JPS6028783B2 - Basic monolithic refractory for molten metal containers - Google Patents

Description

[Detailed Description of the Invention] This invention relates to ladle, external refining furnace, tundish, etc.
The present invention relates to a basic monolithic refractory that is useful as a lining refractory for molten metal containers, mainly for steel manufacturing (hereinafter simply referred to as ladles, etc.).

In recent years, in steel manufacturing, the tapping temperature has increased due to the adoption of continuous casting, degassing treatment, ladle refining, etc. to meet the increasing demand for high-grade steel, and the working temperature of ladle etc. has become higher. The conditions for using ladles, etc. are becoming increasingly severe, such as longer residence times.

For this reason, high-grade refractories such as zircon or high-alumina refractories are now being used in place of the high-grade refractories and acid refractories that have been widely used as refractories for lining ladles, etc. At present, these materials do not have a sufficiently satisfactory service life in terms of slag corrosion resistance. Along with the dramatic increase in service life due to this improvement in slag corrosion resistance, attempts have been made to apply basic refractories to ladles, etc. for the purpose of purifying steel. The excellent effects of basic refractories cannot be utilized due to the occurrence of cracks due to structural sporing and the intrusion of bare metal into these cracks and the occurrence of peeling of the refractories, making it difficult to take advantage of the excellent effects of basic refractories, which have not yet been put into practical use. has not yet been achieved.

In the construction of ladles, etc., there has been a shift from bricklaying construction to irregular-shaped construction using methods such as pouring and vibration molding.

This irregular shape construction is simpler than {1} brickwork construction. '21 The work environment will be improved as there will be no dust generation at the construction site. 3) It is possible to perform additional work during intermediate repairs, and there is no need to discard unused parts with remaining space, as is the case with bricks, which reduces costs. [4] Energy saving is achieved as there is no need for firing during the manufacture of refractories. There are many advantages such as, but the biggest advantage is labor saving by shortening the construction time.

For example, in the case of constructing a 15-melon ladle, conventional brickwork would require three days, but pouring could be completed in just half a day. Therefore, it is thought that it would be optimal to construct the basic refractory into an irregular shape, but the strength of the molten metal container, such as steel casting, made of the basic refractory is lower than that of brickwork, and the volume changes. It has the disadvantage of having a large amount of cracking, poor filling, high thermal expansion characteristic of basic materials, and easy absorption of molten slag, which causes concentrated cracking and peeling.

Various attempts have been made to resolve these issues. For example, reduce the amount of water added in '11. ■
Use a vibrator during pouring work. {3'
Dry construction. These measures have led to some improvement, but they are still insufficient.
As a result of various studies in view of these points, the present inventors focused on the use of coarse particles in order to prevent cracks and peeling that occur in ladles and the like made of basic monolithic refractories.

Japanese Patent Publication No. 56-22835 discloses that alumina-silica coarse grains with a grain size of 4 or less are used in the castable construction of a cement rotary kiln to improve thermal volume stability, abrasion resistance, and strength. It is stated that pumping is possible. Also, Tokusei Showa 53-4
No. 022' describes a method of improving the filling rate, strength, corrosion resistance, wear resistance, etc. by using coarse grains of high alumina cost with a grain size of 10 to 10 m in diameter for refractories for blast furnace iron gutter. .

As a result of a detailed study by the present inventors on the occurrence of cracks in a basic monolithic refractory construction body during heating and cooling, we found that the thermal stress generated within the construction body during heating and cooling propagates particularly through the matrix portion. However, they concentrate on particularly weak points in the organization, leading to large rifts.

However, if coarse grains exist in the construction body, the structure of the coarse grain part is stronger than that of the matrix part in the irregularly shaped construction body, so the propagation of stress is stopped.

However, if the coarse grains are not very large, when the stress propagates to the boundary with the coarse grains, it propagates around the coarse grains. If the coarse grains are larger than a certain level, the propagation of stress will not be able to go around the coarse grains, and the propagation will stop there, resulting in stress not being concentrated at one point but remaining in a dispersed state.

Therefore, although very fine cracks may occur in the matrix, they will not concentrate and become large cracks.
It was found that this did not lead to metal intrusion or peeling. On the other hand, a basic amorphous material is placed in a molten metal container such as a hot pot.
If the construction thickness is more than W rib, it will be 30~
Cracks occur intensively within 50 ribs, and as the steel plates are piled up, the cracks develop significantly and peeling occurs at a thickness of 30 to 5 ribs.

There are very few cracks that occur within 6 feet or more from the operating surface and do not cause peeling.

There are two main reasons for this.

