JP2020117775A - Method and apparatus for manufacturing ferrous sintered body - Google Patents

Abstract

To obtain a ferrous sintered body having excellent various mechanical characteristics and excellent shape accuracy by applying excellent correction effect to the ferrous sintered body irrespective of the presence or absence of heat treatment after hardening.SOLUTION: A method for manufacturing a ferrous sintered body in the present invention includes a correction step S4 of making a correction of the ferrous sintered body 1 by subjecting a raw material powder composed mainly of ferrous powder to compression molding, and by constraining the ferrous sintered body 1 obtained by sintering with the use of metal molds 15a and 15b. In the correction step S4, the ferrous sintered body 1 is set to less than 100 degrees, and the ferrous sintered body 1 are constrained by the metal molds 15a and 15b in a state where the metal molds 15a and 15b have a higher temperature than the ferrous sintered body 1 by heating.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method and an apparatus for manufacturing an iron-based sintered body, and particularly to a technique for effectively correcting an iron-based sintered body.

As a method of manufacturing a component having a complicated shape such as a gear, a manufacturing method utilizing powder (powder metallurgy method) has attracted attention from the viewpoint of near net shape. In this manufacturing method, a metal powder is compression-molded into a predetermined shape and then heated to a temperature according to the type of metal to form a sintered body. For example, for parts requiring strength and wear resistance, metal powder having a composition containing iron as a main component and containing a predetermined amount of carbon is compacted, sintered, and then quenched and tempered. As a result, parts satisfying the required specifications are manufactured. Further, in recent years, a technique related to so-called sintering hardening (sinter hardening) in which quenching is performed by utilizing cooling after sintering has been developed.

By the way, in this kind of sintered part, there is a problem that the shape accuracy is deteriorated due to the deformation after sintering. For example, in the case of a thin plate-shaped sintered component such as a gear, the flatness thereof is known to deteriorate. As a countermeasure against this, many correction methods have been conventionally proposed.

For example, Patent Document 1 discloses a technique of sizing the iron-based sintered body heated to 300 to 600 degrees after the sintering treatment of the iron-based sintered body and before the quenching treatment. Further, in Patent Document 2, a sintered component is heated to a predetermined temperature to be austenite and rapidly cooled, and at the same time, the sintered component is constrained by a mold during sizing to be rectified while quenching. Techniques for doing so are disclosed. Further, Patent Document 3 discloses a technique of reheating a sintered body after quenching to 100 to 550 degrees and restraining the sintered body in a high temperature state with a mold to perform straightening.

JP, 2009-149957, A JP, 2016-141857, A JP, 11-80810, A

However, according to the method described in Patent Document 1, since the heat treatment such as quenching is performed after the correction, the sintered body may be deformed again by the heat treatment. According to the method described in Patent Document 2, it is possible to obtain a quenched and sintered body that has been straightened, but when heat treatment such as tempering is additionally performed after quenching, the sintered body may be deformed again. Occurs. According to the method described in Patent Document 3, the sintered body can be straightened while being subjected to heat treatment (tempering, etc.) after quenching, but this is required depending on the shape of the sintered body. There is a problem that it is difficult to correct to a level. In particular, when the sintered body is in the form of a thin plate, the warpage after heat treatment becomes remarkable, so that a more effective straightening technique is required at present.

In view of the above circumstances, in the present specification, regardless of the presence or absence of heat treatment after quenching, it is possible to impart an excellent straightening effect to the iron-based sintered body, which makes it possible to obtain iron having excellent mechanical properties and excellent shape accuracy. Obtaining a system sintered body is a technical problem to be solved.

The solution to the above problem is achieved by the method for manufacturing an iron-based sintered body according to the present invention. That is, this manufacturing method corrects the iron-based sintered body by restraining the iron-based sintered body obtained by compressing and sintering the raw material powder containing iron-based powder as the main component with the mold. In the method for manufacturing an iron-based sintered body having a straightening step of performing, in the straightening step, the temperature of the iron-based sintered body is less than 100 degrees, and the mold is heated to a temperature higher than that of the iron-based sintered body. It is characterized in that the iron-based sintered body is constrained by a mold. The “main component” here refers to the powder with the highest content ratio among the powders contained in the raw material powder. In this case, the raw material powder containing iron-based powder as a main component also includes the raw material powder made of only iron-based powder.

