JP2916940B2 - Copper-based powder composition for powder metallurgy raw materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a copper-based powder composition for a powder metallurgy raw material which hardly causes segregation and dust generation and has excellent fluidity during molding.

<Prior art and its problems> Metal powder is used as a raw material, and it is filled into a pressing die, and the compact that has been compression-molded is further heated and sintered, thereby eliminating the machining process and forming the product at once. Powder metallurgy is a suitable technology for the production of materials and porous parts that are difficult to melt, or for parts that are difficult to finish due to complicated shapes, etc., and its application field is expanding more and more. Showing a trend.

By the way, among the various powder metallurgy raw materials currently used, “copper powder” is an indispensable raw material for the production of oil-impregnated bearings, etc. It is the second largest. In the field of manufacturing such oil-impregnated bearings, copper powder or copper-based powder (for example, copper alloy powder such as bronze) is often used.
In many cases, one or more other alloy element powders are further added and mixed, and after compression molding, sintered to obtain a product in many cases.

However, copper powder or copper-based powder generally tends to have a difference in density, particle size, particle shape, etc. from other alloying element powders. However, it has been a problem that separation phenomena such as segregation and dust generation are likely to occur during subsequent refilling work, transportation, molding, and the like.

However, conventionally, in order to prevent such a separation phenomenon, a method of mechanically mixing white kerosene, spindle oil, or the like into the above-mentioned mixed composition to wet the powder with oil has been taken. However, in this method, a sufficient effect cannot be obtained because the bonding force between the powders is weak, and a remixing step is required before molding, or until the addition of oil deteriorates the fluidity of the powder and leads to molding. Has a problem that the handleability tends to be impaired.

In view of the above, an object of the present invention is to provide a copper-based powder composition for powder metallurgy without causing segregation and dust separation during refilling, transportation, molding, and the like, and An object of the present invention is to establish a means capable of imparting excellent fluidity to smoothly fill every corner of a mold during molding.

<Means for Solving the Problems> The present inventors have conducted intensive studies while repeating many experiments in order to achieve the above object, and as a result, have obtained the following knowledge. (A) Usually, the powder metallurgy product of copper alloy is "dendritic copper powder obtained by electrolytic method" or "60% by weight of this dendritic copper powder.
The copper-based powder (for example, tin, zinc, lead, etc. mixed with copper) containing above) and at least one kind of alloy element powder are mixed and mixed as a raw material. In particular, when a methacrylic resin composed of a methacrylic polymer or copolymer is blended into the mixed raw material, segregation and dust generation during refilling, transporting, and molding of the mixed raw material are effectively suppressed, and the fluidity of the powder raw material during molding is reduced. Is also greatly improved, and the apparent density of the product is significantly increased.

(B) In addition, in the case of a raw material powder mixture for powder metallurgy, especially in a copper-based powder composition, even if a small amount of an additive is added, deterioration of the green compact characteristic is not caused unless there is a sufficient compatibility. However, the addition of the methacrylic resin hardly deteriorates the green compact characteristics.

(C) In addition, since methacrylic resin is completely thermally decomposed even at a low sintering temperature of 700 to 800 ° C, the addition of methacrylic resin to the raw material powder mixture has no adverse effect on the product properties after sintering. Has no effect.

The present invention has been completed on the basis of the above findings and the like. "A copper-based powder composition for a powder metallurgy raw material is mainly composed of a dendritic copper powder obtained by an electrolytic method or this dendritic copper powder. By adding a methacrylic resin to a mixture of a plurality of powder raw materials based on “a powder”, it has excellent segregation resistance during transportation, dust resistance, and excellent molding. In that it combines liquidity ”.

The “powder mainly composed of dendritic copper powder” refers to an alloy composed mainly of dendritic copper powder (containing about 60% or more of Cu) produced using dendritic copper powder obtained by an electrolytic method. Refers to composition powder.

Other powder raw materials include alloy element powders, examples of which include tin, zinc, lead, molybdenum disulfide, graphite, boron nitride, and Sn—Pb alloy powder. The ratio of the alloying element powder mixed with the “copper powder or powder mainly composed of copper” is generally up to 5% by weight of the total powder mixture weight, and rarely exceeds 20% by weight.

The methacrylic resin added to improve the properties of the powder mixture is known as a methacrylic polymer or a methacrylic copolymer, and specifically includes polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethylethyl methacrylate and polymethyl methacrylate. Those selected from the group consisting of butyl methacrylate can be exemplified.

