JP5968735B2 - Lower punch used for forming a ferrite magnet in a magnetic field, and method for manufacturing the lower punch - Google Patents

Description

  The present invention relates to a structure of a lower punch used for forming a ferrite magnet in a magnetic field.

  Conventionally, a forming method in a magnetic field as described in Patent Documents 1 and 2 is known as a forming method of a ferrite magnet. In this method, magnetic powder is injected into a cavity of a mold, and pressure molding is performed while applying a magnetic field to the mold. An anisotropic ferrite magnet is obtained by sintering a molded body obtained thereby. be able to.

  This type of mold includes a die formed with an insertion hole (form frame as described in Patent Document 1), and a lower punch (second punch as referred to in Patent Document 1) that can slide in the insertion hole. And an upper punch (first punch as referred to in Patent Document 1) disposed to face the lower punch. A space surrounded by the inner wall surface of the insertion hole formed in the die, the lower punch, and the upper punch becomes a cavity. Magnetic powder is injected into the cavity, a lower punch is advanced into the cavity to pressurize the magnetic powder, and a desired magnetic field is generated in the cavity to perform molding.

  The shape of the magnetic field generated in the cavity (direction of the lines of magnetic force) is affected by the magnetic material through which the magnetic field passes. In a conventional mold in a magnetic field, a lower punch and an upper punch are made of a magnetic material, and a desired magnetic field is formed in the cavity by devising the shapes of the lower punch and the upper punch. However, the lower punch and the upper punch are molds for molding the magnetic powder, and need to have a shape suitable for molding. For this reason, the freedom degree of a shape of a lower punch and an upper punch is low, and there is little room to devise a shape in order to form a magnetic field.

  Therefore, a configuration has been proposed in which the lower punch (and upper punch) is a combination of two types of materials, a magnetic material and a non-magnetic material. Such a configuration is described in Patent Document 1, for example. The lower punch (second punch) described in Patent Document 1 is composed of a ferromagnetic material and a non-magnetic material. In Patent Document 1, a nonmagnetic material has a molding surface for molding magnetic powder. The ferromagnetic material is bonded to the non-magnetic material on the opposite side of the molding surface. Moreover, in patent document 1, the ferromagnetic material has the convex part which protrudes toward a nonmagnetic material. If the lower punch is configured in this way, the shape of the convex portion of the ferromagnetic material can be set relatively freely, so that an ideal magnetic field can be generated in the cavity.

  In the lower punch configured as in Patent Document 1, a non-magnetic part is exposed inside the cavity, and the surface (molding surface) of the non-magnetic substance is in contact with the magnetic powder to perform pressure molding. For this reason, the nonmagnetic material portion is required to have wear resistance. Therefore, it is preferable to employ a nonmagnetic material that is hard and excellent in wear resistance, such as Stellite (registered trademark), for the nonmagnetic portion of the lower punch.

JP 2012-80097 A JP 2007-203577 A

  Since the lower punch described in Patent Document 1 has a configuration in which two types of materials, a magnetic body and a nonmagnetic body, are joined, there is a problem in the adhesion of the joined portion (boundary portion) between the magnetic body and the nonmagnetic body. In particular, when the non-magnetic part is made of a hard material such as stellite, if the magnetic part is made of a hard material in the same manner, cracks or the like may occur at the joint between the two. For this reason, when the nonmagnetic material portion is made of a hard material such as stellite, the magnetic material portion needs to be made of a relatively soft material.

  By the way, since this type of lower punch slides in the insertion hole of the die when forming the magnetic powder, friction is generated between the outer peripheral surface of the lower punch and the inner wall surface of the insertion hole. However, as described above, the magnetic part of the lower punch needs to be made of a relatively soft material. For this reason, there has been a problem that the magnetic material portion (soft material portion) of the lower punch is worn by friction with the inner wall surface of the insertion hole.

  In this regard, Patent Document 2 describes a configuration in which a diamond-like carbon film is formed on the upper surface of the lower punch. According to Patent Document 2, this improves the wear resistance against the magnetic powder and reduces the amount of the release agent used. Therefore, it is conceivable to improve the wear resistance of the lower punch by providing a coating as in Patent Document 2 on the outer peripheral surface of the lower punch.

  However, even if a film as in Patent Document 2 is provided on the lower punch, the effect of preventing wear due to friction with the inner wall surface of the die cannot be expected. That is, since such a coating is extremely thin and fragile, when the outer peripheral surface of the lower punch slides with the inner wall surface of the insertion hole, it is easily peeled off from the outer peripheral surface of the lower punch. For this reason, even if the coating as described above is provided on the outer peripheral surface of the lower punch, a sufficient effect cannot be obtained in terms of improving the durability of the lower punch.

  In addition to the above, there are the following problems.

  That is, the inner wall surface of the die insertion hole is also worn by friction in the same manner as the outer peripheral surface of the lower punch is worn. Conventionally, when the inner wall surface of the insertion hole is worn, the inner wall surface is processed and the die is reused.

  When the inner wall surface of the insertion hole is machined in this way, the width of the insertion hole is widened. Therefore, the width of the lower punch that has been utilized so far is too thin with respect to the insertion hole after machining. Therefore, in such a case, conventionally, the lower punch used so far has been discarded, and a lower punch adapted to the width of the insertion hole after processing has been newly created. For this reason, the cost of creating a new lower punch has been incurred.

Means and effects for solving the problems

  The present invention has been made in view of the above circumstances, and its main object is to improve the durability of a lower punch used for forming a ferrite magnet in a magnetic field. Another object of the present invention is to provide a method capable of reusing a lower punch.

