JPS59229403A - Production of sintered metallic member and binder for injection molding - Google Patents

Abstract

PURPOSE:To produce a sintered metallic member having an intricate shape, etc. with good mass productivity by compounding an adequate amt. of a binder to metallic powder having an adequate grain size distribution and subjecting the powder to injection molding, heating and binder-removing under specific conditions then sintering the molding. CONSTITUTION:A compounded mixture contg. 6-15wt% binder and consisting of the balance raw material powder consisting essentially of metallic powder having 10-50mum average grain size is injection-molded under the conditions of 150-1,000kg/cm<2> injection pressure and 120-160 deg.C molding temp. then the injection-molding is heated and is removed of the binder under the conditions of 15- 250 deg.C heating rate, 450-600 deg.C heating temp. and 0-5hr time for maintaining heating in a reducing atmosphere and in succession the molding is sintered under ordinary conditions, by which a sintered metallic member is obtd. A binder consisting of 30-50wt% ethylene/vinyl acetate copolymer or low-density PE, 19- 32% methacrylate copolymer, 7-13% one kind of dibutyl phthalate, diethyl phthalate and stearic acid, the balance paraffin wax is suitable as the above- mentioned binder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a sintered metal member using injection molding, and an injection molding binder suitable for use in carrying out this method.

Generally, metal sintered members are manufactured by a powder metallurgy method, which involves press-forming a raw material powder mainly consisting of metal powder into a green compact, and then sintering the compact.

On the other hand, ceramic products such as refractories are manufactured by injection molding a mixture of 15 to 30 weight percent binder and the remainder consisting of raw material powder, heating to remove the binder, and firing. A method using injection molding has been proposed, and has attracted attention in recent years because it is possible to mass-produce products with shapes that cannot be molded using normal stamping or with thin walls. It is now possible to collect.

Therefore, attempts were made to apply the injection molding method used to manufacture the ceramic products mentioned above to the manufacture of metal sintered parts, which are currently manufactured using powder metallurgy. In this case, the raw material powder has a fine average particle size of 10 μm or less, whereas the metal sintered member has a relatively coarse particle size.

■ 3- Binder for injection molding used in the manufacture of ceramic products must be one that emphasizes the moldability of the raw material powder and the ease of thermal decomposition.

For these reasons, even if you try to manufacture sintered metal parts under substantially the same conditions as when manufacturing ceramic products by just changing the raw material powder, you will not be able to manufacture strong injection molded products. In addition, the heated molded product after the binder has been removed is easily broken and difficult to handle, making it impossible to perform the next step of sintering satisfactorily.

Therefore, from the above-mentioned viewpoint, the present inventors conducted research in order to use injection molding to manufacture metal sintered members with good mass productivity on an industrial scale. % (all % indicates weight %), ethylene vinyl acetate copolymer (hereinafter abbreviated as EVA)
and low density polyethylene (hereinafter abbreviated as LDPE)
One or two of the following: 30-50%, methacrylic acid ester copolymer = 19-32%, di-butyl phthalate (hereinafter abbreviated as DBP), di-ethyl phthalate (hereinafter referred to as DFiP) (abbreviated as) % and one type of stearic acid near to 13 parts, paraffin wax: remainder (but contains more than 20 parts)
, Use all products with a composition consisting of.

5 to 15 times of this binder is blended into a raw material powder mainly consisting of metal powder having an average particle size of 10 to 50 μmf to form a mixture.
~1000Kg/7°Molding temperature: 120~160℃, injection molded under the following conditions, Then, this injection molded body is heated and held in a reducing atmosphere at a heating rate of 15~B Heating temperature: 450~600℃ When the binder is removed by heating under the conditions of 20 to 5 hours, in the above injection molding process, a strong injection molded article is formed by the binder having the above composition and its blending amount. In the above-mentioned first step of debinding, a slight welding phenomenon occurs in the mutual contact areas of the metal powder, which is the raw material powder. Therefore, it is not necessary to pay special attention to handling, and the first step of sintering is satisfactory. I gained the knowledge that I could do it.

This invention was made based on the above knowledge, and the reason why the composition and manufacturing conditions of the TFk binder were limited to the above-mentioned conditions will be explained below.

