JPS5964579A - Powder molding process - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for processing a powder compact, which is applied to processing a powder compact using an organic binder as a forming aid.

Conventionally, when processing powder compacts such as ceramics, as shown in FIG. As shown in FIG. 2, a cushioning material 4 made of a polymer, wood, etc. is inserted into a hollow powder compact 1, and a chuck jig 2 of a processing machine is inserted through this cushioning material 4. A method of machining with two tools 3 is generally known. However, in the above case, when the powder compact is fixed to the chuck jig 2, the clamping force is directly applied to the powder compact 1, and
During processing, processing stress is directly applied to the powder compact 1, so the powder compact 1 cracks or residual strain remains, and defects such as sintering cracks and sintering bands occur after the powder compact 1 is degreased and sintered. There was a problem that a sound sintered product could not be obtained due to the occurrence of. In addition, in the latter method, the cost required to process or manufacture the buffer material 4 is high, and the buffer material 4 is often processed at the same time as the powder compact 1, and the buffer material 4 is repeatedly used. There was a problem that it took a lot of man-hours because it could not be done.

In another conventional method, in order to improve the strength of the powder compact 1 itself, a thermosetting resin is mixed into the powder as a binder and then molded, followed by heat curing treatment and then machining. There is a known method of providing According to this method, the strength of the powder compact 1 can be further increased, and when used in combination with the above-mentioned cushioning material 4, degreasing and
The yield of good products after sintering can be increased to some extent.

However, in this method, since a thermosetting resin in which carbonaceous nonvolatile components remain is used as a binder, carbonaceous substances remain after degreasing and sintering. Therefore, there is a problem that it cannot be applied to pressureless sintered silicon carbide materials, which require delicate control of the nitriding material and carbon content, where carbonaceous matter has a negative effect on the properties of the sintered body. Ta.

The invention of wood was made in order to solve all of the above problems, and it is possible to process the molded product non-contact to avoid cracks or distortion without the need for fixing jigs or cushioning materials or applying processing loads to the molded product. The object of the present invention is to provide a novel method for processing a powder compact.

That is, when processing a powder compact using an organic binder such as a thermoplastic resin as a molding aid, the wood invention decomposes and volatilizes the organic binder by irradiating the processed portion of the powder compact with a high energy density heat source. It is characterized in that the powder in the heated portion is scattered and removed by heating the heating portion to a temperature higher than that and supplying jet gas to the heating portion.

Next, the present invention will be explained in detail based on the drawings.

FIG. 3 is an explanatory diagram of a method for processing a powder compact according to the present invention. In the figure, 11 is a ceramic molded body, 12 is a nozzle part of a high energy density heat source generator 13, 14 is a heat source, 1
5 is jet gas.

The ceramic powder compact 11 is made of silicon nitride.

An organic binder such as a thermoplastic resin is added as a molding aid to a conventionally known ceramic powder such as a silicide or oxide such as silicon carbide, and an oxide such as magnesium oxide or aluminum oxide is further added as a sintering aid. The mixture is then molded using existing molding techniques.

The organic binder includes many thermoplastic resins such as polypropylene and polystyrene amide. This thermoplastic resin can be efficiently processed into strong shapes by extrusion molding or injection molding, and it also has the advantage that scraps from defective molded products can be reused. Furthermore, it has the property of increasing its emotional deformability when heated, and dissipating by dispersing, volatilizing, and dissipating above a predetermined temperature. 12 in the figure is a high energy density heat source generator 1
3, and a heat source 14 such as a laser beam 14.
It also serves as the irradiation port and the jet d'r port for the gas 15. However, this is not an essential component of the invention; a jet gas nozzle may be provided separate from the nozzle 12. Examples of the high-energy density heat source 14 mentioned above include laser beams, electron beams, and ion beams. For example, processing using laser beams involves focusing coherent laser beams with the same phase using a lens. This is a method in which the powder compact 11 is irradiated onto the workpiece and instantaneously partially evaporated or melted by thermal energy with a high powder density.
2 laser, ruby laser, etc. are often used. In addition, when the jet gas 15 is mainly composed of ceramic powder, nitrides, carbides, etc., which are averse to oxidation, the jet gas 15 may be N2, CO2, or Ar.

