JPH02203192A - Rapid degreasing furnace of powder moldings - Google Patents

Abstract

PURPOSE:To reduce the consumption of inert gas and carry out the degreasing of moldings in a short time period by a method wherein the binder contained in the moldings is discharged and evaporated while the mouldings are pressurized by using the volume expansion of inert gas due to the temperature rise in a furnace. CONSTITUTION:After moldings 14 containing binder are put into a furnace 1, a vacuum inducing needle valve 6 is operated so as to evacuate the furnace 1, a gas introducing needle valve 7 are opened to introduce inert gas such as Ar, N2, etc. and the furnace 1 is heated until the temperature reaches a set point. The pressure in the furnace 1 rises with the rise of temperature, so that rapid discharge and evaporation of binder from the moldings are controlled and defects such as cavities, bulge, etc. are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a degreasing furnace for removing binder from a powder molded product, and particularly to a degreasing furnace for powder molded products in which the inside of the furnace is pressurized to degrease the powder molded product. in between.

[Prior Art] Conventionally, injection molded products containing 50 to 60 volume % of ceramic powder or metal powder and 40 to 60 volume % of binder such as wax or polymer have been degreased by heating the molded product in a heating furnace to remove the binder. flows out of the molded product and is removed by vaporization. At that time, if the atmosphere in the heating furnace is kept under pressure, the rapid generation of gas from the molded product will be suppressed, and defects such as pores and blisters that are likely to occur during degreasing will not occur, and the atmosphere in the heating furnace will be kept under pressure. It is known that degreasing can be performed more quickly than in the case of

[Problem to be solved by the invention] However, as a means to pressurize the atmosphere inside the furnace,
There is a method of pressurizing the atmosphere or an inert gas such as Ar or N2 using a compressor, or a method of pressurizing using the pressure of a gas cylinder such as Ar or N2. A pressurizing device is required because the binder trap is discharged together with the atmosphere or inert gas that is being input while maintaining the temperature.Also, when using an inert gas, the amount of gas consumed increases because the inert gas is forced to flow. However, there was a problem that running costs were high.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, an object of the present invention is to provide a degreasing furnace that consumes less inert gas and can degrease molded products in a short time.

[Means for solving 111] In order to achieve the above object, the quick degreasing furnace for powder molded products according to the present invention includes a heating chamber with an airtight structure provided in the heating furnace,
A binder trap with an airtight structure and a cooling function is connected, and a powder molded product made by kneading with a binder such as wax or polymer is placed in the heating chamber, and after filling the heating chamber with inert gas, the heating is performed. The chamber is heated, and the molded article is pressurized by utilizing the volumetric expansion of the inert gas as the temperature rises within the heating chamber, while the binder contained in the molded article flows out and vaporizes.

[Function] According to the above configuration, the binder contained in the molded product flows out and vaporizes while pressurizing the molded product by utilizing the volumetric expansion caused by the heating of the inert gas filled in the sealed heating chamber. Therefore, it is possible to quickly degrease the molded product using a small amount of inert gas without causing defects such as holes or blisters in the molded product.

[Example 7] Hereinafter, an example of the method for manufacturing a rapid degreasing furnace for powder molded products according to the present invention will be described in detail with reference to the drawings.

In FIG. 1, a heating chamber l with an airtight structure is provided in the heating furnace, cooling water 2 is arranged around the airtight structure, and a lid 3 is provided at the lower end.
A binder trap 4 with a binder attached thereto is connected to the heating chamber 1. At the connection between the heating chamber 1 and the binder trap 4, there are a needle valve 5 for leakage, a needle valve 6 for evacuation, a needle valve 7 for gas introduction, a safety valve 8, and a solenoid valve 9 for pressure control.
, a pressure gauge 10, and a pressure sensor 11 are installed. Further, a heating element 12 is installed in the heating chamber 1, and the heating chamber 1 is surrounded by a heat insulating material 13.

The molded product 14 containing the binder is placed in the heating chamber 1, the vacuum needle valve 6 is operated to create a vacuum in the heating chamber 1, and then the gas introduction needle valve 7 is injected with Ar, N2, etc. Inert gas is introduced and heating chamber 1 is heated until it reaches a set temperature. Heating chamber 1 when using air as the gas
There is no need to evacuate the inside of the molded product 14, and the air introduced into the heating chamber 1 when taking the molded product 14 in and out of the molded product 14 may be kept in a sealed state for heating.

