JP2000063913A - Production of metallic sintered product having two or more parts composed of different kinds of material and metallic sintered product obtained thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high hardness part without requiring quenching and to obtain a low hardness part in which, even in the case deformation is generated at the time of sintering, the modification thereof is easy, and, post-working by cutting or the like is also easy at the time of producing a product having two or more parts by a metal injection molding method. SOLUTION: By using a primary molding material composing a primary part 2 and contg. metallic material powder and a binder contg. a thermoplastic resin and a secondary molding material composing a secondary part 4 and contg. secondary metallic material powder and a binder contg. a thermoplastic resin, respectively, a molding primary part 2a and a molding secondary part 4a are subjected to injection molding to obtain a green molding in accordance with a metallic sintered product. This green molding is subjected to heating treatment under the reduced pressure, the binder is removed from the green molding, and the primary metallic material powder and the secondary metallic material powder are sintered to form a primary part having 80 to 250 Hmv hardness and a secondary part having >=600 Hmv hardness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the field of technology for manufacturing a metal-sintered product, and more particularly to the manufacture of a metal-sintered product having a plurality of parts made of different materials using metal injection molding. is there.

[0002]

2. Description of the Related Art Sintered metal products have been used in a wide range of fields in recent years because of their advantages in mass productivity. As an example thereof, an actuator finger for a circular knitting machine is exemplified.

In a circular knitting machine, an actuator finger is appropriately brought into contact with a knitting needle in a needle selection mechanism section to control a moving path of the knitting needle, whereby a desired pattern can be formed on a knitted fabric to be braided. it can. Such control of the movement path of the knitting needle causes each of a large number of actuator fingers to engage with the action portion of the actuator,
This is done by controlling the actuator in a desired manner by an electronic computer.

The actuator finger is adapted to the tip (acting portion) of an actuator using a piezoelectric element that operates by receiving an electric signal under the control of an electronic computer, and has a first portion that receives a driving force from the acting portion and the first portion. The second portion is fixed to the first portion and appropriately contacts the knitting needle to control the traveling movement route thereof.

As a method of manufacturing such an actuator finger, a molding material obtained by mixing metal powder with a binder containing a thermoplastic is molded by an injection molding machine to obtain a desired shape corresponding to a molding die. It is possible to use a metal injection molding method (MIM method) in which a green molded body is produced, and then the binder molded plastic is burned or sublimated by heating the green molded body to sinter the metal powders in the green molded body. it can. According to this, it is possible to obtain a product (actuator finger) made of a metal sintered body having a shape similar to that of the green molded body, although the dimension of the green molded body is shrunk. This method has an advantage that a large amount of products can be manufactured in a short time as compared with a method of machining a bulk metal material by cutting or the like to obtain a desired shape.

By the way, since the actuator engaging portion of the first portion which engages with the actuator needs to accurately follow the minute displacement of the acting portion of the actuator, extremely high dimensional accuracy is required. Not so high hardness is required. On the other hand, the head portion (knitting needle contact portion) of the second portion that comes into contact with the knitting needle is required to have high hardness in order to reduce wear due to frequent rubbing (contact) of the knitting needle and to prolong life. To be done.

As described above, when forming a product having a plurality of parts having different requirements for hardness and other properties with a metal sintered body, if there is a metal material that satisfies all the properties required for each part, It is preferably used for all parts (ie the entire product is made of the same material).
However, in reality, such a thing is often difficult.

In the case of the actuator finger, for example, the high hardness required for the head of the second portion can be realized by carburizing and quenching the sintered body. However, when the entire product is formed using such a material and the entire product is made to have a high hardness by hardening, if the first portion is deformed during the carburizing and quenching, the correction is required. It has the disadvantage of becoming extremely difficult.

Further, the addition of the carburizing and quenching step has a disadvantage that the manufacturing step is complicated and the number of steps is increased, resulting in an increase in cost.