A. Composition of binder (a) EVA and LDPE These components are thermoplastic resins that increase the strength of the injection molded product without impairing the moldability of the slurry.
During binder removal treatment, it has the effect of maintaining the shape of the injection molded product while other components are thermally decomposed at low temperatures and removed, but if the blending amount is less than 30 parts, the desired effect is not obtained. On the other hand, if the amount exceeds 50, the moldability of the blended mixture deteriorates, foaming phenomenon occurs during binder removal, and furthermore, it may remain in the sintered material. , since it deteriorates its properties, its blending amount was determined to be 30-50%.

(b) Methacrylic acid ester copolymer This component also contains
Like EVA and LDPE, it is a highly adhesive thermoplastic resin, and in addition to having the same effects as EVA and LDPE, it also prevents chipping and breakage of thin parts especially during injection molding, and is also resistant to thermal decomposition. The temperature is Fj V A
+Low compared to LDP Fi (EVA: 400°C or higher, LDP: 350°C or higher, whereas the thermal decomposition temperature of methacrylic acid ester copolymer is 200°C or higher)
Therefore, in coexistence with these components, the thermal decomposition temperature range of the binder expands, and as a result, when the binder is removed, the thermal decomposition of the binder progresses gradually, which may cause rapid thermal decomposition of the binder. However, if the amount is less than 19%, the desired effect will not be obtained, while if it is more than 32%, the moldability of the slurry will be reduced. Since this causes deterioration, the blending amount was determined to be between 19 and 32.

(C) DBP, DEP, and stearic acid These components have the effect of improving the compatibility of each component constituting the binder and homogenizing the binder, as well as improving the fluidity of the blended mixture during injection molding. However, if the amount is less than 7 parts, the desired effect cannot be obtained, while if it is added in excess of 13 parts, the injection molded product will not only become brittle, but also the hot molded product will be deformed. Since this phenomenon occurs, the amount to be added was determined to be 7 to 13 qb.

(d) Paraffin wax This component has the effect of improving the fluidity of the blended mixture during injection molding, as well as improving the wettability of the raw material powder and the binder to homogenize the blended mixture. In order to ensure this, it is necessary to mix 20 parts or more.

B. Manufacturing conditions (a) Amount of binder blended If the blended amount is less than 6%, the fluidity of the blended mixture during injection molding will be insufficient, not only will injection molding be difficult, but also injection molding with the desired strength will not be possible. On the other hand, if the amount exceeds 15, the amount of binder will be too large, and the heated molded product after removing the binder will tend to become brittle and difficult to handle. (b) Average particle size of metal powder When the average particle size becomes smaller than 10 μm, the specific surface area of the powder increases relatively, making it suitable for the desired injection molding even if 15% of binder is blended. In addition, the strength of the injection molded product decreased.On the other hand, even if the particle size was coarser than 50 μmf, the strength of the injection molded product and the heated molded product after removing the binder significantly decreased. Therefore, the average particle size was determined to be 10=50 μm.

(C) Injection molding conditions Injection pressure is 150Kg/m, molding temperature is 120℃
If it is less than that, a satisfactory injection molded product cannot be formed.
On the other hand, in terms of injection pressure, it is possible to mold any complex shape with an injection pressure of 1000 Kj1/m; however, when the molding temperature exceeds 160°C, the blended mixture The injection pressure was lowered to 150 to 100 ml because the gas generation became significant and defects such as a decrease in the density of the molded product and poor appearance occurred.
00Kg/c1fl, and the molding temperature was set at 120-160°C.

(d) Temperature rising rate for binder removal conditions If the temperature rising rate exceeds 250°C/hr'f (250°C/hr'f), foaming holes and cracks will occur, making it difficult to obtain a satisfactory hot molded product; Since a temperature increase rate of less than °C/hr is too slow to be practical, the temperature increase rate was reduced to 15-b.

■ Heating temperature and heating holding time If the heating temperature is less than 450°C, the binder cannot be completely removed, which will lead to an increase in the carbon content in the sintered material and cause problems in the properties and dimensions of the sintered material. On the other hand, if the heating temperature exceeds 600°C, deformation may occur [10-] Also, regarding the heating holding time, thin-walled products will not completely decompose during the heating process. Since it is binderized, there is no need to hold it at the heating temperature, and on the other hand, the binder can be completely removed in 5 hours no matter how thick the wall is. It was set as 0 to 5 hours.

Note that when carrying out the method of the present invention, the debinding treatment is preferably performed by burying the injection molded body in powder of alumina, silica, or even zirconia, which does not react with the molded body, thereby removing the binder from the molded body. Not only the shape retention effect is obtained, but also the binder discharge effect by capillary action is promoted, and the processing time can be shortened.

