JPH03177503A - Production of starting material for injection-molding metal powder - Google Patents

Abstract

PURPOSE:To uniformly disperse metal powder, to prevent the aggregation of the powder, to improve flowability at the time of injection molding and to stabilize the quality of metal parts after sintering by mixing the metal powder with a binder under irradiation with ultrasonic waves to prepare starting material for molding. CONSTITUTION:A blend of metal powder with a binder consisting of a bonding agent, a lubricant and a plasticizer is mixed. At this time, the metal powder is first mixed with the plasticizer under irradiation with ultrasonic waves until the powder is uniformly dispersed in the liq. The remaining binder components melted by heating are then added and they are kneaded. This kneaded mixture is used as starting material for injection molding, injection-molded freed of the binder and sintered to produce metal parts.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention is directed to the production of metal parts by injection molding using a blended mixture obtained by heating and kneading metal powder and a binder, followed by removal of the binder and sintering. The present invention relates to a method for producing a raw material for metal powder injection molding in a method.

[Prior art] A conventional method for manufacturing metal powder injection molding raw materials (hereinafter referred to as metal injection raw materials) consisting of metal powder and a binder is described in the magazine "
Metal” (Agne Publishing) Vo159, No. 5. As shown in the special feature "Metal Injection Molding," the binder was plasticized by heating in a kneader, then metal powder was added and kneaded for about 30 minutes to one hour.

However, with conventional technology, since the metal powder is in a dry state before kneading, it is impossible to avoid agglomeration of the metal powder particles and the presence of air at the interfaces and between the metal powder particles. When the metal injection raw material 4 is poured into a plasticized binder, agglomerates of metal powder and air will be present in the metal injection material 4, resulting in non-uniform fluidity during injection molding, resulting in an injection molded product (hereinafter referred to as It was not possible to obtain precision metal parts because the dimensions of the sintered metal parts (referred to as "green") varied, the shape collapsed when the binder was removed, and the dimensions after sintering varied. In particular, when reducing the particle size of metal powder to achieve dimensional accuracy, it is impossible to reduce dimensional variation during mass production by simply changing the conditions of the injection molding method, binder removal method, and sintering method. there were.

In addition, in order to avoid metal powder layer agglomerates and air in the metal injection raw material, if the kneading time is increased or the driving torque is increased during cross-wiring, the polymer in the binder will thermally deteriorate and the strength of the green will decrease. This makes it unsuitable for mass production because it breaks during handling between processes.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems. By using a metal injection raw material in which metal powder and binder are uniformly dispersed, dimensional accuracy is excellent and quality is stable. Our goal is to provide quality metal parts.

[Means for Solving the Problems] The method for producing a raw material for metal powder injection molding of the present invention uses a mixture of a metal powder and a binder comprising at least a binder, a lubricant, and a plasticizer as a raw material for injection molding, and after injection molding, In the method for manufacturing metal parts by removing the binder and sintering, the metal powder is mixed with a plasticizer that is at least a part of the binder while irradiated with ultrasonic waves, and after the metal powder is uniformly dispersed in the liquid. , is characterized in that it is added to the remaining binder that has been heated and melted and kneaded.

Binders are usually polymer-based binders to maintain the green's shape retention and strength, lubricants such as paraffin to improve slippage in the mold during injection molding, and lubricants to improve fluidity during injection molding. It consists of plasticizers such as phthalate esters. Further, the binder and lubricant are solid, and the plasticizer is liquid. A plasticizer, which is part of the binder, is used as a solvent to disperse metal powder into a liquid, but depending on the particle size and material of the metal powder, the amount of plasticizer may be insufficient to disperse the metal powder. In this case, add the required amount of an organic solvent such as ethanol or ether, which has a boiling point lower than that of the plasticizer, uniformly disperse the metal powder in the solvent while irradiating it with ultrasound, and then heat it to dissolve the ethanol, ether, etc. This can be done by volatilizing and removing the organic solvent, adding it to the heated and melted binder, and kneading it.