As a result of diligent study on the influence of the temperature of the iron-based sintered body and the temperature of the restraining die on the straightening effect, the inventors have found that the temperature of the iron-based sintered body in the quenched state is less than 100 degrees. And, it was found that when the iron-based sintered body is straightened by the die in a state where the temperature of the die is higher than the temperature of the iron-based sintered body, a very excellent straightening effect is obtained. It was The present invention was made on the basis of the above-mentioned findings, and by binding an iron-based sintered body in a state of less than 100 degrees with a die in a state of being heated to a higher temperature than the iron-based sintered body by heating, It is possible to obtain a better correction effect. Further, if the iron-based sintered body is restrained in a state where the iron-based sintered body is set to a relatively low temperature and the die is heated to a relatively high temperature, the temperature of the die can be controlled (for example, By holding a predetermined temperature for a certain period of time, it is relatively easy to perform heat treatment other than quenching at the same time as straightening. Therefore, it is possible to avoid the situation where the iron-based sintered body is deformed again by the heat treatment after quenching, and it is possible to maintain excellent shape accuracy. As described above, according to the present invention, it is possible to obtain an iron-based sintered body that is excellent in various mechanical characteristics and is excellent in shape accuracy.

In the method for manufacturing an iron-based sintered body according to the present invention, the difference between the temperature of the mold and the temperature of the iron-based sintered body may be 200 degrees or more.

As described above, by performing the straightening step in a state where the difference between the temperature of the mold and the temperature of the iron-based sintered body is 200 degrees or more, a more excellent straightening effect can be obtained. The above configuration is particularly effective when the amount of deformation after heat treatment is large.

In the method for manufacturing an iron-based sintered body according to the present invention, the temperature of the iron-based sintered body may be room temperature. In addition, the normal temperature referred to herein means a predetermined temperature in the range of 5 degrees Celsius or more and 35 degrees Celsius or less according to JIS 8703.

As described above, by performing the straightening step in a state where the temperature of the iron-based sintered body is room temperature, a further excellent straightening effect can be obtained.

In the method for manufacturing an iron-based sintered body according to the present invention, the temperature of the mold may be less than 400 degrees.

In this way, by performing the straightening step in a state where the temperature of the restraining mold is less than 400 degrees, it is possible to suppress the decrease in hardness due to heat treatment such as tempering performed after quenching as much as possible, and it is excellent. It is possible to obtain a correction effect.

Further, in the method for manufacturing an iron-based sintered body according to the present invention, the constraint time by the mold may be 1 minute or more and 20 minutes or less.

Thus, by setting the holding time of the iron-based sintered body by the mold to 1 minute or more, an excellent straightening effect on the iron-based sintered body can be stably obtained. On the other hand, even if the restraint time exceeds 20 minutes, there is not much difference in the correction effect, so from the viewpoint of productivity, it is preferable to limit it to 20 minutes at the maximum.

Further, in the method for manufacturing an iron-based sintered body according to the present invention, the method further comprises a tempering step of subjecting the iron-based sintered body to a tempering treatment, and heating the iron-based sintered body with restraint by a mold. A tempering process may be performed according to.

In this way, if the tempering process is performed by heating the iron-based sintered body by restraining it with the mold, the deformation caused in the iron-based sintered body due to the tempering can be corrected. Alternatively, it is possible to suppress the deformation that should occur in the iron-based sintered body due to tempering. As a result, it is possible to provide the iron-based sintered body with high shape accuracy even after the tempering process. Of course, the iron-based sintered body can be subjected to the straightening treatment and the tempering treatment at the same time, which is also preferable from the viewpoint of productivity.

Further, in the method for producing an iron-based sintered body according to the present invention, a sintering step for obtaining an iron-based sintered body by sintering a powder compact formed by compression-forming iron-based powder before the straightening step. And a quenching step of subjecting the iron-based sintered body to a quenching treatment after the sintering step. Alternatively, before the straightening step, a sinter-quenching step in which a powder compact formed by compression-molding an iron-based powder is heated to a predetermined temperature for sintering and a quenching process is performed by cooling after heating is further performed. You may prepare.

INDUSTRIAL APPLICABILITY The present invention is capable of imparting a very excellent straightening effect to an iron-based sintered body that has been subjected to quenching. Therefore, as described above, the sintering step and quenching are performed before the straightening step. By providing a step or by providing a sintering and hardening step, it becomes possible to mass-produce an iron-based sintered body that is excellent in various mechanical properties such as strength and is also excellent in shape accuracy.

In the method for manufacturing an iron-based sintered body according to the present invention, the iron-based powder may contain iron as a main component and at least carbon. Further, in this case, the iron-based powder may contain carbon in an amount of 0.3 wt% or more and 1.0 wt% or less.

As described above, by forming the iron-based sintered body with the iron-based powder containing at least carbon, the heat treatment such as the above-described quenching can be sufficiently performed, and thus, the iron-based firing excellent in various mechanical properties such as strength can be achieved. It becomes possible to obtain a union.

Further, in the method for manufacturing an iron-based sintered body according to the present invention, the iron-based sintered body may have a thin plate shape. Further, in this case, the iron-based sintered body may be a gear.

The present invention is particularly effective for straightening an iron-based sintered body having a thin plate shape. Therefore, when the iron-based sintered body has a thin plate shape, the iron-based sintered body is subjected to the straightening step according to the present invention. This makes it possible to obtain a very excellent correction effect.