Next, the present invention will be specifically explained using examples.

Examples of raw material powders include carbonyl iron powder with an average particle size of 12 μm, atomized iron powder with an average particle size of 32 μm, reduced iron powder with an average particle size of 40 μm, and carbonyl Ni powder with an average particle size of 18 μm.

40 pm Fe-Ni alloy (containing 50% N1) powder.

32pm JIS-SUS304 stainless steel powder (hereinafter referred to as 5US304 powder), 32μ
m JIS-8US316 stainless steel powder (hereinafter 5
US316 powder) and 8 μm carbon powder were prepared, and these raw material powders were blended into the composition shown in Table 1, and this raw material powder had the composition shown in Table 1. , Add the binder according to the present invention in the amount shown in Table 1, mix for 1 hour at 135°C using a pressure kneader to form a homogeneous slurry, cool and crush to obtain an average particle size. : 2 cm of the present invention blends 1 to 7 were prepared, respectively.

Next, using all of the above-mentioned blended mixtures 1 to 7 of the present invention, and under the injection molding conditions shown in Table 2, the molding was performed to a height of 50 mm, a maximum thickness of 25 mm, and a minimum thickness of 25 mm, as shown in the longitudinal cross-sectional view in FIG. Wall thickness: 3mm, maximum diameter: 45ynm.

A cylindrical injection molded body with an uneven thickness having a minimum diameter of 24 cm was molded, and the injection molded body was immersed in alumina powder under the conditions shown in Table 2 in a hydrogen atmosphere. Methods 1 to 7 of the present invention were carried out by carrying out binder removal treatment and further sintering the molded bodies after binder removal under the same conditions shown in Table 2.

As a result, metal sintered members having the theoretical density ratios shown in Table 2 and having the shape shown in FIG. 1 without any defects were obtained.

In addition, in the above example, the production of a metal sintered member with a complex shape in which thin and thick parts coexist was described, so the injection molding pressure was relatively high and the temperature increase rate during the binder removal process was comparatively high. Although this was carried out under relatively slow conditions, when producing metal sintered parts with simple shapes such as plates, rods, or tubes, it is necessary to form injection molded bodies at low injection pressure and at a high temperature increase rate. This makes it possible to remove the binder.

As described above, according to the present invention, it is possible to mass-produce metal sintered members not only in thin-walled shapes and uneven-walled shapes but also in extremely complicated shapes.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an example of an injection molded article. Applicant Mitsubishi Metals Co., Ltd. Agent Tomi 1) Kazuo Kazuo and 1 other person July 4, 1980 Commissioner of the Japan Patent Office Kazuo Wakasugi 1゜ Indication of the case Patent application No. 102310/1982 2 Name of the invention Metal sintering Manufacturing method for binding parts and binder for injection molding 3, Person making the amendments Representative: Ken Nagano 4, Agent Address: 8th Floor, Soyasu Daini Building, Kanda Nishiki-cho, Chiyo 11-ku, Tokyo - 8th floor, Soho Daini Building 6, Amendment: Detailed explanation of the invention column 7 of the subject specification, contents of the amendment As attached (1) Description, page 14, Detailed explanation of the invention section,
In Table 2, the value of the theoretical density ratio (%) of the sintered member according to method 5 of the present invention is "83", which has been corrected to "93". Above 1-

Claims (2)

[Claims] (1) Using a mixture consisting of raw material powder containing binder = 6 to 15% by weight and the remainder being a metal powder having an average particle size of 10 to 50 μmf, injection pressure = 15
0-1000 shame/d. Molding temperature = 120 to 60°C, injection molded under the following conditions, and then the injection molded product was heated and held in a reducing atmosphere at a heating rate of 15 to 250°C/hr-%, heating temperature: 450 to 600°C Time: 0-5 hours. 1. A method for producing a metal sintered member, which comprises heating under the following conditions to completely remove the binder, and then sintering the molded body after the binder has been removed under normal conditions. (2) One or two of ethylene-vinyl acetate copolymer and low-density polyethylene: 30-50 in weight%
41 Methacrylic acid ester copolymer = 19 to 32%, dibutyl phthalate, diethyl phthalate, and one type of stearic acid, near to 13%, paraffin wax: remainder (contains 20% or more)
An injection molding binder characterized by having a compounding composition consisting of.