JP2010150567A - Method for producing sintered component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the amount of chipping in a compact accompanying cutting before sintering, and to improve quality and a yield thereby. <P>SOLUTION: A method for producing a sintered component 1 includes: a compacting stage where raw material is compacted; a cutting stage where the compact 1A obtained in the compacting stage is subjected to cutting; and a sintering stage where the compact after the cutting stage is sintered, wherein the cutting stage is the one where both the side faces 1a, 1a of the compact 1A are constrained by a pair of fixtures 3 having opening parts 4 obtained by notching the upper face part and both the side face parts, and rotating cutting tools 5 are passed through the space between the opening parts of both the fixtures so as to cut grooves 2 and 7 communicated with both the side faces of the compact 1A, and, of the pair of fixtures, at least either one collapses the side face of the compact on the side through which at least the cutting tool 5 is pulled out from the cutting part of the compact 1A, and the part through which the cutting tool 5 is pulled out in the fixture has a similar figure larger than the groove formed by the cutting. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a sintered part, and more particularly to a method for manufacturing a sintered part in which a molded body obtained in a compacting process is cut before sintering.

  Filling the mold powder of the raw material powder mainly composed of metal powder and pressing it with a punch from above and below to form a product shape, sintering the resulting molded body and diffusion bonding the powder to metallurgy The powder metallurgy method to be bonded together is applied to various machine parts and the like because it can be shaped into a near net shape and can greatly reduce the labor of machining. However, when a recess is required in a direction perpendicular to the pressurizing direction of the punch, it is difficult to provide the recess at the time of molding. Generally, after sintering, a method of forming a recess by machining is employed. It has been. For example, as shown in FIG. 6, a machine having a cylindrical portion 61 and a convex portion 62 extending in the radial direction of the cylindrical portion 61, and the convex portion 62 having grooves 7 communicating with both side surfaces of the convex portion 62. When the parts are produced by the powder metallurgy method, a sintered body composed of the cylindrical part 61 and the convex part 62 is produced as shown in FIG. 7A, and the groove of the convex part 62 is accommodated as shown in FIG. 7B. The part 7a is manufactured by machining.

  However, the addition of such machining is a cause of cost increase due to an increase in the number of processes, and the cutting form is intermittently cut by the pores included in the sintered body, so that the machinability may be poor. This will increase the cost. For this reason, the state that the powders are not metallurgically joined, that is, if the machining is performed only on the molded body in which the powders are mechanically entangled, it is easy to machine, Machining of compacts has been studied and proposed for a long time. The manufacturing method of Patent Document 1 is one of such proposals, and is premised on cutting the molded body obtained in the compacting process before sintering, and is molded as a compacting process together with the raw material powder composition. By applying die lubrication molding that applies a lubricant to the die, the strength and quality of the sintered parts are improved while suppressing the occurrence of chipping of the molded product due to cutting.

JP 2004-323939 A

  In the above-mentioned Patent Document 1, application of mold lubrication molding (so-called mold lubrication method) because the component strength is reduced when using a method of using a lubricant mixed powder in which a lubricant is added to the raw material powder (so-called mixed lubrication method). In other words, with this mold lubrication molding, since the molded body reduces internal voids, the cutting form becomes continuous cutting, making it easier to suppress chipping of the molded body due to cutting and at the same time devising the raw material powder configuration Describes that both high strength and high quality of sintered parts can be achieved. However, even if the above-described mold lubrication method is used, the strength of the molded body does not increase dramatically. In any case, the powder is easily chipped because it is mechanically entangled with each other. Not a suggestion. Under such circumstances, the present inventors have studied the chipping phenomenon of the molded body that occurs when the molded body before sintering is subjected to cutting. However, it was found that the amount of chipping or breakage generated in the molded body can be greatly suppressed by devising the cutting form.

  The object of the present invention is to suppress the chipping of the molded product accompanying cutting before sintering, regardless of the material composition of the raw material powder and the molding using the lubricant mixed powder or the die lubrication molding in the compacting process, Accordingly, it is an object of the present invention to provide a practical cutting method of a molded body that can improve quality and yield, and to make sintered parts applicable to more fields.