The solution to the above-mentioned problems can also be achieved by the apparatus for producing an iron-based sintered body according to the present invention. That is, this manufacturing apparatus corrects the iron-based sintered body by restraining the iron-based sintered body obtained by compression molding and sintering the raw material powder containing iron-based powder as the main component. In an iron-based sintered body manufacturing apparatus including a device, the straightening device has a die for constraining the iron-based sintered body and a heating unit for heating the die, and the straightening device is an iron-based sintered body. It is characterized by the fact that the iron-based sintered body can be restrained by the mold in a state where the bonded body is less than 100 degrees and the mold is heated to a temperature higher than that of the iron-based sintered body by heating in the heating section. ..

According to the manufacturing apparatus of the present invention, as in the manufacturing method of the present invention, it is possible to obtain a correction effect superior to the conventional one. In addition, if the iron-based sintered body is kept at a relatively low temperature and the iron-based sintered body is constrained while the die is heated to a relatively high temperature by heating the heating section, the temperature of the die should be controlled. Thus, heat treatment other than quenching can be relatively easily applied simultaneously with straightening. Therefore, it is possible to avoid the situation where the iron-based sintered body is deformed again by the heat treatment after quenching, and it is possible to maintain excellent shape accuracy. As described above, according to the present invention, it is possible to obtain an iron-based sintered body that is excellent in various mechanical characteristics and is excellent in shape accuracy.

As described above, according to the present invention, it is possible to impart an excellent straightening effect to the iron-based sintered body regardless of the presence or absence of heat treatment after quenching, and thus excellent in various mechanical characteristics and also in shape accuracy. It is possible to obtain an iron-based sintered body.

It is a flow chart which shows the whole flow of the manufacturing method of the iron system sintered compact concerning one embodiment of the present invention. It is a figure which shows the correction device which concerns on one Embodiment of this invention, and its periphery structure. It is sectional drawing of a correction device. It is a flow chart which shows the whole flow of the manufacturing method of the iron system sintered compact concerning other embodiments of the present invention. It is a side view on the surface plate of the iron system sintered compact concerning an example.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a flowchart showing the overall flow of a heat treatment process according to an embodiment of the present invention. As shown in FIG. 1, in the heat treatment step according to the present invention, a molding step S1 of compressing and molding a raw material powder containing an iron-based powder as a main component, and a sintering treatment of a powder compact obtained by compression molding. Sintering step S2, quenching step S3 of performing a quenching treatment on the iron-based sintered body obtained by the sintering treatment, straightening step S4 of performing a straightening treatment on the quenched iron-based sintered body, and quenching A tempering step S5 of tempering the iron-based sintered body that has been subjected to the treatment and a finishing step S6 of finishing the iron-based sintered body that has been subjected to the straightening treatment and the tempering treatment are provided. In the finishing process S6, one or a plurality of machining processes such as polishing and shot peening are performed. Of course, the finishing step S6 can be omitted. Although illustration is omitted, if necessary, a cleaning step and an inspection step may be provided after the quenching step S3 and the tempering step S5, respectively.

FIG. 2 is a diagram showing the straightening device 10 used in the straightening step S4 shown in FIG. 1 and its peripheral configuration. The straightening device 10 is configured to perform a straightening process on a plurality of works (that is, the iron-based sintered body 1) transported on the transport path 11 in a predetermined direction, and the dies 15a and 15b. The iron-based sintered body 1 can be restrained by (see FIG. 3 described later). In the present embodiment, a temperature adjusting chamber 12 that adjusts the temperature of the iron-based sintered body 1 is arranged on the upstream side of the conveying path 11 with respect to the straightening device 10. Further, in the present embodiment, the straightening device 10 also serves as a heating device that performs heating for performing the tempering process on the iron-based sintered body 1, and the iron is provided on the downstream side of the transport path 11 with respect to the straightening device 10. A cooling device 13 that cools the system sintered body 1 to perform a tempering process is provided. Hereinafter, the configuration of the straightening device 10 will be mainly described, and then an example of the straightening process S4 and the tempering process S5 using the straightening device 10 will be described.

Here, the target iron-based sintered body 1 may have any shape in principle, and may have a thin plate shape such as a disk shape (with or without a central hole). In addition, the composition of the raw material powder that constitutes the iron-based sintered body 1 is also optional in principle, and contains, for example, iron-based powder containing carbon in a predetermined ratio (0.3 wt% or more and 1.0 wt%) as the main component. The powder composition may be mentioned. Of course, the raw material powder may be composed of only iron-based powder. Further, the type of the iron-based sintered body 1 from the viewpoint of application is also arbitrary, and for example, mechanical parts used for applications requiring relatively high strength, hardness, toughness (fatigue strength), such as gears. Can be the target.