Therefore, according to the present invention, a high hardness portion can be obtained without a quenching step when manufacturing a product having a plurality of portions having different required characteristics with respect to hardness by using a metal injection molding method. On the other hand, a metal sintered product having a plurality of parts, which can be easily corrected in a portion requiring low hardness even when deformed during sintering and can be easily post-processed by cutting etc. It aims at providing the manufacturing method of.

A further object of the present invention is to provide a metal-sintered product having a high hardness portion and a low hardness portion which is easy to correct deformation and to be post-processed.

[0012]

According to the present invention, in order to achieve the above object, there is provided a method for producing a sintered metal product comprising a plurality of parts, wherein each of the plurality of parts is a powder of a metal material. A green molded body is obtained by forming a corresponding molded body part by injection molding using a molding material containing a binder containing a thermoplastic resin.
By subjecting the green molded body to heat treatment under reduced pressure to remove the binder from the green molded body and sinter the metal material powder, different hardnesses can be obtained by using different metal materials for each of the plurality of portions. A method for producing a metal-sintered product having a plurality of parts made of different kinds of materials is provided, which comprises obtaining the metal-sintered product having the plurality of parts.

In one aspect of the present invention, the binder content in each molding material of the plurality of parts is
The shrinkage rates of the molded body portions corresponding to the respective plurality of portions due to the heat treatment are set to be equal.

In an aspect of the present invention, the plurality of portions have a hardness Hmv of 80 to 250 and a hardness Hm of the first portion.
and a second part in which v is 600 or more.

In one aspect of the present invention, the melting point of the metal material of the first portion is higher than the melting point of the metal material of the second portion.

In one aspect of the present invention, the binder content in the molding material of the first portion is higher than the binder content in the molding material of the second portion.

In one aspect of the present invention, the metal material of the first portion has a carbon content of 0.2% or less, and the metal material of the second portion has a carbon content of 0.5% or more. .

In one aspect of the present invention, the metal material of the first portion is stainless steel or Fe-2 to 8% Ni.
And the metal material of the second part is alloy tool steel, carbon tool steel or high speed steel.

According to the present invention, in order to achieve the above object, there is provided a metal sintered product having at least a first portion and a second portion, the first portion having a corrected shape and size. Alternatively, it is made of a sintered body of a first metal material having a low hardness to facilitate post-processing, and the second portion has a hardness Hm.
A sintered metal product, characterized in that it is composed of a sintered body of a second metal material having a high hardness v of 600 or more.

In one aspect of the present invention, the first portion is made of a sintered body of a first metallic material having a hardness Hmv of 80 to 250.

In one aspect of the present invention, the metal material of the first portion has a carbon content of 0.2% or less, and the metal material of the second portion has a carbon content of 0.5% or more. .

In one aspect of the present invention, the metal material of the first portion is stainless steel or Fe-2 to 8% Ni.
And the metal material of the second part is alloy tool steel, carbon tool steel or high speed steel.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic process explanatory view showing an embodiment of a method for producing a metal sintered product having a plurality of parts according to the present invention. In this embodiment, an actuator finger for a circular knitting machine is used as the metal sintered product. 2 is a side view showing the actuator finger for the circular knitting machine, and FIG. 3 is a sectional view taken along the line XX '.

2 to 3, reference numeral 2 indicates a first portion, and reference numeral 4 indicates a second portion. As shown in FIGS. 2 and 3, the first portion 2 has a U-shaped cross-section that is open downward and extends along a direction orthogonal to the XX ′ direction (vertical direction). Groove (groove width is, for example, 2.0
mm) 22 and 1 to form the groove 22
A pair of legs 24 are formed. The second portion 4 is the groove 2
2 and a base portion 44 having a substantially rectangular through hole 42 (minimum inner diameter is 1.7 mm, for example) formed in parallel,
6 and a head portion 48 supported by the neck portion. Code 6
Indicates a joint surface between the first portion 2 and the second portion 4.

