JPH0642879A - Induction furnace for melting metal - Google Patents

Abstract

PURPOSE:To obtain means for improving a lining material and a constructing method in which an environment of a lining material construction of an induction furnace is improved and instability of an operation of the furnace due to an irregularity in a life due to an irregularity in the construction and the life can be improved. CONSTITUTION:A regular shape refractory material 3 molded by wet vibration charging in the atmosphere, a reduced pressure or a vacuum is installed at a predetermined position in an induction furnace 1 as a lining refractory material in the furnace, dry powderlike backside 4 is inserted to be charged between a furnace wall 2 and the material 3 to construct the furnace. Thus, an operating environment of the lining material construction of the furnace is improved, and its life can be largely improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction furnace for melting metals.

[0002]

2. Description of the Related Art In recent years, melting of metals (castings) in the casting industry has been the mainstream until now due to problems such as productivity, labor saving, quality of molten metal and working environment.

A. Little dissolution loss. B. The work operation is simple and labor saving is possible. C. There are few pollution problems. D. High uniformity can be secured by the effect of induction stirring. E. Easy control of ingredients and temperature.

Replacement with an induction furnace, which has various advantages, is rapidly becoming widespread. Since the induction furnace installed in place of the conventional cupola has to have a melting capacity comparable to that of the cupola, it tends to increase in size. The refractory material for the lining that forms the furnace wall of these induction furnaces is generally constructed with an irregular shaped refractory material. The refractory material and the quality of construction of the refractory material affect the life and availability of the furnace. If the durability of this refractory lining material is low, not only will the operating rate of the furnace be reduced, but the furnace itself will also be damaged and the entire foundry will be shut down. Requires a refractory material that has high heat resistance, thermal shock resistance, corrosion resistance, and hot wear resistance, does not crack, and has little melting loss.

At present, in some small and medium-sized induction furnaces, graphite, alumina, zirconia, magnesia, etc. refractory materials are used for melting non-ferrous metals such as aluminum and copper and ferrous metals such as stainless steel. Although crucible-shaped ones made of wood are used, all of them are 500 kg or less and have not yet been applied to large furnaces due to manufacturing and quality problems. Quality, high alumina quality, alumina quality, magnesia quality or magnesia quality
Spinel and zirconia are used, and in special cases, carbide may be added to them. Since these various raw materials satisfy the above-mentioned various characteristics, all of them are high-purity materials, which are not necessary as refractory materials, but indefinite shaped refractory materials manufactured by using a sintering aid such as boric anhydride in order to retain strength. Is mainly used, and it is constructed by vibration filling with dry powder or stamping method. When performing construction by such a compaction or vibration filling method, if particle size segregation of irregularly shaped material occurs during construction, or if construction is not performed reliably, not only will overall wear be accelerated, but local melting or cracking will also occur. This may cause a metal insertion phenomenon at this crack and cause a hot metal leak accident as well as damage the furnace itself, which shortens the life of the furnace and is economical in terms of operating rate and safety. Since the lining work is greatly affected, the lining operator needs an expert who is familiar with the work content and construction method and can perform reliable construction.
At the time of this construction, a steel mold (homer) is installed in the furnace, a refractory material is put between the furnace wall and the steel frame, and a vibrator is attached inside the mold to fill the material while vibrating it. Or stamp with a rammer. At this time, a large amount of dust is scattered when the refractory materials are sequentially charged, and segregation of particles easily occurs at the time of charging and at the time of charging, and the segregation of the particles becomes a physical and chemical unstable element of the construction body. . In particular, when segregation of particles occurs, a portion of coarse particles gathers between the particles (texture), and when the fine particles are offset, foreign matter easily penetrates. As a result, an altered layer is generated, causing a volume change and cracking. There are problems such as the inability to operate due to the phenomenon of a jug from the cracks or a local peeling phenomenon. Under such circumstances, stable life and stable operation of the furnace are no longer desired.

Further, the steel homer used at the time of construction is used once as a heating material and a shape-retaining tool for maintaining the strength of the molding and construction wall, and is a consumable item each time, so that the construction cost is high. However, there are still many problems such as not being able to make full use of the advantages of the induction furnace performance, and there is a strong demand for improvement of the quality of the furnace wall material and construction method. .

[0007]

[Problems to be Solved by the Invention] Dismantling of the furnace lining material at the present site, improvement of the environment by reducing 3K work during construction, and instability of furnace operation due to variations in service life due to variations in construction The technical issue is to provide a lining material that can be eradicated and the service life can be improved, and a method for improving the construction method.

