JP2005105370A - Method of producing rotary body provided with pressure resistant face for sliding on circumferential face, such as gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a rotary body provided with a pressure resistant face for sliding on the circumferential face such as a gear which can be recycled, to increase the density of the circumferential face, and to improve the pressure resistance in its sliding face. <P>SOLUTION: When after a lubricating layer B is beforehand formed at a through hole 1 formed with a forming part 1A of teeth T on the inner circumferential face, iron powder for powder metallurgy is stored therein as raw material powder M, and then a powder compact A is subjected to press molding, the lubricity between the forming part 1A and the raw material powder is improved, and the density of the site corresponding to the teeth of a gear in the powder compact is increased to increase its facial pressure resistance for sliding. Iron powder containing only carbon powder and Fe with inevitable impurities is used as the raw material powder M, thereby a sintered alloy is easily extracted as the metals of various single elements, so that its recycling properties can be improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a rotating body including a sliding pressure-resistant surface on a circumferential surface of a sprocket, a cam, or the like, for example, an automobile gear or a high surface pressure.

  Conventionally, a sintered sprocket made of an iron-based sintered alloy containing C, Mo, and Ni has been known as this type, and sizing after pre-sintering a powder compact as a method for producing a sintered sprocket Then, it is known that the presintered material is press-molded, sized after the main sintering, and then the density of the sprocket is increased by performing press molding and sizing twice at that time. (For example, refer to Patent Document 1).

  Further, a powder having a mixture of a lubricant having high temperature stability, graphite powder, and iron powder for powder metallurgy is heated to 100 ° C. or higher, compression-molded using a mold heated to 120 ° C. or higher, and then 1180 ° C. or higher. And the iron powder for powder metallurgy is Ni: 2.0-5.0%, Mo: 0.2-1.0%, Cu: 0.5-2.0%, balance Fe And a method for producing a sintered sprocket for silent chain, in which the iron powder is formed by diffusion bonding of metal particles of Ni, Mo, and Cu around the iron particles (see, for example, Patent Document 2). .

In addition, in order to improve the wear resistance of the tooth surface of the sprocket, as a means for improving the tooth surface density, a sprocket can be manufactured by two-time molding and two-time sintering, a sprocket can be manufactured by warm molding, After the sprocket is sintered, hot precision forging is performed in a closed mold to improve the mechanical properties, or the gear as a die meshes with the sintered metal sprocket after the sprocket is sintered. A rolling method is also known (see, for example, Patent Document 3).
JP 2002-129295 A (paragraphs 0003 and 0004) JP 2001-295915 A (paragraphs 0009, 0010) JP 2001-25838 A (paragraphs 0002, 0003)

  C, Mo, Cu, Ni and the like contained in the alloy contribute to improvement of material strength and wear resistance. By the way, in order to recycle such an alloy, it is necessary to melt the alloy and separate it into various components. However, Ni and Cu are difficult to recover, and as a result, a sintered body having such a component is recycled. There is a problem that it is difficult. On the other hand, a sintered body obtained by molding iron powder for powder metallurgy consisting only of C, the remaining Fe and inevitable impurities and then molding the powder molded body is excellent in recyclability, but has high strength and surface wear resistance. There is an inferior problem.

  And, as a means for improving the material strength and wear resistance of such recyclable metal materials, the sintering forging method and the gear rolling method are known, but the manufacturing method by such means is also possible. The former is prone to defects in the surface layer, and the latter is limited in density improvement. It is not suitable for gears, sprockets loaded with high surface pressure, and rotating bodies with a pressure-resistant surface for sliding on cams, etc. It was a thing. Further, in the method of rolling the gears after performing the press twice and sintering twice, high cost becomes a problem.

  Therefore, the present invention provides a method of manufacturing a rotating body having a sliding pressure-resistant surface on a circumferential surface of a gear or the like that can be recycled and can increase the density of the peripheral surface to improve the pressure resistance on the sliding surface. For the purpose.

