JPH05117043A - Dry ramming refractory for induction furnace - Google Patents

Abstract

PURPOSE:To obtain a lining material having better durability and prolong the life of an inner lining of an induction furnace in a dry ramming material for the inner lining of the induction furnace. CONSTITUTION:A dry ramming refractory for an induction furnace is characterized by blending 0.3-5.0 pts.wt. zirconium compound powder such as zirconium carbonate or zirconium hydroxide with 100 pts.wt. refractory aggregate containing one or more raw materials in an alumina, a magnesia and a spinel raw materials.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to a dry ramming refractory material for linings of low frequency and high frequency induction furnaces.

[0002]

2. Description of the Related Art Conventionally, a siliceous dry ramming refractory material having a controlled grain size has been generally used as a lining material for low frequency and high frequency induction furnaces. First, a steel core is installed in the induction furnace, and a dry ramming refractory material is dry-filled by a vibrator, etc. between the steel core and the iron shell of the induction furnace. The refractory material was induction-heated together with the steel core and used as an integrated refractory lining layer. As a conventional dry ramming refractory material, there is a refractory material composed of silica stone and boric acid whose particle size is adjusted. The refractory lining layer that uses this refractory material is sintered only on the operating surface that is in contact with molten steel during furnace operation, and on the back side of the furnace refractory lining layer is a powdery unsintered layer. . Therefore, even if a crack occurs on the operating surface that contacts molten steel,
Since the crack did not extend to the back side of the refractory lining layer of the furnace, the furnace could be continuously operated. However, in recent years, when melting of special cast steel of high temperature operation is started in induction furnace, its durability becomes insufficient with the above-mentioned siliceous dry ramming refractory material, and alumina, magnesia, spinel, alumina- Refractory materials such as magnesia and alumina magnesia spinel have come into use.

[0003]

The refractory materials such as alumina, magnesia, spinel, alumina-magnesia and alumina magnesia spinel which have been used in recent years have high corrosion resistance and high fire resistance. Since there is little melting loss due to molten steel, on the other hand, it is inferior in thermal shock resistance, and in the case of intermittent operation of the furnace, the refractory lining layer cracks during operation of the furnace, and the thickness of the refractory lining layer is sufficient. Nevertheless, there was a problem that the use had to be stopped. The reason is that the refractory material such as alumina, magnesia, spinel, alumina-magnesia and alumina-magnesia-spinel has high thermal conductivity, and not only the working surface during use but also sintering to the back layer. Proceeds and creates a solid monolithic layer,
There was a serious defect that once the crack had developed, the crack had propagated to the back surface and the molten steel had penetrated through the crack to the back surface of the refractory lining layer. In order to solve the above problem, a method of suppressing the sintering by using alumina and magnesia activated ultrafine powder, which uses a high-purity material, and the reaction of alumina and magnesia to expand and suppress sintering has been attempted. The effect was not sufficient.

[0004]

Means for Solving the Problems The present invention has conducted extensive studies on the above problems, and as a result, at a temperature lower than the reaction temperature of alumina and magnesia, zirconium oxide of Focusing on a large volume change, and by adding zirconium carbonate, zirconium hydroxide, or other zirconium hydroxide, which produces active zirconium oxide upon heating, to the dry ramming refractory material, sintering of the refractory material can be suppressed. I thought. That is, in the present invention, 0.3 parts of zirconium compound powder such as zirconium carbonate and zirconium hydroxide is added to 100 parts by weight of a refractory aggregate containing at least one raw material among alumina raw materials, magnesia and spinel raw materials.
It is a dry ramming refractory material for an induction furnace, characterized by being mixed in an amount of up to 5.0 parts by weight.

[0005]

The function of the alumina raw material in the present invention is alumina 9
Any of 5.0% or more can be used, and an electromelted product is particularly desirable. As the magnesia raw material, any ordinary material can be used, and particularly, magnesia of 95.0% or more is desirable. As a spinel raw material, the Mgo / Al ₂ O ₃ ratio is 5/95
~ 50/50 and other than magnesia and alumina 5.
Any content of 0% or less can be used, and an electromelted product is particularly desirable. The refractory aggregate may be any one of alumina raw material, magnesia and spinel raw material as long as it contains one or more raw materials, but the composition of alumina, magnesia and spinel is 60 to 95 parts by weight of alumina, magnesia. 5
Spinel 3 to 3 for 100 parts by weight of -40 parts by weight
The composition with 0 part by weight added is particularly excellent in durability.