As shown in FIG. 3, the straightening device 10 includes a pair of molds 15a and 15b for sandwiching and restraining the iron-based sintered body 1 from above and below, and a pair of molds 15a and 15b that are in contact with each other. It has heating parts 16a and 16b. In this embodiment, the lower die 15a and the lower heating portion 16a are both fixed to the fixed die 17a, and the upper die 15b and the upper heating portion 16b are both fixed to the movable die 17b. .. As a result, when the movable die 17b is moved up and down by a driving device (not shown), the upper die 15b and the upper heating part 16b fixed to the movable die 17b are moved up and down.

In addition, in the present embodiment, the straightening device 10 further includes a pair of heat insulating parts 18a and 18b on the opposite sides of the heating parts 16a and 16b from the molds 15a and 15b, and cools the heating parts 16a and 16b. It further includes a pair of cooling units 19a and 19b. As a result, the respective molds 15a and 15b can be heated to a predetermined temperature by the corresponding heating units 16a and 16b, and the temperatures of the respective molds 15a and 15b can be maintained by the heat insulating units 18a and 18b. Further, the respective cooling units 19a, 19b can cool the corresponding molds 15a, 15b. In this case, the straightening device 10 further includes a control unit 20 that controls the heating units 16a and 16b and the cooling units 19a and 19b. As a result, the temperature of each mold 15a, 15b can be controlled.

In addition, in FIG. 3, each heating unit 16a, 16b has a case where it has a metal heating plate 16a1, 16b1 and one or a plurality of cartridge heaters 16a2, 16b2 embedded in each heating plate 16a1, 16b1. Although illustrated, of course, other configurations may be adopted. Similarly, in FIG. 3, each cooling unit 19a, 19b exemplifies a case where the cooling plate 19a1, 19b1 made of metal and the cold water pipes 19a2, 19b2 embedded in each cooling plate 19a1, 19b1 are exemplified. However, of course, other configurations may be adopted.

Further, in the present embodiment, the conveying path 11 of the iron-based sintered body 1 is configured to extend in the horizontal direction and pass between the pair of molds 15a and 15b forming the straightening device 10 (see FIG. 3). Of course), of course, the transportation mode of the iron-based sintered body 1 is not limited to this. For example, although illustration is omitted, the transport path 11 is a first transport path for transporting the iron-based sintered body 1 in the horizontal direction, and a second transport for raising the iron-based sintered body 1 from the downstream end of the first transport path. Path, a third conveyor path for horizontally conveying the iron-based sintered body 1 from the downstream end of the second conveyor path, and a fourth conveyor path for descending the iron-based sintered body 1 from the downstream end of the third conveyor path. , And a fifth conveyance path for horizontally conveying the iron-based sintered body 1 from the downstream end of the fourth conveyance path. The means for conveying the iron-based sintered body 1 along the conveying path 11 is arbitrary and, for example, although not shown, a conveyor or a power cylinder (hydraulic cylinder, air cylinder, electric cylinder) or the like is used. Can be adopted.

Further, means for introducing and discharging the iron-based sintered body 1 on the transport path 11 between the pair of molds 15a and 15b is also arbitrary, and for example, although not shown, the iron-based sintered body 1 on the transport path 11 is omitted. An extruding device that extrudes the sintered body 1 toward the downstream side, or a drawing device that retracts the iron-based sintered body 1 on the transport path 11 toward the downstream side can be used. Alternatively, although not shown in the figure, the iron-based sintered body 1 on the conveying path 11 is picked up and introduced between the pair of molds 15a and 15b, and the iron-based sintered body is inserted between the pair of molds 15a and 15b. A robot arm for taking out the body 1 and returning it to the transport path 11 may be adopted.

The straightening device 10 having the above configuration is adjacent to the temperature adjusting chamber 12 and the cooling device 13 on the upstream side and the downstream side of the transport path 11 (see FIG. 2 ). As a result, the iron-based sintered body 1 carried out from the temperature adjusting chamber 12 is carried into the straightening device 10, and the iron-based sintered body 1 carried out from the straightening device 10 is carried into the cooling device 13. Has become.

The temperature adjustment chamber 12 is a device for adjusting the temperature of the iron-based sintered body 1 that has been carried in to a predetermined temperature, and has a device configuration according to the temperature adjustment method. For example, when the temperature is adjusted by air conditioning, the control unit (not shown) controls the air conditioner to adjust the temperature in the temperature adjustment chamber 12 to less than 100 degrees. In the present embodiment, the temperature inside the temperature adjustment chamber 12 is adjusted to a predetermined temperature (for example, 20 degrees) in the range of normal temperature (5 to 35 degrees), and the iron carried into the temperature adjustment chamber 12 through the quenching step S3. The temperature of the system sintered body 1 can be adjusted to the above predetermined temperature. The controller 20 of the straightening device 10 shown in FIG. 3 may adjust the temperature in the temperature adjusting chamber 12 adjacent to the straightening device 10. In this case, the control unit 20 can control both the temperature of the pair of molds 15a and 15b and the temperature of the iron-based sintered body 1 immediately before being introduced between the pair of molds 15a and 15b.

