JP2008138226A - Cast iron-based sintered sliding member, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a cast iron-based sintered sliding member having excellent sliding characteristics. <P>SOLUTION: The cast iron-based sintered sliding member can be manufactured by subjecting a large amount of wet chips generated at machining of a grown grey cast iron casting using cutting oil to vacuum heating at a degree of vacuum of 0.1 Torr at 600°C for 60 min and to pulverization using a pulverizer into chips which pass a sieve of 36 meshes but do not pass a sieve of 55 meshes, filling the chips into a die to carry out pressing at a compacting pressure of 5 tons per square centimeter and then subjecting the resulting green compact to sintering in a hydrogen gas atmosphere at 1,130°C for 60 min. Moreover, when filling the chips into the die, iron powder can be filled, for the purpose of improving bearing performance, into the die by being mixed with the chips in an amount of 5% based on the weight of the chips. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cast iron-based sintered sliding member excellent in sliding characteristics using a chip obtained by cutting a growth gray cast iron casting in which a base exhibits an all-ferrite structure, and a manufacturing method thereof.

  Conventionally, gray cast iron in which carbon is present in the form of flake graphite is known. Castings made from gray cast iron (grey cast iron castings) are widely used as materials for internal combustion engines because of their large vibration absorption capacity and high thermal conductivity. Gray cast iron is also widely used as a material for industrial machinery and equipment having complicated shapes such as fluid machinery and valves because of its excellent castability. Furthermore, there is known a grown gray cast iron obtained by growing the cast iron by heating the gray cast iron casting for a long time or repeating heating and cooling. It is also known that this grown gray cast iron can be used as an oil-impregnated sliding member having excellent sliding properties by impregnating (performing oil impregnation) a lubricating oil into the porous portion (porous portion) generated by the above growth. Yes. Furthermore, this oil-impregnated sliding member is used as a bearing or a sliding plate.

On the other hand, as a sliding member using the above-mentioned grown gray cast iron, Japanese Patent No. 3795391 “Cast Iron Sintered Sliding Member and Manufacturing Method Thereof” disclosed by the present inventors is known. In this invention, the present inventors first observed chips obtained by cutting grown gray cast iron. From this observation, it was found that a large amount of the enlarged flake graphite was exposed in the substrate of the chip, and that the periphery of the flake graphite was made porous. As a result of various experiments, sintered compacts obtained by sintering green compacts obtained by molding chips of grown gray cast iron are not only excellent in moldability but also solid lubricants such as graphite The inventors have obtained the knowledge that excellent sliding characteristics can be exhibited without adding a separate amount, and have conceived the above invention. In addition, the above invention uses chips that are cut without using a cutting fluid (dry chips), and chips with various particle sizes are generated depending on the cutting conditions. It was characterized by using the powder mixed at a certain ratio. For example, 30% by weight of chips that pass through a 20 mesh screen but not through a 36 mesh screen, 60% by weight of chips that pass through a 36 mesh screen but do not pass through a 55 mesh screen, 10% by weight of chips passing through a 55 mesh sieve are mixed and used. And since these chips do not use cutting fluid, they do not adversely affect the reducing atmosphere during sintering after molding in the mold, and also have chips having three different particle size ranges. Since it is used by mixing, there is an advantage that 90% or more of dry chips generated by cutting can be effectively used, and this is an effective technique for cost reduction.
Japanese Patent No. 3795391

Furthermore, the present inventors conducted verification of technical improvements according to the above-mentioned Japanese Patent No. 3795391 while continuing the research on the above-mentioned invention. As a result, in the present invention, there is a problem that dust is generated because dry chips that do not use cutting fluid are used, and processing using cutting fluid is strongly sought from the viewpoint of environmental hygiene in today's factories. What is being done. Furthermore, since chips having three different particle size ranges are used at a certain ratio, each sorting operation is complicated, and chips having each particle size range remain in the chips depending on cutting conditions. Distortions are also different, and therefore, a problem has been discovered that density fluctuations are likely to occur when compacting chips in a mold and affect the strength of the molded body.

