JPS5845173A - Lining material for dielectric melting furnace - 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 The present invention relates to a lining material for an induction melting furnace, particularly having spalling resistance. This invention relates to a zircon-based finning material that has excellent corrosion resistance and can be used as a stamp material in induction melting furnaces.

In an induction melting furnace, the material to be melted is charged into a crucible made of refractory material, and an alternating current is passed through an induction coil wound around the crucible, causing the material to be heated and melted by Joule heat generated by electromagnetic induction. However, in high-frequency induction furnaces for melting cast steel, which require intermittent operation, partial tapping, and large temperature fluctuation operations, rapid heating and cooling occur repeatedly, which is extremely harmful to the refractory materials (lining materials) that make up the crucible. As a result, hot water leakage accidents due to spalling (cracking) and local erosion (erosion) due to molten steel and rust have become major problems.

Conventionally, as such refractory materials, magnesia-based materials have been mainly used, but silica-based materials have also been used to some extent.These refractory materials are pounded and hardened (nutampu) and then placed in a crucible inside the coil. The dissolution chamber is formed by a method such as molding. However, although such conventional magnesia-based refractories have the advantages of high fire resistance and good corrosion resistance, they have the disadvantage of large thermal expansion and cracking due to spalling, and the aforementioned hot water leakage. The risk of an outbreak always exists. On the other hand, silica-based refractories have high thermal expansion, which causes problems such as cracking due to spalling, and melting due to molten steel/nurag.
Loss is a major problem, which limits its use.

On the other hand, zircon (ZrO, I-Sin, 2) belongs to weakly acidic refractory materials, but it is cheaper than zirconia (Zr02), can withstand use up to 1750°C, and has no transformation, so it has a low volume It has the advantage of little change, and although it has the problem of slightly low electrical resistance, it is suitable for induction melting furnaces due to its low thermal expansion coefficient, low heat transfer coefficient, and high thermal shock resistance. Although the use of zircon refractories in induction furnaces has been proposed in various ways, in reality, there are no actual examples of zircon refractories being used as refractories in induction melting furnaces. Not reported. Although its excellent characteristics have been recognized, the reason why it has not actually been used as a refractory material for induction melting furnaces is that conventional zircon refractories suffer from significant erosion and wear and tear. This is because cracking occurred due to poling, and its advantages could not be fully demonstrated compared to magnesia refractories.

゛Here, the present invention has been made against the background of such circumstances, and its purpose is to solve the problems with the conventional zircon refractories and to improve them compared to magnesia refractories. It can exhibit superior characteristics. The purpose of the present invention is to provide a lining material for induction melting furnaces that has excellent spalling resistance and corrosion resistance.

In order to achieve such an objective, the present invention provides 1μ
The following ultrafine particles are 1~. 10% and 1000-6000
Large μ particles account for 40-60%, and the remaining 1-1000
Zircon particles consisting of particles of μ and n are used as a zircon refractory component, and a lining material for an induction melting furnace is made of zircon particles having such a particle size.

That is, the lining material (refractory material) according to the present invention
Because it is essentially a zircon refractory, it has sufficient fire resistance, poor electrical conductivity, low coefficient of thermal expansion, low heat transfer coefficient, and high thermal shock resistance. Of course, the presence of a certain amount of zircon particles with a large particle size of 1000 to 6000μ ensures sufficient refractory strength to mechanically withstand bridges, etc., and to withstand intensely stirred molten steel flows and high temperatures. By incorporating ultrafine zircon powder of 1μ or less, the structure is made denser, and the porosity is significantly reduced from the conventional 82-34% to about 20-24%, and the water absorption rate is also lower than the conventional one. 12% to 6
%, thereby reducing the infiltration of nlug and the formation of low melting point compounds, thereby significantly suppressing their melting loss. Also, along with this,
It shows good durability against sudden temperature changes caused by tapping and charging operations, as well as sudden temperature gradients inside the lining, which has a water-cooled outer wall and is thin.
were also effectively suppressed.

As a result of these effects, an induction furnace formed using the lining material according to the present invention has significantly improved durability compared to conventional magnesia-based lining materials.
This resulted in white clay having a lifespan approximately 2 to 8 times longer.

