JP2019147325A - Mold for molding powder slush mold, method for manufacturing mold for powder slush molding, and powder slush molding method using mold for powder slush molding - Google Patents

Abstract

To provide a mold for powder slush molding excellent in durability and heating characteristics, a method for manufacturing the mold, and a powder slush molding method using the mold.SOLUTION: In the mold for powder slush molding used for powder slush molding, its manufacturing method, and the powder slush molding method using the same, the difference between the maximum Vickers hardness and the minimum Vickers hardness in the cross section of the mold for powder slush molding in the thickness direction is set to a value equal to or lower than 30 Hv.SELECTED DRAWING: Figure 3

Description

The present invention relates to a powder slush molding die (hereinafter, sometimes simply referred to as a die), a method for manufacturing the die, and a powder slush molding method using the die.
More specifically, the present invention relates to a powder slush molding die having excellent durability and excellent heating characteristics, a manufacturing method thereof, and a powder slush molding method using the same.

Conventionally, for mass production of large and complex sheet-like materials such as automobile interior materials, sheet-like hot melt derived from powder resin (powder) on the molding surface of a heated mold A powder slush molding method is widely practiced in which the hot melt is cooled and solidified together with a mold and a resin molded product having the same or similar shape to the mold surface is formed.
Such a powder slush molding method uses an electric mold (such as a nickel electric mold) as a mold, heats the mold to a predetermined temperature, and sprays a powder resin onto the product molding surface of the heated mold. A powdering process for forming a predetermined skin, a mold cooling process for cooling the mold together with the predetermined skin to a predetermined temperature, and a demolding process for removing the formed predetermined skin are provided.
Therefore, in order to make the thickness of the sheet-like hot melt derived from the powder resin (powder) uniform, the mold is rapidly heated to a uniform temperature and rapidly cooled to take out the predetermined skin. It is hoped to do.

  Here, as a method for uniformly heating the mold, a provisional heating process and a preliminary heating process controlled to a predetermined temperature are provided to heat the mold to a uniform temperature, and after using the mold, There is a method of forming leather characterized in that it is immersed in and slowly cooled (see, for example, Patent Document 1).

  Further, as another heating method in the powder slush molding method, the slush molding die is a porous die, the opening of the hot air supply duct is brought into contact with the material inlet of the die, and the hot air is blown from the duct There has been proposed a method for heating a slush molding mold characterized by being pumped into a mold (see, for example, Patent Document 2).

Furthermore, a powder slush molding machine provided with a specific mold heating unit, a powder slush unit, and a mold cooling unit has been proposed (see, for example, Patent Document 3).
More specifically, as shown in FIG. 10, the specific mold heating unit is housed in the heating furnace 140 and blows hot air from below the mold 160 in a state attached to the frame 161 to the product molding surface. The 1st hot air blowing part 133 which blows off, the 2nd hot air blowing part 111 which blows a hot air on the outer surface of the metal mold | die 160, and the hot air blown from the 2nd hot air blowing part 111 are guided to the desired location of the outer surface of the metal mold | die 160. And a hot air guide member 113 for heating.

JP-A-3-202329 JP-A-4-191018 JP 2005-28773 A

That is, the heating method disclosed in Patent Document 1 includes a temporary heating step and a preliminary heating step, and it is necessary to control to a predetermined temperature in each step, and temperature control is complicated.
Further, such complicated temperature control is not efficient for heating a large mold at high speed.
Therefore, when the heating method disclosed in Patent Document 1 is applied to the powder slush molding method, if the heating rate exceeds 50 ° C./min or the cooling rate exceeds 50 ° C./min, the mold can be obtained in a short time. There was a problem that cracks due to thermal distortion of the steel were likely to occur.

In addition, in the heating method in the powder slush molding method disclosed in Patent Document 2, hot air is blown out only to the inner surface of the mold to heat it, and in the case of a complex shaped mold, there are places where hot air is difficult to reach. There was a problem in that there was a place where heating was insufficient, and uneven heating was likely to occur.
Therefore, even in the mold disclosed in Patent Document 2, when the heating rate exceeds 50 ° C./min or the cooling rate exceeds 50 ° C./min, it is caused by thermal distortion of the mold in a short time. There was a problem that cracks were easily generated.

