JPH021205B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention (1) Industrial Application Field The present invention relates to a raw material sheet for a metal sintered body used in obtaining a metal sintered body, and a method for manufacturing the same.

(2) Prior art The present applicant first laminated a raw material sheet for a metal sintered body obtained by kneading a synthetic resin binder into sinterable metal powder on the surface of a metal base material, and the laminated raw material We have proposed a technique in which a sheet is formed into a predetermined shape, and then the formed body is subjected to a sintering process to obtain a sintered body, and at the same time, the sintered body is welded to a base material.

(3) Problems to be Solved by the Invention As a result of various studies on the above technology, we found that depending on the material of the synthetic resin binder, the lamination properties of the raw material sheets may deteriorate, causing delamination in the molded product, or It was discovered that there was a problem with cracks occurring.

An object of the present invention is to provide the raw material sheet and its manufacturing method that can eliminate the above problems.

B. Structure of the invention (1) Means for solving the problems The raw material sheet for metal sintered bodies according to the present invention has 90 to
The sheet is composed of 99% by weight of sinterable metal powder and 1 to 10% by weight of a synthetic resin binder. % by weight of a thermoplastic synthetic resin with excellent lamination properties, the thermoplastic synthetic resin with excellent crack resistance is at least one selected from tetrafluoroethylene resin, polystyrene resin, and nylon; The thermoplastic synthetic resin having excellent properties is characterized by being at least one selected from acrylic resin, polyethylene resin, and butadiene-vinyl acetate copolymer.

In addition, the method for producing a raw material sheet for metal sintered bodies according to the present invention includes at least one thermoplastic synthetic resin with excellent crack resistance selected from tetrafluoroethylene resin, polystyrene resin, and nylon, and an acrylic resin. , at least one thermoplastic synthetic resin with excellent lamination properties selected from polyethylene resin and butadiene vinyl acetate copolymer.
A step of preparing a liquid synthetic resin binder containing 30 to 70% by weight, and a step of kneading 90 to 99% by weight of sinterable metal powder and 1 to 10% by weight of the liquid synthetic resin binder to obtain a plastic material. The method is characterized by sequentially performing the following steps: heating and drying the plastic material; and molding the plastic material into a sheet in a thermoplastic state.

(2) Effect When a synthetic resin binder containing the thermoplastic synthetic resin with excellent crack resistance and the thermoplastic synthetic resin with excellent lamination properties is used,
The molded product obtained from the raw material sheet does not cause delamination or cracking, has high interlayer adhesion strength, and has a good surface texture, resulting in improved dimensional accuracy and surface texture. An excellent metal sintered body can be obtained.

However, the amount of synthetic resin binder added is 1% by weight.
If it is less than 10% by weight, it will not be possible to form a sheet, while if it is more than 10% by weight, the porosity of the sintered body will be high, making it impossible to obtain a high-strength sintered body.

Furthermore, if the blending amount of thermoplastic synthetic resin with excellent lamination properties is less than 30% by weight, delamination will occur between the laminated raw material sheets, while if it exceeds 70% by weight, cracks will occur on the surface of the laminated raw material sheets during molding. occurs.

In producing the raw material sheet, a sinterable metal powder and a liquid synthetic resin binder having the specific material are kneaded to obtain a plastic material, and then the plastic material is heated and dried to form a small amount of synthetic resin binder. can be uniformly applied to sinterable metal powder. Uniformly applying the synthetic resin binder to the sinterable metal powder in this way is necessary to obtain a sheet with good shape retention in the sheet forming process in the next process, and it is also necessary to use a small amount of the synthetic resin binder. is necessary to obtain a high-strength sintered body with low porosity.

By subsequently molding the plastic material into a sheet in a thermoplastic state, it is possible to facilitate the molding process and to obtain a raw material sheet that has appropriate flexibility and tear strength at room temperature and is easy to handle. can.

(3) Examples Sinterable metal powders used in the present invention include self-fusing alloy powders such as Ni-based, Co-based, Fe-based, etc.
Conventionally known materials such as Fe powder and Cu powder are applicable.
In addition, when using self-fusing alloy powder, if the sintering temperature is set to a temperature exceeding the liquidus line of the alloy to improve the strength of the sintered body, high-melting point metal powder may be added to the self-fusing alloy powder. The high melting point metal prevents the flow of the self-fusing alloy and improves shape retention.This type of high melting point metal powder includes Mo,
Any one of powders such as W, stainless steel, WC, Fe-Mo (ferromolybdenum), or a mixture thereof is used.

