WO2012077750A1 - Method for manufacturing high-strength sinter-molded compact, and device for manufacturing same - Google Patents

Abstract

A method for manufacturing a high-strength sinter-molded compact by means of a pressure molding step and a sinter molding step, wherein the pressure molding step comprises a first pressure molding step and a second pressure molding step, with a heating/temperature-raising step therebetween. In the first pressure molding step, a first pressing force is applied to a mixed powder at room temperature, which is less than the melting point of a lubricant powder, in a first mold to form a primary green molded compact. In the heating/temperature-raising step, the primary green molded compact is heated to raise the temperature of the compact to a temperature equivalent to the melting point thereof. In the second pressure molding step, a second pressing force is applied to the primary green molded compact at the temperature equivalent to the melting point in a second mold that has been warmed to the temperature equivalent to the melting point in order to form a secondary green molded compact having an increased density.

Description

Manufacturing method and manufacturing apparatus for high-strength sintered compact

A high-strength sintered compact that produces a compacted compact with high density by pressing the mixed powder twice to form a compact compact with high density and subjecting this compacted compact to sintering treatment The present invention relates to a manufacturing method and a manufacturing apparatus thereof.

In general, in the powder metallurgy technology, a metal powder is pressed (compressed) to form a green compact having a predetermined shape, and then the green compact is heated to a temperature close to the melting point of the metal powder. It is a series of techniques for performing a sintering process to promote bonding (solidification). As a result, a sintered compact (such as a machine part) having a complicated shape and high dimensional accuracy can be manufactured at low cost.

Also, with the request for further reduction in size and weight of mechanical parts, it is required to improve the mechanical strength of the green compact. The mechanical strength is said to increase significantly (hyperbolic) as the density of the green compact is increased. As a typical method for increasing the strength, a method of pressure forming by reducing the frictional resistance by mixing a lubricant with metal powder is proposed (for example, Patent Document 1: Japanese Patent Laid-Open No. 1-219101). Has been. Many proposals aiming at higher density have been made. These proposals can be broadly divided into improvements in the lubricant itself and improvements in processes related to pressure forming and sintering.

The former belongs to a proposal that a lubricant is a carbon molecule composite in which ball-like carbon molecules and plate-like carbon molecules are combined (Patent Document 2: JP-A-2009-280908), and the penetration at 25 ° C. A proposal for a lubricant having a thickness of 0.3 to 10 mm (Patent Document 3: JP 2010-37632 A) can be mentioned. Both are ideas for reducing the frictional resistance between the metal powder and the mold.

The latter belongs to the warm forming / sintered powder metallurgy method (Patent Document 4: Japanese Patent Laid-Open No. 2-156002), the two-time press-2 times sintered powder metallurgy method (Patent Document 5: Japanese Patent Laid-Open No. Hei 4-). No. 231404) and a one-time molding-sintered powder metallurgy method (Patent Document 6: Japanese Patent Laid-Open No. 2001-181701) are known.

The first warm forming / sintering powder metallurgy method is to preheat a metal powder mixed with a solid lubricant and a liquid lubricant to melt part (or all) of the lubricant and to apply the lubricant between the particles. Disperse. Thus, the moldability is improved by reducing the frictional resistance between the particles and between the particles and the mold. In the double press-twice sintered powder metallurgy method, an iron powder mixture containing an alloying component is pressed in a die (die) to produce a green compact, and this compact is then heated to 870 ° C. Pre-sintered for 5 minutes to produce a pre-sintered body, pressurizing this pre-sintered body to produce a pre-sintered body that has been pressed twice, and then pre-sintered twice. This is a method for producing a sintered part by sintering a body at 1000 ° C. for 5 minutes. In the last one-time molding-sintered powder metallurgy method, the mold is pre-heated and the lubricant is charged and adhered to the inner surface, and then the iron-based powder mixture (iron-based powder + lubricated) heated in the mold. Agent powder), press-molded at a predetermined temperature to form an iron-based powder molded body, then subject the iron-based powder molded body to sintering treatment, further bright quenching, and then tempering treatment. This is a method for producing an iron-based sintered body.

As described above, any conventional improvement measures relating to the lubricant and the pressure molding / sintering process are likely to be complicated and expensive. Handling is also cumbersome. Moreover, even if such a great disadvantage is perceived, the density of the green compact is at most about 7.4 g / cm ³ (94% of the true density). In addition, if there is a residue generated due to the combustion of the lubricant, the quality of the compacted body that has been press-molded is degraded. Therefore, the actual manufacturing density is 7.3 g / cm ³ or less. That is, the mechanical strength is insufficient.

In particular, considering the production of magnetic cores (magnetic cores) for electromagnetic equipment (motors, transformers, etc.) from powder compacts, it is pointed out that this density (7.3 g / cm ³ or less) is extremely unsatisfactory Is strong. Decreasing loss (iron loss, hysteris loss) and increasing magnetic flux density requires higher density of the green compact, for example, announced at the Fall Meeting of the Powder and Powder Metallurgy Association in 2009 It is clear from the materials (provided by Toyota Central Research Institute).

Incidentally, regarding the production of a compact for a magnetic core, a two-time molding-one-time sintering (one-time annealing) powder metallurgy method (Patent Document 7: JP-A-2002-343657) has been proposed. In this proposed powder metallurgy method, a magnetic powder whose surface is coated with a coating containing a silicone resin and a pigment is preformed to form a preform, and the preform is subjected to heat treatment at a temperature of 500 ° C. or more. The heat-treated body is then subjected to compression molding. If the temperature for the heat treatment is 500 ° C. or lower, fracture is likely to occur during the subsequent compression molding, and if it is 1000 ° C. or higher, the insulating coating is decomposed and the insulating properties are burned out. This high temperature treatment is performed in vacuum, in an inert gas atmosphere or in a reducing gas atmosphere from the viewpoint of preventing oxidation of the preform. Therefore, it is more complicated and individualized than other proposed methods, and it is difficult to implement and implement, resulting in a significant increase in manufacturing cost. Not suitable for mass production.

By the way, none of the above proposed methods / apparatuses (Patent Documents 1 to 7) can meet the industry's request to reliably manufacture a sintered compact with high mechanical strength at low cost. In addition, the mechanical strength depends on the final sintering process, but there are many ideas. Although there is a description that can be implemented for annealing treatment and sintering treatment in a high temperature atmosphere, details regarding the pressure forming process are not clear, and the specifications / functions of the pressure forming machine, the relationship between pressure and density It is clear from the fact that there is no description of new improvements in the analysis on the limits.

Here, the development of a method / apparatus capable of producing a high-strength sintered molded body reliably, stably and at low cost is also urgently required from the viewpoint that one level of mechanical strength accompanying the reduction in size and weight is required.

An object of the present invention is to provide a method for producing a high-strength sintered molded body and a production apparatus therefor, which can reliably and stably produce a sintered molded body having high mechanical strength at low cost.

Conventionally, the pressure molding process establishes a mixed powder as a specific form, and is considered as a pre-stage (preliminary) mechanical process of the high-temperature sintering process and has been treated as such. In other words, it is considered that the increase in strength was left to the final sintering process.

