JPH02194104A - Binder for forming and sintering metal powder and manufacture of sintered body using this binder - Google Patents

Abstract

PURPOSE:To improve closeness with injection molding by using organic binder containing acrylic series resin as essential component in the binder at the time of forming metal powder of Mo, W, Ti, etc. CONSTITUTION:The acrylic resin as the essential component in the binder functions as main bonding agent for the metal powder and secures fluidity at the time of injection-molding of the metal powder and also has good gas diffusibility at the time of debinding treatment and the closeness is not obstructed at the time of sintering. Therefore, the conformable fluidity with the metal powder is improved and the debinder can be executed at relatively simple without causing to remain much residual carbon. Further, the injection- molding and sintering can be substantially executed to the metal of Mo, W, Ti, etc., and the sintered body having high density and complicate shape is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a binder for producing a molded sintered body of metal powder, kneads the binder and metal powder, and then injection molds the mixture.
This invention relates to a metal powder injection molding sintering method for obtaining a product by removing the binder and then sintering.

[Conventional technology]

This injection molding sintering method uses high melting point metal powder obtained by hydrogen reduction of atomized powder, carbonyl iron and nickel powder, and oxide powder to produce biomaterial parts such as artificial joints,
It is widely known that this method is suitable for producing highly densified sintered bodies such as aircraft parts such as turbine blades, valves, and typewriter ink heads.

The presentation on "Factors governing sintering densification during injection molding of metal powder" at the 1986 Spring Conference of the Powder Metallurgy Association disclosed the factors for sintering densification during injection molding and sintering. ing.

[Problem to be solved by the invention]

However, when applying injection molding to a metal with a relatively high melting point such as Tl5M01W, it is difficult to make the starting metal powder spheroidal due to its high melting point, which makes it difficult to mold, easily loses its shape when removing the binder, and carbon in the binder. Due to reasons such as the tendency for the powder to react with oxygen, etc. and form carbides and oxides,
The reality is that there are difficulties in its application, and the sufficient densification effect of injection molding cannot be obtained.

The problem to be solved by the present invention is to solve the above-mentioned problems in applying such high-melting point metal powder to injection molding and to find conditions for deriving the densification effect by injection molding of high-melting point metal powder.

[Means to solve the problem]

In the present invention, when molding metal powders such as Mo, W, and Ti,
The above problem was solved by using an organic binder whose main component is an acrylic resin.

[Effect]

The acrylic resin, which is the main component of the binder, functions as the main binder for the metal powder, ensuring fluidity during injection molding of the metal powder, good dispersion during binder removal processing, and denseness during sintering. It does not interfere with

This acrylic resin is blended with paraffin wax to improve the mold releasability from the mold for maintaining the shape of the molded product, and when such wax is blended, it is used to bond the waxes and the acrylic resin. of active polypropylene (APP). As a result, a uniformly densified molded body can be obtained without inhibiting binder removal properties and without separating from the metal powder during injection molding.

In addition, the amount of this binder blended into the metal powder and the conditions for removing the binder vary depending on the type of metal powder used and the composition of the blended binder, but from the viewpoint of moldability and removal of the binder, generally 100% of the metal powder is 5～
20 parts by weight is preferred.

Further, the above metal powder contains Group IA (Li) of the periodic table of elements.
, Na, K, Rb, Cs), IIA group (Mg, Ca,
Sr, Ba), IIIA group (Sc, Y, lanthanoids, actinides), IVA group (Ti, Zr.

Hf), VA group (V, Nb, Ta), Cr, Ni.

By containing one or more hydrides selected from the elements Cu and Pb as active ingredients,
Hydrogen generated from the metal hydride during binder removal or sintering further progresses decomposition of chain-bonded polymers, promoting binder removal.

Among these, particularly preferred is I[[A group (Sc.

Y, lanthanoids, actinides), IV/! Family (T
i.

It is a metal hydride of one or more of the following: Zr, Hf), VA group (V, Nb, Ta), and Ni.

In order to remove the binder that makes up the intermediate product taken out of the mold, the binder is removed by heating. Debinding is carried out in an oxidizing atmosphere, for example in air, at a temperature of 200 to
This is done by heating to 300°C.

Since the binder used in the present invention is mainly composed of an acrylic resin that easily becomes a monomer when heated, removal of the binder is effectively promoted. At the stage where binder removal is completed, the external shape remains unchanged, but the porosity is 20 to 30%.

Furthermore, K, and when debinding is performed in an oxygen atmosphere, K,
It is preferable that the heating during the sintering is performed using a thermal cycle.

It is even more preferable to perform the step of kneading the metal powder and binder in an inert gas atmosphere.

