KR102157340B1 - Making method for control finger - Google Patents

Abstract

The present invention comprises the steps of preparing a metal powder and a binder as raw materials for manufacturing a control finger; Kneading the metal powder and the binder; Injection molding the kneaded raw material in a control finger forming mold; Degreasing the binder of the formed body in a nitric acid atmosphere; Sintering the degreased green body; And post-treating the formed sintered body. It provides a method of manufacturing a control finger using metal powder injection molding comprising a.
According to the present invention, after the control finger is manufactured, it is possible to have a final shape for obtaining the final shape without an additional processing process, and the binder can be removed within a short time after the control finger is formed.

Description

Control finger manufacturing method {Making method for control finger}

The present invention relates to a method for manufacturing a control finger, and more particularly, to a method for manufacturing a control finger in which the number of processing steps is reduced and a binder removal operation can be performed more quickly.

In general, a transmission of a vehicle is a device that is installed between a clutch and a propulsion shaft to appropriately shift and transmit a driving force of an engine according to a change in a driving state of the vehicle.

The transmission of the vehicle includes an automatic transmission that automatically shifts according to a driving situation of the vehicle, and a manual transmission that shifts the shift by a driver's operation.

A manual transmission generally includes a control mechanism for shifting a gear stage and a synchro mesh mechanism interlocked with the control mechanism.

Here, a control finger is mounted to operate the shift lug connected to the synchro mesh mechanism.

Since the control finger has to be used for a long time under severe conditions, excellent durability and precision such as strength and wear resistance are required.

To this end, conventionally, it is manufactured using a casting method using nodular cast iron, but due to the elaborate shape of the control finger itself, additional processing to obtain the final shape is required after casting, and the additional processing increases the cost of the process. And it is necessary to solve this problem because the manufacturing cost of the control finger is increased due to additional material loss.

The use of a powder injection molding process has been disclosed to reduce further processing of the control finger.

Here, for powder injection molding, a predetermined metal powder and a binder (wax-based) are supplied together, and when the molding is completed, a degreasing process of removing the binder is performed. At this time, the degreasing process is performed by applying a predetermined heat.

The degreasing process of performing degreasing while applying heat requires a lot of time, such as 48 hours or more, so there is a problem that productivity is lowered.

As prior art for the present invention, there may be exemplified Patent Registration No. 10-0471859 and US Patent No. 9,095,905.

An object of the present invention is to solve the above problems, and an object thereof is to provide a control finger manufacturing method capable of having a final shape for obtaining a final shape without an additional processing process after the control finger is manufactured.

In addition, an object of the present invention is to provide a control finger manufacturing method capable of removing a binder within a short time after forming the control finger.

In order to achieve the above object, the present invention comprises: preparing a metal powder and a binder as raw materials for manufacturing a control finger; Kneading the metal powder and the binder; Injection molding the kneaded raw material in a control finger forming mold; Degreasing the binder of the formed body in a nitric acid atmosphere; Sintering the degreased green body; And post-treating the formed sintered body. It provides a method of manufacturing a control finger using metal powder injection molding comprising a.

The metal powder may include carbon, nickel and iron.

The diameter of the metal powder may be 1 to 25㎛.

The binder comprises a first binder containing 80 to 95% POM (polyacetal), 1 to 5% wax (including carnauba wax or paraffin wax), and 1 to 2% stearic acid, and 1 to 10% polymer. It may include a second binder to include.

The polymer may include any one or two or more selected from EVA, PC, PP, and PE.

The kneading may include injecting the metal powder and the binder into a kneader, and heating the metal powder and the binder at 170 to 190° C. for 2 to 4 hours.

The metal powder and the binder may be prepared in 55 to 65 vol% and 35 to 45 vol%, respectively.

The injection molding may be performed by a nozzle maintaining a temperature of 190-200°C.

The temperature of the mold may be 100 to 130°C.

The degreasing may include charging the molded body into an oven, preparing nitric acid and nitrogen, injecting the nitric acid into the oven to evaporate it, and supplying the nitrogen into the oven. , Maintaining the molded body in the oven and removing the first binder.

The oven may be maintained at 110 ~ 125 ℃.

The nitric acid may be supplied at 1 to 10 ml/min and nitrogen at 1 to 5 l/min.

In the maintaining step, after supplying the nitric acid and the nitrogen, the molded body may be maintained in the oven for 4 to 8 hours.

The second binder may be removed by performing the sintering step.

In the present invention as described above, the final shape can be obtained without an additional processing process after the control finger is manufactured, and the binder can be removed within a short time (4 to 8 hours) after the control finger is formed.