Furthermore, according to the heating method in the powder slush molding method disclosed in Patent Document 3, the first hot air blowing portion, the second hot air blowing portion for blowing hot air to the outer surface of the mold, and the frame member are provided. And a hot air guide member for guiding the hot air blown from the second hot air blowing section to a desired location on the outer surface of the mold, so that uniform heating can be performed even on large-sized and complex-shaped molds. It is possible to deposit the powder uniformly and quickly.
However, in recent years, for example, the time until heating to about 250 ° C. or the time until cooling to, for example, about 50 ° C. has been considerably shortened, and the heating rate exceeds 100 ° C./min. When the temperature exceeds 100 ° C./min, the thermal strain generated in the mold is considerably large.
Therefore, even with the heating method in the powder slush molding method disclosed in Patent Document 3, conventionally, the mold has withstood the repeated use of 30000 times or more, but, for example, even in the repeated use of 1000 times or less, the crack The problem that it is easy to occur was seen.

Therefore, as a result of diligent investigations by the inventors of the present invention, the difference between the maximum Vickers hardness and the minimum Vickers hardness in the cross section in the thickness direction of the powder slush molding die is set to a predetermined value or less, for example, heating Even when the rate exceeds 100 ° C./min or the cooling rate exceeds 100 ° C./min, it has been found that cracks can be suppressed during cooling of a powder slush mold, etc. It has been completed.
That is, the present invention reduces the Vickers hardness variation (size difference) in the cross-section in the thickness direction of the powder slush molding die, thereby improving the heating characteristics and the like, and having a high durability. An object of the present invention is to provide a mold, an efficient manufacturing method of such a powder slush molding die, a manufacturing method thereof, and an efficient and economical powder slush molding method using the same.

According to the present invention, a powder slush molding die used for powder slush molding, the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MinHv) in the cross section in the thickness direction of the powder slush molding die. The powder slush molding die is characterized in that the difference (ΔHv = MaxHv−MinHv) is set to a value of 30 Hv or less, and the above-described problems can be solved.
That is, by reducing the size difference as the variation in Vickers hardness in the cross section in the thickness direction of the powder slush molding die, it is possible to provide a powder slush molding die having excellent heating characteristics and high durability. be able to.
More specifically, by controlling the variation in the Vickers hardness to a predetermined difference, the metal crystal structure of the multilayer structure constituting the powder slash molding die is effectively a single layer and a uniform metal. By changing the crystal structure, the heating characteristics and durability can be remarkably improved.

In configuring the powder slush molding die of the present invention, it is preferable to set the maximum Vickers hardness (MaxHv) in the cross section in the thickness direction of the powder slush molding die to a value within the range of 110 to 200 Hv. .
By defining the maximum Vickers hardness of the powder slash molding die in this way, the metal crystal structure of the multilayer structure constituting the powder slash molding die is effectively a single layer and uniformized. It can help to confirm the change to the metal crystal structure.

In configuring the powder slush molding die of the present invention, it is preferable that the minimum Vickers hardness (MinHv) in the cross section in the thickness direction of the powder slush molding die is set to a value in the range of 90 to 160 Hv. .
By defining the minimum Vickers hardness of the powder slash molding die in this way, the metal crystal structure of the multilayer structure constituting the powder slash molding die is effectively a single layer and uniformized. It helps to confirm that the metal crystal structure has been changed.

Further, in configuring the powder slush molding die of the present invention, it is preferable that the surface of the powder slash molding die has a Vickers hardness (AveHv) in a range of 110 to 180 Hv.
In this way, by setting the average value (AveHv) of the Vickers hardness of the surface of the powder slash molding die (product molding surface) to a value within a predetermined range, the metal having a multilayer structure that constitutes the powder slash molding die It helps to confirm that the crystal structure is effectively a single layer and changed to a uniform metal crystal structure.

Further, in configuring the powder slush molding die of the present invention, the surface roughness (Rz: JIS B0601: 1970, ten-point average roughness) of the powder slush molding die is set to a value of 0.1 mm or less. It is preferable.
By controlling the surface roughness (Rz) of the powder slush molding die in this way, a predetermined surface smoothness can be obtained, and as a result, a skin having a uniform thickness and excellent smoothness is powder slush molded. be able to.
In addition, if the surface roughness of the powder slush molding die is below a predetermined value, the metal crystal structure of the multilayer structure constituting the powder slash molding die is effectively a single layer and uniformized. This helps to confirm that the metal crystal structure has changed.

Moreover, in constructing the powder slush molding die of the present invention, it is preferable to set the thickness (average value) within a range of 0.5 to 10 mm.
Thus, by setting the thickness of the powder slush molding die to a value within a predetermined range, a good balance is achieved among the heatability, durability, mechanical strength, economy, etc. of the powder slush molding die. Can be taken.