  In order to solve the above-mentioned problems, the above-mentioned problems can be solved by using, as a raw material for cutting chips, wet cutting chips that have been mostly disposed of in the past. The use of powder has the following problems. That is, the problem is that the cutting fluid adhering to the chip is decomposed and sublimated during sintering to break the balance of the reducing atmosphere in the furnace, lowering the density of the sintered body and adversely affecting the strength. In addition, there is a drawback in that wet chips have adhesion of free graphite powder and dust in the environment, which also causes a decrease in the density and strength of the sintered body. On the other hand, as other problems, it is difficult to obtain a certain formability at the time of compaction due to residual stress during processing as in the case of dry chips, and the molding density is likely to vary.

  Thus, the present invention was made on the basis of the knowledge obtained from the results of continuous research after the invention relating to the patent No. 3795391 made by the present inventors while considering the above-mentioned problems in the prior art. The purpose is to recycle the wet gray cast iron chips, which have been mostly disposed of in the past, and to produce a cast iron-based sintered sliding member with sufficient strength and appropriate lubricity, and its manufacture. It is to provide a method.

  In order to achieve the above object, a method for producing a cast iron-based sintered sliding member according to the present invention cuts a growth gray cast iron casting in which the base exhibits an all-ferrite structure, and the chips obtained by the cutting are removed from the vacuum furnace. A heating step of heating inside, a selection step of pulverizing the above-mentioned chips and selecting only chips in a predetermined particle size range as raw material powder, and the raw material powder alone or the raw material powder with iron powder or stainless alloy powder In addition, a filling step of filling the mixed powder into the mold and forming the green compact by compression molding the mold at a molding pressure in the range of 4 tons / square cm to 5 tons / square cm. A sintering process in which the green compact is sintered in a neutral or reducing atmosphere at a temperature in the range of 1100 ° C to 1150 ° C for a time in the range of 30 minutes to 90 minutes. This consists of a ligation process And the first gist.

  Next, in order to achieve the above object, in the method for producing a cast iron sintered sliding member according to the present invention, the heating in the heating process of the first aspect is performed in a vacuum furnace at 1 Torr (100 Pa) or more and 0.001 Torr. A vacuum degree within a range of (0.1 Pa) or less and vacuum heating at a temperature within a range of 300 ° C. to 600 ° C. for a time within a range of 60 minutes to 420 minutes may be used.

  Furthermore, in order to achieve the above object, the method for producing a cast iron-based sintered sliding member according to the present invention comprises a 36-mesh powder obtained by mechanically pulverizing chips in the selection process of the first aspect. It can be a powder in a particle size range that passes through a sieve but does not pass through a 55 mesh sieve.

  Furthermore, in order to achieve the above object, the method for producing a cast iron-based sintered sliding member according to the present invention is characterized in that the raw material powder in the sorting step of the first gist is obtained by mechanically pulverizing chips, and 55 mesh It can be set as the powder of the particle size range which passes a sieve.

  Subsequently, in order to achieve the above object, the method for producing a cast iron-based sintered sliding member according to the present invention uses iron powder or stainless alloy powder as the mixed powder for the raw material powder in the filling step of the first aspect. It can be added in the range of 5% to 30% with respect to the weight of the raw material powder.

  Subsequently, in order to achieve the above object, the method for producing a cast iron-based sintered sliding member according to the present invention is applied to a green compact obtained after the sintering step, and 10 volume of the total volume of the green compact. % To 20% by volume or less may be used.

  Further, in order to achieve the above object, the cast iron-based sintered sliding member according to the present invention is a cast iron-based sintered sliding member obtained by the above-described method for producing a cast iron-based sintered sliding member according to the present invention. It can be a member.

