JPWO2015004880A1 - Iron powder for bearings and method for producing iron powder for bearings - Google Patents

Abstract

According to the present invention, the addition amount of the raw iron oxide powder is 5-30 mass% with respect to the raw iron powder, the 50% average particle diameter (D50) measured by the laser diffraction method of the raw iron oxide powder is 1.5 μm or less, Furthermore, when the apparent density of the iron powder for bearings is 1.80 Mg / m3 or more and 2.50 Mg / m3 or less and the iron oxidation degree I is in the range of 6 mass% or less, the shaft portion is produced when the impregnated bearing is manufactured. It is possible to obtain porous iron powder for impregnated bearings while reducing Si and Ca, which are element elements that cause wear and deformation of the bearing.

Description

  The present invention relates to a bearing iron powder and a manufacturing method for obtaining the bearing iron powder, and more particularly to a bearing iron powder used for manufacturing an impregnated bearing.

  It is important to maintain an appropriate impregnation rate in the sintered impregnated bearing. If the impregnation rate is low, appropriate lubricity and durability cannot be obtained. However, in order to maintain this appropriate impregnation rate, it is necessary to increase the porosity in the sintered body. However, if the porosity is too high, the mechanical strength of the sintered body is inferior.

  In order to solve this problem, for example, in Patent Document 1, tin powder and metal soap as a lubricant are added to and mixed with copper powder, and further, the powder mixture is compacted and sintered. As a raw material copper powder, there is a disclosure of a technique in which a powder containing 30 to 60% of fine powder having a particle size of 325 mesh or less is employed and the addition amount of metal soap is in a range of 3 to 7%.

  In recent years, reduced iron powder having a larger specific surface area and more voids is used as bearing iron powder than atomized iron powder. Reduced iron powder is obtained by finishing and reducing sponge iron, and is widely used as a raw material for powder metallurgy because its particle shape is irregular and porous, and has excellent moldability and sinterability. ing.

Japanese Patent Publication No.57-45801

  However, the technology described in Patent Document 1 requires a large amount of fine powder of 325 mesh or less as raw material copper powder, such as 30-60%, and also uses metal soap in large quantities, such as 3% or more, and is compacted. Since molding is performed, there has been a problem in that a decrease in productivity due to a decrease in green compact strength typified by the Latra value cannot be avoided.

  Furthermore, the technique described in Patent Document 1 uses copper powder and tin powder as main materials, and requires a considerable amount of those fine powders as described above, and it is necessary to use a larger amount of metal soap than usual. Because of this, there is no choice but to increase the cost of raw materials. Also, in manufacturing operations, the moldability and the need for hot kneading are increased, and special crushing after cooling after kneading is required, increasing the difficulty in manufacturing operations. And other disadvantages.

On the other hand, reduced iron powder obtained by further reducing the iron powder obtained by rough reduction of the mill scale is generally high in purity, but the apparent density is relatively high at 2.40 to 2.80 Mg / m ^3, and formability There is a problem that is low.
In addition, iron powder obtained by rough reduction of iron ore, and reduced iron powder obtained by finish reduction, has an apparent density as low as 1.70 to 2.50 Mg / m ³ and is generally used as iron powder for impregnated bearings. However, there is a problem that the compressibility is bad. Furthermore, iron ore, the purity of the iron oxide is low, gangue components such as SiO _2, CaO is contained, the SiO _2, CaO or the like remaining in the reduced iron powder in a inclusions, the performance degradation of the bearing In other words, there is a concern that when an impregnated bearing is manufactured, wear of the shaft portion and deformation of the bearing are caused.

  The present invention has been developed in view of the above-described situation, and when impregnated bearings are produced, Si and Ca, which are factors that cause wear of the shaft portion and deformation of the bearings, are reduced, and are porous. It is an object of the present invention to provide an iron powder for an impregnated bearing together with its advantageous production method.

The gist of the present invention is as follows.
1. In the iron powder for bearings obtained by mixing the raw powder produced by the atomization method and the raw iron oxide powder to make the raw iron powder, then finishing reduction, secondary pulverization, secondary classification,
The amount of the raw iron oxide powder added is in the range of 5 to 30 mass% with respect to the raw iron powder, and the 50% average particle diameter (D50) measured by the laser diffraction method of the raw iron oxide powder is 1.5 μm. And
The apparent density of the iron powder for the bearing is 1.80 Mg / m ³ or more and 2.50 Mg / m ³ or less, and the iron oxidation degree I calculated by the following formula (1) is 6 mass% or less, and further for the bearing. Iron powder for bearings in which the Ca content in the iron powder is 0.06 mass% or less and the Si content is 0.04 mass% or less.
Iron Degree of oxidation I (mass%) = A / B x 100 (1)
However, A: Oxygen mass in iron powder for bearings
B: Oxygen mass when all iron in the iron powder for bearings becomes Fe ₂ O ₃
[= [Fe mass / (55.85 × 2)] × (16 × 3)]

2. 2. The bearing iron powder according to 1 above, wherein the raw iron oxide powder has a 50% average particle diameter (D50) in the range of 0.6 to 1.2 μm.

3. The iron powder for bearings according to 1 or 2, wherein the iron oxide degree II calculated from the following calculation formula (2) of the raw iron oxide powder is 84 mass% or more.
Iron Degree of Oxidation II (mass%) = C / D x 100 (2)
However, C: oxygen mass in iron oxide powder
D: Oxygen mass when all iron in iron oxide powder becomes Fe ₂ O ₃
[= [Fe mass / (55.85 × 2)] × (16 × 3)]

4). The iron powder for bearings in any one of said 1-3 whose Ca content in the said iron powder for bearings is 0.02 mass% or less.

