JP6504501B2 - Mesh belt type continuous sintering furnace and method of manufacturing sintered body - Google Patents

Description

  The present invention relates to a mesh belt type continuous sintering furnace used for manufacturing a sintered body, and a method for manufacturing a sintered body that can use the mesh belt type continuous sintering furnace. In particular, the present invention relates to a mesh belt type continuous sintering furnace in which a mesh belt has a long life.

  BACKGROUND ART A sintered body obtained by sintering a compact containing metal powder such as iron powder is used for automobile parts, general machine parts and the like. Types of these parts include, for example, sprockets, rotors, gears, rings, flanges, pulleys, bearings, and the like. The mesh belt furnace (mesh belt type continuous sintering furnace) is used for manufacture of a sintered compact (patent document 1).

  A conventional mesh belt type continuous sintering furnace 100 will be described with reference to FIG. The mesh belt type continuous sintering furnace 100 includes a preheating unit 11 for preheating a heating target (not shown), a sintering unit 13 for sintering a preheated heating target to produce a sintered body, and a sintered body. It has the cooling part 14 to cool, and the furnace main-body part 110 which conveys heating object and performs preheating * sintering * cooling continuously is provided. The conveyance of the heating target is performed by placing the heating target on the endless mesh belt 30 traveling from the inlet to the outlet of the furnace body 110. The mesh belt 30 is stretched around an inlet-side pulley 21 and an outlet-side pulley 22 respectively disposed on the inlet side and the outlet side of the furnace body portion 110. Using at least one of the inlet pulley 21 and the outlet pulley 22 as a drive pulley, the mesh belt 30 is caused to travel by the drive. Here, the outlet pulley 22 is a drive pulley (the direction of rotation is indicated by an arrow), and the inlet pulley 21 is a driven pulley. The mesh belt 30 that has exited the outlet of the furnace body 110 passes under the furnace body 110 and returns to the inlet of the furnace body 110. In the vicinity of each of the inlet side pulley 21 and the outlet side pulley 22, tension pulleys 211 and 221 for adjusting the tension of the mesh belt 30 are provided.

Japanese Utility Model Publication No. 05-94695

  It is desirable to increase the life of mesh belts. Since the mesh belt travels in the sintering furnace with the object to be heated loaded, it is exposed to a very severe environment in addition to the application of a large load and tension. Because the mesh belt is stretched mainly by high temperature creep under the influence, the mesh belt's elongation is checked regularly as maintenance of the mesh belt, and the mesh belt is cut and joined whenever predetermined elongation occurs. ing. When the extension margin of the mesh belt reaches a limit, it is necessary to replace the mesh belt itself. These maintenance and replacement operations are very complicated.

  The present invention has been made in view of the above-mentioned circumstances, and one of the objects thereof is to provide a mesh belt type continuous sintering furnace having a long mesh belt life.

  Another object of the present invention is to provide a method for producing a sintered body which can utilize the mesh belt type continuous sintering furnace.

  A mesh belt type continuous sintering furnace according to an aspect of the present invention is stretched between a furnace main body having a preheating part, a sintering part, and a cooling part, and an inlet-side pulley and an outlet-side pulley of the furnace main body, And an endless mesh belt which travels from the inlet to the outlet of the furnace body to convey the object to be heated. The mesh belt type continuous sintering furnace has a tension dividing mechanism for dividing a section where a predetermined tension acts on the mesh belt between the inlet side and the outlet side between the inlet end of the preheating unit and the outlet end of the sintering unit. Prepare.

  The method for producing a sintered body according to one aspect of the present invention is a method for producing a sintered body in which the steps of preheating, sintering, and cooling are sequentially applied to a molded body conveyed from the upstream side to the downstream side by a traveling belt. In the traveling belt, a section in which a predetermined tension acts on the traveling belt is divided into the upstream side and the downstream side within the range corresponding to the start end of the preheating step to the end of the sintering step to convey the formed body Do.

  The mesh belt continuous sintering furnace has a long mesh belt life.

  The manufacturing method of the said sintered compact can manufacture the sintered compact which is excellent in surface characteristics with sufficient productivity.

1 is a schematic view showing a mesh belt type continuous sintering furnace according to Embodiment 1. FIG. It is the schematic which shows the conventional mesh belt-type continuous sintering furnace.

