JPS5825721B2 - Mold for powder molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder molding mold, and particularly to a powder molding mold for molding metal powder, etc. in powder metallurgy.

The general manufacturing method for ferrous sintered alloys for machine structures is to first mix copper powder, graphite powder, etc. with iron powder, which is the main component of the alloy, and then pour these mixed powders into mold cavities of various shapes. The density is usually 6.0 to 7.0 at room temperature. Og
Pressure mold until it reaches about lcd.

Next C, the molded body is placed in a non-oxidizing gas atmosphere such as ammonia decomposition gas or endothermic gas to
Heat and sinter at a temperature of about 1150° C. During this heating step, iron, copper, graphite, etc. are diffused and sintered, resulting in an alloy with sufficient mechanical strength.

After heating and sintering, the product may be slowly cooled and used as a product, or it may be used after its dimensions are partially corrected by machining.

In the manufacturing method of such general iron-based sintered alloys,
When press-molding metal powder using a mold, it is necessary to provide lubrication between the mold and the molded body in order to prevent galling between the mold and the molded body and to easily extract the molded body from the mold.

Conventionally known such lubrication methods include a lubricant mixing method in which a lubricant such as stearin or zinc oxide is mixed into metal powder in advance, and a mold lubrication method in which a lubricant is applied to a mold.

The former lubricant mixing method has the advantage of being able to distribute the lubricant to a certain extent, but since the lubricant is contained in the metal powder, it is Contains defects that deteriorate the physical strength.

In addition, such lubricants have a negative effect on the diffusion phenomenon during sintering, resulting in a decrease in product strength. Therefore, in general sintering furnaces, a preheating zone is provided before the heating zone, and the lubricant is introduced into the gas in the preheating zone. I'm trying to remove it by changing it.

This not only increases the number of manufacturing steps by one step and reduces productivity, but in order to obtain sintered products with stable quality, the sintering furnace must be carefully designed to prevent the lubricant gasified in the preheating zone from entering the heating zone. It becomes necessary to control the flow and flow rate of the atmospheric gas.

Recently, in order to obtain a sintered product with higher strength, a powder forging method is being developed in which a powder compact is heated and sintered and then forged. There is a movement to implement this by heating and speed up the heating cycle.

In this case, if a lubricant is mixed in the powder compact, the rapid evaporation of the lubricant due to rapid heating may cause cracks in the powder compact, and the generated lubricant gas will further disturb the heating atmosphere. Therefore, the current situation is that if a lubricant is mixed into the powder compact, it is practically impossible to heat it.

Also, according to the latter mold lubrication method, since the powder compact does not contain lubricant, the disadvantages and problems of the lubricant mixing method described above do not occur, but it is necessary to apply liquid lubricant to the mold. It is difficult to apply the lubricant to the mold, and if the lubricant is sprayed onto the mold, the lubricant will scatter around the mold, polluting the working environment and being harmful to the human body. As a result, productivity is significantly reduced, and it is hardly ever put into practical use.

In addition to the above-mentioned mold forming method, the moldability of metal powder can be improved by filling metal powder into a mold that can be deformed like rubber.
There is a method of isostatically pressurizing metal powder by applying hydraulic pressure or air pressure to the entire mold.This method eliminates the need for lubricants such as zinc stearate at all, or does not require a mold made of rubber or other materials. The dimensional accuracy is poor due to the use of molds, and since pressure must be applied to the metal body after filling a mold made of rubber or the like and sealing it, productivity is poor and it is not suitable for mass production.

By the way, seizure or galling of the molding die is particularly caused by a die that is movable in the direction of the movement axis of the pressure punch and is pressed in a direction opposite to the direction of pressure applied by the pressure punch, which is generally called a lower punch. According to so-called floating molding molds in which only the bottom element of the die hole is fixedly arranged, and two-bottom molds in which the die is moved in the pressing direction at the same time as pressure is applied, no lubricant is used. It has been found that both of them hardly occur during the pressure molding process, but occur during the molded product extraction process after pressure molding.

The present invention provides an improved powder molding method that avoids seizure or galling of the mold and the powder molded product when the powder molded product is extracted from the mold without using a lubricant, and can perform good powder molding. The purpose of this invention is to provide a mold for powder molding.

According to the present invention, in a powder molding mold for molding metal powder, etc., a die having a die hole and a bottom surface inserted into the die hole and located in the middle of the die hole are provided. a divided die element, the die being divided into at least two parts along a dividing plane passing through the die hole, and a pressurizing punch inserted into the die hole opposite to the bottom element; the split die elements are movable toward and away from each other in a direction substantially perpendicular to the axis of movement of the pressure punch, and the bottom element is configured to move toward and away from each other in a direction substantially perpendicular to the axis of movement of the pressure punch, and This is achieved by a powder molding mold characterized in that it is configured to be movable relative to the powder molding mold.

According to this configuration, in the pressure forming process, the split die elements are brought into contact with each other to create a so-called mold clamping state, and in the molded body extraction process, the split die elements are substantially moved in the axial direction of the pressure punch. By moving it in the right angle direction and separating it from the molded object, the molded object can be extracted without sliding against the die.

