JP2885087B2 - Extrusion dies having a hard coating with excellent exfoliation resistance, a method for producing the dies, and an extruded aluminum profile with excellent surface properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extruded aluminum die having an excellent durability, which has a bearing surface coated with a boron nitride hard coating excellent in exfoliation resistance, and has excellent durability. About materials.

[0002]

2. Description of the Related Art In order to improve abrasion resistance, a die used for extruding Al, Al alloy or the like has a bearing surface hardened by nitriding. The hard coating peels off from the die substrate with repeated use of the die. For this reason, the nitriding process is performed again after repeated use a predetermined number of times to regenerate the dice. However, as the number of reprocessing increases, chipping or peeling of a white layer or the like adversely affects the quality of the extruded profile occurs on the bearing surface. The white layer is an Fe-N-based compound layer on the outermost surface of the nitride layer, and the original function of the hard film is impaired by peeling of this layer. Therefore, instead of nitriding, PVD, CV
The formation of a hard coating with D or the like has been studied. In particular, since the film formation by PVD, low-temperature CVD, plasma CVD, or the like is performed at a temperature of 600 ° C. or less that does not exceed the transformation temperature of the steel material, it does not adversely affect the material of the die base material. For example, TiN, BN, Si
₃ N ₄ or the like of the ceramic coating ion plating, be applied by CVD or the like, JP 59-1781
22 and JP-A-59-193713. The dies prepared by these methods can be used any number of times without peeling off the fatigued hard thin film and forming a hard thin film by the same method without adversely affecting the die base material and the like.

[0003]

SUMMARY OF THE INVENTION PVD, CVD, etc.
Although effective in terms of repeated use of dies, the adhesion of the formed ceramic coating tends to be insufficient. For this reason, the ceramic coating may peel off from the die substrate during the extrusion, which may adversely affect the surface properties of the extruded product. Further, since the adhesion is poor, the frequency of regenerating the ceramic coating increases, and as a result, the die becomes expensive. PVD typified by ion plating has the advantage that low-temperature processing is possible, but it is difficult to coat the inside of the slit like the bearing surface of an extrusion die.
Although plasma CVD can form a film at a relatively low temperature, the types that can be formed are limited to Ti-based carbonitrides. The present invention has been devised to solve such a problem, and by improving the adhesion of a boron nitride film,
An object of the present invention is to provide an extrusion die having excellent durability and an increased number of times of repeated use, and to provide an aluminum extruded profile extruded by the die and having excellent surface gloss.

[0004]

SUMMARY OF THE INVENTION In order to achieve the object, an extrusion die of the present invention has a bearing surface made of a boron nitride film formed by an ion beam assisted vapor deposition method using a hot tool steel as a base material. It is characterized by being coated. When forming a boron nitride film on the Si _x N _y based intermediate layer, the adhesion of the boron nitride film is further improved. Si _x N _y based intermediate layer is a compound layer between Si and N, a compound Si ₃
N ₄ is the main compound. _x = 1~3, Si x N _y based intermediate layer is in the range of y = 2 to 4, the affinity for boron nitride film formed thereon is good, effectively improving the adhesiveness. Si _x N _y based intermediate layer is not particularly restricted the present invention, in addition to being formed by ion beam assisted deposition method in the same manner as boron nitride film, it can be formed by CVD or ion plating or the like method. However, when considering continuous processing in the same apparatus, it is preferable to form by ion beam assisted deposition.

A boron nitride film has a low frictional force with an aluminum material in an extrusion temperature range, is excellent in oxidation resistance and lubricity, and does not react with the aluminum material. For this reason, the die coated with the boron nitride film has a long-lasting function of producing an extruded material having good surface properties, in combination with the excellent peel resistance. The effect of the boron nitride film becomes more remarkable as the film thickness increases. But,
An excessively thick boron nitride film not only takes a long time to form the film, but also promotes peeling from the die substrate. From this point, it is preferable to form the boron nitride film with a thickness of 0.2 to 3 μm.

The boron nitride film is formed by an ion beam assisted deposition method (Ion Beam Assisted Deposition).
). In the ion beam assisted deposition method, a die substrate is set in a vacuum vessel of 10 ⁻² to 10 ⁻³ Pa, and B is evaporated from metal B by an electron beam. .3 ~
A nitrogen ion beam is generated at an acceleration voltage of 1.0 KV,
The surface of the die substrate is irradiated together with the B vapor. That is,
This is a method in which vacuum deposition with a high film formation rate is used during the ion implantation process, and a compound thin film having different characteristics can be formed on the substrate surface while modifying the surface layer of the substrate.
According to this method, a boron nitride film is formed at a lower temperature than conventional CVD, and a thin film having better adhesion and durability than conventional PVD such as ion plating is formed. Further, since the treatment can be performed at a low temperature, the material of the hot tool steel serving as the die base material is not adversely affected.

