JP5062637B2 - Intermediate Stoke Manufacturing Method - Google Patents

Description

  The present invention relates to an intermediate stalk of a low-pressure casting apparatus used for manufacturing an aluminum casting or the like.

  A basic configuration of a conventional low pressure casting apparatus is shown in FIG. In FIG. 2, 1 is a molten metal container (crucible) constituting a low pressure casting apparatus, 2 is a molten aluminum, 3 is a furnace lid, 4 is a stalk tube, 5 is an intermediate stalk, 6 is an external heater, and 7 is a mold. The molten aluminum 2 in the molten metal container 1 is heated by a heating means (not shown) and is in a molten state.

  For casting with the low-pressure casting apparatus, the pressure of pressurized air indicated by an arrow P is applied to the molten metal surface of the molten metal 2 by means not shown, and the molten metal 2 passes through the molten water passages of the stalk pipe 4 and the intermediate stalk 5 by this pressure action. Then push up toward the mold 7. Although not shown, an air vent hole is provided in the upper part of the mold so that excess air can escape therefrom.

  A mold corresponding to the product to be cast is disposed in the mold 7, and the pushed-up molten metal flows into the mold. And a casting (aluminum casting) is obtained by cooling a metal mold | die at an appropriate timing. Here, the structure of a low-pressure casting machine that pushes up the molten metal and supplies it to the mold is shown. However, the pressure inside the mold is reduced, and the structure that sucks up the molten metal by the pressure-reducing action or the pressure inside the mold is reduced. There is also a low-pressure casting device with a structure that pushes the molten metal under pressure.

  In the low pressure casting apparatus, the stalk pipe 4 and the intermediate stalk 5 must be able to withstand the temperature of the molten metal. In general, the Stoke tube 4 is made of cast iron or fine ceramics. On the other hand, the intermediate stalk 5 is often made of cast iron for ease of molding.

  The stalk tube 4 stably supplies molten metal, and therefore has an inner diameter of about several centimeters to several tens of centimeters. On the other hand, the gate of the mold 7 is larger than the inner diameter of the Stoke tube, or the gate is divided into a plurality. Therefore, in order to smoothly advance the flow of the molten metal from the stalk tube 4 to the gate of the mold 7, an intermediate stalk 5 that functions as an intermediate hot water pool is required. If there is no intermediate stalk 5, there is a possibility that the molten metal enters the gate of the mold unevenly or the gate is clogged. Therefore, the uniformity of the material of the obtained cast product may be impaired, and so-called “su” may be formed.

  Generally, the temperature of the molten aluminum in the molten metal container 1 of the low pressure casting apparatus is about 600 ° C to 700 ° C. As a matter of course, the temperature of the molten metal until the molten metal is introduced into the mold needs to be maintained at a predetermined temperature.

  However, in the case of a large product, the mold becomes large, and the intermediate stalk on the mold gate side must also be increased. If it does so, the movement distance of a molten metal and the surface area of a shell material (casing) will become large in intermediate | middle stalk, the heat dissipation from intermediate | middle stalk will increase, and the problem that the temperature of a molten metal will fall occurs.

  Further, at the time of casting, the molten metal that has not been able to enter the mold returns to the intermediate stalk 5 and the stalk pipe 4, but if the temperature of the intermediate stalk is lowered, the molten metal is solidified and adhered and deposited there. Also occurs.

  In general, it is inevitable that a molten metal material or oxide adheres to the inner surface of the intermediate stalk, and it is dealt with by periodic removal and maintenance. The above temperature drop problem also occurs in the Stoke tube 4, but becomes significant in intermediate Stoke. As a means for solving such a problem, there is a method in which the stalk tube and the intermediate stalk are heated from the outside by an electric heater or a gas burner so that the molten metal is not cooled.

When aluminum is used as the molten metal, the molten metal temperature is 600 ° C to 700 ° C. In order to make the product obtained as a result of casting uniform, the temperature of the molten aluminum is not lowered in the intermediate stalk, and the molten metal temperature is controlled within a certain range, so that a stable molten metal flow is achieved. It is necessary to consider so that it can be obtained.
However, in the above-described external heating system, fluctuations in the hot water temperature at the rise and fall of the heater or burner are unavoidable, and the product uniformity and product yield are naturally limited. It will be.

