KR20090071400A - Iron base sintered alloy for slide member - Google Patents

Abstract

An iron base sintered alloy for slide member is provided to reduce the content of copper while ensuring its functional effect and to thereby reduce dimension variation in sintering. An iron base sintered alloy for slide member comprises C: 0.6~1.2%, Cu: 3.5~9.0%, Mn: 0.6~2.2%, S: 0.4~1.3%, and the remnant Fe and inevitable impurities. In the alloy structure, at least one of isolated Cu phase or isolated Cu~Fe alloy phase is spread and MnS phase of 2~100mum is spread by 1.0~3.5 mass% in martensite base.

Description

Iron-based sintered alloy for slide members {IRON BASE SINTERED ALLOY FOR SLIDE MEMBER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an iron-base sintered alloy for slide members suitable for use in bearings having a high surface pressure on an inner circumferential surface. In particular, the present invention has a small dimensional change at the time of sintering and an excellent burn-out portion. The present invention relates to an iron-based sintered alloy for a slide member exhibiting properties.

For example, as a slide member which high surface pressure acts on a slide surface, such as a drive part of a vehicle, a machine tool, an industrial machine, or a slide part, carbon steel is cut and quenched and tempered, or what is made of a sintered alloy is used. . In particular, since the sintered alloy can impart self-lubrication property by the impregnated lubricating oil, it has been widely used because it has good baking resistance and wear resistance. For example, Japanese Patent Laid-Open No. 11-117940 discloses a bearing having a slide surface with an iron-based sintered alloy layer made of Cu: 10 to 30% and the balance: Fe.

However, in recent years, since the price of copper is increasing, in the technique which uses 10 to 30% of copper as in Unexamined-Japanese-Patent No. 11-117940, manufacturing cost is comparatively high and it is not practical. In addition, since copper having a low melting point becomes a liquid phase at the time of sintering, there is also a disadvantage that the amount of dimensional change after sintering is large. For this reason, machining is required in order to satisfy the required precision, and manufacturing cost becomes more expensive.

On the other hand, by containing copper in the sintered alloy, the soft Cu phase or the Cu alloy phase is dispersed in the matrix, whereby the aggression to the counterpart member is alleviated and the compatibility with the counterpart member by moderate deformation is improved. For this reason, when the copper content is reduced, the wear resistance decreases, the aggression to the counterpart member increases, and when lubricating oil is insufficient, a crying sound occurs.

Accordingly, an object of the present invention is to provide an iron-based sintered alloy for a slide member which can reduce the amount of copper used and reduce manufacturing costs while maintaining excellent performance by containing copper.

The iron-based sintered alloy for the slide member of the present invention has a total composition of C: 0.6 to 1.2%, Cu: 3.5 to 9.0%, Mn: 0.6 to 2.2%, S: 0.4 to 1.3%, and the balance: Fe and It is made of inevitable impurities, the alloy structure is dispersed in the martensite matrix, at least one of the free Cu phase or the free Cu-Fe alloy phase, and the MnS phase is 1.0 to 3.5% by mass dispersed It is done.

MnS dispersed in the matrix acts as a solid lubricant and prevents the occurrence of crying sounds by preventing metal contact between members even under conditions in which lubricant is insufficient. In addition, while MnS alleviates the aggression to the opponent member, excellent fusion with the opponent member can be obtained. EMBODIMENT OF THE INVENTION Hereinafter, the basis of limitation of this invention is demonstrated with the action of this invention. In addition, in the following description, "%" means the mass%.

〈Base base〉

The base is made of martensite having high hardness and strength so that it can be used under high surface pressure and exhibit wear resistance.

<C: 0.6 to 1.2%>

If the content of C is less than 0.6%, the hardness and strength become insufficient, and the amount of wear increases. On the other hand, if the content of C exceeds 1.2%, the matrix becomes weak and the amount of wear increases. In addition, C is decarburized by heating, such as sintering or quenching, and decreases with respect to content in raw material powder, or it may increase by carburization. Content of C in this invention means content after final heat processing is complete | finished.

<Cu: 3.5 to 9.0%>

If the content of Cu is less than 3.5%, the amount of free Cu phase or Cu-Fe phase dispersed in the matrix becomes insufficient, and adhesion with the mating member is likely to occur. On the other hand, when the content of Cu exceeds 9.0%, a liquid phase occurs during sintering, and the amount of dimensional change after sintering increases.

<Solid lubricant>

The solid lubricant is dispersed in the matrix to enable the reduction of the friction coefficient under the conditions in which lubrication with oil is insufficient, the reduction in the aggressiveness to the counterpart member, and the improvement of the intimacy with the counterpart member. Typical solid lubricants include graphite, MoS ₂ , FeS, CuS, WS ₂ , and MnS. Since graphite diffuses in iron at the time of sintering, it is difficult to liberate and disperse in the matrix, and the amount of graphite is liberated. A large amount of cement precipitates and weakens cementite in the base, and increases the relative aggression, which is undesirable. Since MoS ₂ , FeS, CuS, WS ₂ , are easily decomposed during sintering, the dispersion state in the matrix after sintering is easy to disperse, and increasing the addition amount to secure the dispersion amount increases the material cost and decreases the strength. This is undesirable. In view of this, MnS is very stable and is preferable as a solid lubricant to be dispersed in a matrix in order to obtain an iron-based sintered alloy for a slide member having excellent lubrication characteristics and strength characteristics.

<MnS: 1.0 to 3.5%>

When the content of MnS is less than 1.0%, the action as a solid lubricant is insufficient. On the other hand, when the content of MnS exceeds 3.5%, the known strength decreases and the amount of wear increases under conditions with high surface pressure.

<MnS phase size: 2 to 100 µm>

If the size of the MnS phase is less than 2 µm, the function as a solid lubricant is insufficient. On the other hand, when the size of MnS phase exceeds 100 micrometers, a known intensity | strength will fall.

It is preferable to produce a MnS phase by adding MnS powder in material powder. Since MnS is more stable than MoS ₂ and graphite, it is difficult to decompose during sintering. Therefore, while a sufficient effect can be obtained with a small addition amount, it is easy to control the dispersion amount to a base, and the performance of a slide member can be stabilized. Moreover, it is preferable that MnS powder contains 90 mass% or more of particle | grains whose particle diameter is 15 micrometers or less. By adding in finely divided MnS powder in this way, the dispersibility to a matrix becomes favorable. Moreover, although MnS particle may disperse | distribute in a matrix in the form which aggregated with each other, there is no problem in the performance of a slide member.

According to this invention, since MnS supplements the effect | action by Cu, the usage-amount of copper can be reduced, maintaining the outstanding performance by containing copper. Thereby, since the amount of dimensional change at the time of sintering can be reduced, the effect of reducing processing cost in addition to material cost is acquired.

Hereinafter, an Example demonstrates this invention further in detail.

In order to manufacture the sintered alloy of the bearing, the following raw material powder was prepared.

1.Atomize Iron (Kobe Steel Mill Atmel 300M)

2. Electrolytic Copper Powder (CE15, Fukuda Metal Foil Industry)

3. Natural Graphite Powder (Japan Graphite JCPB)

4. Manganese Sulfide Powder (MnS-E manufactured by Heganes)

5. Zinc stearate (Fedecochem ZNS730 manufactured by ADEKA Chemical Supply)

These powders were mix | blended so that the whole composition might become the ratio shown in Table 1. In addition, zinc stearate is added for lubrication at the time of shaping | molding, and when the mixed powder except this was made into 100%, 0.75% was added with respect to all the mixed powders.

The powder blended as described above was mixed in a V-type mixer for 30 minutes, compression molded into a bearing cylindrical shape having a density of 6.2 g / cm 2 and a density ratio of 80% with respect to the mixed powder, and the molded body was sintered at 1130 ° C. for 20 minutes. Subsequently, the sintered compact was carburized and quenched at 850 ° C, and tampered at 180 ° C. Then, after finishing with an inner diameter of 30 mm, an outer diameter of 36 mm, and a length of 25 mm by cutting, the pores of the sintered body were impregnated with lubricating oil (gear oil equivalent to ISO VG460), and a sample was obtained. Nos. 1 to 16 were obtained. Further, for the comparison instead of the MnS powder is blended in the ratio indicating the MoS ₂ in Table 1, except that the sample was obtained under the same conditions as in sample No.17 No.1~16.

In Table 1, the dimensional change after sintering of sample No.1-17 was shown by ellipse amount. The ellipse amount is a value obtained by subtracting the minimum measured value from the maximum measured value of the inner diameter of the sample. In Table 1, the value which deviates from the range prescribed | regulated by this invention, and the characteristic value recognized as fail are underlined.

As shown in Table 1, in sample No. 16 in which the Cu content exceeds the upper limit (9%) of the present invention, it is understood that the elliptic amount is very large and the dimensional change during sintering is severe. In addition, the rolling strength of Sample No. 1-17 is shown in Table 1. As shown in Table 1, the sample No. 8 and the content of MnS exceeding the upper limit (3.5%) of the present invention, and the sample No. 10 whose C content is lower than the lower limit (0.6%) of the present invention, Since sample became weak in sample No. 14 whose content of C exceeds the upper limit (1.2%) of this invention, the rolling strength was low.

Next, the bearing test was done about sample No.1-17. The bearing test was carried out by fixing the sample to the housing of the tester, attaching the shaft of the S45C quenched steel to the hole of the sample, applying a load evenly in the direction perpendicular to the axis center, and rotating it at 100 rpm for 200 hours at a surface pressure of 25 MPa. Table 1 shows the friction coefficient at the beginning of operation and the amount of wear after operation for 200 hours.

As shown in Table 1, the sample No. below which the Cu content is below the lower limit (3.5%) of the present invention. In 2 and 3, the friction coefficient was high and as a result, the wear amount of the counterpart material increased. In particular, in sample No. 1 in which the content of Cu was below the lower limit of the present invention, baking with the counterpart occurred, and the bearing test was stopped. In addition, in Sample No. 4 in which the content of MnS was below the lower limit (1.0%) of the present invention, the friction coefficient was high, and as a result, the amount of wear of the counterpart material increased. On the other hand, in sample No. 8 in which the content of MnS exceeded the upper limit (3.5%) of the present invention, the known strength decreased, and the amount of wear of the sample increased.

In sample No. 10 where the content of C was below the lower limit (0.6%) of the present invention, since the hardness and the strength were low, the amount of abrasion of the sample increased. On the other hand, in sample No. 14 in which the C content exceeded the upper limit (1.2%) of the present invention, the matrix became weak and the amount of abrasion of the sample increased. In addition, in Sample No. 17 in which MoS ₂ powder was added in place of MnS powder, MoS ₂ was decomposed by sintering and Mo was dissolved in the matrix. As a result, the initial friction coefficient was high due to lack of lubrication, and the matrix was cured. As it became finer, the amount of wear of the counterpart increased.

Regarding the above comparative examples, in the examples of the present invention, the friction coefficient, the strength and the dimensional change were all excellent, and in the bearing test, both the sample and the counterpart had little wear.

The iron-based sintered alloy for a slide member of the present invention is suitable for use in a slide member in which high surface pressure acts on the slide surface, such as a drive portion or a slide portion of a vehicle, a machine tool, an industrial machine, or the like. Specifically, bearings for press machines, bearings for linkages of brake devices such as vehicles, bearings for hinges, bearings for joints such as industrial robots, bearings for casters, and the like can be given.

Claims (3)

The total composition is composed of C: 0.6 to 1.2%, Cu: 3.5 to 9.0%, Mn: 0.6 to 2.2%, S: 0.4 to 1.3%, balance: Fe and inevitable impurities, and the alloy structure thereof, At least one of the free Cu phase or the free Cu-Fe alloy phase is dispersed in the martensite matrix, and 1.0 to 3.5% by mass of the MnS phase is dispersed.基: iron-base) Sintered alloy. The method according to claim 1, An iron-based sintered alloy for a slide member, wherein the dispersed MnS phase has a size of 2 to 100 µm. The method according to claim 1 or 2, The said MnS phase is produced by adding MnS powder to a material powder, The said MnS powder contains 90 mass% or more of particle | grains whose particle diameter is 15 micrometers or less, The iron-based sintering alloy for slide members.