The particle size of the refractory aggregate is 5 to 1 mm:
30-50 parts by weight, particle size 1-0.074 mm: 20-40
By weight, -0.074 mm: 20 to 40 parts by weight is typical, but when the alumina raw material is 80 parts by weight or more, the magnesia raw material is blended with fine powder of 0.074 mm or less, and the magnesia raw material is When the amount is 50 parts by weight or more, it is desirable to mix fine particles of 0.074 mm or less as the alumina raw material. The zirconium compound powder may be a commercially available one, but zirconium carbonate ZrOCO ₃ .nH ₂ O and zirconium hydroxide ZrO (OH) ₂ .nH ₂ O are particularly preferable. The amount of zirconium compound powder added is preferably 0.3 to 5.0 parts by weight, based on 100 parts by weight of the refractory aggregate.
If it is less than 3 parts by weight, there is no effect, and if it exceeds 5.0 parts by weight, the zirconium compound powder is a thermally unstable raw material, so that the corrosion resistance of the refractory material is significantly lowered. The dry ramming refractory material of the present invention can be easily manufactured by an Erich mixer, can be applied to the lining of an induction furnace by a conventional method, and can be used as a fire lining layer by induction heating.

[0007]

[Examples] Table 1 shows the raw material blending of the samples of Examples and Comparative Examples, the results of the sinterability determination test and the spooling test.

[0008]

[Table 1]

The test methods for the sinterability determination test and the spooling test will be described below. Sintering degree determination test For the sintering degree determination test, the rotary erosion method which is commonly used for the corrosion resistance test of refractory materials was adopted. The sample consists of two large and small pipes (diameter 100 mm and 200 mm, length 1
(00 mm) was installed, and the ramming material was vertically filled between the two pipes to manufacture. The inner pipe was heated and melted and removed during the test. C / S = 1, Fe ₂ as corrosive material
Heated at 1600 ° C. for 3 hours using 20% O ₃ slag. After the test was completed, the sample was cut in the lateral direction together with the outer pipe, and the melt loss thickness and the thickness of the sintered layer (consolidated portion on the working surface side that was not in the powder state) were measured. Spooling test The sporing test was performed according to the sintering degree determination test.
However, as the lining method of the ramming material, a method of horizontally filling the ramming material (in layers) was adopted. Test 1650 ℃
The cycle of heating for 1 hour at 30 ° C. and air cooling for 30 minutes (the temperature is lowered to 500 ° C.) was repeated 20 times. After the test, the sample was divided into pieces and the state of crack generation was determined.

In Examples 1 to 4 in Table 1, zirconium carbonate or zirconium hydroxide was added to the main raw materials (alumina, magnesia, spinel), and Comparative Example 1
Is a main raw material only, and Comparative Example 2 is a conventional siliceous raw material. In the corrosion resistance test, since Comparative Example 2 is a silica stone,
The erosion thickness was more than twice that of the example. Comparing Examples 1 to 4 with Comparative Example 1, the erosion thickness does not change much, but the thickness of the sintered layer is different from that of Comparative Example 1 in Example 1.
.About.4 is as small as 1/4 to 1/5. Therefore, in the example, the sintering is suppressed and the thickness of the sintered layer is smaller than that of the comparative example. Excellent anti-spooling property.

[0011]

As a result of using the dry ramming refractory material for an induction furnace of the present invention as the lining of a 1t high frequency induction furnace, the life of the lining of the furnace is more than twice as long as that of the conventional siliceous dry ramming refractory material. Extended.

Claims (1)

[Claims] 1. A zirconium compound powder such as zirconium carbonate or zirconium hydroxide is added in an amount of 0.3 to 5. with respect to 100 parts by weight of a refractory aggregate containing one or more raw materials among alumina raw materials, magnesia and spinel raw materials. A dry ramming refractory material for an induction furnace, characterized by containing 0 part by weight.