KR20100067281A - Method for manufacturing head rest stay having high strength and light weight - Google Patents

Abstract

PURPOSE: A manufacturing method of a headrest-stay having high intensity and light weight is provided to be manufactured by environmental-friendly processes without pollution generating. CONSTITUTION: A manufacturing method of a headrest-stay having high intensity and light weight comprises the following steps. A material for a rod or pipe shaped headrest stay is cut(S10). A barrier groove and both ends of the material are processed(S20). The processed material is processed of nitrating-oxidizing thermal treatment(40). A machine-processing is enforced on the surface of the material(S50). The processed material is bent(S30). A oxidizing thermal treatment for growing a color oxide layer is enforced(S60). A resin coating processing is enforced(S70).

Description

Method for Manufacturing Head Rest Stay Having High Strength and Light Weight}

The present invention relates to a method for manufacturing a head rest stay, and more particularly, by applying a nitriding-oxidation (Oxynitrocarburizing) process in place of the conventional hard chromium plating process, high strength and light weight can be produced and excellent corrosion resistance head rest stay It is about a method.

The head restraint for the vehicle supports the head rest for protecting the heads of the driver and passengers from impact and makes it possible to adjust the head rest to a constant height above the seat of the car.

1 is a perspective view of a general head rest stay, Figure 2 is a procedure showing a manufacturing process of a conventional head rest stay.

Specifically, the head rest stay has a diameter of 7 mm to 15mm steel bar or diameter 7mm ~ 15mm, 1mm ~ 3mm thick steel pipe is cut (S10), tapered of the locking groove (1) and both ends (2) (S20), then bent through the bending process After forming the portion (1) (S30), hard chromium plating is performed so that the plating layer thickness is about 10㎛ (S40) to manufacture a product.

Such a conventional head rest stay may use a material having a low strength equivalent to SM 20C for easy processing, which may threaten the safety of the occupant due to bending or damage during a vehicle crash. The use of large diameters solves this safety problem to some extent, but raises the cost and weight of the material.

Hard chromium plating, which is performed for the purpose of improving wear resistance and corrosion resistance, is a chromium metal after plating, so it is not regulated, but hexavalent chromium is generated in the process or during the wastewater treatment, causing air or water pollution. In addition, the process is complicated, such as several washing processes during the process, and even after washing, hexavalent chromium remains on the surface of the product.In particular, since the inside of the pipe is not easy to wash, the remaining hexavalent chromium adversely affects the human body. It is targeted for regulation. In addition, since the color can provide only a single color of silver white, the appearance of the product is monotonous.

Hard chromium plating process using trivalent chromium has been developed to replace such harmful hexavalent chromium. However, trivalent chromium plating has a product quality variation and low corrosion resistance due to instability of the plating solution due to the accumulation of impurities in the plating solution. . In addition, since the color is dark gray, there is no gloss as in hexavalent chromium, and the production cost is 2 to 3 times that of hexavalent chromium plating, commercialization is progressing, but there are various problems in terms of production.

In addition, both hexavalent chromium and trivalent chromium plating have a problem in that hydrogen generated during plating is diffused into the product, thereby preventing the occupant from being damaged by hydrogen embrittlement during a vehicle crash.

As described above, in the conventional manufacturing process of the head rest stay, hexavalent chromium generated during the hard chromium plating process, there is an environmental pollution problem, low strength, there is a fear of damage or warpage caused by hydrogen embrittlement during collision There are problems such as instability of quality.

Therefore, the present invention has been made in view of the problems of the prior art, the object of the present invention is to promote the safety of the occupants in the event of a high-strength and no pollution material discharged during the process is not only environmentally friendly manufacturing process, but also corrosion resistance The present invention provides a method for manufacturing a head rest stay that can enhance aesthetic characteristics by enabling high, light and various colors.

Other objects and advantages of the invention will be described below and will be appreciated by the embodiments of the invention.

In order to achieve the above object, according to the present invention, after (a) cutting the material for the head rest stay of the bar or pipe shape, processing the engaging groove and both ends, (b) step (a) Performing a nitriding-oxidation heat treatment process on the coarse material, (c) performing surface machining on the material undergoing the step (b), and (d) bending the material undergoing the step (c) Provided is a method of manufacturing a high strength and light weight head rest stay comprising the step.

According to the present invention, preferably, after the step (d), further comprising the step of performing an oxidation heat treatment for forming a color oxide layer.

In addition, according to the present invention, preferably, further comprising the step of performing a resin coating process after the step (d).

In addition, according to the present invention, preferably, after the step of performing an oxidative heat treatment for forming the color oxide layer, further comprising the step of performing a resin coating treatment on the material.

Hereinafter, the present invention will be described in detail.

The present invention cuts a steel rod of 7 mm to 15 mm in diameter or a steel pipe having a diameter of 7 mm to 15 mm and a thickness of 1 mm to 3 mm in a predetermined length, and processes the locking grooves and both ends, and performs a nitriding-oxidation heat treatment process.

After that, surface machining such as buffing, polishing, lapping, etc. is performed, followed by bending, resin coating or bending as necessary, and then only oxidizing or oxidizing as necessary. After the treatment consists of a step of performing a resin coating.

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

3 is a flowchart illustrating a method of manufacturing a head rest stay according to the present invention.

Referring to Figure 3, first the present invention diameter 7mm ~ 15 mm steel bar or a steel pipe 7 mm to 15 mm in diameter and 1 mm to 3 mm in thickness is cut to a predetermined length. (S10)

At this time, the surface roughness of the material is not particularly limited, but in consideration of corrosion resistance, glossiness, appearance, etc. of the final product is preferably 2㎛Ra or less.

In this way, the cutting groove 1 for adjusting the height of the head rest stay and the head rest stay are tapered to both ends 2 so that the head rest stay can be easily assembled on the seat.

After that, the nitriding-oxidizing (Oxynitrocarburizing) heat treatment process is performed. (S40) The nitriding-oxidation process is performed for the purpose of improving strength, corrosion resistance, and abrasion resistance, and the process is a nitriding formed by mixing an oxidizing gas with a nitriding atmosphere. It is a thermochemical treatment in which nitrogen, carbon and oxygen diffuse and penetrate simultaneously when oxynitriding and carburizing steel in an oxidizing gas atmosphere.

By the nitriding-oxidation process, a small amount of an oxide layer of Fe ₃ O ₄ and Fe ₂ O ₃ is formed on the outermost surface of the head rest stay. An ε-phase nitride layer or a nitride layer is immediately below the nitride layer. Alternatively, a nitrogen diffusion layer in which nitrogen is diffused and a solid solution is formed under the nitride carbide layer, and then the material having excellent silver-white corrosion resistance can be obtained by removing the oxide layer by surface machining.

The nitriding-oxidation process can replace the hard chromium plating process by forming an ε-phase nitride layer or a nitride layer having high corrosion resistance, and the strength is improved by the nitrogen diffusion layer, so that deformation or breakage of the head rest stay during vehicle collision To prevent the occupant's safety can be secured, and according to this strength improvement there is also an advantage that can be reduced by about 10 to 20%.

In addition, in hard chromium plating, hydrogen atoms generated during the plating process may diffuse to the surface of the steel to cause hydrogen embrittlement, and thus may be damaged even by a small impact. However, in the nitriding-oxidation process, hydrogen embrittlement does not occur, but the strength may be increased.

In the present invention, the nitriding-oxidation heat treatment process means that nitriding and oxidation occur simultaneously in the same furnace, and the nitriding heat treatment process is a heat treatment process including nitriding and nitriding in a broad sense.

The nitriding-oxidation heat treatment may be performed by any heat treatment process including a gas method, a plasma method, a salt bath method, and a vacuum method.