  Moreover, when it is made not to reduce hot water temperature using an external heating system, it is necessary to heat intermediate | middle stalk to 800 to 900 degreeC. However, when the intermediate stalk of cast iron is heated, the above-described heating temperature causes a problem that the durability of the intermediate stalk skin material (casing) itself is deteriorated (deterioration of the material). Further, contamination occurs due to the material of the casing material (casing) being melted into the molten metal. In addition, the cast iron, which is the outer skin material (casing), is distorted by heating, and a malfunction occurs in the seal mechanism.

To prevent deformation and contamination of the intermediate stalk, the intermediate stalk outer shell (casing) may be made of high heat-resistant ceramics, but the intermediate stalk is more than the stalk tube on the molten metal container side. Another problem arises that the shape becomes complicated and inevitably expensive. In addition, when the shape of the high heat-resistant ceramic is complicated, it is necessary to design in consideration of problems such as repeated thermal history (hysteresis), stress cracking due to local heating, and load resistance of the mold.
In addition, when a ceramic outer casing (casing) is used, it becomes difficult to transfer heat compared to that made of metal such as cast iron, so it is difficult to transfer heat due to external heating, and the range of changes in molten metal temperature is large. This is expected to affect the uniformity and yield of products.

  On the other hand, Patent Document 1 and Patent Document 2 are disclosed as means for suppressing the temperature drop of the molten metal in the intermediate stalk without using an external heating system. Specifically, Patent Document 1 discloses an intermediate stalk A including a heat insulating layer 7 and an immersion heater 10, and Patent Document 2 discloses an intermediate stalk 7 having a sleeve 11 and a heat insulating material 12. The thing provided with the heat insulation layer of the layer is disclosed (a code | symbol is what is described in drawing of each patent document).

JP 2000-271722 A Japanese Utility Model Publication No. 04-047856

  Similar to the above-mentioned patent document, the present invention is common in that it is implemented in intermediate stalk without using an external heating system to suppress the temperature drop of the molten metal in the intermediate stalk. However, by developing intermediate stalk with improved performance, quality, etc., it is possible to maintain a more constant molten metal temperature for each casting, and to improve the product uniformity and product yield. It aims at providing the low-pressure casting apparatus used.

In order to achieve the above object, a first invention is an intermediate stalk used in a low-pressure casting apparatus, and the inside of a metal outer shell material has non-wetting property, erosion resistance, and heat insulation properties against molten metal. In addition, it is structured such that an inorganic material that adjusts and absorbs the mutual thermal expansion difference is sandwiched between the outer skin material and the refractory heat insulating material. Here, “intermediate stalk” is sometimes expressed as “Yuguchi nesting”, “distributor” or the like, and “outer material” is sometimes expressed as “casing” or the like. In the present invention, the “inorganic material” is formed by, for example, applying a flexible material containing inorganic fibers, an inorganic binder, and appropriate moisture to the outer skin material as a putty material to form an “inorganic material layer”. However, in consideration of workability, for example, an inorganic paper pre-formed into a sheet shape or a paper shape is preferable.
The second invention is characterized in that the refractory heat insulating material has a porosity of 20 to 80% and a density of 0.5 to 2.0 kg / m ³ .
According to a third aspect of the invention, the refractory heat insulating material is an amorphous refractory heat insulating material obtained by kneading a calcium silicate and / or siliceous main material with an alumina cement binder and water added thereto. It is a feature.
According to a fourth aspect of the present invention, there is provided a refractory heat insulating material mainly composed of inorganic fibers and alumina powder, and mica, carbon, silicon carbide or silicon nitride powder as a non-wetting improver, and silica or alumina inorganic binder. It is a paste-like amorphous refractory heat insulating material obtained by adding a thickener and water and kneading.
The fifth invention is characterized in that the inorganic material is a heat-expandable sheet that expands by heating.
In the present invention, the heat-expandable sheet refers to a sheet that starts expanding at 300 to 400 ° C. and expands in the thickness direction, for example. The expansion coefficient only needs to be twice or more in the thickness direction, and in the present invention, the expansion coefficient may be 2 to 4 times. If the expansion coefficient is 2 times or less, it is feared that the gap between the outer skin material and the refractory heat insulating material that may be caused by a difference in thermal expansion cannot be sufficiently closed, and the expected heat insulating effect cannot be obtained, and is 4 times or more. Then, there is a concern that the expansion is too large and the refractory heat insulating material lining material is broken.
The heat-expandable sheet may be a sheet material containing, for example, ceramic fibers 20 to 40% by mass, unfired vermiculite 40 to 70% by mass, and organic binder 5 to 20% by mass, and the density is 500 to 800 kg. / Cm ³ , preferably 600 to 700 kg / cm ³ .
In the present invention, the inorganic paper is a sheet material containing 90 to 98% by mass of inorganic fibers such as ceramic fiber, alumina fiber, rock wool, and glass fiber and 2 to 10% by mass of an organic binder in addition to the above-described heat-expandable sheet. It may be. The density of such a sheet material is 100 to 300 kg / cm ³ .
The sixth invention is a low pressure casting apparatus provided with these intermediate stalks.
A seventh invention is a method for producing intermediate stalk used in a low-pressure casting apparatus, the step of attaching an inorganic material that adjusts and absorbs a difference in thermal expansion to the inside of a metallic outer skin material, and a water repellent property to the inorganic material A step of performing a treatment, and a step of lining a refractory heat insulating material having non-wetting property, erosion resistance, and heat insulating property with respect to the molten metal on the inorganic material subjected to water repellent treatment.

