JPS6227149B2 - - Google Patents

Description

[Detailed description of the invention]

This invention maintains constant sintered body dimensions without causing any change in sintered body dimensions even if the carbon content changes.
The present invention relates to a method for producing a Fe--Cu--P--C based sintered alloy member, that is, an Fe-based sintered alloy member containing at least Cu, P, and C as alloy components. It is generally well known that Fe--Cu--P--C based sintered alloy members are widely used as mechanical parts. Normally, this type of Fe-Cu-P-C based sintered alloy member uses Fe powder, Cu ₃ P powder, and graphite powder as raw material powder, and if necessary, Ni
Powder, Mo powder, Cr powder, Mn powder, etc. are also used, and after blending these raw material powders into an appropriate composition, mixing, and forming into a green compact, in a reducing atmosphere,
It is produced by a conventional powder metallurgy process consisting of sintering at a predetermined temperature in the range of 1150°C. However, the resulting Fe--Cu--P--C based sintered alloy member has extremely large dimensional changes and large dimensional variations compared to the green compact before sintering. Among these, the reason why the size of the sintered body changes significantly compared to the green compact is due to the use of Cu ₃ P powder (contains about 14% P) with a melting point of about 1030°C as the raw material powder. It is considered to be something that does. That is, when the sintering atmosphere reaches approximately 1030°C, which is the melting point of the Cu ₃ P powder, during the temperature raising process in the sintering process, the Cu ₃ P powder melts at once, and the Cu ₃ P that has become a liquid phase melts. It is said that most of this is due to the so-called Copper Growth phenomenon (copper expansion phenomenon), in which the Fe powder, which is the raw material powder, penetrates at once between the Fe powders and expands the mutual spacing between the Fe powders. On the other hand, this copper expansion phenomenon is closely related to the C content of the sintered body, and tends to decrease as the C content increases. This corresponds to Cu: 3.0%, P: 0.49% (more than % by weight, less % by weight) in Figure 1.
This is also clear from the graph showing the relationship between the C content of the Fe-Cu-P-C sintered alloy member, which contains Fe-Cu-P-C sintered alloy members (indicates weight %), and the dimensional change ratio (calculation will be described later) with respect to the green compact. It is. That is, as shown in Fig. 1, as the C content in the Fe-Cu-P-C sintered alloy member increases, the copper expansion phenomenon decreases, and when the C content is 1.0% or more, the copper expansion phenomenon almost never occurs. will no longer occur. This is because during the sintering process, graphite powder as a raw material powder diffuses into the Fe powder before the Cu ₃ P powder melts, causing the Fe powder to melt.
This is thought to be due to poor wettability with the Cu ₃ P liquid phase, which prevents the Cu ₃ P liquid phase from penetrating between the Fe powders at once. However, Fe-Cu-P-C based sintered alloy members,
The C content is usually in the range of 1% or less, and due to the manufacturing process, it is impossible to avoid variations in the amount of graphite powder blended during powder mixing and variations in the carbon potential of the sintering atmosphere. It can be easily understood from FIG. 1 that the C content of the sintered body varies individually with respect to the target C content, and accordingly, the dimensional variation also becomes large. As described above, in conventional Fe-Cu-P-C based sintered alloy members, the dimensional change of the sintered compact relative to the green compact is large due to the copper expansion phenomenon, and the C
Dimensional variations increase depending on the content, and it is currently extremely difficult to keep the dimensions of the sintered body within a predetermined dimensional accuracy. Therefore, from the above-mentioned viewpoint, the inventors of the present invention have developed a method in which the dimensional change of the sintered body with respect to the green compact is small, and
As a result of conducting research to produce Fe-Cu-P-C based sintered alloy members that have consistent dimensions even when the C content varies, we found that
Cu ₃ P, which is conventionally used as a raw material powder when manufacturing Fe-Cu-P-C based sintered alloy parts.
Cu--P containing 3.5-7.0% P instead of powder
When alloy powder is used, this Cu-P alloy powder starts to melt at its eutectic temperature of approximately 714°C during the heating process in the sintering process, as is clear from the Cu-P binary phase diagram. Since this melting occurs continuously and gradually over a temperature range up to approximately 1083℃, which is the melting point of Cu, the generation of the Cu-P liquid phase occurs little by little. Since the Cu-P liquid phase penetrates between the powders very slowly, the distance between the Fe powders is not expanded by the Cu-P liquid phase, and as a result, the sintered body The dimensional change in the Fe-Cu-P-C becomes extremely small, and even if there is a manufacturing variation in the C content of the sintered body, it is compensated for by the action of the Cu-P liquid phase, and as a result, the Fe-Cu-P-C It was found that no matter how the C content in the sintered alloy member changes, the dimensional change of the resulting sintered body relative to the green compact is always approximately constant. This invention was made based on the above knowledge, and is based on the P of Cu-P alloy powder, which is the raw material powder.
The reason for limiting the content to 3.5% to 7.0% is that even if the content is less than 3.5% or exceeds 7.0%,
This is because Cu--P liquid phase generation occurs in a narrow temperature range during the temperature increase process in the sintering process, causing the copper expansion phenomenon. Next, the method of the present invention will be specifically explained using examples. Examples As raw material powders, atomized Fe powder with a particle size of -100mesh and a Cu-P alloy (P:
3.64%) powder, same 350mesh Cu-P alloy (P: 5.13% content) powder, same 350mesh Cu-P
(Contains P: 6.83%) Powder, Natural graphite powder of the same 200mesh, Ni powder of the same 350mesh, Ni powder of the same 350mesh
Mo powder, same 350mesh Cr powder, and same
Prepare 350mesh Mn powder and
350mesh conventional Cu ₃ P powder (P: 13.8% content) was also prepared, and these raw material powders were blended in the proportions shown in Table 1. After mixing for 0.5 hours in a V-type mixer, 6 tons/ The compacts were formed into compacts with dimensions of width: 10 mm x thickness: 10 mm x length: 55 mm at a pressure of cm ² , and then these compacts were heated at a temperature of 1120°C in an ammonia decomposition gas at 10°C/10°C. Sintered alloy members 1 to 30 of the present invention and conventional sintered alloy members 1 to 15 were manufactured by heating at a temperature increase rate of min and sintering under conditions of holding for 30 minutes. In addition, as shown in Table 1, the sintered alloy members 1 to 30 of the present invention are as follows:
All of them use Cu-P alloy powder as raw material powder, and conventional sintered alloy members 1 to 15 are
Cu ₃ P powder is used as the raw material powder. The resulting sintered alloy members 1 to 30 of the present invention
and the longitudinal dimension of conventional sintered alloy members 1 to 15

