JPH0818884B2 - Filter material for molten metal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a filter material for molten metal for filtering solid impurities from the molten metal.

(Prior Art) A metal thin plate or foil is manufactured by casting a molten metal into an ingot and rolling it. However, when solid impurities such as metal oxides contained in the molten metal and minute fragments of refractory are directly mixed into the ingot, pinholes and surface defects occur in the process of rolling this to produce thin plates and foils. Sometimes. In order to prevent this, it is necessary to remove solid impurities from the molten metal, and therefore, glass cloth, alumina balls, ceramic foam or the like has been conventionally used as a filter for molten metal filtration.

However, glass cloth tends to be clogged at an early stage, and alumina balls are apt to flow out of impurities once trapped, resulting in poor filtration accuracy. Furthermore, since ceramic foam has a large pore size, fine impurities cannot be sufficiently filtered. is there.

Therefore, for example, as shown in JP-A-48-6912, for example, aggregate particles such as silicon carbide and alumina, B ₂ O ₃ ,
A filter medium having a structure in which innumerable fine continuous pores are formed between aggregate particles by bonding with an inorganic binder containing Al ₂ O _3, CaO, etc. is being used. According to this, clogging can be prevented for a long period of time, and there is no outflow of captured impurities,
Moreover, there is an advantage that the pore diameter can be appropriately adjusted and precise filtration can be performed.

(Problems to be Solved by the Invention) However, the above-described filter medium may sometimes be cracked during handling or use, and may be damaged by the pressure of the molten metal, which is still unsatisfactory in terms of strength. The reality is that there was room. If a filter material cracks during use, the molten metal containing solid impurities will pass through the crack intensively, resulting in extremely low filtration performance and replacement of the filter material when it is damaged. Also, a large loss occurs due to re-filtration of the molten metal. Further, the above-mentioned filter material has a problem that unstable CaO contained in the inorganic binder easily flows out into the molten metal, and the free CaO that flows out causes cracks in the rolling process of the ingot.

Therefore, an object of the present invention is to provide a filter for a molten metal capable of ensuring sufficient strength and preventing contamination of the molten metal with CaO or the like.

[Structure of the Invention] (Means for Solving Problems) The filter material for molten metal of the present invention is one or more kinds of aggregate particles of silicon carbide, silicon nitride, fused alumina and sintered alumina. Are bound by an inorganic binder, and the inorganic binder is B ₂ O ₃ 15-80%, Al ₂ O ₃ 2-60%
And CaO 5 to 50%, and 10 per 100 mol of B ₂ O _3.
It is characterized by having a composition containing ~ 20 mol of SiO ₂ .

(Operation) According to the metal melt filter medium of the above means, since the content of SiO ₂ in the inorganic binder is optimum for B ₂ O ₃ , stable borosilicate glass is produced and the bond strength is remarkably high. Will increase. Moreover, since the chemical stability of the matrix is enhanced by the formation of borosilicate glass, the outflow of free CaO is suppressed and the contamination of the molten metal is prevented. Where B ₂ O ₃
If the SiO ₂ content is less than 10 mol per 100 mol, the degree of vitrification is low, and sufficient strength improvement and CaO outflow suppression effect cannot be obtained. On the other hand, when SiO ₂ is 20 mol or more, the amount of borosilicate glass produced becomes excessive, and although strength improvement is observed, excess SiO ₂ is reduced by molten metal and flows out as free silicon (so-called silicon pickup). Invite. The free silicon that has leaked out in this way causes pinholes and cracks in the rolling process of the ingot, and may cause read signal disturbance when a memory disk is manufactured, especially in the case of aluminum. It is necessary to suppress it as much as possible. In addition, the outflow of constituents such as CaO and SiO ₂ in the matrix into the molten metal means the corrosion of the matrix and thus the decrease in its strength.Thus, it becomes difficult to maintain the strength for a long time with these products. According to the invention, since the outflow of the constituent components is strongly suppressed, not only the contamination of the molten metal can be prevented but also the strength can be maintained for a long period of time.

Further, as the aggregate, it is necessary that it is not corroded by the molten metal and that it can be easily obtained with an appropriate grain size, but silicon carbide, silicon nitride, fused alumina and sintered alumina satisfy these conditions.