In consideration of high corrosion resistance and high wear resistance, the thickness of a single ε-phase nitride layer is preferably 10 to 30 µm. For this purpose, the nitriding-oxidation treatment temperature is set to 500 ° C to 600 ° C. If the temperature is lower than this, it is difficult to obtain a nitride layer having a sufficient thickness in a short time due to the low growth rate of the compound layer, and if the temperature is higher than this, it is difficult to increase the concentration of nitrogen in the nitride layer to obtain a single ε-phase. to be.

The nitriding-oxidation treatment time is preferably 2 hours to 8 hours, because if the thickness is shorter than this, the nitride layer is thin, and if it is longer than this, the nitride layer may be too thick and peeling may occur.

The head rest stay subjected to the nitriding-oxidation process is then subjected to surface machining such as polishing, buffing, lapping or polishing to remove oxides from the surface and to obtain uniform roughness. Obtain a silver white head rest stay. (S50)

Then, the head rest stay obtained through the surface machining is bent (S30) to complete the product.

By the way, in the conventional manufacturing process shown in FIG. 2, after bending (S30) and hard chromium plating (S40), the reason is, before the bending after the groove and both ends processing (S20), but in a straight form, The bent state (S40) is in the 'c' shape, because this type of hard chromium plating process (S40), it is easy to flow the electricity of the cathode by mounting the product to the jig.

On the other hand, in the present invention, the bent state when mounting the jig of the product for the nitriding-oxidation process takes a lot of space, there is a problem in that the number of products that can be loaded into the furnace is not easy and the surface machining is not easy.

Therefore, when the grooves and both ends are processed and subjected to the bending after the nitriding-oxidation process and the surface machining, a large amount of the product can be heat treated, and the surface machining is easy.

The color of the product manufactured by such a process is silver white, and in the case of requiring various color colors other than silver white, an oxidation treatment for forming a color oxide layer film may be further performed in a subsequent process.

This oxidation treatment heats the silver-white headrest stay subjected to surface machining in a high temperature oxidizing atmosphere to form an iron oxide layer having a thickness of several nm or less on the ε-phase nitride or nitride carbide layer, and is reflected from the surface of the iron oxide layer. The light reflected from the surface of the nitride or nitride layer through the light and the iron oxide layer interfere with each other to express a unique color. The colors are gold, purple, blue and blue depending on the oxidation treatment temperature, time, and oxidation atmosphere. Black and the like. The iron oxide layer is versatile and beautiful in color, and at the same time, it provides excellent corrosion resistance, giving vehicle designers more design choices. In addition, the iron oxide layer fills in the minute cracks generated at the bent portion, and may complement corrosion resistance.

The oxidation treatment conditions are depending on the color to be expressed, the temperature is in the range of 200 ℃ to 400 ℃, the oxidation treatment time is 30 minutes to 4 hours. This is because when the oxidation treatment temperature is lower than 200 ° C., the oxidation treatment is not performed and the desired iron oxide layer cannot be obtained. When the oxidation treatment temperature is higher than 400 ° C., black with low glossiness is expressed.

In addition, when the oxidation treatment time is less than 30 minutes, it is difficult to obtain the desired color oxide layer because the temperature at which the oxide layer is formed is difficult to obtain, and it causes unnecessary time from an economical point of view because the oxidation treatment time is maintained only in black after 4 hours. .

After the resin coating may be further carried out. (S70)

This resin coating is for imparting high gloss, anti-fingerprint and fouling resistance to the head rest stay and improving corrosion resistance. The method is a liquid coating material such as poly-ethylene, poly-urethane, poly-acrylic or poly-alkyd It is applied to the surface of the head rest stay 3㎛ ~ 50㎛ thickness by spraying, dipping or powder coating or electrodeposition of the resin and drying in a temperature range of 30 ℃ ~ 300 ℃, this process As a result, a transparent resin coating layer is formed on the surface of the head rest stay.