According to an aspect of the present invention, a die, a lower punch that slides in a predetermined sliding direction in an insertion hole formed in the die, and disposed opposite to the lower punch are used for forming a ferrite magnet in a magnetic field. The following configuration is provided for the lower punch of the mold comprising the upper punch. That is, the lower punch includes a base material portion, a nonmagnetic material portion, and a sliding contact layer. The base material portion is made of a magnetic material. The nonmagnetic body portion is disposed at an end portion of the base material portion facing the upper punch in the sliding direction of the lower punch, and is made of a nonmagnetic material. The sliding contact layer is provided on at least a part of the outer peripheral surface of the base material portion and contacts the inner wall surface of the insertion hole. And the said sliding contact layer consists of a magnetic body harder than the said base material part. The sliding contact layer is not provided on the outer peripheral surface of the nonmagnetic body portion. In the joint portion between the base material portion and the nonmagnetic material portion, a step is formed so that the outer peripheral surface of the base material portion is lower than the outer peripheral surface of the nonmagnetic material portion. The sliding contact layer is formed in a portion that is lowered by the step. And the outer peripheral surface of the said sliding contact layer and the outer peripheral surface of the said nonmagnetic body part are flush | level.

Thus, the wear resistance of the lower punch can be improved by providing the sliding contact layer on the outer peripheral surface of the base material portion. Moreover, since the sliding contact layer is made of a magnetic material, the sliding contact layer and the base material portion can be regarded as one magnetic material, and a good magnetic field can be formed. In the present invention, since the sliding contact layer is made of a magnetic material, if a sliding contact layer is provided on the outer periphery of the non-magnetic material portion, the magnetic field of the non-magnetic material portion affects the influence of the sliding contact layer. I will receive it. Therefore, as described above, the sliding contact layer has an adverse effect on the magnetic field of the nonmagnetic body portion by not providing the sliding contact layer (magnetic body) on the outer periphery of the nonmagnetic body portion. You can avoid that. Moreover, the base material part is formed one step lower than the non-magnetic part, and the sliding contact layer and the non-magnetic part can be finished flush with each other by providing the sliding contact layer in this part. By finishing the two parts flush with each other at the boundary between the non-magnetic part and the sliding contact layer, the outer periphery of the lower punch is not caught and the sliding contact layer is less likely to be peeled off from the substrate part. Further improvement can be achieved.

  In the lower punch, it is preferable that the thickness of the sliding contact layer is 0.1 mm or more.

  Thus, the durability of the sliding contact layer can be sufficiently ensured by setting the thickness of the sliding contact layer to, for example, 0.1 mm or more.

  In the lower punch, it is preferable that the sliding contact layer is stainless steel having a hardness of 40 to 60 in HRC.

  Thereby, it is possible to obtain a sliding contact layer having excellent wear resistance and made of a magnetic material. Further, when the material of the sliding contact layer is made of stainless steel, the repair can be easily performed by overlay welding. In addition, when performing wet-type forming in a magnetic field using a corrosive dispersion medium such as water, it is particularly preferable to use stainless steel having corrosion resistance.

  According to another viewpoint of this invention, the lower punch manufacturing method for manufacturing said lower punch is provided. That is, in this lower punch manufacturing method, the sliding contact layer is formed by overlay welding a material whose hardness in use is harder than that of the base material portion to the outer peripheral surface of the base material portion.

  Thus, by forming the sliding contact layer by welding, it is possible to obtain a sliding contact layer having good adhesion to the base material portion. Thereby, since a sliding contact layer does not peel from a base material part, durability of a lower punch can be improved. In addition, since overlay welding is easy to form a thick sliding contact layer, a sliding contact layer having sufficient strength can be easily formed.

  According to still another aspect of the present invention, the following lower punch manufacturing method is provided. That is, this lower punch manufacturing method includes a sliding contact layer welding process, a non-magnetic part welding process, and a machining process. In the sliding contact layer welding step, a magnetic material harder than the base material is welded to the outer peripheral surface of the sliding contact layer of the lower punch. In the non-magnetic body part welding step, the non-magnetic body is welded on the outer peripheral surface of the non-magnetic body part of the lower punch. In the processing step, processing is performed so that the outer peripheral surface of the sliding contact layer and the outer peripheral surface of the non-magnetic body portion are flush with each other.

  Even if the outer circumference of the lower punch is worn, etc., the welded parts are regenerated by performing overlay welding on the outer circumferential surfaces of the sliding contact layer and the non-magnetic body, and then performing polishing or other processing. be able to. Thereby, compared with the case where the worn lower punch is discarded and another lower punch is newly created, the cost can be greatly reduced. In addition, since overlay welding is performed on the outer peripheral surface of the lower punch, it is possible to manufacture a lower punch having a width wider than that of the original lower punch. According to this, even if the die is worn and the width of the insertion hole is increased, it can be coped with by increasing the width of the lower punch used so far. Therefore, the cost can be greatly reduced as compared with the conventional method in which a lower punch is newly created each time the die is worn.

Sectional drawing of the metal mold | die which concerns on one Embodiment of this invention. Sectional drawing which shows a mode that the lower punch was inserted in the insertion hole. The perspective view of the ferrite magnet shape | molded by the metal mold | die of this embodiment. Sectional drawing which shows the manufacturing method of the lower punch of this embodiment. Sectional drawing which shows the repair method of a lower punch. Sectional drawing which shows the method of manufacturing the lower punch whose width | variety of a front-end | tip part is thicker than it based on the existing lower punch.

  Next, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the mold 1 according to the present embodiment includes an upper punch 2, a lower punch 3, and a die 4. This mold 1 is used for forming a ferrite magnet in a magnetic field. The formation of a ferrite magnet in a magnetic field and the general configuration of its mold are known as described in, for example, Patent Document 1 and Patent Document 2, but will be briefly described below.

  The lower punch 3 is configured as an elongated quadrangular prism-shaped member, and a front end portion 5 and a holding portion 6 are provided side by side in the longitudinal direction thereof. Note that the tip 5 has a function as a mold of the lower punch 3, and the holding portion 6 is provided exclusively for holding the tip 5. The lower punch 3 is configured to be movable along the longitudinal direction thereof. The direction in which the lower punch 3 moves is indicated by a thick arrow in FIG.