Description of the embodiment of the present invention
The present inventors focused on the high temperature creep of the mesh belt in order to achieve the long life of the mesh belt. Specifically, the high temperature of the mesh belt in the vicinity of the position of the highest temperature in the sintered portion where the high temperature creep seems to be most likely to occur during the manufacturing process of the sintered body from the preheating to the cooling. We investigated the reduction of creep. As a result, it has been found that the high temperature creep is greatly influenced by the length between the position where the mesh belt is at the maximum temperature and the position of the upstream pulley closest to that position. The "maximum temperature position" refers to the position where the maximum temperature is at the maximum temperature in the temperature distribution in the longitudinal direction of the mesh belt, and for a predetermined length. When there is a range that reaches the maximum temperature, it refers to the most downstream position in the range. In the following description, the “maximum position” and the “most downstream position” may be collectively referred to as a maximum temperature end point T. For example, the maximum temperature end point T is shown at the center in the transport direction of the sintered portion 13 in FIG. 2 described above for convenience of explanation (this point is the same in FIG. 1 described later). And if the distance between the highest temperature end point T and the closest pulley on the upstream side (hereinafter sometimes referred to as the heating belt section L) can be shortened, the load acting on the heating belt section L can be reduced, and the mesh belt It was found that the elongation accompanying high temperature creep can be significantly suppressed. The present invention is based on these findings. First, the contents of the embodiment of the present invention will be listed and described.

  (1) The mesh belt type continuous sintering furnace according to one aspect of the present invention is stretched by a furnace main body having a preheating part, a sintering part, and a cooling part, and an inlet pulley and an outlet side pulley of the furnace main body. And an endless mesh belt which travels from the inlet to the outlet of the furnace body to convey the object to be heated. The mesh belt type continuous sintering furnace has a tension dividing mechanism for dividing a section where a predetermined tension acts on the mesh belt between the inlet side and the outlet side between the inlet end of the preheating unit and the outlet end of the sintering unit. Prepare.

  According to the above configuration, high temperature creep deformation of the mesh belt can be easily suppressed, and the life of the mesh belt can be extended. Therefore, the number of maintenance of the mesh belt and the number of replacement of the mesh belt can be reduced. By dividing the section in which the predetermined tension acts on the mesh belt by the tension dividing mechanism, the section can be shortened compared to the prior art. The tensions of the mesh belts in the sections separated by this division do not substantially affect each other, and are independent of each other. That is, since the length of the mesh belt acting on its own weight can be shortened, the load of the object to be heated placed in the shortened area can also be smaller than the load of the object to be placed on the mesh belt before division.

  Moreover, according to said structure, it is easy to improve the productivity of a sintered compact. The tension of the mesh belts in the divided sections can be made independent of each other, and the section in which the predetermined tension acts on the mesh belt can be shortened, so that the stress acting on the mesh belt can be reduced, and it is easy to stack and convey. Therefore, single-stage conveyance to multi-stage stacking, or the number of multi-stage stacking can be increased, and a larger number of heating targets can be sintered at one time.

  Furthermore, according to said structure, it is easy to manufacture the sintered compact which is excellent in the surface characteristic without wrinkles and rough skin. Conventionally, a series of sections where the predetermined tension acts on the mesh belt is very long in a section from the inlet-side pulley to the maximum temperature end point T of the sintering portion. If the preheating unit is made longer, the series section becomes longer, so there is a possibility that the frequency of maintenance and replacement of the mesh belt may become excessive, and the preheating unit could not be made longer. On the other hand, the tension of the mesh belts in the divided sections is made independent of each other to shorten the section in which the predetermined tension acts on the mesh belt, whereby the length of the preheating portion can be increased. Therefore, the heating target can be sufficiently preheated because the length (time) of preheating can be taken longer than before. In particular, when the object to be heated includes a lubricant, the lubricant can be sufficiently removed, so it is easier to manufacture a sintered body having excellent surface properties.

  (2) As one mode of the mesh belt type continuous sintering furnace, the tension dividing mechanism is provided between the preheating part and the sintering part.

  According to the above configuration, the section of the mesh belt on which a predetermined tension acts can be divided into the preheating part side and the sintering part side of different treatments, so that the life of the mesh belt can be extended and the productivity of the sintered body can be increased. It is easy to achieve, at a high level, the production of a sintered body excellent in the improvement of the surface quality. In addition, since the temperature range to be controlled differs between the preheating unit and the sintering unit, normally, there are many differences in configuration such as the heating means and the heat insulating material, and it is between the preheating unit and the sintering unit It is easy to form a tension dividing mechanism.

  (3) As one mode of the mesh belt type continuous sintering furnace, the tension dividing mechanism may include an intermediate conveyance mechanism which conveys the object to be heated on the tangent line connecting the inlet side pulley and the outlet side pulley.