  In the method for producing a cast iron-based sintered sliding member according to the present invention, chips (wet chips) obtained by using a cutting fluid are heated in the chip processing of grown gray cast iron whose base exhibits an all-ferrite structure. In the process, the degree of vacuum is in the range of 1 Torr (100 Pa) to 0.001 Torr (0.1 Pa), and the temperature is in the range of 300 ° C. to 600 ° C., and in the range of 60 minutes to 420 minutes. By vacuum heating only for a period of time, the attached cutting fluid can be decomposed and the processing distortion of the chip can be removed, so that the moldability when forming a green compact from this chip is extremely good. .

  In the method for producing a cast iron-based sintered sliding member according to the present invention, in the sintering step, the temperature is in the range of 1100 ° C. to 1150 ° C., and the time is in the range of 30 minutes to 90 minutes. By sintering the green compact, it changes to a base structure with a mixture of ferrite and pearlite, which increases the hardness of the sintering and improves the strength, so that a sintered sliding member with excellent sliding characteristics can be manufactured. . Further, since sintering is performed in a neutral atmosphere or a reducing atmosphere, there is an effect that oxidation of the sintered body can be prevented. Here, in obtaining the above-mentioned grown gray cast iron casting, the green cast iron cast is subjected to repeated heating and cooling treatment that repeatedly heats and cools between a temperature higher and lower than the A1 transformation point of the gray cast iron cast, whereby the green cast iron cast is all made. Grown gray cast iron exhibiting a ferrite structure can be easily obtained.

  Furthermore, in the method for producing a cast iron-based sintered sliding member according to the present invention, when the selected chips are loaded into a predetermined mold, the chips pass through a 36 mesh screen but do not pass through a 55 mesh screen. Alternatively, by obtaining and loading chips that pass through a 55 mesh sieve, there is also an effect that a cast iron-based sintered sliding member that exhibits a high lubricating action is manufactured.

  Furthermore, in the method for producing a cast iron-based sintered sliding member according to the present invention, when the green compact is subjected to an oil impregnation treatment after the sintering step, not only the lubricating action of graphite but also the lubricating action by the lubricating oil is added. There is also an effect that the dynamic characteristics are further improved. In this case, when the green compact is subjected to an oil impregnation treatment, the green compact is subjected to an oil impregnation treatment so that the oil content is within the range of 10% by volume or more and 20% by volume or less of the total volume of the green compact. When applied, a cast iron-based sintered sliding member having sufficient strength and appropriate lubricity is produced.

  Subsequently, in the method for producing a cast iron-based sintered sliding member according to the present invention, when the selected chips are loaded into a predetermined mold, the chips that pass through the 36 mesh screen but do not pass through the 55 mesh screen. Alternatively, a sintered compact is obtained by sintering a green compact in which iron powder or stainless alloy powder is added in an amount of 5% to 30% with respect to the weight of the raw material powder with respect to the chips passing through a 55 mesh sieve. Is changed to a material having an appropriate hardness and strength, in particular, the compatibility with the mating shaft is improved, and the sliding characteristics can be improved.

  Further, since the cast iron-based sintered sliding member manufactured by the above-described method for manufacturing a cast iron-based sintered sliding member according to the present invention has sufficient strength and sufficient lubricity, various types of sliding members can be used. Can be widely used in the field.

  Hereinafter, the best mode for carrying out the present invention will be described. First, as a problem when using wet swarf as raw material, the cutting fluid adhering to the swarf decomposes and sublimates during sintering, destroys the balance of the reducing atmosphere in the furnace, and lowers the density of the sintered body. It has been mentioned that the strength and the strength of the sintered body are reduced by adversely affecting the strength and adhering the wet graphite to free graphite powder or dust in the environment. In order to solve these problems, the present inventors proceeded with various experiments and researches, and in a vacuum furnace with a degree of vacuum within a range of 1 Torr (100 Pa) to 0.001 Torr (0.1 Pa). , By vacuum heating at a temperature in the range of 300 ° C. to 600 ° C. for a time in the range of 60 minutes to 420 minutes, the cutting fluid adhering to the wet chips is decomposed and sublimated to be removed, At the same time, it has been found that it is possible to remove adhering free graphite and dust in the environment.