Another aspect of the present invention is a method for manufacturing a powder slush molding die, which includes at least the following steps (1) to (3). is there.
(1) A step of preparing a powder slush molding die having a predetermined shape (2) A step of heat-treating the prepared powder slash molding die at a temperature of 350 to 600 ° C. for 20 to 180 minutes (3) The difference between the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MinHv) in the cross section in the thickness direction of the powder slush molding die is annealed in the powder slush molding die (ΔHv = MaxHv−MinHv). ) Is set to a value of 30 Hv or less, that is, by performing heat treatment (quenching) or the like under predetermined conditions in order to reduce variation in the Vickers hardness in the cross section in the thickness direction of the powder slush molding die, for example, powder Metals with different crystal structures that make up the slush molds are effectively made into a single layer. It can be a uniform metal crystal structure.
Therefore, it is possible to provide a powder slush molding die that is excellent in heating characteristics and the like and has high durability.

Still another aspect of the present invention is a powder slush molding method using a powder slush molding die, which includes the following steps (1 ′) to (4 ′): It is.
(1 ′) Powder in which the difference (ΔHv = MaxHv−MinHv) between the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MinHv) in the cross section in the thickness direction of the powder slash molding die is 30 Hv or less Step of preparing slush molding die (2 ') Step of heating powder slush molding die to 230 ° C or higher (3') Slush powder resin against product molding surface of powder slush molding die Step of forming and forming a predetermined skin (4 ') Step of cooling the powder slush molding die to a temperature of 50 ° C. or lower, ie, a powder slash molding die having excellent heating characteristics and high durability By carrying out the powder slush method using a mold, a predetermined skin derived from the powder resin can be obtained efficiently and economically. It is possible.

FIG. 1 is a diagram provided for explaining the relationship between the heating temperature (° C.) of a powder slush molding die and various Vickers hardnesses (MaxHv, MinHv, AveHv). FIG. 2 is a diagram for explaining an example of a heating temperature profile of a powder slush molding die. FIG. 3 is a diagram for explaining the relationship between the difference between the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MinHv) (ΔHv = MaxHv−MinHv) and the durability test result (relative value) in the mold. is there. FIGS. 4A to 4C are views used to explain a powder shrush molding method (part 1). Fig.5 (a)-(b) is a figure where it uses in order to demonstrate a powder shrush shaping | molding method (the 2). FIG. 6 is a diagram provided for explaining an example of a powder shrush device based on a side view. FIG. 7 is a diagram provided for explaining an example of a powder shrush apparatus based on a top view. Drawing 8 is a figure offered in order to explain an example of a heating furnace (gas heating furnace) of a powder shrush apparatus. FIG. 9 is a diagram provided for explaining an example of a heating furnace (electric heating furnace) of the powder shrush apparatus. FIG. 10 is a view for explaining a heating furnace of a conventional powder shrush molding mold.

[First Embodiment]
The first embodiment is a powder slush molding die used for powder slush molding, and includes a maximum Vickers hardness (MaxHv) and a minimum Vickers hardness (MinHv) in a cross section in the thickness direction of the powder slush molding die. ) And a difference (ΔHv = MaxHv−MinHv) with a value of 30 Hv or less.
Hereinafter, the embodiment of the powder slush molding die will be specifically described with reference to the drawings as appropriate.

1. Form (1) Basic Form As a basic form of the powder slush molding mold, a powder slash molding mold 60 capable of forming a skin having a predetermined shape as exemplified in FIG. 4A is typical. However, various modifications are possible.
Therefore, as illustrated in FIG. 4A, it may be a powder slush molding mold capable of forming one kind of skin, and although not shown, as a plurality of skins of the same form, for example, two It may be a powder slush mold that can form two skins.
Further, although not shown in the figure, a powder slush molding die capable of simultaneously forming a plurality of different types of skins, for example, two types of skins, may be used.

(2) Material In addition, the constituent material of the powder slush molding mold includes at least one nickel material such as pure nickel, nickel / chromium alloy, nickel / gold alloy, nickel / silver alloy, nickel / copper alloy, stainless steel, and the like. It is preferable to do.
That is, such nickel material is relatively strong against thermal strain and rich in rust prevention, and is therefore suitable as a constituent material for a powder slush molding die.
In particular, pure nickel is a suitable constituent material because it can be easily formed by electroplating as a plating electroforming mold, has high toughness, and is relatively resistant to thermal strain.

(3) Thickness Moreover, it is preferable to make the thickness (average value) of the metal mold for powder slush molding into a value within the range of 0.5 to 10 mm.
This is because when the thickness is less than 0.5 mm, although the heating efficiency and production efficiency are very good, the mechanical strength and durability may be significantly reduced.
On the other hand, when the thickness exceeds 10 mm, although the durability and mechanical strength of the powder slush molding die are improved, the heating efficiency, the cooling characteristics, or the economy may be remarkably lowered.
Therefore, the thickness of the powder slush molding die can be better balanced among these characteristics in consideration of heatability, cooling performance, durability, mechanical strength, economy, etc. Therefore, the value is more preferably in the range of 2 to 8 mm, and further preferably in the range of 4 to 6 mm.