  The die 4 has an insertion hole 7 formed in a direction parallel to the moving direction of the lower punch 3. The inner wall surface 8 of the insertion hole 7 is formed to be the same as or slightly larger than the outer peripheral shape of the distal end portion 5 of the lower punch 3. Thereby, the front-end | tip part 5 of the lower punch 3 can be inserted in the insertion hole 7 (refer FIG. 2). With the distal end 5 inserted into the insertion hole 7, the lower punch 3 is moved in the longitudinal direction so that the distal end 5 slides inside the insertion hole 7. In the present specification, the direction in which the lower punch 3 slides inside the insertion hole 7 (the longitudinal direction of the lower punch 3) may be simply referred to as “sliding direction”.

  The upper punch 2 is fixedly provided to the die 4. The upper punch 2 is disposed so as to close the insertion hole 7 formed in the die 4 from the side opposite to the side where the lower punch 3 is inserted. As shown in FIG. 2, the end surface of the lower punch 3 faces the upper punch 2 in a state where the distal end portion 5 of the lower punch 3 is inserted into the insertion hole 7. As shown in FIG. 1, a convex curved surface 9 that is convex toward the upper punch 2 is formed at the tip 5 of the lower punch 3. On the other hand, a concave curved surface 10 is formed on the upper punch 2 so as to face the convex curved surface 9.

  With the above configuration, by inserting the tip 5 of the lower punch 3 into the insertion hole 7 of the die 4, the inner wall surface 8 of the insertion hole 7 of the die 4, the convex curved surface 9 of the lower punch 3, and the concave curved surface of the upper punch 2. A cavity 11 surrounded by 10 is formed (see FIG. 2). When molding with the mold 1, magnetic powder (or slurry in which the magnetic powder is dispersed in a dispersion medium) that is a raw material of the ferrite magnet 12 is injected into the cavity 11. Then, a magnetic field passing through the cavity 11 is applied by a magnetic field applying device (not shown) while the lower punch 3 is advanced to a predetermined position to pressurize the magnetic powder in the cavity 11.

  In the mold for molding in a magnetic field as in this embodiment, generally, the lower punch 3 and the upper punch 2 are mostly made of a ferromagnetic material. For this reason, the magnetic field lines of the magnetic field applied by the magnetic field application device are bent by the lower punch 3 and the upper punch 2. As a result, a magnetic field having a predetermined shape is formed inside the cavity 11 (between the convex curved surface 9 and the concave curved surface 10). The magnetic field lines of the magnetic field formed in the cavity 11 are illustrated by two-dot chain arrows in FIG. Note that the die 4 is made of a non-magnetic material so as not to affect the formation of the magnetic field.

  The magnetic powder in the cavity 11 flows according to the magnetic field. Thereby, the molded object which has a predetermined magnetic field orientation is obtained. Thereafter, the molded body is taken out from the cavity 11, sintered, and appropriately processed as necessary, whereby a ferrite magnet 12 as shown in FIG. 3 can be obtained.

  The mold 1 of the present embodiment is assumed to form an arc segment type (bow type) ferrite magnet 12 as shown in FIG. Therefore, the shape of the cavity 11 surrounded by the inner wall surface 8, the convex curved surface 9, and the concave curved surface 10 is an arc segment type. The arc segment type ferrite magnet 12 as shown in FIG. 3 is used not only for a stator or a rotor of an electric motor but also for a speaker, a magnetron tube and the like.

  Next, the lower punch 3 of this embodiment will be described in more detail.

  The lower punch 3 includes a nonmagnetic body portion 20 made of a nonmagnetic material, a base material portion 21 made of a ferromagnetic material, and a sliding contact layer 23 also made of a ferromagnetic material.

  As shown in FIG. 1, the base material portion 21 is disposed across the tip portion 5 and the holding portion 6 of the lower punch 3. As shown in FIG. 1, the base material portion 21 occupies the entire holding portion 6 of the lower punch 3. On the other hand, in the front end portion 5, the surface of the base material portion 21 is covered with the nonmagnetic body portion 20 and the sliding contact layer 23. Therefore, the base material portion 21 is not exposed at the front end portion 5 of the lower punch 3.

  The nonmagnetic body portion 20 is disposed at the tip portion 5 so as to cover the entire tip surface (portion facing the upper punch 2) of the base material portion 21. Therefore, when the front end portion 5 of the lower punch 3 is inserted into the insertion hole 7, the nonmagnetic body portion 20 faces the concave curved surface 10 of the upper punch 2 (see FIG. 2). The non-magnetic body portion 20 is formed with the convex curved surface 9 described above. Further, as shown in FIG. 1, the joint surface (boundary surface) between the nonmagnetic body portion 20 and the base material portion 21 is a second convex curved surface 22 that is convex toward the concave curved surface 10 of the upper punch 2. ing. In other words, the base material portion 21 of the present embodiment has a second convex curved surface 22 that is convex toward the concave curved surface 10 of the upper punch 2.

  Here, the effect of configuring the lower punch 3 with two kinds of materials, that is, a non-magnetic material (non-magnetic material portion 20) and a magnetic material (base material portion 21) will be briefly described.

  Since the nonmagnetic body portion 20 does not affect the formation of the magnetic field, the shape of the magnetic field in the cavity 11 is not affected regardless of the shape of the convex curved surface 9. The shape of the magnetic field formed in the cavity 11 (direction of the lines of magnetic force) is determined by the shape of the base material portion 21 that is a magnetic body (more specifically, the shape of the second convex curved surface 22). In the case of the lower punch 3 configured as in the present embodiment, the shape of the convex curved surface 9 and the shape of the second convex curved surface 22 can be made different from each other. Therefore, in the lower punch 3 of the present embodiment, the convex curved surface 9 has a shape capable of forming the segment arc-shaped cavity 11, and the second convex curved surface 22 has a shape capable of forming an ideal magnetic field in the cavity 11. .

  In this way, the lower punch 3 is made of two kinds of materials, that is, a magnetic body (base material portion 21) and a non-magnetic body (non-magnetic body portion 20), so that the cavity 11 having a desired shape is formed. 11 can form a magnetic field of a desired shape. Thereby, the ferrite magnet 12 having a desired shape and a desired magnetic field orientation can be obtained.