1 is a flow chart showing the configuration of a method of manufacturing a control finger according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flow chart showing the configuration of a method of manufacturing a control finger according to an embodiment of the present invention.

Referring to FIG. 1, a method of manufacturing a control finger according to an embodiment of the present invention includes preparing a mold (ST110), preparing a raw material (ST120), kneading the raw material (ST130), and injection molding. (ST140), degreasing (removing the binder from the molded body) (ST 150), sintering (ST160), and post-processing (ST170).

In the step of preparing a mold (ST110), a mold used for manufacturing a control finger is prepared. The prepared mold may be formed in a predetermined shape so that the control finger can be manufactured by metal powder injection molding.

In the step of preparing a raw material (ST120), a raw material used for manufacturing a control finger is prepared, and a metal powder and a binder are prepared.

Let's look at the raw materials to be prepared.

First, an alloy powder containing carbon, nickel, and iron is prepared as a metal powder.

As the metal powder, an alloy powder containing 0.4 to 0.6% by weight of carbon (C), 1.5 to 2.5% by weight of nickel (Ni), and less than 1% by weight of micro-alloy elements may be prepared.

Here, the size of the diameter of the prepared metal powder may be 1 to 25 μm. In addition, it is preferable that the metal powder is spherical.

And, a binder may be prepared.

The binder includes a first binder and a second binder.

The first binder contains 80 to 95% of POM (polyacetal), 1 to 5% of wax (including carnauba wax or paraffin wax), and 1 to 2% of stearic acid as a surfactant. The first binder may be removed in the step of degreasing described later.

The second binder may contain 1 to 10% of a polymer. Here, the polymer may include any one or two or more selected from EVA, PC, PP, and PE.

The second binder may be removed in the sintering step described later.

POM, the main component of the first binder, increases the strength of the injection body, and is then eroded by nitric acid in the degreasing process, decomposed into monomers in the polymer, and removed within a short time. In addition, wax is added to have an appropriate fluidity for injection molding, and stearic acid serves as a surfactant so that the metal powder and the binder can be well mixed.

The second binder, the polymer, plays a role in maintaining the strength of the degreasing body in place of the POM that is removed within a short time in the degreasing step, and is also referred to as a backbone binder. It is then removed by pyrolysis in the initial stage of sintering.

When the metal powder and the binder are prepared, they are mixed with each other.

In this case, the metal powder and the binder may be mixed with each other in 55 to 65 vol% and 35 to 45 vol%, respectively. This mixing ratio depends on the shape or size of the product, and the higher the powder fraction, the lower the fluidity. Therefore, the injection length is shortened, so whether the inside of the mold can be stably filled determines the mixing ratio.

The mixed metal powder and the binder are supplied to the kneader and then heated to 180° C. and kneaded for 2 hours. After the kneading is completed, the mixed metal powder and the binder are cooled to room temperature and pulverized to an appropriate size to be used as a material for injection molding.

In the step of injection molding (ST140), the prepared metal powder and the binder are uniformly mixed, and then injected into the prepared mold using a predetermined nozzle, and a molded body is manufactured by injection molding.

At this time, the nozzle is preferably maintained at 190 to 200 degrees Celsius.

If the temperature of the nozzle is less than 190 degrees Celsius, the material may not reach the end of the mold due to insufficient fluidity of the injection material. In addition, when the temperature of the nozzle exceeds 200 degrees Celsius, the binder component having a low melting point may be vaporized to form pores in the injection body.

In addition, when the mixture of the metal powder and the binder is injected through the nozzle, it may be injected by a predetermined injection pressure.

The following [Table 1] shows the injection length and spiral test results according to the nozzle temperature.

Nozzle temperature (℃) 170 180 190 Torque (m·g) 120 110 95 Injection length 300mm 340mm 365mm Spiral
Test
result

Remark Unmolded Unmolded normal

As described in [Table 1], it is desirable to properly maintain the temperature of the nozzle for normal molding of the product. The normal molding of the product means that the injection molding material reaches the end of the mold cavity to form a complete injection body without any unfilled parts.

In addition, when performing the injection molding step (ST140), the temperature of the mold is preferably 100 to 130 ℃. When the temperature of the mold is maintained below 100°C, solidification of the binder component in the material may occur before the injection material reaches the end of the mold. In addition, when the temperature of the mold is maintained at 130° C. or higher, pores may remain inside the injection body through vaporization of the low melting point binder component of the injection material.

In addition, a complete injection molded body can be obtained only when an appropriate injection speed, pressure and holding pressure are given. The injection speed, pressure, and holding pressure can be set in various ways according to the needs of the user.

The step of degreasing (ST150) is a step of removing the binder included in the injection molded body formed in the mold.