After this, sintering is performed in vacuum or in an inert gas atmosphere. Some metal hydrides generate hydrogen during the sintering process, and in that case, the generated hydrogen accelerates the decomposition of the remaining binder.

In this case, heating using a thermal cycle method in which the temperature is raised or lowered within a certain range has many advantages, such as increasing the sintering density, increasing mechanical strength, and lowering the sintering temperature. This sintering process causes the intermediate product to shrink in volume, resulting in a net passive product that is substantially in the shape of the final product.

By blending metal hydride into metal powder, the compound is decomposed at the debinding temperature and hydrogen is generated.
This hydrogen reacts with the organic binder, further promoting the decomposition of the organic binder by heating.

As a post-molding treatment, finishing processing may be applied to products that require even higher dimensional accuracy, and surface treatment such as coloring may also be performed depending on the intended use of the product.

〔Example〕

Example 1 M with an average particle diameter of 4.1 μm and a tap density of 27%.

100 parts by weight of powder K, special acrylic resin manufactured by Dai-Kogyo (
G7036): Binder 7.7 manufactured by Eastman Kodak Co. containing PP:wax in a ratio of 2:1:1
Parts by weight were mixed and hot kneaded using a lab blast mill. Fluidity was evaluated using a capillary flow tester. Figure 1 shows the relationship between shear rate and viscosity. From the same figure, a linear relationship was observed between the logarithms of both, indicating that the product had good moldability.

This mixture exhibited stable mixing and flow properties.

This was done at a nozzle temperature of 140℃ and an injection pressure of 660kg/
6X6X80 (carp) injection molded under cat conditions
A sample piece having the size of was obtained. Its flow characteristics were those of Bingham flow, and there were no problems with injection molding.

Also, for comparison, K, PP (polypropylene)-APP
- When a binder made of wax was used, kneading and injection molding were possible without any problems, but deformation and blistering occurred in the molded product when the binder was removed, making it unsuitable for injection molding.

Further, injection molded articles obtained using the above binder were subjected to three types of binder removal treatments shown in Table 1, A to C. The status after each treatment is shown in the right column of the same table.

Further, the molded body from which the binder had been removed under the conditions of A above was sintered at 1700° C. for 19 hours in a hydrogen stream.

This resulted in a sintered body with a relative density of 93-93.5%, c, o, 1 degree of 46 and 22499 m, respectively. The compression characteristics of the sintered body are shown in Figure 2.
It was found that there was no destruction up to a deformation amount of 70%, and that the material had properties equivalent to those of die press sintered MO.

Table 1 Example 2 The second example shows an example in which the present invention is applied to Ti. In the case of Ti, it is particularly desirable to contain 8% by weight or less of Fe powder in view of its sinterability. .

95 parts by weight of Ti powder with an average particle size of 30 μm and an average particle size of 5
5 parts by weight of carbonyl Fe powder of μm were mixed using a mixer, and the proportion of acrylic: APP: wax: DBP was 8.0 by weight with respect to 100 parts by weight of this mixed powder.
: 4.0 : 4.0 : 1.5 and 17.5 parts by weight of the binder contained were mixed, hot kneaded using a lab blast mill, and injection molded under the same conditions as Example 1. . This kneaded material had no problem with injection molding, and a uniform molded product was obtained.

-Binder removal is done by heating to approximately 200℃ in the atmosphere to 20%
The organic matter was removed, and the remaining binder was decomposed and removed by increasing the temperature to 400° C. in a vacuum, and preliminary sintering was performed to make it strong enough to handle.

Then it+-' torr (7) 13 under vacuum
It was sintered at 00°C.

Sintering is promoted by adding and blending Fe powder,
A sintered body with a relative density of 97% or more could be obtained. Furthermore, it was found that the bending strength of the sintered body was approximately doubled by applying the above two-stage binder removal process. Furthermore, both compressive strength and strength deformation were significantly improved by applying two-stage binder removal.

In addition, fine particles of TiC were observed in the conventional Ti sintered body, but by performing the two-stage treatment, it became possible to remove the binder completely, and no carbon remained and the sintered body of the present invention The presence of TiC was not recognized.

Example 3 As raw materials, titanium hydride was blended at a ratio of 60% by volume and organic binder was blended at a ratio of 40% by volume.

The particle size of the titanium hydride at this time was about 30 μm. On the other hand, the binder used had the following composition as part of the above 40% by volume.

Unit: Volume % ・Special acrylic resin manufactured by Dai-Kogyo (G7036) 2
0. Eastman Kodak APP resin 10
- Wax 10 Kneading was carried out using a plastomill and heated at a temperature of 100 to 150° C. while rotating at a rotational speed of 50 revolutions per minute. This kneaded material was granulated into pellets using a granulator, and then injection molded to produce particles.

