JPH10230343A - Baggy core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the take-out of a bag after completing casting, to restrain melting and gasifying caused by contact of the bag with molten aluminum alloy and to obtain good effect to casting quality, cost, workability, etc., by using to the outer surface side of a core and forming a double layer structure filing block and granular material therein. SOLUTION: The bag 1 is used to the outer surface side of the core and the block and granular materials 2 are filled therein. After completing the casting, the bag 1 part is broken and then, since the granular materials 2 have no bonding power, these materials can be trickled out. Since the remained bag 1 is formed as skin-state, this bag can simply be pulled out. In the case of using a resin to the bag 1, the generating quantity of gas can be restrained by adding heat resistant fiber and powder in the bag. The temp. raising of the bag can be restrained with the absorption of the heat at the aluminum alloy side by including the block and granular material having higher thermal conductivity than the resin. Since the core used to the bag including the block and granular material having the high thermal conductivity and set at the time of casting, is used at the room temp., this core can sufficiently absorb the heat of molten metal. The cooling capacity at the core side is sufficient by this heat absorption, and the shrinkage hole caused by the shrinkage at the time of solidifying the molten aluminum alloy, is not developed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core used in the production of aluminum alloys, cast irons and copper alloys, which is used to produce undercuts, hollow internal parts having a complicated internal shape and high dimensional accuracy. It is about.

[0002]

2. Description of the Related Art Heretofore, a core integrally molded as described below has been used as it is, or as required, by coating a core integrally molded. In die casting, low pressure casting, and sand casting, a shell core made of hardened sand with heat-resistant resin is used. A phenol resin, a furan resin, a urea furan resin, or the like has been used as a heat-resistant resin used to solidify sand. It is still used as a mainstream core for production. In die casting, the surface of the shell core is coated and applied to the core in order to apply a high pressure. In some cases, the surface coating is performed by using an aggregate such as mica powder or graphite by applying an organic epoxy resin or phenol resin as a binder. In die-casting, an aggregate such as mica powder or graphite was used as a binder for the surface coating of a metal salt of an inorganic material such as sodium silicate and phosphoric acid. In die casting, there is a method in which a product integrally molded with a resin is used as a core (JP-A-6-91345, JP-A-6-99247, and JP-A-8-33968). There are also cases where a core molded from a low melting point metal is used. Integrally molded cores have the feature of being easy to manufacture, but in the case of cast products, gas and tar from combustion from the core reduce the quality,
The dimensional accuracy was poor due to deformation due to melting and casting pressure, and the casting was performed with poor disintegration when removing the core.

[0003]

[Problems to be solved] In mold casting, low pressure casting, and sand casting, when the molten metal comes into contact with the shell core, the heat-resistant resin that solidifies the sand undergoes thermal decomposition and gasifies, and the gas is filled. A burrow is made inside the casting by mixing in the molten metal on the way. Further, when the gasified component comes into contact with the low temperature part of the mold, it condenses, and the dust accumulates and the hot water flow deteriorates. When the core is taken out after the casting is completed, the part where the resin is not burnt has sufficient strength, and mechanical heat that makes a loud noise to collapse it and heat treatment only for the purpose of collapsing the core I was scorched and took it out. Die casting: Same problem as surface coating with shell core + resin binder. In the die casting, the solidification rate was too slow as compared to the mold side, so that shrinkage of the aluminum alloy occurred on the side in contact with the core due to shrinkage of the aluminum alloy. When pressurized during casting, the core could break. If the production is repeated, the mold accumulates on the mold, and the resin sticks to the mold in the high temperature part of the mold, so that the work of cleaning the mold periodically is required. Since the strength of the core itself is increased by the application of high pressure, it is difficult to remove the core after the completion of casting, so that it is not possible to obtain appropriate disintegration properties, and a large number of man-hours are required. Die casting: Surface coating with shell core + inorganic binder The same phenomenon has occurred, though to a lesser extent. If the surface temperature of the mold is high, the surface coat may adhere to the aluminum alloy and become unremovable. The same phenomenon as above was occurring. Die casting: Molded resin core Softens and deforms when the mold temperature rises, resulting in no product dimensions. In the portion where the solidification is slow, the cast product is cracked due to the thermal expansion of the resin. When it comes into contact with the molten metal, it becomes a gas by thermal decomposition, mixes into the cast product, or adheres to its surface to give a dark brown color. In the high temperature part of the mold, the resin core does not stick to the mold and deposits rapidly. The solidification speed on the resin core side is slow, and shrinkage occurs on the contact surface and inside due to shrinkage.
When the resin core is taken out after the casting is completed, the resin core cannot be taken out at normal temperature. Therefore, the resin core is taken out in a softened state by applying a temperature. Since the molded resin softens and expands, it cannot be taken out to the inside of the hollow. The remaining resin core is dissolved in a solvent that can dissolve the resin over a period of two to three days.

