KR101385930B1 - Manufacturing method of insert screw - Google Patents

Abstract

The present invention relates to a method of manufacturing an insert screw, which includes: a core manufacturing step of supplying a mixture of metallic powders including a first metallic material with a binder into an injector to inject a core mold, removing the binder from the core mold, and sintering the core mold to manufacture the core; a screw manufacturing step of forging a second metallic material having strength lower than that of the first metallic material and manufacturing a screw body provided at an upper portion thereof with a fitting groove; and a bonding step of binding the core with the screw body after the core has been inserted into the fitting groove. As described above, according to the present invention, the binder is mixed with the metallic powders, and the mixture is injection-molded to manufacture the core. Thereafter, the core is bonded to the screw body subject to the cold forging process, so that the insert screw can represent higher strength and can be easily manufactured. Accordingly, the abrasion or the deformation of the head part of the insert screw cannot only be previously prevented, but also the manufacturing time of the insert screw can be reduced, so that the productivity of the insert screw can be remarkably improved. [Reference numerals] (S10) Manufacture a core.; (S11) Inject; (S12) Remove grease; (S13) Sintering; (S20) Manufacture screw.; (S31) Form a plating thin film on an outer surface of a core.; (S32) Brazing

Description

Manufacturing method of insert screw

The present invention relates to a method for manufacturing an insert screw, and more particularly, it is possible to easily manufacture while having a high strength to prevent the wear or deformation of the head portion in advance, as well as to shorten the manufacturing time to improve productivity It relates to a method for producing an insert screw that can be greatly improved.

As is well known, the insert screw is used to screw together two or more components to mutually join a plurality of components. Generally, the screw is integrally formed with a screw body having a threaded line on its outer surface and a screw body on the top of the screw body. And the upper surface is formed of a head portion formed with an insertion groove for inserting a screwdriver for rotating the screw body.

The insert screw is divided into various types depending on the shape of the thread and the shape of the insertion groove of the head, and the size and shape of the insert screw is standardized to meet the intended use as it is used in various places including parts of the machine.

In addition, the insert screw requires a certain level of strength to insert a driver into the insertion groove and rotate the inserted driver to assemble a plurality of parts. The insert screw is mainly manufactured by forging to meet such strength.

On the other hand, when the insert screw is manufactured by using a high strength metal such as cemented carbide to increase the strength, it is difficult to process a complicated shape such as a screw thread because of its low workability, and the unit cost is remarkably increased as the working time required for machining increases. Since it rises, chromium molybdenum steel (SMC4) is mainly transformed into martensitic structure to have a certain level of workability and strength.

Here, the manufacturing method of the conventional insert screw in more detail, cold forging the chromium molybdenum steel (SMC4) to process the screw body and the head unit integrally, and then heat it to the quenching temperature of the chromium molybdenum steel screw body and the head portion It is prepared by transformation into martensite tissue.

In other words, the conventional insert screw manufacturing method includes a transformation process of heating it to a quenching temperature of the chromium molybdenum steel through a cold forging process. there was.

In addition, in the conventional insert screw manufacturing method, even when the chromium molybdenum steel is transformed to improve its strength, the head part is worn or deformed as the tool part of the driver having considerable rigidity is inserted into the insertion groove and rotates with considerable force. .

The present invention has been made to solve the above problems, the object of the present invention is not only to prevent the wear or deformation of the head portion in advance by making it easy to manufacture while having a high strength as well as manufacturing time It provides a method of manufacturing an insert screw that can be shortened to significantly improve productivity.

According to an aspect of the present invention for achieving the above object, in the manufacturing method of the insert screw comprising a screw body, a core is formed on one side and the core is joined to one side of the upper end of the screw body, A core manufacturing step of manufacturing a core by supplying a metal powder made of a metal material and a mixture of a binder mixed with an injection molding machine to inject a core molded product, degreasing the binder contained in the core molded product, and then sintering the binder. A screw manufacturing step of manufacturing a screw body having a fitting groove formed thereon by forging a second metal material having a lower strength than that of the metal material and joining the core and the screw body after inserting the core into the fitting groove. Including, but the bonding step to form a plating film on the outer surface of the core manufactured through the core manufacturing step Inserting the core into the plating step and the fitting groove, and heating the screw body into which the core is inserted above the quenching temperature of the screw body to braze the core and the screw body through the plating film. At the same time provides a method for producing an insert screw, characterized in that it comprises a brazing step for transforming the screw body.

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In addition, the plating film is made of 40 to 90% by weight of silver, 10 to 60% by weight of copper, it may be formed to have a thickness of 0.1 ~ 0.3 ㎛.

The plating film is preferably formed to be inclined downward from the upper end of the outer surface of the core in the inner direction of the core.

