JPH06306404A - Production of sintered compact and powder for the compact - Google Patents

Abstract

PURPOSE:To produce a sintered compact improved in wear resistance, etc., by C, having a high green density and high sintered density and especially without its toughness being lowered due to segregation of C. CONSTITUTION:The powder of a 13%-Cr SUS (Stainless steel) having <= about 149mum particle diameter produced by gas atomization and fine CB powder having 10-40mmmu particle diameter and having 40-300ml/100g oil absorption are mixed respectively in a specified amt., 1wt.% of zinc stearate is added as a binder, and the mixture is charged into a bladed mixing agitator and sufficiently agitated. The surface of the SUS powder after being agitated is covered almost uniformly with the fine CB powder. The powder is compacted and sintered to obtain a sintered compact excellent in compact density and sintered density and without any C segregation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a powder compact sintered product and a powder compact for powder compact sintering, and in particular, the high C content improves the wear resistance of the sintered product. The present invention relates to a method for manufacturing a green compact sintered product and a powder for green compact sintering.

[0002]

2. Description of the Related Art Conventionally, in order to improve wear resistance in a powder-sintered product of SUS powder, powder-compacting and sintering using a powder mixture of SUS powder and graphite powder (graphite). Was being done. In addition, in some cases, C was pre-alloyed in the molten metal used for producing the SUS powder by atomization, and the SUS powder in which C was prealloyed was used.

[0003]

However, when graphite is mixed, segregation of graphite may occur, resulting in poor quality of the sintered product. Further, when C is prealloyed, although there is no problem of segregation, it is not possible to improve the green compact density and the density of the sintered product cannot be improved, so that it is difficult to manufacture a high quality sintered product. .

Therefore, in the present invention, a manufacturing method for manufacturing a green compact sintered product having a high green compact density and a high sintering density while achieving the improvement of the wear resistance and the like by C and the green compact sintering method. The purpose is to provide a powder.

[0005]

Means and Actions for Solving the Problems The method for producing a powder-sintered product of the present invention, which has been made to achieve the above object, comprises mixing metal or alloy powder and carbon black fine powder while mechanically cutting them. It is characterized in that it is formed into a compact by using the agitated compact material and then sintered.

Carbon black (hereinafter referred to as CB) is a furnace black (Furnace bla).
ck) or acetylene black (Acetylene)
As is well known as black), particle size 1
It is very fine and has a spherical shape of about 0 ^-3 μm. For this reason,
It is extremely small compared to the metal / alloy powders that are usually used for green compact sintering. On the other hand, since it is formed by thermally decomposing a hydrocarbon or the like in the gas phase, it contains a tar component and is sticky. As described above, since the particle size is significantly different from that of the metal / alloy powder, and the CB has the adhesiveness and the CBs are likely to be aggregated in a dumpling shape, the CB is simply different from the metal / alloy powder.
If only B and B are mixed and stirred, both are separated and a segregation state is likely to occur.

However, according to the present invention, since the fine particles of CB are mixed and stirred while being mechanically cut, the fine powder of CB is not sprinkled into particles, but is uniformly sprinkled on the surface of the metal / alloy powder. Therefore, a sintered product without segregation can be manufactured. Further, since it is a fine powder, CB fills the gap between the metal / alloy powder at the time of compacting and improves the compacting density. Therefore,
The sintered density in the final product is also improved.

Further, the method for producing a green compact sintered product of the present invention is as follows:
As described in claim 2, C is previously formed on the surface of the metal or alloy powder.
It is also possible to perform powder compacting using a powder for powder compact sintering sprinkled with B fine powder and sinter. If you do this,
It is convenient because there is no need to mix and stir while mechanically cutting.

The CB fine powder has an oil absorption of 1
It is desirable to use one of 50 ml / 100 g or less. This is because if the oil absorption amount (tar content) is large, the green compact density cannot be improved so much. This is considered to be because when CB having a high oil absorption amount is used, its adhesiveness becomes too high, and CB plays a role like a spring at the time of powder compaction, so that the powder compact density cannot be improved so much. . It is more desirable that the oil absorption is 100 ml / 10.
The amount is preferably 0 g or less, more preferably 50 ml / 100 g or less. This is because the green compact density tends to increase as the oil absorption decreases.

The present invention is also directed to the powder for powder compact sintering itself. The powder for powder compact sintering of the present invention is obtained by sprinkling CB fine powder on the surface of a metal or alloy powder. And again, the CB fine powder has an oil absorption of 150 ml /
It is preferably 100 g or less, more preferably 100 ml / 100 g or less, and further preferably 50 ml /
It will be 100 g or less. This is because, as described above, the powder density tends to increase as the oil absorption decreases.