(4) Multilayer structure In addition, when the powder slush molding die is an electroplated plating mold, the crystal structure is basically the same, but due to slight differences in the crystal structure etc., basically the microscope According to the photograph etc., it is formed as a multilayer structure.
Therefore, the thickness per layer gradually increases from the non-product molding surface (B surface) of the powder slush molding die 60 shown in FIG. 4A toward the product molding surface (A surface). Thus, an electroplating casting mold having a multilayer structure in which thermal strain is dispersed in a predetermined direction is preferable.

  For example, in the case of a powder slush molding die having a total thickness of 5.5 mm, the thickness of the first layer is 0 from the non-product molding surface (B surface) toward the product molding surface (A surface). .5 mm ± 0.2 mm, the thickness of the second layer is 0.8 mm ± 0.2 mm, the thickness of the third layer is 0.9 mm ± 0.2 mm, and the thickness of the fourth layer is 1.0 mm ± 0. The thickness of the second layer and the fifth layer is preferably 1.1 mm ± 0.2 mm, and the thickness of the sixth layer is preferably 1.2 mm ± 0.2 mm.

Furthermore, a relatively thin layer, a relatively thick layer, and a thicker layer are basically composed of a plurality of combinations of every three layers, and the relatively thin layer can easily function as a strain absorbing layer. Such an electroplating casting mold of a powder slush molding mold having a multilayer structure is also preferable.
Therefore, in the case of a powder slush molding die having a total thickness of 5.5 mm, the thickness of the first layer is 0 from the non-product molding surface (B surface) toward the product molding surface (A surface). .5 mm ± 0.2 mm, the thickness of the second layer is 0.8 mm ± 0.2 mm, the thickness of the third layer is 1.2 mm ± 0.2 mm, and the thickness of the fourth layer is 0.6 mm ± 0. It is also preferable that the thickness of the second layer and the fifth layer is 1.1 mm ± 0.2 mm, and the thickness of the sixth layer is 1.3 mm ± 0.2 mm.

2. Vickers hardness (1) Maximum Vickers hardness (MaxHv)
The maximum Vickers hardness (MaxHv) in the cross section in the thickness direction of the powder slush molding die is preferably set to a value within the range of 110 to 200 Hv.
The reason for this is that by defining the maximum Vickers hardness (including the rate of change thereof) in this way, the metal crystal structure of the multilayer structure that constitutes the powder slash molding die is caused by a predetermined heat treatment. This is because it can help to confirm that the crystal structure has been changed to a uniform metal crystal structure consisting of a single layer.
More specifically, when the maximum Vickers hardness is less than 110 Hv, the metal crystal structure of the multilayer structure constituting the mold is reduced, but conversely, the mechanical strength, heat resistance, etc. as the mold are significantly reduced. It is because there is a case to do.
On the other hand, when the maximum Vickers hardness exceeds 200 Hv, there are many multi-layered metal crystal structures constituting the mold, the toughness of the mold is significantly reduced, and cracks due to thermal strain occur. It is because it may become easy to do.

That is, as shown by the line B in FIG. 1, it has been found that the maximum Vickers hardness (MaxHv) value in the cross section in the thickness direction changes depending on the heating temperature of the powder slush molding die.
More specifically, FIG. 2 shows an example of a mold temperature profile in heat treatment and annealing. By such heat treatment or the like, a metal crystal structure having a multi-layer structure can be effectively changed from a single layer. It can be changed to a uniform metal crystal structure.

Therefore, as shown in FIG. 3, the difference (ΔHv) between the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MaxHv) in the cross section in the thickness direction of the powder slush molding die is within a predetermined range. By adjusting to, it is possible to change to a uniform metal crystal structure consisting of a single layer, and as a result, good durability can be obtained.
That is, in FIG. 3, the horizontal axis represents the difference between the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MinHv) (ΔHv = MaxHv−MinHv), and the vertical axis represents the durability of the mold. Evaluation points (relative values) are taken.
And the evaluation point (relative value) which shows this durability is the result of evaluation 5 (durability test) described in Example 1 etc. which will be described later, ◎ is 5 points, ○ is 3 points, Δ is 1 point, It is a value obtained by relative evaluation with x as 0 point.

