JPH02145704A - Composition for compacting and manufacture of sintered body using it - Google Patents

Abstract

PURPOSE:To manufacture a sintered product without any crack and bulging, etc., by adding the specific organic binder to raw material powder of metal powder or further mixing powder with ceramic powder and sintering after compacting and debindering the melted and kneaded composition. CONSTITUTION:The powder of various kinds of metals or alloy of stainless steel, etc., or/and oxide, carbide or nitride series ceramic powder of Al2O3, SiC, Si3N4, etc., having 0.01-50mum average particle diameter, are mixed. After mixing 40-50wt.% of material mixing 30-60wt.% thermoplastic component having >=130 deg.C heat deformation temp. of polyacetal, etc., and 40-70wt.% component having 30-100 deg.C melting temp. of polyethylene glycol, etc., as the organic binder, with 50-60wt.% the powder mixed material of the metal and the ceramic, this is melted and kneaded to manufacture the composition for compacting. This composition is compacted into the aimed shape with injection-molding method, and after removing the binder by heating under oxidizing atmosphere, this is sintered under vacuum at <=10<-3>Torr.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a molding composition comprising a metal powder or a mixed powder of metal powder and ceramic powder and an organic binder, and a method for producing a sintered body using the same. .

[Prior Art] Conventional molding compositions consisting of metal powder or ceramic powder and an organic binder include heat-resistant polypropylene, methacrylic acid ester, polystyrene, ethylene-vinyl acetate copolymer, and low-density polyethylene as the organic binder. Plastic resins or plasticizers and lubricants such as paraffin wax, diethyl phthalate, and stearic acid are used in combination with these resins.

It is also known to obtain a sintered body by injection molding such a composition, removing the organic binder from the molded body (this process is called degreasing), and then sintering (for example, US Pat. No. 2,593,943. Kaisho 58-223662
Publication No.).

[Problems to be Solved by the Invention] However, with conventional compositions, when degreasing, the molded body easily deforms due to its own weight, or cracks or bulges due to decomposition gas. It was necessary to perform degreasing by burying it inside to prevent deformation, or by suppressing decomposition gas generation at a slow temperature rate of usually 1 to 10°C/hr. Therefore, before proceeding to sintering, a process of brushing off powder adhering to the surface of the molded body is required, and degreasing requires a long time, making industrial production difficult.

The present invention was created in order to eliminate the drawbacks of the prior art as described above, and it is an object of the present invention to provide a composition that does not undergo thermal deformation during degreasing and can be degreased in a short time, and to provide a composition that can be degreased in a short time. The purpose of the present invention is to provide a method for efficiently producing a sintered body free from defects such as deformation, cracks, and blisters.

[Means for Solving the Problems] The molding composition of the present invention comprises metal powder or a mixed powder of metal powder and ceramic powder, and a thermoplastic component (component A) having a heat distortion temperature of 30°C or higher. A composition prepared by mixing an organic binder with a melting point of 3.
The composition further contains a component having a temperature of 0 to 100'C (component B). Here, the heat distortion temperature is ASTM 0641
1, and shall be expressed as a value measured at a load of 4.6 kg/as''.

Moreover, the sintered body of the present invention! ! In the two-way method, a molding composition is prepared by melting and kneading metal powder or a mixed powder of metal powder and ceramic powder and an organic binder consisting of Δ component or A 55 minute and B component, and this composition is mixed into the desired shape. This is a method for preparing a sintered body, which is characterized by forming the molded body into a shape, then heating and removing the organic binder from the molded body, and sintering the obtained degreased body.

In the molding composition of the present invention, the components include polycarbonate, polyphenylene oxide, polyphenylene sulfide, polyvinylidene fluoride, polyacetal (a homopolymer consisting only of trioxane, and combinations of trioxane and ethylene oxide, dioxolane, substituted dioxolane, 114-dioxane, etc.). copolymer)
, polyamide (e.g. nylon 6.11.12.66
or these copolymers), polyesters (e.g.
polyethylene terephthalate, polybutylene terephthalate), polyaryl sulfone, polyaryl ether, polysulfone, polyether sulfone, polyether ether ketone, etc., and it is possible to use one type or a mixture of two or more of these as appropriate. can. Among these, thermoplastic components having a heat distortion temperature of 150° C. or higher are preferred, and among them, polyacetal is particularly preferably used because it has a low melt viscosity, is easy to mold, and has good thermal decomposition.