[0004] The above problems can be summarized as follows:
C can be consolidated. A] The disintegration after the completion of casting is poor and it is difficult to take out the core. B] When a resin material is used, it is thermally decomposed and gasified by contact with a high-temperature molten metal. In the high temperature part of the mold, the resin material melts and sticks. C] Since the resin material has a low thermal conductivity, the solidification speed becomes slow, and shrinkage occurs due to shrinkage of the molten metal. These problems are caused by using a core and resin that are integrally molded, and there is a relationship that cannot be solved.
A], which is the most problematic, requires rigidity to withstand the pressure applied by die casting and requires a high strength core, but the higher the core strength, the lower the disintegration. Therefore, it takes a lot of time to take out the core from the cast product. B] is generated as long as the resin material is in contact with the molten aluminum alloy to lower the casting quality. Further, sticking resin is deposited on the high temperature part of the mold, so that continuous casting is impossible. C] is a problem that cannot be solved because it depends on the physical properties of the resin material due to the low thermal conductivity of the material. In the actual situation, it is a fact that they are engaged in production of castings and casting tests while having these problems.

[0005]

[Means for Solving the Problems] The present inventors have found a means for solving a problem that cannot be solved by integral molding by using a two-layer structure. Put the core on the outer surface side as shown in Fig. 1 (1)
It is intended to solve the problem by using a bag and (2) forming a two-layer structure in which lumps and particles are packed. A] (1) If the bag portion is broken after the casting is completed, the particles in the bag portion have no binding force, and can be flushed out. The remaining bag is skin-like and can be easily pulled out. B] (1) When a resin is used for the bag, the temperature of the molten metal is high and the heat resistance is insufficient, so that gasification due to thermal decomposition is inevitable. B-1] Casting conditions: Paying attention to the fact that the gasification time varies depending on the resin material, if the molten metal is forcibly filled in a shorter time than the gasification, the cavity due to the gas inside the casting is obtained. The hole is gone. The results are shown in (Example 1). That is, it was found that the influence of the gas was not required if the molten aluminum alloy was filled earlier than when the resin material was thermally decomposed due to the casting conditions. B-2] Heat resistance of resin: A resin having high heat resistance, a non-combustible resin, and a resin added with a filler have a longer time to cause thermal decomposition. The results are shown in (Example 2). (1) When resin is used for the bag, the amount of gas generated can be suppressed by adding heat-resistant fiber or powder into the resin. B-3] (2) Lumps and particles: (2) Lumps and particles having higher thermal conductivity than resin, due to heat absorption on the aluminum alloy side (1)
The temperature rise of the bag can be suppressed. C] (2) The heat conductivity of the lumps and particles is high, and the core set when casting is at room temperature, so that higher heat absorption can be achieved. Due to this heat absorption, the cooling performance on the core side is increased, and the shrinkage due to shrinkage of the aluminum alloy is eliminated. The results are shown in (Example 3). In particular, in the case of metal particles, no shrinkage occurred. Manufacturing method of the bag core In mass production, it is possible to mold the bag portion like a plastic bottle or a resin bottle with a resin molding machine, and to fill the hollow portion with (2) lumps or particles. In the case of a small amount, a preheated resin plate can be set in a wooden mold and vacuum-suctioned. In the embodiment, a 1 mm resin plate preheated as shown in FIG. 2 is molded by pressing it between (3) wooden irregularities, and (4) half bags are joined together as shown in (FIG. 3). (5) A bag (1) formed by bonding with an epoxy resin as an adhesive was packed with (2) lumps and particles. Casting pressure Under high-strength, high-speed casting conditions such as die casting, (1) the bag deforms according to the contents of the bag core (2) and the shape of the lumps and particles as shown in FIG. 4. This is because (2) deformation of the bag was recognized as the mass and particles became finer, and the surface became almost flat when the maximum size was 500 μm or less.
(2) There was an effect even when the thickness of the bag was 2 mm or more. Mold casting, sand casting, low pressure casting with relatively long filling time (1) Aluminum hydroxide, magnesium hydroxide,
Add metal powder of aluminum, copper and iron zinc, (2)
It can be used by packing metal particles in lumps or particles. As the heat absorbing power of the bag core is improved, the amount of gas and the number of defects are reduced. The results are shown in (Example 4). The conventional shell core has no gas and shrinkage casting defects, and the disintegration requires only about 1/5 to 1/8 removal time. Recycling When a thermoplastic resin is used among heat-resistant resins, it can be recycled due to its reversibility. The result (Example 5)
Shown in Method of measuring gas amount The gas amount in the examples was determined by melting a cast product at 700 ° C., evacuating it to a vacuum, measuring the amount of gas generated, and calculating the aluminum alloy weight 1
It is converted and output per 00g.