  In order to achieve the above-described object, the present invention includes a compacting process for compressing a raw material powder, a cutting process for cutting the compacted compact, and a sintering process for sintering the compacted compact. In the method for manufacturing a sintered part, the cutting process is performed by constraining both side surfaces of the molded body by a pair of jigs having openings cut out from the upper surface part and both side surface parts, and opening parts of the two jigs. A step of cutting a groove communicating with both side surfaces of the molded body by passing a rotating cutting tool between them, and at least the cutting tool of the pair of jigs cuts the molded body. A jig for restraining the side surface of the molded body that is to be removed from the portion, wherein a portion of the jig from which the cutting tool comes out has a similar shape to that of the groove formed by cutting.

  In the present invention described above, “the part from which the cutting tool comes out of the jig” means, for example, that after the cutting tool comes out from one side of the molded body to the other side as shown in FIG. When it comes out from the other side to one side, it is an opening edge part corresponding to the code | symbol b and d of the figure among the opening parts of a jig | tool. On the other hand, when the groove is formed by the cutting tool slipping out from one of the two side surfaces of the molded body, the corresponding both edge portions of the opening of the jig on the side from which the cutting tool exits (FIG. ), For example, the opening both edge portions corresponding to symbols b and c on the side from which the cutting tool comes out.

The above-described production method of the present invention is more preferably embodied as follows. That is,
(1) Each of the pair of jigs includes a holding member in which the opening is formed in a substantially C-shaped step, and the holding member has an opening width in the C-shaped step with respect to opposite side surfaces of the molded body. It is the structure arrange | positioned in the state which contact | abutted the small side of each, respectively.
(2) The step (for example, d2 in FIG. 5B) between the portion of the jig from which the cutting tool comes out and the groove formed by cutting is configured to be 0.4 mm or less. ).

  In the first aspect of the invention, in the cutting process, a rotary cutting tool such as a milling cutter or an end mill is connected to the jig side opening in a state in which the opposite side surfaces of the molded body are constrained by a pair of jigs from the outside. And cutting while moving between both side surfaces of the molded body. In this case, of the pair of jigs, the jig that restrains the side of the molded body from which the cutting tool comes out of the cutting portion of the molded body, and the part from which the cutting tool comes out of the groove is formed by cutting. It has a large similar shape. For this reason, in the present invention, it is possible to greatly suppress the occurrence of chipping of the molded product due to cutting by the clamping force or restraining force of the jig, and as a result, the quality and yield can be improved. Moreover, since the cutting tool rotating with respect to the part to cut of a molded object is moved through a jig side opening part, workability | operativity can also be maintained favorable.

  In the invention of claim 2, each sandwiching member is disposed in a state where the side having a small opening width in the C-shaped step is in contact with both opposing side surfaces of the molded body, thereby cutting the molded body as in the embodiment. Of these parts, cutting can be efficiently performed including chamfering of the side edges of both side surfaces.

  In the invention of claim 3, the step between the corresponding portion of the jig where the cutting tool comes out from the cutting portion of the molded body and the groove is 0.4 mm or less, so that the cutting is performed by the clamping force or the restraining force of the jig. It is possible to more reliably suppress the occurrence of chipping in the molded product.

  Next, the best mode of the present invention will be described with reference to the drawings. The present invention provides, as a method for manufacturing a sintered part, a compacting process for compressing raw material powder, a cutting process for cutting the compacted compact, and a sintering process for sintering the compacted compact. In particular, the cutting tool and the cutting method in the cutting process are devised. Further, a description will be given by using a model in which the convex part 62 of the machine part shown in FIG. Hereinafter, the structural features of each process will be described in detail.

(Powdering step) In this step, a raw material powder prepared in advance is filled in a desired mold, and is compacted at a predetermined molding pressure, thereby forming a molded body as illustrated in FIG. 1A is made. Here, the raw material powder is only required to be used in ordinary powder metallurgy, for example, iron or iron alloy powder as a main material, other metal powder (copper, zinc, molybdenum, nickel, etc.) A mixed powder in which graphite powder or the like is mixed.