The organic binder has a melting point of 30 to 10 with the above component A.
It is preferable to use a component at 0° C. (component B) in combination. Such components include polyalkylene glycols (normal molecules such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide-propylene oxide copolymer, etc.)
waxes (petroleum wax, natural wax, synthetic wax, etc.), various low molecular weight compounds that are solid at room temperature (higher fatty acids such as stearic acid, metal soaps such as aluminum stearate, distearylamine, etc.) aliphatic amines, various surfactants), etc., and one type or a mixture of two or more of these can be used as appropriate.

When polyacetal resin is used as component A, polyalkylene glycol is preferred as component B from the viewpoint of compatibility, and polyethylene glyfur is particularly preferred. Molecule 1 of polyethylene glyfur is usually 1000 to 2
10,000 to 10,000 is used, but those with a molecular fi of 11,000 to 10,000 are more preferable because they are excellent in moldability and deformation prevention effect during degreasing.

In addition to components A and B, a third component (component C) having a heat deformation temperature of less than 130"C and a melting point of more than 100"C may be added to the organic binder in order to improve moldability.

Examples of such C component include polyethylene, polypropylene, poly(4-methylpentene-1), polystyrene, poly-α-methylstyrene, ethylene-vinyl acetate copolymer, polymethacrylic acid ester, polyethylene oxide, etc. However, from the viewpoint of compatibility, polyethylene oxide is preferred.

The Yf machine binder further contains plasticizers that are liquid at room temperature (diethyl phthalate, dibutyl phthalate, etc.), surfactants and various coupling agents to improve the binder's wettability with gold powder powder, etc., within the range normally used. May contain.

Component A in the organic binder provides fluidity to the composition and also serves to prevent deformation during degreasing. Since a component with a heat distortion temperature of less than 130°C would have insufficient deformation prevention effect, the heat distortion temperature of component A was set at 130°C or higher. The amount of component A in the binder is usually 20 to 10
0% by weight, preferably 30-60% by weight. If the amount of component A is less than 20% by weight, the strength of the molded product will be insufficient and handling will be difficult.

Component B increases the fluidity of the composition to facilitate injection molding, further enhances the deformation prevention effect during degreasing, and plays the role of accelerating the degreasing speed.

If the melting point is below 30°C, the strength of the molded product will be weakened,
If the temperature exceeds 100°C, the deformation prevention effect becomes insufficient, so the melting point range was set at 30 to 100°C. The proportion of component B in the binder is usually 0 to 80 mM%, preferably 40 to 70% by weight. If Component B exceeds 1% by weight of 80%, the strength of the molded product will be insufficient.

The amount of C component in the binder is usually 0 to 60% by weight.
, preferably 0 to 30% by weight. The same of C component is 60
%, the molded product will become deformed during degreasing.

In the present invention, metal powders include iron, aluminum,
Metal powders such as copper, titanium, molybdenum, zirconium, cobalt, nickel, and chromium, and alloy powders containing these metals as main components (e.g., stainless steel powder, high-speed copper powder,
cemented carbide powder, magnetic material powder, etc.), and one of these
One species or two or more species can be appropriately mixed and used as required.

Furthermore, ceramic powder may be added to these metal powders in a range of 0 to 95% by weight. Such ceramic powders include oxides (aluminum oxide, silicon oxide, zirconia oxide, titanium oxide, mullite, cordurite, etc.), carbides (silicon carbide, boron carbide, zirconia carbide, etc.), and nitrides (silicon nitride, aluminum nitride, nitride). There are powders such as boron, titanium nitride, etc.

In addition to powder, these powders include sintering aids, forming aids,
Pond powder or the like may be added in advance as appropriate to improve physical properties.As for the method of addition, it may be mixed into the powder, or it may be coated on the surface of the powder.