  According to the above configuration, by providing the intermediate conveyance mechanism, it is possible to suppress that the heating object deviates from the conveyance path at the position of the tension dividing mechanism, and the heating object is substantially linear from the inlet to the outlet of the furnace body. Can be transported to

  (4) As one form of the mesh belt type continuous sintering furnace, when the tension dividing mechanism includes an intermediate conveyance mechanism, the intermediate conveyance mechanism includes an intermediate drive pulley for bridging the mesh belt with the inlet pulley and an outlet. And providing an intermediate driven pulley for bridging the mesh belt with the side pulley. At this time, the mesh belt has a slack portion formed between the intermediate drive pulley and the intermediate driven pulley.

  According to the above configuration, the mesh belt on the upstream side of the tension splitting mechanism is driven such that the intermediate drive pulley separates the mesh belt on the downstream side of the tension splitting mechanism and the tension acts. And, due to the slack portion of the mesh belt, the tension of the mesh belt between the inlet side pulley and the intermediate drive pulley and the tension of the mesh belt between the intermediate driven pulley and the outlet side pulley substantially affect each other Can be independent of each other. Therefore, the tension dividing mechanism can be configured with a simple configuration.

  (5) As one form of the mesh belt type continuous sintering furnace, when the intermediate conveyance mechanism includes an intermediate drive pulley and an intermediate driven pulley, the intermediate drive pulley and the intermediate driven pulley mutually extend in the conveying direction of the object to be heated. It may be placed at a larger interval than At this time, the intermediate conveyance mechanism is provided with a conveyance roll which is disposed so as to fill the gap without bridging the mesh belt, and conveys the object to be heated from the intermediate drive pulley to the intermediate driven pulley.

  According to the above configuration, as compared to the case where the intermediate drive pulley and the intermediate driven pulley are disposed at an interval smaller than the length in the transfer direction of the heating target, the intermediate drive according to the length in the transfer direction of the heating target Less restriction on pulley diameter. The term "interval" as used herein refers to the axis of the pulley. When the two pulleys are disposed at an interval smaller than the length in the transport direction of the heating object, the diameters of the two pulleys are the heating object in order to prevent the heating object from falling off or greatly tilting between the two pulleys. Constrained by the above length of On the other hand, according to the above configuration, for example, the diameter of the intermediate drive pulley can be increased regardless of the length of the heating target. In that case, if the diameter of the transport roll is adjusted, the object to be heated can be easily transported without being inclined between the pulleys.

  (6) As one form of the mesh belt type continuous sintering furnace, when the intermediate conveyance mechanism includes an intermediate drive pulley and an intermediate driven pulley, the intermediate drive pulley and the intermediate driven pulley mutually extend in the conveying direction of the heating target Are placed at smaller intervals.

  According to the above configuration, the intermediate drive pulley and the intermediate driven pulley are disposed at an interval greater than the length in the conveyance direction of the heating target, and the intermediate drive pulley to the intermediate are compared with the case where the conveyance roll is provided. It is easy to shorten the length of the transport path to the driven pulley. Therefore, the temperature of the object to be heated does not easily decrease in the process of conveyance from the intermediate drive pulley to be heated to the intermediate driven pulley. Therefore, it is easy to sinter the object to be heated easily in the sintering section, and it is easy to manufacture a sintered body excellent in surface properties free from wrinkles and rough surfaces.

  (7) As one form of the mesh belt type continuous sintering furnace, when the tension dividing mechanism includes the intermediate conveyance mechanism and the slack portion of the mesh belt, the intermediate conveyance mechanism is further hooked on the slack portion of the mesh belt And a tension pulley for adjusting the tension of the mesh belt.

  According to the above configuration, the frictional resistance between the intermediate drive pulley and the mesh belt can be adjusted, and the traveling of the mesh belt can be easily adjusted. In addition, it is easy to adjust the length of the slack portion of the mesh belt.

  (8) As one mode of the mesh belt type continuous sintering furnace, the tension dividing mechanism may be provided with an auxiliary heater for keeping the object to be heated warm.

  According to the above configuration, the heating target can be kept warm in the conveyance process of the heating target from the upstream to the downstream of the tension splitting mechanism. Therefore, even if the tension dividing mechanism may be elongated due to the configuration of the tension dividing mechanism (for example, the size of the intermediate drive pulley), it is possible to suppress the temperature decrease of the heating target in the conveyance process of the tension dividing mechanism. Therefore, it is easy to sinter the object to be heated easily in the sintering section, and it is easy to manufacture a sintered body excellent in surface properties free from wrinkles and rough surfaces.