[0011]

EXAMPLES Next, examples will be described below in order to further clarify the present invention. In the examples, 13% Cr-based SUS powder produced by gas atomization and fine CB powder were used to form a cylinder (diameter 11.4 mm, height 9. 0 mm) powder compaction was performed.

[0012] SUS powder is a JIS equivalent product, SU
S410, which was classified to have a particle size of about 149 μm or less. As the CB fine powder, those having a particle size as shown in the following table were used. The display symbols in the table mean the display symbols of various test results on the drawing.

[0013]

[Table 1]

In powder compaction, the SUS powder and CB fine powder are blended in a predetermined amount based on the C content expected in the final product, and 1 wt% of zinc stearate is added as a binder. The mixture was put into a mixing stirrer with a blade, and was thoroughly mixed and stirred while being mechanically cut. An electron micrograph of the SUS powder surface after mixing and stirring is shown in FIG. This photo is No. This is an example using the CB fine powder of No. 3 and the case where the CB content is 2.5 wt%. The whole picture is blurred and the metallic luster cannot be confirmed in the photograph,
It means that the fine CB fine powder is almost uniformly sprinkled on the surface of the SUS powder. The CB fine powder itself cannot be visually recognized unless the magnification is further increased.

Next, SUS dusted with this CB fine powder
The powder was put into a mold and was compacted under a load of 7 t / cm ² . Then, the zinc stearate added as a binder was eliminated by first performing the sintering at 500 ° C. for 30 minutes in vacuum, and then the sintering was performed at 1200 ° C. for 60 minutes in the same vacuum. In addition, No. When CB of No. 1 was used, when a C content of 1.0% or more was aimed at, C was separated at the time of mixing and stirring, and a sintered product could not be obtained. In addition, No. When CB of 2 is used, C
When aiming for a content of 1.5% or more, C at the time of mixing and stirring
Was separated, and a sintered product could not be obtained.

On the other hand, for comparison with the prior art, the SUS powder pre-alloyed with C was used alone to compact and sinter the cylindrical body under the same conditions (indicated by symbol X in the figure), and replace CB with graphite. Powder compacting was similarly performed using (particle size of about 10 μm) (indicated by symbol ◇).

First, the apparent density AD and the fluidity FR which are obtained by examining the properties of the powder sprinkled with CB will be described.
In addition, these are No. 1-No. No. 4 was measured only when CB was used. No measurement was made for the case of using CB of 5. The result of examining the relationship of the apparent density AD is shown in FIG. As shown in the figure, the apparent density AD decreased as the CB content increased. This is natural because CB has a lower density than SUS. On the other hand, it was found that the greater the oil absorption amount, the greater the degree of the decrease. It is considered that this is because the larger the oil absorption amount, the higher the tackiness and the bulkiness becomes as a whole.

The flow rate FR is shown in FIG. No. with the smallest amount of oil supply The fluidity was best with 4 CB. On the other hand, no. CB of 1 had the worst liquidity. In addition, No. 2 and No. There was not much difference in liquidity at 3. Although it was not measured this time, No.
No. 5 is also used. As with No. 4, it is expected that the liquidity will improve considerably.

Next, FIG. 4 shows the results of examining the green compact density GD of the pre-alloyed C product and each of the examples after green compacting. As shown, No. It can be seen that in 3, 4, and 5, the green compact density is remarkably improved. Here, No. 1 and No. Three
Have almost the same particle size, and the former has a larger amount of oil supply. In addition, No. 2 and No. No. 3 has a relatively specific surface area, but the amount of lubrication is No. 3. 2 is doubled. From these, it can be seen that the smaller the amount of oil supply, the higher the green compact density GD. This becomes even clearer when the amount of refueling is arranged as shown in FIG.

Next, in order to examine the brittleness of this green compact, a JIS Rattler test was conducted and the Rattler value RV was measured. The results are shown in FIG. The Ratler test is a test in which a powder-molded sample is placed in a cage made of wire mesh and the extent to which the sample collapses when the cage is rotated is measured. The Ratler value RV is the amount dropped from the cage. Shows. RV =
100% means that it completely fell apart and fell from the basket. No. 1, No. When CB of 2 was used, the CB mixed amount was 0.5 wt%, 1.0 w
It was found that even at about t%, it was likely to collapse. From this, it can be seen that the molded body is brittle when the amount of oil supply is large. On the other hand, No. 2.5wt when using 3 CB
There was almost no change in the percentage. No. CB of 4
Was almost destroyed at 2.0 wt% or more. From this, it was also found that the smaller the particle size, the more difficult it is to collapse if the amount of oil supplied is the same. However, the most important factor is considered to be the amount of refueling. No. 1 and No. In No. 3, the particle size is almost the same, but the former is liable to collapse, whereas the latter is almost irreversible.