  According to the first aspect of the present invention, a lubricant layer is formed in advance on the mold body in which a molded part of a sliding pressure-resistant surface is formed on the inner peripheral surface, and then C: 0.1 to 1.0% by weight and the balance as a raw material powder A method of manufacturing a rotating body having a sliding pressure-resistant surface on a circumferential surface of a gear or the like, characterized by containing iron powder consisting of only Fe and inevitable impurities and press-molding a powder molded body, and lubricating a molded part By forming the layer, when the powder molded body is molded by the molded section, the lubricity between the molded section and the iron powder for powder metallurgy is improved, and the surface density of the powder molded body can be improved. By improving the density of the surface of the powder compact, and hence the pressure-resistant surface for sliding, the surface pressure for sliding can be increased, and the sintered body can be easily recycled.

  The invention according to claim 2 is characterized in that the lubricating layer is formed by a crystallization layer in which a solution in which a lubricant is dissolved in a solvent is adhered to the molding portion and the solution is evaporated. This is a method of manufacturing a rotating body having a sliding pressure-resistant surface on the circumferential surface of a gear, etc., and a lubrication layer of a molding part can be formed into a uniform layer by a crystallization layer. For this reason, iron powder for powder metallurgy is formed in the molding part. When the powder compact is accommodated and the powder compact is molded, the density of the powder compact, and hence the pressure-resistant surface for sliding, can be made uniform. The surface pressure for sliding can be further increased by making the density of the powder compact, and thus the surface of the pressure-resistant surface for sliding uniform.

  The invention according to claim 3 is characterized in that after the sintered compact obtained by sintering the powder compact is rolled, heat treatment is further performed, and the sliding pressure-resistant surface is provided on the circumferential surface of the gear according to claim 1 or 2. This is a manufacturing method of a rotating body provided, and the peripheral surface can be formed accurately and densely by meshing the die with the peripheral surface of the sintered body. The accuracy of the sliding pressure resistant surface can be improved, and the density can be further improved to improve the sliding resistant pressure.

  According to the first aspect of the invention, by improving the density of the powder compact, and thus the surface of the sliding pressure-resistant surface, the sliding surface pressure can be increased and the sintered body can be easily recycled.

  According to the invention of claim 2, the surface pressure for sliding can be further increased by making the density of the surface of the powder compact, and thus the surface of the pressure-resistant surface for sliding uniform.

  According to the invention of claim 3, the accuracy of the sliding pressure-resistant surface can be improved, and the density can be improved to improve the sliding surface pressure.

  Preferred embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below do not limit the contents of the present invention described in the claims. In addition, all of the configurations described below are not necessarily essential requirements of the present invention. For example, the lubricating layer is not formed by a crystallization layer, but a higher fatty acid-based lubricant is applied to the molded part to form a lubricating layer, or a higher fatty acid-based lubricant dispersed in water, The lubricating layer may be formed by coating the molding part by spraying or the like and evaporating water with a heated mold body. In addition, the solution in which the lubricant is dissolved in the solvent in the embodiment may include a solution in which the lubricant is partially dissolved in the solvent. Further, before filling the raw material powder, the solution is attached to the molding part, and the solution is evaporated to form a crystallization layer in the molding part, and then a punch is fitted into the molding part to form a powder. It is not necessary to form a crystallized layer in the molded part by always attaching the solution to the molded part before filling the raw material powder and evaporating the solution. After forming the powder compact, before the third raw material powder is filled, the raw material powder is filled as it is using the first crystallization layer without adhering the solution to the molded part. Alternatively, the solution may be attached to the molding part in an intermittent manner so that the solution is adhered to the molding part and the solution is evaporated to form a second crystallization layer in the molding part.

  Embodiment 1 of the present invention will be described below with reference to the accompanying drawings. The embodiment shows the case of a gear G as a rotating body in which teeth T, which are pressure-resistant surfaces for sliding, are arranged along the outer peripheral surface of the disc-shaped main body B as shown in FIG. In addition, the concrete pressure | voltage resistant surface for sliding in the tooth | gear T is a tooth surface which the roller of a chain contacts.

