JPH11140507A - Correcting method for 2p2s process sinter, and correction die unit used in the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of defective correction on a stepped part side of a projecting part in correcting a work having the projecting part on one side of an outer peripheral surface in a 2P2S process sinter of the powder metallurgy. SOLUTION: A die 36 is supported in a vertically movable manner relative to a die plate 21 in the prescribed range, and pressed upward by a spring 33. When a work 1 is mounted in the die 36, a projecting part 2 of the work 1 is abutted on a stepped part 37 of the die 36 from the initial stage. An outer peripheral surface of the work 1 can be prevented from being swollen when pressurized. The die 36 is lowered by the prescribed quantity against the pressing of the spring 33 by pressing with an upper punch 46, and in the middle thereof, the work 1 is brought into contact with a lower die 42. The compression ratio of the projecting part 2 of the work 1 becomes equal to that of other part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a straightening method used for a repress resinter in powder metallurgy comprising a powder compacting step, a preliminary sintering step, a straightening step, and a main sintering step, and a straightening mold used in this method. Related to the device.

[0002]

In powder metallurgy, a raw material powder is compression-molded to form a green compact, and the green compact is heated at a low temperature, temporarily sintered, and then re-compressed into a sintered body. Is performed to increase the density of the sintered body, and further, the sintered body is heated at a higher temperature than during the preliminary sintering to perform the main sintering. This is a so-called repress resinter. The correction is also called coining and the like, and is aimed at improving physical properties. In particular, the repress resinter is intended to increase the density of the sintered body. For this reason, in temporary sintering before straightening, the heating temperature is lowered so that the sintered body can be greatly crushed during straightening.

FIG. 4 shows an example of a work 1 made of a sintered body subjected to such correction. This work 1
Has a substantially cylindrical shape, but has a convex portion 2 on one end side of the outer peripheral surface. 6 and 7 show an example of a correction mold device used for correcting the work 1. Reference numeral 11 denotes a die plate, and a stepped die 12 is fixed to the die plate 11 by a die holder 13. Die 12
Has a substantially cylindrical shape with the vertical direction as the axial direction, and forms the outer peripheral surface of the work 1 including the convex portion 2. On the inner peripheral surface of the die 12, an upward horizontal step portion 14 forming the lower surface of the convex portion 2 is formed. Also,
Reference numeral 15 denotes a core rod. The core rod 15 has a cylindrical shape with the vertical direction as the axial direction, is coaxially located in the die 12, and forms the inner peripheral surface of the work 1.
The positions of the die 12 and the core rod 15 are fixed, and the upper surface of the die 12 and the upper end of the core rod 15 are positioned at the same height. Also, 16 is a lower punch, and this lower punch 16
The die has a cylindrical shape with the vertical direction as the axial direction.
The lower end surface of the work 1 is formed between the core 12 and the core rod 15 so as to be freely slidable from below. Further, reference numeral 17 denotes an upper punch. The upper punch 17 has a cylindrical shape whose axial direction is the vertical direction. Together, they form the upper end surface of the work 1.

When straightening, the upper punch 17 is pulled upward from between the die 12 and the core rod 15, and the lower punch 16 is raised, and the upper punch 17 is positioned at the same height as the upper surface of the die 12. The work 1 is carried onto the work 16.
Next, the lower punch 16 descends, and the work 1 descends together with the lower punch 16 and is loaded between the die 12 and the core rod 15. FIG. 6 shows the state at the time of completion of the loading,
In this state, the work 1 remains on the lower punch 16, and the convex portion 2 of the work 1 is located upward away from the step 14 of the die 12. Pressurization also starts from this position. And
As shown in FIG. 7, the upper punch 17 descends and fits between the die 12 and the core rod 15, and the die 12 and the core rod
When the work 1 is pressurized by the punches 16 and 17 between the positions 15, the work 1 is recompressed and corrected. During this pressurization, the convex portion 2 of the work 1 is
Then, the convex portion 2 is compressed by the step portion 14 of the die 12 and the upper punch 17. As described above, since the compression of the convex portion 2 starts later than other portions of the work 1,
The compression allowance of the work 1 is larger in the other portions than in the convex portions 2, and the compression ratio is equal in each of the portions. After the pressurization is completed, the upper punch 17 rises again and comes out of the space between the die 12 and the core rod 15, and the lower punch 16 rises and the die
The work 1 is extracted from between the core rod 12 and the core rod 15.
Thereafter, the recompressed work 1 is carried out and the next work 1 is carried in, and the above steps are repeated.

