JP2000154026A - Molding die of glass bottle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass molding die coated with a ceramic thin film which has a reduced reactivity with glass and good sliding property with glass. SOLUTION: This molding die for glass bottles is produced by applying a ceramic thin film on the glass molding face of the molding die base. The base body 1 consists of an iron-based metal. The amount of chromium and nitrogen in the ceramic thin film are controlled to 65 to 75 mol% chromium and 35 to 25 mol% nitrogen in the lower layer side, and 52 to 60 mol.% chromium and 48 to 40 mol.% nitrogen in the upper layer side. The amount of chromium increases while the amount of nitrogen decreases to the lower layer side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for molding a glass bottle to be solidified by pouring molten glass into the mold.

[0002]

2. Description of the Related Art Glass bottles are generally formed by pouring molten glass having a high temperature exceeding 1000 ° C. into a mold made of cast iron to solidify and precipitate. In order to prevent cracks due to uneven cooling during the solidification of the glass, the mold is always kept at a high temperature of about 500 ° C., and the operation of “injection → molding → removal” is continuously repeated.

In this operation, the high-temperature glass and the surface of the mold react with each other to cause seizure, and the product may not come off the mold or may be damaged.

In addition, when the product after molding is removed from the mold, rubbing between the product and the mold causes wear of the mold, which significantly impairs the appearance of the product. In order to shorten the tact time of casting, some products require specially conscious roughening of the mold molding surface or marking or printing for design, and damage to the surface appearance due to mold wear is critical to yield. Has a significant effect.

In order to prevent such a phenomenon, a work method of regularly applying a release resin containing lubricating oil, graphite, and sulfur to a molding surface of a mold is generally adopted. The coating operation not only has a safety problem, but also evaporates and scatters during the molding operation, which significantly impairs the working environment of the factory.

[0006] Furthermore, the residue of the lubricant and the release agent is seized on the surface of the mold, significantly impairing the surface condition of the product, and causing a great decrease in the yield of the product.

[0007]

In order to solve these problems, a method of intentionally roughening the surface of an iron alloy having a special composition or forming fine holes to control the cooling effect (Japanese Patent Laid-Open No. 8-109449) Publication). But,
The surface condition changes due to the friction of the mold, and a stable life is not obtained.

[0008] There has also been proposed a method of plating a molding surface with a heat-resistant metal to improve lubricity. However, this method is also not practical because the heat resistance of the plating layer is insufficient and cracks occur during operation at a high temperature, or peeling occurs.

Further, as a similar known technique, there is known a technique of forming a compound of chromium and nitrogen in a glass molding die for an optical element (Japanese Patent Application Laid-Open No. 3-61616). Since this technology has an operating temperature range of 600 ° C or less and is intended for small and high-precision parts, metals with a small expansion coefficient such as cemented carbide and heat-resistant metal can be used as the metal substrate, and no detailed film structure has been studied. Can be implemented. In addition, since it is used for static glass molding of a product having a very smooth surface, the abrasion is originally low, and the requirements for the hardness of the surface layer are relatively moderate.
On the other hand, for molding applications such as beer bottles, there are many restrictions such as the cost for the mold, the operating temperature range, and the abrasion resistance to the molten fluid glass during blow molding, and it was necessary to go through a detailed design of the film composition.

[0010] Accordingly, it is a main object of the present invention to provide a glass molding die coated with a ceramic thin film having low reactivity with glass and good slidability with glass.

[0011]

A mold according to the present invention is a glass bottle molding mold in which a glass molding surface of a mold is coated with a ceramic thin film, wherein the content of chromium and nitrogen in the ceramic thin film is lower. Chromium: 65-75 mol%, Nitrogen: 35-25 mol%, Chromium in the upper layer: 52-60 mol%, Nitrogen: 48-40 mol%, the lower layer has a higher chromium content and nitrogen Characterized by a low content of

Here, the above composition limitation defines the total composition of the ceramic thin film as 100 mol%. The ceramic thin film contains chromium and nitrogen as main components, and the ratio of both elements to the whole thin film is suitably, for example, 90 mol% or more. Therefore, it goes without saying that the ceramic thin film may contain unavoidable impurities such as hydrogen, argon, iron and silicon.