By the way, among the zircon (ZrO2.'SiO,,) particles constituting the lining material according to the present invention, those with a large particle size of 1000 to 6000μ have a diameter of 4
It is necessary to adjust the ratio to be 0 to 60% (weight ratio; the same applies hereinafter). By being present in a proportion within this range, a refractory material (lining) that exhibits sufficient strength for use in induction melting furnaces can be obtained, and when the large-sized zircon particles are less than 40%. However, it cannot be used as a lining for induction melting furnaces even though it can be made with a lining of sufficient strength. In addition, in cases where the porosity exceeds 60%, the porosity of the lining to be formed may be increased and the object of the present invention may not be fully achieved. The incorporation of ultrafine powders causes problems in the tambing operation f'14 for forming the lining in the induction melting furnace.

In addition, in order to make the lining structure dense and reduce the porosity, it is necessary to contain at least 1% or more of zircon ultrafine particles with a particle size of 1 μ or less in the zircon particles. That is, if the ratio exceeds 10%, the degree of filling will increase significantly, and the porosity will become extremely small, causing problems such as spalling to occur again. Therefore, ultrafine powder of 1μ or more is 1 to 10μ in order to achieve the purpose of the present invention.
It has to be adjusted so that the ratio is %.

The remaining silicon particles, excluding particles with two types of particle sizes, large particle size and ultra-fine particle size, are those with an intermediate particle size of 1 to 1000μ. During the stamping operation, it is interposed between the large diameter particles and the ultrafine particles to effectively increase their filling degree and form a desired porosity range of about 20 to 24%. It's easy to do. In particular, among the zircon particles with a particle size in this intermediate range, the proportion of those in the 1 to 100 μ range is 10 to 80% of the total zircon particles,
If the remaining portion is in the range of 10.0 to 1000 μm, it becomes possible to form a lining having more desirable characteristics.

A zircon particle according to the present invention having such a particle size distribution is generally produced by using zircon sand as a starting material,
It can be easily prepared by pulverizing it using various types of pulverizers, or by suitably blending the obtained pulverized products of various particle sizes to adjust the particle size. It can also be produced by solidifying the finely pulverized material with glue, firing it, and pulverizing the resulting ingot to adjust the particle size.

In the present invention, zircon particles having such a particle size distribution are used as a zircon refractory component (baked), and a predetermined binder such as sodium silicate, boric acid, or borax is mixed therein according to a conventional method. The zircon particles to which the binder has been added are pounded and hardened in a moist state (in the presence of water), and then molded into a crucible in an induction melting furnace.

In other words, a lining that is in contact with the melt is formed inside the coil. In addition, the zircon particles having a specific particle size distribution according to the present invention can be directly pounded and solidified according to a known dry method and used as a lining for an induction heating furnace.

As described above, the lining material containing zircon particles with a specific particle size distribution as a refractory component according to the present invention is particularly useful as a stamping material for forming a lining in an induction melting furnace by the stamping (pounding and hardening) method. By using the lining material according to the invention, it has been possible to significantly improve the spalling resistance and erosion resistance, thereby significantly improving the service life of the induction melting furnace.

In particular, the lining material according to the present invention is extremely useful as a refractory material in high-frequency induction furnaces that are exposed to extremely severe conditions.

Examples of the present invention will be shown below to clarify the effects of the present invention in more detail, but it goes without saying that the present invention is not limited in any way by the description of such implementations.

In addition, percentages and parts in the examples are limited unless otherwise specified.
All values are based on weight.

EXAMPLE Eight types of primary lining materials (A, B, 0) were used for various tests.