However, if the density of the green compact can be greatly increased by devising the pressure molding process, which was considered to be the previous (preliminary) mechanical process, the subsequent sintering process should be kept as before. However, as a result, the mechanical strength of the sintered compact should be greatly increased.

The present invention relates to the effectiveness of the lubricant during pressurization, the compression limit including the lubricant powder, the spatial occupancy in the mixed powder of the lubricant powder, the spatial arrangement state of the base metal powder and the lubricant powder, Research on their behavior, residual state of residue (solidified particles of lubricant), partial diffusion of metal particles with vaporization of lubricant and final disposal of lubricant, and general pressure molding machine It was created based on the analysis of the properties, the compression limit and the influence on the density (strength) of the green compact.

Specifically, according to the conventional method, as shown in FIGS. 8A and 8B, a large amount of unnecessary substances (residues) 108 or large holes 109 remain in the green compact 115. In this state, it was found that the density (strength) of the green compact cannot be increased beyond a certain level even if the applied pressure is remarkably or infinitely increased. In the present invention, the density of the green compact is increased while eliminating this cause, and the strength is increased by sintering using this as a foundation, and as a result, the strength of the final sintered compact is greatly increased.

In the present invention, the primary compacted body is molded by the first pressurization while maintaining the powder state of the lubricant, and then the lubricant is heated and liquefied, whereby the lubrication aspect in the primary compacted body is changed. The secondary compacted body is made by modifying the primary compacted body by applying a second pressurization to increase the density, and then the secondary compacted body is sintered to obtain high strength. The sintered compact is molded. In other words, in the pressure molding that was the previous stage (preliminary) mechanical treatment, by actively and marginally increasing the density of the green compact that is the basis for densification by the sintering treatment As a result, the present invention provides an epoch-making method and apparatus capable of reliably and stably producing a high-strength sintered compact at a low cost.

(1) A method for producing a high-strength sintered compact according to an embodiment of the present invention is a pressure molding process in which a powder compact is formed by pressurizing a mixed powder that is a mixture of a base metal powder and a lubricant powder. And a sintering forming step of forming a sintered compact having high mechanical strength by sintering the green compact, and a first pressure forming step in which the pressure forming step sandwiches the heating temperature raising step, The first pressure forming step applies a first pressure to the mixed powder at a room temperature below the melting point of the lubricant powder in the first mold, and the first pressure forming step applies the primary pressure. The powder compact is to be molded, and the heating temperature raising step is to heat the primary powder compact to raise the temperature of the primary powder compact to the melting point equivalent temperature of the lubricant powder, In the second mold in which the second pressure forming step is warmed up to the temperature corresponding to the melting point of the lubricant powder, and at the temperature corresponding to the melting point, the primary It is intended to mold the secondary green compact densified by a second pressing force added to the powder molded body, characterized in that.

(2) In the method for producing a high-strength sintered compact, the melting point of the lubricant powder can be set to a low melting point within the temperature range of 90 to 190 ° C.

(3) In the method for producing a high-strength sintered compact, 0.03 to 0.10% by weight of zinc stearate powder as the lubricant powder is mixed with pure iron powder as the mixed metal powder as the base metal powder. The first pressing force is selected to be capable of compressing the density of the primary green compact to 7.0 to 7.5 g / cm ³ , and the second pressing force is selected to be the secondary pressing force. It can be selected that the density of the green compact can be compressed to 7.75 g / cm ³ .

(4) In the method for producing a high-strength sintered compact, 0.03 to 0.10% by weight of zinc stearate powder as the lubricant powder is added to the Fe—Si alloy powder where the mixed powder is the base metal powder. And the first pressing force is selected to be capable of compressing the density of the primary compact to a true density ratio of 70 to 85%, and the second pressing force is selected to be the secondary pressure. It can be selected that the density of the powder compact can be compressed to a true density ratio of 85 to 95%.

(5) In the method for producing a high-strength sintered compact, the second pressure can be made equal to the first pressure.

(6) An apparatus for producing a high-strength sintered compact according to an embodiment of the present invention includes a mixed powder feeder capable of supplying and filling a mixed powder, which is a mixture of a base metal powder and a low melting point lubricant powder, to the outside. A first pressure molding machine for forming a primary powder compact by applying a first pressing force to the mixed powder filled in the first mold using the mixed powder feeder; A heating temperature-raising machine for raising the temperature of the primary green compact taken out from the mold to a temperature corresponding to the melting point of the lubricant powder, and a second mold that can be warmed up to the temperature corresponding to the melting point in advance. And forming a secondary compact formed by increasing the density by applying a second pressurizing force to the primary compact that has been warmed up and set in the second mold that has been warmed up. 2 and a sintering machine for producing a sintered compact in which the secondary green compact is subjected to a sintering treatment to increase the mechanical strength.

(7) In the manufacturing apparatus for the high-strength sintered compact, the heating temperature raising machine and the second pressure molding machine are formed from a heating and pressure molding machine in which these functions are integrated, and heating is applied. It is possible to form the pressure forming machine from a plurality of heat-pressure forming child machines and to form each heat-pressure forming child machine so that it can be selected and operated for each cycle.

According to the embodiment of (1) above, a high-strength sintered compact can be reliably and stably manufactured, and the manufacturing cost can be greatly reduced.

According to the embodiment of (2) above, it is possible to ensure a sufficient lubricating action of the lubricant during the first pressurizing step. Moreover, the selectivity for the type of lubricant is wide.

According to the embodiments of (3) and (4) above, it is possible to efficiently produce a sintered molded body having high mechanical strength as compared with a sintered molded body by a conventional molding method.

According to the embodiment of (5) above, the equipment economy of the pressure molding machine can be reduced, and the pressure molding process can be easily performed and handled. Indirectly, the production cost of the green compact can be further reduced.

According to the embodiment of the above (6), the manufacturing method of the high-strength sintered molded body according to the above (1) to (5) can be surely carried out, and it is easy to implement and easy to handle.

According to the above embodiment (7), the apparatus can be simplified as compared with the above embodiment (6). Simplification of the production line can be promoted and handling becomes easier. In addition, it is possible to match the tact times of the first process forming step, the heating temperature raising step, and the second pressure forming step.