  Next, the manufacturing process will be described. FIG. 1 shows a first step. In FIG. 1, reference numeral 1 denotes a through hole formed in a die 2 which is a mold body for forming a powder compact A which is a green compact, which will be described later, below the through hole 2. The lower punch 3 is fitted, and the upper punch 4 is fitted from above the one through-hole 2. And the molding part 1A is formed by the inner peripheral surface so that the tooth T is formed by the inner peripheral surface of the through hole 1. In order to form the teeth T, the forming portion 1 </ b> A is formed with irregularities in an annular shape around the axis Z of the through hole 2. Further, a feeder 5 as a raw material supply body for supplying the raw material powder M is slidably provided on the upper surface of the die 2. Further, a spray part 6 is provided above the through-hole 2 as an attaching means for spraying the lubricant solution L and depositing the solution L on the molding part 1A. The spray part 6 faces the through-hole 2. It is provided and connected to a tank (not shown) of the solution L via an automatic opening / closing valve (not shown). In addition, a heater 7 and a temperature detection unit 8 are provided around a molded part 1A of the powder molded body A formed by the through hole 1 and the lower punch 3 fitted in the through hole 1. The temperature detection unit 8 is connected to a temperature control device 9 as temperature control means, and the temperature control device 9 controls the temperature of the through hole 2 to be higher than the evaporation temperature of the solution L and lower than the melting temperature of the lubricant. It has become.

  In the first step, the peripheral surface of the molding part 1A is set higher than the evaporation temperature of the solution L and lower than the melting temperature of the lubricant by the heat of the heater 7 controlled in advance by the temperature control device 9. . Then, with the lower punch 3 fitted into the through hole 1 to form a bottomed molding space, the automatic open / close valve is opened and the lubricant solution L is heated by the heater 7 from the spray section 6. The molded part 1A of the die 2 is sprayed and attached. As a result, the solution L evaporates and dries, and crystals grow in the molded part 1A, so that the crystallization layer B of the lubricant is uniformly formed as a lubricating layer.

  Next, as shown in the second step of FIG. 2, the feeder 5 moves forward to drop the raw material powder M into the bottomed through-hole 1 and fill it. The raw material powder M is iron powder for powder metallurgy consisting of carbon C: 0.1 to 1.0% by weight indicated by reference numeral M1 and the balance of Fe and inevitable impurities indicated by M2. In addition, you may make it mix | blend a lubricant, for example, a lithium stearate, with the iron powder for powder metallurgy as needed.

  Next, as shown in the third step of FIG. 3, the die 2 is moved downward, the upper punch 4 is inserted into the through hole 1 from above, and the raw material powder M is sandwiched between the upper punch 4 and the lower punch 3. Compress. At this time, the lower punch 3 is fixed at the lower end so as not to move. And in this 3rd process, the raw material powder M which contact | connects the shaping | molding part 1A which forms the tooth | gear T of the gear G, or its vicinity is compressed by the crystallization layer B currently formed with the lubricant in the lubrication state.

  In the powder compact A thus press-molded, the die 2 is further lowered, and the upper surface of the lower punch 3 becomes substantially the same height as the upper surface of the die 2 as shown in the fourth step of FIG. Sometimes it can be taken out. Also at the time of taking out, the site | part which forms the tooth | gear T of the gear G in the powder molded object A contacts the crystallization layer B formed with the lubricant in a lubrication state. In this way, after the powder compact A is taken out, the process returns to the first step again, and after the solution L is sprayed again on the molding part 1A to form the crystallization layer B, the raw material powder M is transformed into the molding part 1A. Is to be filled.

  After forming the powder compact A in this manner, as a fifth step, the powder compact A is accommodated in a sintering furnace (not shown) and sintered in an atmospheric gas.

  Thereafter, the gear G is manufactured by performing post-processing such as polishing on the product obtained by sintering.

  In addition, the thing obtained by sintering is subjected to rolling and heat treatment in the sixth step by rolling shown in FIG. 5 as necessary. This is because the outer peripheral surface of the sintered body obtained by sintering the powder compact A in the fifth step is pressed against the concave rolling tool 11 shaped with the tooth profile of the tooth T, and the tooth profile of the rolling tool 11 is pressed. Is transferred, the density of the tooth surface of the tooth T in the gear G is improved, and the hardness of the tooth T is improved by performing heat treatment.