  Furthermore, the present inventors have also found that the residual stress (residual strain) of chips, which was another problem, can be reduced or removed by performing the vacuum heating. Here, a high temperature is desirable for the decomposition of the cutting fluid, but it has been found that the decomposition temperature is sufficient for heating so as not to disturb the balance of the reducing atmosphere during sintering. As a result of the experiment, it was found that the conditions were satisfied if vacuum heating was performed at 300 ° C. for 420 minutes and at 600 ° C. for 60 minutes. Regarding the degree of vacuum, it was sufficient if the sublimated component could be removed, and the result was obtained that the range was from 1 Torr to 0.001 Torr.

  On the other hand, the grown gray cast iron casting contains a large amount of enlarged flake graphite, and therefore has good machinability, and it is generally easy to obtain chips having a large particle size. Depending on the case, the size was 3 to 5 mm, and it was difficult to mold with a mold as it was, so pulverization was essential. Here, in the case of the invention according to the above-mentioned Patent No. 3795391, since chips having different three kinds of particle size ranges are used at a certain ratio, sieving from the obtained chips to each particle size is performed. After that, the method of blending and mixing again was employed, but this operation was complicated and expensive. Therefore, in the present invention, a method of using only pulverized powder having a constant particle size after chip pulverization is adopted. The particle size of the pulverized powder affects the moldability of the mold and appears as a density difference of the molded body. Further, the density difference of the molded body appears as a difference in sintering strength obtained in a subsequent process, and greatly affects the load resistance of the bearing. Therefore, when the relationship between the particle size and the density of the molded body was experimentally examined, by using a chip that passes through a 36 mesh screen but does not pass through a 55 mesh screen, or a chip that passes through a 55 mesh screen. The present inventors have found that good moldability and appropriate sintering hardness can be obtained. That is, it was found that the hardness and strength of the sintered body can be greatly improved with good moldability in the case of a chip that passes through a 36 mesh screen but does not pass through a 55 mesh screen. On the other hand, in the case of chips passing through a 55 mesh sieve, it was found that the sintered body can be imparted with appropriate hardness and strength as well as good moldability. Such a difference in hardness and strength of the sintered body can improve convenience as a bearing characteristic. That is, when considering general use conditions, one can be used with a high load, and the other can be used with a light load.

  Subsequently, the flake graphite obtained by cutting the gray cast iron casting contains a large amount of flake graphite that is enlarged by the growth and is exposed. This is because there is more flake graphite that exerts a lubricating action in the chips obtained by cutting the grown gray cast iron casting compared to the chips obtained by cutting a general gray cast iron casting (FC150). Is shown. Therefore, the function as a bearing can be sufficiently achieved. However, when it is desired to reduce the friction coefficient or prevent the shaft material from being worn, it is possible to improve the material by adding iron powder or stainless alloy powder to the crushed chips. In particular, by adding the above metal powder, the base of the cast iron-based sintered sliding member can be changed from a hard pearlite structure to a pearlite structure mixed with a soft ferrite structure or a strong austenite structure. Can be systematically controlled, and the occurrence of damage to the shaft can be prevented. Here, iron powder takes in a part of graphite in cast iron and forms a solid solution of iron-carbon, increasing the strength and hardness of the substrate (matrix). However, most of them exist in the pearlite structure as pure iron (ferrite), and fulfill the effect of adjusting the hardness of the substrate. As a result of various experiments, the mixing ratio of the iron powder or the stainless alloy powder with respect to the weight of the raw material chips is not effective in adjusting the hardness when it is 5% by weight or less. It was something to lower. Furthermore, the stainless alloy powder has an effect of increasing the strength of the substrate by forming an austenite structure in the pearlite structure, but the mixing ratio is not effective in improving the strength at 5% by weight or less, but it is not effective at 30% by weight or more. The result that hardness was reduced and it did not contribute to strength improvement was obtained.