The cooling device 13 is a device for cooling the iron-based sintered body 1 heated by the straightening device 10, and has a device configuration according to the cooling method. For example, in the case of air cooling, the internal space of the cooling device 13 is controlled to a predetermined ambient temperature by an air conditioner (not shown), and the iron-based sintered body 1 carried into the cooling device 13 is cooled to a predetermined temperature at a predetermined cooling rate. Cooled down. Alternatively, in the case of water cooling, the cooling device 13 has a liquid tank for a cooling liquid (not shown), and the iron-based sintered body 1 carried into the cooling device 13 is immersed in the cooling liquid to obtain a predetermined cooling rate. Is cooled to a predetermined temperature.

Next, an example of a method for manufacturing the iron-based sintered body 1 according to the present invention will be described focusing on the straightening step S4 and the tempering step S5 of the iron-based sintered body 1 using the straightening apparatus 10 having the above-described configuration.

(S1) Molding Step In this step, first, a raw material powder containing iron-based powder having the above-mentioned composition as a main component is supplied to a molding device (not shown) and pressurized. Thus, the raw material powder is compression-molded to obtain a green compact having a predetermined shape.

(S2) Sintering Step Subsequently, the powder compact obtained in the molding step S1 is supplied to a sintering device (not shown) and subjected to a predetermined heat treatment, thereby obtaining a sintered body (iron-based sintered body 1). To get At this time, the heating temperature is set within the range of the sintering temperature of the raw material powder (usually the iron-based powder that is the main component).

(S3) Quenching Step In this step, the iron-based sintered body 1 obtained in the sintering step S2 is supplied to a quenching device (heating device, cooling device) not shown, and is heated and cooled at a predetermined temperature history. Apply quenching treatment. At this time, depending on the iron-based sintered body 1, deformation occurs due to the quenching treatment.

(S4) Straightening step (S5) Tempering step After obtaining the iron-based sintered body 1 in the state where the quenching treatment is performed as described above, the iron-based sintered body 1 is subjected to the straightening treatment. In this embodiment, the tempering process is performed together with the straightening process. Specifically, as shown in FIG. 2, the iron-based sintered body 1 in the state of being subjected to the quenching treatment is conveyed along the conveying path 11, and the temperature adjusting chamber 12 adjacent to the straightening device 10 on the upstream side thereof. Bring it in. Here, the temperature of the temperature adjusting chamber 12 is adjusted to less than 100 degrees (for example, room temperature), and the iron-based sintered body 1 is held at this ambient temperature for a predetermined time, so that the iron carried in is transferred. The temperature of the system sintered body 1 becomes less than 100 degrees. The iron-based sintered body 1 in a state where the temperature is lower than 100 degrees is carried into the straightening device 10 adjacent to the temperature adjusting chamber 12 on the downstream side of the transport path 11.

The iron-based sintered body 1 carried into the straightening device 10 is introduced between the pair of molds 15a and 15b (see FIG. 3) by the above-mentioned predetermined means. Since the temperature of the iron-based sintered body 1 at the time of being introduced between the pair of molds 15a and 15b is substantially equal to the temperature at the time of carrying out the temperature adjustment chamber 12 (almost unchanged), the iron-based baking is performed. The united body 1 is introduced between the pair of molds 15a and 15b at a temperature of less than 100 degrees. At this time, the control unit 20 heats the heating units 16a and 16b of the straightening device 10 to a temperature higher than the temperature of the iron-based sintered body 1. Specifically, each die 15a, 15b is heated to a temperature higher than the temperature of the iron-based sintered body 1 by 200 degrees or more (for example, a predetermined temperature in the range of 250 degrees or more and 350 degrees or less). Is in a state. When the straightening step S4 and the tempering step S5 are performed at the same time as in the present embodiment, the temperatures of the respective molds 15a and 15b are within a range in which a sufficient straightening effect can be expected, and It is preferable to set within a range in which various mechanical characteristics are expected to be improved (for example, 270 degrees or more and 320 degrees or less).

