JPH01197370A - Monolithic refractory for lining molten metal vessel - Google Patents

Abstract

PURPOSE:To prevent the cracking and peeling of a cast product and to allow a refractory to exhibit superior corrosion resistance by using aggregate consisting of alumina- and spinel-based heat resistant starting materials. CONSTITUTION:A blend of 60-95 pts.wt., preferably 50-85 pts.wt. heat resistant starting material based on alumina such as electromelted or sintered alumina with heat resistant starting material based on spinel such as high purity electromelted or sintered spinel is used as aggregate and an inorg. binder such as high alumina cement or colloidal silica and a dispersant such as phosphate are added to the blend to obtain the title refractory.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a monolithic refractory for lining the inner surface of a molten metal container, and particularly to a monolithic refractory that exhibits less cracking and peeling when formed by a pouring method, and has excellent corrosion resistance. The present invention relates to a lining material composition for a molten metal container that exhibits the following properties.

[Prior Art] Conventionally, as monolithic refractory materials for ladle lining, waxite, waxite-zircon, silica-zircon, zircon, etc. have been mainly used.

On the other hand, in recent years, with the adoption of vacuum degassing methods and continuous casting methods, and further improvements in ladle refining technology, high-grade steels have come to be refined in ladle. For this reason, processing conditions in the ladle have become increasingly severe, as exemplified by the need to carry out argon stirring, alloy addition, vacuum treatment, etc., as well as increased molten steel temperature and extended molten metal residence time. ing. However, the conventional general-purpose materials mentioned above cannot cope with these harsh conditions, and the life of the ladle is significantly reduced. Due to the large amount of components flowing out from the refractories due to the erosion of the ladle,
Deterioration of steel quality, such as contamination of molten steel and increase in inclusions in steel, is becoming a problem.

In order to solve the above-mentioned problems with conventional materials, materials such as alumina, spinel, Magdrome, and Magcarbon have been tried, but no satisfactory results have been obtained with any of them.

[Problems to be solved by the invention] First, in alumina materials, the penetration of slag into the structure is large and structural spalling occurs, and the corrosion resistance of high basicity slags is significantly reduced due to chemical attack. There are other problems. Furthermore, although spinel and maguro materials have excellent corrosion resistance, they have a problem of poor thermal spalling resistance due to their high hot linear expansion. Furthermore, carbon-containing materials, such as magcarbon, have excellent heat resistance and ffT impact resistance, but in addition to picking up carbon into steel,
Decrease in corrosion resistance due to consumption of carbon due to eO slag and high 02 level steel types, remarkable drop in molten steel temperature due to high thermal conductivity (heat dissipation), foul odor and smoke during drying due to the use of organic binders, and problems with the back side (lining). There are problems such as brittle deterioration due to oxidation on the iron skin side of the layer.

[Means for Solving the Problems] The present inventors grasped the low hot linear expansion and low thermal conductivity of alumina and the slag erosion resistance of spinel as advantages,
In addition, spinel makes up for the drawbacks of alumina, which has high slag permeability and tends to cause structural spalling, while alumina makes up for the drawbacks of spinel, which has high hot linear expansion and tends to cause thermal spalling. By using both in combination, we have completed a monolithic refractory for lining molten metal containers that has excellent spalling resistance and corrosion resistance. That is, the gist of the present invention is to contain as an aggregate a composition consisting of 50 to 95 parts by weight of a heat-resistant raw material containing alumina as a main component and 50 to 5 parts by weight of a heat-resistant raw material containing spinel as a main component. be.

[Function] In ladle operation, heating and cooling are repeated. Therefore, the material may show a tendency to shrink due to slag absorption or self-sintering, and in such cases, cracks are likely to occur, allowing metal to enter through the cracks, resulting in peeling of the lining. Therefore, it is desirable to obtain a material with excellent crack resistance and peeling resistance as a ladle lining material.
It is also important to reduce the hot linear expansion coefficient of the material itself. In this regard, when only alumina-based raw materials are used as the main aggregate, the thermal spalling resistance is excellent due to low hot linear expansion, but as mentioned above, structural spalling occurs due to poor slag penetration resistance. Easy to do. On the other hand, when only spinel raw materials are used as the main aggregate, structural spalling is less likely to occur, but thermal spalling is more likely to occur. The main point of the present invention is to skillfully combine the advantages and disadvantages of both.