In the core manufacturing step, an injection step of injection molding a core molded body having a shape corresponding to the core by supplying a mixture of a metal powder and a binder to an injection machine, and applying a solvent to the core molded product injected in the injection step A degreasing step of firstly removing a part of the binder from the core molded body by heating and sintering by heating the core molded body to a predetermined temperature and sintering the secondary molded body to prepare the core by secondly removing the binder contained in the core molded body. It may include a step.

In addition, the metal powder in the injection step is made of 92 ~ 97% by weight of tungsten carbide, 3 ~ 8% by weight of cobalt, the binder 50 ~ 95% by weight of the main binder, 2 ~ 40% by weight of the auxiliary binder, dispersion reinforcing agent It consists of 1 to 10% by weight and 0.1 to 2% by weight of plasticizer, the mixture is preferably prepared by introducing 80 to 95% by weight of the metal powder, 5 to 20% by weight of the binder into the kneader, and mixing it while heating. Do.

In addition, the main binder is a copolymer-based polyacetal resin, the auxiliary binder is a polyolefin-based low density thermoplastic resin, the dispersion reinforcing agent is any one of paraffin wax (Caraffin Wax) or carnauba wax (Canauba Wax), the plasticizer May be either stearic acid amide or dioctylphthalate.

According to the present invention as described above, by mixing the binder in the metal powder, and injection molding it to produce a core and then bonded to the screw body processed by cold forging to have a high strength and easy to manufacture the head portion Not only can the wear or deformation be prevented in advance, but the manufacturing time can be shortened, thereby significantly improving productivity.

In addition, the present invention is to form a plating film on the outer surface of the manufactured core after brazing the core to the screw body, the core body is bonded to the screw body in the process of bonding the core and the screw body by heating the screw body above the hardening temperature of the screw body By transforming to have an effect that can significantly shorten the manufacturing time.

1 is a flow chart of the manufacturing method of the insert screw according to an embodiment of the present invention,
Figure 2 is a side view of the core and the screw body 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 of a method for manufacturing an insert screw according to an embodiment of the present invention, Figure 2 is a side view of the core and the screw body according to an embodiment of the present invention.

As shown in Figure 1, the manufacturing method of the in-circuit screw according to an embodiment of the present invention comprises a core manufacturing step (S10), a screw manufacturing step (S20) and a bonding step (S30).

Core manufacturing step ( S10 )

Core manufacturing step (S10) according to an embodiment of the present invention is an injection step (S11) for injection molding the core molded body, a degreasing step (S12) for degreasing a part of the binder included in the core molded body and the sintered core molded body It is configured to include a sintering step (S13), it is a step for producing a tungsten carbide (WC), that is, a carbide 11 core.

In the injection step (S11), 80 to 95% by weight of the metal powder and 5 to 20% by weight of the binder are charged into the kneader, and the mixture is kneaded at a temperature of 160 to 180 ° C. for 120 minutes by pressing / heating to the surface of the metal powder. Bond as if homogeneously coating the binder.

More specifically, when the metal powder and the binder are mixed, tungsten carbide 92 ~ 97% by weight, cobalt 3 ~ 8% by weight of the metal powder of the copolymer-based polyacetal resin as the main binder, and the polyolefin-based low density thermoplastic resin as the sub-binder After premixing (Premixing) and charged into the kneader, and the first mixing for 1 hour in the heating temperature 160 ~ 180 ℃ section.

Thereafter, any one of a paraffin wax or a carnauba wax as a lubricant and one of the plasticizer stearic acid amide or dioctylphthalate is added and mixed for about 1 hour in the same environment.

The reason for dispersing the binder and mixing it with the metal powder is that if a highly volatile lubricant and a plasticizer are present at a relatively low temperature in the binder component for a long time at a mixing temperature, a part of the component may volatilize and the binder content may change. This is to minimize this.

The binder is preferably composed of 50 to 95% by weight of the main binder, 2 to 40% by weight of the auxiliary binder, 1 to 10% by weight of the dispersion enhancer, and 0.1 to 2% by weight of the plasticizer.

Here, as a binder, the reason for including 1 to 10% by weight of the dispersion reinforcing agent is that when the content of the dispersion reinforcing agent exceeds 10% by weight, the core molding is formed while the fluidity of the feedstock (feedstock), which is a raw material of the injection molding material, increases. This is because the problem is not maintained, the content of the dispersion reinforcing agent is less than 1% by weight because the flowability of the injection molding for injecting the core molded product is less because the problem of not molding the core molded properly.

After the mixture is solidified at room temperature, it is pelletized in a grinder to facilitate injection molding, and used as a feedstock, which is a raw material for injection molding. The feedstock is introduced into an injection machine hooper. After setting the injection nozzle to 160 ~ 200 ℃, inject the core molded product by adjusting the mold temperature, injection temperature, injection pressure and speed in consideration of the mold shape, the product to be molded and the shape of the core 11. .

