KR20110137537A - Variable section extrusion molding apparatus - Google Patents

Abstract

PURPOSE: A variable section extruding molding device is provided to enhance the surface roughness and quality of an extruded product. CONSTITUTION: A variable section extruding molding device comprises a container(100), a stem, and variable dies(120). The container comprises an extruding hole. The container comprises a space unit, in which an extruding material(130) is charged. The stem(110) is located behind the container. The stem pressurizes the extruding material charged in the space unit in the container. The variable dies are mounted around the extruding hole of the container. The variable dies change the scale of the section shape of the extruded product. The extruded product is extruded to the shape of the extruding hole of the container by a driving unit.

Description

Variable section extrusion molding apparatus

The present invention relates to a variable cross-section extrusion die apparatus, and particularly, to form a metal nitride film having excellent strength, coefficient of friction, and abrasion resistance on the surface of an area in contact with an extruded material, which can suppress wear and improve surface roughness of an extruded product. A cross-sectional extrusion mold apparatus.

Recently, in various vehicles such as general passenger cars and trucks, the fuel efficiency of the vehicle, the weight reduction of the vehicle body, the durability improvement, or the recyclability are excellent. Therefore, the conventional iron is used as a structural member such as a chassis member, a body member, a bumper material, etc. of the vehicle. Aluminum or aluminum alloy is mainly used instead.

When manufacturing various structural members of a vehicle using aluminum or an aluminum alloy as mentioned above, since the melting point of aluminum which is a raw material is low, extrusion processing is employ | adopted.

In the extrusion process, an extrusion die having an extrusion hole having the same cross-sectional shape as the cross-sectional shape of the constituent member is fixed to the tip of the container, a heated aluminum extruded material (billet) is put into the container, and the billet is pressurized (stem). The extruded product is molded by pressing the die to an extrusion die side and extruding from the extrusion hole.

In addition, in such an extrusion process, since the extrusion hole of the extrusion die has a constant cross-sectional shape, the manufactured extruded product is also molded into a constant cross-sectional shape toward the longitudinal direction.

On the other hand, the production cost of the extrusion die is very cheap compared to the mold used for sheet processing, the production speed is fast, and the material of the closed cross-section used as a structure can be made without bonding work such as welding.

However, in the general extrusion molding method, since the flange having a constant thickness dimension is formed at the upper and lower ends of the web throughout the longitudinal direction in the manufactured extruded product, even if only the length of the web is changed, the cross-sectional secondary moment in the longitudinal direction is large. It is difficult to change the width, and it is necessary to cut off flanges at both ends and flanges that interfere with other members, which is unnecessary when installed in a vehicle body.

In addition, aluminum extruded material has a disadvantage inferior in absolute strength and bondability compared to steel, and tends to reduce the degree of freedom of the manufacturing shape relatively poor formability.

Therefore, it is necessary to develop a low cost economic molding process such as saving the number of processes for molding an extruded material and the development of new molding process technology. In order to solve this problem, when extruded a molding material such as aluminum, a variable cross-section extrusion die has been used that can be formed by freely changing the length dimension of the web, the presence or absence of a flange and its thickness dimension along the longitudinal direction. .

According to the present invention, the metal nitride film formed on the surface in contact with the extruded material increases the surface strength to improve wear resistance, and also improves the surface roughness of the extruded product to improve the quality of the extruded product. The purpose is to provide.

According to an aspect of the present invention, there is provided a mold apparatus for variable cross-section extrusion, in which an extrusion hole is formed and a space portion in which an extrusion material is inserted is formed; A stem positioned at the rear of the container to pressurize the extruded material charged into the space in the container; And a variable die mounted around the extrusion hole of the container and changing the specification of the extruded product which is moved and extruded with respect to the extrusion hole of the container by a driving means. Here, a metal nitride film is formed on the surface of the region in contact with the hot extruded material.

In the present invention, the metal nitride film may be formed on the inner circumferential surface of the extrusion hole of the container or on the inner surface of the variable die, and the metal nitride film may be formed together on the inner circumferential surface of the extrusion hole of the container and the inner surface of the variable die.