1. It is preferable to use one or more types of inert gases such as He or Ne to shield the processed portion of the powder compact 11 and prevent oxidation. ). This jet gas 15 serves to locally decompose the organic powder by irradiating it with heat s14 such as a laser beam, heating it above the volatilization temperature, and scattering and removing the powder that has lost its bonding strength with its ejection force. It is something. As this jet gas 15, from the viewpoint of the amount of powder removed with respect to the irradiated laser energy, it is optimal to use He gas having a high specific gravity. It is also optional to use inexpensive N2 gas or CO2 gas instead of expensive He scum. On the other hand, ceramic powder is an oxide such as AJZ203t (7)
In this case, it is effective to use a mixed gas in which O2 or air is mixed with one or more of N2 + CO2 + Ar, He, or Ne, in terms of processing efficiency and reduction in gas price. When mixing 02 or air, the mixing ratio is preferably 20% or less for 02 or 60% or less for air.

If the amount exceeds 0220% or air exceeds 60%, the organic binder in the processed part of the powder compact ll will rapidly oxidize and burn, leading to damage to the processed amount, while at the same time it will be difficult to control the processed amount, resulting in precision This is because there is an inconvenience that processing may become impossible.

Next, it is more desirable to set the flow rate of the jet I gas to 1 to 101/min per 1 mm2 of the irradiation area of the heat source 14 such as a laser beam. The reason for this is that if the Li flow rate is less than 2.7 minutes, the shielding effect will be insufficient, and there is a risk that the powder will not be scattered.
This is because if it exceeds 1 minute, the amount of gas supplied becomes excessive and it becomes necessary to fix the powder compact 11, leading to an increase in the manufacturing cost of the product. This gas flow rate is actually determined by the distance between the nozzle 12 and the processed part of the powder compact 11, the area and shape of the nozzle outlet, the energy density of the irradiation beam, the irradiation area, the beam scanning speed, etc. be.

The present invention has the above-described configuration, in which the processed portion 11a of the powder compact 11 is locally heated by irradiation with a high-energy density heat source 14 such as a laser beam, and the organic binder 16 between the powders is dispersed and volatilized. and dissipates outside the workpiece,
Rapidly loses bonding force between powders. In this situation,
Since the shed gas 15 is ejected to the workpiece at a required flow rate, the powder that has lost its binding strength can be scattered outside the workpiece by the scattering force of the gas. Processing progresses by sequentially repeating the above-described powder removal action.

Next, the present invention will be described in more detail with reference to Examples.

Example 1 A powder compact to be used in this experiment was prepared by adding 6% by weight of magnesium oxide and 3% by weight of aluminum oxide as sintering aids to ceramic powder containing silicon nitride as a main component, and further adding molding aids. 18% by weight of polypropylene and 2% by weight of stearic acid were added as an organic binder and mixed, and then produced by injection molding. The size of the plate was 1010 x 20 x 75. The processing conditions are a laser beam capacity of 500W,
The jet gas is N2, and the laser beam irradiation area is 1 mm.
The flow rate per unit was 3 i/min. FIG. 4 shows the state of the processing at this time.

Table 1 is a table showing the machining width and machining depth when the irradiation beam diameter, electric power, and beam scanning speed were variously changed based on the above conditions.

1yOpen'a59-[14579(4) As is clear from the table, by appropriately setting the power density and beam scanning speed, it becomes possible to process various shapes, such as cutting, drilling, and grooving. At this time, the shape of the bottom of the processed portion was a shape corresponding to the energy density distribution of the laser beam, and in this example, since a Gaussian distributed beam was used, it was semicircular.

Therefore, by controlling the energy density distribution of the laser beam in various ways, any shape corresponding to the distribution can be obtained. The above-processed powder compact was heated and degreased in a nitrogen scum atmosphere at a heating rate of 5°C/hour from normal crystal to goo'c, but no deformation or defects on the machined surface were observed. There wasn't. For comparison, laser processing was performed under processing conditions such that the flow rate of the jet gas was reduced to 0.5 Jl/min per rnrn2 of surface area of the applied part.

As a result, the organic binder in the processed portion was burned during processing, making it impossible to obtain a beautiful processed surface. This means that in this example, the laser beam irradiation area is 1 to 1 oi per 1 mm2 of the laser beam irradiation area.
It is clear that it is better to set it to y minutes.

Example 2 An example of the present invention using an oxide (A J2203) as the ceramic powder will be described below.

The ceramic powder molded body to be used is first made of oxide (A
J-203) 18% by weight of polystyrene and 2% by weight of stearin m were added as molding aids to the powder, and after mixing, it was molded into 1010X20X7 by an injection molding machine.
It is molded to the size of 5.

In addition, the jet gas used for beam processing is N2: 90%.
, 02; 10% mixed gas, and the other stripes 14 were carried out in the same manner as in Example 1 described above, and the ceramic powder molded body 11 was beam-processed as shown in FIG.

Table 2 is a table showing the machining width and machining depth when the beam diameter, power density, and beam scanning speed on the surface of the workpiece are changed.