[0008]

In view of the above situation, the present inventor has paid attention to filling the lining material of the furnace with a uniform and high density in advance, and as a result of various researches, the result has been sufficient in advance. Generated by the current method of construction on site as described above by using a binder and mixing and kneading well to prevent segregation of the refractory material, and by making it a homogeneous and high density molded body with high packing density It was possible to solve various problems such as working environment and quality, stable furnace operation and stable service life were obtained, and the service life could be extended.

That is, in the induction furnace of the present invention, the refractory layer forming the inner working layer of the furnace is adjusted to a composition and particle size composition suitable for the refractory material to be used by using a mold conforming to a predetermined shape. Add a suitable binder and mix and knead well to perform uniform wet vibration filling (atmosphere or reduced pressure, under vacuum) molding, and when the shape retaining ability appears, demold and dry to cure. A non-firing material to be produced or a heat treatment (firing) may be applied if necessary. In this way, wet vibration filling is performed to produce the product.

(Reason for limiting the forming method to the wet vibration filling method) The uniformity of the structure is enhanced. The bulk density (filling degree) is increased by vibration filling molding. Since the bond between particles is improved, no crack is generated even if it is dense. Excessive fine particle material can be removed and close packing becomes possible. In the case of siliceous materials, which are most often used in castings, since dry powder materials use boric acid anhydride to provide the required strength, the heat resistance and corrosion resistance of the joints, which are the most important for the refractory structure, are reduced. In the method, wet vibration filling is unnecessary and does not affect the characteristics of the refractory material, so that heat resistance, corrosion resistance, and crack generation due to sintering resistance are also improved.

The standard crucible-shaped material manufactured in this manner is installed at a fixed position in the induction furnace, and a dry powder-like backsand is inserted and filled in the gap between the furnace wall and the main material to complete the furnace construction. . The back sand material used at this time may be a commonly used refractory material having a controlled particle size, or may be zircon sand in which particles are as single particles as possible, or sized silica sand. In particular, the latter can solve the current problems because it is more effective in terms of work environment, workability, etc., such that the material has good fluidity and can be uniformly filled, and the generation of dust is extremely small. (EN) A refractory material for an induction furnace lining and a lining method therefor capable of achieving stable and long life.

Examples will be shown below.

[0013]

【Example】

◎ Construction furnace and operating conditions used in the examples 1.3T type low frequency induction furnace 2. Molten metal Normal casting (FC material) 3. Dissolution cycle: 60 minutes / ch, 11ch operation per day 4. Melting temperature 1500 ° C ◎ Refractory material for lining Raw material Silica-based refractory material SiO ₂ content 98% to 99% Material Maximum grain size 4 mm Grain size 1 mm or more 1 mm to 0.1 mm 0.1 to 0.044 mm 0.044 mm or less It implements using the above raw materials.

[0014]

[Table 1]

As shown in the results of Table 1, in the construction work in which much dust is generated, which is a typical 3K work, the time from dismantling to the end of construction is 29.7, together with improvement of the working environment.
%, Which was about 30.8%, which was about 30%, and the service life was significantly improved, with the melt loss cost remaining at 57.1% or 66.9%.

[0016]

EFFECTS OF THE INVENTION As shown in the above embodiment, the time required from the dismantling of the furnace lining material of the induction furnace to the construction, which is a typical work of 3K work as compared with the comparative example, is 195.
This is 58 minutes in the example of the present invention compared with 125 minutes in the comparative example, and when the comparative example is 100, it can be shortened to 29.7% in this example, and the handling amount of the powder material is And the working environment has been improved. In the method of the present invention, as shown in this example, the filling density (bulk specific gravity) is also compared with that of the comparative example because the furnace lining material is pressure-formed or vibration-filled using a semi-dry type or a wet type material in advance. 2.10 of the comparative example and 2.21 of the comparative example, the example material according to the present invention has a high value of 2.30, and the service life is 24 days for the comparative example and 28 days for the comparative example. According to the example according to the present invention, 17 in 42 days
It is possible to master a long service life of 5% to 150%,
The effect is tremendous.

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[Procedure amendment]

[Submission date] February 16, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Added

[Correction content]

[Brief description of drawings]

FIG. 1 is a sub-sectional view of an induction furnace for melting a metal according to the present invention.

[Explanation of symbols] 1. Induction furnace 2. Furnace wall 3. Standard refractory 4. Back side

Claims (1)

[Claims] An induction furnace for metal melting, characterized in that the refractory for lining the furnace in the metal melting furnace is constructed by a fixed refractory molded by wet vibration filling in air or under reduced pressure and under vacuum.