5). The iron powder for bearings in any one of said 1-4 whose Si content in the said iron powder for bearings is 0.03 mass% or less.

6). It is a manufacturing method of the iron powder for bearings in any one of said 1-5,
After primary classification of raw powder produced by atomization method, raw iron oxide powder with 50% average particle diameter (D50) measured by laser diffraction method of 1.5 μm or less is 5-30 mass% in mixing ratio with the raw powder. After the final reduction, the apparent density of the iron powder was set to 1.80 Mg / m ³ or more and 2.50 Mg / m ³ or less by secondary pulverization and secondary classification, and calculated from the following formula (1). A method for producing iron powder for bearings, wherein the iron oxidation degree I is set to 6 mass% or less, the Ca content in the bearing iron powder is adjusted to 0.06 mass% or less, and the Si content is adjusted to 0.04 mass% or less.
Iron Degree of oxidation I (mass%) = A / B x 100 (1)
However, A: Oxygen mass in iron powder for bearings
B: Oxygen mass when all iron in the iron powder for bearings becomes Fe ₂ O ₃
[= [Fe mass / (55.85 × 2)] × (16 × 3)]

7). 6. The method for producing iron powder for bearings according to 6, wherein the 50% average particle diameter (D50) measured by the laser diffraction method is in the range of 0.6 to 1.2 μm.

8). 8. The method for producing bearing iron powder according to 6 or 7, wherein the iron oxidation degree II calculated from the following formula (2) of the raw iron oxide powder is 84 mass% or more.
Iron Degree of Oxidation II (mass%) = C / D x 100 (2)
However, C: oxygen mass in iron oxide powder
D: Oxygen mass when all iron in iron oxide powder becomes Fe ₂ O ₃
[= [Fe mass / (55.85 × 2)] × (16 × 3)]

9. The manufacturing method of the iron powder for bearings in any one of said 6-8 which makes Ca content in the said iron powder for bearings 0.02 mass% or less.

10. The manufacturing method of the iron powder for bearings in any one of said 6-9 which makes Si content in the said iron powder for bearings 0.03 mass% or less.

  According to the present invention, a porous oil-impregnated bearing can be produced without causing shaft wear and bearing deformation.

It is a flowchart which shows the manufacturing process of the normal iron powder for bearings. It is a flowchart which shows the manufacturing process of the iron powder for bearings in this invention.

Hereinafter, the present invention will be specifically described.
In the present invention, raw powder produced by the atomization method (hereinafter simply referred to as raw powder produced by the atomization method when raw powder is used) and raw iron oxide powder are mixed to obtain raw iron powder, and then the belt. Iron powder for bearings obtained by reduction, secondary pulverization, and secondary classification in a hydrogen atmosphere using a heating furnace such as a formula (hereinafter simply referred to as iron powder for bearings) .
The raw powder in the present invention is a state before spraying molten steel discharged from the converter with high-pressure water, followed by dehydration and drying, further primary pulverization and primary classification, and before being subjected to finish reduction. This powder is magnetically selected as necessary. In addition, bearing iron powder is iron powder used in the manufacture of bearings used to hold rotating shafts. As a feature of the powder, it has pores connected to the outside in the particles. Can be impregnated with lubricating oil. Furthermore, the raw iron oxide powder is usually a powder that exists in any form of wustite (FeO), magnetite (Fe ₃ O ₄ ), and hematite (Fe ₂ O ₃ ). Moreover, the iron oxidation degree is 66.7 mass% for wustite, 88.9 mass% for magnetite, and 100 mass% for hematite.

In the present invention, it is important to satisfy the following conditions.
Addition amount of raw iron oxide powder: 5-30 mass%
In this invention, in order to adjust the apparent density of the iron powder for bearings, the addition amount of raw material iron oxide powder shall be 5-30 mass% (in a mixing ratio with raw powder) with respect to raw material iron powder. If it is less than 5 mass% with respect to the raw iron powder, the apparent density of the obtained iron powder for bearings is increased, resulting in problems described later. On the other hand, when it exceeds 30 mass%, impurities such as Ca become excessive, and when an oil-impregnated bearing is produced using this iron powder, the rotating shaft portion is worn and the bearing is deformed.

50% average particle size (D50) measured by laser diffraction method of raw iron oxide powder: 1.5μm or less The average particle size of raw iron oxide powder is 50% average particle size (D50) measured by laser diffraction method on a volume basis. ) To 1.5 μm or less. This is because if it exceeds 1.5 μm, the reduction efficiency in the finish reduction process is lowered. Preferably, it is in the range of 50% average particle diameter (D50): 0.6 to 1.2 μm.

  The laser diffraction method used in the present invention may follow a publicly known and publicly known laser diffraction method, but the measurement method is preferably a dry method, the compression air pressure is 0.01 MPa, and the transmittance is 90 to 98%.

The apparent density of the iron powder for bearings is 1.80 Mg / m ³ or more and 2.50 Mg / m ³ or less. If the apparent density is less than 1.80 Mg / m ³ , the density in the green compact will not be sufficient when molding into a green compact. When the sintered material is made uniform, a portion having a low strength is partially formed and becomes a starting point of destruction, so that the strength of the sintered material is insufficient. On the other hand, when the apparent density exceeds 2.50 Mg / m ³ , the pores are reduced, so that the oil is difficult to be impregnated and the characteristics as a bearing material are not satisfied.