  Since the nonmagnetic body portion 20 is exposed in the cavity 11 and contacts the magnetic powder injected into the cavity 11, wear resistance is required. In the mold 1 of the present embodiment, Stellite (registered trademark), which is a non-magnetic material excellent in wear resistance, is employed as the material of the non-magnetic material portion 20. Stellite has an HRC (Rockwell hardness) of about 45.

  Moreover, as already demonstrated as a prior art, when both the non-magnetic-material part 20 and the base material part 21 are comprised with a hard material similarly, a crack etc. may generate | occur | produce in both joining part. For this reason, it is preferable that the magnetic material used for the base member 21 is softer than the non-magnetic member 20. In this embodiment, carbon steel such as S45C is adopted as the material of the base material portion 21. Note that the HRC of S45C is about 25.

  Subsequently, a characteristic configuration of the lower punch 3 of the present embodiment will be described.

  When the magnetic powder is molded with the mold 1 of the present embodiment, the distal end portion 5 of the lower punch 3 slides in the insertion hole 7 formed in the die 4, and therefore the outer peripheral surface of the distal end portion 5 and the insertion hole 7. Friction occurs between the inner wall surface 8 and the inner wall surface 8. For this reason, the outer peripheral surface of the tip portion 5 is required to have wear resistance. However, as described above, the base material portion 21 of the lower punch 3 must be made of a softer material than the non-magnetic material portion 20, and is not sufficient in terms of wear resistance. For this reason, if the base material portion 21 is in direct contact with the inner wall surface 8, the outer peripheral surface of the base material portion 21 is quickly worn.

  Therefore, the lower punch 3 of the present embodiment is provided with a sliding contact layer 23 made of a magnetic material harder than the base material portion 21 on the outer peripheral surface of the base material portion 21. The sliding contact layer 23 is disposed so as to cover the entire outer peripheral surface of the base material portion 21 at the distal end portion 5 of the lower punch 3. Therefore, when the magnetic powder is molded with the mold 1 of the present embodiment, the sliding contact layer 23 arranged on the outer periphery of the base portion 21 contacts and slides on the inner wall surface 8 of the insertion hole 7. It will be. In the present specification, the “outer peripheral surface” refers to a surface parallel to the longitudinal direction of the lower punch 3. Therefore, when the “outer peripheral surface” of the front end portion 5 of the lower punch 3 is referred to, it means a surface facing the inner wall surface 8 of the insertion hole 7.

  As described above, by providing the sliding contact layer 23 so as to cover the outer peripheral surface of the base material portion 21 at the distal end portion 5 of the lower punch 3, the base material portion 21 contacts the inner wall surface 8 of the insertion hole 7. It is supposed not to. Thereby, abrasion of the base material part 21 can be prevented.

  Since the sliding contact layer 23 is made of a material harder than the base material portion 21, the sliding contact layer 23 is excellent in wear resistance as compared with the base material portion 21. Therefore, by providing the sliding contact layer 23 on the outer periphery of the base material portion 21, wear of the lower punch 3 can be reduced and the life of the lower punch 3 can be extended.

  As shown in the cross-sectional view of FIG. 1, the outer peripheral surface of the base material portion 21 becomes one step lower than the outer peripheral surface of the nonmagnetic material portion 20 at the joint portion (boundary portion) between the nonmagnetic material portion 20 and the base material portion 21. As described above (that is, the base material portion 21 is recessed toward the inner side of the lower punch 3), the step 24 is formed. A sliding contact layer 23 is provided so as to fill the step 24. And the outer peripheral surface of the nonmagnetic body part 20 and the outer peripheral surface of the sliding contact layer 23 are connected, and both are flush.

  Thus, in the lower punch 3 of the present embodiment, the outer peripheral surface of the non-magnetic body portion 20 and the outer peripheral surface of the sliding contact layer 23 are connected without any step, so that the tip portion 5 slides in the insertion hole 7. No catching occurs. Thereby, the lower punch 3 can slide smoothly, and the sliding contact layer 23 can be prevented from being peeled off from the base material portion 21.

  Further, in the cross section (the cross section shown in FIG. 1 and the like) parallel to the longitudinal direction of the lower punch 3, the base material portion 21 is wedge-shaped in the portion between the nonmagnetic body portion 20 and the sliding contact layer 23. A wedge part 25 is provided. That is, since the non-magnetic part 20 and the sliding contact layer 23 are both hard materials, if they are directly joined, cracks or the like may occur at the joined part. Therefore, the base material portion 21 is configured to enter the wedge shape between the nonmagnetic material portion 20 and the sliding contact layer 23. Since the base material portion 21 is a relatively soft material, the wedge portion 25 between the non-magnetic body portion 20 and the sliding contact layer 23 serves as a buffer portion and can prevent cracking.

  In addition, as shown in FIG. 1, the wedge part 25 is formed so that it may become thin as it approaches an outer peripheral surface, and it is comprised so that it may lose | disappear just before reaching an outer peripheral surface. That is, the wedge part 25 of the base material part 21 is not exposed to the outer peripheral surface. By providing such a wedge portion 25, it is possible to prevent cracks between the two while connecting the outer peripheral surface of the nonmagnetic body portion 20 and the outer peripheral surface of the sliding contact layer 23.

  If the sliding contact layer 23 is a material harder than the base material part 21, the effect which improves the abrasion resistance of the lower punch 3 can be acquired. In the case of this embodiment, since the hardness of the base material portion 21 is about HRC = 25, the material of the sliding contact layer 23 is not particularly limited as long as it is a harder magnetic material. However, from the viewpoint of ensuring sufficient wear resistance, the material of the sliding contact layer 23 preferably has an HRC of 40 or more. On the other hand, since the outer peripheral surface of the sliding contact layer 23 of the present embodiment is finished by machining such as polishing (details will be described later), the hardness of the sliding contact layer 23 is HRC 60 or less from the viewpoint of facilitating processing. Preferably there is.

