JPS63503289A - Ceramic filter for molten metal filtration - 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] Ceramic filter applicable to molten metal I This invention is for allowing molten liquid metal to flow through it. A system for molten metal applications consisting of a bonded or sintered ceramic body containing a large number of channels. Regarding ramic filters.

Molten metal typically contains solids, which can cause undesirable effects in the final casting. have a purpose. These mixed solids become inclusions in the final product after the molten metal solidifies. This can lead to defects in the final product. Inclusions can be caused by various causes, such as due to surface oxide films and insoluble impurities such as carbides and borides. may occur. Ceramic filters, e.g. U.S. Pat. No. 3,893,91 7.4081371 and 3962081 are particularly suitable for molten metals. interconnected to ensure a tortuous passage through which the genus is suitable. In addition, it has an open cell structure that includes many cavities surrounded by a network structure made of ceramic. Particularly suitable are these ceramic foam filters with a These fi Luthers are popular for a variety of reasons, including their superior performance, low cost, and ease of use. They are particularly advantageous due to their flexibility and the fact that they can be used interchangeably and disposablely. It is.

Ceramic foam filters are particularly practical and inexpensive to manufacture; Due to the fact that it can be used in single-use or single-use formats, molten metal processing has become popular in recent years. Its use has spread to the field of science.

However, special problems arise when dealing with molten metals such as steel with low fluidity. Ta. When using this type of material, it is necessary to start the flow of metal through the filter. is often difficult.

For this reason, before the filter is wetted, i.e. the flow of metal through the filter High metal deposits (Meta 11 u be rstand) is formed. Furthermore, the molten metal penetrates the entire filter. Often there is no flow through the filter, or the filter is It was acknowledged that there were no. Furthermore, in other instances the filter is not necessarily entirely Without wetting, excessively high metal deposits form on the filter.

These issues are particularly important in the case of steel, but also apply to other metals, each with their own unique characteristics. Occurs regardless of gold and casting temperature.

The way to solve these problems is to heat the alloy to obtain better flowability. there were. Superheating the melt improves its fluidity, which on the one hand promotes wetting. It was approved to proceed. However, this is not a completely satisfactory solution.

This is because large amounts of overheated material also create other problems regardless of the type of alloy. sand In other words, heating more than ordinary materials does not necessarily solve the above problems effectively. stomach.

Coated ceramic foam filter from U.S. Pat. No. 4,302,502 - are also known, which are respectively used to remove certain impurities from molten metal. It has an activation layer of a scale corresponding to the size of the market. However, the teaching regarding this filter is also This is not related to the metal deposit issue mentioned above.

The problem of the present invention is to eliminate the disadvantage of metal deposits and to solve the problem of metals with correspondingly low fluidity. Improved melting of molten metal to facilitate melting without the formation of excessive metal deposits. The purpose of the present invention is to provide a ceramic filter with high quality. Another object of the invention is to It is cheap and quick, and has no adverse effects on the filtration operation or the properties of the final casting. We provide an improved filter of the above type based on an acoustically silent bonded ceramic body. Is Rukoto. Another object of the invention is to provide a filter with significant wettability. It is an object of the present invention to provide an improved filter that does not require excessive heating.

According to the invention, this is achieved by a thin coating extending over the entire area of the filter. , consisting of an inorganic material easily wetted by molten metal, with a thickness of 5 to 1 micron adheres to the ceramic body and is removed when molten metal comes into contact with it. Made by a ceramic filter featuring

Therefore, the present invention aims to overcome the problem of low flowability of metals such as steel and provide convenient wetting. heats the metal significantly without forming excessive metal deposits. A high performance ceramic filter that does not require molten metal is disclosed.

The ceramic filter of the present invention has a thin coating through which molten liquid metal flows. a bonded or fired ceramic filter containing a large number of channels with The membrane adheres to the ceramic body and is wetted over essentially the entire area by the molten liquid metal. This is an expansion of inorganic materials. The coating is removed by the flowing molten liquid metal. It will be done.

This ceramic filter is particularly characterized by its open-celled cell structure and A ceramic containing a large number of interconnected cavities surrounded by a network of It is a foam filter. Ceramic bodies are made of aluminum oxide as a ceramic material. Contains minium. The preferred thickness of the coating is between 10 and 100. The coating is that It has a uniform film thickness and contains silicon dioxide, especially for steel filtration.

As mentioned above, metals with low fluidity, such as steel, are advantageously used in the art. The problem was that it did not flow through the ceramic filter. This problem is caused by molten metal This happens due to the ceramic filter material not being completely wetted. i.e. Molten metal does not flow or be distributed on the surface of the material.

For example, in the case of a ceramic filter that contains aluminum oxide as a material, This material is not completely wetted by the rope.

