KR101547442B1 - Method for manufacuring a helical gear using powder metallugy - Google Patents

Abstract

The present invention relates to a method for manufacturing powder metallurgy of a helical gear capable of manufacturing a helical gear with powder metallurgy with improved high hardness, wear resistance, lubricating properties, and corrosion resistance in order to be used as a deceleration gear whose rotation number is few but a compressive force is high. Moreover, the method for manufacturing powder metallurgy of a helical gear which is a cylindrical gear for transmitting rotary motion between two parallel shafts, and wherein a teeth of the gear is inclined to one side comprises: a powder mixing step for forming metal powder by mixing an additive including 4.5-5.5 wt% of nickel (Ni), 2.7-3.3 wt% of copper (Cu), 0.7-0.9 wt% of molybdenum (Mo), 0.3-0.5 wt% of manganese (Mn), 0.1-0.3 wt% of silicon (Si), 1.3-1.7 wt% of carbon, and 0.3-0.7 wt% of a lubricant, and a main raw material of other residual iron (Fe); a powder forming step for pressing and forming after inserting the metal powder into a mold having a cavity coupled with the helical gear; a powder sintering step for applying heat to the powder pressed and formed in the form of the helical gear by the mold at a certain temperature for a certain time; a post processing step of post processing a sintered body wherein powder is sintered; and an electroless nickel plating step for electroless nickel plating the surface of the sintered body post processed.

Description

METHOD FOR MANUFACURING A HELICAL GEAR USING POWDER METALLURG

The present invention relates to a method of manufacturing a honeycomb structure by using a powder metallurgy in which a metal powder is press-formed by press-forming a helical gear in which gear teeth of gears are tilted to one side of a cylindrical gear for transmitting rotational motion between parallel shafts, The present invention relates to a method of manufacturing a powder metallurgy of a helical gear to be manufactured.

Generally, various gears are installed in a power transmitting portion that is applied to a mechanical device, an automobile or the like to transmit power, or an accelerating / decelerating reducer. A gear is a mechanical component consisting of gears connected to a rotating shaft. The gears work in pairs, and the teeth of one gear engage with the teeth of the other gears to transmit or rotate the rotational and rotational forces without slip.

Most of the gears are circular, and the contact surfaces of the gear teeth must be precisely shaped in order to smoothly transfer the motion at a constant speed ratio at all times. The axes connecting these gears should be relatively close together, but in practice there is some spatial relationship between them. That is, not parallel to, not intersecting, and not intersecting.

And a spur gear and a helical gear as cylindrical gears for transmitting rotational motion between the two parallel shafts. Among them, the helical gear is formed by the teeth of the gears tilted to one side, and the transmission is smooth, vibration and noise are small, and it is mainly used for transmitting large power.

Conventional gear manufacturing methods including helical gears as described above can be largely divided into a cutting method and a non-cutting method. There are various methods such as hobbing and gear saving in the cutting method. However, in general, Polishing, lapping or the like. Non-cutting methods include gear forming by plastic forming using metal forming processes such as casting, forging, rolling, extrusion and powder metallurgy. Among them, the casting method is disadvantageous from the viewpoint of quality and productivity and is not widely used. Researches on gear forming method by plastic forming suitable for mass production have been actively carried out.

Examples of the gear forming method by the above-mentioned plastic working include cold extrusion, precision forging, tempering, powder metallurgy and the like. Of these, powder metallurgy is a method in which a metal powder is pressed and formed, , Which is characterized in that a uniform and dense structure can be obtained without secondary processing as compared with other processing.

As a result, the present developer can not produce a helical gear having high strength and high strength so that it can be used as an industrial reduction gear, especially a reduction gear of a green juicer or a raw-material machine, and can be used as a reducer having a high compression force. This study was conducted.

SUMMARY OF THE INVENTION It is an object of the present invention, which is conceived from the above-described viewpoints, to provide a helical gear having improved hardness, wear resistance, lubrication characteristics and corrosion resistance so that the helical gear can be used as a reduction gear having a small number of revolutions, And a manufacturing method thereof.

Other objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments with reference to the accompanying drawings.