FIG. 1 is a diagram for explaining a method for producing a high-strength sintered compact according to an embodiment of the present invention. FIG. 2 is a front view for explaining an apparatus for manufacturing a high-density sintered compact and its operation according to the first embodiment of the present invention. FIG. 3A is a view for explaining a molding operation of the mixed powder in the manufacturing apparatus of the high-density sintered compact according to the first embodiment of the present invention, and is a primary compacted compact with a first mold. The state which is shape | molding is shown. FIG. 3B is a view for explaining the molding operation of the mixed powder in the high density sintered compact manufacturing apparatus according to the first embodiment of the present invention, and the next mixed powder is put in the first mold. The state of filling is shown. FIG. 4 is a graph for explaining the relationship between the applied pressure and the density obtained by the applied pressure in the high-density sintered compact manufacturing apparatus according to the first embodiment of the present invention. The solid line B shows the molding state of the second mold, and the solid line B shows the molding state of the second mold. FIG. 5 is an enlarged partial cross-sectional view for explaining the internal state of the cross section of the secondary green compact in the high density sintered compact manufacturing apparatus according to the first embodiment of the present invention. FIG. 6A is a view for explaining a ring-shaped sintered compact (and a secondary compacted compact, a primary compacted compact) in the high-density sintered compact manufacturing apparatus according to the first embodiment of the present invention. It is an external perspective view. FIG. 6B illustrates the elongated round shaft-shaped sintered compact (and the secondary compacted compact, the primary compacted compact) in the high-density sintered compact manufacturing apparatus according to the first embodiment of the present invention. FIG. FIG. 7: is a front view for demonstrating the manufacturing apparatus and operation | movement of the high intensity | strength sintered compact which concern on the 2nd Embodiment of this invention. FIG. 8A is an enlarged partial cross-sectional view for explaining the internal state of the cross section of the pre-compacted compact after the heat treatment according to the conventional method and the problems thereof, and shows the case where the heat treatment is performed at 500 to 700 ° C. FIG. 8B is an enlarged partial cross-sectional view for explaining the internal state of the cross section of the pre-compacted compact after the heat treatment according to the conventional method and the problems thereof, and shows a case where the heat treatment is performed at 700 to 1000 ° C.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

(First embodiment)
As shown in FIGS. 1 to 6B, the high-strength sintered compact manufacturing apparatus 1 includes a mixed powder feeder 10, a first pressure molding machine 20, a heating temperature riser 30, and a second pressure molding machine 40. And a sintering machine 80, and a pressure forming step for pressing the mixed powder 100, which is a mixture of the base metal powder and the lubricant powder, to form the green compacts 110 and 115, and the green compact 115. The method for producing a high-strength sintered compact including a sintering process for forming a sintered compact 120 having a high mechanical strength by sintering can be stably and reliably performed.

The technical characteristics of the manufacturing method of the present high-strength sintered compact include the first pressure molding step (PR2) and the second pressure molding step in which the pressure molding step sandwiches the heating temperature raising step (PR3 in FIG. 1). (PR5) and the first pressure molding step (PR2) is performed in the first mold (lower die 21) in the first mixed powder 100 at room temperature below the melting point of the lubricant powder. The primary compacting body 110 can be molded by applying the pressure P1, and the heating temperature raising step (PR3) heats the primary compacting body 110 and raises the temperature to the melting point equivalent temperature of the lubricant powder. In the second mold (lower mold 41) in which the second pressure forming step (PR5) is warmed up to the melting point equivalent temperature of the lubricant powder, and the primary compaction is performed at the melting point equivalent temperature. It is possible to mold the secondary compacted compact 115 in which the density is increased by applying the second pressure P2 to the compact 110. That is that.

As an overall flow in this embodiment, as shown in FIG. 1, a mixed powder filling step (PR1) for filling the first mold with the mixed powder 100 prepared in the preparation step (PR0), primary compaction molding Step (PR2): A heating temperature raising step (PR3) for actively raising the temperature of the primary compacted green body 110 to a temperature corresponding to the melting point of the lubricant powder; Step (PR4) for setting in mold 2 and secondary compacting step (PR5) and sintering treatment for forming high strength sintered compact 120 by subjecting secondary compacted compact 115 to sintering treatment Steps (PR6) are performed in this order.

The mixed powder 100 in the present specification means a mixture of a base metal powder and a low melting point lubricant powder. In addition, as the base metal powder, there are a case where it consists of only one kind of main metal powder and a case where it consists of one kind of main metal powder and one or a plurality of alloying component powders. The case can be adapted. The low melting point means that the temperature (melting point) is significantly lower than the melting point (temperature) of the base metal powder and is a temperature (temperature) at which oxidation of the base metal powder can be significantly suppressed. . Specific details will be described later.

In FIG. 2 which shows the manufacturing apparatus 1 of a high-strength sintered compact, the mixed powder supply machine 10 arranged on the leftmost side (upstream side) of the high-strength molding line converts the mixed powder 100 into the first pressure molding machine 20. Is a means for filling the first mold (lower mold 21) constituting a part of the first mold. It has a function of holding a fixed amount of mixed powder 100 and a function of supplying a fixed amount, and as a whole, an initial position (position indicated by a solid line in FIGS. 2, 3A, and 3B) and a first mold (lower mold 21). It can selectively reciprocate between the upper position (the position indicated by the broken line in FIGS. 3A and 3B).

Since it is important to uniformly and sufficiently fill the mixed powder 100 anywhere in the first mold (lower mold 21), the mixed powder 100 must be in a smooth state. That is, since the form of the internal space (cavity) of the first mold (lower mold 21) is a form according to the product form, even if the product form is complicated or has a narrow portion, the primary pressure In order to guarantee the dimensional accuracy of the powder molded body 110, non-uniform filling and insufficient filling are not allowed.

The primary green compact 110 (secondary green compact 115) in this embodiment has the ring shape shown in FIG. 6A, and the form of the internal space (cavity) 22 of the first mold corresponds to this. It is finished in the form to do.

Here, the lubricant for reducing the frictional resistance between the particles of the base metal powder and the frictional resistance between the base metal powder and the inner surface of the mold is a solid (very small granular) in a smooth state at room temperature. Choose one. For example, when a liquid lubricant is used, the mixed powder 100 has a high viscosity and low fluidity, so uniform filling and sufficient filling cannot be performed.

Next, during the molding of the primary compact 110, which is performed in the first mold (21) at normal temperature and while applying the first pressure P1, the lubricant is solid and has a predetermined lubricating action. It must be stable. Even if there is a case where a slight temperature increase may occur due to the pressurization of the first pressurizing force P1, it should be kept stable as well.

On the other hand, the melting point of the lubricant powder is set to the melting point of the base metal powder from the viewpoint of the relationship with the heating temperature raising step (PR3) executed after the molding of the primary compact 110 and the oxidation suppression of the base metal powder. In comparison, it is necessary to have a very low melting point (low melting point).

In this embodiment, the melting point of the lubricant powder is selected as a low melting point belonging to a temperature range of 90 to 190 ° C. The lower temperature (90 ° C.) is an upper limit temperature (80 ° C.) of a value (70 to 80 ° C.) that will not reach this temperature even if a certain temperature rise occurs during the molding of the primary green compact. ) With a margin (90 ° C.), and further, the melting point (eg, 110 ° C.) of another metal soap is selected. That is, the concern that the lubricating oil powder is dissolved (liquefied) and flows out during the pressure molding of the primary compacted body is eliminated.

The upper temperature (190 ° C.) is a minimum value from the viewpoint of expanding selectivity with respect to the type of lubricant powder, and in particular, a maximum value from the viewpoint of suppressing oxidation of the base metal powder during the heating temperature raising step (PR3). Selected. That is, the lower temperature and the upper temperature in this temperature range (90 to 190 ° C.) should be understood as boundary values rather than limit values.