As a result, the molded body can be extracted from the mold without using a lubricant without causing seizure or galling of the mold.

Since there is no need to mix a lubricant into powder such as metal, it is possible to increase the strength of the compact sintered body, and in particular, the increased strength of the compact makes it difficult to crack, making it easier to handle. Automation of transportation becomes possible.

In addition, the delubrication process is no longer necessary, improving productivity, stabilizing the atmosphere inside the sintering furnace, and reducing variations in product quality.In the production of powder forged parts, high-frequency induction heating can be used for sintering heating. I can do it.

Also, since the molded body and die do not slide when the molded product is extracted,
No large force is applied to the molded object when the product is extracted.
Cracks are less likely to occur, and the clearance between the pressurizing punch and the die hole during ejection of the molded product is increased, so mold galling is reduced and mold life is greatly improved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

1 to 4 are process diagrams schematically showing the process of molding a cylindrical molded body using the powder molding die according to the present invention.

In FIG. 1, 1 is a die, and the die 1 is composed of two substantially semi-cylindrical split material elements la and ib.

Recesses 2a and 2b having a semicircular cross section are formed along the central axis of each of the split die elements 1a and 1b, and the die elements 1a and 1b have recesses 2a and 2b formed along their central axes. When the comrades are joined to each other, the recess 2a
, 2b form a die hole 2 with a circular cross section that passes vertically through the center.

That is, the die 1 is composed of two divided die elements 1a and 1b divided along a dividing plane (diameter plane) passing through the center of a die hole 2 having a circular cross section.

Above the die 1, there is a pressure punch 3 having a cylindrical shape with a circular cross section corresponding to the die hole 2, and the pressure punch 3 is fixed to a ram of a molding machine (not shown), and It is designed to move up and down along the

A cylindrical bottom element 4, generally referred to as a lower punch, is inserted into the die hole 2 from its lower opening, and the upper surface of the bottom element 4 corresponds to the substantial bottom surface of the die hole 2. It consists of

In this embodiment, the bottom element 4 is fixed to the upper surface of the mold base 5, and each of the divided die elements 1a and 1b is arranged in the direction of the movement axis of the pressure punch 3 (in the axial direction of the die). It is movable and is pressed by compression coil springs 6, 6 in a direction (upward direction in the figure) opposite to the pressing direction (downward direction in the figure) by the pressurizing punch 3.
As shown in FIG. 1, the compression coil is maintained at a predetermined height position by the action of the spring 6 so that the bottom element 4 is inserted into the lower part of the die hole 2 by a predetermined amount.

Further, each of the divided material elements 1a, 1b is arranged in a direction substantially perpendicular to the axis of movement of the pressurizing punch 3, that is, in a direction perpendicular to the diametrical plane in the figure, in order to move away from each other. It is constructed so that it can be moved horizontally.

When molding metal powder using the powder molding mold configured as described above, the molding is performed in the order described below.

First of all, as shown in FIG.
A predetermined amount of metal powder is filled into the cavity defined by the and bottom element 4.

Next, as shown in FIG. 1 and 2, the pressure punch 3 is lowered to press the metal powder filled in the cavity to form a cylindrical molded body W in the gouging hole 2 under pressure.

During this pressure forming, the die 1 descends against the action of the compression coil spring 6 as the pressure punch descends due to friction with the metal powder, minimizing slippage between the die hole and the metal powder. Keep it to.

When the pressure forming is completed, the pressure punch 3 is stopped at that position, and then the left divided die element 1a is moved to the left in the figure, and the right divided die element i1b is moved to the left as shown in FIG. are moved substantially horizontally to the right in the figure, and the mold surface of the die hole 2 is separated from the pressure punch 3, the bottom element 4, and the molded body W.

That is, the die 1 is separated.

When the separation of the dies 2 is completed, the pressurizing punch 3 is raised and returned to its original position as shown in FIG. Compression coil spring 6 to a height that corresponds to the top surface of
lowering against the action of

Then, in this state, the molded body W placed on the upper surface of the bottom element 4 is taken out.

Therefore, the molded body W is extracted without sliding with respect to the die 1.

Incidentally, the lifting operation of the pressurizing punch 3 is performed by the split die elements 1a and 1.
This may be performed before separating b.

Figs. 2 1-46 are somewhat exploded process diagrams illustrating the molding process when powder molding a connecting rod for an internal combustion engine using the powder molding mold according to the present invention.

In FIG. 2, 11 is a first divided die element, and this divided die element 11 constitutes a part of a die hole 18 forming a connecting rod shape to be formed, and the second and third divided die elements. It is provided with a relatively large space 14 for storing 12 and 13.

The second and thirtieth die elements 12, 13 have die hole forming recesses 12', 13' formed corresponding to the shape of the end face of the connecting rod to be formed on opposite sides thereof,
The connecting rods are arranged to be horizontally movable within the space 14 in a direction perpendicular to the longitudinal axis of the connecting rod so as to move toward and away from each other.