The composition change from the lower layer side (glass molding surface side) to the upper layer side of the ceramic thin film may be continuous or stepwise. In other words, a ceramic thin film having a continuous composition change has a gradient structure in which the chromium and nitrogen contents are sequentially changed so that the chromium content is higher in the lower layer and the nitrogen content is higher in the upper layer. . On the other hand, a ceramic thin film having a stepwise composition change has a laminated structure, and a thin film is formed such that the contents of chromium and nitrogen differ stepwise in each layer. In particular, when the composition change is formed stepwise, it is preferable that the ceramic thin film is formed in a plurality of layers including a lowermost layer, an intermediate layer, and an uppermost layer, and the contents of chromium and nitrogen in each layer are configured as follows.
In this case, the intermediate layer itself includes a plurality of layers.

Lowermost layer: chromium: 70-75 mol%, nitrogen:
30-25 mol% Intermediate layer: Chromium: 60-70 mol%, Nitrogen: 40-30 mol% Top layer: Chromium: 52-60 mol%, Nitrogen: 48-40 mol%

The thickness of the ceramic thin film is suitably 5 to 20 μm. Such a ceramic thin film may be formed by an ion plating method, a PVD (physical vapor phase synthesis) method, or the like.

Examples of the base material of the mold include iron-based materials such as cast iron and soft iron. When a ceramic thin film is formed, it is desirable that the surface of the base material of the mold be polished in advance. The ceramic thin film has a molding surface of a mold substrate,
It is desirable to form it also on the joint surface between the mold components.

Hereinafter, the process leading to the present invention and the reasons for limiting the above-described configuration will be described. Ceramic thin films containing chromium and nitrogen as main elements are chemically stable and are known to have good slidability. The inventors coated this ceramic thin film on the molding surface of the glass bottle molding base material to prevent seizure and adhesion to the glass, greatly eliminating the application of lubricant, which is a source of contamination of the factory environment of products, Research was conducted to reduce the manufacturing cost of glass bottles.

In general, since the mold for glass bottles is large in size and the operating temperature range is extremely wide ranging from room temperature to 1000 ° C. or more, it is easy to manufacture, the cost is low, and cast iron is hard to generate heat distortion. Molds are used. Therefore, first, conditions for coating a thin film that can withstand thermal cycling without causing peeling in a cast iron mold that can be obtained at low cost were examined.

However, a material having a ratio of chromium to nitrogen of 50%, which is generally referred to as chromium nitride, has an extremely low expansion coefficient. Although it could withstand, it could not withstand a thermal cycle with molten glass at around 1000 ° C., and peeling occurred.

Since the molten glass comes into contact with the outermost surface of the thin film of the mold and the bottle is taken out after blow molding at a maximum temperature of about 1000 ° C., the bottle undergoes a thermal cycle in which the temperature is rapidly lowered to about 500 ° C. Therefore, a ceramic thin film with a different composition ratio of chromium and nitrogen was manufactured and compared, and as a result,
A condition for withstanding the above thermal cycle was found.

As the nitrogen ratio is decreased, the expansion coefficient of the compound increases, and 2.5 × 10 ⁻⁶ deg ⁻¹ when the Cr / N ratio is 50/50.
From 70/30 to 9 × 10 ^-6 deg ^-1 , but it was found that as the chromium ratio increased, the hardness decreased rapidly.

Also, cast iron contains a large amount of free carbon as a constituent element, and causes diffusion during film formation and during long-time use at a high temperature, and reacts with a thin film mainly composed of chromium to form a compound. It was also found that peeling easily occurred.

As a result of repeating these tests, the chromium content of the lower layer in direct contact with the cast iron was 65-75.
Mol%, and the upper layer has a lower chromium content
It has been found that a mold having a stable life can be obtained by setting the content to 60 mol%.

