extremely difficult to wet with the molten metal.

As a result, according to the present invention, a black button-containing brick for lining with molten metal is obtained, which has both low thermal conductivity obtained by adding a heat-dissipating material to form voids, and corrosion resistance and spalling resistance due to phosphor graphite compounding. be able to.

The present invention will be explained in more detail below. The proportions of each compound and additive below are expressed in % by weight.

Phosphorous graphite is particularly effective in corrosion resistance and spalling resistance among carbon materials. It also has excellent oxidation resistance and filling properties. In the present invention, this phosphorous graphite is
Add 0%. If it is less than 3%, the effect of blending it will not be sufficiently obtained, and if it exceeds 20%, the thermal conductivity will increase.

As described above, it is essential to use phosphorous graphite as the carbon material. However, in addition to phosphorous graphite, graphite other than phosphorous graphite or amorphous carbon may be used as long as the effects of the present invention are not impaired. May be blended. Examples of graphite other than phosphorous graphite include earthy graphite and quiche graphite. Examples of amorphous carbon include pitch coke and carbon black.

When the amount of heat-dissipating material added is large, the number of voids formed by the heat-dissipating material increases, which tends to reduce corrosion resistance, but when phosphorescent graphite and amorphous carbon powder are added, thermal conductivity is low. Due to the presence of the amorphous carbon powder, the amount of heat-disappearing material added, which causes a decrease in corrosion resistance, can be reduced accordingly, and the RJJ corrosion resistance of the bricks is further improved. If amorphous carbon powder is added, the proportion should be 25% or less so as not to inhibit the effect of phosphorous graphite, and the total content of the entire carbon material family including phosphorous graphite should be 30% or less. In this case, the preferred proportion of the amorphous carbon powder is 5 to 20%.

The refractory aggregate is the same as that used in this type of brick, and is mainly composed of one or two selected from alumina, alumina silica, waxite, mullite, zircon, zirconia, magnesia, spinel, etc. do. If necessary, one or more selected from silicon carbide, silicon nitride, clay, etc. may be further combined.

The heat-dissipating material dissipates by melting or burning when the brick is heated during drying or use, forms voids in the brick structure, and makes the brick have low thermal conductivity. The proportion of the heat-dissipating material in the mixture is 1.0 to 10% in terms of outer total. If it is less than 1%, there is no effect of low conductivity, and if it is less than 10%,
If it exceeds this, the brick becomes porous and has poor corrosion resistance. Its shape may be either short fibers or granules. Further, short fibers and granules may be used in combination. The size needs to be fine, for example, short fibers have a diameter of 0.05 to 1.5 cm.
Length 10mm or less, granular materials such as 0.1 to 3 mm
．． Set to 0m.

Specific materials for the heat-disappearing material include short fibers such as natural fibers such as cotton, pulp fiber, hemp, silk, and wool, acrylic fibers, vinylon fibers, polyethylene fibers, vinyl fibers, polyamide IT fibers, acetyl cellulose fibers, It is one or more types of synthetic fibers selected from nitrocellulose fibers, polyester fibers, polypropylene fibers, and the like. The granules are, for example, one or more selected from natural resin particles, paraffin particles, wood chips, fruit powder, etc.
If it is heat-dissipative, it will not leave animals, plants, minerals, or resins. 6 Figure below shows 74% alumina, 7% silicon carbide, and 1 carbon material.
In unburnt bricks manufactured from a blend consisting of 5%, when phosphorous graphite and pitch coke are used together as carbon materials and the proportion of phosphorous graphite is varied (i.e.
FIG. 2 is a graph showing changes in thermal conductivity and corrosion resistance. From this result, it can be seen that as the amount of phosphorus-like black metal added increases, the corrosion resistance improves, but the thermal conductivity also increases5. In bricks, the total amount of carbon raw material is phosphorescent graphite, the amount is changed to 3%, 10%, 15%, and 20%, and acrylic resin granules ('#i diameter 0.48 to 1 225 rrn) is a graph showing changes in the thermal conductivity I scale and the corrosion resistance scale with respect to the addition ratio of the heat-dissipating material. In all cases, the thermal conductivity decreases due to the addition of acrylic resin, and the rate of decrease is particularly steeper for those with a higher phosphorous graphite content.

However, since the pores in the bricks are increased by the addition of acrylic resin, the corrosion resistance tends to be low, especially when the amount of acrylic resin added exceeds 10%. In addition, the range of 3% to 20% of phosphorous graphite is such that if it is less than 3%, the effect of improving spalling resistance, which is the original aim of adding phosphorous graphite, will not be sufficiently obtained, and if it exceeds 20%, the thermal conductivity will decrease. is high and even if acrylic resin is added, the target 2 to 5 Kcal. /
m. hr. This is because a thermal conductivity of 'C or less cannot be obtained.

Note that the methods for measuring corrosion resistance and thermal conductivity were the same as those shown in Examples below.