For example, in the case of the work 1 having a length of about 20 mm, the compression allowance is about 0.4 mm in the case of ordinary straightening performed after sintering in powder metallurgy in which sintering is performed only once. However, in the case of correction in the repress resinter,
The compression allowance is about 2.5 to 3 mm, and the pores in the work 1 made of a sintered body are almost crushed. In particular, when the compression allowance is large as described above, in the above-described conventional straightening method and straightening mold apparatus, pressurization is started in a state where the convex portion 2 of the work 1 is floating from the step portion 14 of the die 12 as follows. Problems had arisen. That is, during pressurization, the portion of the outer peripheral surface of the work 1 below the convex portion 2 and above the step portion 14 of the die 12
Since it is not regulated by 12, the bulging portion 3 bulges outward as shown in FIG. The bulging portion 3 is crushed separately from the convex portion 2, and therefore, the convex portion 2 of the work 1 after recompression.
Has a narrow groove 4 at the bottom as shown in FIG. 8, and the work 1 is defective.

An object of the present invention is to solve such a problem, and a straightening method for a repress resinter which can prevent occurrence of poor straightening when straightening a work having a convex portion in the repress resinter. An object of the present invention is to provide a straightening mold device used in this method.

[0007]

According to a first aspect of the present invention, there is provided a straightening method for repress resintering, wherein a raw material powder is compressed to form a green compact, and the green compact is reduced. A prepress sinter that is pre-sintered by heating at a temperature, and the sintered body obtained by the pre-sintering is recompressed and straightened, and the sintered body after the straightening is heated at a high temperature and fully sintered. Is a correction method used in the method, the work having a convex portion on one end side of the outer peripheral surface in a stepped die by one side punch located on the convex side and the other side punch located on the opposite side to the convex portion In the straightening method of straightening by pressing, the pressing by the one-side punch is started in a state where the convex portion of the work is in contact with the step in the die, and the die is pressed by the one-side punch in accordance with the pressing by the one-side punch. After moving a predetermined amount in the pressure direction by the side punch, stop the die and pressurize Is performed.

As described above, since the convex portion of the work is in contact with the step of the die from the beginning of pressurization, the entire outer peripheral surface of the work is reliably regulated by the die, and the outer peripheral surface of the work is incorrectly deformed. Can be prevented. In addition, after the die moves by a predetermined amount in the pressing direction by the one-side punch due to the pressing by the one-side punch, the die is stopped and the pressing by the punch is continued, so that the work allowance of the work is smaller than that of the convex part. Other parts are larger. Thus, although the convex portion of the work comes into contact with the step of the die from the beginning of the pressurization, the compression allowance becomes predetermined at each of the convex portion of the work and other portions.

According to a second aspect of the present invention, in the straightening method for a repress resinter according to the first aspect of the present invention, the work is located away from the other side punch at the time of starting pressing by the one side punch, and The workpiece comes into contact with the other side punch in the middle of the movement.

[0010] If the work is positioned away from the other-side punch at the time of starting pressurization as described above, the convex portion of the work can reliably contact the step of the die from the time of start of pressurization. Then, when the die slightly moves due to the pressure of the one-side punch, the work comes into contact with the other-side punch, and the pressure is applied by the other-side punch.

According to a third aspect of the present invention, there is provided a straightening die apparatus used in the straightening method for a repress resinter according to the first or second aspect, wherein one side of the inside is formed as a thick hole by the step portion and the other side is narrower. A die having a pore portion, a one-side punch that is slidably and removably fitted into the die from the thick hole portion side, and a slide from the pore portion side within the die. A die plate for holding the die; a die plate for holding the die; the die is movable in a predetermined range with respect to the die plate in a moving direction of the punch; It is urged toward the one punch side by means.