Above, the amount of raw iron oxide powder added: 5-30 mass%, 50% average particle diameter (D50) measured by laser diffraction method of raw iron oxide powder: 1.5 μm or less, the apparent density of bearing iron powder is 1.80 Mg It is particularly important in the present invention to satisfy the following conditions: 1 / m ³ or more and 2.50 Mg / m ³ or less, and the iron oxidation degree I calculated by the following calculation formula (1) is 6 mass% or less, It is a feature of the present invention that the Ca content in the powder satisfies 0.06 mass% or less and the Si content simultaneously satisfies 0.04 mass% or less, and this is the first embodiment. The amount of raw iron oxide powder added and the apparent density of bearing iron powder are the same as in the first embodiment, and the 50% average particle diameter (D50) measured by the laser diffraction method of the raw iron oxide powder is In a preferable range, that is, in the range of 0.6 to 1.2 μm, the second embodiment is adopted.
Iron oxidation degree I (mass%) = A / B x 100 (1)
However, A: Oxygen mass in iron powder for bearings
B: Oxygen mass when all iron in the iron powder for bearings becomes Fe ₂ O ₃
[= [Fe mass / (55.85 × 2)] × (16 × 3)]

The iron oxidation degree II of the raw iron oxide powder is 84 mass% or more. The iron oxidation degree II of the raw iron oxide powder calculated from the calculation formula (2) shown below is preferably 84 mass% or more (third embodiment). This is because if the iron oxidation degree II of the raw iron oxide powder is less than 84 mass%, the apparent density of the bearing iron powder is not effectively reduced.
Note that 0 mass% corresponds to metallic iron, and 100 mass% corresponds to hematite.
Iron oxidation degree II (mass%) = C / D x 100 (2)
However, C: oxygen mass in iron oxide powder
D: Oxygen mass when all iron in iron oxide powder becomes Fe ₂ O ₃
[= [Fe mass / (55.85 × 2)] × (16 × 3)]

Furthermore, the iron oxidation degree I of the iron powder for bearing needs to be 6 mass% or less, and preferably 5.3 mass% or less.
This is because if the iron oxidation degree I of the iron powder for bearings exceeds 6 mass%, the occurrence of shaft scratches due to iron oxide, particularly magnetite, becomes obvious, so that a sufficient function as a bearing material cannot be achieved. . In addition, the lower limit of the iron oxidation degree I of the iron powder for bearings is not particularly limited, and may be 0 mass%.

Ca content in iron powder for bearings is 0.06 mass% or less, preferably 0.02 mass% or less When Ca bearing inclusions are present when producing bearings, the following reactions are likely to occur after sintering the green compact When this happens, the sintered body expands and the sintered body is deformed. In the worst case, the sintered body is destroyed from the inside. In order to prevent these deformations, the Ca content in the iron powder for bearings is preferably 0.06 mass% or less, and more preferably 0.02 mass% or less (fourth embodiment). Moreover, there is no restriction | limiting in particular in the lower limit of Ca content, 0 mass% may be sufficient.
In addition, when the yield at the time of bearing manufacture is considered, the upper limit of Ca content is 0.06 mass%. Furthermore, the upper limit of the Ca content that can be produced with a good yield is 0.03 mass%.

  Note that the bearing is not useful as a product even if it is deformed by expansion of 1% or less. Therefore, the expansion coefficient at the time of manufacturing the bearing may be appropriately selected depending on the size of the bearing. For example, when a bearing having an outer diameter: 2 mm, an inner diameter: 0.8 mm, and a height: 1.2 mm is manufactured, The variation in diameter is required to be less than 0.2%.

The Si content in the iron powder for bearings is 0.04 mass% or less, preferably 0.03 mass% or less. Table 1 shows inclusions in iron powder and their hardness. Steel is generally used for the shaft, but SiO ₂ contained in the iron powder for bearings has the same Mohs hardness as steel, but has high Vickers hardness, so the presence of SiO ₂ particles causes shaft scratches. It becomes a factor.

As shown in Table 1, when Si-based inclusions are present in the bearing iron powder, the SiO ₂ particles in the bearing damage the rotating shaft received by the bearing. In order to avoid this problem, the Si content in the iron powder for bearings is preferably 0.04 mass% or less, and more preferably 0.03 mass% or less (fifth embodiment). Moreover, there is no restriction | limiting in particular in the lower limit of Si content, 0 mass% may be sufficient.

Next, the manufacturing method of the iron powder for bearings is demonstrated using the manufacturing flow shown in FIG.
As shown in FIG. 1, the conventional method for producing iron powder for bearings is as follows. Raw powder, or iron powder obtained by mixing and coarsely reducing mill scale, iron ore and coke, and coal is first ground and primary classified. Then, after magnetic selection, it was subjected to finish reduction, and then secondary pulverization and secondary classification to obtain iron powder.
On the other hand, as shown in FIG. 2, the method for producing bearing iron powder according to the present invention mixes raw powder and raw iron oxide powder after primary classification and before finishing reduction. There are features.

And the raw material iron oxide powder used in that case is as described above.
(1) Addition amount of raw iron oxide powder (mixing ratio with raw powder): 5-30 mass%
(2) 50% average particle diameter (D50) measured by laser diffraction method of raw iron oxide powder: It is necessary to satisfy the properties of 1.5 μm or less (first embodiment),
(3) 50% average particle diameter (D50) measured by laser diffraction method of raw iron oxide powder: 0.6 to 1.2 μm (second embodiment)
(4) Using the iron oxidation degree II calculated from the above formula (2), the iron oxidation degree II of the raw iron oxide powder is 84 mass% or more (third embodiment).
Each of these is a preferable property.