  From the various findings as described above, the method for producing a cast iron-based sintered sliding member according to the present invention cuts a gray cast iron casting in which the base exhibits an all-ferrite structure, and uses the chips obtained by the cutting. In a vacuum furnace, the degree of vacuum in the range of 1 Torr (100 Pa) to 0.001 Torr (0.1 Pa) is within the range of 60 minutes to 420 minutes at a temperature in the range of 300 ° C. to 600 ° C. Heating process for vacuum heating for a period of time, and the above-mentioned chips are pulverized mechanically and pass through a 36 mesh screen but do not pass through a 55 mesh screen, or a particle size range through a 55 mesh screen A selection process for selecting only the powder as raw material powder, and the raw material powder alone or the raw material powder with iron powder or stainless alloy powder in the range of 5% to 30% with respect to the raw material chips In addition, a filling step of filling the mixed powder into the mold and forming the green compact by compression molding the mold at a molding pressure in the range of 4 tons / square cm to 5 tons / square cm. A sintering process in which the green compact is sintered in a neutral or reducing atmosphere at a temperature in the range of 1100 ° C to 1150 ° C for a time in the range of 30 minutes to 90 minutes. From the linking step, the best mode for implementation can be constructed. Furthermore, the cast iron-based sintered sliding member according to the present invention can be a sliding member obtained by the manufacturing method based on the best mode for carrying out the above, and subsequently the total volume of the sliding member. The oil impregnation treatment may be performed in the range of 10% by volume to 20% by volume.

  Hereinafter, the present invention will be described in detail through preferred embodiments according to the present invention with reference to the tables and drawings. In addition, it cannot be mentioned that this invention is not limited only to the following Example.

  Regarding the vacuum heat treatment of wet chips, first, the wet chips obtained by cutting the gray cast iron casting were heated at a temperature of 300 ° C for 120 minutes at a vacuum of 1 Torr, 300 ° Each chip was prepared when heated at a temperature of C for 420 minutes and when heated at a temperature of 600 ° C. for a time of 60 minutes. After mechanically pulverizing these chips, they are classified into chips that pass through a 36-mesh sieve but do not pass through a 55-mesh sieve or chips that pass through a 55-mesh sieve using a sieve. The mold is filled and compression molded at molding pressures of 3 tons / square cm, 4 tons / square cm, and 5 tons / square cm to form green compacts, and the density of the green compacts is examined. It was. Since the density of the molded body has a correlation with the sintering strength, the influence on the load resistance of the bearing can be roughly determined by examining the density of the molded body. The results are shown in Table 1, and the conditions under which the target density of 6.0 or more is obtained are as follows. The molding pressure is 4 tons / square cm or more, and the temperature is in the range of 300 ° C. to 600 ° C. The result was obtained that the vacuum heating should be performed for a time within the range of 60 minutes to 420 minutes.

  Next, 3.65 wt% C, 2.22 wt% Si, 0.45 wt% Mn, 0.045 wt% P, 0.084 wt% S and the balance Fe, inner diameter 33 mm A cylindrical gray cast iron casting (FC150) having an outer diameter of 54 mm and a length of 203 mm was produced. This gray cast iron casting was subjected to repeated heating and cooling treatment (heating up and down between A1 transformation points) between a temperature higher and lower than the A1 transformation point of this gray cast iron casting. By this repeated heating and cooling treatment, “Oiles # 300 (trade name)” manufactured by Oiles Industries Co., Ltd. can be cited as an example of a gray cast iron substrate. The component composition of the above-mentioned grown gray iron casting is 3.72% C, 2.26% Si, 0.45% Mn, 0.047% P, 0.086% S. The balance was Fe.

  Subsequently, the oxidized scale formed on the surface of the above-mentioned grown gray cast iron is removed, and then roughing, thinning and finishing are performed while dripping a water-soluble cutting fluid onto this growing gray cast iron, A bearing bush having a diameter of 40 mm, an outer diameter of 50 mm, and a length of 40 mm was produced. In this way, a large amount of wet swarf was generated when the bearing gray was produced by cutting the gray cast iron casting. These large amounts of wet chips are vacuum heated at 600 ° C. for 60 minutes at a vacuum degree of 0.1 Torr. These chips were then mechanically crushed and screened into a powder that passed through a 36 mesh screen but did not pass through a 55 mesh screen. Next, this powder was filled in a mold and compression molded at a molding pressure of 5 tons / square cm to produce a green compact. Thereafter, this green compact was sintered in a hydrogen gas atmosphere at a temperature of 1130 ° C. for 60 minutes in a sintering furnace to obtain a sintered body. The sintered body was cut to produce a cylindrical sliding member having an inner diameter of 20 mm, an outer diameter of 28 mm, and a length of 15 mm.