  The lubricant for forming the crystallization layer is a water-soluble phosphate metal salt such as dipotassium hydrogen phosphate, disodium hydrogen phosphate, tripotassium phosphate, trisodium phosphate, polyphosphoric acid. Those containing a phosphate group in the structure such as potassium, sodium polyphosphate, potassium riboflavin phosphate, sodium riboflavin phosphate and the like are preferred.

As water-soluble sulphate metal salts, potassium sulfate, sodium sulfate, potassium sulfite, sodium sulfite, potassium thiosulfate, sodium thiosulfate, potassium dodecyl sulfate, sodium dodecyl sulfate, potassium dodecylbenzene sulfate, sodium dodecylbenzene sulfate, edible Blue No. 1 (C ₃₇ H ₃₄ N ₂ Na ₂ O ₉ S ₃ ), Edible Yellow No. 5 (C ₁₆ H _lO N ₂ Na ₂ O ₇ S ₂ ), potassium ascorbate sulfate, sodium ascorbate sulfate, etc. Thus, those containing a sulfuric acid group in the structure are preferred.

  As shown in Tables 1 to 3, it is preferable that the water-soluble boric acid metal salt includes a boric acid group in the structure, such as potassium tetraborate and sodium tetraborate.

  As the water-soluble silicate metal salt, those containing a silicate group in the structure, such as potassium silicate and sodium silicate, are preferable.

  As the water-soluble tungstic acid metal salt, those containing a tungstic acid group in the structure, such as potassium tungstate and sodium tungstate, are preferable.

  As water-soluble organic acid metal salts, organic acid-based metal salts such as potassium acetate, sodium acetate, potassium benzoate, sodium benzoate, potassium ascorbate, sodium ascorbate, potassium stearate, sodium stearate, etc. Those containing groups are preferred.

  As shown in Tables 1 to 3, it is preferable that the water-soluble nitrogen acid metal salt includes a nitrogen acid group in the structure, such as potassium nitrate and sodium nitrate.

  As the water-soluble carbonate metal salt, those containing a carbonate group in the structure such as potassium carbonate, sodium carbonate, potassium hydrogen carbonate, sodium hydrogen carbonate and the like are preferable.

  One or more of these listed lubricants can be used.

  And the density | concentration of a water-soluble lubricant shall be the density | concentration more than the density | concentration formed with one molecule | numerator of the said lubricant, and less than a saturated density | concentration. Specifically, it is set to 1 PPM to a saturated concentration. This is because if the amount of lubricant adhering to the mold is less than 1 PPM, it is difficult to obtain a crystallized phase coating that can stably obtain lubricity. Above the saturation concentration, the lubricant cannot be completely dissolved and is solid. This is because when the particles are deposited and adhered by the spraying part 6, problems such as clogging of the spraying part 6 occur.

  The water to be dissolved is preferably water from which metal components such as distilled water and ion exchange water and halogen element components have been removed. Depending on the type of lubricant, it may be easily replaced with metal components in water to cause precipitation, and if a large amount of halogen components are contained, the green compact is likely to bind. This is because there may be a problem that harmful substances such as dioxin are generated during sintering.

  In addition, depending on the type of lubricant, there is a problem that microorganisms propagate and are likely to rot, and the ingredients may change or a bad odor may be generated, but the addition of a preservative can prevent the generation of microorganisms. it can. Preservatives that do not impair the lubricity such as sodium benzoate, are less harmful to the human body, and do not contain a halogen element component are preferable.

  Further, depending on the type of lubricant, there is a problem that bubbles are likely to be generated, and when the solution L is adhered to the molding part 1A, there is a possibility that bubbles are generated and the raw material powder is hardened. Generation of foam can be prevented by adding a water-soluble solvent or an antifoaming agent. Alcohols and ketones are preferably those that do not impair the lubricity of ethanol, acetone, etc., have low toxicity to the human body, and do not contain a halogen element component.

  By using a water-soluble solvent such as alcohol or ketone having a boiling point or a latent heat of evaporation lower than that of water, there is a case where it is not necessary to shorten the evaporation and drying time or to make the mold body 2 high temperature. .

  These lubricants, additives, and dissolved water contain toxic elements in trace amounts of dioxins and the like under the conditions often used in iron-based powder metallurgy that sinters in the presence of carbon components when halogen elements are included. Therefore, it is preferable not to include a halogen element.