The average particle size of metal powder and ceramic powder is usually 0.
Olam ~50 μm, preferably 0.1 μm ~
It is 20am. If the particle size is smaller than 0.01 μm,
Although the sinterability is improved, it is bulky and difficult to handle, and the moldability is deteriorated. If the particle size exceeds 50 μm, sinterability will deteriorate.

In the composition of the present invention, the content of the powder in the entire composition is usually 40 to 70% by volume, preferably 50 to 60% by volume.
It is. If the amount of powder exceeds 70% by mass, it becomes difficult to uniformly knead the powder and binder, and injection molding becomes difficult. On the other hand, if it is less than 40% by volume, the molded article will be significantly deformed during degreasing.

The composition of the present invention and the method of molding the composition to obtain a sintered body are shown below.

The IHlii product of the present invention can be produced by melt-mixing the components, cooling and then crushing to coarse pulverization, or by pelletizing. In the above, the kneading can be carried out using a conventional mixing machine such as a Banbury mixer-blast mill, a kneader 1 pressure kneader-roll mill, or a screw extruder. The mixing temperature is usually 150 to 350°C, preferably 15°C.
1 at 0-2506C. The crosstalk time is usually 20 minutes to 2 hours.
Preferably it is 30 minutes to 1 hour.

If necessary, each component or mixture may be dried before cross-talking. The kneading method is to prepare and knead all the ingredients at once, or to knead only the binder ingredient first.
There is a method in which ceramic powder or metal powder is then added and kneaded, and a method in which a binder component is added later.

When injection molding is performed using the composition of the present invention, a conventional injection molding machine such as a plunger type or a screw type can be used. The molding conditions vary depending on the mold shape and the silk material used for molding R14, but the molding pressure is usually 100-3QOO.
Kg/co+', preferably 200-2000Kg/c
m”, the molding temperature is usually 150 to 350°C, preferably 1
It is 50-250°C. In addition, extrusion molding, press molding, etc. can also be performed using the composition of the present invention. For compositions that are easily thermally decomposed by heating, a method of kneading and molding under reduced pressure or in an inert atmosphere may be adopted.

Degreasing is carried out in an oxidizing, reducing or inert gas atmosphere under reduced pressure, normal pressure or increased pressure, at a heating rate of usually 1 to 60°C/hr, preferably 10 to 40°C/hr, to 250 to 500°C.
This is carried out by raising the temperature to a certain degree, preferably 250 to 350°C, and maintaining the temperature at that temperature for usually 0 to IO hours, preferably 1 to 5 hours.

Molded objects made of the composition of the present invention do not need to be embedded in powder or supported with a jig in order to maintain their shape, and can be degreased by being lined up on a shelf in a degreasing furnace as they are. Here, the degreasing time can be shortened by using a shelf board on which the molded body is placed that allows ventilation and by applying a flow of atmospheric gas to the lower surface of the molded body. As such a shelf board, a full mesh made of stainless steel or the like or a grid made of ceramic or the like is used.

Sintering is usually performed in an oxidizing, reducing, or inert gas atmosphere under vacuum, normal pressure, or pressurization at a temperature of about 600 to 2000°C. 4 Hot water speed is usually 50~1000°
C/hr and held at maximum temperature for 10 minutes to 10 hours. When sintering is carried out in vacuum, the degree of vacuum is usually IO-“to
rr or more, preferably 10-3 torr or more.

The conventional method of embedding degreasing in powder requires a step to shake off the powder adhering to the surface of the degreaser before sintering, making it difficult to perform the process from degreasing to sintering continuously. However, according to the method of the present invention, such a step is unnecessary, and it is possible to continuously perform up to sintering in the same heating furnace.

F Example J Hereinafter, the present invention will be further explained with reference to Examples, but the present invention is not limited thereto.

Example 1 Two types of metal powder (iron powder with an average particle size of 4 μm and an average particle size of l
5US304) and thermal deformation/! degree is 130°C
The above four types of resins (polycarbonate (PC), polyacetal copolymer (Co-POM), polyacetal pomopolymer (POM), polysulfone (PSF))
A total of 8 molding compositions were made by combining 1.

