JP3237083B2 - Induction furnace for metal melting - Google Patents

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 metal.

[0002]

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

[0003] b. Low dissolution loss. B. Work operation is simple and labor saving is possible. C. There are few pollution problems. D. High uniformity can be ensured by the induction stirring effect. E. Control of components and temperature is easy.

[0004] The replacement with an induction furnace having advantages and the like is rapidly progressing and becoming popular. Induction furnaces installed in place of conventional cupolas tend to increase in size in order to have melting capabilities comparable to cupolas. The refractory for lining forming the furnace wall of these induction furnaces is generally constructed of an irregular refractory, and the quality of the refractory and the construction of the refractory determine the life and operation rate of the furnace. If the durability of this refractory lining material is low, not only will the furnace operating rate be reduced, but also the furnace itself will be damaged, and the entire casting plant will be shut down. Therefore, a refractory material that has high heat resistance, thermal shock resistance, corrosion resistance, and high abrasion resistance during heat, does not crack, and has little erosion is required.

At present, in some small and medium-sized induction furnaces, graphite, alumina, zirconia, magnesia or other refractory metals are used to dissolve non-ferrous metals such as aluminum or copper and iron metals such as stainless steel. Crucibles made of materials are used, but they are all furnaces of 500 kg or less and have not yet been applied to large furnaces due to manufacturing and quality issues. , High alumina, alumina, magnesia or magnesia
Spinel, zirconia, and the like are used, and in more special cases, carbide may be added thereto. These raw materials satisfy the above-mentioned characteristics, and are made of a high-purity material. The refractory is an irregular refractory manufactured using a sintering aid such as boric anhydride in order to maintain strength while being necessary and bad. It is mainly used, and it is built by vibration filling with dry powder or stamping method. When performing construction by such a compacting or vibration filling method, when irregularity in the size of the irregular-shaped material occurs during construction, or when construction is not performed reliably, not only accelerates overall wear but also causes local melting or cracking. Not only does this crack cause a metal ingot phenomenon, causing hot water leaks but also damaging the furnace itself, shortening the life of the furnace, and further reducing the operating efficiency and safety. The lining builder needs a skilled person who is familiar with the work contents and the construction method and can perform the construction reliably.
At the time of this construction, a steel mold (homer) was built in the furnace, refractory material was put between the furnace wall and the steel frame, and a vibrator was attached inside the mold to fill the material while applying vibration. Or stamp with a rammer. At this time, a large amount of dust is scattered when the refractory material is sequentially charged, and particles are easily segregated at the time of charging and filling, and the segregation of the particles becomes a physically and chemically unstable element of the construction body. . In particular, when segregation of particles occurs, a portion where coarse particles are gathered causes a water bath between particles (texture), and foreign matter easily penetrates where fine particles are biased, and foreign matter penetration at a high temperature is difficult. It forms a deteriorated layer, causes a volume change, and causes cracks. There remains a problem that the operation cannot be performed due to the phenomenon of hot water from the cracked portion and local peeling phenomenon. Under these circumstances, stable furnace life and stable operation are no longer desired.

Further, the steel homer used at the time of construction is used once as a heating material for maintaining the strength of the molding and the construction wall and as a tool for retaining the shape, and becomes a consumable at each time, so the construction cost is high. And still have many problems, such as not being able to fully exploit the advantages of furnace performance of induction furnaces.Currently, improvements in furnace wall material quality and construction methods are strongly desired. .

[0007]

Dismantling of furnace lining materials at the current site, improvement of the environment by reducing 3K work during construction, and instability of furnace operation due to variation in service life due to variation in construction. It is a technical object to provide a method of improving a lining material capable of eradicating and improving a service life and a method of improving a construction method.

[0008]

In view of this situation, the present inventor has focused on filling the furnace lining material in advance with uniformity and high density. Using a binder and mixing and kneading well, segregation of the refractory material does not occur, and a uniform and high-density compact with high packing density is generated by the current method of on-site construction as described above. Thus, various problems such as working environment and quality can be solved, stable furnace operation and service life can be obtained, and the service life can be extended.