In the die, when pressure is started by the one-side punch in a state where the convex portion of the work is in contact with the stepped portion, the die is pressed by the one-side punch in a direction against the urging by the urging means. Move to. Then, the die stops after moving the predetermined range, and thereafter, the convex portion of the work is also compressed by the step portion of the die and the one-side punch.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a straightening method for a repress resinter according to the present invention and a straightening mold apparatus used in the method will be described below with reference to FIGS.
The work 1 to be corrected, which is the recompression, is the work 1 shown in FIG. 4 described above.

First, the configuration of the mold apparatus will be described. 21 is a die plate, and this die plate 21 is a lower die plate member.
The upper die plate member 23 is fixed on the upper surface 22 and has a hole 24 vertically penetrating therethrough. And this hole 24
An annular recess 25 is formed on the inner peripheral surface of the. This recess
25 has an upwardly directed lower stepped surface 26 formed by the lower die plate member 22 at the lower end, and has a downwardly directed upper stepped surface 27 formed by the upper die plate member 23 at the upper end. A substantially cylindrical die holder is provided in the hole 24.
31 are fitted and held slidably in the up-down direction.
The die holder 31 has a convex portion 32 located in the concave portion 25 of the hole 24 on the outer peripheral surface, and biases the lower surface of the convex portion 32 and the lower step surface 26 of the concave portion 25. A plurality of springs 33 as means are mounted. In addition, die holder 31
A spring retainer 34 for pressing the spring 33 from below is fixed to the lower surface of the. In this manner, the die holder 31 can move freely within a predetermined range between the upper limit position where the convex portion 32 contacts the upper step surface 27 of the concave portion 25 and the lower limit position where the spring 33 is compressed to the maximum. Along with
The spring 33 urges the spring upward.

A substantially cylindrical stepped die 36 whose axial direction is the vertical direction is fixed to the inner peripheral side of the die holder 31. The die 36 has a horizontal upward step 37 on the inner peripheral surface, and the inside of the die 36 has a thick hole above the step 37.
38, and the lower side of the step portion 37 is a narrower pore portion 39. The die 36 forms the outer peripheral surface of the work 1, and forms the lower surface (step portion) 5 of the convex portion 2 of the work 1 by the step portion 37. The upper surface of the die 36 and the upper surface of the die holder 31 are located on the same horizontal plane, and the upper surfaces of the die holder 31 and the die 36 are located at the same height as the upper surface of the die plate 21 at the upper limit positions. .

Reference numeral 41 denotes a core rod whose axial direction is the vertical direction. The core rod 41 is located at the center of the die 36 and forms the inner peripheral surface of the work 1. The position of the core rod 41 is fixed together with the die plate 21, and the upper surface is located at the same height as the upper surface of the die plate 21.

Reference numeral 42 denotes a lower punch as the other-side punch. The lower punch 42 has a substantially cylindrical shape whose axial direction is the vertical direction. It is slidably fitted into the portion 39 from below.
That is, the lower punch 42 forms the lower end surface of the work 1 on the side opposite to the convex portion 2. The lower punch 42 is fixed on a lower punch plate 44 via a holder 43,
It moves in the vertical direction together with the lower punch plate 44.

Reference numeral 46 denotes an upper punch as a one-side punch. The upper punch 46 has a substantially cylindrical shape whose axial direction is the vertical direction, and is located on the outer peripheral side of the core rod 41 and has a large hole in the die 36. It is slidably and removably fitted into the portion 38 from above. That is, the upper punch 46 is the work 1
Is formed on the upper end surface on the convex portion 2 side. The upper punch 46 is fixed to a lower side of an upper punch plate (not shown), and moves up and down together with the upper punch plate.

Next, a straightening method using the mold apparatus will be described. In the repress resinter, the raw material powder is compression molded by a powder molding press to produce a green compact, and this green compact is heated at a low temperature by a sintering furnace and temporarily sintered,
The density of the sintered body is increased by performing a recompression correction on the sintered body by a straightening press in which the straightening mold device is assembled, and the sintered body is further heated by a sintering furnace at a higher temperature than at the time of the preliminary sintering. To perform main sintering.