The kneading was carried out using a pressure kneader at a temperature of 180 to 360°C for about 45 minutes depending on the resin used, and the amount of metal powder was 56% by volume of the composition. Next, the above composition was heated and pressed at 200 to 380°C to give a test piece (roomXl, roomX4mm) as shown in the first section.
It was molded into.

Next, the described shape was placed on support rods installed at fixed intervals L (1, 2, and 3 cm) as shown in Figure 2, and heated at a heating rate of 10 ° C / hr in a light furnace. The temperature was raised to 300 to 500°C depending on the resin used, and 90% or more of the resin content was removed by thermal decomposition.

Next, the degree of deformation of the obtained degreased body was evaluated by deformation fTt(h) as shown in FIG. The results are shown in Table 1. Polycarbonate with a heat distortion temperature of 138°C and 5
Although some deformation was observed in the test piece made of US304 when the spacing between the support rods was wide, the heat deformation temperature was low! 50
No deformation was observed in other test pieces using the °C50 heavy resin.

Example 2 As a metal powder, a mixed powder (F
EW-8 powder), polyethylene 'J' was added to the POM or Co-POM used in Example 1 as an organic binder.
:I-ru(PEG-4(+00: average molecular fi 4
000, melting point 56°C) was added and kneaded at the composition ratio shown in Table 2. The mixture was kneaded using a pressure kneader at 150 to 180° C. for 45 minutes, and crushed while cooling to obtain a composition for injection molding.

Table 2 (Unit weight %) Comparative Example 1 A test piece was prepared in the same manner as in Example 1 using polymethyl methacrylate (PMMA) with a heat distortion temperature of 79°C and polypropylene (PP) with a heat distortion temperature of 110°C as the organic binder. , Degreasing was performed, and deformation during degreasing was evaluated. As shown in Table 1, the results showed large deformation even when the spacing between the support rods was 1 cm.

Volume ratio of FEII-4 in the water composition: 56%Next, using an injection molding machine, the heating cylinder temperature was 150°C to 170°C, the mold temperature was 50°C, and the injection pressure was 1500 kg/am. The above composition was molded into a test piece having the same shape as shown in Figure 1. When the resulting molded products were observed, they all had a good appearance.

The above-mentioned molded body was set in a light-air furnace in the same manner as in Example 1, and the temperature was raised to 350°C at a rate of 20°C/h+ and held at that temperature for 2 hours to perform degreasing. The binder component removal rate (degreasing rate) of the obtained degreased body was approximately 9
It was 8%. As shown in Table 3, the degreased body was not deformed at all, and no abnormalities such as cracks or blisters were observed. Furthermore, degreasing was carried out by increasing the temperature increase rate to 30'C/hr, but no abnormality was observed in the molded product, as described above.

Example 3 Metal powder was mixed into stainless steel (SUS30) with an average particle size of lOμm.
4) A composition was prepared in the same manner as in Example 2 except that it was powdered,
Injection molding and degreasing were performed. All of the molded bodies had a good appearance, and the degreasing rate was about 98%, and a degreased body without deformation was obtained. The composition ratios are shown in Table 4, and the degreasing results are shown in Table 5.

Comparative Example 2 An injection molding composition was prepared in the same manner as in Example 2, except that the polypropylene and paraffin wax (PW: melting point sg°C) used in Comparative Example 1 were used as organic binders, and the kneading temperature was 150°C. Created. The composition ratios are shown in Table 2.

Subsequently, heating cylinder temperature 1.50'C1 mold temperature 50'C
1 Injection molding was performed at an injection pressure of 1000 Kg/am" to create the same test piece as in Example 2. When the molded product was observed, all appearance was good. Next, degreasing was performed under the same conditions as in Example 2. , the degreasing rate and the deformation m of the degreased body were evaluated.

The degreasing rate was about 85%, and as shown in Table 3, some deformation was observed even when the spacing between the support rods was as narrow as lea, and large deformation occurred when the spacing was 2c111 or more.

Comparative Example 3 A composition was prepared in the same manner as in Comparative Example 2, except that the metal powder was 5IJS304 powder with an average particle size of 10 μm, and injection molding and degreasing were performed. Table 4 shows the composition ratio, and Table 5 shows the degreasing results. Although the appearance of the molded product was good, the degreased product was significantly deformed even when the spacing between the support rods was narrowed to 1 cm, and no good product was obtained. Moreover, the degreasing rate was about 85%.