With the temperature of the iron-based sintered body 1 and the molds 15a and 15b adjusted as described above, the movable mold 17b is lowered by a driving device (not shown). As a result, the upper mold 15b approaches the lower mold 15a together with the movable mold 17b, and the iron-based sintered body 1 in the state of being introduced between the pair of molds 15a and 15b is sandwiched from the vertical direction. .. At this time, for example, by adjusting the pressure applied to the iron-based sintered body 1, the iron-based sintered body 1 is constrained at a predetermined pressure. Then, this restrained state is held for a certain time (for example, a predetermined time within a range of 1 to 20 minutes). As a result, the deformation of the iron-based sintered body 1 is corrected. As a result, the straightening process for the iron-based sintered body 1 is completed. Further, in the present embodiment, the iron-based sintered body 1 is heated to a temperature at which tempering can be performed by the pair of molds 15a and 15b (heating step of tempering step S5). After that, the movable mold 17b is raised to move the pair of molds 15a, 15b away from each other, and the iron-based sintered body 1 is discharged from between the pair of molds 15a, 15b by the above-mentioned predetermined means. .. In addition, during the holding as described above, the temperature control by the control unit 20 is performed so that the temperature of each of the molds 15a and 15b becomes constant. Of course, the temperature may be changed within a range that does not adversely affect the results of straightening and tempering.

In the present embodiment, the iron-based sintered body 1 discharged between the pair of molds 15a and 15b as described above is cooled (cooling step of tempering step S5). Specifically, as shown in FIG. 2, the iron-based sintered body 1 that has returned to the transport path 11 is transported to the downstream side, unloaded from the straightening device 10, and loaded into the cooling device 13. In the cooling device 13, it is cooled at a predetermined cooling rate to the temperature at the start of straightening (100 degrees or less, here normal temperature). This completes the tempering process for the iron-based sintered body 1. The iron-based sintered body 1 for which the tempering process has been completed is transported to the downstream side on the transport path 11 and is unloaded from the cooling device 13.

(S6) Finishing Step The iron-based sintered body 1 carried out from the cooling device 13 is conveyed to the finishing step S6 which is the next step. Then, in the finishing step S6, mechanical processing such as polishing and shot peening is performed, and the iron-based sintered body 1 is finished to have properties (for example, hardness, surface roughness, shape accuracy) suitable for the final product. .. As described above, many iron-based sintered bodies 1 are continuously manufactured.

As described above, according to the method for manufacturing an iron-based sintered body according to the present invention, the iron-based sintered body 1 in a state of less than 100 degrees is heated by the iron-based sintered body 1 in the straightening step S4. By restraining the molds 15a and 15b in a state where the temperature is higher than that, it is possible to obtain a straightening effect superior to the conventional one. When the iron-based sintered body 1 is held at a relatively low temperature and the dies 15a and 15b are heated to a relatively high temperature to restrain the iron-based sintered body 1, the temperatures of the dies 15a and 15b are changed. By controlling by the control unit 20, the tempering step S5, which is a heat treatment other than quenching, can be performed relatively easily at the same time as the straightening step S4. Therefore, it is possible to avoid the situation where the iron-based sintered body 1 is deformed again by the heat treatment after the quenching step S3, and to maintain excellent shape accuracy. As described above, according to the present invention, it is possible to obtain the iron-based sintered body 1 which is excellent in various mechanical characteristics and is excellent in shape accuracy.

In the present embodiment, the temperature of the iron-based sintered body 1 is room temperature, and the difference between the temperature of the molds 15a and 15b and the temperature of the iron-based sintered body 1 is 200 degrees or more. Since the sintered body 1 is constrained, a further excellent straightening effect can be obtained. In particular, it is effective when the iron-based sintered body 1 has a thin plate shape and a large amount of deformation occurs after the heat treatment, such as when a large amount of warpage occurs due to the quenching treatment.

In addition, in the present embodiment, a tempering step S5 for performing a tempering process on the iron-based sintered body 1 is further provided, and the iron-based sintered body 1 is heated by being restrained by the molds 15a and 15b of the straightening device 10. As a result, a tempering process was performed. As a result, the deformation of the iron-based sintered body 1 due to tempering can be corrected by the pair of molds 15a and 15b. Alternatively, the pair of molds 15a and 15b can suppress the deformation that should occur in the iron-based sintered body 1 due to the tempering. As a result, it is possible to provide the iron-based sintered body 1 with high shape accuracy even after the tempering step S5. Of course, the iron-based sintered body 1 can be subjected to the tempering treatment at the same time as the straightening treatment, which is also preferable from the viewpoint of productivity.

Although one embodiment of the present invention has been described above, the manufacturing method and the manufacturing apparatus for an iron-based sintered body according to the present invention can have configurations other than the above without departing from the spirit of the invention.

FIG. 4 is a flowchart showing a flow of a method for manufacturing an iron-based sintered body according to another embodiment of the present invention. As shown in FIG. 4, this manufacturing method differs from the manufacturing method shown in FIG. 1 in that a provisional sintering step S7 and a sintering and hardening step S8 are provided after the molding step S1. Specifically, in the present embodiment, in the molding step S1, a powder compact of a raw material powder containing iron-based powder as a main component is compacted, and then this compact is heated and subjected to temporary sintering treatment. In the temporary sintering step S7, the green compact is heated at a temperature lower than the sintering temperature set according to the material of the raw material powder (iron-based powder). As a result, the subsequent workability of the work (compacted powder compact) is improved. Next, in a sintering and quenching step S8, the green compact subjected to the temporary sintering treatment is heated to a predetermined temperature to be sintered, and is quenched by cooling after heating. As a result, the iron-based sintered body 1 that has been quenched is obtained.