[0006]

(FIG. 4) (8) In addition to the portion where the bag core comes into contact with the cast product, (6) a convex portion called a baseboard is made, and the concave shape is engraved in the mold. At the time of casting, the mold is closed by fitting the (6) baseboard portion of the (8) bag core into the concave portion of the mold, and the cavity is filled with (7) an aluminum alloy for use. (FIG. 4) shows the mold open state after casting. The cast product that has been opened and removed has a bag core.
To remove it, (6) if the skirting board is scratched, the (2) lumps and particles inside will have no adhesive strength, and will flow out smoothly. Then, (1) the bag can be easily pulled out like a thick plastic bag and made into a cast material.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a bag core according to the present invention will be described below. Except where otherwise noted, the examples are based on the following conditions. Core manufacturing method: Description of the core manufacturing method Board thickness 1 mm Casting product: Outlet water (Example 1) Casting method: Die-cast 320 ton Bag core: (1) Bag material and polyacetal Insufficient gas generation and heat resistance It is a material not used for casting. : No. 5 particles-No. 5 silica sand Casting conditions: After equilibrating to a mold temperature of 260 ° C, continuous casting was performed while changing the injection speed, and converted to the filling time. Cast product results: shown in FIG. For comparison, the amount of gas in the heat-resistant steel core that is pulled out with a normal mass-production mold without using a core is 11.2 cc / 100Al on average in mass production. It is thought to be due to the gas generated from the agent. Fukurocore condition: (2) Particle No. 5 silica sand flowed from the part that was broken by heat. (1) After the bag material was cooled to room temperature, it was easily peeled in a skin shape. Judgment of the result: This product is considered to be a non-defective product if it is 12 cc / 100 g Al or less, so if it is filled in 3.5 seconds or less at the maximum, there is no influence of gas. (Example 2) Casting method: Die-cast 320 ton Bag core: (1) Bag material: Also described with the following gas amount. : (2) Particle No.5 silica sand Casting condition: Equilibrium at mold temperature and 260 ° C: Filling time and 0.046 seconds same as mass production Bag core state: Of the sample number N = 5, with polyethylene and acrylic resin, the inner sand flowed out by N = 2 each time the mold opened after casting, but there was no problem with the dimensions and shape of the core. Others were the same as (Example 1). Judgment of the result: Since the resin has higher heat resistance than polyacetal, the amount of generated gas is also reduced. The level of 8 cc / 100 g Al was a good product that could produce only about 5% even in mass-produced products. (Example 3) Casting method: Die-casting 320 ton Closing defect position: Inside diameter side of the joint between the thin pipe portion and the flange. Bag core: (1) Bag material Polycarbonate + 10% aluminum hydroxide containing (2) Lump and particle material Metal aluminum sphere 1.8mm Casting condition: Mold temperature 260 ° C Filling time Same as mass production 0.046 seconds State of the bag core: (1) The bag core 0.5 mm was too thin, and the surface was slightly deformed and the weir was deformed by the casting pressure. Others were in good condition without any abnormalities. Judgment of results: (1) If the thickness