One is that the ladle etc. in operation is heated from 1,000 pm to 1,600 pm.
Rapid heating and rapid cooling are repeated in a range of about 0, and the temperature difference in this thermal cycle gradually becomes smaller as you move closer to the inside than the operating surface, and the temperature difference becomes extremely small within 6 degrees from the operating surface. Another reason is slag intrusion.

Slag infiltration is significant from the operating surface to 30 to 5 feet.
The invading slag reacts with the refractory, resulting in a structure different from the original structure, resulting in structural spalling and spalling.
This invention is a basic monolithic refractory for molten metal containers, which contains 15 to 5% by weight of coarse particles with a particle size of 50 to 9% by weight in a basic refractory material.

By using coarse particles having a particle size of 50 to 9 mm, the thermal stress generated in the matrix portion is prevented from propagating and is not concentrated at one point.

In other words, the cracks that occur intensively inside the 30-5Q proboscis from the operating surface, which are observed in basic irregularly shaped materials with commonly used particle size configurations, can be separated by using coarse particles with a particle size of 50-9Q. This prevents continuous cracks from forming.
Looking at the results of lined refractories actually used in ladles, those using coarse grains with a grain size of 50 to 9 ratios show that fine grains appear intermittently at the boundary between some coarse grains and the matrix part, or at the matrix part. Many cracks occurred, all of which were separated by coarse grains, and there were no continuous concentrated cracks.

This is because the coarse grains have a pinching effect on the entire structure, and because of the fine cracks, there is no intrusion of metal and no peeling occurs.

However, when coarse grains with a grain size of 40 ribs or less are used, the crack splitting effect is small and the catalytic role is not fully exerted, and although it is not as strong as when coarse grains are not used,
The concentration of cracks and the development of the cracks will cause intrusion and peeling of the base metal, and if the grain size is 9 mm or more, the fluidity during construction will be poor and there is a possibility of grain separation, which is undesirable. In the invention, the particle size of the coarse particles must be in the range of 50 to 9 mm. However, it is also possible to use coarse grains with a grain size of 5 m or less. As described above, in the present invention, coarse particles having a grain size of 50 to 9 molar diameter are contained in the basic refractory material in an amount of 15 to 5% by weight, preferably 25 to 4% by weight, and the content of the coarse particles is If it is less than 15% by weight, the number of coarse grains is too small and the cracks cannot be divided sufficiently, resulting in concentrated cracks and intrusion of the base metal and peeling. If it is not sufficient, grain separation tends to occur, which is undesirable.

In this invention, the basic refractory material refers to known materials such as magnesia IJ linker, dolomite clinker, magnesia spinel clinker, magnesia clinker, and magnesia silica, and the total content of Mg0 and Ca○ is 5. % by weight or more is preferable. This is 5% by weight
This is because the corrosion resistance of the basic material against slag is significantly lost below. MgO and Ca○ in this basic material
Other components include Si02, A〆203, Zh]2
, Ti02, Cr203, etc., as long as they do not react with Mg0 or Ca◯ to lower the melting point or significantly deteriorate other properties. The coarse grains used in this invention do not react with components other than the coarse grains to form low-melting substances or reduce slag corrosion resistance, and the compressive strength of the coarse grains is preferably 300 kg/cm or more, preferably 500k9/
It is necessary to have a porosity of 20% or less, which is equal to or higher than that of carp.

This is because if the compressive strength is less than 300k9/average, the coarse grains themselves may crack due to thermal stress, or cracks that occur in the matrix may not be stopped, and if the porosity exceeds 20%, slag may invade. This is because it becomes easy and undesirable.

Next, methods for producing the coarse particles used in this invention include a method in which raw materials are blended in particle size by a known brick manufacturing method, a binder is added, kneaded, molded, and fired, and then coarsely crushed and divided; Various methods are used, such as granulating it with a granulator or other method and using it as is, or burning natural magnesite ore as it is, coarsely crushing it, and dividing it into sections, as long as they satisfy the above conditions. However, it is not particularly limited.

In addition to the coarse particles of the basic monolithic refractory according to the present invention, what particularly affects the workability, properties, etc. is the powdery part (grain size 0.125 or less).

The amount of this powder to be used is adjusted by the amount of coarse particles used, but it is preferably used in an amount of 25 to 35% by weight of the refractory material raw material. In addition to refractory materials, binders, water reducers, dispersants, defogizers, explosion prevention agents, thickeners, and other materials normally used for monolithic refractories may be used as appropriate.As binders, Hard or thermosetting substances include, for example, aluminum phosphate, alumina cement, poppy, acid soda, magnesia cement, aluminum sulfate, clay, and ethyl silicate. Phosphates, poppy seeds, acid salts, sulfonic acid compounds, etc. are used as water reducers, dispersants, defogants, and various surfactants are used as explosion prevention agents.