Also in the present embodiment, in the correcting step S4, the iron-based sintered body 1 in a state of less than 100 degrees is restrained by the molds 15a and 15b in a state where the temperature is higher than that of the iron-based sintered body 1 by heating. As a result, it is possible to obtain a correction effect that is superior to the conventional one. When the iron-based sintered body 1 is held at a relatively low temperature and the dies 15a and 15b are heated to a relatively high temperature to restrain the iron-based sintered body 1, the temperatures of the dies 15a and 15b are changed. By controlling by the control unit 20, the tempering step S5 can be performed relatively easily at the same time as the straightening step S4. Therefore, it is possible to avoid the situation where the iron-based sintered body 1 is deformed again by the heat treatment after the sintering and quenching step S8, and to maintain excellent shape accuracy. As described above, also in the manufacturing method and the manufacturing apparatus according to the present embodiment, it is possible to obtain the iron-based sintered body 1 which is excellent in various mechanical characteristics and in shape accuracy. Further, as in the present embodiment, by performing the quenching treatment by utilizing the cooling as a part of the sintering treatment in the sintering and quenching step S8, the number of steps can be reduced, which is economical. ..

In the above description, the case where the quenching step S3 or the sintering and quenching step S8 is provided before the straightening step S4 is illustrated, but the application of the present invention is not limited to this. As a result, it is possible to perform the straightening step S4 according to the present invention on the iron-based sintered body of any property as long as it exhibits the same properties as the iron-based sintered body 1 in the quenched state.

Further, in the above description, in any of the embodiments, the case where the straightening step S4 and the tempering step S5 are performed at the same time has been illustrated, but the present invention can take other forms. In short, when the iron-based sintered body 1 is subjected to a heat treatment step other than the quenching step S3 (or the sintering and quenching step S8) and the tempering step S5, the heat treatment step may be performed simultaneously with the straightening step S4. In this case, at least a part of the heat treatment may be performed using the straightening device 10 shown in FIG. Of course, when it is not necessary to perform any heat treatment after quenching, only the straightening step S4 may be performed alone.

Further, in the above description, the temperature adjusting chamber 12 is provided adjacent to the straightening device 10 on the upstream side thereof, and the temperature of the iron-based sintered body 1 supplied to the straightening step S4 in the temperature adjusting chamber 12 is less than 100 degrees. However, the present invention is not limited to this form. For example, when the iron-based sintered body 1 has a distance large enough to be naturally cooled to or near room temperature between the apparatus related to the quenching step S3 and the straightening apparatus 10, the temperature control chamber 12 is especially provided. The temperature of the iron-based sintered body 1 may be set to less than 100° C. by natural cooling during conveyance between steps without providing.

Further, in the above description, the orthodontic device 10 is provided with the heating units 16a and 16b which are in contact with the pair of molds 15a and 15b, and the pair of molds 15a and 15b are heated by the heat generated by the heating units 16a and 16b. Although the case where the temperature is higher than the temperature of the iron-based sintered body 1 is illustrated, of course, other heating forms can be adopted. For example, the pair of molds 15a and 15b may be heated to a predetermined temperature by heating the atmosphere in the casing that covers the straightening device 10.

Further, when performing a heat treatment step other than quenching (for example, tempering step S5), in the above description, the heat treatment of the tempering step S5 is performed by the straightening apparatus 10, and the tempering is performed by the cooling apparatus 13 adjacent to the straightening apparatus 10. Although the case where the cooling process of step S5 is performed is illustrated, it is of course possible to take other forms. For example, the cooling units 19a and 19b of the straightening apparatus 10 shown in FIG. 3 may be used to cool the pair of molds 15a and 15b, whereby the cooling process of the tempering step S5 may be performed in the straightening apparatus 10. ..

Hereinafter, experimental results for demonstrating the correction effect according to the present invention will be described.

≪Test piece≫
In this example, a disk-shaped iron-based sintered body having a hole in the center was prepared and used as a test piece. The dimensions of all the test pieces were φ100 (outer diameter)×φ30 (inner diameter)×t6 (thickness dimension). The iron-based powder having the composition shown in Table 1 below was used as a raw material powder, which was pressed and then subjected to pre-sintering and sinter-quenching to produce an iron-based sintered body having the above size.