  In the same manner as in Example 1 described above, the chips produced when machining the gray cast iron castings to produce bearing bushes are mechanically pulverized and sorted into chips that pass through a 55 mesh screen. The powder was loaded into a cylindrical mold and compression molded at a molding pressure of 5 tons / square cm to produce a green compact. Thereafter, this green compact was sintered in a hydrogen gas atmosphere at a temperature of 1130 ° C. for 60 minutes in a sintering furnace to obtain a sintered body. The sintered body was cut to produce a cylindrical sliding member having an inner diameter of 20 mm, an outer diameter of 28 mm, and a length of 15 mm.

  In the same manner as in Example 1 described above, chips generated when a gray cast iron casting was cut to produce a bearing bush were mechanically pulverized and passed through a 36 mesh screen, but a 55 mesh screen. The powder was selected so as not to pass through. This powder was mixed with 5% spray iron by weight, and the mixed powder was loaded into a cylindrical mold and compression molded at a molding pressure of 5 tons / square cm to produce a green compact. Thereafter, this green compact was sintered in a hydrogen gas atmosphere at a temperature of 1130 ° C. for 60 minutes in a sintering furnace to obtain a sintered body. The sintered body was cut to produce a cylindrical sliding member having an inner diameter of 20 mm, an outer diameter of 28 mm, and a length of 15 mm.

  In the same manner as in Example 2 described above, the chips generated when the bearing gray was produced by cutting the gray cast iron casting was mechanically crushed and selected into chips passing through a 55 mesh sieve. Add 5% by weight of sprayed iron powder to this powder and mix it. Load this mixed powder into a cylindrical mold and compress it at a molding pressure of 5 tons / square cm to make a green compact. did. Thereafter, this green compact was sintered in a hydrogen gas atmosphere at a temperature of 1130 ° C. for 60 minutes in a sintering furnace to obtain a sintered body. The sintered body was cut to produce a cylindrical sliding member having an inner diameter of 20 mm, an outer diameter of 28 mm, and a length of 15 mm.

  In the same manner as in Example 2 described above, the chips generated when the bearing gray was produced by cutting the gray cast iron casting was mechanically crushed and selected into chips passing through a 55 mesh sieve. , 30% by weight of 306 stainless steel powder is added to this powder and mixed, and this mixed powder is loaded into a cylindrical mold and compression molded at a molding pressure of 5 tons / square cm to produce a green compact. did. Thereafter, this green compact was sintered in a hydrogen gas atmosphere at a temperature of 1110 ° C. for 60 minutes in a sintering furnace to obtain a sintered body. The sintered body was cut to produce a cylindrical sliding member having an inner diameter of 20 mm, an outer diameter of 28 mm, and a length of 15 mm.

Comparative example

  On the other hand, it consists of 3.65% by weight of C, 2.22% by weight of Si, 0.45% by weight of Mn, 0.045% by weight of P, 0.084% by weight of S, and the balance of Fe. A cylindrical gray cast iron casting (FC150) having an outer diameter of 54 mm and a length of 203 mm was produced. This gray cast iron casting was subjected to repeated heating and cooling treatment (heating up and down between A1 transformation points) between a temperature higher and lower than the A1 transformation point of this gray cast iron casting. By this repeated heating and cooling treatment, “Oiles # 300 (trade name)” manufactured by Oiles Industries Co., Ltd. can be cited as an example of a gray cast iron substrate. The component composition of the above-mentioned grown gray iron casting is 3.72% C, 2.26% Si, 0.45% Mn, 0.047% P, 0.086% S. The balance was Fe.