In order to accomplish the above object, a method of manufacturing a powder metallurgy of a helical gear according to the present invention is a cylindrical gear for transmitting rotational motion between two parallel shafts, and the powder metallurgy of the helical gear, (Mn), 0.3 to 0.5% by weight of silicon (Si), 0.1 to 5% by weight of silicon (Si), 0.5 to 3% A powder mixing step of adding the additive containing 0.3 wt% to 0.3 wt% of carbon, 1.3 wt% to 1.7 wt% of carbon, and 0.3 wt% to 0.7 wt% of lubricant and the balance material of remaining balance iron (Fe) to form the metal powder; A powder forming step of putting the metal powder into a mold having a cavity formed thereon and pressing the powder to form a powder; and a step of heating the powder, which is press-molded in the shape of the helical gear, And applying the powder sintering stage, characterized in that it comprises a post-treatment step, and a step of nickel plating by electroless plating on the surface of the post-processing the sintered body to an electroless nickel plating in which the powder has a post-processing of sintered sintered body.

The powder mixing step may be performed by mixing 5.0 wt% of nickel, 3.0 wt% of copper, 0.8 wt% of molybdenum, 0.4 wt% of manganese (Mn), 0.2 wt% of silicon (Si) And 0.5% by weight of a lubricant, and the balance of the remaining amount of iron (Fe) are mixed to form the metal powder. In the powder sintering step, the powder is heated to a constant temperature for a certain period of time, The lubricant is removed, and the sintered body from which the lubricant is removed is characterized in that the content of iron (Fe) as the main material is 89.1% by weight.

The post-treatment step includes a high-frequency surface hardening step of hardening the surface of the sintered body by high-frequency induction heating.

The post-treatment step may include a barrel step of removing the sharp edges of the sintered body and polishing the surface for luster, and a rust-preventing step of sealing the pores of the sintered body to coat the rust- .

The electroless nickel plating step may include an alkali degreasing step of electrolytically degreasing and washing the sintered body with a weak alkaline agent, an acid degreasing step of degreasing the sintered body with an acidic solution and then washing the sintered body with nickel hydroxide And a nickel plating step of washing with water after electroless plating.

Further, the alkaline degreasing step, the voltage to the approximately alkali caustic soda (NaOH), sodium carbonate (NA ₂ CO ₃₎ or triphosphate soda 5 to 15V by (NA ₃ PO ₄₎ using at least any one or more of a mixture of and And the sintered body is electrolytically degreased by applying a current of 2500 to 3500A.

Also, the acid degreasing step is characterized in that the acid is degreased for a predetermined time using an acidic solution of hydrochloric acid and sulfuric acid, a surfactant, and a corrosion inhibitor.

The nickel plating step may be performed by depositing the sintered body on the nickel plating solution containing nickel sulfate, sodium hypophosphite, citric acid and potassium sulfate, adjusting the plating temperature to 80 to 100 ° C and adjusting the pH to 4 to 6, Is characterized in that the sintered body is nickel electrolessly plated for 10 to 15 minutes.

The sintered body is characterized in that nickel (Ni) is 92% by weight and phosphorus (P) is 8% by weight in the total plating weight of the surface after nickel electroless plating.

The sintered body is characterized in that the nickel plating layer has a surface thickness of 20 microns and a surface hardness of HV 560 to 600.

The method may further include a drying heat treatment step of drying the nickel-plated sintered body to remove water and then performing heat treatment at a temperature of 350 to 450 ° C.

The sintered body is characterized in that the nickel plating layer has a surface thickness of 20 microns and a surface hardness of HV 900 to 1000.

The method of manufacturing a powder metallurgy of a helical gear according to the present invention can provide a helical gear having improved hardness, wear resistance, lubrication characteristics, and corrosion resistance so that it can be used as a reduction gear having a small number of revolutions but high compression force.