  (9) A method of manufacturing a sintered body according to an aspect of the present invention is a sintered body in which the steps of preheating, sintering, and cooling are sequentially performed on a molded body conveyed from the upstream side to the downstream side by a traveling belt. A manufacturing method, in which a section of a traveling belt, in which a predetermined tension acts on the traveling belt, is divided into an upstream side and a downstream side within a range corresponding to the start end of the preheating step to the end of the sintering step. Transport the body.

  According to said structure, the sintered compact which is excellent in surface property can be manufactured with sufficient productivity. By dividing the section in which the predetermined tension acts on the traveling belt into the upstream side and the downstream side, the load on the traveling belt can be reduced and the high temperature creep characteristics can be improved. And it is easy to slow the temperature rising rate of preheating. By being able to slow the temperature rising rate of preheating, the length (time) of preheating can be taken longer than before, and the temperature rise of the molded body can be smoothed. Thus, when the object to be heated includes a lubricant, it is easy to sufficiently remove the lubricant.

  (10) As one form of the manufacturing method of the said sintered compact, carrying out the multistage piling up of several molded objects and conveying it is mentioned.

  According to the above configuration, the productivity of the sintered body can be enhanced. The long life of the traveling belt makes it easy to stack in multiple stages, and a large number of sintered bodies can be sintered at one time.

  (11) As one form of the manufacturing method of the said sintered compact, it is mentioned that the temperature increase rate of preheating is 40 degrees C / min or less.

  According to said structure, it is easy to manufacture the sintered compact which is excellent in surface characteristics. As described above, since it is possible to divide the section in which the predetermined tension acts on the traveling belt, the length (time) of preheating can be taken longer than in the prior art, the temperature raising rate can be 40 ° C./min or less. As a result, the temperature rise of the molded body can be smoothed. The preheating time can be, for example, 15 minutes or more. Then, when the object to be heated includes a lubricant, the lubricant can be sufficiently removed, and a sintered body free from surface stains, wrinkles, rough skin and the like can be manufactured.

<< Details of the Embodiment of the Present Invention >>
The details of the embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1
The mesh belt type continuous sintering furnace 1 according to the first embodiment will be described with reference to FIG. The mesh belt type continuous sintering furnace 1 according to the first embodiment includes a furnace main body 10 and an endless mesh belt 30. A point where the furnace body 10 has the preheating part 11, the sintering part 13, and the cooling part 14, and the mesh belt 30 is stretched over the inlet side pulley 21 and the outlet side pulley 22 of the furnace body 10, The point of traveling from the inlet to the outlet of the main body 10 to convey the heating target (not shown) is the same as that of the conventional mesh belt continuous sintering furnace 100 described with reference to FIG. The main feature of the mesh belt continuous sintering furnace 1 according to the first embodiment is that a predetermined tension acts on the mesh belt 30 between the inlet end of the preheating unit 11 and the outlet end of the sintering unit 13. The point is that the tension dividing mechanism 12 is provided to divide the section into the inlet side and the outlet side. That is, in the mesh belt type continuous sintering furnace 1 according to the first embodiment, the configuration of the furnace main body 10 is different from the furnace main body 110 of the conventional mesh belt type continuous sintering furnace 100, the following description is different Mainly About the same composition as conventional, the same numerals as FIG. 2 are attached, and the explanation is omitted. Then, the manufacturing method of the sintered compact using this mesh belt-type continuous sintering furnace 1 is demonstrated.

[Overall overview]
The furnace main body 10 is placed on the mesh belt 30 and performs preheating, sintering, and cooling on a heating target (not shown) conveyed by the movement of the mesh belt 30. The mesh belt 30 travels by driving at least one of the inlet pulley 21 and the outlet pulley 22 as a drive pulley. Here, the outlet pulley 22 is a drive pulley (the direction of rotation is indicated by an arrow), and the inlet pulley 21 is a driven pulley. The mesh belt 30 that has exited the outlet of the furnace body 10 passes under the furnace body 10 and is returned to the inlet of the furnace body 10. In the vicinity of each of the inlet side pulley 21 and the outlet side pulley 22, tension pulleys 211 and 221 for adjusting the tension of the mesh belt 30 are provided.