  Moreover, zinc stearate powder etc. may be added to the above mixed powder as a powder lubricant, for example. Of course, instead of adding a powder lubricant to the raw material powder, application of mold lubrication molding, that is, a lubricant film may be formed on the inner hole surface of the die. In this mold lubrication molding, when the mixed powder and the mold are warmed to about 100 ° C. to 140 ° C. for warm molding, the plastic deformation of the powder is facilitated, and the density and strength of the molded body can be made higher than that for cold molding. . The molding pressure is arbitrary, but is usually determined within the range of 500 Mpa to 900 Mpa according to the required density of the molded body 1A.

  The mold used in this process is designed according to the target sintered part. In general, if it is a block shape such as a prism, a base, or a rectangular body as in the molded body 1A of FIG. 1 (a), a die and an upper and lower punch are essential and used for the sintered part 6 with the groove 7 of FIG. In the case of a cylindrical molded body (molded body 6A without a groove 7), a core rod is required together with a die and upper and lower punches. Although the die may be fixed, it is preferable to employ a method in which the die is lowered with the lowering of the upper punch by the withdrawal method or the floating die method, because the powder can be more uniformly compressed.

(Cutting process) In this process, the molded body obtained in the compacting process is cut into a final part shape in a state where the molded body is positioned and held with respect to the cutting device. In this example, as shown in FIG. 1B, when the part to be cut of the molded body 1A communicates the opposite side surfaces 1a and 1a of the molded body and is substantially concave in cross section, the molded body 1A as shown in FIG. Using a jig provided with a pair of clamping members 3 that constrain the opposing side surfaces 1a, 1a from the outside and that expose the upper surface part and both side surface parts of the molded body 1A to be cut, Grooves 2 are formed in the molded body 1A while the rotating cutting tool 5 is moved between both side surfaces of the molded body 1A through the opening 4 of the clamping member 3 as shown in FIG. 4A.

  The cutting device used is a type that rotates a cutting tool 5 that is a cutting tool such as a milling machine or a machining center, and feeds and cuts the formed body 1A that is positioned and held via a jig and attachment means (not shown). I just need it. That is, the target molded body 1 </ b> A is held via attachment means such as a vise with respect to the cutting apparatus in a state of being restrained by the both clamping members 3. Both clamping members 3 have a thick plate shape that is slightly larger than the molded body 1A, have openings 4 and connecting holes 5 on both sides as shown in FIGS. 2 and 3, and are cut with the molded body 1A sandwiched therebetween. The upper surface portion and both side surface portions of the molded body 1A forming the portion to be exposed are exposed through the opening 4 or the like.

  Here, the sandwiching members 3 and 3 that are a pair of jigs are formed bodies that are located on the side of the corresponding sandwiching member side opening 4 side so that at least the cutting tool 5 is pulled out from the cutting portion (groove forming portion) of the shaped body 1A. The corresponding side surface of 1A is constrained in a state of approaching along the corresponding edge portion (groove forming portion) of the groove 2, or at least the side on which the cutting tool 5 comes out from the cutting portion (groove forming portion) of the molded body 1A. It is important that a portion of the jig that restrains the side surface of the molded body has a similar shape larger than the corresponding edge portion of the groove 2 formed by cutting. More specifically, the cutting tool 5 cuts the groove forming portion of the molded body 1A from the opening 4 of the one clamping member 3 as a first cutting method in a state where both the sandwiching members 3 restrain both side surfaces of the molded body 1A. And the groove | channel 2 is formed in 1A of molded objects by slipping out to the opening part 4 of the other clamping member 3. FIG. As a second cutting method, as shown in FIG. 4A, a part of the groove forming portion of the molded body 1A is cut from the corresponding portion of the opening 4 of the one clamping member 3 (for example, the left portion of the opening), After slipping out into the corresponding part of the opening 4 of the other clamping member 3 (for example, the left part of the opening), the molded body 1A again from the corresponding part of the opening 4 of the other clamping member 3 (for example, the right part of the opening). The remaining portion of the groove forming portion is cut, and on the other hand, the groove 2 is formed in the molded body 1A by slipping out to the corresponding portion of the opening 4 of the holding member 3 (for example, the right portion of the opening).