On the other hand, the binder according to an embodiment of the present invention to improve the fluidity of the core molded body by adding a lubricant and a plasticizer in addition to the main binder and the auxiliary binder, which is a polymer component, even if the injection machine nozzle temperature is 160 ~ 200 ℃ mold temperature is 70 Injection molding is possible below < RTI ID = 0.0 >

The degreasing step (S12) is a process of firstly removing the dispersing agent which is a low melting point binder and a plasticizer among the binders included in the core molded body, and the hexane is used as the solvent as the solvent is extracted through the solvent extraction process. The temperature is raised to 40 ℃ to remove the dispersion enhancer and plasticizer.

At this time, even if the dispersing enhancer and the plasticizer are rapidly degreased within a short time, the core molded body can be maintained without its own weight by the polyolefin-based low density thermoplastic resin, i.e., polyethylene, which is an auxiliary binder.

On the other hand, in the present embodiment, but the solvent degreasing method has been described as a method of degreasing the binder, the present invention is not necessarily limited to this, if the method can be degreased while maintaining the shape of the core molded body is applied in any way. It is possible.

In the sintering step (S13), the core molded body is heated to the degreasing temperature of the main binder and the auxiliary binder to remove the main binder and the auxiliary binder included in the core molded product, and the core molded body is manufactured by sintering and cooling the core molded body. It's a step.

In other words, the sintering step (S13) according to an embodiment of the present invention is a degreasing process and the sintering process of the binder at the same time, using a high vacuum sintering furnace and the maximum temperature 400 ~ 600 ℃ in a mixed gas atmosphere of hydrogen and nitrogen After the first sintering to degrease the main binder and the auxiliary binder for 8 hours in a section, the second sintering was carried out by maintaining the temperature in a vacuum atmosphere at a temperature of 1200 to 1500 ° C. for 120 minutes for the second time, and cooling the same to prepare a carbide core 11. do.

screw  Manufacturing stage ( S20 )

The screw body 12 includes a screw body having a screw thread formed on an outer surface thereof, and a coupling part having a fitting groove 12a formed at an upper portion of the screw body and to which the core 11 is joined, such a screw body 12. Unlike the core 11 is manufactured by forging a common chromium molybdenum steel (SMC4).

In this case, when the small insert screw is processed in hot forging, the shape of the screw is deformed as a part of the screw is oxidized by the high temperature, so it is preferable to process the cold forging to prevent this.

On the other hand, the manufacturing method of such a screw, that is, cold forging is known to those of ordinary skill in the art that it is obvious that the specific description will be omitted.

Joining step ( S30 )

Joining step (S30) is a plating step (S31) for forming a plating film 13 on the outer surface of the core 11 manufactured through the sintering step (S13), and inserting the core 11 in the fitting groove (12a) It comprises a brazing step (S32) for brazing the core 11 and the screw body 12, to manufacture the insert screw by joining the cemented carbide core 11 to the screw body 12 made of chromium molybdenum steel Step.

Plating step (S31) is a step of forming a plating film 13 on the outer surface of the core 11, a method for forming the plating film 13 by spraying a plating solution on the outer surface of the core 11 core 11 A spraying method for forming the plating film 13 on the outer surface of the electrolytic plating method, and the electrolytic plating for forming the plating film 13 on the outer surface of the core 11 by immersing the core 11 in the plating bath containing the plating solution. Any one of the methods may be used. In this embodiment, an electrolytic plating method is used.

At this time, the plating liquid for forming the plating film 13 on the outer surface of the core 11 is a brazing solvent with an alloy plating film made of 40 to 90 wt% of silver and 10 to 60 wt% of copper. It is a substitute material. The Ag-Cu alloy has a melting point at 780 ° C with 72% Ag and 28% Cu. The brazing temperature can be controlled according to the alloy composition.

In addition, the plating film 13 serves as an adhesive for bonding the core 11 and the screw body 12 while melting in the brazing step (S32) to be described later when the plating film 13 is less than 0.1㎛ in the brazing step When the heating is melted, there is a problem that the adhesion performance of bonding the core 11 and the screw body 12 is greatly reduced, and when the plating film 13 exceeds 0.3㎛, the core 11 and the screw body 12 The plating force formed on the outer surface of the core 11 because the adhesive force between the cores 11 may flow out of the screw body 12 and move away from the screw body 12 according to the ductility of the alloy plating film of silver and copper. The film 13 is preferably formed to have a thickness of 0.1 to 0.3 mu m.