  Moreover, as will be described later, the sliding contact layer 23 of the present embodiment is formed by overlay welding. Therefore, the material of the sliding contact layer 23 is preferably a weldable metal material. Furthermore, since a slurry using water or the like as a dispersion medium may be injected into the cavity 11 of the mold 1, it is preferable to employ a material having corrosion resistance as the material of the sliding contact layer 23. Considering the above points, it is preferable to use Slentes steel as the material of the sliding contact layer 23. In this embodiment, stainless steel such as SUS420F is adopted as the material of the sliding contact layer 23. The HRC of SUS420F is about 50.

  The sliding contact layer 23 is provided only on the outer peripheral surface of the base portion 21, and is not provided on the outer peripheral surface of the nonmagnetic body portion 20. This is because the non-magnetic body portion 20 of the present embodiment is made of stellite having excellent wear resistance, and thus there is little need to protect it by the sliding contact layer 23. Therefore, when the magnetic powder is molded with the mold 1 of the present embodiment, the outer peripheral surface of the nonmagnetic body portion 20 is in direct contact with the inner wall surface 8 of the insertion hole 7 and slides.

  Further, since the sliding contact layer 23 is a magnetic body, if this sliding contact layer 23 is provided on the outer peripheral surface of the nonmagnetic body portion 20, it will affect the lines of magnetic force passing through the nonmagnetic body portion 20. . Therefore, as described above, the magnetic body (sliding contact layer 23) is not provided on the outer peripheral surface of the nonmagnetic body portion 20, so that the magnetic field lines passing through the nonmagnetic body portion 20 are not affected. It is.

  Further, only the front end portion 5 of the lower punch 3 is inserted into the insertion hole 7, and the holding portion 6 of the lower punch 3 is not inserted into the insertion hole 7. Therefore, since there is no fear that the outer peripheral surface of the holding portion 6 of the lower punch 3 is worn, the sliding contact layer 23 is not provided on the outer peripheral surface of the holding portion 6.

  As described above, the sliding contact layer 23 of the present embodiment is provided only on the outer peripheral surface of the base material portion 21 at the distal end portion 5 of the lower punch 3. As described above, since the sliding contact layer 23 only needs to be formed on a very small part of the outer peripheral surface of the lower punch 3, it is possible to reduce the burden of work (described later) for forming the sliding contact layer 23 by overlay welding.

  Then, the manufacturing method of the lower punch 3 of this embodiment is demonstrated with reference to FIG.

  First, a non-magnetic body 20 and a base 21 are joined (FIG. 4A). From the standpoint of securing a polishing allowance in a later processing step, the non-magnetic body portion 20 is slightly larger in the width direction (direction perpendicular to the longitudinal direction of the lower punch 3) than the prescribed dimension. It is suitable if it is formed. In FIG. 4, a predetermined dimension in the width direction of the tip portion 5 is indicated by L1, and a polishing allowance of the nonmagnetic body portion 20 is indicated by L2.

  Then, the outer peripheral surface of the base material part 21 of the front-end | tip part 5 is shaved by appropriate methods, such as machining, and the width | variety of the said base material part 21 is reduced rather than the regular dimension L1 (FIG.4 (b)). The portion cut in this way becomes the aforementioned step 24. In FIG. 4, the depth of the step 24 (the dimension cut inward from the specified dimension L1) is indicated by L3. In the present embodiment, the depth of the step 24 is L3 = 0.2 mm. In addition, when the outer peripheral surface of the base material part 21 is shaved, the R part is left at the boundary part between the base material part 21 and the nonmagnetic material part 20 (state of FIG. 4B). This R portion becomes the aforementioned wedge portion 25.

  Next, the material of the sliding contact layer 23 (SUS420F in this embodiment) is build-up welded to the outer peripheral surface of the step 24 formed on the base material portion 21 to form the weld portion 26 (FIG. 4C). ). At this time, overlay welding is performed such that the height (dimension in the width direction) of the welded portion 26 is higher than the depth L3 of the step 24 (that is, the welded portion 26 protrudes from the step 24 in the width direction). To do. This is to ensure a polishing allowance for the welded portion 26.

  Finally, the outer peripheral surfaces of the non-magnetic body portion 20 and the welded portion 26 are machined (polished or cut) so that the width of the tip portion 5 of the lower punch 3 becomes a specified dimension L1 (FIG. 4D). . Thereby, the outer peripheral surface of the welding part 26 is finished smoothly, and the sliding contact layer 23 is formed. In addition, by polishing (or cutting) the outer peripheral surface of the nonmagnetic body portion 20 and the outer peripheral surface of the welded portion 26 at the same time, the outer peripheral surface of the nonmagnetic body portion 20 and the outer peripheral surface of the sliding contact layer 23 are finished flush with each other. be able to.

  As described above, in the manufacturing method of the present embodiment, the sliding contact layer 23 is formed by welding on the outer peripheral surface of the base material portion 21, and thus the sliding contact layer 23 having good adhesion to the base material portion 21. Can be formed. Thereby, it can prevent that the sliding contact layer 23 peels from the base material part 21. FIG.

  Moreover, since the sliding contact layer 23 is formed by overlay welding, it is easy to form the sliding contact layer 23 having a thickness. In terms of ensuring sufficient strength of the sliding contact layer 23, the thickness of the sliding contact layer 23 is preferably set to 0.1 mm or more, for example. In the case of overlay welding, the sliding contact layer 23 having a thickness as described above can be formed. In the present embodiment, since the depth L3 of the step 24 is 0.2 mm, the thickness of the sliding contact layer 23 formed so as to fill the step 24 is 0.2 mm.

  In this respect, for example, it is conceivable to form the sliding contact layer 23 by coating. However, it is technically difficult to form the sliding contact layer 23 having a thickness of 0.2 mm by coating, or in reality from the viewpoint of cost. Not right. For this reason, it is difficult to form the sliding contact layer 23 having sufficient strength by coating. In addition, when the sliding contact layer 23 is formed by coating, it is difficult to ensure the adhesion between the sliding contact layer 23 and the base material portion 21, so that the sliding contact layer 23 is separated from the base material portion 21. It easily peels off.