In the present invention, the metal nitride film is preferably any one of a titanium nitride (TiN) film, a titanium aluminum nitride (TiAlN) film, a chromium nitride (CrN) film, and a chromium aluminum nitride (CrAlN) film.

In the present invention as described above, the metal nitride film is formed on the surface in contact with the high-temperature extruded material in the mold apparatus for variable cross-section extrusion, and thus the wear resistance of the mold apparatus (that is, the variable die surface and the inner circumferential surface of the extrusion hole of the container) is improved, and The surface roughness of the manufactured extruded product is improved to improve the quality of the extruded product.

1 is a view schematically showing the structure of a variable cross-section extrusion die apparatus.
Figures 2a and 3a is a photograph showing the surface and surface roughness, respectively, of the aluminum extrusion product manufactured using a typical variable cross-section extrusion mold apparatus.
Figures 2b and 3b are photographs showing the surface and surface roughness, respectively, of the aluminum extruded product produced using a variable cross-section extrusion mold apparatus including a variable die with a metal nitride film formed according to the present invention.

Hereinafter, the variable cross-sectional extrusion mold apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a view schematically showing the structure of a variable cross-sectional extrusion mold apparatus according to the present invention, the variable cross-section extrusion mold apparatus according to the present invention is formed with an extrusion hole, the space is formed in which the extrusion material 110 is charged The container 100 and the stem 110 for pressing the extruded material (billet) 110, which is located at the rear of the container 100 and is inserted into the space portion of the container 100, and is mounted around the extruded hole of the container 100. Variable die 120.

The variable die 120 is divided into first and second variable dies, and the first and second variable dies are movable in opposite directions with respect to the extrusion hole of the container 100 by driving means (not shown). To be installed.

The first and second variable dies 120 moving in opposite directions vary the open area of the extruded holes of the container 100, so that the extruded material discharged from the container 100 is controlled by the first and second variable dies ( The cross-sectional area is partially different depending on the degree of movement of 120).

That is, the extruded material discharged through the extruded holes of the container 100 by the pressure by the stem 110 has the same cross-sectional shape A0 as that of the extruded holes of the container 100, but the first and second While passing through the variable die 120, its cross-sectional shape is transformed into the same shape as the shape A between the first and second variable die 120.

Thus, the cross-sectional shape of the extruded material, ie the extruded product, which has passed through the first and second variable dies 120 changes in real time according to the degree of movement of the first and second variable dies 120.

As such, in order to improve the dimensional accuracy of the extruded products having different cross-sectional shapes, maintaining the stable strength of the container 100 and the first and second variable dies 120 in contact with the extruded material 130, the degree of processing of the surface, Wear condition is an important variable.

That is, in the process of discharging the high-temperature extruded material 110 by high pressure, excessive heat and pressure are applied to the container 100, the first and second variable dies 120, and thus, the container 100 and the first. In addition, the strength of the second variable die 120 may not be stably maintained, and wear of the die surface in contact with the extruded material 110 may occur, thereby reducing the degree of processing.

In order to prevent this, in the present invention, the strength, friction coefficient, and abrasion resistance on the inner circumferential surface of the extrusion hole of the container 100 and on the inner surface of the first and second variable dies 120, that is, the surface of each part in contact with the extruded material 110. This excellent metal nitride film was formed.

In the present invention, the titanium nitride, titanium aluminum (TiAl), chromium (Cr), chromium aluminum (CrAl) is nitrided on the inner peripheral surface of the extrusion hole of the container 100 and the surface of the first and second variable die 120 A titanium (TiN) film, a titanium aluminum nitride (TiAlN) film, a chromium nitride (CrN) film, and a chromium aluminum nitride (CrAlN) film were formed.

In the present invention, the physical properties of TiN, TiAlN, CrN, and CrAlN formed in a thin film on the inner circumferential surface of the extrusion hole of the container 100 and the surfaces of the first and second variable dies 120 are shown in Table 1 and the following description.