When the chromium content of the lower layer exceeds the specified upper limit, the heat resistance becomes insufficient and the heat cycling cannot withstand.
If the value is less than the specified lower limit, the adhesion of the thin film will not be stable, and peeling will occur in a thermal cycle due to the mismatch of expansion coefficients.

When the chromium content of the upper layer is less than the specified lower limit, peeling of the film does not occur, but hardness is insufficient, and wear occurs during use. Conversely, if the value exceeds the specified upper limit, peeling due to thermal cycling occurs due to mismatch of expansion coefficients.

Further, in order to clear the abrasion resistance with the molten glass at the time of use in a high temperature range and blow molding, 5 μm is required.
As described above, a film thickness of 20 μm or less is required. If the film thickness exceeds the specified upper limit, there is a risk of causing cracks in the film due to expansion mismatch, and if it is less than the lower limit, unevenness on the surface cannot be covered, and performance tends to vary.

In a glass mold having a single-layer CrN thin film formed in a thickness of 3 μm as disclosed in Japanese Patent Publication No. 3-61616, a repeated thermal cycle is performed from a high temperature range. Oscillation occurs, causing early film detachment.

On the other hand, as will be described later, the mold having the thin film within the specified range of the present invention does not suffer from the seizure phenomenon even when the continuous operation of 100,000 shots is performed without the operation of applying the lubricant. It was confirmed that the product was obtained.

This thin film not only improves the sliding performance with glass, but also has a remarkable effect of preventing seizure and galling between molds in a manufacturing process in which assembly and opening are repeated at a high temperature. Therefore, by further coating not only the glass molding surface but also the joining surfaces of the mold components, further improvement in productivity can be realized.

[0030]

Embodiments of the present invention will be described below. <Example 1> Various ceramic thin films having different compositions of chromium and nitrogen were formed on the surface of a cast iron substrate using an arc ion plating apparatus, and a wear test was performed on hardness and glass. The thin film is a single layer, its thickness is 10μ
m. Regarding the coefficient of thermal expansion, a rough value was estimated from a bimetal effect by a heating test after coating a thin film of tungsten with a thick film. Table 1 shows the results. In Table 1, the nitrogen content is substantially equal to 100% minus "Cr mol%" (the same applies to the following Example 2). In the "amount of wear with glass", "xx" indicates that severe abrasion to the base material was observed, "x" indicates that the amount of abrasion was large, and "△" indicates the amount of abrasion. Is small, and “○” indicates that almost no wear was observed.

[0031]

[Table 1]

As shown in Table 1, the higher the chromium content, the closer the coefficient of thermal expansion to the value of cast iron. It was found that a lower value was more advantageous.

Example 2 Ceramic thin films having different contents of chromium and nitrogen were laminated on a cast iron base material to a thickness of 5 μm, and the adhesion after coating was evaluated by a diamond indentation indentation test. Although a thin film in which the composition of the thin film continuously changes in the thickness direction was manufactured here, this can be realized by continuously increasing the amount of nitrogen gas to be reacted with chromium. In addition, these samples should be
A heat cycle of 1000 ° C. was applied, the presence or absence of peeling was observed, and the same adhesion was evaluated as described above to confirm stability. Table 2 shows the results. In Table 2, in "Adhesion of thin film" and "Stability to thermal cycle", "x" indicates that film peeling was observed all around the indentation, and "△" indicates that the number was around the indentation. "O" means that film peeling was observed in a part around the indentation, and "◎" means that no film peeling was observed.

[0034]

[Table 2]

As can be seen from Table 2, good results were obtained when the chromium content of the lowermost layer was 65 mol% or more. In particular, those obtained by continuously changing the composition in the thickness direction of the thin film show extremely excellent adhesion.

<Example 3> The surface of a mold base made of cast iron
The layers of the ceramic thin film were laminated. The composition of the lower layer (substrate side) is 70 mol% of chromium and 30 mol% of nitrogen, and that of the upper layer is 55 mol% of chromium and 45 mol% of nitrogen. The total thickness of these two layers was 10 μm. Then, the glass bottle was molded.