Thus, many substances belonging to the metal soap (such as zinc stearate and magnesium stearate) can be selectively employed as the lubricant powder. Since the lubricant must be in a powder state, a viscous liquid such as zinc octylate cannot be used.

In this embodiment, zinc stearate powder having a melting point of 120 ° C. was used as the lubricant powder. In the present invention, as in the invention of Patent Document 6, a pressure molding is performed while using a lubricant having a temperature (melting point) lower than the mold temperature at the time of pressure molding and dissolving (liquefying) the lubricant from the beginning. The idea of performing is denied. If the dissolved lubricant flows out before the molding of the primary green compact 110, the insufficiently lubricated part is likely to occur on the way, so that sufficient pressure molding cannot be performed reliably and stably. It is.

Also, the amount of lubricant powder shall be a value selected from empirical rules through test studies (0.02 to 0.12% by weight of the total amount of mixed powder). Preferably, it is 0.03 to 0.10% by weight. 0.03% by weight is a value that can ensure the best lubricating action until the molding of the primary compact 110, and 0.10% by weight is expected when the mixed powder 100 is changed to the primary compact 110. This is the best value to obtain the compression ratio. Each example described below was carried out using these values.

The first pressure molding machine 20 uses the mixed powder feeder 10 to apply the first pressure P1 to the mixed powder 100 filled in the first mold 21 to form the primary compact 110. In this embodiment, it is a press machine structure.

In FIG. 2, the mold is composed of a lower mold 21 on the bolster side and an upper mold 25 on the slide 5 side. The cavity 22 of the lower mold 21 has a shape (annular cylindrical shape) corresponding to the form (ring shape) of the primary compact 110. The upper mold 25 can be pushed into the lower mold 21 (22) and is moved up and down by the slide 5. A movable member 23 is fitted below the cavity 22 so as to be displaced in the vertical direction.

The movable member 23 is displaced upward by a knockout pin (not shown) protruding through a through hole 24 provided below the ground level GL. That is, the primary compacting body 110 in the mold [21 (22)] can be pushed up to the transfer level HL. When viewed from the outside, the first compacting body 110 in the mold [21 (22)] serves as a first take-out means for taking out to the outside (HL). After the primary green compact 110 is transferred to the heating warmer 30 side, the movable member 23 returns to the initial position together with the knockout pin. But you may form the 1st extraction means from other special means.

The relationship between the pressure P (first pressure P1) in the first pressure molding machine 20 and the density ρ of the primary green compact 110 obtained correspondingly will be described with reference to FIG. To do. The horizontal axis indicates the applied pressure P as an index. The maximum capacity (pressing force P) in this embodiment is 10 Ton / cm ^2, and this is taken as 100 on the horizontal axis. Pb is a mold breakage pressure and has a horizontal axis index of 140 (14 Ton / cm ² ). The vertical axis indicates the density ρ as an index. The vertical axis index (100) is the density ρ (7.6 g / cm ³ ).

Incidentally, the vertical axis index 102 corresponds to the density ρ (7.75 g / cm ³ ). The density ρ (7.0 g / cm ³ , 7.5 g / cm ³ ) corresponds to the vertical axis index (92, 98).

When the first pressure P1 is increased, the density ρ obtained by the first pressure molding machine 20 increases according to the curve indicated by the broken line A. The density ρ is 7.6 g / cm ^{3 at} the first pressure P1 (the horizontal axis index is 100). Even if the first pressure P1 is increased to a value higher than this, the increase in the density ρ is minimal. Strong risk of mold damage.

In the conventional method, if the density ρ obtained by pressing with the maximum capacity of the press molding machine (press machine) cannot be satisfied, a larger press machine must be equipped. However, even if the maximum capacity is increased to, for example, 1.5 times, the increase in the density ρ is slight. Thus, it was the actual situation that compromised with a low density ρ (for example, 7.5 g / cm ³ ) which is currently available with a press machine.

Here, currently used as it is press machine, if the longitudinal axis index 100 (7.6g / cm ³⁾ to be increased to 102 (7.75g / cm ^3), it can be understood to be a breakthrough. That is, if the density ρ can be improved by 2%, the mechanical strength can be greatly improved.

In order to realize the above, the primary compacting body 110 molded by the first press molding machine 20 is heated to promote dissolution (liquefaction) of the lubricant, and then the second press molding machine. At 40, the second pressure forming process is performed. When the primary compacting body 110 is pressurized in the second pressure molding machine 40, a high density (7.75 g / cm ³ ) corresponding to the vertical axis index 102 is achieved as shown by a solid line B in FIG. it can. Details will be added in the description of the second pressure molding machine 40.

The heating temperature increasing device 30 heats the primary compacting body 110 taken out from the first mold 21 to positively adjust the temperature of the primary compacting body 110 to the temperature corresponding to the melting point of the lubricant powder. It is a means to raise the temperature. In FIG. 2, the heating warmer 30 includes a hot air generating source (not shown), a blowing hood 31, an exhaust circulation hood 33, and the like, and the primary compacting body 110 positioned on the wire mesh holding member 32 is heated. Air is blown and heated, and the temperature is raised to the melting point equivalent temperature (120 ° C.) of the lubricant powder. In each of the following examples, the melting point of zinc stearate is 120 ° C.

The technical significance of this low-temperature heat treatment will be described in relation to the first pressure molding treatment. When the mixed powder 100 filled in the lower mold 21 (22) is observed, the presence of the lubricant powder is relatively dense and dense in relation to the base metal powder. Part (dense part) is recognized. In the dense portion, the frictional resistance between the particles of the base metal powder and the frictional resistance between the base metal powder and the inner surface of the mold are small. The sparse part should increase the frictional resistance.

During the pressurization with the first pressure molding machine 20, the dense portion has low friction, so the compressibility is superior and the compression is likely to proceed. Since the sparse part has high friction, the compressibility is inferior and the compression is delayed. In any case, a compression progression difficulty phenomenon occurs in accordance with a preset value of the first pressure P1. That is, a compression limit occurs. Under this condition, when the fracture surface of the primary green compact 110 taken out from the mold 21 is enlarged and observed, the base metal powder is pressed in an integral manner in the dense portion. However, lubricant powder is also mixed in. In the sparse part, a slight gap (hole) remains between the pressed base metal powders. Almost no lubricant powder is found.

Thus, if the lubricant powder is removed from the dense part, a compressible gap is created. If the lubricant can be replenished in the gaps between the sparse parts, the compressibility of those parts should be improved.

That is, the primary powder compact 110 after the completion of the first pressure molding is heated to a temperature corresponding to the melting point of the lubricant powder (120 ° C.) to dissolve (liquefy) the lubricant powder. Increase fluidity. The lubricant that has melted out from the dense part soaks into the periphery and is replenished to the part that has been sparse. Therefore, the frictional resistance between the particles of the base metal powder can be reduced, and the pores occupied by the lubricant powder can also be compressed. The frictional resistance between the base metal powder particles and the inner surface of the mold can also be reduced.

It should be noted that the technical idea of the present invention is completely different from conventional methods (for example, Patent Document 5 and Patent Document 7).