Therefore, if ΔHv is 10 Hv or 20 Hv, a high evaluation score for durability of 5 points is obtained, but as ΔHv increases, the evaluation score for durability decreases rapidly, for example, 50 Hv or more. It is understood that the evaluation score is 0 point.
More specifically, it can be said that by setting ΔHv to a value of 30 Hv or less, three or more evaluation points are obtained, and the durability of the mold is improved accordingly.
Therefore, in order to adjust the value of ΔHv to a desired range, the maximum Vickers hardness (MaxHv) in the cross section in the thickness direction of the powder slush molding die is more preferably set to a value within the range of 120 to 180 Hv. More preferably, the value is in the range of ˜150 Hv.

(2) Minimum Vickers hardness (MaxHv)
Moreover, it is preferable that the minimum Vickers hardness (MinHv) in the cross section in the thickness direction of the powder slush molding die is set to a value within the range of 90 to 160 Hv.
The reason for this is that by defining the minimum Vickers hardness of the powder slush molding die in this way, the metal crystal structure of the multilayer structure constituting the powder slash molding die is effectively a single layer, This is because it can help confirm that the metal crystal structure has been made uniform.
More specifically, when the minimum Vickers hardness is less than 90 Hv, the metal crystal structure of the multilayer structure constituting the mold is reduced, but conversely, the mechanical strength, heat resistance, etc. as the mold are significantly reduced. It is because there is a case to do.
On the other hand, when the minimum Vickers hardness exceeds 160 Hv, there are many multi-layered metal crystal structures constituting the mold, the toughness of the mold is significantly reduced, and cracks due to thermal strain occur. It is because it may become easy to do.

That is, as shown by line C in FIG. 1, it has been found that the value of the maximum Vickers hardness (MinHv) in the cross section in the thickness direction changes depending on the heating temperature of the powder slush molding die.
Therefore, as shown in FIG. 3, the difference (ΔHv) between the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MaxHv) in the cross section in the thickness direction of the powder slush molding die is set to a value within a predetermined range. By adjusting, it is possible to change to a uniform metal crystal structure composed of a single layer, and thus to obtain good durability.
Therefore, the minimum Vickers hardness (MinHv) in the cross section in the thickness direction of the powder slush molding die is more preferably set to a value in the range of 100 to 150 Hv, and more preferably set to a value in the range of 110 to 140 Hv. preferable.

(3) Vickers hardness variation (ΔHv = MaxHv−MinHv)
Further, the difference (ΔHv = MaxHv−MinHv) as a variation of the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MinHv) in the cross section in the thickness direction of the powder slash molding die is set to a value of 30 Hv or less. And
The reason for this is to provide a powder slush molding die that is excellent in durability and excellent in heating characteristics, etc., by reducing the difference in the Vickers hardness variation in the die cross section in the thickness direction. This is because it can.
Therefore, as shown in FIG. 3, the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MaxHv) and the difference (ΔHv) in the cross section in the thickness direction of the powder slush molding die are values within a predetermined range. To a uniform metal crystal structure consisting of a single layer, and thus good durability can be obtained.

However, if the difference in the Vickers hardness variation is excessively small, the yield at the time of mold manufacture may be extremely reduced.
Therefore, the difference as the variation in Vickers hardness is preferably set to a value in the range of 5 to 25 Hv, and more preferably set to a value in the range of 8 to 20 Hv.

That is, by controlling the predetermined difference (ΔHv), variation in Vickers hardness can be controlled. As a result, the metal crystal structure of the multilayer structure constituting the powder slush molding die is effectively a single layer. Thus, it can be confirmed that the metal crystal structure has been made uniform.
Therefore, for example, even if it is used 30,000 times under severe conditions for powder slush molding, it can be heated to a predetermined temperature in a short time, and cracks in the powder slush molding mold can be effectively prevented in the cooling process etc can do.

Although not shown, by setting the predetermined difference (ΔHv) to a value of 30 Hv or less, the thermal conductivity in the thickness direction of the mold is increased by at least 10%, and the heating characteristics of the powder slash molding mold are improved. It has been proved separately.
That is, in the case where the same heating furnace is used, the powder slush molding mold is conventionally heated at a heating rate of, for example, 100 ° C./min. According to the present invention, at a heating rate of 110 ° C./min. Can be heated.