1 is a flow chart showing a first embodiment of a method of manufacturing a powder metallurgy of a helical gear according to the present invention,
2 is a flowchart showing a second embodiment of a method of manufacturing powder metallurgy of a helical gear according to the present invention,
3 is a perspective view showing a sintered body of a helical gear having undergone the powder sintering step of the embodiment of FIG. 2,
FIG. 4 is a flowchart showing a third embodiment of a method of manufacturing powder metallurgy of a helical gear according to the present invention,
5 is a flowchart showing a fourth embodiment of a method of manufacturing powder metallurgy of a helical gear according to the present invention,
6 is a flowchart showing a fifth embodiment of a method of manufacturing powder metallurgy of a helical gear according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a method of manufacturing a powder metallurgy of a helical gear according to the present invention will be described in detail with reference to the accompanying drawings.

The method of manufacturing a powder metallurgy of a helical gear according to the present invention includes the steps of powder mixing (S100), powder forming (S200), powder sintering (S300), post-processing (S400) And a nickel plating step (S500). The post-treatment step S400 may include a high frequency surface hardening step S410, a barrel step S420 and a rust prevention step S430 as shown in FIG. 4, and the electroless nickel plating step S500 As shown in FIG. 5, may include an alkaline degreasing step S510, an acid degreasing step S520, and a nickel plating step S530, and further includes a drying heat treatment step S540 as shown in FIG. 6 .

3, the helical gear 100 is a cylindrical gear that transmits rotational motion between two parallel shafts, and the gear teeth of the helical gear 100 are tilted to one side, Is a method of manufacturing by powder metallurgy. Powder metallurgy is a plastic working method using a metal forming process by a non-cutting process. It is a method of making a product by pressing and molding a metal powder and then heating and sintering it at a high temperature. Secondary processing is unnecessary compared to other processes, And to obtain a precise organization. Particularly, the method of manufacturing a powder metallurgy of a helical gear according to the present invention is characterized in that a helical gear having high strength and high strength is used so that it can be used as an industrial reduction gear, particularly a reduction gear of a green juice machine or a raw material machine, And a powder metallurgy including a post-treatment process and an electroless nickel plating process.

For this purpose, iron (Fe) and other additives, which are main raw materials, are added to form a metal powder and subjected to a powder mixing step (S100). In the powder mixing step (S100), a mixer such as a double cone or a vicon is used for the purpose of mixing a base material and an additive for the production of the helical gear as a finished product or adding a lubricant. By adjusting the rotation speed and mixing time, And it is a very important process for homogenizing the quality.

Specifically, the powder mixing step (S100) may include: 4.5 to 5.5% by weight of nickel, 2.7 to 3.3% by weight of copper, 0.7 to 0.9% by weight of molybdenum, 0.3 to 0.5% 0.1 to 0.3% by weight of silicon (Si), 1.3 to 1.7% by weight of carbon and 0.3 to 0.7% by weight of a lubricant and the balance of the remaining amount of iron (Fe) are mixed to form the metal powder. (Ni), carbon (C), molybdenum (Mo), and manganese (Mn) are added in order to improve the strength together with the main raw material iron (Fe). Silicon (Si) and copper ) Is added. At this time, the lubricant is added to the mold and the powder to resist the high pressure and friction during the subsequent molding process, and is added to maintain the shape of the powder and protect the mold. Such a lubricant is removed through the powder sintering step (S300) do.

In the powder mixing step (S100), as shown in FIG. 2, the optimum mixing ratio of iron (Fe) and each additive, that is, the best combination of strength and strength, is 5.0 wt% , An additive comprising 3.0 wt% of copper (Cu), 0.8 wt% of molybdenum (Mo), 0.4 wt% of manganese (Mn), 0.2 wt% of silicon (Si), 1.5 wt% of carbon and 0.5 wt% (Fe) are mixed to form the metal powder. At this time, since the lubricant is removed through the powder sintering step (S300), the sintered body from which the lubricant is removed has a content of iron (Fe) as the main material of 89.1 wt%.

In order to form the metal powder according to the optimum compounding ratio in the powder mixing step S100 described above, the powder container is placed on the balance, the zero point setting is performed, and the iron powder (Fe) And the powder charged into the powder container is transferred to a mixer and mixed by rotating for 30 minutes to form a metal powder. The metal powders in which the raw materials and additives are uniformly mixed are formed through the powder forming step (S200) described below.