  The temperature of the mold body 2 and the mixed raw material powder M are preferably set to a high temperature because of the effect of shortening the drying time and the effect of warm forming, but may be room temperature if there is no problem. In the case of a high temperature, it is difficult to perform stable warm molding because the raw material powder is hardened or the lubricant flows down to the bottom of the mold (molded part 1A). Therefore, it is preferable to select a lubricant that does not melt at the set temperature. However, if there is no problem, one or more of a semi-molten state, a highly viscous state, and two or more lubricant blends may be in a molten state. Conventionally used zinc stearate melts at about 120 ° C and lithium stearate melts at about 220 ° C, so it was difficult to perform stable warm molding at higher temperatures. There are many agents that do not melt at 220 ° C or higher, and some of them do not melt even when they exceed 1000 ° C, so the heat resistance temperature and raw material of the mold (molded part 1A) It is possible to perform warm molding easily and stably at a temperature as high as the oxidation temperature of the powder.

  As described above, in the embodiment, after the lubricating layer B is formed in advance in the through hole 1 in which the molded portion 1A of the tooth T is formed on the inner peripheral surface, the powder metallurgy iron powder is accommodated and the powder compact is pressed. When molding, the lubricity between the molded part 1A and the raw material powder can be improved, the density of the portion corresponding to the tooth T in the powder molded body can be increased, and the sliding surface pressure can be improved. By making the iron powder consisting of carbon powder, Fe powder and inevitable impurities as M, the sintered alloy can be easily taken out as various single element metals, and the recyclability can be improved.

  Further, the lubricating layer is formed by a crystallization layer B obtained by adhering a solution obtained by dissolving a lubricant in a solvent to the forming portion 1A and evaporating the solution, thereby lubricating the forming portion 1A for forming the teeth T. The layer can be formed into a uniform layer, and the surface pressure for sliding can be further increased by making the density of the surface of the powder compact A, and thus the tooth T uniform.

  Furthermore, after rolling the sintered body obtained by sintering the powder compact A, the metal structure of the tooth T can be made dense by further heat treatment, and the sliding surface pressure can be further improved.

  As described above, the rotating body according to the present invention can also be applied to sprockets, cams and the like to which high surface pressure is applied. In this case, the teeth and the cam surface are the pressure-resistant surfaces for sliding.

It is sectional drawing of the 1st process which shows 1st Example of this invention. It is sectional drawing of the 2nd process which shows 1st Example of this invention. It is sectional drawing of the 3rd process which shows 1st Example of this invention. It is sectional drawing of the 4th process which shows 1st Example of this invention. It is a top view of the 6th process showing the 1st example of the present invention. It is a top view of the gear which shows 1st Example of this invention.

Explanation of symbols

1A Molding part 2 Mold body
11 Rolling tool A Powder compact B Crystallized layer (lubricant layer)
M Raw material powder G Gear (Rotating body)
T teeth (sliding pressure-resistant surface)

Claims (3)

  A rotating body having a pressure-resistant surface for sliding on a circumferential surface of a gear or the like formed by sintering a powder compact after the powder powder for metallurgy is contained in a molding die body and press-molding the powder compact. In the manufacturing method, after forming a lubrication layer in advance on the mold main body in which the molded part of the pressure-resistant surface for sliding is formed on the inner peripheral surface, C: 0.1 to 1.0 wt%, Fe and A method for producing a rotating body comprising a sliding pressure-resistant surface on a circumferential surface of a gear or the like, wherein iron powder comprising only inevitable impurities is accommodated and the powder compact is pressure-molded.   The sliding surface on the circumferential surface of the gear according to claim 1, wherein the lubricating layer is formed by a crystallization layer obtained by adhering a solution obtained by dissolving a lubricant in a solvent to the molding portion and evaporating the solution. A method of manufacturing a rotating body having a pressure-resistant surface. 3. The method of manufacturing a rotating body having a sliding surface with a pressure-resistant surface on a gear or the like according to claim 1, wherein the sintered body obtained by sintering the powder compact is rolled and then further heat-treated. .

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