In addition to the above, in the present invention, one or more types of known additives for carbon-containing bricks, such as metal powder, glass powder, and boron carbide, may be added in appropriate amounts.

Mixing is carried out by adding a binder such as phenol resin, furan resin, pitch, phosphate, or silicate to the mixing ladle in an amount of about 2 to 3%. Shaping is performed using any pressurizing means such as a friction press or an oil press.

Drying is preferably carried out by heating. The heating temperature at that time is preferably 500'C or less from the viewpoint of energy saving. Generally, a temperature of about 100 to 400°C is sufficient.

(Example) Examples of the present invention and comparative examples thereof are shown below.

Each example was prepared by adding 2.5% of phenolic resin as a binder to the mixture shown in Table 1, kneading the mixture, pressure molding it in a flexion press, and drying it at 250°C for 24 hours. Carbon-containing bricks were manufactured.

(1) In the table, the sizes of substances lost on heating are as follows. Vinylon short fibers; diameter 0.2 x length 5llIl Nylon short fibers: diameter 0.5 x length 1.0mm Paraffin particles; diameter 0.1-0.5mm Acrylic spherical particles:
Diameter: 0.48 to 1.225 m (2) In the table, the numbers in parentheses are external multiplication tzt,%.

(Test method) (1) Porosity; Measured according to JIS-R2205.

(2) Corrosion resistance: Measured by a rotary erosion test using pig iron and mixed pig iron car slag as the corrosive agents. 1550℃ x 15 minutes 1
After repeating the test five times, the dimensions of erosion were measured, and Comparative Example 1 was used as a standard.

(3) Thermal conductivity; The thermal conductivity at 120°C was determined by comparison with samples with known thermal conductivity. (4) Actual machine test; some of each example was actually tested on 60
Line the 0t pig iron mixed car and measure the erosion dimensions after use.
Expressed in m/charge.

(5) Spall resistance; 4QX40X230rrn sample 1. After being immersed in pig iron melted in a high frequency induction furnace at 400°C for 3 minutes, it was pulled up and air cooled for 60 minutes. After repeating this process 20 times, the number and size of cracks were determined using Comparative Example ■ as a standard, with 0 being excellent, Δ being the same, and X being inferior.

(Effects of the Invention) Phosphorous graphite has been well known as a fireproof material with excellent corrosion resistance and spalling resistance.

However, due to its high thermal conductivity, its addition to bricks for lining molten metal containers has been naturally restricted from the viewpoint of preventing a drop in the temperature of the molten metal, saving energy, and preventing damage to the steel shell of the molten metal container.

On the other hand, as described above, the present invention provides excellent corrosion resistance by adding an appropriate amount of heat-disappearing material in the production of bricks containing phosphorescent graphite, and also provides fine voids formed by the heat-disappearing material b. This method made it possible to obtain bricks with low thermal conductivity. This effect is unique to the combination of phosphorous graphite and a heat-disappearing material.For example, even if the heat-disappearing material is added, the voids formed by the heat-disappearing material will be reduced if phosphorous graphite is not added. Penetration of molten steel significantly reduces the corrosion resistance of bricks, making them unable to function as a lining for molten metal containers. Due to the above-mentioned effects, the graphite-containing bricks produced by the present invention improve the durability of the lining when lined in a molten metal container without causing a drop in the temperature of the molten metal or damage to the container shell.

[Brief explanation of drawings]

Figure 1 shows the effects of changing the proportion of phosphorous graphite in bricks using both phosphorous graphite and pitch coke.
It is a graph showing changes in thermal conductivity and corrosion resistance. FIG. 2 shows the change in thermal conductivity and corrosion resistance with respect to the addition ratio of the heat-dissipating material in a brick containing phosphorous graphite, using the content of phosphorous graphite as a parameter.昭圆小沉O 0小■ 三CRIO

Claims (4)

[Claims] (1) Phosphorous graphite as carbon material 3 to 20% by weight
%, the balance is 100% of the mixture mainly consisting of refractory aggregate, and 1.0 to 10% of fine heat-disappearing substances are added, kneaded,
A method for producing graphite-containing bricks for lining molten metal containers, which comprises drying after forming. (2) Phosphorous graphite as carbon material in weight proportion: 3 to 20
%, amorphous carbon powder is 25% or less, and the total amount of the above phosphorous graphite and amorphous carbon material is 30% or less, and the balance is based on 100% of the mixture whose main material is refractory aggregate. A method for producing a graphite-containing brick for lining a molten metal container, which comprises adding 1.0 to 10% of heat-disappearing materials, kneading, shaping, and drying. (3) The method for producing a graphite-containing brick for lining a molten metal container according to claim 1 or 2, wherein the material lost upon heating is a short woven fiber and/or a granular material. (4) Short fibers have a diameter of 0.05 to 1.5 mm x length of 10 m
4. The method for producing a graphite-containing brick for lining a molten metal container according to claim 3, wherein the granules have a diameter of 0.1 to 3.0 mm.