JPS61222954A - Manufacture of limy crucible - 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 "Object of the Invention" The present invention relates to a method for producing a lime-based crucible, which is suitable for refining ultra-low sulfur steel with a sulfur content of 10 ppm or less. The aim is to provide a method that can accurately obtain the

Industrial applications Manufacturing technology for lime-based crucibles suitable for refining ultra-low sulfur steel.

BACKGROUND OF THE INVENTION As the demand for ultra-clean steel has increased in recent years, induction melting furnaces have been significantly developed, and with the increase in the internal volume of the furnace and rapid melting technology using high output, productivity has significantly improved.

However, in general, the operation of induction furnaces does not generate as many hot spots and slag as in arc furnaces, so the requirements for refractories are not very strict.
is formed around the outside of the furnace body 11 having a lining 12, and includes a ground antenna 13, a dedicated cooling coil 14, a yoke 16, a furnace lid 17 . A water passage part 8, a current supply part 9, etc. are arranged as shown in the figure, and the produced molten metal is discharged from the tapping port 21. The chemical composition of such refractory materials for electric induction furnace melting is shown in Table 1 below, and each has performance suitable for the material to be melted, and in general, forced pressure sintering is It is fired using the binding method.

Problems to be Solved by the Invention However, in the conventional type shown in FIG. 3, the induction coil 15 replaces the outside of the furnace body, so even a slight crack in the refractory can cause molten metal to leak inside the furnace wall. There is a high risk of invading the coil and burning out the coil or damaging the insulating structure and causing a major accident. Therefore, such refractory materials are required to have the following characteristics, and it is difficult to satisfy both of these requirements.

■Have high filling properties.

■Have appropriate sinterability.

■It must be chemically and physically stable at the melting temperature.

■It must have the strength to withstand charging of melted material and tilting of the furnace body.

■High wear resistance against flow of molten iron, molten steel, etc.

In addition, the content of CaO in the conventional refractory materials mentioned above is extremely small, and this is based on the general concept in this type of technical field that quicklime is difficult to sinter. Corrosion resistance against molten metal in fermentation melting furnace,
It has no choice but to be inferior in durability. In a crucible manufactured by the above-described forced pressure firing method, the entire crucible expands due to erosion of the molten metal, and may collapse into lumps during the cooling process after tapping.

"Structure of the Invention" Means for Solving the Problems A lime-based refractory material mixed in a weight ratio of 10 parts of quicklime to 0.5 to 2.0 parts of fluorite is stamped in the shape of a crucible,
1150±50t: A method for manufacturing a lime-based crucible, characterized by heating and holding for 20 to 40 minutes at a temperature range of 1150±50t.

By blending 10 parts of active quicklime with 0.5 to 2.0 parts of fluorite, the melting property of fluorite at a relatively low temperature, such as around 940°C, can be utilized to create an indica product. The fired refractory material used in this process is obtained. Heating temperature is 1100±50℃
This gives a preferable firing effect, and the desired crucible can be obtained by heating for 20 minutes or more.

Example The present invention as described above will be further explained.

The present invention relates to a sintering technique in which a lime-based crucible can be easily fired by mixing appropriate amounts of quicklime and desulfurizing agent with fluorite. When used, it is possible to easily produce ultra-low sulfur steel with a sulfur content of 10 ppffl or less, which has the effect of significantly improving scouring technology.

That is, the present invention takes advantage of the property of fluorite to melt at a relatively low temperature of around 940°C, and mixes fluorite in a ratio of 0.5 to 2.0 parts by weight to 10 parts of quicklime. By heating and holding the lime-based refractory material at 1100±50° C. for 20 to 40 minutes, it can be fired into a crucible with excellent durability and corrosion resistance. As a specific embodiment, as shown in FIG. 1, first the crucible bottom 22 is stamped inside the outer circumferential cylinder 21 having a bottom surface, and then the inner cylinder 23 is set.
The crucible periphery 24 is stamped to form a crucible shape, and the crucible body 1 from which the inner and outer cylinders 21 and 23 have been removed is fired, and a magnesia stamp 2, an energizing coil 5, and a cooling coil 4 are used. A yoke 6 and a yoke 6 are respectively attached to the outside of the trap as shown in the figure, and a tapping port T is provided at the upper part of the trap, and a furnace cover 8 is attached to form an electric induction bath melting furnace. It is preferable to use two innings of magnesia.

In the crucible, the amount of fluorite added to 10 parts of quicklime must be within the range of 0.5 to 2.0 parts, and 0.
．． If the amount is less than about 5 parts, it is not possible to effectively obtain the preferable sintering property due to the Tatami method blending. Also, this fluorite is 2.0
If it exceeds 50%, the viscosity increases in high temperature ranges, making cracks and peeling more likely to occur, which is undesirable.