As described above, according to the present invention, it is possible to increase the strength compared to the conventional hard chromium plating method to secure the safety of the vehicle occupant and to reduce the weight. In addition, it is possible to produce a variety of colors excellent in corrosion resistance and hard to implement hard chrome plating method can be produced high strength lightweight head rest stays with excellent decoration.

The manufacturing method of the head rest stay of the present invention made as described above provides the following effects.

First, it is possible to provide a high strength and light weight head rest stay without hydrogen embrittlement compared with the prior art.

Second, environmental pollution can be prevented as a pollution-free method different from the conventional hard chromium plating method.

Third, it is possible to implement a variety of colors that can not be expressed by the conventional method can diversify the vehicle interior.

Fourth, when color oxidation treatment and resin coating are performed after the nitriding-oxidation process, it is possible to secure excellent corrosion resistance.

≪ Example 1 >

SM 20C equivalent material was cut into diameter 10mm and length 65cm, and the locking groove and the both ends were processed. This material is made up of a total flow rate of 35 m3 / hr in a pit furnace with a diameter of 1200 mm and a height of 3,000 mm. The composition of gas is 3.5% in an atmosphere of 60% ammonia-4% propane gas-16% air-20% nitrogen by volume. Gas nitriding-oxidation heat treatment was performed, followed by buffing to obtain a silvery white product.

As a result of measuring and comparing the tensile strength of the product according to the present embodiment and the product subjected to the hard chromium plating to the material having the same standard as that of the conventional coating layer under the same conditions, the hard chromium plated product was 39 kgf. / Kg 2, the product of this example is 48 kgf / mm 2, and the tensile strength of this product is 23%.

<Example 2>

The raw material equivalent to SM 20C was cut into a diameter of 10 mm and a length of 65 cm, and processed in the same manner as in Example 1 to produce a product. In this case, the nitriding-oxidation process was performed in the same pit furnace as in Example 1, and the total flow rate was 40 m 3 / hr, and the gas composition was 60% ammonia-2% propane gas-18% air-20% nitrogen in the volume ratio. Gas nitriding-oxidation treatment was performed for a period of time, followed by buffing to obtain a silvery white product.

Then, after bending the product, an oxidation heat treatment for 2 hours in an air atmosphere of 220 ℃ to obtain a product having a golden color. As a result of measuring and comparing the corrosion resistance of the product of this embodiment and the product subjected to the hard chromium plating to a thickness of 10 μm on the same material as in the prior art under the same conditions, the hard chromium plated product appeared after 96 hours. Although there was a rust, the product of this example did not have a call after 250 hours.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

1 is a perspective view of a typical head rest stay,

2 is a procedure showing the manufacturing method of the head rest stay according to the conventional method;

3 is a procedure showing a method of manufacturing a high strength and light weight head rest stay according to the present invention.

Claims (5)

(a) cutting the bar or the head rest stay material of the pipe shape, and then processing the engaging groove and both ends, (b) performing a nitriding-oxidation heat treatment process on the material passed through step (a); (c) performing surface machining on the material which has passed the step (b); and (d) a method of manufacturing a high strength and light weight head rest stay comprising the step of bending the material which has undergone the step (c). The method of claim 1, After the step (d), further comprising the step of performing an oxidative heat treatment for forming a color oxide layer. The method of claim 1, After the step (d), the method of manufacturing a high strength and light weight headrest stay, characterized in that it further comprises the step of performing a resin coating process. 3. The method of claim 2, After the oxidation heat treatment for forming the color oxide layer, the method of manufacturing a high strength and light weight headrest stay further comprising the step of performing a resin coating. The method of claim 1, The nitriding-oxidation heat treatment process of step (b) is carried out in the same furnace to produce nitriding and oxidation at the same time characterized in that the high strength and light weight head rest stay manufacturing method.

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