As a result, 50,000 without any lubricant application work
When a continuous operation of up to 80,000 shots was performed, the uppermost layer was worn away, and the seizure of the glass occurred, resulting in damage to the mold itself. As a comparative example, when a similar test was performed using a mold having no ceramic thin film, the seizure of the glass occurred in less than 600 shots, and the mold itself was damaged.

<Example 4> The surface of a mold base made of cast iron
The layers of the ceramic thin film were laminated. The composition of the lower layer (substrate side) is a ceramic thin film of chromium 60 mol% and nitrogen 40 mol%.
The upper layer is 55 mol% chromium and 45 mol% nitrogen. The total thickness of these two layers was 10 μm. Then, the glass bottle was molded.

As a result, 50,000 without any lubricant application work
When the continuous operation of shots was performed, fine cracks were generated in the upper layer, and the film was partially peeled. The glass bottles made at that time were also defective.

Example 5 A three-layer ceramic thin film was laminated on the surface of a mold made of cast iron. FIG. 1 shows a sectional view of the configuration. As shown, the lowermost layer 2, the intermediate layer
3. The uppermost layer 4 was formed, and the composition of chromium and nitrogen in each layer was as follows.

Lower layer 2: 75 mol% of chromium, 25 mol% of nitrogen, middle layer 3: 68 mol% of chromium, 32 mol% of nitrogen, uppermost layer
4: 55 mol% of chromium and 45 mol% of nitrogen. The total thickness of these three layers was 10 μm. Then, the glass bottle was molded.

As a result, continuous operation of 100,000 shots was possible without applying lubricant. In addition, the surface condition of the resulting glass bottle was extremely clean, and defective scratches were significantly reduced.

[0043]

As described above, the use of the mold of the present invention eliminates the need for a lubricant application operation, not only keeps the factory environment clean, but also causes sticking of residue to the mold and products. Therefore, continuous operation over a long period of time is possible, and the appearance defect of the product can be reduced. As a result, the manufacturing cost of the glass bottle can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a laminated structure of a ceramic thin film formed on a molding surface of a mold.

[Explanation of symbols]

 1 base material 2 bottom layer 3 middle layer 4 top layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mikio Ueda 1351-1 Imaiza, Himeji-shi Amahi Beer Pax Co., Ltd. (72) Inventor Nakanishi Tetsuo 1351-1 Imaiza, Himeji-shi Shima, Himeji Inside Beer Packs (72) Inventor Takaya Ishii 575 Kuzedonojo-cho, Minami-ku, Kyoto, Japan Inside IT F Co., Ltd. (72) Inventor Norio Asagi 575 Kuzedonojo-cho, Minami-ku, Kyoto, Japan F term in TF Corporation (reference) 4G015 HA01 4K029 AA02 AA26 BA58 BB02 BC02 BD05 CA01 CA03

Claims (3)

[Claims] 1. A glass bottle molding mold in which a glass molding surface of a mold substrate is coated with a ceramic thin film, wherein the content of chromium and nitrogen in the ceramic thin film is 65 to 75 mol% of chromium on the lower layer side. Nitrogen: 35 to 25 mol%, chromium on the upper layer side: 52 to 60 mol%, nitrogen: 48 to
A glass bottle molding die, characterized in that the lower layer has a higher chromium content and a lower nitrogen content. 2. The method according to claim 1, wherein the ceramic thin film is formed in a plurality of layers including a lowermost layer, an intermediate layer, and an uppermost layer, and the contents of chromium and nitrogen in each layer are configured stepwise as follows. Item 7. The glass bottle molding die according to Item 1. Bottom layer: Chromium: 70-75 mol%, Nitrogen: 30-25 mol% Intermediate layer: Chromium: 60-70 mol%, Nitrogen: 40-30 mol% Top layer: Chromium: 52-60 mol%, Nitrogen: 48 ~ 40 mol% 3. The glass bottle molding die according to claim 1, wherein the thickness of the ceramic thin film is 5 to 20 μm.