TiN TiAlN CrN CrAlN Hardness (Hv) 2,000-2,500 2,600-3,000 1,600-2,000 2,500-3,000 Dry friction coefficient 0.7 0.7 0.5 0.6 Wear resistance ○ ○ ○ ○ Low friction △ △ ○ ○ Cost △ △ ○ ○ Heat resistance △ ◎ ○ ◎ Corrosion resistance ○ ○ ◎ ◎ Film thickness (㎛) 2 ~ 3 2 ~ 3 2 ~ 3 2 ~ 3 Coating temperature (℃) 500 or less 500 or less 500 or less 500 or less

◎: very good, ○: excellent, △: normal

nitrification  titanium

Titanium nitride is the most common coating film and has excellent wear resistance and corrosion resistance. In particular, since coating is possible at 500 ° C. or less, there is no dimensional change, and has a film hardness of about 2,000 to 2500 Hv and a dry friction coefficient of 0.7.

Titanium nitride having such a property is used as a material for cutting tools, drawing dies, molding tools and the like.

Titanium Nitride

Titanium aluminum nitride is excellent in oxidation resistance even at a high temperature of 500 ° C. or higher, and is excellent in mechanical properties such as abrasion resistance and impact resistance compared to titanium nitride. Coating is possible below 500 ℃ and has a film hardness of about 2,600 ~ 3,000 Hv.

Chromium nitride

Chromium nitride has high elasticity, excellent adhesion strength, high hardness, and excellent mechanical performance even in harsh environments. Even if the contact area with the material reaches several hundred degrees Celsius, it is excellent in wear resistance and oxidation resistance. Coating is possible below 500 ℃, has a film hardness of about 1,600 ~ 2,000 Hv, dry friction coefficient is 0.5.

Chromium nitride

Chromium nitride is excellent in oxidation resistance at high temperatures and has a low coefficient of friction even at high extrusion rates. Coating is possible below 500 ℃ and has a film hardness of about 2,500 ~ 3,000 Hv.

The titanium nitride film, titanium aluminum nitride film, chromium nitride film and chromium aluminum nitride film having the above physical properties are the object of the present invention, namely, the surface (in contact with the extruded material) of the variable cross-section extrusion mold apparatus in contact with the hot extruded material. It is possible to improve the strength, friction coefficient and wear resistance of the, and also to improve the surface roughness of the extruded product produced through the extrusion process.

Meanwhile, in the above description, the metal nitride film is formed on the inner circumferential surface of the extrusion hole of the container 100 and the inner surfaces of the first and second variable dies 120, but the present invention is not limited thereto. That is, the metal nitride film may be selectively formed on a portion of the region contacting the extruded material 110, for example, the inner circumferential surface of the extrusion hole of the container 100 or the inner surfaces of the first and second variable dies 120.

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

A chromium nitride film was formed on the surface of the variable die (surface in contact with the extrusion material) of the variable cross-section extrusion die apparatus. The conditions for forming the chromium nitride film are shown in Table 2 below.

Chromium Nitride Film Formation Conditions Condition
Coating material

Chrome (Cr)
Base pressure
2 × 10 ^-6 torr
Working pressure
5 × 10 ^-3 torr
(40% argon nitrogen)
Board

Hot Tool Steels (SKD61)
Coating temperature

150 ~ 500 ℃

The chromium nitride film forming process under such conditions is as follows. Meanwhile, the following description has described a process of forming a chromium nitride film, but the process of forming a titanium nitride film, a titanium aluminum nitride film, and a chromium aluminum nitride film is performed in the same process except for the coating material used.

After positioning the variable die of the variable die extrusion die apparatus made of hot tool steel in the chamber, evacuating the inside of the chamber and injecting nitrogen (N ₂ ) gas into the chamber to increase the internal pressure of the chamber from 0.1 mbar to 1,023 mbar. The temperature is increased to be.

Thereafter, the internal pressure of the chamber is evacuated to 0.05 mbar or less and ammonia gas is introduced into the chamber to raise the temperature (450 ° C. to 600 ° C.) such that the internal pressure of the chamber is 50 mbar to 1,000 mbar.