  The cutting process of the present invention may be any of the first and second cutting methods. However, in the first cutting method, the other holding member 3 is constrained in a state of being approached along the corresponding edge portion (groove forming portion) of the groove 2 of the molded body 1A. In the second cutting method, the other holding member 3 corresponds to a corresponding edge of the groove 2 of the molded body 1A (a corresponding portion of the opening 4 of the other holding member 3, for example, a left portion of the opening). , And the one clamping member 3 approaches along a portion corresponding to a corresponding edge of the groove 2 of the molded body 1A (corresponding portion of the opening 4 of the one clamping member 3, for example, the right portion of the opening). It is to restrain in the state. Further, the above approached state refers to a step d2 (preferably d2 is 0.4 mm or less) in FIG. In addition, as for the above structural features, the clamping member 3 which is a jig | tool which restrains the side surface of the molded object 1A in the side from which the cutting tool 5 comes off from the cutting part (groove formation part) of the molded object 1A as another way of grasping. Of these, the part that exits the cutting tool 5 has a similar shape to that of the groove 2 or the corresponding part of the groove 2.

  Further, the opening 4 is formed in a substantially C-shaped step, and among the sandwiching members 3, a side surface 3 a having a smaller C-shaped step opening width, and a side surface 3 b having a larger C-shaped step opening width, Is communicated. Moreover, each inner side surface 4a which divides the C-shaped step is inclined at an angle θ with respect to the side surface 3b as shown in FIG. This angle θ can be arbitrarily set as long as it is within the range of 20 to 90 °. However, when chamfering 2a is applied to the edge of the groove 2 cut as shown in FIG. 1 (c), the gradient or angle of the chamfering 2a. It is preferable to match t.

  Reference numeral 6 denotes a shaft inserted into the connecting holes 5 and 5 facing each other. The both clamping members 3 abut on the opposite side surfaces 1a, 1a of the molded body 1A with the side surface 3a having the smaller opening width in the C-shaped step, and are positioned via the shafts 6 on both sides. The molded body 1A is constrained in the above manner, and is attached to and detached from the attachment means of the cutting device in that manner.

  Furthermore, in this example, both the sandwiching members 3 are in contact with the opposite side surfaces 1a and 1a of the molded body 1A on the side having the smaller opening width in the c-shaped step, respectively, as shown in FIGS. Steps d1 and d2 for escaping the cutting tool 5 are set between the opening left and right edges 3c on the side having a smaller opening width and the cutting line S of the formed body 1A. In this setting, of the steps d1 and d2, the step d1 corresponding to the a portion and the c portion in FIG. 4A may be larger than 0.4 mm, but the step corresponding to the b portion and the d portion. d2, that is, the step d2 on the side where the cutting tool 5 moves from the cutting portion of the molded body 1A to the opening 4 (that is, the side from which the cutting tool comes out) is preferably 0.4 mm or less for the reason described later.

  FIG. 4A shows a state in which the groove 2 is formed by cutting in the molded body 1A positioned and held as described above, and an example of movement of the cutting tool 5 during cutting. In this example, after the rotating cutting tool 5 moves from one side of the opposite side surfaces 1a, 1a of the molded body 1A to the other side through the openings 4 of the sandwiching members 3, both side surfaces 1a. , 1a and cutting while moving from the other side to one side. More specifically, the cutting tool 5 is shown in the direction of the arrow, that is, the one inner surface 4a of the one opening 4 (4A), the cutting surface orthogonal to the side surface 1a, the one inner surface 4a of the other opening 4 (4B), the other The chamfer 2a and a part of the part a are moved along the other inner side face 4a of the opening 4 (4B), the cutting surface orthogonal to the side face 1a, and the other inner side face 4a of the one opening 4 (4A). The groove inner surface 2b between the b portion, the chamfer 2a of the b portion, the chamfer 2a of the c portion, the groove inner surface 2b between the c portion and the d portion, and the chamfer 2a of the d portion are continuously formed.

  In other words, with respect to the above step, the rotating cutting tool 5 moves to the cutting portion from the opening 4 shown in FIG. 5A with respect to the portion to be cut of the molded body as shown in FIG. In other words, the step d1 on the side where the cutting tool enters the cutting part (each step d1 between the part a and c in FIG. 4A) and the cutting part shown in FIG. There is a level difference d2 on the side where the cutting tool comes out (that is, the level difference d2 between the symbol b and d in FIG. 4A). And the present inventors discovered the following phenomena in the process of examining the manufacturing method of this invention. That is, the amount of chipping and damage caused by cutting is more likely to occur as the level difference (d1, d2) becomes larger, and the level difference d2 has a greater influence on the generation amount and the degree of occurrence than level difference d1. In particular, when the level difference d2 is larger than 0.4 mm, the amount of generation and the degree of generation tend to increase rapidly, while the amount of generation and the degree of generation do not change much even when the level difference d1 is larger than 0.4 mm. . These phenomena apply regardless of, for example, the specific composition of the raw material powder, whether the powder mixture is made into a lubricant mixed powder or die lubrication molding.