FIG. 1 shows a state when the work 1 is extracted after the straightening and when the work 1 is carried in. In this state, the upper punch 46 is pulled upward from the die 36 and the core rod 41, the die 36 is at the upper limit position by the bias of the spring 33, and the lower punch 42 is also raised, so that the upper end surface thereof is
It is located at the same height as the upper surface of 36. In this state, the lower punch 42
The work 1 is carried on. Thereafter, the lower punch 42 descends as shown in FIG. 2, and the work 1 placed on the lower punch 42 is loaded between the die 36 and the core rod 41. When this loading is completed, the convex portion 2 of the work 1 contacts the step 37 of the die 36, but the lower end surface of the work 1 is
Slightly upward from the upper end surface of the. Pressurization starts in this state.

That is, the lowering upper punch 46 is fitted between the die 36 and the core rod 41 and comes into contact with the upper end surface of the work 1 as shown by a chain line in FIG.
In the initial stage of this pressing, the upper punch 46 presses the die 36 together with the die holder 31 against the bias of the spring 33.
Decreases by a predetermined amount. Work 1 during the lowering of this die 36
Is in contact with the upper end surface of the lower punch 42. At this point, pressurization by the lower punch 42 starts, and the work 1 is compressed by the lower punch 42 and the upper punch 46. In addition, die
After 36 reaches the lower limit and stops, upper punch 46 and die 36
The convex portion 2 of the work 1 is also compressed by the step portion 37. FIG.
Indicates the time point when the pressurization is completed.

Thereafter, the upper punch 46 is attached to the die 36 and the core rod.
41, the die 36 is also raised to the upper limit position by the bias of the spring 33. Also, lower punch 42
Rises to the position shown in FIG. 1 and the work 1 is extracted from between the die 36 and the core rod 41. Thereafter, the recompressed work 1 is carried out and the next work 1 is carried in, and the above steps are repeated.

According to the above-described straightening method, since the convex portion 2 of the work 1 is in contact with the step portion 37 of the die 36 from the beginning of pressurization, the outer peripheral surface of the work 1 from the start to completion of pressurization. Even though the whole is reliably regulated by the die 36 and is a repress resinter, the outer peripheral surface of the work 1 can be prevented from being deformed improperly even if the compression allowance is large, and the correction failure can be prevented. That is, it is possible to prevent the bulging portion 3 and the groove portion 4 from being formed below the convex portion 2 of the work 1 as in the related art.

Further, since the die 36 can be moved up and down with respect to the die plate 21 within a predetermined range and is urged upward by the spring 33, the convex portion 2 of the work 1 can be moved from the beginning of the pressing to the step of the die 36. Despite contact with the part 37, the compression allowance can be set separately for the convex part 2 of the work 1 and other parts. In other words, the die
After the 36 has been lowered by a predetermined amount, the die 36 stops and the punches 42, 46
, The allowance for the compression of the work 1 is larger in the other portion than in the convex portion 2. Thereby, the compression allowance can be set to a predetermined value at each of the convex portion 2 and the other portions of the work 1.

In addition, at the time of starting pressurization, the work 1 is positioned so as to slightly float from the lower punch 42. Therefore, even if there is a dimensional error, for example, the convex portion 2 of the work 1 is moved from the start of pressurization to the die. Make sure to contact the step 37 of 36. Therefore, it is possible to more reliably prevent a correction failure from occurring on the lower surface 5 side of the convex portion 2 of the work 1.

Further, the structure of the mold apparatus in which the die 36 is supported on the die plate 21 so as to be movable up and down and the die 36 is urged upward by the spring 33 is simple. And the reliability of operation is high.

