JP3225663B2 - Fracture separation method for sintered material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for fracture separation of a sintered material, which method can be used for producing a sintered material split bearing, for example, a connecting rod large end bearing of an internal combustion engine.

[0002]

2. Description of the Related Art In order to improve the yield of materials and reduce costs, parts having split bearings such as connecting rods are sometimes made of a sintered material. JP-A-64-647
No. 29 discloses that a V-groove is formed in advance by machining at a portion of the inner peripheral surface of the large end hole that is to be broken and separated in order to separate the large end of the sintered material connecting rod into the rod body and the cap. Discloses a method of separating the fracture by using the fracture as a starting point of the fracture.

[0003]

However, the above-mentioned conventional method requires a machining step for forming a V-groove, which leads to an increase in cost. Further, a break-off force is applied to generate a crack from the V-groove. Also, since the V-groove does not extend in the direction in which the crack is to propagate, the crack may propagate in a direction other than the plane in which the fracture is to be separated, and may not be used as a split bearing.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sintered material capable of forming a crack propagation guide crack which does not require machining to form a crack serving as a starting point at the time of fracture separation and extends over the entire length in the direction in which the crack should propagate. Of the present invention is to provide a fracture separation method.

[0005]

Means for Solving the Problems A method for breaking and separating a sintered material according to the present invention for achieving the above object comprises the following methods. That is, the sintered material powder is filled into a predetermined cavity and molded under pressure to form a molded product. The molded product is sintered to form a sintered product. After cooling the sintered product, the sintered product is fractured and separated. In the method of breaking and separating a sintered material into at least two split parts, in the step of pressing the sintered material powder, one side of the surface of the sintered material powder filled in the cavity to be fractured and separated is provided. Pressing and molding a certain first portion with a first punch to form a step between the first portion and a second portion on the other side of the fracture separation surface, and thereafter, the sintered material filled in the cavity The second portion of the powder is formed separately from the first punch by a second punch which is in sliding contact with the first punch, and pressure-formed to embed the side surface of the step in the sintered material powder. By forming a crack extending along the fracture separation scheduled surface at the pressing direction end surface of the powder molded product, Fracture separation method of the sintered material to fracture splitting the sinter at fracture separation process of the serial sinter along the crack.

[0006]

In the method of the present invention, when the first portion of the cavity filling powder is pressed and molded with the first punch, a step is generated at the end of the cavity filling powder in the pressing direction. Subsequently, the second part of the cavity filling powder is pressure-molded to the same level as the first part by the second punch.
The side of the step sinks into the cavity filling powder,
Although the back side is united with the cavity filling powder, near the end face in the pressing direction, a fault that does not bond with the filling powder occurs, and this forms a crack that serves as a starting point of fracture separation.

This crack can be formed on both sides of the fracture-separation-scheduled surface simply by increasing or decreasing the pressure, and the formation thereof does not require machining, thereby enabling cost reduction. Also,
Since the crack extends over the entire line along the fracture separation plane, the crack is easily propagated along the fracture separation plane, and the fracture separation direction is stabilized.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In one embodiment of the present invention, there is provided a method for separating a sintered material into fractures by filling a predetermined amount of sintered material powder into a cavity and press-forming the molded product to form a molded product. And a step of breaking and separating the sintered product after cooling to form at least two split parts. The method of the present invention may further include the step of reassembling the split parts together at the fracture surface to form a split part assembly. The method of the present invention is characterized in that a crack is formed as a starting point of a crack at the time of fracture separation in the pressure molding step.

[0009] The above-described method for separating a sintered material into fractures may include a hot forging step between the sintering step and the fracture separation step. If there is no forging process, the split component assembly is a sintered product, and if it has a forging process, the split component assembly is a sintered forged product (included in the sintered product). The above-mentioned split part assembly is composed of, for example, a sintered product connecting rod of an internal combustion engine, and the split parts are a rod body and a large end cap. However, the split part assembly is not limited to the connecting rod. For example, the split part assembly is a disc-shaped sintered product,
The split part may be a semicircular part.

In order to facilitate understanding of the present invention, the pressure forming step of the method of the present invention will be described with reference to FIGS. First, as shown in FIG. 1, for example, a sintered material powder 2 in which powders of Fe, 2% Cu, 0.6% graphite, and 0.8% zinc stearate are mixed for 20 minutes is prepared. Raise die 4,
The sintering powder 2 is filled in a cavity formed by the lower punches 8 and 12 and the die 4.

The lower punch 8 is held by an air cylinder capable of generating a pressing force P ₁ ′, and the lower punch 12 is held by a hydraulic cylinder capable of generating a pressing force P ₂ ′. The upper punches 6 and 10 located above the cavity have not yet pressed the sintered material powder 2. The hydraulic cylinder 14 the upper punch 6 is put out a pushing force P ₂
In is supported, the upper punch 10 is supported by the air cylinder 18 to put out a pushing force P _1. Between the pressing forces, P ₁ <
P ₂ ′, P ₁ ′ <P ₂ . The upper punch 6 and the lower punch 8 constitute a first punch for pressing the first portion 2a of the sintered material powder 2, and the upper punch 10 and the lower punch 12 apply a second portion 2b of the sintered material powder. A second punch to be pressed is formed.