Next, the oxidized scale formed on the surface of the above-mentioned gray cast iron casting is removed, and then the rough gray cast, thinning, and finish cutting are performed on the grown gray cast iron casting by dry cutting without using a cutting fluid. A bearing bush having an inner diameter of 40 mm, an outer diameter of 50 mm, and a length of 40 mm was produced. Chips generated during the production of the bearing bush are mechanically pulverized, and 30% by weight of the chips that pass through the 20 mesh screen but do not pass through the 36 mesh screen, and the 36 mesh screen. 60% by weight of the chips that pass through but does not pass through the 55 mesh sieve, and 10% by weight of the chips that pass through the 55 mesh sieve are collected, and after mixing these powders, this mixed powder Was loaded into a cylindrical mold and compression molded at a molding pressure of 5 tons / square cm to produce a green compact. Thereafter, this green compact was sintered in a hydrogen gas atmosphere at a temperature of 1130 ° C. for 60 minutes in a sintering furnace to obtain a sintered body. The sintered body was cut to produce a cylindrical sliding member having an inner diameter of 20 mm, an outer diameter of 28 mm, and a length of 15 mm.

  Subsequently, the composition of each chip in Example 1, Example 2, Example 3, Example 4, Example 5, and Comparative Example described above is shown in Table 2, and the physical properties of each green compact and sintered body Is shown in Table 3. The oil content in Table 3 is a value obtained by subjecting the sintered bodies produced in each Example and Comparative Example to oil treatment and measuring the oil content.

Bearing performance was tested under the test conditions shown below for the sintered sliding members obtained in Example 1, Example 2, Example 3, Example 4, Example 5, and Comparative Example. A schematic diagram of the test method is shown in FIG. Here, as shown in the figure, the mating shaft inserted into the cylindrical bearing repeatedly moves in the range of 45 ° clockwise and 45 ° counterclockwise in a total range of 90 °. The load is applied by a weight from the lower part in the vertical direction via a lever.
"Bearing performance test"
Test condition sliding speed 0.5m / min
Load (surface pressure) 200kgf / square cm
Oscillation angle -45 ° to + 45 °
Test time 20 hours Counter shaft Machine structural carbon steel (S45C) quenching material test method Radial journal swing test lubrication method Grease was applied thinly to the sliding surface at the start of the test

  FIGS. 2 and 3 show the results of the wear amount and the friction coefficient of each example from the results of the bearing swing test performed under the above-described conditions, respectively. Here, FIG. 2 shows the amount of wear in the bearing performance test of each example and comparative example, and FIG. 3 shows the change in the friction coefficient in the bearing performance test of each example and comparative example. The amount of wear in FIG. 2 indicates the amount of change when the inner diameter of a cylindrical sliding member having an inner diameter of 20 mm, an outer diameter of 28 mm, and a length of 15 mm manufactured in each example is worn by a bearing swing test. . On the other hand, as shown in FIG. 3, in the sliding member of the comparative example, the friction coefficient started to increase slightly from the time when the test time exceeded 10 hours, and showed 0.18 when the test time was 20 hours. Further, the wear amount of the comparative example in FIG. 2 was 0.0117 mm. The bearing swing test is a test method that assumes the conditions generally used for cast iron casting bearings, but the load (surface pressure) is typically 50 kgf / square cm or less. There are not many examples of use at a high load of 200 kgf / square cm, and the conditions are selected in order to draw out the difference in bearing performance between the product of the present invention and the comparative example. The comparative example functions as a bearing despite such high load conditions. On the other hand, as shown in FIG. 3, the friction coefficient of each example maintained a low coefficient of friction of 0.15 to 0.10 compared with the comparative example during the 20-hour test, and exhibited excellent performance as a bearing. Further, in the bearing wear amount in FIG. 2, 0.004 mm in Example 1, 0.0068 mm in Example 2, 0.0066 mm in Example 3, 0.0053 mm in Example 4, and 0.0026 mm in Example 5. The values are considerably smaller than 0.0117 mm in the comparative example. After the test, the surfaces of the mating shafts of Example 1, Example 2, Example 3, Example 4 and Example 5 were observed, and it was confirmed that a lubricating film of free graphite was formed on the mating shaft surface. It was. Similarly, in the observation of the counterpart shaft of the comparative example, it was confirmed that the lubricant film was partially missing and the metal surface was exposed. Such results show that in the examples, the material was homogenized by vacuum annealing of the raw material powder and had a certain particle size range, so that a certain stable structure and hardness were obtained after sintering, and the free graphite was uniform. It is inferred that it was obtained because of the dispersion.