Comparing Table 2 with Table 1, it can be seen that at the same power density and beam scanning speed at the same applied lower surface, the diene l
'By combining 4 swords with 02 swords, 1 piece of power]
It can be seen that the two efficiencies are opposite. It has been found that when the ceramic powder is a molten powder, adding 02 to 1 is effective in improving processing efficiency. Furthermore, for comparison, when beam processing was carried out under the same conditions with the incorporation ratio of 02 increased to 30%, the organic binder in the added part burned and a beautiful machined surface could not be obtained. Therefore, when the ceramic powder is an oxide, the gas is N2
It has been found that it is effective to mix 20% or less of 02, or 60% or less of air with one or more gases of +CO2, Ar, He, or Ne. Furthermore, the beam-processed ceramic powder molded body was degreased by being heated in the air at a heating rate of 5°C/hour from room temperature to 8 oo"c, or the molded body was not deformed and there were no defects on the machined surface. I was not able to admit.

Back Engraving This example shows an example in which ceramic parts for a gas turbine combustion tube were actually manufactured.

First, 25% by weight of graphite was added to silicon carbide as a ceramic powder, and 3% by weight of Avicel was added as an organic binder to form 4I, and then a rubber press was used to form an intermediate gas turbine combustion tube with a wall thickness of 2 mm. created a body. Next, as shown in FIG.
7", and air holes 23 are formed on the side of this intermediate molded body 21.
was cut according to the present invention. The laser device used in the implementation was a CO2 laser device with an output of 500 W, and the processing conditions are shown in Table 3.

7''/' Third surface: Next, the beam-processed intermediate molded body 21 was degreased and then silicified and sintered, and there was no defect.
It has been demonstrated that this method can be applied to actual manufacturing.

Embodiment 4 In this embodiment, as shown in FIG. 6, a die gas nozzle 36 is provided separately from the laser beam nozzle 32, and the die gas 35 is flowed through this nozzle 36 at the same time. A laser beam 34 is irradiated from the nozzle 32,
Wider than the powder compact 31! Sei 37 was laser processed. Even with this method, it is possible to form grooves of any desired width by appropriately selecting the force and machining conditions.

Embodiment 5 FIG. 7 shows a case in which seal-ring grooves were actually laser-machined on the outer peripheral surface of a ceramic ink part of a radial rotor shaft made by injection molding ceramic ink powder using the method described in Example 4. The radial rotor shaft 41 as shown in FIG.
It is S by laser processing the wide groove 37 while rotating it.

As is clear from the above detailed description, according to the present invention, a force of 11 is applied to a powder compact using an organic binder as a forming aid without fixing it to a jig. Cutting, drilling holes in the powder compact without contact,
Alternatively, processing such as grooves can be applied to the powder compact. It is possible to process accurately and efficiently without causing defects such as cracks and distortions.

Furthermore, in the conventional method, when rough processing a molded body, a special jig such as a buffer phase, a curing process using a thermosetting resin as a binder, or a pre-sintering process are required, but according to the present invention, -cutting is possible. It is no longer necessary, and has great industrial significance.

[Brief explanation of the drawing]

1 and 2 are longitudinal sectional views illustrating the rough processing method for powder compacts according to the conventional method, FIG. 3 is a schematic sectional view illustrating the processing method for powder compacts according to the present invention, and FIGS. 7 to 7 are explanatory diagrams showing each embodiment of the present invention. 11.21, 31.41...Powder compact, 14°24
．． 34... Heat source (laser beam), 12, 22.32
...Heat source nozzle, 15,25.35...Jet gas, 36...Jet gas nozzle. Patent Applicant 1] San Jidosha Co., Ltd. Representative Patent Attorney Yutaka Oshio Figure 1ml Figure 2 Figure 4 Figure 6 Wj7FI! I

Claims (3)

[Claims] (1) When processing a powder compact using 41 Machine Piter as a forming aid, the processed portion of the powder compact is irradiated with a high energy density heat source to decompose the organic binder.
A method for processing a powder compact, which comprises heating the powder to a temperature higher than its volatilization temperature and supplying jet gas to the heating section. (2) Gases include N2, C02, and Ar. One or more types of gas such as He or Ne, and the meteor of the gas is 1 mm2 per 1 mm2 of the irradiation area of the high energy density heat source.
The method for processing a powder compact according to claim (1), wherein the processing speed is 10 A/min. (3) Jet gas is N2, Co2, A, r. 20% or less of 0 in one or more of He or Ne
2, or a mixture with 60% or less of air added, and the flow rate of the gas is equal to the irradiation area of the high energy density heat source.
Claim range f of 1 to Roll/min per mm2
The method for processing a powder compact according to item iS(1).