  In the present embodiment, since the sliding contact layer 23 is formed by overlay welding, the sliding contact layer 23 having excellent adhesion with the base material portion 21 and having a large thickness can be formed easily and inexpensively. it can. Thereby, durability of the lower punch 3 can be improved cheaply and easily.

  Further, if the sliding contact layer 23 is formed by coating, the sliding contact layer 23 becomes extremely thin, so that there is almost no polishing allowance for the sliding contact layer 23. Therefore, if the sliding contact layer 23 is formed by coating, it is difficult to finish the outer peripheral surface of the sliding contact layer 23 and the outer peripheral surface of the nonmagnetic body portion 20 to be flush with each other. In the present embodiment, since the sliding contact layer 23 is formed by overlay welding, it is easy to secure a polishing allowance for the sliding contact layer 23. Thus, the outer peripheral surface of the sliding contact layer 23 and the outer peripheral surface of the nonmagnetic body portion 20 can be finished by polishing (or cutting or the like) so as to be flush with each other.

  Next, the effect of using the sliding contact layer 23 as a magnetic material will be described.

  As described above, the lower punch 3 of the present embodiment forms the step 24 at the tip portion 5 of the base material portion 21 in order to provide the sliding contact layer 23 having a thickness. For this reason, the width | variety of the base material part 21 of the front-end | tip part 5 is thinner than the regular dimension L1. Thus, in order to provide the sliding contact layer 23, the width of the base material portion 21 must be made smaller than the specified dimension L1.

  Now, if only considering improving the wear resistance of the base member 21, the sliding contact layer 23 may be a non-magnetic material. However, if the sliding contact layer 23 is made of a non-magnetic material, the portion of the sliding contact layer 23 does not affect the formation of the magnetic field. For this reason, the thicker the sliding contact layer 23 is, the narrower the magnetic part (base material part 21) of the lower punch 3 becomes, and it becomes difficult to form an ideal magnetic field in the cavity 11. .

  In this regard, since the lower punch 3 of the present embodiment uses the sliding contact layer 23 as a magnetic material, the sliding contact layer 23 affects the formation of a magnetic field. Therefore, from the viewpoint of forming a magnetic field, the sliding contact layer 23 and the base material portion 21 can be considered as one “magnetic body”. In this case, even if the width of the base material portion 21 is reduced by increasing the thickness of the sliding contact layer 23, the width of the “magnetic material” including both is the specified dimension L1. Thus, by using the sliding contact layer 23 as a magnetic material, the width of the “magnetic material” portion of the lower punch 3 can be secured regardless of the thickness of the sliding contact layer 23. Therefore, according to the configuration of the present embodiment, an ideal magnetic field can be formed in the cavity 11 while ensuring a sufficient thickness of the sliding contact layer 23.

  Then, the repair method of the lower punch 3 of this embodiment is demonstrated.

  Although the lower punch 3 of the present embodiment has improved wear resistance by providing the sliding contact layer 23, the outer peripheral surface of the tip 5 may gradually wear if used for a long time. .

  If the lower punch 3 with a worn outer peripheral surface of the tip portion 5 is continuously used, a gap is formed between the outer peripheral surface of the tip portion 5 and the inner wall surface 8 of the insertion hole 7, and the inside of the cavity 11 is formed during molding. Magnetic powder may leak out. For this reason, conventionally, the lower punch 3 in which the outer peripheral surface of the tip 5 is worn has been discarded.

  Accordingly, the present invention proposes a method for repairing the worn lower punch 3. This repair method is performed as follows.

  First, as shown in FIG. 5 (a), a lower punch 3 having a worn outer peripheral surface of the tip 5 is prepared. Subsequently, a material of a magnetic material harder than the base material portion 21 is welded to the worn outer peripheral surface of the sliding contact layer 23 to form the sliding contact layer welded portion 27 (sliding contact layer welding step). . At this time, the material to be welded is preferably the same material as the sliding contact layer 23 (SUS420F in this embodiment).

  Similarly, the nonmagnetic body welded portion 28 is formed by overlay welding a wear-resistant nonmagnetic material on the worn outer peripheral surface of the nonmagnetic body portion 20 (nonmagnetic body portion welding step). At this time, it is preferable that the material to be welded is the same material as the non-magnetic body portion 20 (in the case of the present embodiment, stellite). The order of the sliding contact layer welding process and the non-magnetic body welding process may be reversed. FIG. 5B shows a state in which the sliding contact layer welded portion 27 and the nonmagnetic welded portion 28 are formed.

  Then, the outer peripheral surfaces of the sliding contact layer welded portion 27 and the non-magnetic welded portion 28 are machined (polished or cut) so that the width of the tip portion 5 welded as described above becomes the specified dimension L1. Etc.) (processing step). Thereby, the outer peripheral surfaces of the sliding contact layer welded portion 27 and the nonmagnetic welded portion 28 are finished smoothly. By the above machining, the worn outer peripheral surfaces of the non-magnetic member 20 and the sliding contact layer 23 can be restored to the original smooth state (FIG. 5C).

  As described above, the nonmagnetic material is welded to the worn outer peripheral surface of the nonmagnetic material portion 20, the magnetic material is welded to the worn outer peripheral surface of the sliding contact layer 23, and then the outer peripheral surface is polished (or By cutting or the like, the worn outer peripheral surface can be repaired. The part added by overlay welding is integrated with the part before repair, so there is no concern that the part added by welding will be peeled off. Since the worn lower punch 3 can be repaired by the above repairing method, the lower punch 3 can be reused.

  The repair method described above can be considered as a manufacturing method for manufacturing the repaired lower punch 3 based on the worn lower punch 3. In view of this, the manufacturing method of the present invention is not limited to simply repairing the worn lower punch 3 but can be reinterpreted as a method of manufacturing a lower punch different from the original lower punch 3.

  Therefore, a method for manufacturing a lower punch 3 ′ having a tip 5 having a larger width than the lower punch 3 based on the existing lower punch 3 will be described next.