The step of degreasing (ST150) is performed as follows.

After removing the molded body from the mold, it is charged into a predetermined oven (ST151), and the oven temperature is maintained at 110°C.

First, the user prepares nitric acid and nitrogen (ST152).

At this time, the concentration of nitric acid prepared may be 90%.

When nitric acid and nitrogen are prepared, nitric acid is vaporized (ST153). Vaporization of nitric acid can be accomplished as follows.

Liquid nitric acid is supplied to an oven in which the injection body is loaded, so that the nitric acid is vaporized by the temperature of the oven. At this time, nitric acid may be supplied at 5 ml/min.

Also, nitrogen may be supplied along with nitric acid. At this time, nitrogen can be supplied at 1 to 5 l/min.

The lower limit of the flow rate of nitric acid and nitrogen is related to the degreasing reaction rate. If the concentration of evaporated nitric acid is too thin, the binder in the molded body cannot be removed effectively or degreasing takes too long. It reacts with the powder and corrodes it, causing a problem in that sintering is not smoothly performed in the subsequent sintering process.

The vaporized silver nitrate contacts the injection body so that the binder is removed.

After supplying nitric acid and nitrogen, the molded body is kept in an oven for 4 to 8 hours (ST155) so that degreasing is performed. In this case, as the thickness of the molded body increases, the holding time may be extended.

The POM included in the first binder is decomposed and removed from the polymer into monomers by nitric acid, but the backbone binder, that is, the second binder that maintains the strength of the molded body even after the degreasing process is completed, is not removed.

In the sintering step (ST160), after the degreasing is completed, the molded body is maintained for 3 hours in a sintering furnace maintained at 1270° C. for a predetermined time, and sintering is performed.

During sintering, the second binder, the polymer, may be removed.

The post-treatment step (ST170) includes all additional processes necessary to produce the sintered body as a final product, such as applying pressure to determine the size of the sintered body and performing sizing processing or high-frequency heat treatment on the required part, if necessary. .

According to the present invention, after the control finger is manufactured, it is possible to have a final shape for obtaining the final shape without an additional processing process, and the binder can be removed within a short time after the control finger is formed.

The present invention has been described with reference to the embodiments shown in the drawings, but these are merely exemplary, and those of ordinary skill in the art will appreciate that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical scope of the present invention should be determined by the technical spirit of the appended claims.

Claims (14)

As a method of manufacturing a control finger,
Preparing a metal powder and a binder as raw materials for manufacturing a control finger;
Kneading the metal powder and the binder;
Injecting the kneaded raw material into a mold for forming a control finger having a temperature of 100 to 130°C through a nozzle maintaining 190 to 200°C, and injection molding;
Degreasing the binder of the formed body in a nitric acid atmosphere;
Sintering the degreased green body; And
Post-treating the formed sintered body;
Method of manufacturing a control finger using metal powder injection molding comprising a. The method of claim 1,
The metal powder is a method of manufacturing a control finger containing carbon, nickel and iron. The method of claim 2,
The method of manufacturing a control finger having a diameter of the metal powder of 1 to 25㎛. The method of claim 2,
The binder,
A first binder containing 80 to 95% of POM (polyacetal), 1 to 5% of wax (including carnauba wax or paraffin wax), and 1 to 2% of stearic acid,
A method of manufacturing a control finger comprising a second binder containing 1 to 10% polymer. According to claim 4
The polymer is EVA, PC, PP, PE, a method of manufacturing a control finger comprising any one or two or more selected from. The method of claim 1,
The kneading step,
Injecting the metal powder and the binder into a kneader,
A method for manufacturing a control finger comprising heating the metal powder and the binder at 170 to 190°C for 2 to 4 hours. The method of claim 6,
The method of manufacturing a control finger wherein the metal powder and the binder are prepared in 55 to 65 vol% and 35 to 45 vol%, respectively. delete delete The method of claim 4,
The step of degreasing,
Charging the molded body into an oven,
Preparing nitric acid and nitrogen, and
Injecting the nitric acid into the oven to evaporate it,
Supplying the nitrogen into the oven,
And removing the first binder while maintaining the molded body in the oven. The method of claim 10,
The oven is a method of manufacturing a control finger maintained at 110 ~ 125 ℃. The method of claim 11,
The method of manufacturing a control finger in which the nitrate is supplied at 1 to 10 ml/min and the nitrogen at 1 to 5 l/min. The method of claim 11,
The maintaining step,
After supplying the nitric acid and the nitrogen, the method of manufacturing a control finger for maintaining the molded body in the oven for 4 to 8 hours. The method of claim 4,
The second binder is a method of manufacturing a control finger that is removed by performing the sintering step.

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