[0007] Prior to formation of boron nitride film, the surface of the die base material previously coated with Si _x N _y, differential thermal expansion between the die substrate and the boron nitride film, the internal stress,
Latch mismatch and the like are alleviated. As a result, delamination is suppressed, and the adhesion of the boron nitride film is further improved. Coating of Si _x N _y is the nitrogen gas is ionized by an ion gun, a nitrogen ion beam is generated at an acceleration voltage of 0.5～1.5KV, irradiating the substrate surface with Si vapor. When extruding using a die coated with boron nitride film, pick-up defects, entanglement,
An extruded shape material that can suppress defects such as die lines and has high surface gloss and excellent surface smoothness can be obtained. This is significantly lower than the reactivity or affinity between Al and BN than the reactivity or affinity between Fe and Al of the die substrate in the conventional method. It is presumed that the compound was not formed on the bearing surface. In this respect, in the case of forming a hard film by the conventional nitriding treatment, the extruded aluminum material reacts with the nitride film on the surface of the die base material, and a compound of Fe-Al-Si or the like which induces a defect of the shape material. It is believed that formation is promoted. Further, the surface of the compound layer (Fe-N) formed by the conventional nitriding treatment is oxidized in the extrusion temperature range of 400 to 500 ° C., and changes to Fe ₂ O ₃ , Fe ₃ O _{4, and the} like. The formation of these oxides increases the coefficient of friction and causes peeling of the white layer and deterioration of wear resistance. In contrast,
The boron nitride film formed according to the present invention is not oxidized even in a high temperature range of up to 900 ° C. and maintains a low coefficient of friction. Therefore, a high-quality extruded section having excellent surface gloss and good wear resistance is obtained without wear powder being caught in the extruded section.

[0008]

EXAMPLES hot work tool steel S that tempering the H _RC 48 after heat treatment
Using KD61 as a die substrate, an insert die was prepared. This die is of a split type as shown in FIG. 1A, and fixing screw holes 3 and 4 are formed in each of the die members 1 and 2. When assembling the die members 1 and 2 with fixing screws (shown) inserted into the screw holes 3 and 4, a die having a slit 5 is assembled as shown in FIG. In this embodiment, the slit 5 is set to 40
mm × 3 mm. The cross section of the slit 5 is shown in FIG.
With respect to the extrusion direction indicated by the arrow in (c), the upstream side is the bearing surface 6 and the relief surface 7 is formed on the downstream side. The relief surface 7 has an important effect on the extrudability, the surface properties of the extruded profile, and the like. Therefore, a boron nitride film 8 was formed on the relief surface 7 by ion beam assisted deposition using silicon nitride as a base. Table 1 shows the deposition conditions.

[0009]

[Table 1]

The die on which the boron nitride film was formed was assembled in a 600-ton hot extrusion tester and subjected to an extrusion test under the conditions shown in Table 2. For comparison, an extrusion test was performed under the same conditions using a die having a hard coating formed on the bearing surface by a salt bath nitriding treatment.

[0011]

[Table 2]

[0012] 20 from the profile obtained by extrusion
Samples were taken every m, and the surface properties of the terminal portion were examined for surface roughness, glossiness, and the presence or absence of die lines. The surface roughness was _{measured by} setting _Ra and _Rmax perpendicular to the extrusion direction to the right end,
It was represented by the average value measured at three places at the center and the left end.
The gloss was measured using a digital variable-angle gloss meter at an incident angle of 60 degrees. The presence or absence of the die line was determined by visual observation. The examination of the surface properties was performed after the dies were washed when the cumulative extrusion length reached 100 m, 200 m and 600 m. Figure 2 shows the surface roughness of the extruded profile.
As shown in the figure, the value varied depending on the extrusion length. Surface roughness R
_{The maximum} is about 4 μm in the comparative example in which the hard coating is formed by the salt bath nitriding treatment, whereas it is 2 μm, which is almost half in the embodiment using the die in which the boron nitride film is formed according to the present invention. I have. From this, it was confirmed that the die according to the present invention greatly improved the smoothness of the extruded profile.