The first portion 2 is made of a sintered body of a first metallic material having a hardness Hmv of 600 or more, and the second portion 4 is made of a sintered body of a second metallic material having a hardness Hmv of 80 to 250. The first metal material is, for example, stainless steel having a carbon content of 0.2% or less (SUS316L, SUS304L, etc.)
Alternatively, Fe-2 to 8% Ni, and the second metal material is, for example, an alloy tool steel (SKD11) having a carbon content of 0.5% or more.
Etc.), carbon tool steel (SK3 etc.) or high speed steel (S
KH3 etc.).

FIG. 4 is a sectional view showing a usage state of the actuator fingers of this embodiment. A pin 10 having a circular cross section that functions as a rotation center support shaft is provided in the through hole 42.
Has penetrated. The pin 10 is arranged in the needle selection mechanism of the circular knitting machine, and is fitted with the minimum inner diameter of the through hole 42 and a minute clearance. Therefore, the actuator finger can rotate around the pin 10 as a center. On the other hand, the upper end (action portion) of the piezoelectric element actuator 12 is inserted into the groove 22 from below with a minute clearance. The actuator 12
Has a lower end fixed to the needle selection mechanism of the circular knitting machine, and is operated by receiving a required electric signal in association with a number of other actuator fingers under the control of the electronic computer. As a result, the upper end of the actuator 12 can be displaced in the left-right direction in FIG. 4 as shown by the arrow. Along with this, the leg portion 24 which is fitted so as to sandwich the actuator acting portion receives a driving force, the actuator fingers rotate around the pin 10, and the head 48 in FIG. It can be displaced left and right. The displacement of this head 48 is
Since the distance from 2 is larger than the distance from the pin to the actuator acting portion, it corresponds to an enlarged displacement of the actuator acting portion. The maximum displacement of the head 48 is 0.5 mm on one side and about 1 mm on both sides.

The knitting needle of a circular knitting machine (not shown) can come into contact with the head 48 during its movement, and the movement path after contact and separation is controlled according to the magnitude of the displacement of the head. It The foot portion 24 constitutes an actuator engaging portion, and the head portion 48 constitutes a knitting needle contact portion.

The actuator finger as described above is manufactured as follows, as shown in FIG.

First, a first molding material containing a first metallic material for the first part 2 is obtained. The first molding material is, for example, a mixture of SUS316L powder, polyethylene as a binder, paraffin wax, and stearic acid. The amount of binder added is, for example, 45
The capacity is%.

Apart from this, the second for the second part 4
A second molding material containing the metallic material of is obtained. The second molding material is, for example, a mixture of SKD11 powder, polyethylene as a binder, paraffin wax, and stearic acid. The amount of binder added is 4
It is 3% by volume.

The first molding material and the second molding material are applied to a two-color molding machine, and first, as shown in FIG. 1 (a), a molded body second portion 4a corresponding to the second portion 4 is formed. The second portion 4a of the molded body is formed by injection molding the second molding material into the cavity for the. Then, as shown in FIG. 1B, the movable mold member of the mold device is moved to form a cavity for the first portion 2a of the molded body corresponding to the first portion 2, and The first portion 2a of the molded body is formed by injection molding the first molding material. Thereby, as shown in FIG. 1B, a green molded body including the molded body first portion 2a and the molded body second portion 4a is obtained. In the steps of FIGS. 1A to 1B, the mold device is moved from the position corresponding to the injection port of the second molding material to the position corresponding to the injection port of the first molding material in the two-color molding machine. It is continuously performed with the step of moving.

By subjecting the green compact thus obtained to heat treatment, the binder is removed from the green compact and the metal powder is sintered as shown in FIG. Obtain the actuator fingers as shown in 2-3. This heat treatment can be performed in a reduced pressure heating furnace, for example, according to a temperature curve as shown in FIG.