After evacuating, a variable die was introduced into the chamber with ammonia (NH ₃ ), nitrogen (N ₂ ), and other gases (CO ₂ , NO _x, etc.) at a constant composition ratio to maintain the internal pressure at 50 mbar to 1000 mbar. Nitride.

The nitrided variable die is placed in a chamber prepared with a coating material (i.e. chromium) and evacuated inside the chamber to about 10 ^-4 mbar. Thereafter, the inside of the chamber is raised to 400-500 ° C. and argon gas is added to activate the surface of the variable die.

Then, N _{2 at} a pressure of 10 ⁻² to 10 ⁻³ mbar A gas is added and a coating material (chromium) is deposited on the surface of the variable die by physical vapor deposition (PVD) to form a chromium nitride film. Finally, by cooling the inside of the chamber, a high hardness chromium nitride film is formed on the surface of the variable die.

3.58㎛ through the above process A chromium nitride film of thickness is formed on the variable die surface of the variable cross-section extrusion die apparatus.

The extrusion process for aluminum was performed using a variable cross-section extrusion die apparatus including a variable die having a chromium nitride film formed on the surface thereof, and the extrusion process conditions are shown in Table 3 below.

Condition Temperature
(Mold, aluminum extrusion material, container) 450 ℃ Extrusion ratio 30-60

On the other hand, the extrusion process for aluminum in the present embodiment is the same as the extrusion process for general aluminum, and thus a detailed description thereof will be omitted.

The surface image and the roughness of the aluminum extrusion product manufactured through the extrusion process as described above were analyzed, and the analysis results are shown in FIGS. 2B and 3. Meanwhile, FIGS. 2A and 3A show surface image and surface roughness analysis results of an aluminum extruded product manufactured using a general variable cross-section extrusion mold.

Here, a scanning electron microscope (SEM) was used for surface image analysis of the extruded aluminum product, and an atomic force microscopy (AFM) was used for surface roughness analysis.

The surface roughness of the aluminum extruded product manufactured using the general variable cross-sectional extrusion mold apparatus shown in FIGS. 2A and 3A is about 21.193 nm, and the variable cross-section manufactured according to the present embodiment shown in FIGS. 2B and 3B. The surface roughness of the aluminum extruded product manufactured using the extrusion mold apparatus is about 13.830 nm. Thus, aluminum extruded articles made using the present invention have about 35% improved surface roughness.

The foregoing detailed description illustrates the present invention. In addition, the foregoing description shows and describes preferred embodiments of the present invention, and the present invention can be used in various other combinations, modifications, and environments. That is, changes or modifications may be made within the scope of the concept of the invention disclosed in this specification, the scope equivalent to the disclosed contents, and / or the skill or knowledge in the art.

Claims (5)

An extrusion hole is formed and a container in which a space portion into which an extrusion material is charged is formed;
A stem positioned at the rear of the container to pressurize the extruded material charged into the space in the container; And
A variable die mounted around the extrusion hole of the container, the variable die changing the size of the cross-sectional shape of the extruded product extruded with respect to the shape of the extrusion hole of the container by a driving means;
A variable nitride extrusion die apparatus, wherein a metal nitride film is formed on the surface in contact with the extruded material.  The variable cross-section extrusion die apparatus according to claim 1, wherein the metal nitride film is formed on the inner circumferential surface of the extrusion hole of the container.  The variable cross-section extrusion die apparatus according to claim 1, wherein the metal nitride film is formed on an inner surface of the variable die.  The variable cross-section extrusion die apparatus according to claim 1, wherein the metal nitride film is formed on the inner circumferential surface of the extrusion hole of the container and the inner surface of the variable die.  The variable cross-section extrusion die according to claim 1, wherein the metal nitride film is any one of a titanium nitride (TiN) film, titanium aluminum nitride (TiAlN) film, chromium nitride (CrN) film, and chromium aluminum nitride (CrAlN) film. Device.

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