The addition amount of the methacrylic resin is suitably in the range of 0.05 to 5.0% by weight based on the total weight of the powder mixture. Because
If the amount of the methacrylic resin is less than 0.05% by weight, the effect of improving the fluidity of the powder mixture is not sufficient. On the other hand, if the amount exceeds 5.0% by weight, the properties of the sintered body of the powder mixture tend to be adversely affected. But preferably 0.10 to 0.
Adjust to 50% by weight.

<Function> When the methacrylic resin additive is added to and mixed with a mixture of a plurality of powder raw materials based on “resinous copper powder obtained by an electrolytic method or a powder mainly containing this resinous copper powder”. In addition, the bonding strength between the raw material powders is appropriately increased, and separation phenomena such as segregation and dusting, which are likely to occur during refilling, transporting, and molding operations of containers, are effectively suppressed. There is no need to worry about mixing work.

Moreover, when a methacrylic resin is added to and mixed with a mixture of a plurality of powder raw materials based on “resinous copper powder obtained by an electrolytic method or a powder mainly containing this resinous copper powder”,
When a large pressing force is applied to the powder, the apparent density is remarkably increased because it acts to improve the fluidity of the copper-based powder composition, but the compacting properties are not significantly deteriorated. Moreover, this methacrylic resin additive
Even at a low sintering temperature of 700 to 800 ° C., it is completely thermally decomposed, so that the characteristics of the sintered body are not adversely affected.

The adjustment of the “copper-based powder composition” according to the present invention includes:
First, dry mixing of "resinous copper powder obtained by the electrolytic method or powder mainly composed of this resinous copper powder" and alloy element powder is performed by a known technique, and then methacrylic resin is added. It is advisable to employ a technique of further mixing until wet. Here, mixing of the powder may be performed by any of a V-type mixer, a double cone type mixer, a ribbon type mixer, a vertical screw type mixer and the like.

The addition of the methacrylic resin is preferably carried out after dilution with an organic solvent in order to improve the dispersibility of the resin component in the powder mixture, but is not particularly limited to this method.

By the way, in order to reduce the amount of the methacrylic resin to be added, first, a part of “the resinous copper powder obtained by the electrolytic method or the powder mainly composed of the resinous copper powder” (based on the total weight of the powder mixture) Methacrylic resin is added to and mixed with the alloy element powder, and the remaining “resinous copper powder obtained by the electrolytic method or a powder mainly composed of this resinous copper powder” is added. Dry mixing is also effective.

Next, the present invention will be described in more detail with reference to examples and comparative examples.

<Example> Example 1 Bronze powder (obtained by pulverizing a temporary sintered body of dendritic copper powder and tin powder obtained by an electrolytic method as usual, and tin is dispersed in dendritic copper powder. The powder shape is almost the same as that of electrolytic dendritic copper powder): 96.4 wt%, -200 mesh lead powder: 2.4 wt%, -325 mesh zinc powder: 0.9 wt%, mixed with vertical screw type The mixture was added to the apparatus, and while mixing them, "methyl methacrylate polymer (PMMA): 0.25% by weight dissolved in an organic solvent" was added over about 10 minutes, and then mixed for another 20 minutes.

Subsequently, the uniformly wet mixture was dried under reduced pressure in a mixer, and then passed through an 80-mesh sieve.

Then, 0.3% by weight of zinc stearate was mixed with the mixture, and the apparent density, flowability, green compact properties and sintered body properties were evaluated.

The apparent density was measured by packing the mixed powder in a drum of 100 kg, transporting it by a truck for about 200 km, and collecting the powder from the upper and lower portions of the drum.

On the other hand, as a comparative example, a mixture having the same powder composition as described above, but containing 0.01% by weight of spindle oil instead of PMMA, and a mixture containing neither PMMA nor spindle oil were added in the same manner as described above. Adjustments were made and the apparent density, flowability, green compact properties and sintered compact properties were evaluated.

The evaluation of each of the above properties was performed by measuring the following apparent density, fluidity, rattle value, radial crushing strength, and outer diameter dimensional change rate.

Apparent density: mass per unit volume determined according to JIS Z2504, Fluidity: "Time required for a certain amount of powder to flow out of a specified orifice" determined according to JIS Z2502, Rattra value: Japan Society of Powder and Powder Metallurgy (JSPM) Standard 4-69: Edge strength of green compact, Compaction strength: Strength of cylindrical sintered compact or compact specified by JIS Z2507, Outer diameter dimension change: Cylindrical Rate of change of outer diameter before and after sintering of sintered oil-impregnated sintered bearing.

 The evaluation results are shown in Table 1.