That is, first, the temperature is raised from room temperature to 100 ° C. in 30 minutes from time 0 to T ₁ , and this temperature is changed to time T 1.
_Hold from ₁ to T ₂ for 4 hours. During this period, the paraffin wax is scattered from the molded body, and the pressure in the heating furnace is reduced to about 10 ⁻⁵ Torr in order to accelerate its removal to the outside of the system.

Next, from time T ₂ to T ₃ , 0.5 ° C./m
The temperature is raised to 400 ° C. with a temperature gradient of in, and this temperature is maintained from time T ₃ to T ₄ for 1 hour.

Next, from time T ₄ to T ₅ , 1 ° C./min
The temperature gradient is raised to 500 ° C., and this temperature is set to time T
Hold for 2 hours from ₅ to T ₆ .

By the above, the binder burns.

Next, from time T ₆ to T ₇ , 10 ° C./mi
The temperature is raised to 1100 ° C. with a temperature gradient of n, and this temperature is maintained for 1 hour from time T ₇ to T ₈ .

Next, from time T ₈ to T ₉ , 10 ° C./mi
The temperature is raised to 1230 ° C. with a temperature gradient of n, and this temperature is maintained for 4 hours from time T ₉ to time T ₁₀ .

As a result, the metal powders are sintered together.

Next, in the heating furnace, it is rapidly cooled to room temperature from time T ₁₀ to T ₁₁ over 4 hours.

From time T ₂ to T ₁₁ , the inside of the heating furnace is depressurized to about 10 Torr by introducing nitrogen gas.

According to the steps of the embodiment of the present invention as described above, in the first molding material containing the first metal material having a relatively high melting point of about 1400 ° C., the binder content is relatively 45% by volume. In the second molding material containing the second metal material, which has a relatively high melting point and a relatively low melting point of about 1240 ° C., the binder content is relatively low at 43% by volume, so that the sintering heat treatment at the peak temperature of 1230 ° C. The shrinkage rate of the molded body first portion 2a and the shrinkage rate of the molded body second portion 4a become equal, and the residual stress in the vicinity of the joint surface 6 between the first portion 2 and the second portion 4 is sufficiently reduced. can do.

The binder content in the molding material can be set in the following manner in consideration of such shrinkage. That is, first, a suitable binder content rate is set for the second molding material containing the second metal material having a relatively low melting point. The peak temperature of the heat treatment during sintering (sintering peak temperature) is preferably set near the melting point of the second metal material (a temperature slightly lower than the melting point). In addition, generally, if the binder content is too low, the smoothness of the flow of the molding material in the molding machine is reduced, and if the binder content is too high, the shape change due to the removal of the binder in the heat treatment becomes large and the shape retention is lowered It's easy to do. Considering these points, the sintering peak temperature is 1 when the second metal material is SKD11.
It is preferable to set the binder content in the second molding material to 43 [± 0.5]% by volume (Vol%) at 230 [± 5] ° C. The shrinkage rate of the second molding material due to sintering in this case is about 18%.

On the other hand, with respect to the first molding material, the change in shrinkage rate when the sintering peak temperature is changed is examined. First
When the metal material of No. 1 is SUS316L, the change of the shrinkage rate of the first molding material with respect to the change of the sintering peak temperature is as shown in FIG. 6 with the binder content in the first molding material as a parameter. . From this figure, at a sintering peak temperature of 1230 ° C., in order to make the shrinkage rate of the first molding material 18%, which is equivalent to the shrinkage rate of the second molding material,
The binder content in the first molding material is approximately 45% by volume.
You can see that

In the heat treatment, from time T ₆ to T
By rapidly heating up to ₇ , the occurrence of non-uniform heat distribution during sintering is suppressed as much as possible to realize uniform shrinkage (shrinkage rate of about 18%), and abnormal deformation can be prevented.

The effect of preventing such deformation is obtained by the second step (ie, the time of sintering) of the metal material powder after the completion of the first step of the binder removal (ie, from time 0 to time T ₆ ). It is obtained by increasing the temperature at a rate of 8 ° C./min or more from T ₆ to time T ₁₁ .