of the bag core is 1 mm or more, it can withstand the casting pressure. With the two-layer structure of the bag core taking into account the cooling performance, the same cooling product as that of the mold body can be obtained. (Example 4) Casting method: Mold (gravity) casting A mold for mold casting was separately prepared and tested. Fukuronaka: Shown in the results PP is an abbreviation for polypropylene. Casting conditions: mold temperature, 380 ° C: filling time, average 8.3 seconds State of bag core: In PP and PP + 10% G, the bag core melted and the shape collapsed, or it melted partially before the weir. Others were not found in the area where the aluminum alloy contacts the bag core. Judgment of the results: (1) heat-resistant fiber or powder is added to the bag side, and (2) ceramic or metal particles are added to the lumps and particles to make it better than the current mass-produced products using shell cores. Become. (Example 5) Casting method: Die-cast 320 ton Bag core: (1) Bag material PE (polyethylene) + 10% hydroxide hydroxide containing (2) Lumps and particles Alumina spherical 1.8 mm Recycling method: Take out in leather (1) ) 20% by weight of a new material was added to 80% by weight of a bag and molded, and this operation was repeated. State of the bag core: The deterioration of the material due to repetition caused the color to change slightly from brown to dark brown, but there was no visual difference between 3 and 4 times. Judgment of the result: Although long-term repetition is unknown, the amount of gas and the reject rate increase slightly at the beginning of the repetition. However, the deterioration in casting quality due to calm and recycling can be minimized.

[0008]

According to the present invention, the removal of the core after the completion of the casting is very easy. (1) Melting due to contact between bag and aluminum alloy
Gasification was also suppressed, and the effect of gas from the current release agent of die casting was suppressed.
By combining (1) the bag and (2) the cooling property of lumps and particles, the same cooling property as that of the mold body was obtained, and measures against shrinkage failure became possible. (1) By using a thermoplastic resin for the bag, recycling is possible and industrial waste is eliminated. By these, it is a thing which brings good results to casting quality, cost, workability, environment and the like.

[Brief description of the drawings]

FIG. 1 is a sectional view of a bag core.

FIG. 2 is a sectional view of a mold and a half bag.

FIG. 3 is a sectional view of the joining of the bag core.

FIG. 4 is a sectional view of the mold after casting.

FIG. 5 is a graph showing the relationship between gas amount and time.

[Explanation of symbols]

 (1) Bag (2) Lump or particle (3) Mold (4) Half bag (5) Adhesive (6) Skirting board (7) Aluminum alloy (8) Bag core (9) Mold split surface

Claims (4)

[Claims] 1. A core having a two-layer structure in which (1) a bag is provided on the outside and (2) lumps and particles are packed therein. (2) The core according to (1), wherein a heat-resistant resin is used as a material of the bag. (1) As a filler in a bag, carbon fiber
Glass wool, inorganic fiber, ceramic, metal powder, sand,
The core according to claim 1, wherein refractory particles and powder, a flame retardant and a flame retardant are added. 4. The method according to claim 1, wherein the inner (2) particles are ceramic, metal,
The core according to claim 1, wherein a lump or particles of sand / refractory is packed.