According to the present invention, the following effects can be obtained.
(1) Heat dissipation from the intermediate stalk is suppressed, and the temperature drop of the molten metal is prevented. Therefore, it becomes unnecessary to use an external heater.
(2) Since an external heater is not used, the heat balance for each casting is equal, and casting can always be performed under the same conditions. That is, the product quality can be made uniform.
(3) The intermediate stalk has non-wetting properties, erosion resistance and airtightness, and adhesion of molten metal to the stalk inner surface and penetration into the stalk are prevented.
(4) By sandwiching an inorganic material that adjusts and absorbs the mutual thermal expansion difference between the outer skin material and the refractory heat insulating material, cracking of the refractory heat insulating material due to the thermal expansion difference can be prevented. Moreover, by using a heat-expandable sheet that expands by heating as the inorganic material, it is possible to close a gap that may be generated between the outer skin material and the refractory heat insulating material due to a difference in thermal expansion, and to prevent deterioration of the heat insulating effect.
(5) Even intermediate stalks with complicated shapes can be easily obtained.
(6) Since an external heater is not used, the service life of intermediate stalk can be extended as compared with conventional intermediate stalk.

The cross-sectional schematic diagram of the low-pressure casting apparatus which shows one Example of this invention. The cross-sectional schematic diagram of the conventional low pressure casting apparatus.

  As a preferred embodiment of the present invention, as shown in FIG. 1, in the low pressure casting apparatus that performs casting by feeding the molten aluminum 2 in the molten metal container 1 into the mold 7 through the stalk pipe 4 and the intermediate stalk A, The inner side of the intermediate stalk A is lined with a refractory heat insulating material B having non-wetting properties, erosion resistance and heat insulation properties through a heat-expandable sheet C for the purpose of adjusting and absorbing the difference in thermal expansion between each other. .

  The embodiment shown in FIG. 1 will be described. In addition, the same code | symbol is attached | subjected to the same or similar member as FIG. In FIG. 1, 1 is a molten metal container, 2 is a molten aluminum, 3 is a furnace lid, 4 is a silicon nitride ceramic stalk tube, A is an intermediate stalk, and 7 is a mold.

  The intermediate stalk A is made of a conventional cast iron outer shell material (casing), and is adjusted to absorb and absorb the difference in thermal expansion between each other through a sheet C made of heat expansion to make it non-wettable and resistant to damage to molten metal. And a refractory heat insulating material B having both heat insulation properties.