Next, the results of various investigations on the state after sintering will be described. First, FIG. 6 shows the results of examining the CB addition amount before sintering and the C content after sintering. As can be seen from (A), the C content is slightly decreased by sintering. However, as shown in (B), when the amount of O contained in the SUS powder itself (usually 0.2 wt%) is subtracted from the added CB, it becomes approximately (added C) = (post-sintering C). Become. This means that the decrease in the C content due to sintering does not mean that the added CB does not disappear, but is used for the reduction of O contained in the SUS powder. Therefore, C
The yield does not deteriorate with B, and the same yield is obtained even if graphite is added. Further, in the case of C prealloy, the yield is similar.

Next, the sintered density SD was examined and examined.
As shown in FIG. 3, No. 4, No. It was found that in both Nos. 5 and 5, the sintered density was good, and the sintered density tended to decrease as the amount of oil supply increased. This also becomes clearer when the oil supply amount is rearranged as shown in FIG.

Further, when the shrinkage ratio in the width direction and the shrinkage ratio in the height direction were examined, it was found that there was almost no shrinkage in the comparative example of C prealloy as shown in FIG. Therefore, the compaction due to sintering is small and the sintered density cannot be sufficiently increased. This means that no improvement in product strength can be expected. On the other hand, in the comparative example of graphite and this example, the shrinkage rate was considerably high in the portion having a high C content. Therefore, it was found that the CB mixed type had a better shrinkage than the C prealloy. On the other hand, even in the mixed type, the toughness was lowered in the comparative example using graphite due to the segregation of C. On the other hand, in the example using CB, the sintered product had no C segregation and had good toughness.

Thus, when CB is used, when a sintered product having the same C content is manufactured, the green compact density is improved,
A product having high strength can be obtained by improving the sintering density, and since C segregation does not occur, a product having good toughness can be manufactured. Further, in this case, the smaller the amount of oil supply, the better in producing a sintered product having a particularly high C content. Then, according to the diagram of FIG.
Since the sintered density improves at the boundary of ml / 100g, 1
It can be seen that the amount should be 50 ml / 100 g or less. And, when considering the Ratler value RV and the green compacting density GD comprehensively, it is preferably 100 ml / 100 g.
In the following, it has been found that it is particularly preferable that the amount is 50 ml / 100 g or less. In particular, when a C content of about 2.0 wt% is produced, the oil supply amount is 100 ml / 1
Should be suppressed below 00g.

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above-mentioned embodiments and can be implemented in various modes without departing from the scope of the invention. Nor. For example, it goes without saying that the present invention can be applied to the powder compact sintering using various metal / alloy powders other than SUS powder.

[0026]

As described above, according to the method for producing a powder compact sintered product and the powder for powder compact sintering of the present invention, while improving wear resistance and the like by C, the powder compact density can be achieved. Further, it is possible to manufacture a powder compact sintered product having a high sintering density, and in particular, segregation of C does not cause deterioration in toughness. In particular, as described in claims 3 and 5, when CB with a small amount of oil supply is used, the effect of improving the green compact density and the sintering density is high when a product with a large C content is manufactured.

[Brief description of drawings]

FIG. 1 is an SUS coated with CB according to an embodiment.
It is a microscope picture of the particle structure of powder.

FIG. 2 is a graph of the results of measuring the apparent density of the powder for powder compacting of the example.

FIG. 3 is a graph showing the results of measuring the fluidity of the powder for powder compacting of the example.

FIG. 4 is a graph showing the results of measuring the green density of green compacts according to Examples and Comparative Examples.

FIG. 5 is a graph showing a result of measuring a ratler value of the powder compact of the example.

FIG. 6 is a graph showing the results of measuring the relationship between the CB mixed amount and the C content after sintering for the powder compacts of Examples.

FIG. 7 is a graph showing the results of measuring the sintered density of the green compacts of Examples and Comparative Examples.

FIG. 8 is a graph showing the results of measuring shrinkage ratios in the width direction and the height direction of the powder compacts of Examples and Comparative Examples.

Claims (5)

[Claims] 1. A method for producing a powder compact sintered product, which comprises compacting and sintering a powder compact material obtained by mixing and stirring metal or alloy powder and carbon black fine powder while mechanically cutting the powder. Method. 2. The production of a compacted sintered product characterized by compacting and sintering using a compacting powder for compaction, which is prepared by previously sprinkling carbon black fine powder on the surface of a powder of metal or alloy. Method. 3. The method for producing a green compact sintered product according to claim 1, wherein an oil absorption amount of 150 ml / 100 g or less is used as the carbon black fine powder. 4. A powder for powder compact sintering, which is obtained by sprinkling carbon black fine powder on the surface of a metal or alloy powder. 5. The powder for green compact sintering according to claim 4, wherein the fine carbon black powder has an oil absorption of 150 ml / 100 g or less.