[Tension breaking mechanism]
The tension dividing mechanism 12 divides a section in which a predetermined tension acts on the mesh belt 30 between the inlet end of the preheating unit 11 and the outlet end of the sintering unit 13 into an inlet side and an outlet side. The tensions of the mesh belts 30 in the sections divided by the tension dividing mechanism 12 do not substantially affect each other, and are independent of each other. That is, the section in which the tension acts independently on the mesh belt 30 can be shortened. In particular, the length (hereinafter, the heating belt section L) between the maximum temperature end point T and the pulley closest to the upstream side can be shortened as compared with the related art. Although the maximum temperature end point T is shown at the center in the transport direction of the sintering unit 13 for convenience of explanation in FIG. 1, it may actually be different. Thereby, since the stress acting on the mesh belt 30 can be reduced, high temperature creep deformation of the mesh belt 30 can be suppressed, and the life of the mesh belt 30 can be extended. The installation location of the tension dividing mechanism 12 can be theoretically provided in the middle of the preheating unit 11 or in the middle of the sintering unit 13 (in particular, on the upstream side of the maximum temperature end point T). It is provided between the sintered part 13 and the like. The tension dividing mechanism 12 of this example includes an intermediate conveyance mechanism 120 for conveying a heating target on a tangent connecting the inlet pulley 21 and the outlet pulley 22 and a slack portion 31 of the mesh belt 30 formed by the intermediate conveyance mechanism 120. And

(Intermediate conveyance mechanism)
The intermediate conveyance mechanism 120 includes an intermediate drive pulley 121 for bridging the mesh belt 30 with the inlet-side pulley 21 and an intermediate driven pulley 122 for bridging the mesh belt 30 with the outlet-side pulley 22.

<Intermediate drive pulley>
The intermediate drive pulley 121 is upstream of the tension dividing mechanism 12 (on the preheating unit 11 side) so that tension is applied by dividing the mesh belt 30 on the downstream side (sintered portion 13 side) of the tension dividing mechanism 12. ) Is driven. The intermediate drive pulley 121 forms a slack portion 31 of the mesh belt 30 described later.

  The diameter and the number of the intermediate drive pulleys 121 are not particularly limited as long as they can ensure a predetermined contact length (frictional resistance) with the mesh belt 30, and can be selected appropriately. The larger the diameter of the intermediate drive pulley 121, the larger the contact length (frictional resistance) with the mesh belt 30 as the diameter of the intermediate drive pulley 121 is larger, but if too large, the transport path from the preheating unit 11 to the sintering unit 13 tends to be long. There is a possibility that the temperature of the object to be heated may drop during this transport process. For example, when the diameter of the intermediate drive pulley 121 is large, the number can be one, or when the diameter of the intermediate drive pulley 121 is small, the number can be plural.

<Intermediate driven pulley>
The intermediate driven pulley 122 spans the downstream side of the slack portion 31 of the mesh belt 30 and conveys the mesh belt 30 along the surface of the sintering portion 13. The diameter of the intermediate driven pulley 122 may be smaller than the diameter of the intermediate drive pulley 121. Unlike the intermediate drive pulley 121, the intermediate driven pulley 122 does not have to secure frictional resistance with the mesh belt 30. If the diameter of the intermediate driven pulley 122 is smaller than the diameter of the intermediate drive pulley, it is easy to make the mesh belt 30 travel by reducing the frictional resistance with the mesh belt 30. Moreover, since the conveyance path from the preheating unit 11 to the sintering unit 13 can be easily shortened, it is easy to suppress the temperature drop of the heating target in the conveyance process.

  The arrangement relationship between the intermediate drive pulley 121 and the intermediate driven pulley 122 is (1) arranged at a distance larger than the length in the transfer direction of the heating object, or (2) smaller than the length in the transfer direction of the heating object It can be mentioned that The length in the transport direction of the heating target is the length of the transport unit that behaves integrally, and when the individual heating target (molded body) is directly placed on the mesh belt 30, the heating target (molding When the body is a length of itself and a plurality of heating targets (formed bodies) are arranged in a tray and the tray is placed on the mesh belt 30, the length is the length of the tray. This spacing refers to the length between the axes of the two pulleys 121, 122. In the case of (1), the intermediate conveyance mechanism further includes a conveyance roll 123 (described later) disposed so as to fill the gap so that the heating object is not dropped between the two pulleys 121 and 122. Be When setting it as said (2), it is thought that it is preferable to set the space | interval to half or less of the length of the conveyance direction of heating object. This is because the intermediate driven pulley 122 can support the object to be heated before tilting between the two pulleys 121 and 122. Here, the intermediate drive pulley 121 and the intermediate driven pulley 122 are disposed at a distance greater than the length in the conveyance direction of the heating target, and the conveyance roll 123 is provided therebetween.