The resulting iron powder for bearings is
(5) The apparent density of the iron powder for bearings is 1.80 Mg / m ³ or more and 2.50 Mg / m ³ or less, and the iron oxidation degree I calculated by the above formula (1) is 6 mass% or less, and further It is necessary to satisfy the properties that the Ca content in the iron powder for bearings is 0.06 mass% or less and the Si content is 0.04 mass% or less (first embodiment). In the present invention, the final classification is performed by secondary classification. Further adjusted to
(6) Ca content in iron powder for bearings is 0.02 mass% or less (fourth embodiment)
(7) Si content in iron powder for bearings is 0.03 mass% or less (fifth embodiment)
Are preferable properties.

  Here, at the time of finish reduction according to the present invention, an appropriate amount of carbon components such as coke can be added in accordance with a conventional method for producing iron powder for bearings. At that time, the properties of the coke are not particularly limited, and conventionally known ones can be used. Moreover, the manufacturing method of the iron powder for bearings which is not mentioned above can follow the conventional method of the manufacturing method of the iron powder for bearings.

As the atomized raw powder, molten steel was dried and sieved after water atomization. Further, as the coarsely reduced powder, mill scale and iron ore obtained by heat reduction with a carbonaceous material such as coke were used.
Table 2 shows chemical components and physical properties of the atomized raw powder and the coarsely reduced powder.
JC-DC manufactured by JFE Chemical Co., Ltd. was used as the raw iron oxide powder (hereinafter simply referred to as iron oxide powder). Table 2 shows chemical components, iron oxidation degree II, and physical properties. The average particle size (D50) of iron oxide powder 1 was 1.45 μm, iron oxide powder 2 was 0.82 μm, and iron oxide powder 3 was 1.02 μm. Moreover, the iron oxide powder 1 was 95.8 mass%, the iron oxide powder 2 was 94.9 mass%, and the iron oxide powder 3 was 82.7 mass%.
As the graphite powder, one having an average particle diameter (D50) of 4.6 μm was used.
For mixing, a mixed powder of atomized raw powder, iron oxide powder and graphite powder was prepared using a double cone type mixer at a rotation speed of 10 to 15 rpm. Next, the mixed powder was subjected to heat treatment, and the heat treatment (reduction treatment) conditions were set to a temperature of 950 ° C. and a holding time of 65 minutes in a pure hydrogen gas atmosphere.
After the above reduction treatment, the mixed powder was pulverized with a hammer mill and classified with a 212 μm sieve. The iron powder thus obtained was evaluated based on apparent density, chemical composition, and iron oxidation degree I.
Table 3 shows the experimental conditions and the evaluation results of the produced iron powder.

Here, in the present invention, the apparent density of the iron powder for bearings is 1.80 Mg / m ³ or more and 2.50 Mg / m ³ or less in order to ensure the strength of the sintered material and enable sufficient oil impregnation. It needs to be in the range.
Moreover, the iron oxidation degree I of iron powder is 6 mass% or less, preferably 5.3 mass% or less.
Furthermore, it is essential that the expansion rate during the manufacture of the bearing is less than 0.20% due to the variation in the outer diameter when a bearing having an outer diameter of 2 mm, an inner diameter of 0.8 mm, and a height of 1.2 mm is manufactured.

Invention Example 1 uses atomized raw powder as a raw material, and uses iron oxide powder 1 having a D50 of 1.45 μm measured by a laser diffraction method as iron oxide powder, in a mixing ratio with raw powder (relative to raw iron powder). It is the iron powder manufactured on the conditions which satisfy | fill 1st Embodiment which made the compounding quantity of the iron oxide powder 1 20 mass%. At this time, the apparent density was 2.43 Mg / m ³ , and the iron oxidation degree I of the iron powder was 5.2 mass%. The outer diameter fluctuation at the time of manufacturing the bearing was as good as 0.18%.

On the other hand, the comparative example 1 is the iron powder manufactured on the conditions which do not satisfy | fill this invention by using atomized raw powder as a raw material and not including an iron oxide powder. At this time apparent density Apparent density upper limit of the present invention becomes 2.85 mg / m ^3: for greater than 2.50 mg / m ^3, it is seen that does not satisfy the requirements of the present invention. In this case, the outer diameter fluctuation at the time of manufacturing the bearing was as good as 0.18%, but when the oil-impregnated bearing was manufactured, the bearing volume decreased when the pore volume decreased and the oil impregnation amount decreased by 25%. It was inferior in function.

Moreover, the comparative example 2 is the iron powder manufactured on the conditions which do not satisfy | fill 1st Embodiment by making rough reduced powder into all the raw materials. At this time, the apparent density is 2.42 Mg / m ³ , which is less than 2.50 Mg / m ³ , but when the bearing is manufactured by adjusting, forming and firing the iron powder of Comparative Example 2, the expansion coefficient of the bearing However, Invention Example 1 was 0.18%, while Comparative Example 2 was 0.28%. This is because Ca contained in iron powder chemically reacts with moisture and carbon dioxide in the atmosphere after manufacturing the bearing (CaO + H ₂ O → Ca (OH) ₂ or CaO + CO ₂ → CaCO ₃ ). It is because it expanded.

Invention Example 2 uses atomized raw powder as a raw material, and uses iron oxide powder 2 having a D50 of 0.82 μm measured by a laser diffraction method as iron oxide powder, and the blending amount of iron oxide powder 2 at a mixing ratio with raw powder. It is the iron powder manufactured on the conditions which satisfy | fill 2nd Embodiment made into 20 mass%. At this time, the apparent density is 2.45 Mg / m ³ and the iron oxidation degree I of the iron powder is 4.4 mass%, which is an iron powder that satisfies the more preferable conditions of the present invention.

  In addition, above-mentioned invention example 1 is the iron powder manufactured on the conditions which the iron oxidation degree II of iron oxide powder is 95.8 mass%, and satisfy | fills 3rd Embodiment simultaneously. At this time, the iron oxidation degree I of the iron powder was 5.2 mass%.