  According to the method for producing a cast iron-based sintered sliding member according to the present invention, it is possible to reuse grown gray cast iron, which has been mostly discarded as waste, with respect to wet chips, and to have sufficient strength and appropriateness. Cast iron-based sintered sliding members with excellent lubricity can be produced in large quantities by an industrial production method, and because of their high functional properties as sliding members, they are used for various industrial machine equipment materials. The economic effect of using as is extremely high.

(Table 1) The table | surface which shows the relationship between the vacuum heating conditions and the molding pressure of the wet swarf which influence on a density.
(Table 2) The table | surface which shows the particle size and composition of the raw material powder | flour of each Example and a comparative example.
(Table 3) The table | surface which shows the density after molding of each Example and a comparative example, the density after sintering, hardness, and oil content.
The figure which shows the outline of a bearing performance test method. The graph which shows the abrasion loss in the bearing performance test of each Example and a comparative example. The graph which shows the friction coefficient in the bearing performance test of each Example and a comparative example.

Claims (7)

  Cutting the growth gray cast iron casting in which the base exhibits an all-ferrite structure, a heating process in which the chips obtained by the cutting are heated in a vacuum furnace, and the chips are pulverized to obtain only chips in a predetermined particle size range. As a raw material powder, a filling step for filling the raw material powder alone or a mixed powder obtained by adding iron powder or stainless steel alloy powder to the raw material powder, and filling the mold with 4 ton / A compression molding step in which a green compact is formed by compression molding at a molding pressure in a range of square cm to 5 ton / square cm; and then in a neutral atmosphere or a reducing atmosphere at 1100 ° C. to 1150 ° C. A method for producing a cast iron-based sintered sliding member, comprising a sintering step in which the green compact is sintered at a temperature within a range for a time within a range from 30 minutes to 90 minutes.   The heating in the heating step is performed at a temperature in a range of 300 ° C. or more and 600 ° C. or less for 60 minutes or more and 420 degrees in a vacuum degree in a range of 1 Torr (100 Pa) or more and 0.001 Torr (0.1 Pa) or less in a vacuum furnace. 2. The method for producing a cast iron-based sintered sliding member according to claim 1, wherein vacuum heating is performed for a time within a range of minutes or less.   The raw material powder in the selection step is a powder having a particle size range in which a chip is mechanically pulverized and passes through a 36-mesh sieve but does not pass through a 55-mesh sieve. Item 3. A method for producing a cast iron-based sintered sliding member according to Item 2.   3. The cast iron-based sintered slide according to claim 1, wherein the raw material powder in the sorting step is a powder in a particle size range in which a chip is mechanically pulverized and passes through a 55 mesh sieve. Manufacturing method of moving member.   The mixed powder with respect to the raw material powder in the said filling process added iron powder or stainless steel alloy powder in the range of 5% or more and 30% or less with respect to the said raw material powder weight, The Claim 1 thru | or 4 characterized by the above-mentioned. Of manufacturing a cast iron-based sintered sliding member.   6. An oil impregnation treatment is performed on the green compact obtained after the sintering step in a range of 10% by volume to 20% by volume of the total volume of the green compact. The manufacturing method of the cast iron type sintered sliding member of description.   A cast iron-based sintered sliding member produced by the method for producing a cast iron-based sintered sliding member according to any one of claims 1 to 6.

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