Thermoplastic synthetic resins with excellent crack resistance include tetrafluoroethylene resin, polystyrene resin,
At least one selected from nylon is suitable, and at least one selected from acrylic resin, polyethylene resin, and butadiene-vinyl acetate copolymer is suitable as a thermoplastic synthetic resin with excellent lamination properties.

First, the production of the raw material sheet will be explained.

10~60μ Ni self-fusing alloy powder 80% by weight and 10~60μ Ni self-fusing alloy powder 80% by weight
A mixed powder is obtained by mixing 20% by weight of 53μ Mo pulverized powder in a V-blender for 30 minutes.

A liquid synthetic resin binder is obtained by mixing a tetrafluoroethylene resin emulsion and an acrylic resin emulsion at a ratio of 1:1.

Synthetic resin binder 3% by weight based on the above mixed powder
is added and kneaded for 5 minutes using a table kneader at room temperature to obtain a plastic material. In this case, the synthetic resin binder is an emulsion type, so it has good dispersibility.
It can be uniformly dispersed in a small amount of synthetic resin binder mixed powder with a short kneading operation.

Plastic materials are heated using drying ovens, heaters, etc.
The plastic material is dried by heating to 80 to 120°C to evaporate the moisture in the synthetic resin binder. The obtained plastic material has a shape of numerous nodules as it is bound by the synthetic resin binder, and the mixed powder is uniformly coated with the synthetic resin binder.

After drying, the plastic material, which is in a thermoplastic state by retaining heat of approximately 80°C, is passed through a roll machine equipped with rolls with a diameter of 245 mm and a length of 215 mm several times in the X and Y directions.
Three types of raw material sheets with thicknesses of 1 mm, 1.5 mm, and 3 mm are formed. The molding pressure was 0.5 kg/mm ² in terms of the density of the pressure molded test piece. In this case, heating the roll of the roll machine to a temperature similar to that of the plastic material (approximately 80°C) can improve the workability of forming the raw material sheet.

After molding, the raw material sheet is heat-treated at 80°C for 30 minutes to remove distortion generated during molding.

The obtained raw material sheet has appropriate flexibility and tear strength at room temperature.

Next, a method for manufacturing a press mold using the raw material sheet will be described.

Figure 1 shows a press die 1, which is made up of a base material 2 cast from cast steel (JIS SC46 material) and a workpiece forming part 3 made of a metal sintered body S welded to the base material 2. configured.

As shown in FIG. 2a, the base surface 2a forming the workpiece forming part 3 of the base material 2 is 5 to 20 mm lower than the outer surface of the workpiece forming part 3 in the completed mold 1 (indicated by chain lines). Molded. The base material 2 is used as-cast, and the base surface 2a with black crust is sandblasted.
After cleaning, apply acrylic resin adhesive.

As shown in FIG. 2b, the base surface 2a has a thickness of 3.
3 mm raw material sheets St are stacked and pasted, the raw material sheet St is pressed by a synthetic resin female mold M attached to a press machine, etc., and the degree of contact of the female mold M against the raw material sheet is checked. The raw material sheet is scraped in some places, and new raw material sheets are added in areas where there are no hits.
Paste St. The shape of the laminated raw material sheet St is made to substantially match the shape of the female mold M by repeating this pressing of the female mold M and the scraping and pasting of the raw material sheet St. The laminated raw material sheet St that has undergone such a forming process has high interlayer adhesion strength, and has good surface properties without cracking. In this case, the pressing force of the female mold M is 0.2 to 0.3 kg/mm ² .

As shown in FIG. 2c, the base material 2 together with the laminated raw material sheet St is placed in a heating furnace 4 and heated to 80° C. to plasticize the laminated raw material sheet St.

As shown in Fig. 2d, a 3 mm thick raw material sheet St is further laminated and pasted on the plasticized laminated raw material sheet St, and the obtained laminated raw material sheet St is 0.7 kg by the female die M. The molding operation of the workpiece molding section 3 is completed by pressing with a pressing force of /mm ² .

In this case, in order to improve the mold releasability of the female mold M from the laminated raw material sheet St, talc powder is applied to the female mold M, or polyvinylidene chloride resin or polychloride resin is applied between the female mold M and the laminated raw material sheet St. An ultra-thin membrane made of vinyl resin, polyethylene resin, etc. is interposed.

