KR100693297B1 - Methods for treating surface of metal - Google Patents

Abstract

The present invention additionally forms a functional metal thin film or metal layer on the surface of a metal product after removing processing defects such as residual stress, abnormal structure, work hardening, and pores generated during metal processing such as cutting or non-cutting. The present invention relates to a surface treatment method for improving durability and wear resistance of the metal product.

The surface enhancement method of a metal product according to the present invention comprises a heat treatment process for improving the constitution of a metal product by removing stress and deformation, and a metal of a different type from the metal product on the surface of the metal product subjected to the heat treatment process. A thin film forming process in which a metal thin film is deposited according to a physical vapor deposition method, and a substitution in which the metal product is heated in a predetermined temperature range so that a part of the metal thin film deposited in the thin film forming process is replaced or penetrated on the surface of the metal product. A carburizing nitriding process in which a nitrogen-based cemented layer is formed on the surface of the metal product which has undergone the permeation process and the substitution / penetration process, and a polishing process is further added after the carburizing and nitriding process as necessary. Can be implemented.

Heat Treatment, PVD, Ion Coating, Carburizing Nitriding, Long Life, Functional Mold, Parts, Ion Plating, Ceramic Diffusion Layer, Cost Reduction, Process Automation, Uniformity, Durability

Description

Method for treating surface of metal

1 is a working process diagram showing a surface treatment method of a metal product according to an embodiment of the present invention.

Figure 2 is a cross-sectional view of the metal product of an embodiment produced according to the surface treatment method of the present invention.

3 is an enlarged photograph of a surface of a metal product according to the conventional surface treatment method and the surface treatment method of the present invention, respectively, enlarged 200 times.

[Description of Drawing Reference]

P10 ... heat treatment process, P20 ... thin film formation process,

20 ... metal thin film, P30 ...

P40 ... carburization nitriding process, 40 ... carbonized layer,

P50 polishing process, W ... metal material.

The present invention is a functional metal thin film on the surface of a metal product after removing the processing defects such as residual stress, abnormal structure, work hardening, internal pores generated during metal processing such as cutting or non-cutting processing by various heat treatment methods Or to form a metal layer further relates to a surface treatment method for improving the durability, heat resistance, wear resistance and the like of a metal product.

Various processing defects appear when the metal material is processed into a metal product having a predetermined shape and dimension according to the intended use.

For example, when a metal material is processed according to a plastic working method such as rolling, forging, extrusion, drawing, pressing, etc., the finished metal product is left with stresses due to processing and work hardening appears. Since such stress (residual stress) and work hardening increase the brittleness of the metal product, the metal product is vulnerable to external shock, and the fatigue resistance and durability are low.

In addition, in a casting method in which a molten metal material is poured into a mold and cooled and solidified, it is hardened from the part in contact with the mold, so that air that has not escaped from the mold forms pores in the metal product or is localized. There is a problem in that the abnormal structure occurs due to the difference in cooling rate and the durability of the metal product falls.

In addition, in the method of removing a part of the metal material, such as mechanical cutting, the surface processing (polishing) with a polishing machine to increase the surface roughness of the metal product, in which case the durability is reduced because stress remains on the polished surface.

On the other hand, since the metal material itself obtained through artificial smelting is in an unstable state, unless it is treated specially, it will gradually corrode over time and change into an oxide, sulfide, hydroxide, carbonate, and the like. For this reason, most metal products are subjected to secondary processing to prevent corrosion and to improve the durability of the product after primary processing related to shape and dimensions.

Examples of the secondary processing (method) include ① a method of plating or painting a corrosion resistant coating on the surface of the metal product, ② a method of hardening the surface of the metal product such as quenching, and ③ a chemical treatment method such as carburizing. However, according to the conventional secondary processing method (surface modification method), the surface characteristics of the metal product are improved, but processing defects in the metal material (material) remain as it is, so that it is difficult to obtain good results.

In addition, in recent years, the coating method through PVD process is used as an effective technique for metal surface treatment, but it is limited to the surface processing of cold forging and cutting tools, etc. Rapid oxidation only adversely affected.

The present invention has been made to improve such a conventional problem, and is a new 2 that is resistant to thermal fatigue or thermal shock, excellent wear resistance and durability, high temperature hardness, and can realize a product surface of various characteristics required by consumers The purpose is to provide a tea processing method.