Next, as shown in FIG. 2, the upper ram of the press is lowered, and the upper punches 6, 10 are lowered. At this time, the second portion 2b on the left side of the filling powder 2 is
Due to the relationship of P ₁ <P ₂ ′, the piston of the air cylinder 18 escapes to keep the pressing force at a small pressing force P ₁ . On the other hand, filling powder 2
Is pressed by a large pressing force because of the relationship of P ₂ > P ₁ ′. At this time, the first
A shift occurs between the portion 2a and the second portion 2b, and a step having a surface 22 in contact with the side surface of the upper punch 6 of the first punch is formed at the upper end of the second portion 2b. Similarly, at the lower end of the first portion 2a, a step having a surface 24 in contact with the side surface of the lower punch 12 of the second punch is generated. The height of the step is about 6 to 7 mm.

When the upper ram is further lowered from the above state, the pressing force of the upper ram is applied to the air cylinder 18 at the stroke end state, and the pressing force of the hydraulic cylinder 20 is weaker than the pressing force of the upper ram. The punch 10 is in the second part 2
Pressing b, the lower punch 12 also descends, and finally, as shown in FIG. 3, the upper punches 6, 10 are at the same level, and the lower punches 8, 12 are also at the same level.

During the transition from the state shown in FIG. 2 to the state shown in FIG. 3, relative movement occurs between the first portion 2a and the second portion 2b of the filling powder 2. Then, the surfaces 22 and 24 of the steps which were in contact with the side surfaces of the punches 6 and 12 are buried in the filling powder, and generate the faults 2c and 2d near the end surfaces in the pressing direction.
The faults 2c and 2d are hardly integrated with the opposing members and remain as cracks, and the crack surfaces are oxidized in the next sintering step to form cracks with sharp tips at the back. The cracks 2c and 2d slightly flow toward the opposing member and are formed obliquely. Crack 2c, 2
The depth d is higher as the height of the step is higher, but when the height of the step is 6 to 7 mm, the depth of the cracks 2c and 2d is about 400 microns. Thus, a crack that serves as a starting point of fracture separation can be formed during the molding process of the powder molded article. The crack is formed on the pressing end face of the pressing material over the entire line in a direction perpendicular to the pressing direction. The density of the molding material is 6.6 ~
It is about 7.0 g / cm ³ .

Next, as shown in FIG. 4, the die 4 is lowered relative to the lower punches 8 and 12, the upper ram is raised, and the molding material 2 is removed. This molding material 2 is sent to a sintering step, where it is sintered at about 1100 ° C. in a reducing atmosphere. Subsequently, hot forging is performed as necessary. Since the crack is taken out of the sintering furnace and placed in the atmosphere during transportation, the surface has already been oxidized. Therefore, even if hot forging is performed, the crack portion does not recombine and the crack does not disappear. Next, in the fracture separation step, the sintered material is fractured, but cracks are generated along the cracks, and the direction of separation is stabilized. Next, the separated split parts are re-assembled with the fractured surfaces aligned. The fracture surface is jagged and fits as it is jagged. This prevents a slip displacement from occurring in the fracture surface. Also, the work of machining the fractured surface becomes unnecessary.

FIG. 9 shows a state in which the apparatus shown in FIGS. 1-4 is assembled to an existing press apparatus. In FIG. 9, the die 4 is fixed to a die holder 26, and the lower punches 8 and 12 are air,
The lower punch pressure plate 28 is supported by the punch plate 30 via the hydraulic cylinders 16 and 20. The die holder 26 is connected to the base plate 32 via the guide post 34. Die holder 2
The punch plate 6 and the punch plate 30 can move vertically. On the other hand, the upper punches 6 and 10 are hydraulic and air cylinder 1
The upper punch pressure plate 36 is supported by the upper punch plate 38 via the upper and lower punch pressure plates 36 and 38. The upper punch plate 38 is fixed to the upper ram 42 of the press. The upper punch plate 38 and the die holder 26 can move relative to each other in the vertical direction, and the upper die guide post 40
Are aligned.

FIGS. 1 to 4 and FIG. 9 show the case in which the upper and lower punches are divided into two parts. However, by dividing only the upper punch or only the lower punch into two parts, the pressing direction of the molding material is reduced. It is also possible to generate a crack only on one end face.