After the molding operation is completed and the temperature of the base material 2 and the laminated raw material sheet St has been cooled to room temperature, the excess portion of the sheet St is removed.

As shown in Fig. 2e, a base material 2 made by laminating a 1 mm thick alumina sheet Sa on a laminated raw material sheet St is placed in a container 5, and a steel ball with a diameter of 0.75 mm is placed as a backup in the container 5. Pour in 6. This alumina sheet Sa is composed of alumina powder and the same synthetic resin binder as described above, and prevents the rough surface of the steel balls 6 from being transferred to the laminated raw material sheet St, thereby reducing the surface roughness of the sintered body S. It has the function of preventing Also, depending on its weight, the steel ball 6 may be made of Ni, which will be described later.
This suppresses the dimensional change, that is, the expansion, of the sintered body S during sintering of the self-fusing alloy-Mo powder.

Next, the base material 2 is placed in a vacuum sintering furnace 7, and the organic substances are decomposed and the Ni self-fusing alloy and Mo powder are sintered under the heating-cooling conditions shown in FIG. As the carrier gas, nitrogen gas or highly reducing hydrogen gas is used.

(A) First heating zone (Fig. 3A) This heating zone A is from room temperature to 650°C, and the temperature increase rate is 10 to 20°C/min. In this heating zone A, moisture first evaporates, and then the tetrafluoroethylene resin and acrylic resin in the synthetic resin binder in the raw material sheet St and the alumina sheet Sa are decomposed and gasified. These synthetic resins gasify at 300 to 400℃, but in consideration of heat conduction, most of the organic substances are removed by soaking at 600 to 650℃ for 90 minutes, leaving behind the Ni self-soluble alloy-Mo powder. do. The gasification of this organic substance is explained by the change in the degree of vacuum inside the vacuum sintering furnace 7. At room temperature, the degree of vacuum is 1 Torr, but when soaking is maintained at 650° C. for 90 minutes, the degree of vacuum decreases to a maximum of 2 Torr.
This is mainly due to the production of decomposition gases from organic substances. After 90 minutes, the vacuum level is restored again.
The temperature rises to 1 Torr, which is the vacuum sintering furnace 7.
This means that decomposition gas has been removed from the inside.

(B) Second heating zone (Fig. 3B) This heating zone B is in the range of 900 to 1000℃, and the Ni self-flux alloy-Mo powder is heated to the solidus line of the Ni self-flux alloy (1010 to 1020℃). Temperatures below, e.g.
A solid-phase sintering process is performed by soaking at 950°C for 30 minutes, and this is pre-sintered. The temperature increase rate from the first heating zone A is 10 to 20°C/min.

Since the Ni self-fusing alloy-Mo powder body in the vacuum sintering furnace 7 is heated from its surface and increases in temperature, a predetermined heating time is required until the entire powder body reaches a uniform temperature. If the sintering temperature is
If it is suddenly heated to 1000-1200℃, a temperature difference will be created between the surface part of the Ni self-fusing alloy-Mo powder body and the part in contact with the base surface 2a, which will increase the variation in porosity and make it impossible to obtain a uniform sintered body. Not only is this difficult to achieve, but also defects such as cracks are more likely to occur after sintering.

In the second heating zone B, undecomposed organic substances are completely gasified and removed. Due to this gasification, etc., the degree of vacuum in the vacuum sintering furnace 7 temporarily decreases to 4 Torr, but returns to 1 Torr after 30 minutes.

(C) Third heating zone (Figure 3C) This heating zone C ranges from just below the solidus line (1010~1020℃) of the Ni self-fluxing alloy to the liquidus line (1075~1020℃).
1085℃), i.e. in the range of 1000 to 1200℃.
Preferably, the sintered body S is formed by holding the temperature constant at 1160° C. for 120 minutes and performing liquid phase sintering treatment by melting the Ni self-fusing alloy. In this case, the flow of the Ni self-fusing alloy is hindered by the presence of Mo, and therefore shape retention is good. The temperature increase rate from the second heating zone B is 15 to 20°C/min.
Since the Mo pre-sintered body has already been heated to a high temperature in the second heating zone B, the time required to raise the temperature to the third heating zone C is short. If the holding time in the third heating zone C is insufficient, sintering will not be completed completely and defects will occur in the sintered body S.