In addition, the present invention, through the penetration diffusion and heat treatment process, by overcoming the limitation of the ion plating limited to the surface treatment can obtain a ceramic diffusion layer superior to the case by the conventional carburizing method, environmentally friendly, with the advantages of ceramic coating The purpose is to spread the metal processing process in the metal industry, which can be applied to the long life of metal products by adding strong heat resistance.

To this end, in the present invention, the metal product subjected to the secondary processing by heat treatment in various ways to deform the stress and the structure of the metal product, the surface of the metal product so that the surface characteristics required from the consumer can be exhibited The predetermined film is formed in a physical method or a chemical method.

The present invention for solving the technical problem, in the method of treating the surface of the metal product, the heat treatment step for improving the constitution of the metal product by removing the stress and the structure, and the metal on the surface of the metal product subjected to the heat treatment step A thin film forming process in which a metal thin film made of a metal different from the product is deposited according to a physical vapor deposition method, and the metal part of the metal thin film deposited in the thin film forming process is replaced or penetrated on the surface of the metal product. And a carbonaceous nitriding process in which a nitrogen-based cemented layer is formed on the surface of the metal product subjected to the substitution / penetration process and the product is heat-treated at or below the tempering temperature. If necessary, a polishing step of mirroring the surface of the metal product may be carried out before and after each of the above-described steps.

1 is a working process diagram showing a surface treatment method of a metal product according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the metal product of one embodiment manufactured according to the surface treatment method of the present invention. 3 is an enlarged photograph of a conventional surface treatment method and a surface of a metal product according to the surface treatment method of the present invention, respectively, enlarged by 200 times, and the present invention will be described in more detail based on the drawings.

The heat treatment process (P10) for the improvement of the metal product by stress relief and the deformation of the structure should be performed by the surface modification heat treatment and the treatment on the metal material conforming to the surface modification. The above and subsequent surface modification heat treatment may be performed, and any one of the following three heat treatment methods or a combination thereof may be performed for heat treatment for improving the sieving of a metal product.

① Normalizing

In the case of metal products hot-worked by casting, forging, rolling, etc., the cooling rate or solidification rate in each part is different depending on the shape and thickness of the metal product. , Coarsening of grains, etc. When such a structure is heat-treated at an appropriate temperature to form a single phase of austenite, and then air-cooled in the air, the metal structure is improved and the grains are refined between the transformation points. In addition to improving properties, residual stresses are also eliminated.

② Annealing

It is a heat treatment method that softens steel to improve machinability and plastic workability, removes residual stress, controls grains and structures, and removes segregation of elemental elements and impurities by diffusion. In particular, in order to improve the machinability and plasticity of the roughened steel and to increase the toughness after quenching to prevent quenching cracks, it is advantageous to destroy the layered structure of the ferrite beforehand and disperse it as a spherical carbide in the ferrite matrix. For this purpose, spherical immersion cracking treatment is performed.

③ tempering and sub-zero treatment

What seems to be cold working is actually hot working in many cases, so considering the rapid speed of mold work and stainless steel processing after quenching, for example, even the mold used for cold working can be used for hot working. Considering the mold, it is recommended to set the tempering temperature as high as possible.

Therefore, it is preferable to process by quench hardening → sub zero treatment → high temperature tempering method rather than quench hardening → first high temperature tempering → second high temperature tempering method.

Subsequently, after the heat treatment process, a thin film forming process (P20), a substitution / penetration process (P30), and a carburization-nitridation process (P40) are sequentially performed to form various functional metal thin films or metal layers on the surface of the metal product. These processes are described in more detail below.