The ideal condition, i.e. high defiltration capacity, is that the parent metal material to be filtered is When the inclusions to be removed completely wet the furnace material, rather than actually wetting the furnace material. achieved. For example, aluminum oxide inclusions in steel contain aluminum oxide. W completely wets the ceramic filter, but steel leaves the filter incomplete. Don't let it get wet. The inclusions therefore pass through the metal stream and attach themselves to the filter. but the parent metal does not tend to remain in contact with the filter or inclusions. direction. Similarly, the matrix metal does not wet the filter and therefore attacks the furnace material. It is advantageous that the impact is smaller. This behavior occurs when flow begins to flow into the filter. Immediately, i.e. when the filter is already cast, the desired situation is achieved. give. Therefore, a filter that has these characteristics and is easy to cast at the same time. is worth pursuing. Also the advantageous properties of the filter or the We are also pursuing a filter that can easily cast molten metal without sacrificing performance. worth it.

Ceramic bodies of the present invention can be bonded or is a sintered ceramic body. Bonded and bent by a network structure made of ceramic All known Ceramic bodies, e.g. extruded ceramic bodies, objects consisting of sintered ceramic particles or by using ceramic foam filters, especially those with an open cell structure. I can do it. A particularly suitable ceramic foam filter is German Patent Publication No. 34 This is shown in the specification of No. 24504.

According to the invention, a thin coating is applied onto this ceramic body. In this case, this film is essentially spreads over the entire ceramic body and the film adheres to the ceramic body. this The coating is completely wetted by the molten metal and is 5 to 1 micron thick. It is a fee. In a convenient embodiment, the coating thickness is between 10 and 100 mm.

This indicates that the film is extremely thin. When loading the filter The coating is removed by contact with molten metal, and once the metal flow has started, it becomes overactive. The entire filter surface required for this purpose is now available. In particular, melting by molten metal by the mechanical action of the molten metal on the ceramic steel-like structure. In either case, it is preferred that the coating be completely removed within 5 seconds. subordinate Coatings that are soluble or partially soluble in molten metal are preferred.

10 to properly and quickly remove the coating once metal flow begins. It is preferable to use a film with a thickness of 0 Å or less; Coatings up to 1 micron can be used accordingly if

As mentioned above, the coating should not spread with a uniform thickness over the entire ceramic body. However, variations in film thickness and uncovered areas are acceptable. But easy to get wet In order to achieve this, the coating should spread throughout the network structure and be particularly uniform. Delicious.

The coating material is non-toxic to the molten metal being filtered or to the final casting. It must be a material that does not have any harmful effects. Therefore, the coating is removed from the network structure. Mechanical desorption is less worth pursuing than dissolution or partial dissolution into the metal. low.

Possibility of mechanically detached coating parts appearing as inclusions in the final casting This is because there is. Furthermore, the coating material may have adverse effects on the molten metal, such as mechanical properties. Do not cause a decrease in properties, coarsening of crystal grains, or the formation of an undesired second phase. No.

A preferred form uses a colloidal silicon dioxide coating. It is especially This is particularly advantageous for steel, as it allows a suitable silicon dioxide coating to be applied to the ceramic. This is because it has been recognized that it can be obtained on Mick bodies. Thin coating on ceramic body In view of the fact that the above amount of silicon dioxide coating is used, Does not have any adverse effects. Although not covered by the present invention, silicon dioxide There is only a possibility that the element may have an adverse effect. Also, thin dioxide according to the present invention The silicon coating is completely removed upon contact with molten steel.

In a preferred form, an aqueous dispersion of colloidal silicon dioxide, particularly 0 ．． A 5-10% concentration of colloidal silicon dioxide is used, especially a 1% concentration.

Additives may be added to the aqueous dispersion, such as wetting agents, dispersing aids, or coating aids. l! It is obvious that substances etc. can be used.

Depending on the preferred form, the dispersion described above is prepared and distributed over essentially the entire ceramic body. In order to obtain a thin coating, the ceramic body is immersed in the dispersion. Remove excess material (for example, shake it off), then remove the wet ceramic body from 93 to 14 for example. After drying at 9℃, especially 121℃, 982 to 1038℃3, especially 1000℃ The temperature treatment is such that silicon dioxide is not rehydrated (and the ceramic It must be hot enough to adhere firmly to the body. dry and re- Firing can be carried out in separate steps or continuously. This temperature must be maintained. There's no need. The material coated in this way has been found to be particularly suitable for filtration of steel. Admitted.

Coatings that require firing temperatures so high that damage to each ceramic body may occur It is obvious not to use .

Materials other than silicon dioxide can also be easily wetted by molten metal and It can be used as long as it is an inorganic material that is removed when it comes into contact with the genus. silicon dioxide is steel Steel filters are very well wetted by molten metal and easily dissolved by molten metal Very particularly preferred. Other suitable inorganic materials that can be used include, for example, silicates, For example, aqueous dispersions of sodium silicate, and salts such as sodium chloride or Contains potassium chloride. In this case, the latter salts are reticulated instead of being calcined again. Dry once on the structure. Oxides, such as calcium or magnesium acids compounds can also be used, which are used as salts, e.g. carbonates, and then dried Can be dried and calcined. Metals such as nickel, iron and chromium are Used in coatings as a solution or dispersion of metal compounds and then converted to metals For this purpose, a drying process and a heat treatment can be performed. These metals are used for coating This is not a hindrance since the amount of water used is extremely small.

