KR20090120919A - Method of increasing service life of press tools - Google Patents

Abstract

PURPOSE: A method for lifetime of press die improvement is provided to produce the press die including excellent abrasion resistance and easy workability by using nano structure cermet coating material having easy workability and excellent abrasion resistance. CONSTITUTION: The abrasion resistant coating is performed on the press die surface by applying a spraying coating process. The nano structure cermet coating material is performed for obtaining excellent abrasion resistance and easy workability. The ceramic particle size is fined into the nano structure cermet coating material less than 1 micrometer. The coating material is the tungsten carbide-cobalt(WC-Co) coating material. The nano structure cermet coating material includes the micro-structure(4) like being combined with the metal after the micron-size ceramics is pulverized.

Description

How to improve the service life of press molds {Method of Increasing Service Life of Press Tools}

The present invention relates to a method for improving the durability life of a press die, and more particularly, in the method of forming a coating layer by spray coating on the surface of a press die, a coating layer formed on the surface of a press die by applying a nanostructured cermet-based coating material. The invention relates to a method for improving the service life of a press die for facilitating polishing and improving wear resistance during press forming of thin metal.

Press mold is a mold that uses a thin metal as a material to form and process a large amount of products of the same standard in a shape required by plastic deformation, etc., without sticking. Press mold technology is an industry-based technology that is currently being used in many fields such as automobiles, electric and electronic communication devices, precision machines, aircraft parts, office equipment, building materials, and is widely used for producing various parts of the automobile industry.

Currently, large and medium press molds for the production of domestic automotive parts are mostly made of casting materials in order to reduce manufacturing costs and shorten manufacturing periods, and press molds made of such casting materials are made of mold steel (cast steel). There is a problem of inferior durability.

Hard chromium plating technology is applied as a surface treatment method for press molds to compensate for such durability problems, but hard chrome plating technology is gradually limited in application due to the global environmental regulations, and the processing cost is increased. There is a trend that there is a problem that does not meet the required mold life due to the relatively low durability performance compared to other surface treatment methods.

In particular, the die bead and punch R-shape areas, which are the main stress / wear concentration areas of the press die, are frequently damaged due to the low wear resistance of chromium plating. Frequent maintenance of the mold increases the cost of repairs as well as disrupts the production of the product.

Therefore, the domestic automotive industry is in urgent need for a new high performance clean surface treatment method that can solve the low life and environmental problems of the press mold with the existing hard chrome plating technology.

In general mold, surface treatment methods for improving durability life include physical vapor deposition (PVD), chemical vapor deposition (CVD), ion implantation, and TD coating (Toyota Diffusion). Various methods are applied. However, they all have great limitations in terms of equipment and cost in application to medium and large press molds for automobiles weighing several tens of tons due to the process characteristics of inserting a mold into a chamber.

In order to overcome such a problem, the application of thermal spraying may be considered as a surface treatment method for improving durability of medium and large press dies. The thermal spray coating technology is a technique of forming a coating layer in which a powder or wire-shaped material is heated from a high temperature heat source such as a flame or a plasma to be melted into liquid droplets, accelerated to a substrate at high speed, and then rapidly cooled and solidified and laminated. The thermal spray coating technology has almost no limitation on the shape and size of the base metal (mold), can be installed on site, and various materials can be used to optimize the coating characteristics according to the use environment, and to improve productivity compared to other surface treatment processes. It is a technology that is applied to improve the durability life of various industrial machinery parts and facilities as an eco-friendly surface treatment technology with the advantage of being very high.

Despite these advantages, however, current thermal spray coating technology is rarely applied as a method for improving the service life of molds except for some simple shaped extrusion die parts. This is due to the disadvantage that the surface roughness of the thermal spray coating material is about 10㎛ large after the spray coating process must be performed after a high level of skill and experience.

In other words, after the anti-wear coating technology, the thermal spray coating material must be manually processed after the anti-wear coating. The thermal spray coating material having excellent wear resistance is polished to the high dimensional accuracy and surface properties (roughness) level required by the mold. It requires a lot of manpower and time to process, and unlike the various equipment parts such as rolls and screws, which use the conventional anti-wear spray coating technology, the press mold has a very complex surface shape, which is very problematic. It gets serious.