This green is heated to 300°C in a hot air circulation heating furnace at 10°C per hour.
It was heated at a temperature increase rate of 0.degree. C., and cooled after reaching the temperature.

At this stage, about 85% of the binder had disappeared.

After the binder was removed, the product was heated and sintered at 1000° C. in a vacuum.

As a result of this sintering, almost all of the binder disappeared, and a good sintered body with K and a filling degree of 95 to .98% was obtained.

Example 4 An experiment similar to Experimental Example 1 was conducted, except that a binder having the following composition was used as a binder in the raw materials.

Unit: Volume % Acrylic resin (CB-1) manufactured by Sanyo Chemical Co., Ltd. 20
・Polystyrene 10・Wax 10 As with Experimental Example 1, a good sintered body was obtained from the sintered body thus prepared.

Example 5 An experiment similar to Example 3 was conducted, except that an organic binder having the following composition was used as the organic binder in the raw materials.

Unit: Volume % ・Special acrylic resin manufactured by Dai-Kogyo (G7036) 2
0・Toso BVA resin (mouth IE633)
10 (Ethylene Vinyl Acetate Resin) - Wax 10 As with Example 3, a good sintered body was obtained with respect to the sintered body thus prepared.

Example 6 Sintering was carried out at 800°C, with 10 to 20 holes above and below the center.
A so-called thermal cycle method was used in which heating and cooling were repeated to a temperature range of 0°C. In the thermal cycle, the temperature was raised and lowered 5 to 6 times while maintaining the final temperature for 5 to 10 minutes.

Other conditions are the same as in Example 3.

In this case, despite the low sintering temperature, Experimental Example 1
A higher degree of filling (98-99%) was obtained than in the case of , and the mechanical properties were excellent.

〔Effect of the invention〕

The present invention provides the following effects.

(1) Compatibility with metal powder improves fluidity, and binder removal can be performed relatively easily without leaving a large amount of residual carbon.

(2) Injection molding and sintering of metals such as Mo SW and Ti is substantially possible, and a sintered body with a high density and a complicated shape can be obtained.

(3) The sintered body obtained by the present invention has high density and particularly excellent compressive strength.

[Brief explanation of the drawing]

The attached figure shows an example of applying the present invention to Mo powder,
FIG. 1 shows the formability of the kneaded product, and FIG. 2 shows the compression characteristics of the sintered body. Patent applicant: Nippon Tungsten Co., Ltd. Representative: Masu Kobori 3 Ichishi R. Σ

Claims (1)

[Claims] 1. A binder for metal powder molding and sintering comprising an organic binder containing an acrylic resin as a main component. 2. The binder for metal powder molding and sintering according to claim 1, wherein the organic binder containing an acrylic resin as a main component contains waxes and an agent for preventing separation between the acrylic resin and the waxes. 3. In the metal powder injection molding sintering method in which a product is obtained by kneading metal powder and a binder, injection molding, removing the binder, and then sintering, the binder is mainly acrylic resin. A metal powder injection molding sintering method using an organic binder as a component. 4. The metal powder injection molding sintering method according to claim 3, wherein the binder removal is performed in an oxygen atmosphere, and the heating during the sintering is performed in a thermal cycle. 5. In the description of claim 3, the metal powder is Mo powder, and after injection molding a mixture of 100 parts by weight of Mo powder and 5 to 10 parts by weight of a binder mainly composed of acrylic resin, the mixture is molded in air. After heating and debinding,
A metal powder injection molding sintering method characterized by sintering in a hydrogen stream. 6. In claim 3, the metal powder is a single Ti powder or a mixed powder of Ti powder and 8% by weight or less of Fe powder, and 100 parts by weight of the mixed powder contains 15% by weight of a binder mainly composed of acrylic resin. After injection molding a kneaded product containing ~20 parts by weight, it was heated in the atmosphere to partially remove the binder, and then heated to about 500°C in a vacuum.
A metal powder injection molding sintering method characterized by sintering in a vacuum. 7. In the statement of claim 3, the metal powder is a member of the periodic table of elements.
IA group (Li, Na, K, Rb, Cs), IIA group (M
g, Ca, Sr, Ba), IIIA group (Sc, Y, lanthanoid, actinide), IVA group (Ti, Zr, Hf)
, VA group (V, Nb, Ta), Cr, Ni, Cu, Pb
A metal powder injection molding sintering method in which one or more hydrides selected from the following elements are contained as an active ingredient.