The alumina-based raw material to be used is preferably one that contains few impurities and has been treated at a high temperature, such as fused alumina, sintered alumina, or calcined alumina. Natural bauxite and pansoil shale contain a large amount of impurity components such as Sin and TiO2, and therefore have poor corrosion resistance, but are low in cost and can be used in some cases. Commercially available high-purity fused spinel and sintered spinel are recommended as spinel raw materials. However, contamination with impurities cannot necessarily be excluded. Therefore, in the present invention, the term "heat-resistant raw material containing alumina or spinel as a main component" is adopted. Although these heat-resistant raw materials are used after being crushed, they are generally prepared by dividing them into relatively large particles and relatively small particles in order to reduce the porosity during mixing. Therefore, each raw material is divided into two types of particle sizes, but it is also possible for one raw material to have mainly large particle sizes and the other raw material to have small particle sizes, in which case spinel is the main component. In the case of slag, it is desirable to increase the fine particle content in view of the purpose of improving the penetration resistance of the slag.

The blending ratio of alumina-based raw materials and spinel-based raw materials is 50 to 95 parts by weight out of 100 parts by weight of both! i
parts by weight, and the remaining 50 to 5 parts by weight is spinel-based raw material. A more preferable ratio is 50 to 85 parts by weight of the alumina-based raw material. If the alumina-based raw material is less than 50 parts by weight, the hot linear expansion coefficient becomes large due to the spinel-based raw material, resulting in poor poling durability. On the other hand, if it exceeds 95 parts by weight, durable lag permeability and corrosion resistance will decrease.

A monolithic refractory is manufactured by forming an aggregate using the above-mentioned Z fit raw materials and adding a third component generally referred to as an outer layer. First, it is desirable to use a conventionally used inorganic binder as the binder. As mentioned above, the use of organic binders not only causes bad odor and smoke when drying, but also causes deterioration due to oxidation on the back side.
In more detail, the binders to be used, which are undesirable because they have disadvantages such as making joint repair impossible, are: high alumina cement, sodium silicate, colloidal silica, amine silicate, alumina sol, sodium phosphate, g! Aluminum 4-acid, modified aluminum phosphate, etc. can be used.

[Examples] Examples 1 to 3 Aggregates for pouring materials of the present invention were manufactured using sintered alumina and sintered spinel at the mixing ratios (parts by weight) shown in Table 1.

To 100 parts by weight of the above refractory raw material aggregate, 3 parts by weight of vaporized silica as a binder, 2 parts by weight of high alumina cement, and 0.1 part by weight of phosphate (dispersant) are mixed.
An appropriate amount of water (an amount that can be adjusted to a flow value of 180 to 190) was added, and after kneading, the mixture was poured into a metal frame measuring 40 mm x 40 mm x 160 mm. 24 hours at a temperature of 20℃ and a humidity of 90% or higher.
After curing for an hour, it was dried at 105° C. for 24 hours and used for testing.

Table 1 shows the results of the performance test of the obtained pourable material of the present invention.

Comparative Examples 1 and 2 Comparative pouring materials were manufactured according to the examples and subjected to performance tests. The results are shown in Table 1. The test method was as follows.

(1) Physical properties (apparent porosity) of the sample after drying and the sample after firing at 1500°C for 3 hours in an electric furnace.

Bulk specific gravity) was measured.

(2) The strength characteristics (bending strength) of the sample after drying and the sample after firing at 1500° C. for 3 hours in an electric furnace were measured.

(3) The linear change rate after firing at 1500° C. for 3 hours in an electric furnace was measured.

(4) The hot linear expansion coefficient up to 1000° C. was measured using a thermal expansion measuring device.

(5) A corrosion resistance test was conducted at 1650° C. for 2 hours using a rotary drum type erosion test using converter slag, and the erosion depth and infiltration depth were measured.

(6) The sample was inserted into an electric furnace maintained at 1000° C. for 10 minutes, and then air-cooled for 10 minutes, a cycle repeated, and the number of times until cracking occurred was determined.

From the above results, it can be seen that the casting material of the present invention has excellent corrosion resistance and durable poling property compared to conventional alumina-based and spinel-based materials.

[Effects of the Invention] Since the monolithic refractory for lining molten metal containers of the present invention is configured as described above, it has excellent durability and poling property compared to conventional alumina-based or spinel-based monolithic refractories. It has corrosion resistance and is ideal as a refractory lining for various types of smelting furnaces, including ladles.

Claims (1)

[Claims] 50 to 95 parts by weight of a heat-resistant raw material containing alumina as a main component,
A monolithic refractory for lining a molten metal container, comprising as an aggregate a composition consisting of 50 to 5 parts by weight of a heat-resistant raw material containing spinel as a main component.