The reason why the sintering temperature is selected as 1160℃ as mentioned above is that when the sintering temperature is about 1200℃, the dimensional change of the sintered body S becomes large, and it is not easy to control the furnace temperature. This is because there are problems when the temperature fluctuates, and 1160°C is the appropriate working temperature to eliminate these problems.

(D) Cooling zone (Fig. 3D) This cooling zone D is approximately below the sintering temperature.
Primary cooling zone D ₁ up to 800℃, secondary cooling zone D ₂ from approximately 800℃ to approximately 400℃, and approximately 400℃
It is divided into a tertiary cooling zone _D3 from ℃ to room temperature.

The primary cooling zone D ₁ is a stable region of the sintered body S under high temperatures, and in this cooling zone D ₁ , thermal stimulation is avoided as much as possible, and at the same time, cooling is performed at a maximum of about 2°C/min in consideration of cooling efficiency. Cool at the set rate. When rapid cooling is performed in this cooling zone _D1 , cracks occur frequently in the sintered body S.

In the secondary cooling zone D ₂ , the base material 2 is cooled at a slow rate of about 3° C./min at maximum in order to absorb linear expansion and dimensional changes due to Ar ₁ transformation. In this case, the linear shrinkage of the sintered body S is 14.6×
10 ^-6 /°C, but since it is porous, it follows the shrinkage of the base material 2. When rapid cooling is performed in this cooling zone _D2 , cracks occur frequently in the sintered body S.

In the tertiary cooling zone _D3 , the temperature of the sintered body S and the base material 2 is cooled to room temperature by gas cooling (including air cooling) other than liquid cooling such as water or oil.

Through the heating-cooling process described above, a mold 1 is obtained, as shown in FIG. 1, in which the workpiece forming portion 3 is formed of a sintered body S made of a Ni self-fluxing alloy-Mo.

The sintered body S has good weldability with the base material 2 and does not have defects such as cracks. In addition, we measured the shape at 50 mm intervals in the X and Y directions using a three-dimensional measuring machine and compared it with female mold M. When the dimensions of mold 1 were 300 mm in length, 250 mm in width, and 180 mm in height,
There are three locations that are expanded by a maximum of 5mm.
Other locations showed expansion of 0 to 0.3 mm, indicating excellent dimensional accuracy. Further, by using the alumina sheet Sa, the rough surface of the steel ball 6 is prevented from being transferred to the laminated raw material sheet St, so that the surface roughness of the sintered body S is good.

Therefore, the mold 1 obtained through the above steps can be used immediately for press work by performing simple finishing processing.

Next, a method for manufacturing a sliding member using the raw material sheet will be explained.

After degreasing the surface of a cold-rolled steel plate with a length and width of 100 mm and a thickness of 1.5 mm, two of the above raw material sheets with a thickness of 3 mm were laminated and attached to the steel plate using an acrylic resin adhesive. , the surface of the raw material sheet is finished smooth.

The obtained laminate is placed in a vacuum sintering furnace, and the organic substance is decomposed and the Ni self-fusing alloy powder and Mo powder are sintered under the same heating and cooling conditions as described above. Note that the sintering treatment time was 30 minutes.

A large number of through holes are bored in the laminate made of the steel plate and the sintered body obtained through the above steps to produce a light-load sliding member having the sintered body as a sliding surface.

The sliding member has a sintered body with good surface roughness and excellent sliding performance, and since the sintered body is reliably welded to the steel plate, delamination does not occur.
In order to improve the lubrication performance of the sintered body, the sintered body is impregnated and hardened with a lubricating synthetic resin such as tetrafluoroethylene resin, or WS ₂ , etc. is added to the raw material sheet.
It is recommended to mix a solid lubricant such as MoS ₂ .

In order to increase the thickness of the sintered body of the sliding member, the raw material sheet with a thickness of 3 mm is adhered to the sintered body using an acrylic resin adhesive, and after finishing the surface flat, the same method as above is repeated. A sintering process is performed to obtain a sliding member having a two-layered sintered body.

In this sliding member, the two sintered bodies are reliably welded together, and no delamination occurs during use.

For comparison, a liquid synthetic resin binder consisting only of tetrafluoroethylene resin emulsion was prepared, a raw material sheet was formed using the same method as above, and a press mold similar to that described above was manufactured using this raw material sheet. When the process was carried out, it was confirmed that delamination occurred in the laminated raw material sheet that had undergone the forming process.