【table】

[Table] was measured for each of five test pieces, and the change rate with respect to the green compact length, that is, (sintered compact length - green compact length) / (green compact length) × 100
(%) was calculated. Based on these results, Table 1 shows the maximum dimensional change rate, minimum dimensional change rate, and average dimensional change rate, respectively. From the results shown in Table 1, the dimensional changes in all of the sintered alloy members 1 to 30 of the present invention are relatively small compared to the conventional sintered alloy members, and are almost constant even when the C content changes. It is clear that the conventional sintered alloy members 1 to 15 have a relatively large dimensional change and also have a significantly large dimensional variation. As described above, according to the method of the present invention, it is possible to produce a Fe--Cu--P--C based sintered alloy member with relatively small dimensional changes and almost no dimensional variation. During manufacturing, there is no need to take into account the expansion allowance of the sintered body, and it is also almost unaffected by manufacturing conditions that cause variations in C content, making it possible to obtain products with high dimensional accuracy. It brings about useful effects.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between C content and dimensional change rate of Fe-Cu-P-C sintered alloy members.

Claims (1)

[Claims] 1. When producing Fe-Cu-P-C based sintered alloy members by powder metallurgy, P:
A method for producing a Fe--Cu--P--C based sintered alloy member whose sintered body dimensions remain constant despite changes in carbon content, characterized by using Cu--P alloy powder containing 3.5 to 7.0% by weight. .