In the conventional method in which compacting is considered as a mere preliminary (pre-stage) process for sintering, a preform (corresponding to the primary compact 110) is heat-treated (strained) in a high-temperature atmosphere (500 to 1000 ° C). To be removed). Indeed, this conventional heat treatment is presumed to be the source of the deterioration of quality and the prevention of strength improvement of the green compact.

According to the test study, the lubricant melts when the green compact is heat-treated in the low temperature range (500-700 ° C) related to the above-mentioned 500-1000 ° C. Thereafter, when the temperature is returned to room temperature, the lubricant is solidified to bond the metal particles. As a result, as shown in FIG. 8A, a large amount of solidified particles of the lubricant (unnecessary material 108) remain in the voids and in the gaps between the metal particles (101) in the green compact.

One heat treatment in the high temperature range (700 to 1000 ° C.) undergoes a process of melting and vaporizing the lubricant as the temperature increases. For this reason, the decomposition and solidification content (108) tends to decrease, but this time, diffusion starts at the contact surface between the metal particles (101), and sintering partially proceeds at some grain boundaries. For example, in the case of iron powder, partial diffusion at the contact surface between metal particles begins at 750 to 760 ° C. That is, when heat treatment is performed at such a high temperature, as shown in FIG. 8B, the portion where the lubricant is vaporized remains as the pores 109, and a partial diffusion bonding portion (partial sintering) 128 is partially formed between the metal powders. Will exist.

Thus, when the compacted compact after heat treatment is compressed again (room temperature pressurization process), in the low temperature range, the internal residue cannot be discharged outside the compact, and the waste (residue) Etc.) 108 remains in the green compact (FIG. 8A). In the case of the high temperature side range, although there are fewer unnecessary materials (residues, etc.) 108 compared to the case of the low temperature side range, there are partial sintering points 128 at the metal grain boundaries (FIG. 8B). It is a process of increasing the density by breaking and reducing the holes 109. When partial sintering (128) occurs, the pressure molding pressure at the second time becomes very high, and there is a limit to improving the density of the green compact from the limit on the strength of the mold. As a result, when heat-treated in a high temperature atmosphere (500 to 1000 ° C.), the molded body after the second pressure molding is very brittle and has low mechanical strength. In addition, it is very disadvantageous in terms of equipment economy that a pressurizing pressure for the second time must be increased because a press machine and a high-pressure mold having a high pressurizing capacity are required.

However, in the case of the present invention, the second compacting process is performed on the compacted article 110 in which the compacted compact is heated to the melting point of the lubricant and the temperature is maintained. Inside the green compact 110 maintained at this temperature, carbonization does not occur, and the lubricant is in a meltable and flowable state. In this state, when a pressure molding process such as a press machine is performed, the melted lubricant present inside is squeezed out and flows out from the green compact 110 to the outside. As a result, as shown in FIG. 5, almost no unnecessary matter (residue or the like) 108 remains inside the green compact (secondary green compact 115) after completion of the press molding process. That is, it is possible to mold the green compact 115 having extremely high density and high mechanical strength.

The second pressure molding machine 40 for executing this second compacting process has a second mold 41 that can be warmed up to the temperature corresponding to the melting point in advance, and the second mold that has been warmed up. This is a means for forming a secondary compacted green body 115 having a high density by applying a second pressure P2 to the heated primary compacted compact 110 set in the mold 41.

Note that the maximum capacity (pressing force P) of the second pressure molding machine 40 in this embodiment is 10 Ton / cm ² as in the case of the first pressure molding machine 20. Thus, the first pressure molding machine 20 and the second pressure molding machine 40 are configured as one press machine, and the upper molds 25 and 45 can be moved up and down synchronously by the common slide 5 shown in FIG. Also from this point, the apparatus economy is advantageous, and the molding cost of the secondary green compact 115 can be reduced.

In addition, the value of the 2nd applied pressure P2 should just be more than the value of the 1st applied pressure. For example, the first pressure molding machine 20 and the second pressure molding machine 40 are constituted by two press machines, and the maximum capacity (pressure P) of the second pressure molding machine 40 and the first The maximum capacity (pressure P) of the pressure molding machine 20 may be different.

In FIG. 2, the mold is composed of a lower die 41 on the bolster side and an upper die 45 on the slide 5 side. The cavity 42 of the lower mold 41 has a shape (annular cylindrical shape) corresponding to the shape (ring shape) of the pressure molded body 115 at the lower part, and the upper part is slightly so as to receive the primary compacted body 110. It has a large form. The upper mold 45 can be pushed into the lower mold 41 (42) and is moved up and down by the slide 5. A movable member 43 is fitted below the cavity 42 so as to be displaceable in the vertical direction. The metal mold (41) and the metal mold (21) have been adjusted in height (position) corresponding to the vertical dimension difference between the objects to be compressed (110 and 115).

The movable member 43 is displaced upward by a knockout pin (not shown) that protrudes through a through hole 44 provided below the ground level GL. That is, the secondary compacting body 115 in the second mold [41 (42)] can be pushed up to the transfer level HL. When viewed from the outside, the second compacting body 115 in the mold [41 (42)] serves as a second take-out means for taking out to the outside (HL). Note that the second take-out means may be formed from other special means. After the secondary green compact 115 is discharged to the discharge shooter 59 and receives a new primary green compact 110 from the heating warmer 30, the movable member 43 returns to the initial position together with the knockout pin.

The second mold [41 (42)] is provided with a warm-up means 47 capable of changing the set temperature. The warming-up means 47 allows the second mold [41 (42) to reach the melting point equivalent temperature (120 ° C.) of the lubricant powder (zinc stearate) until the primary compact 110 is received (set). )] Warms up (warms up). The heated primary compact 110 can be received without being cooled. As a result, the lubricating action can be ensured while preventing re-solidification of the previously dissolved (liquefied) lubricant.

In this sense, the warm-up means 47 can be heated until the secondary compacted body 115 is completely pressed. In this way, the fluidity of the dissolved lubricant in all directions during pressure molding can be further improved, so that the frictional resistance between the particles and the mold 41 (42) as well as between the particles is greatly increased. Can be reduced and maintained.

Although the warm-up means 47 is an electric heating system, it can also be implemented by a hot oil or hot water circulation system.

The relationship between the applied pressure (second applied pressure P2) in the second pressure molding machine 40 and the density ρ of the secondary powder compact 115 obtained in response thereto will be described with reference to FIG.

The density ρ obtained by the second pressure molding machine 40 follows a straight line indicated by a solid line B. That is, unlike the case of the first pressure molding machine 20 (broken line A), the density ρ does not gradually increase as the second pressure P2 is increased. That is, the density ρ does not increase until the final first pressure P1 (for example, the horizontal axis index 50, 75, or 85) in the first pressure molding step is exceeded. When the second pressure P2 exceeds the final first pressure P1, the density ρ increases at a stretch. It is understood that the second pressure molding is performed as if the first pressure molding was continuously taken over.

Thus, in the first pressure molding step, it is not necessary to perform an operation in which the first pressure P1 is increased to a value (horizontal axis index 100) corresponding to the maximum capacity at any time. That is, it is possible to eliminate energy consumption for a useless time when the first pressure molding is continued after the compression limit. This leads to reduced manufacturing costs. Moreover, since it becomes easy to avoid the overload operation exceeding the horizontal axis index 100, there is no fear of die damage. Overall, handling is easy and safe and stable operation is possible.