From the results shown in Table 1, the following can be confirmed.

i) The copper-based powder composition is a methacrylic resin (in this case, PM
By adding MA), segregation can be extremely reduced, and the fluidity is improved more than when no additive is added (fluidity: 18.2 sec / 50 g). In addition, methacrylic resin (in this case,
Even with the addition of PMMA), the outer diameter dimensional change, radial crushing strength, and rattle value are within the range where there is no practical problem.

ii) On the other hand, segregation occurs when spindle oil is added. The prevention effect is not enough. Moreover, if the segregation is reduced by increasing the addition amount of the spindle oil, the fluidity is further deteriorated, causing a serious problem in practical use.

Example 2 Bronze powder: 96.3% by weight, -200 mesh lead powder: 0.9% by weight, -325 mesh zinc powder: 0.9% by weight, -325 mesh graphite powder: 1.4% by weight were placed in a beaker and mixed. "Methyl methacrylate polymer (PMMA): 0.25% by weight dissolved in an organic solvent" was added over about 10 minutes, and the mixture was further mixed for 10 minutes.

Subsequently, the mixture kept in a uniformly wet state was dried under reduced pressure, and passed through a 60-mesh sieve.

Then, 50 g of a composition in which zinc stearate: 0.5% by weight was mixed was used as a test sample.

On the other hand, as a comparative example, a sample of 50 g of a mixed composition having the same powder composition as above but without adding PMMA was also prepared.

After performing a segregation test on each of these samples in a beaker under the conditions of frequency: 3000 VPM, amplitude: 2 mm, and vibration application time: 5 minutes, the sample in the beaker is divided into two parts, upper and lower, to contain graphite. The ratio was investigated, and the segregation coefficient [Cs] was determined from the value.

The calculation of the powdering coefficient [Cs] is calculated by the formula (Note that Cs = 0 when complete mixing is performed).

The results are shown in Table 2 and plotted in the first graph.
Also shown as a figure.

From the results shown in Table 2 and FIG. 1, the segregation coefficient in the comparative example is “−13.0%”, whereas the methacrylic resin (here, PMMA) is added to the copper-based powder composition according to the present invention. In the case of the composition, the composition was extremely small, such as "-3.3%", which indicates that the composition of the present invention is extremely unlikely to cause segregation.

Example 3 Bronze powder: 97.75% by weight, −325 mesh zinc powder: 0.95% by weight, −325 mesh graphite powder: 0.8% by weight were charged into a vertical screw-type hybrid machine, and “methacrylic acid Methyl polymer (PMMA): 0.25% by weight dissolved in an organic solvent "was added over about 10 minutes, and the mixture was further mixed for 20 minutes.

Subsequently, the mixture kept in a uniformly wet state was dried under reduced pressure in a mixer, and then passed through a 60-mesh sieve.

Then, 0.5% by weight of zinc sulphate was mixed with the mixture, and the fluidity, green compact properties and sintered body properties were evaluated.

On the other hand, as a comparative example, a mixture having the same powder composition as described above but without adding PMMA was prepared in the same manner as described above, and the fluidity, green compact properties and sintered body properties were also evaluated for these mixtures. Carried out.

In addition, the evaluation method of each characteristic was the same as that of the example 1.

 Table 3 shows the results.

From the results shown in Table 3, the copper-based powder composition according to the present invention to which the methacrylic resin (here, PMMA) is added has sufficient properties as a powder metallurgy raw material, and in particular, the fluidity is remarkably improved. (Flow rate: 19.5sec / 50g)

<Summary of Effects> As described above, according to the present invention, it is possible to provide a copper-based powder composition with reduced segregation and dust generation during transportation and the like, and improved fluidity in a mold during molding. And as a result, in powder metallurgy Industrially useful effects such as (i) no need to remix at the time of powder molding, (b) easy to use and easy to mold, (c) small loss during molding, etc. Is brought.

[Brief description of the drawings]

FIG. 1 is a graph comparing the segregation coefficients of the copper-based powder composition of the present invention prepared in the examples and the comparative copper-based powder composition.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B22F 1/00-7/08 C22C 1/04

Claims (3)

(57) [Claims] 1. A mixture of a plurality of powdery raw materials based on dendritic copper powder obtained by an electrolytic method or a powder mainly composed of the dendritic copper powder, and comprising a methacrylic resin. A copper-based powder composition for a powder metallurgy raw material. 2. The copper-based powder composition for a powder metallurgy raw material according to claim 1, wherein the content of the methacrylic resin is 0.05 to 5.0% by weight of the whole powder mixture. 3. The copper powder for a powder metallurgy raw material according to claim 1, wherein the methacrylic resin is selected from polymethyl methacrylate, polyethyl methacrylate, polypropyl methacrylate, polybutyl methacrylate and copolymers thereof. Composition.