  On the other hand, the comparative example 3 is the iron oxide powder 3 whose iron oxidation degree II of iron oxide powder is 82.7 mass%, and is the iron powder manufactured on the conditions which do not satisfy 3rd Embodiment. At this time, the iron oxidation degree I of the iron powder was 9.1 mass%, and the iron powder did not satisfy the first embodiment. In this case, the proportion of defective products increased by 5% compared to when the iron oxidation degree I of the iron powder was 6.0 mass%.

  Invention Example 3 is an iron powder that has a Ca content of 0.015 mass% lower than that of Invention Example 1 and satisfies the fourth embodiment. At this time, when the bearing was manufactured by adjusting, shaping, and firing the iron powder of Invention Example 3, the outer diameter fluctuation was 0.11%, which is lower than that of Invention Example 1 and shows good properties.

  Invention Example 4 is an iron powder having a Si content of 0.022 mass% lower than that of Invention Example 1 and satisfying the fifth embodiment. At this time, when the bearing was manufactured by adjusting, molding, and firing the iron powder of Invention Example 4, the outer diameter fluctuation was 0.16%, which is lower than that of Invention Example 1 and shows good properties.

  Invention Example 5 is an iron powder produced using the iron oxide powder 3 as the iron oxide powder and satisfying the second embodiment in which the blending amount of the iron oxide powder 3 is 15 mass% in a mixing ratio with the raw powder. Furthermore, the Ca content is 0.020 mass% lower than that of Invention Example 1, and the iron powder satisfies the fourth embodiment. At this time, when the bearing was manufactured by adjusting, shaping, and firing the iron powder of Invention Example 5, the outer diameter fluctuation was 0.15%, which is lower than that of Invention Example 1 and shows good properties.

Invention Example 6 is iron powder manufactured using the iron oxide powder 1 as the iron oxide powder and satisfying the first embodiment in which the blending amount of the iron oxide powder 1 is 30 mass% in a mixing ratio with the raw powder. At this time, the apparent density was 1.83 Mg / m ³ , and the iron oxidation degree I of the iron powder was 5.1 mass%. Further, the outer diameter fluctuation at the time of manufacturing the bearing was as good as 0.18%.

Invention Example 7 is an iron powder manufactured using the iron oxide powder 1 as the iron oxide powder and satisfying the first embodiment in which the blending amount of the iron oxide powder 1 is 25 mass% in a mixing ratio with the raw powder. At this time, the apparent density was 2.20 Mg / m ³ , and the iron oxidation degree I of the iron powder was 5.1 mass%. Further, the outer diameter fluctuation when the bearing was manufactured was as good as 0.17%.

On the other hand, Comparative Example 4 uses the atomized raw powder as a raw material, uses iron oxide powder 1 as the iron oxide powder, and satisfies the first embodiment because the blending amount of the iron oxide powder 1 is 35 mass% in the mixing ratio with the raw powder. It is an iron powder manufactured under no conditions. In this case, the apparent density is below 1.80 mg / m ³ at 1.74 mg / m ^3, it is understood that the iron powder which does not satisfy the requirements of the present invention. In this case, the outer diameter fluctuation when the bearing was manufactured was 0.20%.

The present invention relates to a manufacturing method and a bearing for obtaining an iron powder and the iron powder bearing bearings, to an iron powder bearing in particular provide for the production of impregnated bearing.

10. The manufacturing method of the iron powder for bearings in any one of said 6-9 which makes Si content in the said iron powder for bearings 0.03 mass% or less.
11. The bearing which uses the iron powder for bearings in any one of said 1-5 as a raw material.

The present invention, which relates to the production of how to obtain the iron powder and an iron powder for this bearing bearing, it relates to an iron powder bearing in particular provide for the production of impregnated bearing.

The gist of the present invention is as follows.
1. In the iron powder for bearings obtained by mixing the raw powder produced by the atomization method and the raw iron oxide powder to make the raw iron powder, then finishing reduction, secondary pulverization, secondary classification,
The amount of the raw iron oxide powder added is in the range of 5 to 30 mass% with respect to the raw iron powder, and the 50% average particle diameter (D50) measured by the laser diffraction method of the raw iron oxide powder is 1.5 μm. And
The apparent density of the iron powder for the bearing is 1.80 Mg / m ³ or more and 2.50 Mg / m ³ or less, and the iron oxidation degree I calculated by the following formula (1) is 6 mass% or less, and further for the bearing. Iron powder for bearings in which the Ca content in the iron powder is 0.03 mass% or less and the Si content is 0.04 mass% or less.
Iron Degree of oxidation I (mass%) = A / B x 100 (1)
However, A: Oxygen mass in iron powder for bearings
B: Oxygen mass when all iron in the iron powder for bearings becomes Fe ₂ O ₃
[= [Fe mass / (55.85 × 2)] × (16 × 3)]

6). It is a manufacturing method of the iron powder for bearings in any one of said 1-5,
After primary classification of raw powder produced by atomization method, raw iron oxide powder with 50% average particle diameter (D50) measured by laser diffraction method of 1.5 μm or less is 5-30 mass% in mixing ratio with the raw powder. After the final reduction, the apparent density of the iron powder was set to 1.80 Mg / m ³ or more and 2.50 Mg / m ³ or less by secondary pulverization and secondary classification, and calculated from the following formula (1). A method for producing iron powder for bearings, wherein the iron oxidation degree I is set to 6 mass% or less, and the Ca content in the bearing iron powder is adjusted to 0.03 mass% or less and the Si content is adjusted to a range of 0.04 mass% or less.
Iron Degree of oxidation I (mass%) = A / B x 100 (1)
However, A: Oxygen mass in iron powder for bearings
B: Oxygen mass when all iron in the iron powder for bearings becomes Fe ₂ O ₃
[= [Fe mass / (55.85 × 2)] × (16 × 3)]

10. The manufacturing method of the iron powder for bearings in any one of said 6-9 which makes Si content in the said iron powder for bearings 0.03 mass% or less .