In each of the examples described below, the first pressure P1 is set to an equivalent pressure (any value of the ordinate index 92 to 98) that can increase the density ρ to 7.0 to 7.5 g / cm ^3. The molding process is selected and set. 7.5 g / cm ³ (vertical index 98) is the upper value that does not enter the dangerous area exceeding the vertical index 100, and 7.0 g / cm ³ (vertical index 92) is wider than the upper value. Selected as the lower value. This is for handling (pressurization setting etc.) and facilitating operation. The second pressing force P2 corresponds to the vertical axis index 92 (˜98) to 100, and the secondary compacted body 115 having a density ρ (7.75 g / cm ³ ) corresponding to the vertical axis index 102. Can be molded. In addition, in the case of Example 2, it represented with the true density ratio from the problem of the mixing ratio.

In FIG. 2, in this embodiment, the sintering machine 80 is formed from a continuous sintering furnace, and the secondary compacted body 115 introduced through the shooter 59 is continuously conveyed at a low speed by a conveyor (not shown). While being moved, the sintering process can be performed for a predetermined time at a predetermined temperature. A plurality of secondary green compacts 115 can be sintered efficiently and uniformly. That is, it is possible to manufacture a sintered molded body 120 with higher strength. In FIG. 3, the sintering machine 80 is not shown. In addition, you may form the sintering processing machine 80 from a batch type sintering furnace.

The sintering temperature is usually about 1120 ° C for iron-based materials and about 1250 ° C for high-temperature sintering. Since the sintering proceeds even in the process of increasing the temperature, the maximum temperature holding time of about 30 minutes is sufficient. In this embodiment, the values of the sintering temperature and the sintering time (conveyor speed) are configured to be changeable.

As shown in FIG. 5, the second green compact 115 is in a state where there is almost no unnecessary matter (residue or the like) 108 (high density), so that the contact area between the metal particles (101) and the metal particles (101) is large. . This means that diffusion bonding having the same area as that of the conventional method can be expected in a shorter sintering time than in the case of the conventional method. In other words, since the contact area is large, diffusion bonding can be promoted in a wider area, so that a significant improvement in mechanical properties (strength) can be expected.

Furthermore, since the internal (strain) stress can be removed by the final sintering process, no annealing process is required.

In FIG. 3B, the workpiece transfer means 50 is the predetermined compact in the heating warmer 30 for the primary compacted body 110 taken out from the first mold 21 by the first take-out means (23, 24) in FIG. 3A. The first compacted green body 110 after the temperature rise can be transported from a predetermined position in the heating temperature riser 30 to the second mold 41, and can be transported to the position by the second take-out means (43, 44). The secondary green compact 115 taken out from the second mold 41 is formed so as to be transportable to the discharge shooter 59.

The workpiece transfer means 50 of this embodiment is composed of three feed bars 51, 52, 53 that are operated synchronously as shown in FIG. 3B. The feed bars 51, 52, and 53 are advanced from the depth side of the sheet of FIG. 3A to the front (FIG. 3B) transfer line at the time of a transfer request, and then move back from the left to the right and then retreat to their original positions. The setting means (52, 43, 44) sets the heated primary compact 110 to the second mold 42 warmed to the melting point equivalent temperature.

Note that the workpiece transfer means may include a finger or the like driven in a two-dimensional or three-dimensional direction, and may be formed from a transfer device that sequentially transfers the workpiece to each mold. Further, the secondary green compact 115 can be formed so as to be transportable to the sintering machine 80.

In such an embodiment, in the manufacturing apparatus 1 for the high-strength sintered molded body 120, the high-strength sintered molding method is performed as follows.

(Procurement of mixed powder)
The mixed powder 100 in a smooth state is procured by mixing the base metal powder and 0.03 (˜0.10) wt% lubricant powder (zinc stearate powder). A predetermined amount is supplied to the mixed powder feeder 10 (step PR0 in FIG. 1).

(Mixed powder filling)
At a predetermined timing, the mixed powder supplier 10 is moved from a predetermined position (solid line) to a replenishment position (broken line) as shown in FIG. 3B. Next, the supply port of the mixed powder supplier 10 is opened, and a fixed amount of the mixed powder 100 is filled into the empty lower mold 21 (22) of the first pressure molding machine 20 (step PR1 in FIG. 1). For example, it can be filled in 2 seconds. After the filling, the supply port is closed, and the mixed powder supply machine 10 returns to a predetermined position (solid line).

(Molding of primary compacted body)
A first pressure molding process in which the upper mold 25 of the first pressure molding machine 20 moves down together with the slide 5 of FIG. 2 and pressurizes the mixed powder 100 in the lower mold 21 (22) with the first pressure P1. Begins. Solid lubricants provide sufficient lubrication. The density ρ of the compressed primary compact 110 is increased according to the broken line A in FIG. When the first applied pressure P1 reaches a pressure (9.5 Ton / cm ² ) corresponding to the horizontal index (for example, 95), the density ρ increases to 7.25 g / cm ³ (corresponding to the vertical index 95). For example, when the pressure molding for 8 seconds is completed, as shown in FIG. 3A, the primary powder compact 110 is molded in the mold (21) (step PR2 in FIG. 1). Thereafter, the upper die 25 is raised by the slide 5. In the second pressure molding machine 40, the second pressure molding process related to the primary compacted green body 110 is performed in synchronization.

(Removal of primary compacted body)
The first take-out means (23) works, and the primary compacted body 110 is pushed up to the transfer level HL. That is, it is taken out from the lower mold 21. Then, as shown in FIG. 3B, the workpiece transfer means 50 works, and the primary compacting body 110 is transferred toward the heating temperature riser 30 by the transfer bar 51. At this stage, the movable member 23 is returned to the initial position below. The primary compact 110 after the transfer is positioned on the wire mesh holding member (32) as shown in FIG. 3A.

(Heating temperature)
In FIG. 3A, the heating warmer 30 is activated. Hot air is blown from the blowing hood 31 and the temperature of the primary green compact 110 is raised to the melting point equivalent temperature (120 ° C.) of the lubricant powder (step PR3 in FIG. 1). That is, the lubricant is dissolved, and the lubricant distribution in the primary compact 110 is uniformly modified by the flow. The heating temperature raising time is, for example, 8 to 10 seconds. The hot air is recirculated through the wire mesh holding member 32 and the exhaust circulation hood 33.

(Set of heated primary compacts)
As shown in FIG. 3B, the heated primary compact 110 is transferred to the second pressure molding machine 40 by the workpiece transfer means 50 (transfer bar 52) and positioned above the lower die 41. Is set on the movable member 43 in the lower mold 41 (42) (step PR4 in FIG. 1).

(Mold warm-up)
In the second pressure molding machine 40, the warm-up means 47 works, and before the primary compacting body 110 is received (set), the mold [41 (42)] is moved to the temperature corresponding to the melting point of the lubricant powder. Warm to 120 ° C. Thereafter, re-solidification of the lubricant in the temperature-primed primary compact 110 that has been received can be prevented.