If appropriate amounts of these substances are used, the viscosity of the bond part will be relatively high in case of pouring construction, and particle separation due to sedimentation will not occur even if coarse particles are used. However, when using a vibrator, known pulp waste liquid, silica gel , Kushi, CM
By adding a small amount of a thickener such as C, sodium alginate, or PVA, sedimentation of coarse particles can be prevented. The basic monolithic refractories containing coarse particles according to the present invention may be constructed by known construction methods such as pouring, stamping, and vibration molding, but among them, the pouring method is the most suitable. preferable. In the case of this pouring construction, coarse particles, other refractory materials, binders, and other additives are weighed and mixed using a mixer that does not involve compression as much as possible, such as a vortex mixer, mortar mixer, or cement mixer. Add 5-8% of the solid content, strain for 3-2 minutes, and pour into the mold.

The curing time until demolding depends on the temperature, but it is 0.5 to 4
About an hour is preferable. It is then dried at elevated temperatures and used. The basic monolithic refractory using coarse particles according to this invention is
In particular, it is used as a refractory lining material for ladles, etc. that are used at high temperatures. This prevents corrosion during use and fully demonstrates the slag corrosion resistance characteristics of basic materials.

At the same time, by using coarse grains, the heat-induced volume stability of the refractory layer, the wear resistance of molten steel, and the strength due to the aggregate effect can be combined, and the advantages of basicity and irregularly shaped materials can be fully utilized.

The present invention will be explained in detail with reference to Examples below.

Example 1 (Manufacture of coarse grains) Magnesia dolomite clinker having the composition shown in Table 1 was blended with a grain size, 3% of water was added, and mixed in a wet pan.
After being molded into a regular brick shape using a 5-press press, it was fired at 1580 qo in a tunnel kiln.

The apparent porosity of the brick after firing is 11% and the compressive strength is 98.
It was 0k9/th. The bricks were crushed with a jaw crusher and divided into 90-5 ribs and 50-5 ribs. Table 1 Examples 2 to 4 Insulating bricks with a thickness of 114 meters were built inside an iron container with a diameter of 1.5 meters and a height of 0.8 meters, assuming a ladle, and a layer of 20 meters thick was built in the center. A steel core was installed so that

Coarse particles, magnesia dolomite clinker, and binder having the composition shown in Table 2 were mixed in this container using a vortex mixer, water was added, and the mixture was stirred for 3 minutes, followed by pouring the material.

After being left for 2 hours, the core was removed and immediately heated to 1000 pm using an oxygen-propane burner at an overflow rate of 100 oo/hr.
Stripes appeared and the mixture was kept for 3 hours and then allowed to cool.

After cooling, the state of cracks was measured.

The temperature was raised again to 1600 oo at a heating rate of 100 oo/hr and maintained for one field hour. Ladle slag having the composition shown in Table 1 was hot sprayed.

This spraying cooled the furnace to about 1,000 qo, so the temperature was raised again to 1,600 qo at 100 qo/hr. This operation of slag spraying and temperature raising was repeated five times, and then cooled. After cooling, the state of cracking and peeling of the constructed body was observed. The results are shown in Table 2. Comparative Examples 1 to 4 Experiments were conducted using pouring materials with different compositions such as coarse particles in exactly the same manner as in Examples 2 to 4.

The results are shown in Table 2. Table 2 As is clear from the results in Table 2 above, the pouring material containing 15 to 5% by weight of coarse particles with a particle size of 50 to 9 mm causes only microcracks and no peeling. No outbreak was observed.

However, if the amount of coarse particles used in 50 to 9 degrees is small, or if the particle size is less than 5 degrees, or if no coarse particles are used at all, large cracks will occur intensively, and the cracks will It also reaches from the top to the bottom of the container and from the operating surface to the back.
It was accompanied by peeling. -This recognized the excellence of this invention.

Example 5 The pouring material of Example 3 was applied to a ladle with a thickness of 18 mm.As a result, there were no concentrated cracks, and there was no penetration of the base metal into the material or peeling. This did not occur, and the durability was twice as long as when the material of Comparative Example 3 was used.

Claims (1)

[Claims] 1. A basic monolithic refractory for molten metal containers, which is made by blending 15 to 50% by weight of coarse particles with a particle size of 50 to 90 mm in a basic refractory material.