In the powder forming step (S200), the metal powder is put into a mold having a cavity formed in the helical gear (100) and pressurized to form the metal powder. The powder forming step (S200) is a first step in which the metal powder mixed in the powder mixing step (S100) is formed into a semi-finished product, that is, a powder. When the metal powder particles sufficiently bond to process a subsequent process To the extent that it does not interfere with the handling. For example, even in the case of a molded body molded by applying a high pressure, the bonding force between the metal powder particles is very small, even with a small stress, only in a state before the powder sintering step (S300) described later. Therefore, the sintered body must be made to be bonded at a high strength through the powder sintering step (S300) to be described later.

In the powder sintering step (S300), the powder press-molded in the shape of the helical gear (100) is heated by the mold at a constant temperature for a certain period of time. That is, in the powder sintering step (S300), each of the particles in the metal powder is bonded by an adhesive force between atoms by heating, thereby increasing the strength of the whole powder, causing the density to increase and recrystallization due to mass transfer. The metal powder particles are bonded only by heating at a temperature lower than the melting point of any one component of the system. In other words, as a kind of heat treatment performed at a temperature lower than the melting point of the base material Fe (Fe), diffusion of the metal powder particles occurs and chemical bonding is performed to obtain the required mechanical properties. Such heat treatment is called sintering do. These sintering effects are affected by the sintering temperature, time, atmosphere, heating rate, cooling rate, etc., and also affect the sintering characteristics. The sintered body of the helical gear 100 manufactured through the powder sintering step (S300) is shown in Fig. Such a sintered body is finished through a post-treatment step (S400) and an electroless nickel plating step (S500) described later.

In the post-treatment step (S400), the powder-sintered body is post-processed. For example, the post-treatment step S400 may increase the density of the sintered body to increase the density of the sintered body and increase the density of the sintered body. . In particular, the post-treatment step (S400) includes a high-frequency surface hardening step (S410) for inducing high-frequency induction heating on the surface of the sintered body as shown in FIG.

In the high-frequency surface hardening step (S410), an induction coil is wound around an area to be cured to flow an alternating current, rapidly heating the surface of the product by the generated heat, and then cooling the hardened surface. In other words, heat is generated by the eddy current loss and the hysteresis loss in the conductor such as metal located on the induction coil side where the alternating current flows, and heating the material to be heated by this heat is referred to as induction heating. At this time, there are hysteresis loss, eddy current loss, delay loss, and dielectric loss in the insulator. This high-frequency surface hardening step (S410) allows local heating, allows selection of the depth of the hardened layer, improves the heating efficiency, saves energy by shortening the working time, and is cost-effective. Further, the compression residual stress generated on the surface due to the rapid heating and quenching enhances the fatigue strength, is free from oxidation and decarburization, and is less deformed.

4, the post-treatment step S400 includes a barrel step S420 of removing the sharp edges of the sintered body and polishing the surface to polish the surface, and a step of sealing the pores of the sintered body to maintain airtightness (S430) for applying anti-corrosive oil to the electroless nickel plating step S500 to be described later. In the case of the barrel step S420, the surface of the sintered body is vortexed, vibrated, rotated, or the like is used. The sintered body and the grinding stone are appropriately moved so that the grinding stone rotates around the sintered body to perform a friction movement. Since the operation is carried out in water at a rotational speed of 10 to 25 rpm for about 30 to about 2 hours, the sintered body is liable to generate rubbing after the operation. Therefore, after the sintered body is sufficiently dried, the rustproofing step (S430) The surface of the sintered body should be rusted by applying anti-rust oil.

The electroless nickel plating step (S500) is a step of electroless nickel plating on the surface of the sintered body after finishing, and aims to enhance the hardness while improving the corrosion resistance, abrasion resistance and flexibility. Unlike electrolytic nickel plating, the electroless nickel plating is characterized in that even a product having a complicated shape such as the helical gear 100 can form a plated layer having a uniform plating thickness on the surface and forming a dense plated layer. The electroless nickel plating step S500 may include an alkaline degreasing step S510, an acid degreasing step S520, and a nickel plating step S530 as shown in FIG.

The alkaline degreasing step (S510) is a process of electrolyzing and degreasing the sintered body with a weak alkaline agent followed by washing with water, and simultaneously activates the contaminant removal on the surface of the sintered body. That is, oxygen generated from the metal surface of the sintered body penetrates and removes contaminants, and prevents the deposition of impurity metals which interfere with the plating adhesion in the case of anodic electrolysis. This alkali degreasing step (S510) by using at least any one or more of a mixture of caustic soda (NaOH), sodium carbonate (NA ₂ CO ₃₎ or triphosphate soda (NA ₃ PO ₄₎ as the weakly alkaline agent of 5 to 15V voltage and And the sintered body is electrolytically degreased by application of a current of 2500 to 3500A. The alkali-degreased sintered body is sufficiently washed with industrial water or other acid liquid.

The acid degreasing step (S520) is a step of degreasing the sintered body with an acidic solution followed by washing with water, thereby promoting the removal of contaminants dissolved in the scale, oxide film, rust and other acids, and activation of the surface of the sintered body. That is, it acts to neutralize the alkali in the alkali degreasing step (S510) and the removal of the thin oxide film. In this acid degreasing step (S520), the acid is degreased for a predetermined time using an acidic solution of hydrochloric acid and sulfuric acid, a surfactant, and a corrosion inhibitor. The acid-degreased sintered body is also sufficiently washed with industrial water or other acid-containing liquid.

In the nickel plating step S530, the sintered body is immersed in a nickel plating solution, electroless plated, and then washed with water. The electroless nickel plated layer plated on the surface of the sintered body is amorphous. Even if the thickness is increased, the crystal grains do not grow, a uniform surface can be obtained, and corrosion resistance and abrasion resistance are excellent. Specifically, the nickel plating step (S530) may be performed by depositing the sintered body on the nickel plating solution containing nickel sulfate, sodium hypophosphite, citric acid, and potassium sulfate, adjusting the plating temperature to 80 to 100 ° C and adjusting the pH to 4 to 6 While the sintered body is electroless nickel plated for 10 to 15 minutes. The nickel sulfate contained in the nickel plating solution is a nickel salt, sodium hypophosphite serves as a reducing agent, citric acid serves as a complexing agent, and potassium sulfate acts as a stabilizer. Further, sodium hydroxide and ammonia water can be used as the adjusting agent for adjusting pH.

5, the sintered body having been subjected to the nickel plating step S530 has 92% by weight of nickel (Ni) and 8% by weight of phosphorus (P) in the total plating weight of the surface after nickel electroless plating, By weight. At this time, the sintered body is characterized in that the nickel plating layer has a surface thickness of 20 microns and a surface hardness of HV 560 to 600.

6, the electroless nickel plating step S500 further includes a dry heat treatment step (S540) of drying the nickel-plated sintered body to remove moisture and then performing a heat treatment at a temperature of 350 to 450 ° C Whereby the sintered body can have a surface hardness of 20 microns and a surface hardness of HV 900 to 1000, so that the nickel plating layer has a surface hardness of 20 microns.

As described above, the method of manufacturing a powder metallurgy of a helical gear according to the present invention can provide a helical gear having improved hardness, wear resistance, lubricating property and corrosion resistance so that it can be used as a reduction gear having a small number of revolutions but high compression force.

The embodiments of the present invention described above and shown in the drawings should not be construed as limiting the technical idea of the present invention. The scope of protection of the present invention is limited only by the matters described in the claims, and those skilled in the art will be able to modify the technical idea of the present invention in various forms. Accordingly, such improvements and modifications will fall within the scope of the present invention as long as they are obvious to those skilled in the art.