As the refractory heat insulating material B having the above-mentioned physical properties, an amorphous refractory heat insulating material (mainly composed of calcium silicate or siliceous material, kneaded by adding an alumina cement binder and water) Made by our company: trade name "Lumisar" etc.), paste-like unshaped refractory heat insulation material (mainly aluminosilicate ceramic fiber and alumina powder, kneaded with silica or alumina inorganic binder and water) It is preferable to use the product name “Lumicast” manufactured by our company. Mica, carbon, silicon carbide, silicon nitride powder and the like are added to the paste-like amorphous fireproof heat insulating material for the purpose of improving non-wetting.
According to the use of these irregular refractory heat insulating materials, the intermediate stalk portion A having a complicated shape can be easily formed by the mold forming means, and then the product can be commercialized by heating and drying.

  In that case, the intermediate stalk skin material (casing) 8 is an outer frame type, the inner frame type is assembled therein, and the fireproof heat insulating material or the paste-like fireproof heat insulating material is filled between both frame types. Intermediate stalk A can be obtained. Alternatively, a fire-resistant and heat-insulating structure having a predetermined shape may be prepared in advance by using an amorphous fire-resistant heat insulating material, and the structure may be fitted into a skin material (casing).

Under the present circumstances, the layer for adjusting and absorbing a mutual thermal expansion difference can be provided by affixing the inorganic material C (inorganic paper or an inorganic sheet) inside the outer shell material (casing) 8. By providing this layer of inorganic material C, it is possible to prevent cracking of the refractory heat insulating material B due to a difference in thermal expansion. That is, there is a difference in the coefficient of thermal expansion between the refractory heat insulating material B and the outer skin material (casing) 8, and when the refractory heat insulating material B and the outer skin material (casing) 8 are directly bonded together, the refractory heat insulating material B is inferior in strength. A load is applied and cracking is likely to occur. By interposing the inorganic material C, the inorganic material C plays a role as a buffer material, and the fire-resistant heat insulating material B can be prevented from cracking.
Further, by using a heat-expandable sheet that expands by heating as an inorganic material, it is possible to close a gap that may be generated between the outer skin material and the refractory heat insulating material due to a difference in thermal expansion, and to prevent deterioration of the heat insulating effect.
Furthermore, the inorganic material may be subjected to a water repellent treatment in advance, or after applying an inorganic material that adjusts and absorbs the difference in thermal expansion to the inside of the metallic outer skin material, the inorganic material is subjected to a water repellent treatment. Also good. For such water repellent treatment, a known technique may be used. For example, an inorganic material may be coated or impregnated with a water repellent material such as silicone, paraffin, or spray oil. Such a water-repellent treatment eliminates problems such as poor flowability of the lining material caused by water absorption by the sheet and inadvertent generation of voids (voids) when lining an amorphous fireproof insulation material containing moisture. Is done.

  In addition, a heat insulating board 9 having non-wetting properties, heat resistance and heat insulating properties may be provided between the intermediate stalk portion A lined with the fireproof heat insulating material and the gate of the mold 7.

  As the heat insulating board 9, for example, it is preferable to use a heat insulating material made of a composition mainly composed of aluminosilicate ceramic fiber or zonotlite-based calcium silicate. The heat insulating board 9 made of the above raw material has a heat insulating function for preventing the heat of the molten metal in the intermediate stalk from escaping to the mold, and is hard to get wet with the molten metal. It can be easily removed without any problems. Although not shown, appropriate packing is disposed between the stalk tube 4 and the intermediate stalk A, and between the heat insulating board and the casting mold.

Next, examples of the present invention will be described.
Heat expandable sheet material (Nichias T / # 6760 Vermoflex thickness 2.0mm, density 650kg / m ³ (room temperature), 150kg) / M ³ (after heating at 850 ° C. for 30 minutes)) was applied, and paraffin was applied as a water repellent to the surface of the heat-expandable sheet material to perform water repellent treatment. After the water repellent is dried, the inner mold is fitted, and the amorphous fireproof insulation composed of the composition shown in Table 1 is vibrated between the inner mold and the outer skin material to which the heat-expandable sheet material is attached. Poured. After curing, the mold was removed and baked at 350 ° C. to obtain an intermediate stalk.
In this example, Examples 1 to 5 and Reference Examples 1 to 2 shown in Table 1 or Table 2 were prepared for the refractory heat insulating material B. Here, Examples 1 to 3 are irregular refractory heat insulating materials mainly composed of silica powder or the like, and correspond to the refractory heat insulating materials according to claim 3. Examples 4 to 5 are irregular refractory heat insulating materials mainly composed of inorganic fibers and alumina powder, and correspond to the refractory heat insulating materials according to claim 4. Reference Example 1 is an amorphous refractory mainly composed of silicon carbide powder. In Reference Example 2, a molded body was prepared in advance using reaction-sintered silicon nitride ceramics RBS (manufactured by Shinagawa Fine Ceramics Co., Ltd.) and fitted into an outer skin material (casing).