This effect is particularly exerted at a temperature of 800 to 1050 ° C.
(Including time T in FIG. 5) ₆ From time T₇ Until
Within the range) is effective. this
Shows that the shrinkage of the molded body occurs most severely within this temperature range.
Therefore, perform rapid heating within this range to reduce the heat generated during sintering.
To suppress the occurrence of non-uniform distribution as much as possible
It is extremely effective in achieving various shrinkages and preventing abnormal deformation.
Because there is.

The first step is preferably carried out within a temperature range of 550 ° C. or lower, and the rate of temperature increase in this first step is 3 ° C./minute or lower for good debinding. Is preferred.

In the actuator finger obtained as described above, the hardness of the second portion 4 is Hmv720-720.
Since it is 830, it can be used without carburizing and quenching. (Since the second metal material forming the second portion 4 has a carbon content of 0.5% or more, the second portion 4 Is sufficiently hardened by the quenching effect in the process of cooling the furnace). Further, since it is not necessary to carry out the carburizing and quenching, there is no possibility of deformation due to the carburizing and quenching work, and the dimensional accuracy of the first portion 2 is good. Furthermore, since the heat treatment is performed under reduced pressure and under a nitrogen atmosphere, the first portion 2 has a low carbon or oxygen content and a hardness of Hmv110-1.
Since it is 40, even if correction (for example, correction of the width of the groove 22) for further improving the dimensional accuracy is performed as needed, the correction work by pressing or cutting is easy (the first portion 2 is configured. The carbon content of the first metallic material is 0.2% or less, so that the hardness of the first portion 2 is small due to the quenching effect in the process of cooling in the furnace). It should be noted that Hmv of 150 or less is preferable for correction by pressing deformation, and Hmv of 250 or less is preferable for correction by cutting.

In the above embodiment, the through hole 42 for receiving the pin 10 is provided in the second portion 4 near the joint portion with the first portion, and the first portion and the second portion are provided.
This is advantageous because the area of the joint surface 6 with the portion can be increased. However, in the present invention, an embodiment is also possible in which the joint surface between the first portion and the second portion is arranged as shown by reference numeral 8 in FIG. 2 and the through hole 42 is provided in the first portion. is there.

In the above embodiment, the circular knitting machine actuator finger is used as the metal sintered product, but in the present invention, as the metal sintered product, other tools such as a tool blade tip of a rebar thread cutting machine as shown in FIG. 7 are used. It is also possible to use. This tool blade tip has a substantially flat plate shape, and has a first portion 52 having a through hole 53 for forming a mounting screw hole for fixing with a screw to a screw cutting machine and a second portion having a screw cutting blade 55. And a portion 54. The screw cutting blade 54 is formed on the outer peripheral portion of the second portion 54, the attachment screw hole through hole 53 is formed at the center of the first portion 52, and the first portion 52 is the second portion. It is located in the center of 54.

This tool blade tip is manufactured by injection molding with a two-color molding machine, and then, the through hole 5 of the first portion 52 is formed.
3 requires a process for forming a mounting screw hole. For this reason, the first portion 52 is required to have low hardness to the extent that a mounting screw hole can be formed, while the second portion 54 having the thread cutting blade 55 is particularly high in terms of machining performance as a tool. Hardness is required. Such a request is based on the above-mentioned FIG.
Filled with a tool blade tip manufactured similarly to the embodiment described with reference to FIG.

[0054]

As described above, according to the present invention, a metal sintered product having a required high hardness portion and a low hardness portion advantageous for straightening or post-processing does not require a separate quenching step. Can be manufactured.

[Brief description of drawings]

FIG. 1 is a schematic process explanatory view showing one embodiment of a method for producing a metal sintered product having a plurality of parts according to the present invention.

FIG. 2 is a side view showing an actuator finger for a circular knitting machine manufactured by the method for manufacturing a metal sintered product having a plurality of parts according to the present invention.

