JPS6293045A - Net-like filter for filtering molten high melting point metal - Google Patents

Abstract

PURPOSE:To obtain a filter which substantially withstands a molten high melting metal and has an excellent filtration effect for the molten metal by forming a net-like filter of glass fibers contg. specific components. CONSTITUTION:The net-like filter for filtering the molten high melting point metal is formed of the glass filters to a mesh shape. The glass fibers contain >=75wt% SiO22 and are preliminarily shrunk by calcination. The net body after the calcination treatment is adequate for handling of filter if an acidic or neutral consolidating agent is deposited on the fibers to provide a shape retaining property to said body. Since the filter is molded of the glass fibers in the above- mentioned manner, the filter has excellent heat resistance and withstands all kinds of molten cast irons.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a glass fiber mesh filter capable of filtering high melting point metal molten metal such as iron-based molten metal.

(Prior art and its problems) When slag suspended in a ferrous metal such as cast iron or cast steel flows into a casting cavity together with the molten metal, the slag floats to the surface of the casting and solidifies, forming a non-metallic inclusion in the casting. It aggregates directly under the black crust and causes casting defects.

For this reason, runners are generally provided with means to prevent slag from entering the casting cavity.

A common method for this is to increase the height of the runner in the runner system and increase the length of the runner to float and separate the slag in the runner route from the sprue to the casting cavity. However, this method is not preferable because it causes a decrease in yield due to the casting method and becomes a factor in high product cost.

Therefore, in order to shorten the runner route and remove slag, a ceramic strainer-1 foam type or honeycomb type ceramic filter is used in the sprue, runner, etc., but these are both expensive. However, the filtration effect is poor, and since it is brittle, it is easily damaged.Furthermore, it is necessary to provide a recess for the cent in the design during use, which increases the cost of the model required to mold this part. There is.

On the other hand, reticular type carbon fiber or glass fiber filters have been put into practical use, but these only function as filters for low melting point metals such as aluminum/8-molten metal, and are not suitable for low melting point metals such as iron-based melts. 175Fc
I'm addicted to the high-melting-point gold/8-hot water version (currently I can't provide it).

The present invention was made in view of these problems, and is a high-melting point metal/8-molten metal that is easy to handle, does not cause damage, is inexpensive, and has an excellent removal effect of suspended matter such as slag in high-temperature molten metal. The purpose is to provide filters.

(Means for Solving the Problems) The filter of the present invention, which was taken to achieve the above object, is characterized in that the filter is formed in a mesh shape with glass fibers, and the glass fibers have a content of 75% by weight or more. Contains Sin, and has undergone shrinkage due to firing.

(Example) Hereinafter, the reticular filter of the present invention will be explained along with its manufacturing method.

The glass fibers forming the reticular filter of the present invention must be able to withstand high-temperature molten metal, and from this point of view the 5iO7 content that contributes to heat resistance is defined.

In view of this, the present inventor conducted an experiment of immersing glass fiber in molten metal in order to determine the 810□ content in glass fiber.

That is, glass fibers having various SiO□ contents were prepared, immersed in high-temperature molten metal for 20 seconds, pulled up, and the state of deterioration of the fibers was observed.

Figure 1 shows the experimental results, showing the molten metal temperature and SiO□ content (
% by weight). In the figure, ◯ indicates that there was no significant change, and ◯ indicates that a portion of the sample melted and turned into slag.

From Figure 1, when the 5iCh content is 70%, the filter turns into slag and becomes unusable when immersed in the molten metal at 1350"C for 20 seconds, making it suitable for all types of molten cast iron (1200-1450°C). 75% to let
It turns out that you need to do more than that.

By the way, in order to increase the SiO□ content of glass fiber,
Generally, glass fibers may be subjected to acid treatment.

In other words, glass fibers mainly composed of silica are immersed in an acidic solution such as hydrochloric acid, nitric acid, or sulfuric acid with a catalyst added to promote the reaction, and impurities are removed while controlling the temperature, time, and concentration of the acidic solution. CaO, MgO, Fe
z 0B, Cr20B, Na20, K2O, TlO2
, B20. As a result, the content of SiO
It increases the content of □. In the light treatment, it is possible to experimentally increase the SiO□ content up to 99.9%, but industrially the upper limit is about 99.5%. That is, Ca that does not dissolve in the acidic treatment solution,
Mg, Fe, etc. remain in the fiber in the form of positive ions and combine with negative ions in the treatment solution to form CaSO4 on the fiber surface.
, Ca(Off) z , CaO, , CaCQa, hg
This is because it is difficult to separate because it is adsorbed in the form of Fe(OH)2, etc.

A net made of glass fibers having a 5ift content of 75% or more is subjected to a firing treatment and shrunk in advance for the following reason. Many pores are present in acid-treated silica fibers, and these pores cause the net to shrink when it is used as a filter for filtrating molten metal.

If this shrinkage is large, the filter set on the parting surface of the mold will scrape the molding sand near the filter holding part into the molten metal, causing casting defects such as sand pits.
The smaller the shrinkage that occurs when the filter is heated, the better.

The higher the firing temperature and the longer the firing time, the higher the heat shrinkage rate, which is advantageous because the shrinkage is smaller when the mesh is used as a filter, but the processing temperature and time are subject to restrictions in industrial production. The heat shrinkage rate is expressed as (l-β') / ffi , when using the mesh as a filter, ′
/g? Considering the allowable amount of shrinkage due to heat, the heat shrinkage rate that must be achieved by firing is 2.5.
% to 15%.

