JPS6393445A - Core for die casting - Google Patents

Abstract

PURPOSE:To crush a core after high-pressure casting and solidifying of molten Al and to improve workability by forming the core of a metal hydroxide the surface of which consists of strong metal carbonate at the time of mounting the core into a metallic mold for die casting of Al. CONSTITUTION:The movable metallic mold having a projecting part 2a mounted with the core 4 is clamped into the recess 1a of a stationary metallic mold 1 for die casting Al to form a casting cavity 3 between the recess 1a and the core 4. The core 4 formed by using the hydroxide such as Ca(OH)2, putting the molding to an autoclave of a gaseous CO2 atmosphere, subjecting the same to a heating treatment, and forming a hard CaCO3 layer of a high decomposition temp. on the surface of the core 4 is used in this case. The molten Al 6 in a casting sleeve 5 is press-fed by a plunger 7 through a runner 8 and a gate 9 into the casting cavity 3. Since the surface of the core is the hard CaCO3 layer, the shape collapse thereof does not arise. CaCO3 decomposes to CaO and CO2 and the inside Ca(OH)2 decomposes to CaO and H2O as well after the solidification of the molten Al upon lapse of time. The core collapse of itself simultaneously with mold opening. The die cast product is thus easily taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a core in die casting that is supported by a mold and inserted into a mold cavity, and which collapses after solidification of the molten metal.

[Conventional technology]

When die-casting aluminum worms and the like, if the shape of the cast product makes it impossible to remove it after the mold is opened, a core is provided in the mold cavity and the core is opened in the direction perpendicular to the mold opening, and then the mold is opened. It is made using a core called a core. This core is made of sand or powder, and after the mold is opened and the cast product is removed, the core is collapsed and removed.

This type of core has a weight of several hundred 1g/cm when filling the mold cavity with hot water, and in some cases 1000Kf.
Requires strength to withstand high pressure reaching /cIr&,
Furthermore, in the case of aluminum die casting, it is required to maintain a hard and clean surface without decomposing for several seconds even when exposed to a bath temperature of about 700°C. Furthermore, after the molten metal has solidified, it must be disintegrated, and it is desirable that the product can be easily dispensed and washed with water after completion of molding.

[Problem that the invention seeks to solve]

So far, cores having various compositions and manufacturing methods have been proposed, but none of them necessarily satisfy the above requirements in terms of rapid production.

[Means for solving problems]

In order to solve these problems, in the present invention, a die-casting core is formed from metal hydroxide powder, and the surface is hardened by reacting with carbon dioxide gas.

[Effect]

For example, if a core is formed using calcium hydroxide as a metal hydroxide and used for aluminum die casting, the surface of the core will be exposed to carbon dioxide gas when molten aluminum is filled into the mold cavity. Because it is covered with a hard layer of calcium carbonate caused by the reaction, the composition will not change due to aluminum B hot water at around 700℃, and the internal calcium hydroxide layer will also rise in temperature within 1 to 2 seconds after filling. Therefore, the core will not break even if the casting pressure reaches several hundred KF/cm.

After several tens of seconds pass after filling, the hydroxide inside the υ core collapses due to the heat of the molten metal, exceeding the decomposition temperature of 370°C. When the product between the core and the mold shrinks due to cooling, the core also receives a large shrinkage force and the hardened surface layer also collapses.
After opening the mold, the product can be taken out. When taking out the product, when water is poured, calcium hydroxide is easily dissolved and discharged, making it easier to take out the product.

〔Example〕

This practical example shows an example in which the die-casting core according to the present invention is applied to a mold for aluminum die-casting, and the figure is a longitudinal sectional view of the mold in which the present invention is implemented. In the figure, the fixed mold 1 and the 0T movable mold 2 shown in a clamped state are provided with a recess 1a and a projection 2a that engage with each other, and this retaining part has a U-shaped cross section. A cavity 3 is formed, and a core 4, which will be described later, is interposed in the cavity 3 and held by a convex portion 2a. Reference numeral 5 denotes a casting sleeve fitted into the sleeve hole 1b of the fixed mold 1, which is equipped with a pouring port 5 for injecting aluminum F6 molten metal 6, and the inner hole has an oil pressure of an injection cylinder (not shown). A plunger tip 7a of a plunger 7 that moves forward and backward is engaged so as to be able to move forward and backward. A runner 8 and a gate 9 are formed between the casting sleeve 5 and the cavity 3 as a passage for the bath water 6 which is pressed by the plunger tip 7a and injected into the bathtub 3.