Example 4 A degreased body was obtained in the same manner as in Examples 2 and 3, except that in Example 3, the molded body was placed on an IO mesh stainless steel wire gauze and hot air was also applied to the lower surface of the molded body. . The appearance of the degreased body was good, and the degreasing rate was 98%.

Example 5 The degreased body obtained in Example 3 was sintered at 1250"CX for 2 hours in a vacuum of 1O-3 torr or more to achieve a relative density of 95%.
A sintered body was obtained. Further, in Example 3, when stainless steel powder having an average particle size of 4.11 tm was used, a sintered body with a relative density of 98% was obtained under the same sintering conditions.

As can be seen from the above Examples and Comparative Examples, when the organic binder consists only of components with a low heat distortion temperature, such as polypropylene and wax, deformation due to its own weight occurs easily during degreasing. This was more noticeable in the case of powder.

On the other hand, according to the composition of the present invention, by using a component having a heat deformation temperature of +30"C or higher as a binder component, and further by using a component having a melting point of 30 to +00"C in combination, the distance between the support rods can be improved. Even if the molded product becomes larger (i.e., even if the molded product becomes larger), a good degreased body without deformation can be obtained even if a powder material that easily deforms during degreasing, such as stainless steel powder, is used. In addition, the above deformation can be prevented by using a mixed binder of a component such as polyacetal, which has a high thermal deformation temperature of 150°C or more and is resistant to thermal decomposition, and a low melting point component such as polyethylene glycol, which also is resistant to thermal decomposition. In addition to being more effective, it was possible to degrease at a relatively low temperature in a short time.
In the above examples, only the results obtained using metal powder were shown, but results were also obtained for a mixture of metal powder and ceramic powder, in which deformation of the degreased body was reduced compared to conventional compositions.

"Effects of the Invention" The composition and method for packaging a sintered body of the present invention have the following effects.

■ It prevents deformation due to its own weight during degreasing, so
This eliminates the need for embedding in powder and shape-retaining jigs that were required during degreasing, increasing productivity and accuracy of 52 products.

■ Products with complex shapes or large molded products that are difficult to embed in powder or retain their shape with a jig, or products that are easily deformed during degreasing such as molded products using stainless steel powder, can be easily deformed. A non-defatted body can be obtained.

■ Since there is no need to take out the degreased body from the powder, continuous production from degreasing to sintering is possible, increasing productivity.

(2) The temperature increase rate can be lowered by −L than that using conventional compositions, and therefore the degreasing time can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a test piece, FIG. 2 is an explanatory view showing a method for measuring deformation of a test piece, and FIG. 3 is an explanatory view of the amount of deformation.

Claims (1)

[Claims] 1. Metal powder or a mixed powder of metal powder and ceramic powder, and a thermoplastic component (component A) with a heat distortion temperature of 130°C or higher
A molding composition prepared by mixing an organic binder consisting of: 2. The composition according to claim 1, wherein component A is polyacetal. 3. The organic binder is a component with a melting point of 30 to 100°C (B
3. The composition according to claim 1, further comprising a component). 4. The composition according to claim 3, wherein component B accounts for 40 to 70% by weight of the organic binder. 5. The composition according to claim 3 or 4, wherein component A is polyacetal and component B is polyethylene glycol. 6. A molding composition according to any one of claims 1 to 5 is prepared by melting and kneading metal powder or a mixed powder of metal powder and ceramic powder and an organic binder, and shaping the composition into a desired shape. 1. A method for producing a sintered body, which comprises molding, then removing an organic binder from the molded body by heating, and sintering the obtained degreased body. 7. The manufacturing method according to claim 6, wherein the removal of the organic binder is carried out by placing the molded product on a shelf board that allows ventilation, and applying a flow of atmospheric gas to the lower surface of the molded product. 8. Using stainless steel powder as the metal powder, remove the organic binder in an oxidizing atmosphere, and sinter for 10^-^3t.
The manufacturing method according to claim 6 or 7, wherein the manufacturing method is carried out under a vacuum of orr or less.