JPH03465A - Method for removing core - Google Patents

Abstract

PURPOSE:To omit core sand burning process by controlling supply of oxygen- containing gas so that core temp. comes to in the prescribed temp. range at the time of burning organic binder by supplying the oxygen-containing gas to the core before opening dies after casting. CONSTITUTION:Molten Al alloy having the prescribed temp. is poured from a sprue 3. The molten metal flows into a product part 4 formed with the dies 2 and core 1 and fills up. At the time of filling up the sprue with the molten metal, the pouring is stopped and the molten metal is solidified in the dies 2. Air as the oxygen-containing gas is blown into the core in the dies 2 from a blowing hole 5 at the prescribed pressure as shown with the arrow mark. The air is discharged to out of the dies from exhaust hole 6 while burning the organic binder in the core 1 already heated. The value set with pre-test is inputted in a timer 7 and based on this value, a solenoid valve 8 is opened/ closed. The core temp. does not exceed the solidified temp. of Al alloy and the organic binder is sufficiently burnt. By this method, the core can be easily removed without developing deflective casting product.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application 1] The present invention relates to a method for removing a core, and more particularly to a method for removing a core after casting in a casting method using a metal mold as a mold.

[Prior art 1] In a casting method using a core using an organic binder, there is a method of supplying oxygen-containing gas such as air to the core in order to easily remove the encased core after casting. known 0
For example, in JP-A No. 62-259661, in mold casting using a core, air is supplied to the core in the mold when the solidification of the cast product by the molten metal is almost completed, and a mold release agent is released. A method of collapsing a core within a mold is disclosed. Further, Japanese Patent Application Laid-Open No. 157755/1983 discloses a method for manufacturing a light alloy cylinder block by a method substantially similar to the above method.

Furthermore, the present applicant has disclosed the method described in JP-A-58-141814, in which a gas supply port is brought into contact with a core using an organic binder, and then the gas supply port is cast in by pouring metal. We also proposed a core removal method in which oxygen-containing gas is supplied from the gas supply port.

However, in the above-mentioned method, a gap is created at the mold mating surface due to causes such as warping of the mold, processing accuracy, and foreign matter caught on the mold mating surface. In order to supply oxygen-containing gas such as air into the core, it must be supplied at a pressure that overcomes the ventilation resistance of the core, so a large pressure is required during supply. At this time, if there is a gap between the mold mating surfaces, the supplied gas flows through the gap where the ventilation resistance is lower and does not pass through the inside of the core, resulting in an inconvenience. Furthermore, when vent holes are provided in the core to reduce ventilation resistance, the oxygen-containing gas mainly flows only through the vent holes, making it difficult for the oxygen-containing gas to spread throughout the core.

In order to solve the above-mentioned inconvenience, the present applicant fits the tip of a pipe for supplying oxygen-containing gas to the outer periphery of the core wood,
We have also proposed a method in which the end of the pipe is cast-inserted during casting to ensure sealing performance, and oxygen-containing gas is supplied from the pipe after solidification of the product. It is necessary to provide a gap corresponding to the wall thickness of the pipe between the mold and the mold, and if such a gap exists, dimensional defects are likely to occur due to misalignment of the core.

Therefore, the present applicant further proposed in Japanese Patent Application No. 1-44916 that a groove was formed in advance in the mold and/or the groove for closing the gap in the mold mating surface leading to the core wood by guiding the poured molten metal. Alternatively, we proposed a core removal method in which the organic binder is formed in the core and the organic binder is burned by supplying an oxygen-containing gas from the wood of the core to the core before opening the mold after casting.

According to the method described in the specification of Japanese Patent Application No. 1-44916, the poured molten metal is guided by the groove and closes the gap in the mold mating surface leading to the core wood part around the core central part. When oxygen-containing gas is supplied from the core wood to the core before opening the mold after casting, the organic binder is supplied to the entire core without leaking from the gap between the mold mating surfaces. can be burned and the core can be disintegrated in a suitable manner.

[Problem to be solved by the invention] The above-mentioned Japanese Patent Application Laid-Open No. 141814/1981 and Japanese Patent Application No. 1989/1999
In the method described in the specification of No. 4916, since oxygen-containing gas is simply supplied to the core and no control is performed,
The core is heated to 350-450℃ by pouring, and is further heated by combustion of the organic binder, resulting in a temperature of 500-70℃.
The temperature rises rapidly to 0°C. At this time, even if the rough material in contact with the core is once solidified, it is heated again, causing abnormalities in the solidification form such as remelting and crystal transformation, resulting in casting defects.

The present invention is intended to solve the problems in the prior art, and its purpose is to prevent overheating due to a rapid temperature rise of the core when supplying oxygen-containing gas,
Another object of the present invention is to provide a core removal method that can sufficiently burn out the organic binder in the core.

[Means for Solving the Problems 1 That is, the core removal method of the present invention reduces the core temperature when supplying oxygen-containing gas to the core to burn the organic binder before opening the mold after casting. The method is characterized in that the oxygen-containing gas is supplied intermittently or the amount of the oxygen-containing gas supplied is increased or decreased so that the temperature is within a predetermined temperature range.