(Sintering process) In this process, the formed body 1A with the groove 2 formed as described above is sintered in a sintering furnace at a predetermined atmosphere and temperature. Sintering conditions are set according to the target sintered part, but usually a non-oxidizing atmosphere such as nitrogen gas is preferable, and the sintering temperature is in the range of 600 ° C to 1000 ° C. In addition, 1 A of molded objects with a groove | channel 2 of FIG.1 (b) cut the groove | channel 2 to 1A of molded objects obtained at the compacting process. Since the sintered part which sintered this becomes the same shape as 1A of molded objects with a groove | channel 2, the sintered part (1) was appended in the figure. In the method for manufacturing a sintered part as described above, even if the molded body 1A obtained in the compacting process is cut before sintering, molding is performed due to the clamping force or restraining force of the clamping member 3 that is a jig. The occurrence of chipping in the body can be greatly suppressed, thereby improving the quality and yield. Further, since the cutting tool 5 rotating with respect to the portion to be cut of the molded body 1A is moved through the opening 4 of the sandwiching member 3, workability can be maintained well, and among the portions to be cut of the molded body 1A, Cutting can be efficiently performed including chamfering 2a processing on the side edge portions of both side surface portions.

  The production method of the present invention can be variously modified except for the requirements specified in claim 1, and the specific composition of the raw material powder, the lubricant mixed powder in the compacting process, or die lubrication A cutting device or the like used for the molding or cutting process can be developed in various ways based on this form.

(A) The perspective view which shows the molded object obtained by the compacting process of this invention, (b)-(d) shows the molded object after cutting, (b) is a perspective view, (c) is a top view. (D) is a side view. The clamping member of the jig | tool used for this invention is shown, (a) is a top view, (b) is a side view. (A) And (b) is the top view and perspective view which show the state which clamped the molded object obtained at the compacting process with both clamping members. It is the top view and perspective view which show the state which cut the molded object of FIG. 3 with the cutting tool. (A) And (b) is the principal part enlarged view which expanded the a part (c part is the same) and b part (d part is the same) of FIG. It is a perspective view which shows the other example of a shape of the sintered component manufactured by the method of this invention. (A) And (b) is explanatory drawing which shows the conventional method of manufacturing the sintered component of FIG.

Explanation of symbols

1, 6 ... Sintered parts 1A, 6A ... Molded body before sintering (including molded body after cutting)
2,7 ... groove (2a is chamfered, 2b groove inner surface)
3 ... clamping member (a jig is comprised, 3a and 3b are side surfaces)
4 ... Opening (4a is the inside surface of the C shape)
5 ... Cutting tool

Claims (3)

In a method for producing a sintered part that undergoes a compacting step of compression-molding a raw material powder, a cutting step of cutting the compacted compact, and a sintering step of sintering the compacted compact,
A cutting tool in which the cutting step restrains both side surfaces of the molded body by a pair of jigs having openings cut out from the upper surface part and both side surface parts, and rotates between the openings of the two jigs. A step of cutting grooves communicating with both side surfaces of the molded body by passing through,
Of the pair of jigs, at least the cutting tool is a jig for restraining the side of the molded body on the side from which the cutting part of the molded body comes off, and a portion of the jig from which the cutting tool comes out is formed by cutting. A method for producing a sintered part, which is similar in shape to the groove.   Each of the pair of jigs includes a clamping member in which the opening is formed in a substantially C-shaped step, and the clamping member is on a side having a small opening width in the C-shaped step with respect to opposite side surfaces of the molded body. The manufacturing method of the sintered component of Claim 1 arrange | positioned in the state which each contact | abutted.   The method of manufacturing a sintered part according to claim 1 or 2, wherein a step between the portion of the jig from which the cutting tool comes out and the groove formed by cutting is 0.4 mm or less.

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