  First, the necessity of increasing the width of the tip 5 of the lower punch 3 will be briefly described. That is, if the mold 1 is used for a long time, the inner wall surface 8 of the insertion hole 7 of the die 4 may be worn. Therefore, it has been conventionally practiced to reuse the dice 4 by machining (polishing or cutting) the worn inner wall surface 8 so that the inner wall surface 8 becomes smooth.

  When such processing is performed, the width of the insertion hole 7 is slightly expanded. Accordingly, the lower punch 3 having a wider width at the tip portion 5 than before is required corresponding to the expanded insertion hole 7. Conventionally, since it was thought that the lower punch 3 could not be thickened, the lower punch 3 used until then was discarded.

  Therefore, the present invention proposes a method of manufacturing a lower punch 3 ′ having a tip 5 having a wider width than the existing lower punch 3. Hereinafter, this manufacturing method will be described with reference to FIG.

  First, the original lower punch 3 is prepared (FIG. 6A). The prescribed width of the tip 5 of the lower punch 3 is denoted by L1. 6A illustrates a state in which the outer peripheral surface of the tip portion 5 is not worn. However, the present invention is not limited to this, and the lower punch in which the outer peripheral surface of the tip portion 5 is worn as shown in FIG. 5A. 3 can also be used.

  Subsequently, the material of the magnetic material harder than the base material portion 21 is welded to the outer peripheral surface of the prepared sliding contact layer 23 of the lower punch 3 to form the sliding contact layer welded portion 27 (sliding contact layer 27). Welding process). At this time, the material to be welded is preferably the same material as the sliding contact layer 23 (SUS420F in this embodiment).

  Similarly, the nonmagnetic material welded portion 28 is formed by overlay welding a wear-resistant nonmagnetic material on the outer peripheral surface of the nonmagnetic material portion 20 of the prepared lower punch 3 (nonmagnetic material portion welding step). ). At this time, it is preferable that the material to be welded is the same material as the non-magnetic body portion 20 (in the case of the present embodiment, stellite). The order of the sliding contact layer welding process and the non-magnetic body welding process may be reversed. A state in which the sliding contact layer welded portion 27 and the nonmagnetic welded portion 28 are formed is shown in FIG.

  Finally, the outer peripheral surfaces of the sliding contact layer welded portion 27 and the non-magnetic welded portion 28 are machined (polished or cut) (processing step) so that the width of the tip portion 5 becomes the desired dimension L4. . The processed width L4 of the tip 5 can be arbitrarily larger than the width L1 of the original tip 5. Therefore, the lower punch 3 ′ in which the width of the tip portion 5 is larger than that of the original lower punch 3 can be manufactured inexpensively and easily.

  Thus, according to the manufacturing method of the present embodiment, the width of the tip portion 5 of the original lower punch 3 can be increased. Therefore, for example, even when the width of the insertion hole 7 of the die 4 is expanded by machining, it can be dealt with by increasing the width of the tip 5 of the lower punch 3 that has been used so far. Thus, since the lower punch 3 used so far can be reused, the cost for manufacturing the lower punch with the tip 5 having a large width can be greatly reduced.

  As described above, the lower punch 3 of the present embodiment includes the base material portion 21, the nonmagnetic material portion 20, and the sliding contact layer 23. The base material part 21 consists of a magnetic body. The nonmagnetic body portion 20 is disposed at an end portion of the base portion 21 on the side facing the upper punch 2 in the sliding direction of the lower punch 3 and is made of a nonmagnetic material. The sliding contact layer 23 is provided on the outer peripheral surface of the base material portion 21 and contacts the inner wall surface 8 of the insertion hole 7. The sliding contact layer 23 is made of a magnetic material that is harder than the base material portion 21.

  Thus, by providing the sliding contact layer 23 on the outer peripheral surface of the base material portion 21, the wear resistance of the lower punch 3 can be improved. Further, since the sliding contact layer 23 is made of a magnetic material, the sliding contact layer 23 and the base material portion 21 can be regarded as one magnetic material, and a good magnetic field can be formed. Furthermore, even when the sliding contact layer 23 is worn, it can be easily repaired by overlay welding the same material as the sliding contact layer 23. Thus, according to the configuration of the present embodiment, it is possible to provide the lower punch 3 that can improve durability and can be easily repaired and regenerated.

  In the lower punch 3 of the present embodiment, the sliding contact layer 23 is not provided on the outer peripheral surface of the nonmagnetic body portion 20.

  That is, in the present invention, since the sliding contact layer 23 is made of a magnetic material, if the sliding contact layer 23 is provided on the outer periphery of the nonmagnetic material portion 20, the magnetic field of the nonmagnetic material portion 20 is slidably contacted. The layer 23 is affected. Therefore, as described above, the sliding contact layer 23 (magnetic body) is not provided on the outer periphery of the nonmagnetic body portion 20, so that the sliding contact layer 23 against the magnetic field of the nonmagnetic body portion 20 is provided. Can avoid adverse effects.

  Further, in the lower punch 3 of the present embodiment, the step 24 is such that the outer peripheral surface of the base member 21 is lower than the outer peripheral surface of the non-magnetic member 20 at the joint between the base member 21 and the nonmagnetic member 20. Is formed. The sliding contact layer 23 is formed in a portion that is lowered by the step 24. The outer peripheral surface of the sliding contact layer 23 and the outer peripheral surface of the nonmagnetic body portion 20 are flush with each other.

  Thus, the base material part 21 is formed one step lower than the non-magnetic body part 20, and the sliding contact layer 23 and the non-magnetic body part 20 are faced by providing the sliding contact layer 23 in this part. Can be finished to one. By finishing the two surfaces flush with each other at the boundary portion between the nonmagnetic part 20 and the sliding contact layer 23, the outer periphery of the lower punch 3 is not caught and the sliding contact layer 23 is less likely to be peeled off from the base part 21. The durability of the lower punch 3 can be further improved.

  Moreover, since the thickness of the sliding contact layer 23 is 0.2 mm, the lower punch 3 of the present embodiment can sufficiently ensure the durability of the sliding contact layer 23.