The unique advantage of the coating composition according to the invention is that it is easily wetted by molten metal and Use of inorganic material in the form of a thin film that can be easily removed under the action of molten metal. It is in. Since the coating is easily wetted by metals, suitable ceramic materials should be used. In some cases, the metal can be applied to a ceramic body, and even tortuous flow channels within the ceramic body. casting time and metal deposits can be significantly reduced.

For example, it has the effect of causing the process to progress more quickly, and for example, The flow of flowing material is generally faster than with uncoated ceramic bodies. It's bright. Surprisingly, the filter according to the invention is not coated after casting. Retains a higher flow rate than the filter. This occurs after the coating comes into contact with molten metal. This is despite the fact that it was removed.

This means that the entire ceramic filter is cast more quickly, and According to the faster flow through all the pores of the ceramic filter body Seem. This is also a development worth considering.

The invention will be further illustrated by examples.

One way J1-1 It is 18.7 mm thick, has an open cell structure, and is made of ceramic mesh. It features a number of interconnected cavities surrounded by a structure in which the filter book Bonded ceramic filter body with body based on aluminum oxide ceramic Prepare.

The filter used exhibits 10 pores/CI+. Pros of this filter completely into an aqueous dispersion containing 1% colloidal silicon dioxide according to the present invention. The filter body is coated by dipping for a short period of time during which complete impregnation takes place; It was dried at 21°C and fired at 1000°C to obtain a thin film. Film thickness after firing 10 people, and the coating is essentially silicon dioxide particles distributed throughout the ceramic body. was agglomerated. Various types of coated and uncoated filters The tube was fitted into the hollow casting tube. These casting tubes are made of aluminum The specimen was gradually immersed in a deoxidized steel bath and maintained at 1621°C. The start of casting This was determined by visually observing the center of the tube. As a result, the coated filter Immediately after immersion in the bath, it was wetted to a depth of 5.08 cm. uncoated fill The tar was not wetted to an immersion depth of 5.08 CII. Approximately 10 more tubes ．． When immersed to a depth of 16 cra, the tube broke due to thermal shock. coated For filters that were not wetted, no wetting was observed.

Memories J1 Special Coating corresponding essentially to the composition according to Example 1 and prepared essentially according to Example 1 A coated filter and an uncoated filter were prepared.

1. Sequentially casting coated filters and uncoated filters with a thickness of 1.86CI+1 I put it in a crucible. Molten steel is directly transferred to a casting crucible from an induction furnace at a temperature of 1621°C. was injected into. As the crucible is filled, the static pressure on the filter The load rose until it reached the overflow height. When the filter gets wet , determined by visually observing the outlet side of the filter. the result, Coated filters wet 4-5 seconds faster than uncoated filters It was recognized that The flow of molten metal through the coated filter is extremely It was confirmed that the liquid was liquid. In comparison, an uncoated filter The flow flowing through was very viscous and slow. As soon as the bath is finished, A total of 76.6 kg passed through the coated filter. In contrast, uncoated flaps Only 11.3 kg passed through the filter. Furthermore, the obtained casting The products were of high quality. The film on the filter has an unfavorable effect on the filter. It didn't affect me. Additionally, silicon dioxide coatings are inherently resistant to molten metal contact. removed by dissolving it in molten metal.

Husband's support - Lord Coated and uncoated filters with compositions essentially according to Example 1 were carried out. Prepared according to Example 1. However, the filter body contains 6 and 10 pores. Featured. Four sand molds were prepared, three of which were equipped with filtration devices. 4 pieces All of the sand molds were filled with aluminum deoxidized medium carbon 8204 directly from the induction furnace. kg was cast. The results are shown in Table 1 below.

, Table-1”- As clearly shown from the above results, casting l can be improved by using coated filters. The cast surface was entirely free of inclusions. Without using a filter, quite a bit in the material Compare with Casting 2, where there was an amount of inclusions present. uncoated filter Casting 3 using However, when the filter got wet, it completely failed.

Casting 4 used a coated filter, even though the casting temperature was 26°C lower. Part of it got wet.

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Claims (6)

[Claims] 1. A thin coating extends over the entire area of the filter and is blown away by molten metal. Made of an easily wettable inorganic material, it can be applied to a ceramic body with a thickness of 5 Å to 1 micron. molten metal, characterized by its adhesion and being removed when molten metal comes into contact with it consisting of a bonded or sintered ceramic body containing a number of channels for the liquid metal to flow through. A ceramic filter for filtration of molten metal furnaces. 2. Ceramic foam filter whose ceramic body has an open cell structure and interconnected structures surrounded by a network of these ceramics. Ceramic film according to claim 1, characterized in that it consists of a large number of cavities. Tar. 3. Claims 1 and 2, characterized in that the coating has a thickness of 10 to 100 Å; The ceramic filter according to item 2. 4. The method according to any one of claims 1 to 3, characterized in that the film thickness of the film is uniform. Ceramic filter listed in any of the above. 5. Claims 1 to 4, characterized in that the coating is a silicon dioxide coating. Ceramic filter according to any of paragraphs. 6. Claim 1, characterized in that the ceramic body contains aluminum oxide. The ceramic filter according to any one of Items 1 to 5.