<Conveying roll>
The transport roll 123 is disposed so that the mesh belt 30 is not bridged and fills the gap between the two pulleys 121 and 122, and transports the object to be heated from the intermediate drive pulley 121 to the intermediate driven pulley 122. As a result, even if the arrangement relationship between the intermediate drive pulley 121 and the intermediate driven pulley 122 is arranged at a distance larger than the length in the conveyance direction of the heating object, the heating object falls off between the two pulleys 121 and 122, It does not tilt greatly. The number of transport rolls 123 can be appropriately selected according to the size and the length of the above-described interval, and is herein plural. The transport roll 123 is a driven roll in this example, but may be a drive roll.

<Others>
The intermediate conveyance mechanism 120 preferably includes a tension pulley 124 which is hung on the slack portion 31 of the mesh belt 30 to adjust the tension of the mesh belt 30. The intermediate conveyance mechanism 120 may include an idler pulley 125 in addition to the tension pulley 124, but the idler pulley 125 may be omitted.

  The tension pulley 124 adjusts the contact length (frictional resistance) between the intermediate drive pulley 121 and the mesh belt 30 in the circumferential direction. By adjusting the contact length, tension of the mesh belt 30 between the inlet side pulley 21 and the intermediate drive pulley 121 is applied independently of the mesh belt 30 between the outlet side pulley 22 and the intermediate driven pulley 121. The adjustment of the contact length can be performed by adjusting the position of the tension pulley 124. In addition, the tension pulley 124 also contributes to the adjustment of the length of the slack portion 31 of the mesh belt 30. Here, the tension pulley 124 is hung on the upstream side of the slack portion 31.

  The idler pulley 125 defines a slack amount of the slack portion 31 of the mesh belt 30 and a traveling path to the intermediate driven pulley 122 of the mesh belt 30. That is, the amount of slack of the slack portion 31 and the travel path of the mesh belt 30 are based on the position of the idler pulley 125. Here, the idler pulley 125 is provided between the tension pulley 124 and the intermediate driven pulley 122.

  The pulley at the position of the tension pulley 124 in FIG. 1 may also be a plurality of intermediate drive pulleys as a drive. In that case, the pulley at the position of the idler pulley 125 may be a tension pulley.

(Auxiliary heater)
The tension dividing mechanism 12 may be provided with an auxiliary heater 126 (indicated by a two-dot chain line) for keeping the heating object conveyed from the preheating unit 11 warm. The periphery of the conveyance path to be heated in the tension dividing mechanism 12 is covered with a heat insulating material. Therefore, if the temperature drop of the object to be heated by the tension dividing mechanism 12 is small, the auxiliary heater 126 is unnecessary and only the heat insulator may be used. However, depending on, for example, the size of the intermediate drive pulley 121 or the length of the interval between the intermediate drive pulley 121 and the intermediate driven pulley 122, the length between the preheating portion 11 and the sintering portion 13 may be long. . If the auxiliary heater 126 is provided, even if the length between the preheating unit 11 and the sintering unit 13 is increased as described above, the temperature of the preheated heating target is from the preheating unit 11 to the sintering unit 13 It is possible to suppress the temperature falling below a predetermined temperature in the transport process.

(Sag part)
The slack portion 31 of the mesh belt 30 divides a section in which a predetermined tension acts on the mesh belt 30 at the upstream side and the downstream side. By this division, the heating belt section L can be made a length L1 (FIG. 1) from the maximum temperature end point T to the intermediate driven pulley 122, and a length L2 from the maximum temperature end point T to the inlet side pulley 21 (FIG. Can be shorter than the conventional heating belt section L). Moreover, the tension of the mesh belt 30 between the inlet pulley 21 and the intermediate drive pulley 121 and the tension of the mesh belt 30 between the intermediate driven pulley 122 and the outlet pulley 22 due to the presence of the slack portion 31. Are substantially independent of each other and do not affect each other. Thereby, since the stress acting on the mesh belt 30 in the sintered portion 13 can be reduced, high temperature creep deformation of the mesh belt 30 can be suppressed, and the life of the mesh belt 30 can be prolonged.

[Function and effect of mesh belt type continuous sintering furnace]
According to the mesh belt type continuous sintering furnace 1 according to the embodiment described above, a section in which a predetermined tension acts on the mesh belt 30 by the tension dividing mechanism 12 between the preheating unit 11 and the sintering unit 13 Can be divided. Due to the division, the heating belt section L is made shorter than before, and the tension acting on the mesh belt 30 on the preheating portion 11 side and the mesh belt 30 on the sintering portion 13 side does not substantially affect each other. , Become independent of each other. As a result, the mesh belt type continuous sintering furnace 1 can exhibit the following effects.