The firing temperature is 1050°C to 1150°C, and 1050°C
If the temperature is lower than 1150°C, calcination cannot be obtained properly, and if the temperature is higher than 1150°C, calcium fluoride, which is the main component of fluorite, will decompose by itself, making it impossible to obtain a strong bonding force with lime.

Although the firing time depends on the thickness of the crucible body 6, it is generally possible to properly fire the entire product by setting it to 20 minutes or more.

Heating for more than 50 minutes is not only disadvantageous in terms of thermal energy since the firing effect is constant, but also disadvantageous because the operating frequency is reduced.

The firing temperature and firing time play an important role in releasing H2 gas and CO gas contained in quicklime and completely firing the refractory material.

The general chemical composition of the refractory material using quicklime and fluorite according to the present invention is shown in Table 2 below.

Table 2 Specific manufacturing examples of products according to the present invention are explained below.

Manufacturing Example A cylinder 12.13 as shown in FIG. 1 was manufactured using 5U8316 steel plate with a thickness of 5 mm, and a lime-based refractory material was mixed at the bottom of the outer cylinder 21 in a ratio of 10 parts quicklime to 1 part wall surface. The bottom part 22 is formed by stamping to a thickness of 30 to 40M, and then the inner cylinder 23 is installed in the center of the outer cylinder 21, and the above lime-based refractory is stamped in the space between the outer cylinder 21 and the inner cylinder 23. It was molded into a crucible shape.

The crucible-like body of the hindlimb, together with the inner and outer cylinders, is 1100±
It was charged into a heating furnace heated to 30° C. and heated for 35 minutes, so that the fluorite was melted and combined with quicklime.

The cylinder taken out from the heating furnace is allowed to cool naturally, then the inner cylinder 23 is removed, and then the outer cylinder 21 is turned upside down and the outer cylinder 21 is removed to form the target lime-based crucible 6.
I got it.

The lime-based crucible obtained as described above is
This is a summary of the results of measuring the S temperature for the operation results of melting ultra-low sulfur steel using a material with an S content of 41 ppm using a 50-year-old electric induction melting furnace configured as shown in the figure. and as shown in Table 3 below.

Table 3 It is clear from the results in Table 3 that in all of the operation examples, it was possible to produce extremely low heat and melt, and it also withstood the erosion of molten metal, and the operation was repeated four times in a row. It has become clear that the desulfurization effect persists to the extent that ultra-low sulfur steel with a sulfur content of 10 ppm or less can be produced. In addition, if the desired desulfurization effect cannot be obtained (see the bottom row of Table 3), the desulfurization effect can be achieved again by grinding the inner surface layer of a lime-based crucible with sandpaper, etc. If a lime-based crucible is used, no steel slag will be produced, and therefore special analysis equipment for monitoring the resulfurization reaction and steel slag removal will not be required, making it an ideal refining technology for ultra-low sulfur steel. I was able to improve my fluency.

Note that lime-based refractory material stamps use fluorite as a binder, so supplements such as silicate powder and phosphates are not recommended.
Of course it is.

``Effects of the Invention'' As explained above, according to the present invention, a lime-based crucible suitable for refining ultra-low sulfur steel can be accurately manufactured, and its effects can be achieved industrially. This is a great invention.

[Brief explanation of drawings]

The drawings show the technical content of the present invention, and FIG. 1 is a cross-sectional explanatory diagram of the crucible forming operation according to the present invention, FIG. 2 is a cross-sectional diagram of an electric induction furnace using the same, and FIG. The figure is a sectional view showing the structure of a conventional electric induction furnace. Finally, in these drawings, 1 is a crucible body, 2 is a magnetic stamp, 4 is a cooling filter, 5 is a current-carrying coil, and 6 is a
is the yoke, T is the tapping port, 8 is the furnace lid, 21 is the outer cylinder, 22
23 indicates the crucible bottom, 23 indicates the inner cylinder, and 24 indicates the crucible peripheral side. Patent applicant: Nippon Kokan Co., Ltd. Inventor: Tadashi Hirasaka Human Toshi Nakazawa Hirama Sato
Hiroshi Deguchi 2nd Department
Maeki Asai
Tetsu Terai Thoughts
Yoshimura Yoshihiramuki
Kiyoshi Sato
Seido Horiuchi
Masaharu Takano
Sadao Suzuki
Kazu Toshitoshi Tomatsuri
Kodo Enomoto
Ikiji Goto Agent Patent Attorney Shirakawa --- Hearth

Claims (1)

[Claims] A lime-based refractory material mixed in a weight ratio of 10 parts of quicklime to 0.5 to 2.0 parts of fluorite is stamped in the shape of a crucible,
A method for producing a lime-based crucible, which comprises heating and holding in a temperature range of 1150±50°C for 20 to 40 minutes.