As a comparative example, the amorphous refractory heat insulating material used in Example 1 was applied without attaching a heat-expandable sheet material that adjusts and absorbs the difference in thermal expansion to the inside of the metal skin material. Examples 1 to 5 and Reference Examples 1 and 2 had no problem even if they were actually used, but the comparative example had a few shots after operation, and the lining material was cracked and could not withstand practical use. Was confirmed.

The physical properties using Examples and Comparative Examples as described above are as shown in Table 2 below.
Examples 1 to 5 have physical properties in the range of porosity 20 to 80% and density 0.5 to 2.0 kg / m 3, and the amount of heat dissipated (the same applies below under the predetermined conditions described in Table 2) is 10. It is lower than 000 kcal / m ² h. In contrast, Comparative Examples 1 and 2 have physical properties of a porosity of less than 20% and a density of 2.0 kg / m ³ or more, and the amount of heat dissipated is 2-3 times higher than 10,000 kcal / m ² h. . Here, the amount of heat dissipated was calculated according to JIS A 9501 “Insulation Standard for Thermal Insulation / Construction”.
Therefore, it was found that the physical properties of the refractory heat insulating material used as the intermediate stalk lining material are preferably in the range of porosity 20 to 80% and density 0.5 to 2.0 kg / m ³ . .

  INDUSTRIAL APPLICABILITY The present invention can be widely used as an intermediate stalk of a low pressure casting apparatus, and has high practicality capable of spreading a heaterless system of a low pressure casting apparatus that does not require a heater (whether external or internal). is there.

1 Molten metal container (crucible)
2 Molten aluminum 3 Furnace lid 4 Stoke tube 5 Intermediate stalk 6 External heater 7 Mold 8 Outer material (casing)
9 Insulation board A Intermediate stalk (internal lining product)
B Fireproof insulation (lining material)
C Heat-expandable sheet

Claims (5)

A method for producing intermediate stalk used in a low pressure casting apparatus,
A process of attaching an inorganic material that adjusts and absorbs the difference in thermal expansion to the inside of the metal skin material;
An intermediate stalk skin material is used as an outer frame mold, and an inner frame mold is assembled therein, and a step of filling a fireproof heat insulating material or a paste-like fireproof heat insulating material between both frame molds is provided .
A method for producing intermediate stalk, wherein the inorganic material is a heat-expandable sheet that expands by heating, and has an expansion coefficient in the thickness direction of 2 to 4 times . A method for producing intermediate stalk used in a low pressure casting apparatus,
A process of attaching an inorganic material that adjusts and absorbs the difference in thermal expansion to the inside of the metal skin material;
A fireproof heat insulation structure of a predetermined shape is prepared in advance with an amorphous fireproof heat insulating material, and it is provided with a step of fitting it into the outer skin material ,
A method for producing intermediate stalk, wherein the inorganic material is a heat-expandable sheet that expands by heating, and has an expansion coefficient in the thickness direction of 2 to 4 times . The method for producing intermediate stalk according to claim 1 or 2, wherein the refractory heat insulating material has a porosity of 20 to 80% and a density of 0.5 to 2.0 kg / m ³ . The refractory heat insulating material is an amorphous refractory heat insulating material obtained by mixing and kneading an alumina cement-based binder and water with calcium silicate and / or siliceous as a main material. , 2 or 3 A method for producing an intermediate stalk. Refractory heat insulation material is mainly composed of inorganic fiber and alumina powder, and mica, carbon, silicon carbide or silicon nitride powder is added to this as non-wetting improver, and inorganic binder, thickener and water are added and kneaded. The method for producing an intermediate stalk according to claim 1, 2 or 3, which is an irregular refractory heat insulating material obtained in the above.

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