  (1) Since the high temperature creep deformation of the mesh belt 30 can be suppressed, the life of the mesh belt 30 can be extended. Therefore, the number of times of maintenance of the mesh belt 30 and the number of times of replacement of the mesh belt 30 can be reduced.

  (2) It is easy to stack the heating targets in multiple stages for transportation, and it is easy to sinter a large number of heating targets at once, so it is easy to increase the productivity of the sintered body.

  (3) The length of the preheating section 11 can be made longer, and the heating object can be sufficiently preheated because the length (time) of preheating can be taken longer than before, so a sintered body excellent in surface properties free from wrinkles and rough surfaces Easy to manufacture.

[Method of manufacturing sintered body]
In the method of manufacturing a sintered body, the steps of preheating, sintering, and cooling are sequentially performed on a molded body conveyed from the upstream side to the downstream side by the traveling belt. The main feature of the manufacturing method of this sintered body is that, of the traveling belt, a section in which a predetermined tension acts on the traveling belt within the range corresponding to the start end of the preheating step to the end of the sintering step. And the downstream side, and it is in the point which conveys a forming object. In the following description, after the outline of the formed body to be heated is described, conveyance of the formed body, preheating, sintering, and cooling will be described in order. Here, the mesh belt type continuous sintering furnace 1 described above is used to manufacture a sintered body, and the mesh belt 30 corresponds to the traveling belt.

(Molded body)
The formed body to be heated is, for example, a material of a machine part manufactured into a product through sintering described later. Examples of types of mechanical parts include sprockets, oil pump rotors, gears, rings, flanges, and pulleys. The molded body is formed by compression molding of a raw material powder containing a metal powder. The type of metal powder can be appropriately selected according to the type of the above-mentioned machine part, and examples thereof include iron and iron alloys containing iron as a main component. The molded body preferably contains a lubricant. As described above, when the raw material powder is compression-molded to produce a molded body, when the raw material powder contains a lubricant, the lubricity at the time of molding is enhanced and the moldability is improved. The shape / size of the molded body is the shape / size along the final shape of the machine component.

(Transport)
The formed body is conveyed to the above-described furnace body portion 10. The conveyance of the formed body to the furnace main body 10 is performed by being placed on the mesh belt 30 described above. The formed body may be placed directly on the mesh belt 30, or a tray on which the formed body is placed may be placed. When transporting a plurality of compacts, the plurality of compacts may be transported without being stacked on the mesh belt 30, but a plurality of compacts may be stacked on the mesh belt 30 and transported. The mesh belt type continuous sintering furnace 1 can shorten the section in which the predetermined tension acts on the mesh belt 30 as described above, and can reduce the stress acting on the mesh belt 30. Stacking in multiple stages can increase the productivity of the sintered body. Multi-stage stacking of molded bodies can be performed by adsorbing the molded bodies with an electromagnet, a vacuum pad or the like, or gripping with a manipulator such as a robot hand.

  The conveyance of the molded body is performed by dividing the section in which a predetermined tension acts on the mesh belt 30 into the upstream side and the downstream side. Since the mesh belt type continuous sintering furnace 1 described above is used, the division of the section acting on the mesh belt 30 is performed between the preheating unit 11 and the sintering unit 13 with the intermediate drive pulley 121 and the slack portion 31 of the mesh belt 30. To do.

(Preheating)
The compact is heated before sintering. The lubricant contained in the compact can be removed by raising the temperature of the compact above a certain level by this preheating. As a result, when the molded body is sintered, wrinkles and rough surfaces are less likely to occur, and it is easy to produce a sintered body excellent in surface properties. This preheating is performed by the above-described preheating unit 11. The preheating temperature can be appropriately selected according to the material of the lubricant contained in the molded body, and may be, for example, 300 ° C. or more, and further 500 ° C. or more. The preheating temperature is, for example, 730 ° C. or less, and further 700 ° C. or less.

  The temperature rising rate by preheating can be made slower because the length of the preheating unit 11 can be increased. The reason that the length of the preheating unit 11 can be made longer is that the section where the predetermined tension acts on the mesh belt 30 can be made shorter than in the prior art by providing the tension dividing mechanism 12 and the tension dividing mechanism 12 is not provided. It is because the tension which acts on mesh belt 30 can be made small by comparison. By slowing the temperature rising rate, the temperature rise of the molded body can be smoothed, and it is easy to produce a sintered body excellent in surface properties without surface roughness. The temperature rising rate can be, for example, 40 ° C./min or less. The temperature rising rate may be, for example, 10 ° C./min or more. If so, it is easy to suppress the fall of productivity of a sintered compact. Further, the temperature rising rate may be 30 ° C./min or less.