FIG. 3 is a cross-sectional view taken along line X-X ′ of FIG.

FIG. 4 is a cross-sectional view showing a usage state of an actuator finger for a circular knitting machine manufactured by the method for manufacturing a metal sintered product having a plurality of parts according to the present invention.

FIG. 5 is a graph showing a temperature curve of heat treatment when manufacturing an actuator finger for a circular knitting machine manufactured by the method for manufacturing a metal sintered product having a plurality of parts according to the present invention.

FIG. 6 shows changes in shrinkage rate of the first molding material with respect to changes in the peak sintering temperature, with the binder content in the first molding material as a parameter in the method for producing a metal sintered product having a plurality of parts according to the present invention. It is a graph.

FIG. 7 is a perspective view showing a tool blade tip manufactured by the method for manufacturing a metal sintered product having a plurality of parts according to the present invention.

[Explanation of symbols]

2 First part 2a molded body first part 4 second part 4a molded body second part 6,8 Bonding surface 22 groove 24 feet (actuator engaging part) 42 through hole 44 base 46 neck 48 heads (knitting needle contact part) 52 First Part 53 Through hole for mounting screw hole formation 54 Second Part 55 screw cutting blade

Claims (12)

[Claims] 1. A method for producing a metal sintered product comprising a plurality of parts, wherein each of the plurality of parts is injection-molded using a molding material containing a powder of a metal material and a binder containing a thermoplastic resin. A green molded body is obtained by forming a corresponding molded body portion by heating the green molded body under reduced pressure to remove the binder from the green molded body and sinter the metal material powder. A metal sintered product having a plurality of portions made of different materials, characterized in that a metal sintered product made of the plurality of portions having different hardnesses is obtained by using different metal materials for each of the plurality of portions. Product manufacturing method. 2. The binder content in the molding material of each of the plurality of parts is set so that the shrinkage rates of the molded body parts corresponding to each of the plurality of parts due to the heat treatment become equal. The method for producing a metal-sintered product according to claim 1, which is characterized in that. 3. The hardness Hmv of the plurality of portions is 80 to 2
The method for producing a metal-sintered product according to any one of claims 1 and 2, which comprises a first portion 50 and a second portion having a hardness Hmv of 600 or more. 4. The method for producing a metal-sintered product according to claim 3, wherein the melting point of the metal material of the first portion is higher than the melting point of the metal material of the second portion. 5. The binder content in the molding material of the first part is higher than the binder content in the molding material of the second part.
A method for producing a metal-sintered product according to any one of 1. 6. The metal material of the first portion has a carbon content of 0.2% or less, and the metal material of the second portion has a carbon content of 0.5% or more. Claim 3
6. The method for producing a metal-sintered product according to any one of 5 to 5. 7. The metal material of the first portion is stainless steel or Fe-2 to 8% Ni, and the metal material of the second portion is alloy tool steel, carbon tool steel or high speed steel. The method for producing a metal-sintered product according to claim 6, characterized in that. 8. A sintered metal product manufactured by the method according to claim 1. 9. A metal-sintered product having at least a first portion and a second portion, wherein the first portion has a low hardness of the first portion for facilitating correction of shape and size or post-processing. It is made of a sintered body of metal material, and the second portion has a hardness of Hm.
A sintered metal product, characterized by comprising a sintered body of a second metal material having high hardness v of 600 or more. 10. The hardness Hmv of the first portion is 80 to 80.
The sintered metal product according to claim 9, which is composed of a sintered body of 250 first metal materials. 11. The first metal material has a carbon content of 0.
2% or less, and the second metal material has a carbon content of 0.
It is 5% or more, The metal-sintered product in any one of Claims 9-10 characterized by the above-mentioned. 12. The first metal material is stainless steel or Fe-2 to 8% Ni, and the second metal material is alloy tool steel, carbon tool steel or high speed steel. The metal-sintered product according to claim 11.