(4) Average value of Vickers hardness (AveHv)
Moreover, it is preferable to make the average value (AveHv) of the Vickers hardness of the surface (product molding surface) of the powder slush molding die within a range of 110 to 180 Hv.
The reason for this is that the average value of the Vickers hardness (for example, the average value of 3 to 10 measurement points) on the surface of the powder slush molding die is set to a value within a predetermined range, and thus the powder slash molding die This is because it can help to confirm that the metal crystal structure of the multilayer structure constituting the mold is actually a single layer and changed to a uniform metal crystal structure.
More specifically, when the average value of the Vickers hardness is less than 110 Hv, the metal crystal structure of the multilayer structure constituting the mold decreases, but conversely, the mechanical strength, heat resistance, etc. as the mold This is because may decrease significantly.
On the other hand, when the average value of the Vickers hardness exceeds 180 Hv, there are many metal crystal structures of a multilayer structure constituting the mold, and the toughness as the mold is remarkably lowered, resulting in thermal strain. This is because cracks are likely to occur.

That is, as shown by line A in FIG. 1, the average value (AveHv) of the Vickers hardness of the surface (product molding surface) of the powder slush molding die is changed depending on the heating temperature of the powder slush molding die. Since it has been found that it varies, the average value is adjusted to a value within a predetermined range in consideration of prevention of cracking.
Therefore, the Vickers hardness of the surface of the powder slush molding die is more preferably set to a value within the range of 120 to 175 Hv, and further preferably set to a value within the range of 125 to 170 Hv.

[Second Embodiment]
2nd Embodiment is a manufacturing method of the metal mold | die for powder slush molding, Comprising: It is a manufacturing method of the metal mold | die for powder slush molding, Comprising: The powder characterized by including the following process (1)-(3) This is a method of manufacturing a slush mold.
(1) A step of preparing a powder slush molding die having a predetermined shape (2) A step of heat-treating the prepared powder slash molding die at a temperature of 350 to 600 ° C. for 20 to 180 minutes (3) The difference between the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MinHv) in the cross section in the thickness direction of the powder slush molding die is annealed (ΔHv = MaxHv−MinHv). ) Is set to a value of 30 Hv or less Hereinafter, a method for producing a powder slush molding die will be described in detail with reference to the drawings as appropriate.

1. Process (1)
Step (1) is a step of preparing a powder slush molding die 60 having a predetermined shape as illustrated in FIG.
Typically, the powder slush molding die is a nickel electroforming mold, and is preferably formed by electroforming from a nickel sulfamate bath or a nickel chloride bath, for example.

2. Process (2)
Next, step (2) is a step of heat-treating the powder slush molding mold prepared in step (1) at a heating temperature of 350 to 600 ° C. under a condition of a heating time of 20 to 180 minutes.
In other words, the metal crystal structure of the multilayer structure constituting the powder slash molding die is effectively changed to a single-layer, uniform metal crystal structure, and the durability and mechanical strength are remarkably improved. Process.

Here, when the heating temperature is less than 350 ° C., it may be difficult to make the metal crystal structure having a multilayer structure a single layer and a uniform metal crystal structure.
On the other hand, if the heating temperature exceeds 600 ° C., the mold surface is swollen or deformed, and the mold surface roughness may be excessively reduced.
Therefore, the heating temperature is preferably set to a value within the range of 400 to 580 ° C, and more preferably set to a value within the range of 430 to 550 ° C.

Further, regarding the heating time, although depending on the heating temperature, if it is less than 20 minutes, it may be difficult to make the metal crystal structure of a multilayer structure into a single layer and a uniform metal crystal structure. Because.
On the other hand, if the heating time exceeds 180 minutes, the mold surface is swollen or deformed, and the surface roughness of the mold may be excessively reduced.
Accordingly, the heating time is influenced by the heating temperature, but is usually preferably a value within the range of 30 to 120 minutes, and more preferably within a range of 45 to 90 minutes.

3. Step (3)
Next, step (3) is a step of annealing the powder slush molding die heated in step (2).
That is, the powder slush molding die heated to a predetermined temperature is left in an air atmosphere (for example, 15 to 40 ° C., 10 to 90% RH), naturally cooled for 20 to 180 minutes, annealed, and heated. This is a step for further suppressing the occurrence of cracks due to strain or the like.

  More specifically, the difference (ΔHv = MaxHv−) between the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MinHv) corresponding to the variation in Vickers hardness in the cross section in the thickness direction of the powder slush molding die. This is a process for adjusting MinHv) to a value of 30 Hv or less.

Here, when the annealing time is less than 20 minutes, it becomes difficult to make the metal crystal structure of the multilayer structure into a single layer and a uniform metal crystal structure, and the difference in the Vickers hardness variation is This is because it may be difficult to adjust the value to 30 Hv or less.
On the other hand, when the annealing time exceeds 180 minutes, on the contrary, it becomes easy to oxidize, the surface roughness of the mold is excessively reduced, and further, the difference as the variation in Vickers hardness is set to a value of 30 Hv or less. This may be difficult.
Accordingly, the annealing time is influenced by the standing temperature, but is usually preferably a value within the range of 30 to 120 minutes, and more preferably within a range of 45 to 90 minutes.