That is, in the induction furnace of the present invention, the refractory layer forming the lining operation 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, mix and knead well, perform uniform wet vibration filling (atmosphere or reduced pressure, under vacuum), mold, and then remove and dry at the place where the shape retention ability appears, and cure by curing. The unfired material to be produced or, if necessary, heat treatment (firing) may be applied. It is produced by performing wet vibration filling in this way.

(Reason for Limiting the Forming Method to the Wet Vibration Filling Method) The uniformity of the structure is improved. The bulk density (filling degree) is increased by vibration filling molding. Due to the improved interparticle bonding, no cracks are generated even if the particles are dense. Excessive fine particle material can be removed and close packing can be achieved. In the case of siliceous materials, which are used most often in castings, the use of boric anhydride etc. to impart the required strength to dry powder materials reduces the heat resistance and corrosion resistance of the most important joints in the refractory structure. In the method, the wet vibration filling is not required and does not impair the characteristics of the refractory material, so that the heat resistance, corrosion resistance and crack generation due to sintering resistance are also improved.

The shaped crucible-shaped material thus manufactured is installed at a fixed position in an induction furnace, and a dry powder back sand is inserted and filled in a gap between the furnace wall and the material to complete the furnace. . The back sand material used at this time may be a generally used refractory material having a controlled particle size, zircon sand having a single particle as much 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 as good fluidity of the material and uniform filling, and extremely low generation of dust. An object of the present invention is to provide a refractory material for induction furnace lining and a lining method for the same that can stably extend the life.

An embodiment will be described below.

[0013]

【Example】

◎ Construction furnace and operating conditions used in Examples 1.3T type low frequency induction furnace 2. Molten metal ordinary casting (FC material) 3. Dissolution cycle 60 min / ch 11 ch / day operation Melting temperature 1500 ° C ◎ Refractory material for lining Raw material siliceous refractory material SiO ₂ content 98% ~ 99% material Particle size composition Maximum particle size 4mm Particle size composition 1mm or more 1mm-0.1mm 0.1-0.044mm 0.044mm or less This is carried out using the raw materials as described above.

[0014]

[Table 1]

[0015] As shown in the results of Table 1, in the case of the construction work in which a large amount of dust is generated, which is a typical example of the 3K work, the time from dismantling to completion of the construction is 29.7 along with the improvement of the work environment.
% Was 30.8%, which is about 30%, and the service life was greatly improved with the erosion cost remaining at 57.1% or 66.9%.

[0016]

As shown in the above embodiment, the time required from the disassembly of the lining material of the induction furnace to the construction, which is a typical operation of 3K operation for the comparative example, is 195 for the comparative example.
In comparison with the case where the comparative example requires 125 minutes, the embodiment of the present invention takes 58 minutes, and when the comparative example is set to 100, it can be reduced to 29.7% in the present example, and the handling amount of the powder material And the working environment has improved. As shown in the present example, the method of the present invention also includes a comparative example in which the filling density (bulk specific gravity) of the furnace lining material is previously formed by pressure molding or vibration filling using a semi-dry or wet material. In contrast to 2.10 of the comparative example and 2.21 of the comparative example, the example material according to the present invention has a higher service life of 2.30. The service life of the comparative example is 24 days, and that of the comparative example is 28 days. According to an embodiment according to the invention, 17 in 42 days
5% to 150% and a long service life can be learned.
The effect is enormous.

[Brief description of the drawings]

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

[Explanation of symbols]

 1. Induction furnace 2. Furnace wall 3. Fixed refractories 4. Backside

Claims (1)

(57) [Claims] 1. A refractory for lining a furnace in an induction furnace for melting a metal by adding a proper amount of a binder in advance and building the refractory into a shaped refractory in the atmosphere or under reduced pressure and vacuum by wet vibration filling. An induction furnace for melting metals.