For comparison, a liquid synthetic resin binder consisting only of acrylic resin emulsion was prepared, a raw material sheet was molded using the same method as above, and a press mold manufacturing process similar to that described above was carried out using this raw material sheet. When carried out, it was confirmed that cracks had occurred in the laminated raw material sheet that had gone through the forming process, and that the surface quality had deteriorated.

In the above examples, a synthetic resin binder containing tetrafluoroethylene resin and acrylic resin was described, but other thermoplastic synthetic resins with excellent crack resistance and other thermoplastic synthetic resins with excellent lamination properties may be used. Even when a synthetic resin is used in combination, the same effects as in the above embodiment can be obtained.

Note that the alumina sheet is manufactured through the steps described below.

8% by weight of a synthetic resin binder similar to that used in the production of the raw material sheet was added to 2-50μ alumina powder and kneaded for 5 minutes in a table kneader at room temperature, and during this kneading, 3% by weight of water was added. Added.

The obtained plastic material was heated to 120°C for 60°C using a heater.
Heating is performed for a minute to evaporate the moisture in the synthetic resin binder and dry the plastic material.

After drying, the plastic material, which is in a thermoplastic state by retaining heat of approximately 80 degrees Celsius, is subjected to a molding process using the same roll machine as that used for manufacturing the raw material sheet, using the same method as that used to produce the raw material sheet, to form a 1 mm thick plastic material. Form an alumina sheet. In this case, heating the rolls of the roll machine to a temperature similar to that of the plastic material (approximately 80°C) facilitates sheet forming.

After forming, the aluminate is heat-treated at 80°C for 30 minutes to remove distortion generated during forming.

C. Effects of the Invention According to the present invention, since the synthetic resin binder of the raw material sheet contains a thermoplastic synthetic resin with excellent crack resistance and a thermoplastic synthetic resin with excellent lamination properties, a molded article obtained from the raw material sheet is obtained. It is possible to obtain a molded body that does not cause delamination or cracking, has high interlayer adhesion strength, and has good surface quality, and in turn, produces a metal sintered body with excellent dimensional accuracy and surface quality. Obtainable.

According to the second invention, in producing the raw material sheet, a sinterable metal powder and a liquid synthetic resin binder having the specific material are kneaded to obtain a plastic material, and then the plastic material is heated and dried. This allows a small amount of the synthetic resin binder to be uniformly applied to the sinterable metal powder. By uniformly applying the synthetic resin binder to the sinterable metal powder in this way, it is possible to obtain a sheet with good shape retention during the sheet forming process in the next process, and by using a small amount of the synthetic resin binder, It becomes possible to obtain a high-strength sintered body with low porosity.

Thereafter, by forming the plastic material into a sheet in a thermoplastic state, it is possible to facilitate the forming process and to obtain a raw material sheet that has appropriate flexibility and tear strength at room temperature and is easy to handle. can.

[Brief explanation of drawings]

Figure 1 is a sectional view of a press mold manufactured using the raw material sheet according to the present invention, Figures 2 a to e are illustrations of the manufacturing process of the press mold, and Figure 3 is the temperature in the sintering process. This is a graph showing the relationship between time and time. S...Sintered body, St...Raw material sheet.

Claims (1)

[Scope of Claims] 1. Constructed in a sheet form from 90 to 99% by weight of sinterable metal powder and 1 to 10% by weight of a synthetic resin binder, the synthetic resin binder being a heat-resistant material with excellent crack resistance. Contains 30 to 70% by weight of a thermoplastic synthetic resin with excellent lamination properties based on the plastic synthetic resin, and the thermoplastic synthetic resin with excellent cracking resistance is selected from tetrafluoroethylene resin, polystyrene resin, and nylon. and the thermoplastic synthetic resin having excellent lamination properties is at least one selected from acrylic resin, polyethylene resin, and butadiene-vinyl acetate copolymer. sheet. 2. At least one thermoplastic synthetic resin with excellent crack resistance selected from tetrafluoroethylene resin, polystyrene resin, and nylon,
30 to 70% of at least one thermoplastic synthetic resin with excellent lamination properties selected from acrylic resin, polyethylene resin, and butadiene-vinyl acetate copolymer.
A step of preparing a liquid synthetic resin binder containing 90 to 99 weight % of a sinterable metal powder and 1 to 10% by weight of a sinterable metal powder.
% by weight of the liquid synthetic resin binder to obtain a plastic material; heating and drying the plastic material; and molding the plastic material into a sheet in a thermoplastic state. A method for producing a raw material sheet for a metal sintered body, characterized in that: