JP2553374B2 - Sintered alloy material for oil-impregnated bearing and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION “Object of the Invention” The present invention relates to a sintered alloy material for oil-impregnated bearings and a method for producing the same, which is excellent in conformability to a shaft material, has a low friction coefficient, and has a small temperature rise during operation. Moreover, it is an object of the present invention to provide a bearing material suitable for a bearing for audio equipment, which has a high resistance to a load and is excellent in corrosion resistance, and a preferable manufacturing method thereof.

(Industrial field of application) A bearing material and its industrial manufacturing technology that can easily secure the coaxiality and stabilize the rotation speed under the use condition in which the rotating shaft is supported by two bearings.

2. Description of the Related Art Sintered alloy bearing materials are widely used for oil-impregnated bearings, etc., and JIS standards are also stipulated for various industrial equipment, etc., and their composition is pure iron, iron-copper, iron- Various materials and types such as carbon-based, iron-copper-carbon-based, iron-copper-lead-based, bronze-based, copper-based, lead-bronze-based are defined.

Incidentally, for example, in Japanese Patent Laid-Open No. 56-51554, it is announced that a green compact made of iron powder and brass powder is sintered.

Problems to be Solved by the Invention In the above-described conventional ones, iron powder is generally used when importance is attached to strength, although different properties can be obtained depending on the composition of the components. Is essential. However, in the case of using this iron powder, the friction coefficient is large and the mating member such as the shaft portion is damaged and worn. It also has the disadvantage of being extremely inferior in corrosion resistance.

What covers the disadvantages when using such iron powder is a sintered material using copper powder, but in this copper-based material there are disadvantages such as insufficient strength and high cost. Have

As a means for adjusting the disadvantageous relationship between such iron-based and copper-based materials, for example, Japanese Patent Laid-Open No. 57-169064 is used in combination with iron powder and copper powder, or bronze, brass, lead, nickel silver Although the alloy material as described above is used in combination with such alloy powder, in the conventional one in which each metal or alloy powder is used in combination, the specific gravity of each raw material powder is different, and the adjustment is performed, Segregation is liable to occur in handling, and in the case where iron-based powder was used in a relatively large amount, the above-mentioned drawbacks regarding the friction coefficient and corrosion resistance as an iron-based material were revealed, and it was due to the use of copper powder and alloy powder. The merit is scarce. On the other hand, when copper or a copper-based alloy is used in a relatively large amount, it becomes expensive and the above disadvantages of the copper-based material cannot be avoided.

It should be noted that the compression moldability is not always preferable in the conventional ones as described above, and therefore it is necessary to increase the molding pressure to some extent or to improve the compression molding by blending a solid lubricant. However, the products containing this solid lubricant are disadvantageous in that they are inferior in strength and the durability of the compression molding die is not sufficiently obtained.

Further, as described above, in the case of simply mixing the copper powder, both powders having different characteristics are exposed in each piece, for example, iron powder 70
wt% and 30 wt% of copper powder were carefully mixed, compacted and then sintered, and the structure is microscopically magnified as shown in Fig. 3, showing that between iron powder (1) It is clear that the copper powder (2) is scattered and the exposed area ratio is in accordance with the compounding ratio.

On the other hand, today one of the important uses of such bearing materials is
One of them is audio equipment.For example, capstan shafts in tape players and video tape decks rotate from high speed to low speed under the condition that an inertially rotating flywheel is attached to one end. At the same time, it is indispensable to secure the copper axial degree, and in addition, it is necessary to have a low coefficient of friction and good conformability, so that it is required to effectively prevent wow, flutter, noise and other obstacles, It is very difficult to immediately respond to such requests. That is, the flywheel, which is necessary for obtaining a stable speed (rotation), acts as a source of core runout, and suppressing the bearing and bearing it is just strength or familiarity and can not be solved. Yes,
It is inevitably technically difficult to satisfy such a relationship effectively and to allow a relatively thin rotary shaft to be supported in a stable state without center runout under a moderately high speed rotation condition.

"Structure of the Invention" (Means for Solving the Problems) 1. Fe: 20 to 55 wt%, Cu: 30 to 75 wt%, Sn: 2 to 12 wt%, Pb:
2.5 to 9 wt% of the Fe particles, and 95% or more of the Fe particles are covered with Cu or a copper alloy, and have a porosity of 15 to 28 vo
A sintered alloy material for oil-impregnated bearings having a sintered structure of 1%.

2. One or both of tin-lead alloyed powder or copper-tin-lead alloyed powder is added to 100 parts by weight of iron powder coated with 25 to 60 wt% of copper at a coverage of 95% or more. A method for producing a sintered alloy material for oil-impregnated bearings, which comprises compacting and mixing 10 to 150 parts by weight of a raw material powder, and then sintering at 500 to 780 ° C.

(Function) Fe: 20 wt% or more mixed in powder form functions as a skeleton in the sintered alloy body, and has a function of preventing runout of the rotating shaft while securing strength, particularly coercive force against load. This Fe is 55wt
By setting the content to be not more than%, Cu, Sn, and Pb can be appropriately mixed, and the compatibility with the bearing can be obtained, the friction coefficient can be reduced, and the temperature rise can be reduced.

When the Cu content is 30 wt% or more, at least the Fe
The particle surface is sufficiently covered so that the coverage is 95% or more and the thickness of the coating is appropriately obtained, so that even under bearing conditions, Fe particles are exposed during bearing and corrosion resistance is secured. By setting the upper limit of this Cu to 70 wt%, the minimum required amounts of Fe, Sn, and Pb can be mixed, and the action due to them can be properly obtained.

Since the coating rate with Cu is 95% or more, the iron powder particles are coated with Cu in an appropriate perfect state, and sufficient corrosion resistance is secured.

By containing Sn in an amount of 2 wt% or more and Pb: 2.5 wt% or more, the compatibility with the shaft material is improved, and the friction coefficient can be appropriately reduced. Low cost can be obtained by setting the upper limit of Sn to 12wt%, and the upper limit of Pb is 9wt%, especially 7wt.
%, In combination with the above content, the balance with Fe and Cu can be secured, and the above-mentioned characteristics can be effectively obtained.

By setting the porosity to 15% by volume or more, a preferable oil content for the bearing can be secured and an effective lubricating effect can be obtained. Also, by setting the upper limit to 28% by volume, it is possible to obtain an appropriate mechanical strength as a bearing. By covering more than 25% by weight of copper with respect to the iron powder, the exposure of the iron powder is effectively prevented, the corrosion resistance is improved and the powder compacting is facilitated. By setting the upper limit of the coated copper content to 60 wt%, tin-lead and the like can be appropriately added and alloyed.

In this way, the powder compact formed of iron powder coated with copper secures the skeletal function of iron powder, and properly suppresses the runout of the shaft material due to the interaction with other compounded metal components as described above. In addition, the compatibility with the shaft material is improved, and load resistance and the like can be sufficiently obtained. Of course, by adding a considerable amount of iron powder as described above, the cost of the product can be reduced.

By adding and mixing tin-lead or an alloyed copper powder of copper-tin-lead to the copper-coated iron powder as described above, the conformability to the counterpart member such as the shaft material is further improved, and the friction coefficient and the continuous rotation The temperature rise is further reduced. This alloyed copper powder with tin and lead improves the sinterability of the copper-coated iron powder,
A favorable sintered state is formed at a relatively low temperature of about 0 to 750 ° C.

Such an alloyed copper powder with lead and tin cannot sufficiently obtain those effects when the amount is less than 10 parts by weight with respect to 100 parts by weight of the copper-coated iron powder, while those effects are obtained even when it exceeds 150 parts by weight. Is saturated, and the skeleton or core function of the iron powder in the copper-coated iron powder is likely to be impaired, which of course is expensive, which is not preferable.

In any case, the above-described copper coating on iron powder and alloying copper powder with tin and lead facilitates powder compaction.

(Example) Explaining specific embodiments of the present invention as described above, in the present invention, the iron powder coated with copper as described above is used, and the coating of copper on such iron powder is described. Can be carried out by any of an electroplating method, a hot dipping method, an electroless plating method, a thermal spraying method or a dry plating method. Some of the specific copper coatings are as shown in FIGS. 1 and 2, and the copper coating (2a) is formed on the surface of the iron powder (1) to cover substantially the entire surface but partially project. The part (3) or the fine powder part (3a) is obtained as well, which is also made of copper.

Regarding the coating amount of copper as described above, the amount can be appropriately selected by appropriately selecting coating treatment conditions such as the amount of electricity and time, or the heating temperature for the copper bath and the preheating temperature for the iron powder, As described above, the range adopted in the present invention is 25 to 60 wt%. A more preferable range is 28 to 45% by weight.

In any case, the peripheral surface of the iron particles (1) is completely covered with the copper coating (2a) by the coating treatment as shown in FIGS. 1 and 2 above, and the coverage is at least 95%. % Or more. Even if it is possible to confirm by microscopic observation that the small protrusions (3) are formed by the copper coating (2a) as described above, it is due to the copper content and is appropriately deformed at the time of compacting,
In any case, it tends to give a compacting effect more easily than compacting iron powder itself, and also causes segregation and other inconveniences such as when mixing iron powder and copper powder. There is no.

The size of the iron powder particles as the raw material is not particularly limited, but it is further expanded from the 100 mesh or less (including 320 mesh or less) that has been generally adopted in the past for producing pure iron-based sintered bodies. Those having the above-mentioned particle range can be adopted. In other words, even relatively fine-grained ones can be treated in the same manner as those in the conventional general range in terms of particle size by copper coating and the particle size can be treated in the same manner as in the conventional general range. Even those having a large diameter exceeding the normal particle size range can be formed to the same or more easily by a compacting process similar to the conventional method.

As tin-lead or copper-tin-lead alloying powder, Sn: 2
-12 wt%, preferably 5-8 wt%, Pb: 1-15 wt% preferably 2-8 wt%, the balance consisting of Cu or Sn containing Pb 10-63 wt%, They are alloyed. That is, alloyed in this way, in particular Sn and Pb will be a solder-like behavior by alloying, which is alloyed with Cu and is also familiar with the copper-coated iron powder as described above. Will be things.
In alloy materials, if Sn is less than 2 wt% and Pb is less than 2.5 wt%, it is difficult to obtain the above relationship, while Sn exceeds 12 wt% and Pb
When the content exceeds 7 wt%, the bondability due to sintering with the copper-coated iron powder tends to deteriorate.

The compounding ratio of the copper-coated iron powder and the copper-tin-lead alloyed copper powder is as described above, but the preferred compounding ratio is 10 to 150 parts by weight with respect to 100 parts by weight of the copper-coated iron powder.

Compacting for sintering generally has a porosity of 23 to 38 vol.
%, Especially about 26 to 32 vol%, and less than 26 vol%, especially
If it is less than 23 vol%, it is difficult to secure an appropriate compression allowance for sizing performed after sintering, and to obtain the porosity for obtaining the target oil content after the sizing when it is used as an oil-impregnated bearing. Become. On the other hand, if the porosity exceeds 32 vol%, and especially if it exceeds 38 vol%, there is a high possibility of partial defects or destruction even during handling after sintering or during sintering.
Not preferred.

As the iron powder coated with copper according to the present invention, generally, the iron powders having substantially the same coverage are adopted, but in some cases, the iron powders having different coverages are mixed and used. You can For example, copper coverage of 10% and 20%
Alternatively, 30% is mixed, and the alloyed copper powder described above is further added to this.

Generally, the powder compaction is performed by a punch provided in the upper and lower sides of a mold with a pressing force of about ² to 3 Ton / cm ² . This molding pressure is about 70 to 85% of the molding pressure for iron powder.

The material compacted as described above is generally sintered in a reducing or inert atmosphere. The sintering temperature is generally 500 to 780 ° C, but a preferable range is 55
It is 0 to 700 ° C., and the sintering time can be appropriately carried out within the range of about 30 to 60 minutes.

The above-mentioned sintering is followed by sizing treatment to obtain a product having a desired size and porosity, and the compression margin for such sizing is generally 20 to 35% of the porosity of the sintering. The porosity of the product obtained after sizing is of the order of 15-28%. If it is less than 15%, a favorable oil content for use as a bearing cannot be obtained, while if it is more than 28%, the product is inferior in strength. More preferable product porosity is 18-23%
Therefore, it is possible to obtain appropriate strength and oil content.

Graphite, molybdenum disulfide, etc. as solid lubricants are naturally added as powders, but solid lubricants such as graphite have a small specific gravity for iron powder, nickel silver powder, and bronze powder. Therefore, it is difficult to disperse the raw materials in a uniform state with other raw material powders simply by mixing such graphite, and the graphite is not used during the handling of cargo, replacement with the press hopper, compaction molding, etc. Segregation occurs due to the floating of the powder and offset. Therefore, experiments have confirmed that it is effective to use a relatively coarse powder of a solid lubricant such as graphite, and to use a powder obtained by classifying and removing the fine powder. That is, the commercially available graphite powder is generally 1 to 30 μm, or 1 to 30 μm.
The graphite as a solid lubricant, which is preferred by the present inventors to have a particle size of 50 μm, has a particle size of 10 to 150 μm, and particularly 20 to 100 μm. Therefore, uniform dispersion can be facilitated, and segregation can be prevented as much as possible during cargo handling and other handling. Fine particles having a particle size of less than 10 μm or less than 20 μm as described above do not generate dust in a classification treatment in a liquid, and can be appropriately classified. For such solid lubricants, light copper coating is applied, and powder compacting,
It can be exposed from the coating through sizing.

A specific example of manufacturing the device according to the present invention is as follows.

Production example Copper powder is applied to iron powder with a particle size of 100 mesh or less, and the electrical current conditions including the plating time are adjusted to prepare a copper coating amount of 40%. 5%
Sn, 5% Pb alloyed copper powder, 63% Sn, 37% Pb tin-lead alloy powder and molybdenum disulfide (MoS ₂ ) lightly coated with copper
Prepare the powder, and use these to No. 1 ~ as shown in Table 1 below.
Made No.7.

That is, regarding the formulations according to No. 1 to No. 7, their specific component compositions and theoretical specific gravities are as shown in Table 2 below.

Each raw material powder as described above has an inner diameter of 6.02 mm and an outer diameter of 12.07 mm.
Then, powder compaction was performed with a target length of 10 mm, which was charged into a continuous sintering furnace at a rate of 70 mm / min and sintered at 650 ° C. The results of the molding density, sintered density, effective porosity, outer diameter and its change, radial crushing strength and hardness of this product are shown in Table 3 below.

The sintered bodies obtained as described above each have an inner diameter of 6.08
mm, porosity of 25% by volume, and outer diameter of 12.00 mm were sized to obtain a product. Porosity after sizing is 24.8-2
It was 5.3%, and it was known to have a preferable structure for oil impregnation. Furthermore, the humidity of 80
%, A corrosion resistance test was carried out at a temperature of 60 ° C., and the period until the occurrence of rust was measured. All were 120 days or longer, and it was confirmed that they had favorable corrosion resistance.

About the obtained product, the rotating shaft rotating at 1500 rpm and 5000 rpm was supported, and the temperature rise was tested, but the temperature rises 40 minutes after the start of rotation (generally the temperature rises up to 30 minutes and there is almost no temperature change thereafter). Temperature is 1500 rpm at 15-16 ℃, 500
It was confirmed that the temperature was about 24 to 25 ° C. at 0 rpm, which was preferable as a bearing.

Further, in contrast to the one according to the present invention, as a comparative material, a bearing was prepared in the same manner as in the above-mentioned manufacturing example by using a raw material powder obtained by adding only 3.6 parts by weight of tin powder to 96.4 parts by weight of iron powder having a copper coverage of 40% by plating. As a result of manufacturing and similarly testing the compatibility, the temperature rise at 1500 rpm is 30 to 31 ° C.
The temperature was 34 to 35 ° C. at 5000 rpm, and the temperature increase was about 10 ° C. or higher than that according to the present invention.

The inventors of the present invention prepared the above-mentioned compound Nos. 1 to 7 by batch sintering at a sintering temperature of 600 ° C. and sintering at 650 ° C. and 700 ° C. for a sintering time of 1 hour. Although the treatment was carried out, the radial crushing strength was ² to 6 kg / mm ² and the hardness was ² to 25 BRH due to the increase in sintering temperature and time.
Even if it fluctuates within a certain range, the other properties were all in accordance with those shown in Table 3 above.

[Advantages of the Invention] According to the present invention as described above, the conformability to the bearing material is excellent, the corrosion resistance is high, and the friction coefficient is low so that the temperature rise at the time of bearing is small and the resistance is high, but the coaxiality and the like This is an invention that can accurately provide a bearing material whose accuracy is easily ensured and which has a great industrial effect.

[Brief description of drawings]

The drawings show the technical contents of the present invention, and FIGS. 1 and 2 are cross-sectional views showing the coating state of some examples of the copper-coated iron powder used in the present invention in a microscopically enlarged manner. FIG. 3 is a microscopically enlarged view showing an example of a surface particle state of a conventional powder compacted with iron powder and copper powder at 70:30. However, in these drawings, (1) shows iron powder, (2) shows copper powder, (2a) shows a copper coating layer, and (3) shows fine powder.

Claims (2)

(57) [Claims] 1. Fe: 20-55 wt%, Sn: 2-12 wt%, Pb: 2.5-9
wt% and the balance Cu, and 95% or more of the Fe particles were coated with Cu or a copper alloy on the peripheral surface.
A sintered alloy material for oil-impregnated bearings having a sintered structure of up to 28 vol%. 2. Covering the iron powder with 25 to 60 wt% of copper on the peripheral surface of 95%.
To 100 parts by weight of the powder coated as described above, either one or both of the tin-lead alloyed powder and the copper-tin-lead alloyed powder is added in an amount of 10 to 150.
500 ~ 7 after pressing the raw material powder mixed with parts by weight
A method for producing a sintered alloy material for oil-impregnated bearings, characterized by sintering at 80 ° C, and then sizing.