- Lining material A (present invention) - Siyvcon particles = 1μ or less ......
4%1~100μ ・・・・・・28%10″-
108μ ・・・・・・・・・28%108~6X10
8μ...40% - Lining material B (comparative example) - Zircon particles: 1 to 10''μ...4
0%102~103μ ・・・・・・80%10
3～6×108μ・・・20%6×108μ
Above......10% - Lining material C (comparative example) - Commercially available magnesia refractory material (a) Slag wet test Using the above eight types of lining materials, binder; sodium silicate mixture Below, a crucible-shaped test piece (outer diameter 10011 m
, height 80 wtm; inner diameter 8 (1 (bottom) to 40 (top)
8. Depth 80'')
Fifty parts of induction furnace generated slag having the composition shown in Table 1 above was housed in each piece, and a comparative test of slag infiltration was conducted. In addition, after each test beef contained slag, it was held in an electric furnace for 8 hours at 1500'C.

Chapter 1 Table Slag wetness test using crucible method like this.

'As a result, as shown in Table 2, in the test beef obtained from lining materials B and 0 for comparison, slag infiltration was very large, especially in the case of lining material C. It was observed that the slag wetting was extremely large, passing through the matrix of the refractory structure and reaching the outside. In addition, in the case of lining material B, broaching due to refractory and low melting due to slag was observed.

As a result, lining material B, which is made of zircon particles that do not contain ultrafine particles of 1 μ or less, is weak against erosion, and lining material C, which is made of magnesia, has a remarkable tendency to structural spalling due to slag infiltration. In the n number test, lining material A according to the present invention was judged to be the most superior.

Table 2 [Stock]: Value when lining material A is set as 100.

(b) Small induction furnace lining corrosion test Test beef made of each of the above lining materials for the lining of a small induction furnace,
(4 (IIX 4011

In addition, in this test, t, ac-50u-85O
A comparison was made between steel types with the following compositions: r-85N i-8Mo. The dissolution conditions are shown in Table 8.

Table 8 As a result of the erosion test, the test piece formed from the lining material B for comparison showed a large erosion amount of 18.1 wtm, whereas the test piece formed from the lining material A according to the present invention showed a large erosion amount of 18.1 wtm. , the amount of erosion was merely 7.2 mm, and it was judged that the erodibility was significantly improved.

(e) Actual furnace application results T Inning materials A, B, and Ck were each used as Nutande materials, and were heated in a 600Kg high-frequency induction furnace at 250K using the wet method.
g High frequency induction furnace, fining of 200Kg Sirinuta induction furnace was formed by Nutamping. In addition, as a binder, 1.0% of sodium silicate and 2.0% of water were used.

Actual furnace operations were performed on furnaces equipped with refractories made of different lining materials, and the number of service lifespans, power consumption, etc. were determined, and the results are shown in Tables 4 and 5. Indicated.

Table 4: 250Kg, 600Kg Furnace Table 5: 20oKg Thyristor induction furnace As is clear from the results in Tables 4 and 5, compared to the comparative zircon lining material B and magnesia lining material C,
It was found that the lining material A according to the present invention exhibited approximately 2 to 8 times more service life and significantly improved the lifespan of refractories. Furthermore, in terms of power consumption, the furnace lined with lining material A according to the present invention is one made of magnesia (0
), it was found that an improvement of 5 to 10% was widely achieved.

Regarding the improvement of this electricity consumption rate. Although a clear theoretical analysis has not yet been carried out, the thickness of the sintered and metamorphosed layer of zircon is less than half that of magnesia, so it is possible to use a thinner lining. It is thought that this is due to differences in thermal conductivity.

In addition, all induction furnaces formed using the zircon lining material A according to the present invention have significantly less melting damage than those formed using the lining material B, and those made using the lining material C. It was found that there was a significant difference in spalling resistance compared to the previous model, and it was found that the hot water leakage accidents were almost completely eliminated.

Applicant: Daido Steel Co., Ltd. Same Tokyo Ceramics Co., Ltd.

Claims (2)

[Claims] (1) 1 to 10% particles of 1μ゛・or less and 1000 to 100%
6000μ particles account for 40-60% and the remainder 1-100%
A lining material for an induction melting furnace, characterized in that it contains zircon particles composed of 0μ particles as a zircon refractory component. (2) Among the zircon particles with a particle size of 1 to 100μ, those within the range of 1 to 100μ account for 10 to 80% of the total zircon particles, and those within the range of 100 to 1000μ account for the remainder. A lining material according to claim 1.