The gloss of the extruded profile is improved as the surface roughness decreases, as shown in FIG. That is, while the gloss of the comparative example is about 30%, the example shows a gloss of 40%, which is about 10% higher than this. In FIG. 3, the rise of the glossiness is seen on the way.
4 shows the measurement results of the extruded profile after washing the die. The wear of the dies was investigated by measuring the surface roughness of the bearing surface of the dies before and after extrusion. Also in this case, the integrated extrusion length is 100 m or 200 m.
And at the time of reaching 600 m, the die was washed, and the surface roughness _Ra and _Rmax were measured along the direction perpendicular to the extrusion direction.

FIG. 4 shows the measurement results as the amount of increase in the roughness of the bearing surface. As can be seen from FIG. 4, the average surface roughness _Ra is between the hard film formed by the salt bath nitriding treatment (Comparative Example) and the boron nitride film formed by the ion beam assisted deposition method (Example). There is almost no change in the surface roughness of the bearing surface. However, compared with the maximum surface roughness R _max has clear difference between the two, it is seen that the boron nitride film formed by ion beam assisted deposition method and has a good wear resistance. By coating the bearing surface with a boron nitride film formed by the ion beam assisted vapor deposition, the surface quality of the extruded material is improved and the life of the die is extended.

[0015]

As described above, in the extrusion die of the present invention, the bearing surface is coated with a boron nitride film formed by an ion beam assisted vapor deposition method. This boron nitride film is superior in wear resistance, lubricity and the like as compared with a hard film formed by a conventional method, and improves the surface properties of an extruded product. Further, since the adhesiveness and the durability are superior to those of conventional thin films formed by PVD, CVD or the like, a highly stable product can be obtained for a long period of time.

[Brief description of the drawings]

FIG. 1 is an exploded view of a die having a bearing surface coated with a boron nitride film as viewed from a metal outlet (a), an assembly view as viewed from a metal entrance side (b), and a cross section of a slit (c).

FIG. 2 is a graph showing a state in which the surface roughness of an extruded material varies according to an extruded length.

FIG. 3 is a graph showing a state in which the surface glossiness of an extruded material varies according to an extruded length.

FIG. 4 is a graph showing a state in which the surface roughness of the die bearing surface varies according to the extrusion length.

[Explanation of symbols]

1,2: Die member 3,4: Screw hole for fixing 5:
Slit 6: Bearing surface 7: Relief surface
8: Boron nitride film

Continued on the front page (72) Inventor Toshio Kawai 1-34-1 Kabara, Kambara-cho, Abara-gun, Shizuoka Prefecture Inside Nikkei Giken Co., Ltd. (72) Reiko Takazawa 1-34-1, Kambara-cho, Kambara-cho, Abara-gun, Shizuoka Prefecture (56) References JP-A-59-178122 (JP, A) JP-A-6-79343 (JP, A) JP-A 5-210 (JP, U) (58) Fields investigated (Int.Cl. ⁶ , DB name) B21C 25/02 B21C 25/10

Claims (4)

(57) [Claims] 1. An aluminum extrusion die having a bearing surface coated with a boron nitride film formed by an ion beam assisted vapor deposition method using a hot tool steel as a base material. 2. A hot tool steel as a base material, Si _x N _y based aluminum extruding die which bearing surface with boron nitride film formed through the intermediate layer is coated. 3. Melting metal Si in a crucible by an electron beam in a vacuum vessel of 10 ^-2 to 10 ^-3 Pa and evaporating it as Si vapor, and simultaneously ionizing nitrogen gas by an ion gun in the vacuum vessel. Is generated as a nitrogen ion beam at an acceleration voltage of 0.5 to 1.5 KV, and is vapor-deposited on the surface of the hot tool steel substrate simultaneously with the Si vapor.
After the i _x N _y film is generated as an underlying layer with a thickness of 0.5 to 1 [mu] m, the the electron beam in a vacuum vessel and the molten metal B in the crucible, evaporated as B vapor vacuum chamber at the same time Nitrogen gas is ionized by an ion gun in the inside.
At an acceleration voltage of 3~1.0KV is generated as a nitrogen ion beam, B steam and is simultaneously deposited on the Si _x N _y film, and characterized in that to produce a thickness of 0.2~3μm as BN film The method for producing an aluminum extrusion die according to claim 1 or 2, wherein: 4. An extruded aluminum material extruded by the extrusion die according to claim 1 and having excellent surface gloss with a surface roughness of R _max 4 μm or less and a glossiness of 30% or more.