100: Helical gear
S100: powder mixing step
S200: Powder forming step
S300: Powder sintering step
S400: Postprocessing step S410: High frequency surface hardening step
S420: Barrel step S430: Rust prevention step
S500: Electroless nickel plating step S510: Alkali degreasing step
S520: acid degreasing step S530: nickel plating step
S540: Dry heat treatment step

Claims (12)

A method of manufacturing a powder metallurgy of a helical gear in which a cylindrical gear that transmits rotational motion between two parallel shafts and whose teeth are tilted to one side,
(Mn), 0.3 to 0.5% by weight of silicon (Mn), 0.1 to 0.3% by weight of silicon (Si), 4.5 to 5.5% by weight of nickel, 2.7 to 3.3% by weight of copper, 0.7 to 0.9% by weight of molybdenum, An additive comprising 1.3 to 1.7% by weight of carbon and 0.3 to 0.7% by weight of a lubricant, and a remaining amount of iron (Fe)
A powder molding step of putting the metal powder into a mold having a cavity formed therein and pressurizing the metal powder,
A powder sintering step of applying heat to the powder press-molded in the shape of the helical gear by the mold at a constant temperature for a predetermined time,
A post-treatment step of post-sintering the sintered body in which the powder is sintered,
And an electroless nickel plating step of performing electroless nickel plating on the surface of the sintered body after finishing the electroless nickel plating step.
The method according to claim 1,
Wherein the powder mixing step comprises:
(Ni), 3.0% by weight of copper, 0.8% by weight of molybdenum, 0.4% by weight of manganese, 0.2% by weight of silicon, 1.5% by weight of carbon and 0.5% The additive containing the metal powder and the balance of the remaining amount of iron (Fe) are formed,
In the powder sintering step,
Wherein the lubricant is removed from the additive by heating the powder to a predetermined temperature for a predetermined period of time, and the sintered body from which the lubricant is removed has a content of iron (Fe) as a main ingredient of 89.1 wt% Way.
The method according to claim 1,
The post-
And a high-frequency surface hardening step of hardening the surface of the sintered body by high-frequency induction heating on the surface of the sintered body.
The method according to claim 1,
The post-
A barrel step of removing the sharp edges of the sintered body and polishing for surface gloss,
And a rustproofing step of sealing the pores of the sintered body to coat the rust preventive oil to maintain airtightness or to coat the rust preventive oil.
The method according to claim 1,
Wherein the electroless nickel plating step comprises:
An alkali degreasing step of electrolytically degreasing and washing the sintered body with a weak alkaline agent,
An acid degreasing step of degreasing the sintered body with acidic solution followed by washing with water,
Further comprising a nickel plating step of immersing the sintered body in nickel plating solution, electroless plating, and then washing with water.
6. The method of claim 5,
In the alkaline degreasing step,
The approximately alkali caustic soda (NaOH), sodium carbonate (NA ₂ CO ₃₎ or triphosphate soda (NA ₃ PO ₄₎ at least one using one or more of the mixture by 5 to 15V voltage and 2500 to a current of 3500A is of Wherein the sintered body is electrolytically degreased.
6. The method of claim 5,
In the acid degreasing step,
Wherein the acid is degreased for a predetermined period of time using an acidic solution of hydrochloric acid and sulfuric acid, a surfactant and a corrosion inhibitor.
6. The method of claim 5,
Wherein the nickel plating step comprises:
The sintered body is immersed in the nickel plating solution containing nickel sulfate, sodium hypophosphite, sodium hypophosphite, citric acid and potassium sulfate, and the plating temperature is adjusted to 80 to 100 캜, PH 4 to 6 while the plating time is 10 to 15 minutes, Is electroless plated with nickel.
6. The method of claim 5,
The sintered body,
Wherein the nickel (Ni) is 92 wt% and the phosphorus (P) is 8 wt% in the total weight of the nickel plating layer after nickel electroless plating.
10. The method of claim 9,
The sintered body may further comprise:
Wherein the nickel plating layer has a surface thickness of 20 microns and a surface hardness of HV 560 to 600.
6. The method of claim 5,
Wherein the electroless nickel plating step comprises:
Further comprising a drying heat treatment step of drying the nickel-plated sintered body to remove moisture and then performing heat treatment at a temperature of 350 to 450 ° C.
12. The method of claim 11,
The sintered body may be,
Wherein the nickel plating layer has a surface thickness of 20 microns and a surface hardness of HV 900 to 1000.

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