4). Other processes (1) Inspection process 1
The cut surface in the thickness direction of the powder slush molding die is taken out, the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MinHv) are measured, and the difference (ΔHv = MaxHv−MinHv) as a variation is 30Hv or less. It is preferable to include an inspection step for confirming the existence.
The measurement of the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MinHv) on the cut surface in the thickness direction of the powder slash molding die does not necessarily require that the powder slush molding die be inspected for all items, for example, It is sufficient to inspect at a ratio of 1/100 to 1/10.

(2) Inspection process 2
Further, it is preferable to provide an inspection step of taking out a cut surface in the thickness direction of the powder slush molding die and taking an electron micrograph to confirm that the crystal structure is a uniform single layer.
However, it is not always necessary to take out the cut surface of the powder slush molding die and inspect all the products using an electron micrograph. For example, it is sufficient to inspect at a ratio of 1/100 to 1/10.

(3) Inspection process 3
Moreover, it is preferable to measure the Vickers hardness (AveHv) of the surface (product molding surface) of the powder slush molding die and to provide an inspection process that is a value within a predetermined range, for example, a range of 110 to 180 Hv.
The reason for this is that by setting the surface of the powder slush molding die to a value within a predetermined range, the metal crystal structure of the multilayer structure constituting the powder slash molding die is effectively This is because it is a single layer and can help confirm the change to a uniform metal crystal structure.

[Third Embodiment]
The third embodiment is a powder slush method using a powder slush molding die, and includes the following steps (1 ′) to (4 ′).
(1 ′) Powder having a difference (ΔHv = MaxHv−MinHv) of 30 Hv or less as a variation in the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MinHv) in the cross section in the thickness direction of the mold for powder slush molding Step of preparing slush molding die (2 ') Step of heating the prepared powder slash molding die to 230 ° C or higher (3') Powder on the product molding surface of the heated powder slash molding die A step of forming a predetermined skin by slush-molding a body resin (4 ′) a step of cooling a powder slush molding die formed with the predetermined skin to a temperature of 50 ° C. or lower

1. Basic Steps First, the basic steps of the powder slush molding method shown in FIGS. 4A to 4C and FIGS. 5A to 5B are, for example, powder slush molding illustrated in FIGS. This can be done with the device 10.
That is, as a basic process, the above-described steps (1 ′) to (4 ′) are provided, and a predetermined skin 94 derived from the powder resin 92, that is, a sheet that is a solidified product of the thermal melt of the powder resin. In order to make the thickness of the material uniform, it is desirable that the powder slush molding die 60 be rapidly heated to a uniform temperature, and then rapidly cooled to take out the predetermined skin 94 to a predetermined temperature. It is rare.

2. Step (1 ')
More specifically, step (1) in the third embodiment is a step of preparing a powder slush molding die for obtaining a predetermined skin having a desired shape.
And in order to have excellent heating characteristics and to exhibit excellent durability, etc., the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MinHv) in the cross section in the thickness direction of the powder slush molding die The difference (ΔHv = MaxHv−MinHv) indicating variation is set to a value of 30 Hv or less.
In other words, by reducing the difference (ΔHv) indicating the variation in Vickers hardness in the cross section in the thickness direction of the powder slush molding die, it is possible to obtain a powder slush molding die that has excellent heating characteristics and has high durability. It is for providing.

3. Step (2 ')
Next, the prepared powder slush molding die 60 (60D) is prepared using the heating furnace 50 provided in the powder slush molding apparatus 10 (for example, manufactured by Nakata Coating Co., Ltd.) illustrated in FIGS. For example, it is a step of heating in the range of 230 ° C to 300 ° C.
That is, as shown in FIG. 6 (a), the powder slush molding die 60 is moved from the die processing portion (E portion) or the die exchanging portion (D portion) using the conveying device 62. It moves to a mold heating part (A part), and includes the process of heating a powder slush mold (such as a nickel electromold) as a mold heating process.

Here, the heating furnace 50 in the mold heating section (part A) is not particularly limited as long as it can be rapidly heated (heating rate: for example, 100 ° C./min or more). As shown, a gas heating furnace may be used, or an electric heating furnace may be used as shown in FIG.
For example, the gas heating furnace 50 shown in FIG. 8 includes a dome-shaped heating furnace 51 and an elevating device 53, which facilitates taking in and out of the powder slush molding die 60 (60D) and is positioned below. Hot air (W) is blown from the hot air outlet, and the product molding surface of the powder slush molding die 60 (60D) is heated to a predetermined temperature.
In the case of the gas heating furnace 50 shown in FIG. 8, a plurality of far-infrared heater panels 52 are provided on the inner surface of the dome-shaped heating furnace 51, and if necessary, a powder slush molding die 60 (60D). The non-product molding surface is also heated.