The core 4 is made of a powder of metal hydroxide such as Cca(OH)++), which is heated in an autoclave containing carbon dioxide gas. As a result of the treatment, a hard layer of calcium carbonate (Ca) is formed on the surface.The thickness of this layer is set according to the shape of the core 4, and the treatment time in the autoclave is Calcium hydroxide (Ca(OH)s)
Its decomposition temperature is about 370°C, and when the temperature exceeds this temperature, it releases crystal water and decomposes into oxidizing power (Cab) and water vapor (H, O). Further, the decomposition temperature of calcium carbonate (CaCOB) is about 900°C.

The aluminum die-casting operation performed using the core configured as described above will be explained. The core 4 formed into a predetermined shape from the above material is poured into the convex part 2a of the movable mold 2, the mold is clamped, and the molten metal 6 is poured into the casting sleeve 5 from the pouring spout 5a, followed by a plunger tip. When the T& is moved forward, the molten metal 6 is injected and filled into the cavity 3 through the runner 8 and the gate 9.

When f6 6 is filled, the surface layer of core 4 is covered with a layer of hard carbonic acid (CaCO3), so 70
The composition does not change due to the molten aluminum 6 at around 0℃, and the temperature of the internal calcium hydroxide [Ca(OH)n] layer does not rise even if the filling time is 1 to 2 seconds, so the casting pressure can be reduced to several hundreds of degrees. It can be molded without breaking even under high pressure of Kf/(7F+. After filling the molten metal 6, several tens of seconds have elapsed,
When the core 4 enters a cooling field, the core 4 absorbs the temperature of the molten metal 6 and rises in temperature. At this time, the hydroxide power inside the core 4 is CCa (
OH)m) also increases in temperature and exceeds the decomposition temperature of 370°C, so
A portion of calcium hydroxide (Ca(OH)i) changes to calcium oxide (Cab). The water vapor (H2O) released at this time passes through the core 4 and is released to the outside.
undergoes thermal decay. In addition, in the case of aluminum molded products that require heat treatment, the heat treatment temperature is usually around 520℃.
All of the calcium hydroxide (Ca(0)()m) in the core 4 changes to oxidative lucium [CAO] and disintegrates, leaving only a shell of surface 1tII formed of calcium carbonate (CaCOB).

When the gi solidified product is cooled in this way, a contraction force several times the casting pressure acts on the core 4, and the calcium hydroxide (Ca(OH)s) inside the core 4 also collapses. Because of this, Koroto i! After taking out the product for one hour, the hardened surface layer of the core 40 also easily disintegrates into pieces, allowing the core to be easily taken out from the product. Furthermore, when water is injected when taking out the core, the hydroxide power LCa
(OH)i) and oxidizing power (Cab) are easily dissolved in water and discharged. At this time, the calcium carbonate on the surface (
Since the CaCO5JO layer is also separated, it is easy to take out the product and the disintegrated core. Furthermore, even if calcium hydroxide (Ca(OH)B) and oxidizing calcium (Cab) components remain after cleaning with water, the probability of rusting is extremely low compared to other salts, and It completely absorbs the gas and becomes stable by changing to calcium carbonate (CaCOsJ).

In this example, calcium hydroxide (Ca(OH)B) was exemplified as the metal hydroxide as the main material of the core 4, but magnesium hydroxide (Mg(OH)n), etc.
It can also be a metal hydroxide.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the die casting core itself or the surface layer is formed of metal hydroxide powder, and the surface is hardened by reacting with carbon dioxide gas. As a result, when bath water is injected and filled into the cavity of the mold interposed with this core, the temperature of the bath water decreases because the surface of the core is covered with a hard layer of metal carbonate caused by the reaction with carbon dioxide gas. For example, if it is aluminum, it is 70
The surface of the core does not undergo compositional deformation even at high temperatures of around 0℃, and the temperature of the internal metal hydroxide layer does not rise within 1 to 2 seconds after filling, so the casting pressure can be reduced by several seconds. 100 b/an
Even if the temperature reaches k, the core does not break and a predetermined molded product can be obtained.

Furthermore, several tens of seconds after filling, the metal hydroxide inside the core (due to the heat of the bath water) exceeds the decomposition temperature and collapses, and as the product cools and contracts, the core also exerts a large shrinkage force. The surface hardening layer also collapses, allowing the product to be easily taken out after opening the mold, improving workability. Furthermore, when water is poured during product removal, the metal hydroxide is easily dissolved and discharged, making product removal even easier.

[Brief explanation of the drawing]

The figure is a longitudinal cross-sectional view of a die-casting mold in which an aluminum die-casting core is implemented, which is shown as an embodiment of the aluminum die-casting core according to the present invention. 1...Fixed mold, 2...Movable mold, 3...
Cavity, 4... Core, 6... Fusouyu.

Claims (1)

[Claims] A die-casting core characterized by being formed from metal hydroxide powder and having its surface hardened by reacting with carbon dioxide gas.