Furthermore, if foaming occurs when dispersing the metal powder in a solvent, uniform dispersion can be quickly achieved by performing the process in a reduced pressure atmosphere.

[Example 1 As metal powder, average particle size is 9 μm, maximum particle size is 18Lz
JIS-3US316 stainless steel powder (hereinafter referred to as 5US316 powder), dibutyl phthalate as a plasticizer, paraffin as a lubricant, and polyethylene as a lubricant were prepared in the composition amounts shown in Table 1. did.

The volume ratio of 5US316 powder to dibutyl phthalate is approximately 4.
．． Since the amount of 1 and solvent is insufficient, add ether to make 5U.
So that the volume ratio of S316 powder and solvent is 3 l,
After dissolving dibutyl phthalate and ether in a mixer,
While irradiating the skin with ultrasonic waves, add SUS 316 powder and mix for 30 minutes.

In Table 1, the frequencies of ultrasonic waves are 28kHz, 45kHz, 10kHz.
Irradiation was performed by sequentially switching three frequencies of 0 kHz to avoid the formation of standing waves.

Next, in order to remove ether from the solvent in which the 5US316 powder was uniformly dispersed, it was heated at 80°C in a reduced pressure atmosphere of 10 mmHg.
A slurry in which 5LIS316 powder was uniformly dispersed in dibutyl phthalate was obtained.

This slurry was put into a mixed wire (paraffin and polyethylene partially melted at 150°C) and kneaded for 1 hour to obtain a raw material for metal injection.

As a comparative example of the present invention, 5US316 powder was added to dibutyl phthalate, paraffin, and polyethylene that had been heated and melted at 150°C in a kneading machine, and the mixture was mixed for one hour. A metal injection raw material was obtained.

The flow value Q, which represents fluidity, of the thus obtained metal injection raw material according to the present invention and the metal injection raw material of the comparative example was measured at 150°C using a flow tester.
I2/sec, whereas in the comparative example, 3.3x l
0'' mff/sec, which shows that the production method of the present invention significantly improves fluidity.

Next, using these metal injection raw materials, φ20-5'
(mm) of each green under the conditions shown in Table 2.
I created 0 each.

Table 2 As shown in Table 2, the injection conditions are different because the fluidity of the metal injection raw material is different.The metal injection raw material according to the present invention has excellent fluidity, so the injection temperature is lowered, and the injection condition is different. It can be said to be suitable for mass production because the pressure can be reduced and it can support a wide range of injection conditions.

The thus obtained green was heated to 600° C. in a nitrogen gas atmosphere to remove the binder, and then heated to 1350° C. in a vacuum atmosphere to obtain a disk-shaped metal part.

Average shrinkage rate of metal parts by each metal injection raw material,
Table 3 shows the variation in shrinkage rate, average theoretical density ratio, and diameter size variation.

Table 3 As is clear from Table 3, by using the raw material for metal powder injection molding produced by the manufacturing method of the present invention, metal parts with high sintered density and excellent dimensional accuracy can be obtained.

[Effect of the invention 1 As described above, by uniformly dispersing the metal powder in the raw material for metal powder injection molding and preventing powder agglomeration, fluidity during injection molding is improved and binder removal is stabilized. The quality of metal parts after sintering is stable,
It is possible to obtain dimensional accuracy that allows use as a metal part without processing after sintering.

In addition, difficult-to-process materials such as 5US316 can be used as metal parts after sintering, which would result in a significant increase in cost.6, and the advantage of being able to obtain complex and precise metal parts that could not be machined in the past. have

that's all

Claims (1)

[Claims] A method for manufacturing metal parts in which a mixture of a binder and metal powder, which includes at least a binder, a lubricant, and a plasticizer, is used as a raw material for injection molding, and after injection molding, the binder is removed, and the metal parts are sintered. A raw material for metal injection molding, which is characterized in that the powder and a plasticizer, which is at least a part of the binder, are mixed, the metal powder is uniformly dispersed in a liquid, and then the mixture is added to the remaining binder that has been heated and melted and kneaded. Production method.