  In the lower punch 3 of this embodiment, the sliding contact layer 23 is made of stainless steel (SUS420F) having a hardness of HRC 50. Thereby, the sliding contact layer 23 which is excellent in abrasion resistance and is made of a magnetic material can be obtained. In addition, when the material of the sliding contact layer 23 is stainless steel, the repair can be easily performed by overlay welding. In addition, when performing wet-type forming in a magnetic field using a corrosive dispersion medium such as water, it is particularly preferable to use stainless steel having corrosion resistance.

  Moreover, in the lower punch manufacturing method of this embodiment, the sliding contact layer 23 is formed on the outer peripheral surface of the base material portion 21 by overlay welding a material whose hardness during use is harder than that of the base material portion 21. Forming.

  Thus, by forming the sliding contact layer 23 by welding, it is possible to obtain the sliding contact layer 23 having good adhesion to the base material portion 21. Thereby, since the sliding contact layer 23 does not peel from the base material part 21, durability of the lower punch 3 can be improved. Moreover, since it is easy to form the thick sliding contact layer 23 if it is overlay welding, the sliding contact layer 23 of sufficient intensity | strength can be formed easily.

  Moreover, the lower punch manufacturing method of the present embodiment includes a sliding contact layer welding process, a non-magnetic body welding process, and a machining process. In the sliding contact layer welding process, a magnetic material harder than the base material portion 21 is welded to the outer peripheral surface of the sliding contact layer 23 of the lower punch 3. In the non-magnetic body part welding step, the non-magnetic body is welded on the outer peripheral surface of the non-magnetic body part 20 of the lower punch 3. In the processing step, processing is performed so that the outer peripheral surface of the sliding contact layer 23 and the outer peripheral surface of the nonmagnetic body portion 20 are flush with each other.

  Even when the outer periphery of the lower punch 3 is worn, for example, the welded part is subjected to build-up welding on the outer peripheral surfaces of the sliding contact layer 23 and the nonmagnetic body portion 20 and then subjected to processing such as polishing. Can be played. Thereby, compared with the case where the worn lower punch 3 is discarded and another lower punch is newly created, the cost can be greatly reduced. Further, since the overlay welding is performed on the outer peripheral surface of the lower punch 3, it is also possible to manufacture the lower punch 3 having a width wider than that of the original lower punch 3. According to this, even if the die 4 is worn and the width of the insertion hole 7 is increased, it can be coped with by increasing the width of the lower punch 3 used so far. Therefore, the cost can be greatly reduced as compared with the conventional method in which the lower punch 3 is newly created each time the die 4 is worn.

  The preferred embodiment of the present invention has been described above, but the above configuration can be modified as follows, for example.

  In the above embodiment, the sliding contact layer 23 is provided so as to cover the entire outer periphery of the distal end portion 5 of the base material portion 21. However, the present invention is not limited thereto, and the sliding contact layer 23 may be provided so as to cover only a part of the base material part 21 at the front end part 5 (that is, a part of the base material part 21 is exposed at the front end part 5. May be). Even in this case, the effect of improving the wear resistance of the lower punch can be obtained as compared with the case where the sliding contact layer 23 is not provided at all.

  The shape of the ferrite magnet formed by the mold 1 according to the present invention is not limited to the arc segment type. Therefore, the shape of the cavity 11 is not limited to that shown in FIG. 2 and can be an appropriate shape according to the shape of the target ferrite magnet.

  In the description of the method of manufacturing the lower punch 3 of the above embodiment, the step 24 is formed by shaving the base 21 after joining the non-magnetic part 20 and the base 21, but not limited to this. The step 24 may be formed in advance in the part 21 and then the non-magnetic part 20 and the base part 21 may be joined.

1 Mold 2 Upper punch 3 Lower punch 4 Die 7 Insertion hole 20 Non-magnetic part 21 Base part 23 Sliding contact layer

Claims (5)

The die is used for forming a ferrite magnet in a magnetic field, and includes a die, a lower punch that slides in a predetermined sliding direction in an insertion hole formed in the die, and an upper punch that is disposed to face the lower punch. The lower punch of the mold,
A base material portion made of a magnetic material;
In the sliding direction of the lower punch, a non-magnetic body portion that is disposed at an end portion of the base portion facing the upper punch and is made of a non-magnetic body,
A sliding contact layer that is provided on at least a part of the outer peripheral surface of the base material portion and contacts an inner wall surface of the insertion hole;
With
The sliding contact layer, Ri Do a hard magnetic material than the base portion,
The sliding contact layer is not provided on the outer peripheral surface of the non-magnetic body part,
In the joint portion between the base material portion and the nonmagnetic material portion, a step is formed so that the outer peripheral surface of the base material portion is lower than the outer peripheral surface of the nonmagnetic material portion,
The sliding contact layer is formed in a portion that is lowered by the step,
A lower punch , wherein an outer peripheral surface of the sliding contact layer and an outer peripheral surface of the non-magnetic part are flush with each other. The lower punch according to claim 1,
The lower punch, wherein the sliding contact layer has a thickness of 0.1 mm or more. The lower punch according to claim 1 or 2 ,
The lower punch, wherein the sliding contact layer is made of stainless steel having a hardness of 40 to 60 in HRC. A lower punch manufacturing method for manufacturing the lower punch according to any one of claims 1 to 3 ,
A method of manufacturing a lower punch, characterized in that the sliding contact layer is formed by overlay welding a material whose hardness in use is harder than that of the base material portion to the outer peripheral surface of the base material portion . A sliding contact layer welding step of overlay welding a magnetic material harder than the base material part to the outer peripheral surface of the sliding contact layer of the lower punch according to any one of claims 1 to 3 ,
A non-magnetic member welding step for overlay welding a non-magnetic member to the outer peripheral surface of the non-magnetic member of the lower punch;
A processing step of processing so that the outer peripheral surface of the sliding contact layer and the outer peripheral surface of the non-magnetic body portion are flush with each other;
A process for producing a lower punch, comprising:

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