Therefore, in the method of improving the service life of medium and large press dies, the thermal spray coating technology solves the environmental problems of the conventional hard chromium plating methods, low durability performance problems, and size constraints of other surface treatment technologies such as vapor deposition. However, in order for the spray coating technology to be commercially applied to the medium-large press mold, a method for facilitating post processing is required. However, in the related art, there is a lack of preparation for a method for facilitating post-processing of the thermal spray coating material.

The present invention has been proposed to solve the above problems, a method for improving the endurance life of the press die by using a nanostructured cermet-based coating material that is easy to process and excellent wear resistance for the application of the press mold of the thermal spray coating technology To provide that purpose.

In order to solve the above problems, the press die durability improvement method of the present invention is a wear-resistant coating on the surface of the press mold by applying a spray coating method for forming a coating material by heating and accelerating a powder or wire-shaped material with a heat source such as a flame In the process of performing, the thermal spray coating method is characterized in that it is carried out using a nano-structure cermet-based coating material for the simultaneous acquisition of properties that are opposed to each other, such as excellent wear resistance and easy processability.

At this time, it is preferable that the nanostructured cermet-based coating material has a micronized ceramic particle size of 1 micrometer or less.

At this time, the cermet-based coating material may be a tungsten carbide-cobalt (WC-Co) coating material.

As described above, according to the method for improving the service life of the press die by using the nanostructured cermet-based coating material of the present invention, the press die having simultaneously opposed properties such as excellent wear resistance and easy workability Can be prepared.

In addition, by solving the problems with the conventional technology, it is possible to manufacture a press die which is environmentally friendly and is not restricted by the size and shape of the mold and at the same time economically improved durability.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed contents may be thorough and complete, and the technical spirit of the present invention may be sufficiently delivered to those skilled in the art.

Cermet coating material is a representative wear-resistant spray coating that is mainly applied to parts equipment requiring abrasion resistance. The cermet-based coating material is a composite material having a microstructure in which high-hardness ceramic particles are distributed in a metal matrix, such as tungsten carbide-cobalt (WC-Co) -based coating material.

Cermet-based coating materials such as tungsten carbide-cobalt (WC-Co) commonly used in the thermal spray coating process have a size of several to several tens of micrometers of the ceramic particles which are curable phases, but in the present invention, the size of the ceramic particles is 1 micron as the coating material. Nanostructured cermet-based materials refined to less than a meter are used.

Nanostructured cermet-based spray coatings exhibit different wear behaviors depending on the hardness of the wear counterpart. In other words, when the nano-structured cermet-based sprayed coating is worn by a relatively high hardness, the wear resistance is significantly lower than that of the conventional micron-structured coating. .

Figure 1 is a schematic diagram showing the structure of the micron and nano-structure cermet-based coating material in order to compare the processability of the thermal spray coating material with a high hardness abrasive.

Figure 1 (a) shows the structure of the micro-structure cermet-based coating material used as a conventional thermal spray coating material, Figure 1 (b) shows the structure of the nano-structure cermet-based coating material applied to the method of the present invention will be.

As shown in (a) of FIG. 1, the micron-structured cermet-based coating material is composed of ceramic cured particles 2 having a size of several to several tens of micrometers, and the ceramic cured particles 2 are abrasive abrasives. It hinders the progress of (3) and has high abrasion resistance. In this case, the relatively soft metal base (1) is selectively worn first, and as a result, the bonding force between the ceramic curable particles (2) and the metal base (1) is lowered so that the ceramic curable particles (2) are dropped. Wear progresses. Therefore, in terms of the polishing process, when using the micro-structured cermet-based coating material, it is very difficult to polish and there is a problem that many surface defects are generated after polishing.

On the other hand, nanostructured cermet-based coating material, as shown in (b) of FIG. 1, because it has a microstructure (4) as if the micron-size ceramic cured particles are finely pulverized and bonded to a metal material, so that the high hardness abrasive ( 3) A wear mechanism in the form of grinding the metal matrix directly. Therefore, the polishing is very easy and the surface defect does not occur after polishing, the quality of the polishing surface is also very high. By applying the nano-structured cermet-based material in this way it is possible to ensure the easy processability required when applying the press mold of the thermal spray coating technology.