Above, the amount of raw iron oxide powder added: 5-30 mass%, 50% average particle diameter (D50) measured by laser diffraction method of raw iron oxide powder: 1.5 μm or less, the apparent density of bearing iron powder is 1.80 Mg It is particularly important in the present invention to satisfy the following conditions: 1 / m ³ or more and 2.50 Mg / m ³ or less, and the iron oxidation degree I calculated by the following calculation formula (1) is 6 mass% or less, It is a feature of the present invention that the Ca content in the powder satisfies 0.03 mass% or less and the Si content is 0.04 mass% or less, and this is the first embodiment. The amount of raw iron oxide powder added and the apparent density of bearing iron powder are the same as in the first embodiment, and the 50% average particle diameter (D50) measured by the laser diffraction method of the raw iron oxide powder is In a preferable range, that is, in the range of 0.6 to 1.2 μm, the second embodiment is adopted.
Iron oxidation degree I (mass%) = A / B x 100 (1)
However, A: Oxygen mass in iron powder for bearings
B: Oxygen mass when all iron in the iron powder for bearings becomes Fe ₂ O ₃
[= [Fe mass / (55.85 × 2)] × (16 × 3)]

Ca content in the iron powder for bearings is 0.03 mass% or less, preferably 0.02 mass% or less When Ca bearing inclusions are present in the production of bearings, the following reactions are likely to occur after sintering the green compact When this happens, the sintered body expands and the sintered body is deformed. In the worst case, the sintered body is destroyed from the inside. In order to prevent these deformations, the Ca content in the iron powder for bearings is preferably 0.03 mass% or less, more preferably 0.02 mass% or less (fourth embodiment). Moreover, there is no restriction | limiting in particular in the lower limit of Ca content, 0 mass% may be sufficient .

The resulting iron powder for bearings is
(5) The apparent density of the iron powder for bearings is 1.80 Mg / m ³ or more and 2.50 Mg / m ³ or less, and the iron oxidation degree I calculated by the above formula (1) is 6 mass% or less, and further It is necessary to satisfy the properties that the Ca content in the iron powder for bearing is 0.03 mass% or less and the Si content is 0.04 mass% or less (first embodiment). Further adjusted to
(6) Ca content in iron powder for bearings is 0.02 mass% or less (fourth embodiment)
(7) Si content in iron powder for bearings is 0.03 mass% or less (fifth embodiment)
Are preferable properties.

The gist of the present invention is as follows.
1. In the iron powder for bearings obtained by mixing the raw powder produced by the atomization method and the raw iron oxide powder to make the raw iron powder, then finishing reduction, secondary pulverization, secondary classification,
The amount of the raw iron oxide powder added is in the range of 5 to 30 mass% with respect to the raw iron powder, and the 50% average particle diameter (D50) measured by the laser diffraction method of the raw iron oxide powder is 1.5 μm. And
The apparent density of the iron powder for bearings is 1.80 Mg / m ³ or more and 2.50 Mg / m ³ or less, and the iron oxidation degree I calculated by the following formula (1) is 2.36 mass% or less. Iron powder for bearings having a Ca content of 0.03 mass% or less and an Si content of 0.04 mass% or less.
Iron Degree of oxidation I (mass%) = A / B x 100 (1)
However, A: Oxygen mass in iron powder for bearings
B: Oxygen mass when all iron in the iron powder for bearings becomes Fe ₂ O ₃
[= [Fe mass / (55.85 × 2)] × (16 × 3)]

3 . 3. The bearing iron powder according to 1 or 2 , wherein a Ca content in the bearing iron powder is 0.02 mass% or less.

4 . The iron powder for bearings according to any one of the above items 1 to 3 , wherein the Si content in the iron powder for bearings is 0.03 mass% or less.

5 . It is a manufacturing method of iron powder for bearings given in any 1 paragraph of the above-mentioned 1-4 ,
After primary classification of raw powder produced by atomization method, raw iron oxide powder with 50% average particle diameter (D50) measured by laser diffraction method of 1.5 μm or less is 5-30 mass% in mixing ratio with the raw powder. After the final reduction, the apparent density of the iron powder was set to 1.80 Mg / m ³ or more and 2.50 Mg / m ³ or less by secondary pulverization and secondary classification, and calculated from the following formula (1). A method for producing iron powder for bearings in which the iron oxidation degree I is set to 2.36 mass% or less, and the Ca content in the bearing iron powder is adjusted to 0.03 mass% or less and the Si content is adjusted to 0.04 mass% or less. .
Iron Degree of oxidation I (mass%) = A / B x 100 (1)
However, A: Oxygen mass in iron powder for bearings
B: Oxygen mass when all iron in the iron powder for bearings becomes Fe ₂ O ₃
[= [Fe mass / (55.85 × 2)] × (16 × 3)]

6 . 6. The method for producing iron powder for a bearing according to 5 , wherein the 50% average particle diameter (D50) measured by the laser diffraction method is in the range of 0.6 to 1.2 μm.

7 . The manufacturing method of the iron powder for bearings of said 5 or 6 which makes Ca content in the said iron powder for bearings 0.02 mass% or less.

8 . Method of manufacturing a bearing iron powder according to any one of claims 5-7 for the Si content of the iron powder in a said bearing less 0.03 mass%.