FIGS. 5 to 8 show a case where the present invention is applied to a sintered forged connecting rod 2 '. In this case, the split part assembly is connected to the connecting rod 2 '.
And the split parts are the rod body 2a 'and the cap 2
b '. In the step of pressing the molded product of the sintered material powder, pressure is applied in the axial direction of the large end hole. The outer periphery of the large end is fixed with a die, a core is inserted in the large end hole, and the large end is pressed in the axial direction of the large end hole with a two-part punch.

When the step between adjacent punches is 6 to 7 mm, as shown in FIG.
0 micron cracks 2c 'and 2d' are formed. FIG. 5 shows that the cracks 2c 'and 2d' are formed over the entire line from the inner circumference to the outer circumference of the large end hole, and FIG. 6 shows the cracks 2c 'and 2d'.
2d 'is formed on both end surfaces of the large end in the pressing direction.

After sintering and forging this pressure-molded product 2 ', it is broken and separated. The break separation is performed by, for example, the large end hole 2e '.
This is performed by inserting a split die (not shown) into the slits, driving a wedge (not shown) between the split dies, and applying an expanding force to the large end hole 2e '. Cracks are generated from the cracks 2c 'and 2d' on the upper and lower surfaces of the large end hole, and are guided and propagated in the outer peripheral direction of the large end by the cracks 2c 'and 2d' in a plan view. Further, as shown in FIG. 7, in a sectional view, the upper and lower cracks 2c 'and 2d' are broken so as to connect the tips. The cracked surface is jagged, and when the split parts are reassembled and bolted, the rod body 2a '
And the cap 2b 'are prevented from shifting in the direction perpendicular to the longitudinal direction of the connecting rod.

The sintered product and the sintered forged product have brittleness,
Although the elasticity is small (about 5%), the large end hole 2e 'is deformed at the time of breaking and separating, so that the large end hole 2e' is processed into a perfect circle after breaking and separating. A bearing metal is mounted on this, and the pin of the crankshaft is rotatably inserted.

[0022]

According to the present invention, the first portion of the sintered material powder filling is pressurized by the first punch, and the first portion and the second portion are pressed.
A step is formed between the step and the second part, and then the second part is pressed with a second punch so that the side surface of the step is sunk into the powder to form a crack in an unbonded state. Therefore, it is not necessary to form a V-groove or the like, which is a starting point of a crack, by machining as in the related art, thereby reducing the number of steps and cost. Further, since the crack is formed along the fracture separation plane, the crack can be guided and propagated by the crack during the fracture separation step, and the direction of the crack can be stabilized.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an apparatus for performing a method for separating and breaking a sintered material according to one embodiment of the present invention, in a powder-filled state.

FIG. 2 is a schematic cross-sectional view of the apparatus of FIG. 1 in a state where powder is press-formed with a first punch.

FIG. 3 is a schematic cross-sectional view of the apparatus of FIG. 1 in a state in which powder is pressed by a second punch following pressing of a first punch.

FIG. 4 is a schematic sectional view of the apparatus of FIG. 1 in a state where a powder molding material is taken out.

FIG. 5 is a plan view of a connecting rod manufactured by applying a fracture separation method for a sintered material according to another embodiment of the present invention.

FIG. 6 is a side view of the connecting rod of FIG. 5 after crack formation.

FIG. 7 is a side view of the connecting rod of FIG. 6 after fracture separation.

FIG. 8 is an enlarged view of the vicinity of a crack in the connecting rod of FIG. 6;

FIG. 9 is a schematic front view of a press device to which the device of FIG. 1 is assembled.

[Explanation of symbols]

 2 Sintered material powder 2a First part 2b Second part 2c Crack 2d Crack 2 'Connecting rod 2a' Rod body 2b 'Cap 2c' Crack 2d 'Crack 2e' Large end hole 4 Die 6 Upper punch (first Punch) 8 Lower punch (first punch) 10 Upper punch (second punch) 12 Lower punch (second punch) 14 Hydraulic cylinder 16 Air cylinder 18 Air cylinder 20 Hydraulic cylinder 22 Surface of step 24 Surface of step

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B22F 3/24 B22F 3/02 F16C 7/02 B26F 3/04

Claims (1)

(57) [Claims] A sintering material powder is filled in a predetermined cavity and is molded under pressure to form a molded product. The molded product is sintered into a sintered product. After cooling the sintered product, the sintered product is cooled. In the method of breaking and separating a sintered material into at least two split parts by breaking and separating, in the pressure molding step of the sintered material powder, the surface of the sintered material powder filled in the cavity may be a surface to be fractured and separated. The first part on one side was pressure-formed with a first punch to form a step with the second part on the other side of the surface to be broken and then filled into the cavity. The second part of the sintered material powder is separately formed from the first punch by pressure molding with a second punch that is in sliding contact with the first punch,
By embedding the side surface of the step in the sintered material powder, a crack is formed at the end face in the pressing direction of the powder molded product along the fracture separation expected surface, and the crack is formed along the crack in the fracture separation step of the sintered product. And separating the sintered product by breaking.