On the other hand, since the thin metal plate used in the pressing process is generally lower in hardness than the nanostructured cermet-based coating material, the wear mechanism of the form shown in FIG. 1 does not work in the pressing process of forming a product using the finally produced press mold. Do not. The nanostructured cermet-based coating material has excellent wear resistance when compared with a relatively low hardness counterpart. In the case of nanostructured cermet-based coating material, the bonding strength with the metal matrix is improved due to the decrease of grain size and surface area of the ceramic cured phase, and the impact resistance characteristics of the coating material due to the reduction of the mean dislocation distance between the cured phases. Because it is improved.

At this time, the nano-structure cermet-based coating material is fine to the ceramic particle size of less than 1 micrometer, it is preferable to improve the workability during polishing after spray coating, wear resistance during the pressing process.

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

EXAMPLE

A tungsten carbide-cobalt (WC-Co) coating material, which is a typical cermet-based material that is used as a typical thermal spray coating material for parts equipment requiring abrasion resistance, was thermally coated on the surface of a press mold to form a coating layer. In this way, the coating layer formed on the surface of the press die was polished with a wear counterpart to confirm the difference in abrasion resistance of the micron- and nano-structure cermet-based coating materials according to the hardness of the wear counterpart. SUGA test (ASTM standard D6037) The test (ASTM standard G65) was performed. SUGA abrasion test is a wear test method using silicon carbide (SiC) having a hardness of 2500 ~ 2800Hv higher than the hardness of the coating material (1200 ~ 1500Hv), and dry sand abrasion test is a hardness test of the coating material (1200 ~ 1500Hv). Abrasion test method using silicon dioxide (SiO ₂ ), which has a hardness of 700 ~ 1000Hv lower than).

The results of measuring the amount of wear carried out as described above are shown in Table 1 below.

TABLE 1

Figure 2 is a graph showing the results measured and carried out as described above to compare the wear characteristics according to the wear counterpart hardness of the micron and nanostructured cermet-based coating material.

As shown in (a) of FIG. 2, the wear amount of the nanostructured cermet-based coating material when the silicon carbide (SiC) having a hardness higher than that of the thermal spray coating material is used as a wear counterpart is 30 (mg) and the micron structure It was more than three times larger than the amount of abrasion (8 mg) of the mat-based coating material. This is a result showing that the nanostructured cermet-based coating has easier polishing processability than that of the micron-structured cermet-based coating.

In addition, as shown in (b) of FIG. 2, the wear amount of the nanostructured cermet-based coating material when the silicon dioxide (SiO ₂ ) having a hardness lower than that of the thermal spray coating material is used as a wear counterpart is 36 (mg) to a micron. It was found to be 70% of the amount of wear of the structural cermet-based coating material (51 mg). This result shows that the press mold manufactured using the nanostructured cermet-based coating material in the metal sheet forming process of the press die may have better wear resistance than the press mold manufactured using the micronized cermet-based coating material. .

Therefore, the method of improving the service life of the press die of the present invention is a method of paying attention to the change in wear mechanism according to the wear counterpart hardness of the nanostructured cermet-based sprayed coating material, which is applied to the press mold during the post-processing process using a high hardness abrasive material. In the press molding process using a conventional micron-structured cermet-based spray coating material, it is possible to perform a very easy process compared to the case of post-processing and at the same time press molding process of sheet metal with a relatively low hardness compared to the nano-structured cermet-based coating material. In the case of the press mold manufactured using a conventional micron structure cermet-based coating material will be able to secure excellent wear resistance.

Figure 1 is a schematic diagram showing the structure of the micron and nanostructured cermet-based coating in order to explain the processability of the thermal spray coating material by the abrasive.

Figure 2 is a graph for comparing the wear characteristics according to the wear counterpart hardness of the micron and nano-structure cermet-based coating material.

Claims (3)

In the process of applying a spray-resistant coating method to the surface of the press die by applying a spray coating method of heating and accelerating a powder or wire-like material with a heat source such as a flame to form a coating material, The spray coating method is a method for improving the durability life of the press die, characterized in that it is carried out using a nano-structured cermet-based coating material for the simultaneous securing of properties, such as excellent wear resistance and easy processability. The method according to claim 1, The nanostructured cermet-based coating material is a method of improving the durability life of the press die, characterized in that the ceramic particles are micronized to less than 1 micrometer. The method according to claim 1, The coating material is a tungsten carbide-cobalt (WC-Co) coating material characterized in that the durability life of the press die.

Images