Above, the amount of raw iron oxide powder added: 5-30 mass%, 50% average particle diameter (D50) measured by laser diffraction method of raw iron oxide powder: 1.5 μm or less, the apparent density of bearing iron powder is 1.80 Mg In the present invention, it is particularly important that the present invention satisfies the following conditions: 1 / m ³ or more and 2.50 Mg / m ³ or less, and the iron oxidation degree I calculated by the following calculation formula (1) is 2.36 mass% or less, The feature of the present invention is that the Ca content in the iron powder satisfies 0.03 mass% or less and the Si content is 0.04 mass% or less at the same time. This is the first embodiment. The amount of raw iron oxide powder added and the apparent density of bearing iron powder are the same as in the first embodiment, and the 50% average particle diameter (D50) measured by the laser diffraction method of the raw iron oxide powder is In a preferable range, that is, in the range of 0.6 to 1.2 μm, the second embodiment is adopted.
Iron oxidation degree I (mass%) = A / B x 100 (1)
However, A: Oxygen mass in iron powder for bearings
B: Oxygen mass when all iron in the iron powder for bearings becomes Fe ₂ O ₃
[= [Fe mass / (55.85 × 2)] × (16 × 3)]

Furthermore, the iron oxidation degree I of iron powder for bearings, Ru should be 2.36 mass% or less.
This is because if the iron oxidation degree I of the iron powder for bearings exceeds 2.36 mass%, the occurrence of shaft scratches due to iron oxide, especially magnetite, becomes obvious, so that it cannot perform a sufficient function as a bearing material. is there. In addition, the lower limit of the iron oxidation degree I of the iron powder for bearings is not particularly limited, and may be 0 mass%.

The resulting iron powder for bearings is
(5) The apparent density of the iron powder for bearings is 1.80 Mg / m ³ or more and 2.50 Mg / m ³ or less, and the iron oxidation degree I calculated from the above formula (1) is 2.36 mass% or less, and It is necessary to satisfy the properties that the Ca content in the bearing iron powder is 0.03 mass% or less and the Si content is 0.04 mass% or less (first embodiment). Adjusted further,
(6) Ca content in iron powder for bearings is 0.02 mass% or less (fourth embodiment)
(7) Si content in iron powder for bearings is 0.03 mass% or less (fifth embodiment)
Are preferable properties.

As the atomized raw powder, molten steel was dried and sieved after water atomization. Further, as the coarsely reduced powder, mill scale and iron ore obtained by heat reduction with a carbonaceous material such as coke were used.
Table 2 shows chemical components and physical properties of the atomized raw powder and the coarsely reduced powder.
JC-DC manufactured by JFE Chemical Co., Ltd. was used as the raw iron oxide powder (hereinafter simply referred to as iron oxide powder). Table 2 shows chemical components, iron oxidation degree II, and physical properties. The average particle size (D50) of iron oxide powder 1 was 1.45 μm, iron oxide powder 2 was 0.82 μm, and iron oxide powder 3 was 1.02 μm. Also, the iron oxidation degree II, the iron oxide powder 1 80.5 mass%, iron oxide powder 2 is 80.5 mass%, iron oxide powder 3 was 63.7 mass%.
As the graphite powder, one having an average particle diameter (D50) of 4.6 μm was used.
For mixing, a mixed powder of atomized raw powder, iron oxide powder and graphite powder was prepared using a double cone type mixer at a rotation speed of 10 to 15 rpm. Next, the mixed powder was subjected to heat treatment, and the heat treatment (reduction treatment) conditions were set to a temperature of 950 ° C. and a holding time of 65 minutes in a pure hydrogen gas atmosphere.
After the above reduction treatment, the mixed powder was pulverized with a hammer mill and classified with a 212 μm sieve. The iron powder thus obtained was evaluated based on apparent density, chemical composition, and iron oxidation degree I.
Table 3 shows the experimental conditions and the evaluation results of the produced iron powder.

Here, in the present invention, the apparent density of the iron powder for bearings is 1.80 Mg / m ³ or more and 2.50 Mg / m ³ or less in order to ensure the strength of the sintered material and enable sufficient oil impregnation. It needs to be in the range.
The iron oxidation degree I of iron powder is 2.36 mass% or less.
Furthermore, it is essential that the expansion rate during the manufacture of the bearing is less than 0.20% due to the variation in the outer diameter when a bearing having an outer diameter of 2 mm, an inner diameter of 0.8 mm, and a height of 1.2 mm is manufactured.

Invention Example 1 uses atomized raw powder as a raw material, and uses iron oxide powder 1 having a D50 of 1.45 μm measured by a laser diffraction method as iron oxide powder, in a mixing ratio with raw powder (relative to raw iron powder). It is the iron powder manufactured on the conditions which satisfy | fill 1st Embodiment which made the compounding quantity of the iron oxide powder 1 20 mass%. At this time, the apparent density was 2.43 Mg / m ³ , and the iron oxidation degree I of the iron powder was 2.36 mass%. The outer diameter fluctuation at the time of manufacturing the bearing was as good as 0.18%.

Invention Example 2 uses atomized raw powder as a raw material, and uses iron oxide powder 2 having a D50 of 0.82 μm measured by a laser diffraction method as iron oxide powder, and the blending amount of iron oxide powder 2 at a mixing ratio with raw powder. It is the iron powder manufactured on the conditions which satisfy | fill 2nd Embodiment made into 20 mass%. At this time, the apparent density is 2.45 Mg / m ³ and the iron oxidation degree I of the iron powder is 1.88 mass%, which is an iron powder that satisfies the more preferable conditions of the present invention.