The pressure of the inert gas is Pl, the volume is v5, the temperature is T(0
K), since PV/T=constant, the pressure inside the heating chamber 1 increases as the temperature rises, suppressing the rapid outflow and vaporization of the binder from the molded product, and filling the pores of the molded product. ◆Prevent defects such as blistering. The vaporized binder is led to the binder trap 4, where it is cooled and solidified again.
Since it collects at the bottom of the binder trap 4, the resolidified binder 15 can be removed by removing the lid 3 after degreasing.

The safety valve 8 is installed to prevent the heating chamber 1 and the binder trap 4 from exceeding an allowable pressure.

Using a pressure kneader, 56% by volume of carbonyl iron powder with an average particle size of 5 μm, 45% by volume of a binder containing microcrystalline wax, low-molecular acrylic, and EVA was mixed into 150% by volume using a pressure kneader.
Kneaded for 1 hour at ℃, crushed into particles of 3 mm or less after cooling,
The mixture was placed into an injection molding machine cylinder heated to 150°C.

A mold for molding a bar measuring 6 x 4 x 50 mm was used, and the molding was carried out at an injection pressure of 800 kg/c++2.

20 molded products were processed in a conventional normal pressure degreasing furnace and 10 in a rapid degreasing furnace according to the present invention for comparison. In the normal pressure degreasing furnace, the temperature is 5°C or 10°C per hour while flowing N2 gas.
Heat up 5 pieces each from room temperature to 500℃ at a heating rate of Five pieces each were heated from room temperature to 500°C at a heating rate. In the rapid degreasing furnace, the pressure of 1 atm at room temperature (18°C) was reduced to 50
When the temperature was raised to 0°C, the pressure became 2° and 4 atm. However, as shown in Figure 2, the furnace pressure did not rise linearly during the temperature rise, and the reason why it became slightly higher in the middle was due to the binder vaporized from the molded product. This is due to gas pressure.

When molded products that had been degreased as described above were examined for defects using external appearance and X-ray photography, as shown in Table 1, products degreased using conventional atmospheric pressure methods were found to have defects such as cracks, blisters, and holes. In contrast, in the case of the rapid degreasing furnace according to the present invention, defect-free degreased products were obtained even at a heating rate of 10° C./hour.

Therefore, it is possible to more than double the temperature increase rate compared to the conventional normal pressure degreasing method, and by simply introducing N2 gas at the beginning, gas consumption can be saved and economical pressure degreasing can be achieved. It turns out it's possible. In Table 1, the numbers in parentheses in the column for the percentage of non-defective products after degreasing are the number of non-defective products/the number of degreased products.

In this 8V example, a pressure control valve 9 is installed, so the heating chamber is pressurized before the temperature rises, and degreasing work can be performed while maintaining a constant pressure up to the maximum degreasing temperature specified in Table 1. It is possible. In addition, although N2 gas was used as the inert gas, it is not limited to this, and Ar, air, etc. may also be used. However, when using air, the temperature inside the furnace should be kept below 320°C to avoid the risk of explosion. It is necessary to keep it to

[Effects of the Invention] As explained above, according to the present invention, a molded product is pressurized by utilizing the volumetric expansion caused by the heating of the air or inert gas filled in a sealed heating chamber. Since the binder flows out and evaporates, the temperature rise rate is reduced by 2 times compared to the conventional normal pressure degreasing method, without creating defects such as pores and blisters that occur when the binder flows out from the molded product. It is possible to perform degreasing in a short time by more than double the amount, and also to save on inert gas consumption.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view of a quick degreasing furnace for powder molded products according to an example, and FIG. 2 is a graph showing the relationship between furnace temperature and furnace pressure. 1... Heating chamber 4... Binder trap 14... Molded product Figure 1 Patent applicant Komatsu Ltd. Furnace temperature wc2vi! J

Claims (1)

[Claims] A binder trap 4 with an airtight structure and cooling function is connected to a heating chamber 1 with an airtight structure provided in a heating furnace, and a molded product of ceramic powder, metal powder, etc. is kneaded with a binder such as wax or polymer. 14 into the heating chamber 1,
After filling with an inert gas, the heating chamber 1 is heated, and while pressurizing the molded product 14 by utilizing the volumetric expansion of the inert gas accompanying the temperature rise in the heating chamber 1, the molded product 14 is heated. A quick degreasing furnace for powder molded products, characterized in that the binder flowing out and vaporizes.