(Formation of secondary compacted body)
The upper die 45 moves down together with the slide 5 of FIG. 2 as shown in FIG. 3A and starts to pressurize the primary powder compact 110 in the lower die 41 (42) with the second pressure P2. Liquid lubricant provides sufficient lubrication. In particular, since the lubricant flows in all directions as the pressure molding proceeds, the frictional resistance between the particles and the mold can be efficiently reduced as well as between the particles. The density ρ of the compressed primary compact 110 is increased according to the solid line B in FIG. That is, when the second pressing force P2 exceeds the horizontal axis index (for example, 95... 9.5 Ton / cm ² ), the density ρ suddenly increases from 7.25 g / cm ³ to the density ρ corresponding to the vertical axis index 102. It increases to (7.75 g / cm ³ ). When the second applied pressure P2 is increased to an abscissa index of 100 (10 Ton / cm ² ), the density ρ (7.75 g / cm ³ ) becomes uniform as a whole. Here, for example, when the second pressure molding process for 8 seconds is completed, the secondary green compact 115 is molded in the mold (41) (step PR5 in FIG. 1). Thereafter, the upper mold 45 is raised by the slide 5. Note that, in the first pressure molding machine 20, the first pressure molding process for the subsequent primary powder compact 110 is performed synchronously.

(Removal of secondary compacted body)
The 2nd taking-out means (43) works and the secondary compacting body 115 is pushed up to the transfer level HL. That is, it is taken out from the lower mold 41. Then, as shown in FIG. 3B, the workpiece transfer means 50 operates, and the secondary compacting body 115 is transferred toward the discharge chute 59 by the transfer bar 53. At this stage, the movable member 43 is returned to the initial position below.

(Molding cycle)
According to the compacting method according to the above two forming steps, the first pressure forming process, the heating temperature raising process and the second pressure forming process for the metal powder 100 supplied and filled in order can be executed synchronously. Therefore, the secondary compacted body 115 can be formed in a cycle time of 12 to 14 seconds obtained by adding a workpiece transfer time (for example, 2 to 4 seconds) to the longest heating temperature raising time (10 seconds).

(Molding of sintered compact)
The secondary green compact 115 introduced from the discharge chute 59 is sintered in the sintering machine 80. The green compact 115 shown in FIG. 5 becomes a sintered compact 120 that is further enhanced in strength by sintering. The supply of the sintered compact 120 (for example, parts for automobiles and equipment for small and light complex shapes and high mechanical strength) can be stabilized, and can greatly contribute to the reduction of production costs thereof.

Example 1
A mixed powder 100 was prepared by mixing 0.03 (˜0.10) wt% of lubricant powder (zinc stearate powder) with base metal powder (pure iron powder for machine parts). The primary compacted body 110 having a density of 7.0 (˜7.5) g / cm ^{3 was} molded by pressure molding with the first pressure P1. When the mixing amount was 0.03% by weight, the first pressure molding process could be performed most smoothly. The primary green compact 110 heated to 120 ° C. is press-molded by the second pressure P2 to form a secondary green compact 115 having a density ρ7.75 g / cm ³ corresponding to the longitudinal index 102. did. After that, the sintered compact 120 with increased mechanical strength was obtained by subjecting the secondary green compact 115 to a sintering treatment at 1150 ° C. for 30 minutes. Mechanical strength (eg, tensile force) increases with increasing density. In other words, since the density is increased in the second pressure forming step before the sintering process as compared with the conventional method, mechanical parts with further increased mechanical strength can be efficiently manufactured by sintering. I was able to. In addition, it confirmed that it can shape | mold similarly, when adding metal powder for alloy formation to base metal powder. Thus, a high-strength finish can be achieved even with the elongated round shaft shape shown in FIG.

(Example 2)
Mixed powder 100 was prepared by mixing 0.03 (˜0.10) wt% of lubricant powder (zinc stearate powder) with base metal powder (Fe—Si alloy powder). The first green compact 110 having a true density ratio of 70 to 85% was molded by pressure molding with the first pressure P1. When the mixing amount was 0.03% by weight, the first pressure molding process could be performed most smoothly. The primary green compact 110 heated to 120 ° C. is press-molded with the second pressure P2 to form a secondary green compact 115 having a true density ratio of 85 to 95% corresponding to the longitudinal index 102. did. Thereafter, the secondary compacted body 115 was subjected to a sintering process at 1150 ° C. for 30 minutes to obtain a sintered compact 120 with further increased mechanical strength. That is, a sintered compact having high mechanical strength as compared with a sintered compact by a conventional molding method could be efficiently produced.

Thus, according to this embodiment, the first pressure P1 is applied to the mixed powder 100 in the first pressure molding step (in the first mold) and at a room temperature below the melting point of the lubricant powder. The primary compacted body 110 is molded, the primary compacted body 110 is heated to a temperature corresponding to the melting point of the lubricant powder in the heating temperature raising step, and then warmed up in the second pressure molding step. 2 to form a secondary green compact 115 having a higher density by applying a second pressing force P2 to the primary green compact 110 at a temperature corresponding to the melting point. Since it is a manufacturing method of a high-strength sintered molded body in which the molded body 115 is sintered to form a sintered molded body, the high-strength sintered molded body 120 can be reliably and stably manufactured, and the manufacturing cost is greatly reduced. be able to.

Further, since the melting point of the lubricant powder is a low melting point within the temperature range of 90 to 190 ° C., the selectivity of the lubricant can be expanded while promoting the suppression of oxidation.

Moreover, even if the base metal powder is changed to either pure iron powder or Fe—Si alloy powder, and other conditions are the same, the sintered compact 120 having excellent mechanical strength corresponding to the type of the base metal powder. Can be manufactured efficiently and stably at a low cost.

In addition, since the second pressing force P2 can be set to a value equal to the first pressing force P1, it is easy to perform and handle the pressure forming step, and indirectly increase the production cost of the green compact. In addition, it can be easily constructed based on, for example, a single press machine.

In consideration, the capacity of a conventional apparatus (for example, a press machine) (the horizontal axis index 100 in FIG. 4) could not be increased beyond the density corresponding to the vertical axis index 100, according to the present invention. For example, it is possible to increase the density corresponding to the vertical index 102 with the same apparatus. This fact can be commended as a breakthrough in the art.

Furthermore, since the manufacturing apparatus 1 is composed of the mixed powder supply machine 10, the first pressure molding machine 20, the heating temperature raising machine 30, the second pressure molding machine 40, and the sintering machine 80, The manufacturing method of the high-strength sintered compact 120 can be reliably and stably carried out.

(Second Embodiment)
This embodiment is illustrated in FIG. Compared to the case of the first embodiment, the mixed powder supply machine 10, the first pressure molding machine 20, and the sintering processing machine 80 are left as they are, and the heating temperature riser 30 and the second pressure molding machine. 40 is formed integrally.