In addition, the alloy plating film is composed of 0.1 to 10 g / L of silver cyanide, 5 to 40 g / L of copper cyanide, and 15 to 70 g / L of free cyanide. A solution composition containing additives such as lotel salt, dimethylamine salt, and selenium salt. The precipitation process conditions of Ag-Cu alloy plating have a temperature condition of 20-65 ° C. and precipitate under a current density of 0.1-5 ASD. The plating film may form a plating thickness that may be brazed at a thickness of at least 0.1 μm depending on the process conditions.

On the other hand, the plating film 13 formed on the outer surface of the core 11 is formed to be inclined downward from the upper end of the outer surface of the core 11 inward direction of the core 11 so that the core 11 is easily fitted into the fitting groove 12a. It is desirable to allow the Ag-Cu alloy plated film having a solubility property to be inserted in the brazing state so as to be inserted and to prevent the Ag-Cu alloy plated film from flowing down in a semi-melted state so that the bondability between the core 11 and the screw body 12 can be improved. .

Brazing step (S32) is a step of joining the core 11 and the screw body 12, and transforming the screw body 12 into martensite structure, fixing the lower end of the screw body 12 to the jig prepared in advance Then, under a vacuum atmosphere, the temperature of the hardening of the screw body 12, that is, the transformation temperature is increased to 850 to 870 ° C. and maintained for 40 minutes.

The screw body 12 is transformed into a martensite structure, the plating film 13 formed on the outer surface of the core 11 is melted and adhered to one side of the core 11 and the screw body 12, which is nitrogen gas The insert screw is manufactured by quenching using.

As described above, in this embodiment, after the plating film 13 is formed on the outer surface of the core 11 in the brazing step S32, the core 11 is brazed to the screw body 12, but the screw to which the core 11 is bonded is formed. The body 12 is heated above the quenching temperature of the screw body 12, that is, at the transformation point, so that the screw body 12 is transformed into martensite structure during the joining of the core 11 and the screw body 12. There is a feature that can be significantly shortened.

Although the present invention has been described in connection with the above-mentioned embodiment, it is possible to make various modifications and variations without departing from the spirit and scope of the invention. Accordingly, the appended claims are intended to cover such modifications or changes as fall within the scope of the invention.

11: core 12: screw body
12a: fitting groove 13: plated film

Claims (7)

In the manufacturing method of the insert screw comprising a screw body, and a core insertion groove is formed on one side and joined to one side of the upper end of the screw body,
A core manufacturing step of manufacturing a core by supplying a metal powder made of a first metal material and a binder mixed with a binder to an injection molding machine to inject a core molded product, degreasing the binder contained in the core molded product, and then sintering the binder;
A screw manufacturing step of manufacturing a screw body having a fitting groove formed thereon by forging a second metal material having a lower strength than the first metal material; And
Including the bonding step of bonding the core and the screw body after inserting the core into the fitting groove,
The bonding step
A plating step of forming a plating film on an outer surface of the core manufactured through the core manufacturing step; And
The core is inserted into the fitting groove, and the screw body into which the core is inserted is heated above the quenching temperature of the screw body, thereby brazing the core and the screw body through the plating film and simultaneously the screw body. Method for producing an insert screw, characterized in that it comprises a brazing step to be transformed.
delete The method of claim 1,
The plating film is made of 40 to 90% by weight of silver, 10 to 60% by weight of copper, the method of manufacturing an insert screw, characterized in that formed to have a thickness of 0.1 ~ 0.3 ㎛.
The method of claim 1,
The plating film is a manufacturing method of the insert screw, characterized in that formed inclined downward from the upper end of the outer surface of the core in the inward direction of the core.
The method of claim 1,
The core manufacturing step
An injection step of injection molding a core molded body having a shape corresponding to the core by supplying a mixture of a metal powder and a binder to an injection machine;
A degreasing step of first removing a part of the binder from the core molded body by adding a solvent to the core molded body injected in the injection step; And
And a step of manufacturing the core by heating the core molded body at a predetermined temperature and sintering the secondary molded product and removing the binder contained in the core molded product.
6. The method of claim 5,
In the injection step
The metal powder is made of tungsten carbide 92 ~ 97% by weight, cobalt 3 ~ 8% by weight,
The binder is composed of 50 to 95% by weight of the main binder, 2 to 40% by weight of the auxiliary binder, 1 to 10% by weight of the dispersion enhancer and 0.1 to 2% by weight of the plasticizer,
The mixture is 80 to 95% by weight of the metal powder, 5 to 20% by weight of the binder is introduced into the kneader, and the method for producing an insert screw, characterized in that the manufacturing by mixing while heating.
The method according to claim 6,
The main binder is a copolymer polyacetal resin,
The cobinder is a polyolefin low density thermoplastic resin,
The dispersion enhancer is any one of a paraffin wax or a carnauba wax.
The plasticizer is a method of producing an insert screw, characterized in that any one of stearic acid amide or dioctyl phthalate.

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