Air is convenient for practical use as the oxygen-containing gas, but gases with other compositions may be used as long as they contain enough oxygen to burn the organic binder.Properties such as pressure and temperature should be selected as appropriate. .

The temperature range of the core to be controlled is determined by considering the type of casting metal, the type of organic binder, the control method, etc.

The oxygen-containing gas may be supplied intermittently, or the supply amount may be increased or decreased. Of course, the above two methods may be combined as appropriate.

To supply oxygen-containing gas intermittently, for example, open and close a valve installed in the oxygen-containing gas piping automatically or manually at intervals confirmed in a pre-test, or detect the temperature of the core. Install a sensor at a suitable location to
The valve may be opened and closed automatically or manually based on the temperature.

Instead of the above method, the amount of oxygen-containing gas supplied may be increased or decreased. In this case as well, the method can be carried out in the same manner as the above method except that instead of opening and closing the valve provided in the oxygen-containing gas pipe, the degree of opening of the valve is adjusted.

It is even better if a computer is used in combination with temperature sensors, electromagnetic valves, flow control valves, etc., since even complex control can be performed automatically.

[For production]

By controlling the core temperature within a predetermined temperature range, problems during sand firing of the core, such as remelting of the rough material, can be eliminated.

[Examples] The present invention will be explained in further detail in the following examples. Note that the present invention is not limited to the following examples.

Example 1 An example in which the present invention is applied to aluminum mold casting for an intake manifold for an automobile engine is shown in FIGS. 1 and 2.
As shown in the figure.

In FIGS. 1 and 2, 1 is a sand core for an intake manifold using an organic binder as a binder, and 2 is a mold (an upper mold and a lower mold).

FIG. 1 shows a side view of the core 1 set in a horizontally split mold 2, and FIG. 2 shows a plan view.

In the above state, aluminum alloy for casting at a temperature of 700±10° C. was poured from the pouring port 3. The molten metal flows into and fills the product section 4 formed by the mold 2 and the core 1. When the molten aluminum alloy fills the pouring port 3, pouring is stopped and the molten metal is solidified in the mold 2.

When the solidification of the product part 4 was completed, air as an oxygen-containing gas was blown into the core 1 in the mold 2 at a pressure of 4 Kg/am from the blowing port 5 as shown by the arrow. The air is discharged from the mold 2 through the discharge port 6 while burning the organic binder in the core 1, which has already been heated by the heat generated during pouring. The obtained value was input into the timer 7, and the solenoid valve 8 was opened and closed accordingly.

The change over time in the temperature of the portion 1a of the core 1 at this time is shown by a solid line in FIG. As is clear from Fig. 3, since the solenoid valve 8 is opened and closed at predetermined intervals (on-off control), the temperature of part 13 never exceeds the solidification temperature of the aluminum alloy, 560°C, and the organic binder is The temperature is controlled within a predetermined range until sufficient combustion is achieved. In addition, in the case of the conventional method where air is simply blown in and no control is performed, the temperature at part 13 exceeds the solidification temperature of the aluminum alloy, 560°C, and reaches 700°C, as shown by the broken line in Figure 3. C, and has an adverse effect on the raw material, such as remelting.

Example 2 As shown in FIG. 4, the procedure was the same as in Example 1 except that the opening of the flow control valve IO was adjusted based on the signal from the temperature sensor 9 provided in the mold 2 (upper mold). I blew air into it. In the case of this embodiment, the temperature of the core 1 can be controlled within a predetermined temperature range with even less temperature fluctuation of the core 1 after the start of air blowing than in the first embodiment.

[Advantageous Effect 1 of the Invention As described above, the core removal method of the present invention allows the core temperature to reach a predetermined level when oxygen-containing gas is supplied to the core to burn the organic binder before opening the mold after casting. The oxygen-containing gas is supplied intermittently or the supply amount of the oxygen-containing gas is increased or decreased so that the temperature is within the range, so that the core is not heated above the solidification temperature of the raw material. Therefore, the core can be easily removed without causing defects in the casting due to remelting of the raw material.

This makes it possible to double the core sand firing process in the conventional casting process, eliminating the need for a separate sand firing process for the purpose of removing core sand, resulting in more effective use of factory equipment space and energy savings. Shows great effects.

[Brief explanation of the drawing]

Figure 1 is a side view of a core set in a mold according to Example 1 of the core removal method of the present invention, Figure 2 is a plan view of Example 1, and Figure 3 is a method of the present invention. FIG. 4 is a side view of a core set in a mold according to Example 2 of the method of the present invention. In the figure, l ... core 2 ... mold 3 ... pouring port 4 ... product part 5 ... blowing port 6 ... discharge port a ... timer 8 ... solenoid valve 9...Temperature sensor error...Flow rate control valve Patent applicant Toyota Motor Corporation (and 2 others) Figure 2

Claims (1)

[Claims] When oxygen-containing gas is supplied to the core to burn the organic binder before opening the mold after casting, the oxygen-containing gas is intermittently supplied so that the core temperature is within a predetermined temperature range. A method for removing cores, characterized in that the amount of oxygen-containing gas supplied is increased or decreased.