On the other hand, among the constituent components of the inorganic binder, B ₂ O ₃ is a component having poor wettability with respect to molten metal, particularly molten aluminum, and excellent corrosion resistance, but B ₂ O ₃ itself has a low melting temperature,
There is a problem that the viscosity in the molten state is low and the vaporization occurs at a high temperature. Therefore, Al ₂ O that does not react with molten aluminum
₃ and CaO are added to form a glassy material to bond the aggregate particles. The components, B ₂ O ₃ is 15 to 80%, Al
It is necessary that ₂ O ₃ is 2 to 60% and CaO is 5 to 50%, and it is difficult to form a glassy material in other ranges. When Al ₂ O ₃ is less than 2% and MgO is less than 5%, an appropriate glass state cannot be obtained, and when Al ₂ O ₃ is 60% or more and CaO is 50% or more, the melting temperature increases and the firing temperature increases. Since it needs to be increased, the amount of B ₂ O ₃ scattered during firing will increase rapidly.

The amount of the above-mentioned inorganic binder added varies depending on the particle size of the aggregate, but generally 4 parts by weight per 100 parts by weight of the aggregate particle is used.
-20 parts by weight is suitable. This is because if it is less than 4 parts by weight, it is insufficient to fill the matrix part of the aggregate particles, and if it exceeds 20 parts by weight, the voids between the aggregate particles are filled with the inorganic binder and the filtration efficiency is lowered.

(Examples) Examples of the present invention will be described below.

14-28 mesh sintered alumina is used as aggregate particles, and the composition of the inorganic binder is B ₂ O ₃ 45%, Al ₂ O ₃ 30%, CaO 25
%, And SiO ₂ was added in various amounts in the range of 0 to 30 mol with respect to 100 mol of B ₂ O ₃ . The aggregate particles and the inorganic binder were kneaded together with an organic binder and water, shaped into a predetermined shape, dried, and fired at 1300 ° C. After firing, the room-temperature bending strength and the hot strength after immersion in the molten aluminum alloy 5056 for 24 hours were measured, and the strength ratio to the room-temperature strength (hot strength /
Room temperature strength) was determined. The results are shown in the figure.

As is clear from the figure, for 100 mol of B ₂ O ₃ , 10
When SiO ₂ is added in a molar amount or more, the room temperature strength is significantly increased. Further, the strength ratio is sufficiently large in the range where the amount of SiO ₂ added is 20 mol or less, and in the range exceeding 20 mol, the hot strength is largely reduced and the strength ratio is remarkably reduced. From these results, it is clear that a filter medium having remarkably excellent strength can be obtained only in a narrow range in which 10 to 20 mol of SiO ₂ is added to 100 mol of B ₂ O ₃ . In addition, although the measurement results are not particularly shown, in the inorganic binder as compared with the conventional metal melt filter medium,
Since the content of SiO ₂ was considerably low, free silicon flowed out by that much, and the contamination of the molten metal could be prevented as much as possible. Moreover, since the composition ratio of the inorganic binder is appropriate and stable borosilicate glass is produced, almost no CaO outflow into the molten metal was observed.

[Advantages of the Invention] As described above, the present invention produces stable borosilicate glass in the matrix, so that the binding force can be sufficiently increased and damage during handling or use can be prevented for a long period of time. You can Moreover, since the stability of the matrix is increased by the formation of borosilicate glass, CaO can be prevented from being released and flowing out.Since the content of SiO ₂ is extremely small, the reduction and outflow of silicon can also be suppressed, Therefore, it is possible to prevent the generation of cracks and pinholes during ingot rolling due to the contamination of the molten metal and to maintain the strength of the matrix for a long period of time.

[Brief description of drawings]

FIG. 1 is a strength characteristic diagram of the filter medium in the example of the present invention.

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Claims (2)

[Claims] 1. Aggregate particles of one kind or two or more kinds of silicon carbide, silicon nitride, fused alumina, and sintered alumina are bound by an inorganic binder, and the inorganic binder is B ₂ O ₃ 15 to 80%, Al ₂ O ₃ 2 to 60% and CaO 5 to 50%, and a composition containing 10 to 20 mol of SiO ₂ with respect to 100 mol of B ₂ O _3. A filter material for molten metal, characterized by 2. The filter material for molten metal according to claim 1, wherein the inorganic binder is 4 to 20 parts by weight with respect to 100 parts by weight of the aggregate particles.