Further, above these divided die elements, a pressurizing punch 15 corresponding to the connecting rod-shaped die hole formed by these divided die elements is arranged so as to be movable up and down.

In this case, the pressurizing punch 15 is provided with a protrusion 15' having a predetermined shape on its lower surface in order to form one surface of the rib portion of the connecting rod.

The space 14 of the first split die element 11 and the die hole configuration recesses 12', 1 of the second and third split die elements 12, 13.
A bottom element 16 is inserted into the die hole 12 defined by 3' from its lower opening edge to a predetermined depth.

This bottom element 16 corresponds to the protrusion 15' of the pressure punch 15.
It includes a rib-forming bottom element 17 that corresponds to and molds the other side of the rib portion of the connecting rod.

The bottom element 16 is fixed to a mold base (not shown), or the rib forming bottom member 17 is movable up and down with respect to the bottom element 16, and is normally positioned sufficiently above the bottom element 16 as shown in FIG. It is in a state of prominence.

Also, -1 second and third split die elements 11, 12, 13
are movable in the movement axis direction of the pressurizing punch 15, and are flexibly biased upward in the figure by elements such as a compression coil spring (not shown). As shown in FIG. 1, it is maintained at a predetermined height position relative to the fixed bottom element 16.

Next, the molding process will be described in the case where a connecting rod for an internal combustion engine is powder molded using the powder molding mold configured as described above.

First, as shown in FIG. 2, the second and third split die elements 12 and 13 are joined together and molded together, and then the space 14 and the die hole-crossing recesses 12' and 13' work together to form a die. A predetermined amount of metal powder is filled into the cavity defined by the die hole 18, the bottom element 16, and the rib-forming bottom element 17.

Next, as shown in FIG. 2, by lowering the pressurizing punch 15, the metal powder filled in the cavity is pressurized, and a molded body W' having a connecting rod shape is placed in the die hole 18.
to form.

During this pressure molding, the first, second and third divided die elements l
L12 and 13 are pressurized punches 15 due to friction with metal powder.
It descends with the descent of.

At this time, the rib forming bottom element 17 also descends to a predetermined height as the pressure punch 15 descends.

Once the compact W' is formed as described above, the second and third split die elements 12 and 13 are separated from each other as shown in FIG. 2 with the pressurizing punch 15 stopped at that position. Move horizontally in the direction.

Then, raise the pressure punch 15 to its original position,
As shown in FIG. 2, the molded body W' is taken out with the first, second and third divided die elements 1L12, 13 and the rib forming bottom element 17 lowered to their respective predetermined positions.

Therefore, at this time as well, the molded body W' can be pulled out without substantially slipping against the mold surface of the die hole 18.

Incidentally, the lifting operation of the pressure punch 15 may be performed before the second and third Φ-split die elements 12.13 are separated from each other.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to such embodiments, and various embodiments and modifications can be made within the scope of the present invention. This will be clear to those skilled in the art.

[Brief explanation of the drawing]

1 to 4 are process diagrams schematically showing the molding process when powder molding a cylindrical compact using the powder molding mold according to the present invention, and FIGS. 2 1 to 4 are according to the present invention. FIG. 3 is a somewhat exploded process diagram illustrating a molding process when powder molding a connecting rod for an internal combustion engine using a powder molding mold. 1...Die, 1a, 1b...Divided die element, 2...Die hole, 2a, 2b...
Recessed portion, 3... Pressure punch, 4... Bottom element, 5... Type board, 6... Compression coil spring, 11...・First split die element, 12
...Second split die element, 12'...
Recess for configuring die hole, 13...Third split die element, 13'... Recess for intercepting die hole, 14...
... Space, 15 ... Pressure punch, 16 ...
... Bottom element, 17 ... Bottom element for rib forming, 18 ... Die hole.

Claims (1)

[Scope of Claims] 1. A die with a die hole, a bottom element that is fitted into the die hole along its longitudinal axis and constitutes a bottom surface located in the middle of the die hole, and a bottom element that is fitted into the die hole along its longitudinal axis and constitutes a bottom surface located in the middle of the die hole. a pressure punch fitted opposite the bottom element along the
In a powder molding mold for compressing metal powder, etc. loaded therebetween by bringing the bottom element and the pressurizing punch close to each other in the die hole, the die is placed in the die hole. It is constituted by a split die element divided into at least two parts along a splitting plane passing in a direction along the longitudinal axis, and the splitting die element is joined to each other at the splitting plane to provide the die hole and the closed position. the dividing planes are movable in a direction substantially perpendicular to the longitudinal axis of the die hole between an open position in which the parting surfaces are separated from each other and the die hole is enlarged and open, and the bottom surface of the bottom element exits the die hole; A powder molding mold, characterized in that it is configured to be movable relative to the bottom element in a direction along the longitudinal axis of the die hole to a position. 2. In the powder molding mold according to claim 1, the die is flexibly supported so that the bottom surface of the bottom element is located halfway in the die hole. Mold for powder molding.