First, in the thin film forming process (P20) , a metal material (target) containing members of a desired metal thin film is formed in an atomic (evaporation, sublimation, sputtering) state or molecule through a physical vapor deposition apparatus such as an ion plating apparatus or a sputtering apparatus. It is deposited on the surface of the metal product in a state or cluster state and formed into a predetermined metal thin film 20 as shown in FIG. At this time, it is preferable to use ion plating (method). More specifically, in the physical vapor deposition method, the metal particles deposited on the substrate (in the present invention, the metal product subject to secondary processing) are heated by the crucible or the electron beam or the heating of the reactive gas plasma under an inert gas atmosphere. Is generated by In particular, below 1 to 10 ^-2 kPa pressure (average free path of the atmosphere gas molecule, for example, about 0.7 to 70 cm in argon at 25 ° C), which is frequently used in ion plating, until the deposited particles reach the substrate. Molecules, ions, and electrons in the atmosphere gas collide with each other, and not only dozens or thousands of eV ions accelerated, but also ions and neutral particles of various energies, such as ions decelerated by collision and high-speed neutral particles neutralized by accelerated ions It is involved in the formation of a thin film. Sputtering by energy particles of about several hundred eV among the deposited particles related to the thin film formation removes contaminants and oxide films on the surface to clean the substrate and the surface of the thin film. However, in such a physical vapor deposition method, when the high-speed deposition particles become larger than the low-speed deposition particles, the sputtering of the film is more important than the film deposition, so that the desired metal thin film cannot be formed. In addition, if only the ions of an inert gas such as argon (Ar) are irradiated onto the substrate before deposition particles are formed, local overheating occurs on the surface of the metal product and the growth of crystal nuclei is also promoted. Therefore, an ion plating method that can easily obtain a thin metal film with high mechanical strength is preferable.

Substitution and permeation step (P30) performed after the thin film forming step is a metal vapor (hume) permeation treatment of the metal product on which the metal thin film is formed to replace and penetrate a part of the metal thin film on the surface of the metal product and temper ( heat treatment for 6-8 hours below tempering temperature. According to the process, since the bonding force of the metal thin film is greatly increased than the film (plating layer) made by the conventional plating method, it is not easily peeled off, and the durability of the metal product is further improved.

The carburizing nitriding step (P40) is a processing step performed after the substitution / penetration step, in which a carbon atom is diffused to the surface layer portion of the metal thin film to form a carbonized layer 40 on the surface layer portion as shown in FIG. . As will be described more clearly in the following embodiments, the carbide layer 40 plays an important role in improving the durability and long life of the surface-treated metal products.

On the other hand, the polishing process (P50) may be further performed for a mold or a component that requires a mirror surface among the metal products that have been processed above.

Example

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 2 and 3.

In FIG. 2, a predetermined heat treatment is performed on the prepared metal product W, and then a thin metal film 20 having a thickness of about 15 μm is formed by an ion plating method using a titanium-based metal material as a target. Subsequently, nitrogen atoms were diffused into the metal thin film 20 to combine with the metal thin film 20 to form a carbonized layer 40 having a thickness of about 10 μm. At this time, the composition of the carbonization layer is preferably TiN or TiAlN.

The present invention was developed to supply high-performance molds and metal parts that satisfy heat resistance, abrasion resistance, corrosion resistance, high lubrication characteristics, etc. according to industrial development at a low price, and metal products through heat treatment and ion plating processes. Can be achieved and the characteristics of process automation can be satisfied.

In addition, by overcoming the limitation of ion plating limited to the surface treatment by the penetration diffusion and heat treatment processes, a ceramic diffusion layer superior to the conventional carburizing method can be obtained. Therefore, according to the present invention, it is possible to manufacture a metal product having excellent wear resistance and welding resistance, high temperature hardness, and strong resistance to thermal fatigue, thermal shock, or heat loss and hit check.

In addition, the present invention is in the press mold field, which is expanded to the plastic processing increasingly close to the practical use of liquid metal, die casting field including magnesium applied to IT products related to nanotechnology, automobiles requiring high functionality of heat resistance and abrasion resistance It can be widely applied in industrial fields related to metal processing, such as field and machine parts field.

Claims (5)

delete delete delete delete A heat treatment step (P10) for improving the constitution of the metal product by removing the stress and deforming the structure; A thin film forming step (P20) in which a metal thin film made of a metal different from the metal product is deposited by physical vapor deposition on the surface of the metal product which has undergone the heat treatment step; A substitution / penetration process (P30) in which a part of the metal of the metal thin film deposited in the thin film formation step (P20) is substituted and penetrated on the surface of the metal product; A carburizing nitriding step (P40) in which a carbonized layer is formed by diffusion of nitrogen atoms on the surface of the metal product which has undergone the substitution and penetration process (P30); In the surface treatment method of a metal product by the polishing process (P50) performed after the said carburizing nitriding process (P40), The heat treatment step (P10) is selectively performed by any one of soaking, annealing, tempering and sub-zero treatment, The thin film forming process (P20) is deposited by an ion plating method, The substitution and penetration process (P30) is a surface treatment method of a metal product, characterized in that heat treatment for 6 to 8 hours at a temperature below the tempering temperature after the metal vapor substitution infiltration treatment.

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