(Sintering)
The compact is sintered to produce a sintered body. This sintering is performed by the above-mentioned sintered part 13. The sintering temperature can be appropriately selected according to the material of the molded body, and in the case of an iron-based sintered body, for example, 1000 ° C. or more, and further 1100 ° C. or more can be mentioned. The upper limit of the sintering temperature depends on the heat resistance of the mesh belt 30, but may be, for example, 1160 ° C. or less. The sintering time may be about 20 minutes to 150 minutes.

(cooling)
Cool the sintered body. Since the temperature of the sintered body immediately after being sintered is very high, the sintered body is cooled to lower its temperature. This cooling is performed by the cooling unit 14. Cooling includes, for example, blowing the coolant gas into the cooling unit 14. For example, nitrogen gas can be used as the refrigerant gas.

[Operation effect of the manufacturing method of a sintered compact]
According to the above-described method for producing a sintered body, a plurality of compacts can be stacked and transported in multiple stages, or the temperature rising rate for preheating can be reduced, and a sintered body excellent in surface properties can be produced with good productivity. It can be manufactured.

The present invention is not limited to these exemplifications, but is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims .

  A mesh belt type continuous sintering furnace and a method of manufacturing a sintered body according to one aspect of the present invention are various general structural parts (sprockets, rotors, gears, rings, flanges, pulleys, bearings such as machine parts, etc. Can be suitably used for the production of joint parts).

Reference Signs List 1, 100 mesh belt type continuous sintering furnace 10, 110 furnace main body 11 preheating unit 12 tension dividing mechanism 120 intermediate conveyance mechanism 121 intermediate drive pulley 122 intermediate driven pulley 123 conveyance roll 124 tension pulley 125 idler pulley 126 auxiliary heater 13 sintering Part 14 Cooling part 21 Inlet side pulley 22 Outlet side pulley 211, 221 Tension pulley 30 Mesh belt 31 Slack part

Claims (10)

A furnace main body having a preheating part, a sintering part and a cooling part, and an inlet-side pulley and an outlet-side pulley of the furnace main body are stretched and run from the inlet to the outlet of the furnace main body to be heated A mesh belt type continuous sintering furnace comprising an endless mesh belt for conveying,
It provided between the sintered part and the preheating section, a mesh belt type continuous sintering furnace comprising a tension cutting mechanism for cutting a section predetermined tension is applied to the mesh belt and the inlet side and the outlet side. The mesh belt type continuous sintering furnace according to claim 1, wherein the tension dividing mechanism includes an intermediate transfer mechanism which transfers the heating target on a tangent line connecting the inlet-side pulley and the outlet-side pulley. The intermediate transport mechanism
An intermediate drive pulley for bridging the mesh belt with the inlet pulley;
An intermediate driven pulley for bridging the mesh belt with the outlet pulley;
The mesh belt type continuous sintering furnace according to claim 2 , wherein the mesh belt has a slack portion formed between the intermediate drive pulley and the intermediate driven pulley. The intermediate drive pulley and the intermediate driven pulley are disposed at an interval greater than the length in the transport direction of the heating target.
The intermediate transfer mechanism, wherein the mesh belt is disposed so as to fill the gap without being bridged, according to claim 3, further comprising a transport roll for conveying the heating object from the intermediate drive pulley on said intermediate driven pulley Mesh belt type continuous sintering furnace. The mesh belt type continuous sintering furnace according to claim 3 , wherein the intermediate drive pulley and the intermediate driven pulley are disposed at an interval smaller than a length in a conveyance direction of the heating target. The mesh belt-type continuous burning according to any one of claims 3 to 5 , wherein the intermediate conveyance mechanism includes a tension pulley which is hung on the slack portion of the mesh belt to adjust the tension of the mesh belt. Furnace. The mesh belt type continuous sintering furnace according to any one of claims 1 to 6 , wherein the tension dividing mechanism is provided with an auxiliary heater for keeping the temperature of the heating object warm. A method for producing a sintered body, which sequentially performs the steps of preheating, sintering, and cooling on a molded body conveyed from the upstream side to the downstream side by a traveling belt,
In the traveling belt, a section in which a predetermined tension acts on the traveling belt between the end of the preheating step and the beginning of the sintering step is divided into an upstream side and a downstream side to carry the formed body Method of producing a body The method for producing a sintered body according to claim 8 , wherein a plurality of the compacts are stacked and transported in multiple stages. Method for producing a sintered body according to claim 8 or claim 9 heating rate of the preheating is not more than 40 ° C. / min.

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