Therefore, usually 800'C x 30 minutes to 1100'C x
A firing process is performed for about 5 to 10 minutes. The above heating shrinkage rate can be sufficiently achieved under such firing conditions. In addition, 110
If the temperature exceeds 0°C, the silica fiber undergoes cristobalite transformation and becomes brittle, so the firing temperature must be 1100″C or lower.

After the firing process, the net body can be easily handled as a filter by applying an acidic or neutral solidifying agent to the fibers to give it shape retention properties. For example, if the net is coated with acidic novolak phenol resin, neutral phenol resin, starch paste, acidic silica sol solution, etc. and then dried at 150°C for about 20 minutes, the flexural rigidity of the net will be improved and shape retention will be imparted. be done. Using an acidic or neutral curing agent may cause alkaline content to enter the fibers, lowering the fiber strength, or causing SiO□
This is to prevent the content ratio from decreasing. However,
Of course, even without applying a curing agent, the mesh filter can be used, for example, by curing the outer periphery with resin sand or by retaining its shape with wire.

In addition, it is preferable that the opening size of the mesh is 0.4 to 4i. If it is less than 0.4-, the passage resistance of the molten metal will be large, resulting in poor running of the molten metal, and if it exceeds 4-, the effectiveness of removing slag etc. will be reduced. Moreover, the thickness of the net body is preferably 1 to 4 mm. If it is less than IN, the bending rigidity during passage of the molten metal will be insufficient, and if it exceeds 4, the effect of dividing the cast product at the filter intervening part cannot be expected.

Next, a specific example will be described in comparison with a conventional example.

[Casting example of stepped round bar]

(1) Using the various filters shown in Table 1, stepped round bars made of ductile cast iron were cast according to the casting method shown in FIGS. 2 and 3. In the figure, 1 is a stepped round rod cavity, 2 is a runner, 3 is a riser, 4 is a sprue, 5 is a filter, and 6 is a core for installing a filter. Further, the dimensional unit in the figure is ms.

The molten metal composition is as follows, and the casting temperature is 14oo'c.
, the casting time is 10 seconds.

・Molten metal composition (wt%, remainder substantial Fe) C: 3,3-3
．． 9% P: Q, 1% or less Si: 2.0-2.7%
S: 0.01% or less Gate n: o, 2-0.45%
Gate g: 0.025 to 0.050% The firing conditions for the filters of the present invention (numbers 1 to 3) are 900°C x 30 minutes with a heat shrinkage rate of 3%, and a hardness to provide shape retention. A binder was applied.

As the solidifying agent, an acidic novolak phenol resin with a pH of 1 to 2 was used for 11ml, and a neutral phenol resin with a pH of 7.2 was used for the solidifying agent.

Next Leaf 1 Table Note 1. The magnets marked with a circle indicate the KLLd array of the present invention.

Note 2. Seven primary 8-13 pieces/1 inch, blank 5-90%
Structure: Three-dimensional network skeleton structure in which pores are interconnected. Here, the number of cells refers to the number of pores (cells) lined up in a straight line of 1 inch. (2) After casting, remove 5 mm from the surface of the stepped round bar, perform a color check, check the number of surface defects (color check spots), and evaluate the performance of the filter using the following criteria. evaluated.

- Judgment Criteria 4a (Visual judgment of color check spot size φ0.3 or more) The results of averaging the scores of each step were as follows.

Dimension 1... 4 points, Dimension 2... 4 points, Block 3... 5 points 11
h4...2 points, lt5...3 points, 隘6...1 point (
3) From the above results, it can be seen that the filter of the present invention has extremely superior filtration effect compared to conventional filters.

In addition, the thickness was extremely thin compared to conventional ones, and it was extremely easy to insert into the mold.

[Casting example of stepped test piece]

(1) In the same manner as in the casting example of the stepped round bar, using the filter shown in Table 1, the molten ductile cast iron was used to
A step-shaped test piece as shown in FIG. 4 (dimension units in the figure are ■ and inches) was cast.

(2) After casting, the surface was cut and removed until there were no surface defects (color check spots), and the depth of the defect layer was investigated.

The results are shown in Table 3.

Table 3 (3) From Table 3, when the filter of the present invention is used, most defects can be eliminated by cutting 21 or less regardless of the thickness of the casting, whereas with the conventional filter, As the thickness increases, the defect layer tends to become deeper, and it is clear that the filtration effect of the filter is inferior to that of the present invention.

(Effect of the invention) As explained above, the reticular filter of the present invention has a 15 m
Since it is made of glass fiber containing N% or more of S'rOt, it has excellent heat resistance and can withstand all types of molten cast iron. l! ! High temperature of molten metal etc.? ! j. It is also applicable to molten metal. Furthermore, the filtration effect is even better than conventional ones. Furthermore, since the glass fibers have been previously shrunk by firing, they are less likely to be deformed during filtration of the molten metal.

As described above, the reticular filter of the present invention can sufficiently withstand high melting point metal molten metal, has a superior molten metal filtration effect compared to conventional filters, is inexpensive, and has significant utility value in the foundry industry. It's large.

[Brief Description of the Drawings] Figure 1 is a diagram showing the relationship between molten metal temperature and 5i02 content in glass fiber, Figures 2 and 3 are explanatory diagrams showing a casting method for a stepped round bar, Figure 2 is a plan view, Figure 3 is a second
FIG. 4 is a perspective view of the stepped test piece. Figure 1 Figure 3 Figure 4

Claims (1)

[Claims] (1) A reticular filter for filtration of high-melting point metal molten metal, which is a reticular filter formed of glass fibers, characterized in that the glass fibers contain 75% by weight or more of SiO_2 and are pre-shrinked by firing.