≪Test conditions≫
As the test device, the straightening device 10 shown in FIG. 3 was used. Further, as shown in Table 2, a plurality of types (three types in this case) of combinations of the temperature of the test piece and the temperature of the restraining mold were prepared, and the deformation amount before and after the correction in each case was measured. The amount of deformation referred to here is, as shown in FIG. 5, the outer diameter when the test piece 100 is placed such that the inner diameter side end 101 of the thin plate-shaped test piece 100 and the surface plate 103 are in contact with each other. It refers to the size of the gap h between the side end portion 102 and the surface plate 103. Further, the pressing force at the time of restraint was set to 80 tons, and the holding time (the time during which the pressing force at the time of restraint was continuously applied) was set to 5 minutes.

≪Test result≫
The results of the straightening test are shown in Table 2. As shown in Table 2, when the temperature of the test piece was high and the temperature of the mold was low (Comparative Example 4), the straightening effect could not be confirmed. Further, when the temperature of the test piece was high and the temperature of the mold was also high (Comparative Examples 1 to 3), a certain straightening effect was observed, but the larger the pre-straightening deformation amount of the test piece, the straightening effect. Was small. On the other hand, when the temperature of the test piece was less than 100 degrees and the temperature of the mold was high (Examples 1 to 5), a very excellent straightening effect was observed. Particularly when the pre-correction deformation amount was large (Examples 1 to 4), an extremely excellent correction effect was recognized. From the above, the usefulness of the present invention was proved.

1 Iron-based Sintered Body 10 Straightening Device 11 Conveying Path 12 Temperature Control Chamber 13 Cooling Devices 15a, 15b Molds 16a, 16b Heating Parts 16a1, 16b1 Heating Plates 16a2, 16b2 Cartridge Heater 17a Fixed Mold 17b Movable Molds 18a, 18b Insulation Parts 19a, 19b Cooling parts 19a1, 19b1 Cooling plates 19a2, 19b2 Cold water pipe 20 Control part 100 Test piece 101 Inner diameter side end 102 Outer diameter side end 103 Surface plate h Gap S1 Forming step S2 Sintering step S3 Quenching step S4 Straightening process S5 Tempering process S6 Finishing process S7 Temporary sintering process S8 Sinter hardening process

Claims (13)

Equipped with a straightening step for straightening the iron-based sintered body by restraining the iron-based sintered body obtained by compressing and sintering the raw material powder containing iron-based powder as a main component with a mold. In the method of manufacturing the iron-based sintered body,
In the correction step, the iron-based sintered body is restrained by the mold while the iron-based sintered body is less than 100 degrees and the mold is heated to a temperature higher than that of the iron-based sintered body. A method for manufacturing an iron-based sintered body, comprising: The method for producing an iron-based sintered body according to claim 1, wherein the difference between the temperature of the mold and the temperature of the iron-based sintered body is 200 degrees or more. The method for manufacturing an iron-based sintered body according to claim 1 or 2, wherein the temperature of the iron-based sintered body is room temperature. The method for producing an iron-based sintered body according to claim 1, wherein the temperature of the mold is less than 400 degrees. The method for producing an iron-based sintered body according to any one of claims 1 to 4, wherein the constraint time by the mold is set to 1 minute or more and 20 minutes or less. Further comprising a tempering step of performing a tempering process on the iron-based sintered body,
The method for manufacturing an iron-based sintered body according to any one of claims 1 to 5, wherein the tempering treatment is performed by heating the iron-based sintered body with restraint by the mold. Before the straightening step, a sintering step of sintering a powder compact formed by compression molding of the iron-based powder to obtain the iron-based sintered body, and a sintering step after the sintering step. The method for manufacturing an iron-based sintered body according to any one of claims 1 to 6, further comprising a quenching step of performing quenching treatment on the united body. Prior to the straightening step, a sintering and quenching step of heating the powder compact formed by compression molding of the iron-based powder to a predetermined temperature to sinter it, and performing quenching treatment by cooling after the heating. The method for manufacturing an iron-based sintered body according to any one of claims 1 to 6, further comprising: The method for producing an iron-based sintered body according to claim 1, wherein the iron-based powder contains iron as a main component and contains at least carbon. The method for manufacturing an iron-based sintered body according to claim 9, wherein the iron-based powder contains 0.3 wt% or more and 1.0 wt% or less of the carbon. The method for manufacturing an iron-based sintered body according to claim 1, wherein the iron-based sintered body has a thin plate shape. The method for manufacturing an iron-based sintered body according to claim 11, wherein the iron-based sintered body is a gear. An iron-based system having a straightening device for straightening the iron-based sintered body by constraining the iron-based sintered body obtained by compression-molding and sintering raw material powder containing iron-based powder as a main component In the sintered body manufacturing equipment,
The straightening device has a mold for restraining the iron-based sintered body, and a heating unit for heating the mold, and the straightening device sets the iron-based sintered body to less than 100 degrees, and The iron-based sintered body is configured to be capable of restraining the iron-based sintered body by the die while the die is heated to a temperature higher than that of the iron-based sintered body by heating of the heating unit. Equipment for manufacturing unions.

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