That is, the manufacturing apparatus 1 forms the heating temperature riser 30 and the second pressure molding machine 40 in the case of the first embodiment from a heating and pressure molding machine 70 in which these functions are integrated. It is. The heat-pressure molding machine 70 is formed of a plurality of (two in this embodiment) heat-pressure molding child machines 70A, 70B, and each of the heat-pressure molding child machines 70A, 70B is manufactured by control means (not shown). It is possible to select and operate sequentially for each cycle.

The basic structure of each heating and pressing molding machine 70A (70B) corresponds to the second pressing machine 40 in the first embodiment. In addition, each heating and pressure molding child machine 70A (70B) has a composite function type heating means having a composite function corresponding to each function of the heating temperature riser 30 and the warming-up means 47 in the case of the first embodiment. 48 is provided.

That is, the multi-function heating means 48 is an electric heating system having a set temperature switching function. The lower mold 41 can be warmed up to the temperature corresponding to the melting point of the lubricant (120 ° C.) in advance (before receiving the primary green compact 110). After receiving the primary green compact 110, the calorific value is largely switched so that the entire primary green compact 110 can be heated to a temperature corresponding to the melting point of the lubricant (120 ° C.). It is also possible to selectively switch the heating part. After the heating temperature rise, the same second heat forming process as that of the second pressure molding machine 40 in the first embodiment is performed. The multi-function heating unit 48 functions so as to be able to maintain the temperature of the primary green compact 110 at the lubricant melting point equivalent temperature (120 ° C.) or higher during the second thermoforming process.

As shown in FIG. 7, each heating and pressing molding child machine 20, 70 </ b> A, 70 </ b> B has an independent press machine structure, and each slide 5, 5 </ b> A, 5 </ b> B is driven up and down by rotation control of each machine motor. . That is, when one (the other) of each of the heating and pressing child machines 70A and 70B performs a pressure molding operation, the other (one) is preheated and does not perform the pressure molding operation. The same applies to the case where the hot press molding machine 70 is formed from three or more hot press molding slaves in relation to the manufacturing cycle time.

In the apparatus according to this embodiment, the first primary compacting body 110 is being pressure-molded by the first thermoforming machine 20, while the second thermocompressing machine 70A (or 70B) is the second. The first primary green compact 110 is heated and heated, and the first primary green compact 110 is set as the secondary green compact 115 by the other heating and pressing compactor 70B (or 70A). Pressure molding is performed as much as possible. During this period, the sintering machine 80 is in the process of forming a sintered compact 120 by subjecting a plurality of secondary compacts 115 introduced before to the sintering process.

Therefore, according to this embodiment, the heating and pressing molding machine 70 may be constructed from a plurality of pressing molding machines 70A and 70B having the same structure, so that it is compared with the case of the first embodiment. The device can be simplified. Simplification of the production line can be promoted and handling becomes easier. Moreover, according to this embodiment, the tact times of the first pressurizing step, the heating temperature raising step, and the second pressurizing step can be matched.

The first pressure molding machine 20 and the heating and pressure molding machine 70A (or 70B) or the first pressure molding machine 20 and each of the heating and pressure molding machines 70A and 70B are combined into one press machine. It can also be constructed as a structure.

As described above, the embodiments of the present invention have been described. However, those skilled in the art can easily understand that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention.

1. Manufacturing apparatus for high-strength sintered compacts, 10. Mixed powder feeder, 20. First press forming machine, 30. Heating temperature riser, 40. Second press forming machine, 47. Warming-up means, 48. Multifunction heating. Means, 50 workpiece transfer means, 70 heating and pressing molding machine, 70A, 70B heating and pressing molding machine, 80 sintering processing machine, 100 mixed powder, 101 iron powder, 108 unnecessary (residue), 109 void, 110 Primary compacted compact, 115 Secondary compacted compact, 120 Sintered compact, 128 Partially sintered

Claims (7)

1. Pressing the mixed powder, which is a mixture of the base metal powder and the lubricant powder, to form a green compact, and sintering the green compact to form a sintered compact with high mechanical strength And a sintering molding process to
   The pressure molding step is formed from a first pressure molding step and a second pressure molding step sandwiching a heating temperature raising step,
   The first pressure molding step is to form a primary compacted body by applying a first pressing force to the mixed powder at room temperature below the melting point of the lubricant powder in the first mold,
   The heating temperature raising step is to heat the primary green compact to raise the temperature of the primary green compact to a temperature corresponding to the melting point of the lubricant powder,
   Density is obtained by applying a second pressing force to the primary green compact in the second mold warmed to the melting point equivalent temperature of the lubricant powder in the second pressure forming step and at the melting point equivalent temperature. A method for producing a high-strength sintered compact, which is intended to form a secondary compacted compact with increased slag.
2. The method for producing a high-strength sintered compact according to claim 1, wherein the melting point of the lubricant powder is a low melting point belonging to a temperature range of 90 to 190 ° C.
3. The mixed powder is a mixture of pure iron powder, which is the base metal powder, and zinc stearate powder, which is the lubricant powder, by 0.03 to 0.10% by weight. The density of the secondary green compact is selected to be compressible to 7.0 to 7.5 g / cm ³ , and the second applied pressure reduces the density of the secondary green compact to 7.75 g / cm ³ . The manufacturing method of the high intensity | strength sintered compact of Claim 1 or 2 selected as what can be compressed.
4. The mixed powder is a mixture of Fe-Si alloy powder, which is the base metal powder, and zinc stearate powder, which is the lubricant powder, in an amount of 0.03 to 0.10% by weight, and the first applied pressure is The density of the primary green compact is selected to be able to be compressed to a true density ratio of 70 to 85%, and the second applied pressure reduces the density of the secondary green compact to a true density ratio of 85 to 95%. The manufacturing method of the high intensity | strength sintered compact of Claim 1 or 2 selected as what can be compressed.
5. The method for producing a high-strength sintered compact according to claim 1 or 2, wherein the second pressing force is selected to be equal to the first pressing force.
6. A mixed powder feeder capable of supplying and filling a mixed powder, which is a mixture of a base metal powder and a low melting point lubricant powder, to the outside;
   A first pressure molding machine for forming a primary powder compact by applying a first pressing force to the mixed powder filled in the first mold using the mixed powder feeder;
   A heating temperature riser for raising the temperature of the primary green compact taken out from the first mold to a temperature corresponding to the melting point of the lubricant powder;
   Having a second mold that can be warmed up to the temperature corresponding to the melting point in advance, the second pressing force is applied to the primary compact that has been set in the second mold that has been warmed up and has been heated up A second pressure molding machine for forming a secondary green compact with increased density
   A high-strength sintered compact manufacturing apparatus, comprising: a sintering machine that manufactures a sintered compact with increased mechanical strength by subjecting a secondary green compact to a sintering treatment.
7. The heating temperature raising machine and the second pressure molding machine are formed from a heating and pressure molding machine in which these functions are integrated, and the heating and pressure molding machine is formed from a plurality of heating and pressure molding child machines. 7. The apparatus for producing a high-strength sintered molded body according to claim 6, wherein the apparatus is formed and is capable of selecting and sequentially operating each heating and pressing molding machine for each cycle.

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