On the other hand, the comparative example 3 is the iron oxide powder 3 whose iron oxidation degree II of iron oxide powder is 63.7 mass%, and is the iron powder manufactured on the conditions which do not satisfy 3rd Embodiment. At this time, the iron oxidation degree I of the iron powder was 2.60 mass%, and the iron powder did not satisfy the first embodiment. In this case, the proportion of defective products increased by 5% compared to when the iron oxidation degree I of iron powder was 2.36 mass%.

Invention Example 5 is an iron powder produced using the iron oxide powder 3 as the iron oxide powder and satisfying the second embodiment in which the blending amount of the iron oxide powder 3 is 15 mass% in a mixing ratio with the raw powder. Furthermore, the Ca content is 0.0055 mass% lower than that of Invention Example 1, and the iron powder satisfies the fourth embodiment. At this time, when the bearing was manufactured by adjusting, shaping, and firing the iron powder of Invention Example 5, the outer diameter fluctuation was 0.15%, which is lower than that of Invention Example 1 and shows good properties.

Invention Example 6 is iron powder manufactured using the iron oxide powder 1 as the iron oxide powder and satisfying the first embodiment in which the blending amount of the iron oxide powder 1 is 30 mass% in a mixing ratio with the raw powder. At this time, the apparent density was 1.83 Mg / m ³ , and the iron oxidation degree I of the iron powder was 2.12 mass%. Further, the outer diameter fluctuation at the time of manufacturing the bearing was as good as 0.18%.

Invention Example 7 is an iron powder manufactured using the iron oxide powder 1 as the iron oxide powder and satisfying the first embodiment in which the blending amount of the iron oxide powder 1 is 25 mass% in a mixing ratio with the raw powder. At this time, the apparent density was 2.20 Mg / m ³ and the iron oxidation degree I of the iron powder was 2.12 mass%. Further, the outer diameter fluctuation when the bearing was manufactured was as good as 0.17%.

Claims (10)

In the iron powder for bearings obtained by mixing the raw powder produced by the atomization method and the raw iron oxide powder to make the raw iron powder, then finishing reduction, secondary pulverization, secondary classification,
The amount of the raw iron oxide powder added is in the range of 5 to 30 mass% with respect to the raw iron powder, and the 50% average particle diameter (D50) measured by the laser diffraction method of the raw iron oxide powder is 1.5 μm. And
The apparent density of the iron powder for the bearing is 1.80 Mg / m ³ or more and 2.50 Mg / m ³ or less, and the iron oxidation degree I calculated by the following formula (1) is 6 mass% or less, and further for the bearing. Iron powder for bearings in which the Ca content in the iron powder is 0.06 mass% or less and the Si content is 0.04 mass% or less.
Iron Degree of oxidation I (mass%) = A / B x 100 (1)
However, A: Oxygen mass in iron powder for bearings
B: When all the iron in the iron powder for bearings becomes Fe ₂ O ₃
Oxygen mass
[= [Fe mass / (55.85 × 2)] × (16 × 3)]   The bearing iron powder according to claim 1, wherein the raw iron oxide powder has a 50% average particle diameter (D50) in the range of 0.6 to 1.2 µm. The iron powder for bearings according to claim 1 or 2 whose iron oxidation degree II computed from the following formula (2) of the above-mentioned raw iron oxide powder is 84 mass% or more.
Iron Degree of Oxidation II (mass%) = C / D x 100 (2)
However, C: oxygen mass in iron oxide powder
D: When all the iron in the iron oxide powder becomes Fe ₂ O ₃
Oxygen mass
[= [Fe mass / (55.85 × 2)] × (16 × 3)]   The iron content for bearings according to any one of claims 1 to 3, wherein a Ca content in the iron powder for bearings is 0.02 mass% or less.   The iron content for bearings according to any one of claims 1 to 4, wherein the Si content in the iron powder for bearings is 0.03 mass% or less. It is a manufacturing method of iron powder for bearings given in any 1 paragraph of Claims 1-5,
After primary classification of raw powder produced by atomization method, raw iron oxide powder with 50% average particle diameter (D50) measured by laser diffraction method of 1.5 μm or less is 5-30 mass% in mixing ratio with the raw powder. After the final reduction, the apparent density of the iron powder was set to 1.80 Mg / m ³ or more and 2.50 Mg / m ³ or less by secondary pulverization and secondary classification, and calculated from the following formula (1). A method for producing iron powder for bearings, wherein the iron oxidation degree I is set to 6 mass% or less, the Ca content in the bearing iron powder is adjusted to 0.06 mass% or less, and the Si content is adjusted to 0.04 mass% or less.
Iron Degree of oxidation I (mass%) = A / B x 100 (1)
However, A: Oxygen mass in iron powder for bearings
B: When all the iron in the iron powder for bearings becomes Fe ₂ O ₃
Oxygen mass
[= [Fe mass / (55.85 × 2)] × (16 × 3)]   The manufacturing method of the iron powder for bearings of Claim 6 which makes 50% average particle diameter (D50) measured by the said laser diffraction system into the range of 0.6-1.2 micrometers. The manufacturing method of the iron powder for bearings of Claim 6 or 7 which makes the iron oxidation degree II computed from the following formula (2) of the said raw material iron oxide powder 84 mass% or more.
Iron Degree of Oxidation II (mass%) = C / D x 100 (2)
However, C: oxygen mass in iron oxide powder
D: When all the iron in the iron oxide powder becomes Fe ₂ O ₃
Oxygen mass
[= [Fe mass / (55.85 × 2)] × (16 × 3)]   The manufacturing method of the iron powder for bearings in any one of Claims 6-8 which makes Ca content in the said iron powder for bearings 0.02 mass% or less.   The manufacturing method of the iron powder for bearings in any one of Claims 6-9 which makes Si content in the said iron powder for bearings 0.03 mass% or less.

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