The present invention is not limited to the above-described embodiment, and various modifications can be made. For example,
In the above embodiment, the biasing means for biasing the die 36 upward with respect to the die plate 21 is a spring, but the biasing means is not limited to this, and may be an air cylinder or the like. However, if a spring is used as in the above-described embodiment, the configuration of the mold apparatus becomes simple, and the cost required for mold production can be reduced. As shown in FIG. 4, the work 1 to be corrected has a convex portion 2 on the entire circumference at one end of the outer peripheral surface.
Is not limited to a flange-like shape, and one or a plurality of protrusions 2 may be partially provided on one end side of the outer peripheral surface as shown in FIG.

[0028]

According to the method for correcting a repress resinter according to the first aspect of the present invention, the one-side punch positioned on the side of the convex portion with the convex portion on one end side of the work abutting the step portion in the die. After the die is moved by a predetermined amount in the direction of pressurization by the one-side punch,
Since the die is stopped and pressure is applied, even if the compression allowance is large due to the repress resintering, a predetermined compression allowance is maintained at each of the convex portion and other portions of the work, while the step of the convex portion is maintained. It is possible to prevent the correction failure from occurring on the part side.

According to the correction method for a repress resinter of the second aspect of the invention, in addition to the effect of the first aspect of the invention, at the time of starting pressurization by the one-side punch, the work is positioned away from the other-side punch. Since the work comes into contact with the other side punch during the movement of the die, the convex portion of the work can be reliably brought into contact with the step portion of the die from the start of pressurization, and straightening is performed on the step side of the convex portion. The occurrence of defects can be more reliably prevented.

According to the correction mold apparatus of the third aspect of the present invention, the die having the step portion is movable in a predetermined range in the moving direction of the punch with respect to the die plate.
Since the urging means is urged toward the one-punch side, the straightening method according to claim 1 or 2 can be performed with a mold device having a simple structure.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a correction mold apparatus according to an embodiment of the present invention, showing a state before a workpiece is loaded.

FIG. 2 is a cross-sectional view of the correction mold apparatus, showing a state where a work is loaded.

FIG. 3 is a cross-sectional view of the correction mold apparatus, illustrating a state in which the work is pressurized.

FIG. 4 is a perspective view showing an example of a work to be corrected.

FIG. 5 is a perspective view showing another example of a work to be corrected.

FIG. 6 is a sectional view showing an example of a conventional correction mold device.
This shows a state where the work is loaded.

FIG. 7 is a sectional view of the same, showing a point in time when the pressing of the work is completed.

FIG. 8 is a cross-sectional view of the corrected work.

[Explanation of symbols]

 1 Work 2 Convex part 21 Die plate 33 Spring (biasing means) 36 Stepped die 37 Step part 38 Thick hole part 39 Hole part 42 Lower punch (other side punch) 46 Upper punch (one side punch)

Claims (3)

[Claims] 1. A method for compressing a raw material powder to form a green compact, heating the green compact at a low temperature, temporarily sintering, and recompressing a sintered body obtained by the temporary sintering. Straightening, a straightening method used in a repress resinter that heats the sintered body after the straightening at a high temperature and performs main sintering, wherein the work having a convex portion on one end side of the outer peripheral surface is placed in a stepped die. In a straightening method in which one side punch located on the convex side and the other side punch located on the opposite side to the convex are pressed in the axial direction and straightened, the convex part of the work abuts the step in the die. In this state, pressurization by the one-side punch is started, and after the die is moved by a predetermined amount in the pressurizing direction by the one-side punch in accordance with the pressurization by the one-side punch, the die is stopped to perform pressurization. A straightening method for repress resintering, which is performed. 2. The method according to claim 1, wherein the work is located apart from the other punch at the start of pressurization by the one punch, and the work contacts the other punch during the movement of the die. Item 2. A method for correcting a repress resinter according to item 1. 3. A straightening die apparatus used in the straightening method for repress resinter according to claim 1 or 2, wherein the step forms a large hole on one side and a narrower hole on the other side. A die, a one-side punch slidably and removably fitted into the die from the large hole side, and a slidably fitted slidably from the fine hole side into the die. And a die plate for holding the die, wherein the die is movable in a predetermined range in the direction of movement of the punch with respect to the die plate, and the one side is biased by biasing means. A straightening mold device, which is biased toward a punch side.