In the case of the electric heating furnace shown in FIG. 9A, a plurality of far-infrared heater panels 52 are provided on the inner surface of the semi-cylindrical heating furnace 51, and when energized, a powder slash molding die 60 ( 60D) not only the product molding surface but also the non-product molding surface is heated to a predetermined temperature.
That is, as shown in FIG. 9B, the far-infrared heater panel 52 has a heat-resistant member 52b and a heat-insulating blanket material 54 on the back side, and by applying a predetermined voltage from the electrode 52a, In this configuration, far infrared rays can be intensively emitted in one direction (forward direction) while being mechanically and thermally held by the heat-resistant member 52b.

4). Step (3 ')
Next, in the step (3 ′), the powder heated in the mold heating part (A part) provided in the powder slush molding apparatus 10 (for example, manufactured by Nakata Coating Co., Ltd.) illustrated in FIGS. The slush molding die 60 (60D) is transported to the slash part (B part), and the powder resin is slush-molded on the product molding surface of the powder slush molding die 60 (60C) to form a predetermined skin. It is a process of forming.
That is, as shown in FIG. 6, the heated powder slash molding die 60 (60 </ b> D) is moved to the powder slash portion (B portion) using the transport device 62, and the product molding surface ( This is a step of performing a powdering step (powder resin filling step) in which the powder resin 92 is sprayed onto the A surface) to form the predetermined skin 94.

More specifically, first, as shown in FIG. 4B, the heated powder slush molding die is combined with the fluid immersion furnace 86 in which the powder resin 92 is accommodated in the vertical direction.
Next, as shown in FIG. 4 (c), a clockwise rotation (in the opposite direction to the arrow R1) and a counterclockwise rotation (in the forward direction with the arrow R1) around the central axis (not illustrated) This is a step of repeatedly forming the predetermined skin 94 by slush molding the powder resin 92 on the heated product molding surface (A surface).

As shown in FIG. 4 (a), the hammer 108 is used so that the powder resin is sprayed more uniformly on the product molding surface while the united powder slush molding die is rotating. It is preferable to apply a predetermined vibration by striking the projecting portion of the frame for fixing the powder slush molding die.
When the united powder slush molding die is stopped, as shown in FIG. 5A, the powder resin 92 in a fluidized state is allowed to stand inside the powdering device 88, and the die A predetermined skin 94 having a uniform thickness derived from the powder resin 92 is formed on the product molding surface 60.

5. Step (4 ')
Next, in the step (4 ′), a powder slush molding die 60 (60B) having a predetermined skin is formed by using the cooling device 55 provided in the powder slush molding device 10 illustrated in FIG. This is a step of cooling to a temperature, for example, a temperature of 50 ° C. or lower.

Therefore, the powder slush molding die 60 is moved from the powder slash part (B part) to the cooling part (C part) using a crane or the like as the conveying device 62 shown in FIG. In this step, the powder slush molding die 60 (60B) on which the predetermined skin 94 is formed is cooled to a predetermined temperature.
More specifically, a powder slush molding die 60 formed with a skin 94 having a predetermined thickness, exemplified in FIG. 5A, is used as the cooling device 55 exemplified in FIG. 5B. In the process of cooling the mold temperature rapidly to, for example, 50 ° C. or less (cooling rate: 100 ° C./min or more) together with the skin 94 by using a spray device 98 and a mist device (not shown) alone or in combination. is there.

6). Other Steps Finally, a demolding step (molded product taking out step) is performed in which the formed predetermined skin is separated from the mold and taken out.
That is, the powder slush molding die 60 (60A) is moved to the mold releasing part (E part) using the conveying device 62 shown in FIG. (Product removal process)
Then, after the mold 60 (60A) from which the predetermined skin 94 has been removed is transported again to the heating furnace 50 by the transport device 62, the same process is repeated.

If a crack occurs in the mold 60 (60 ') during the powder slash process, the mold is exchanged to the mold exchanging section (D section) shown in FIG. The mold 60 (60 ') is exchanged.
More specifically, in the mold exchanging part (D part) shown in FIG. 7, the cracked mold 60 (60 ′) is slid using a roller or the like and carried to the standby place 66. Therefore, it is replaced with a new mold 60 (60 ').

[Example 1]
1. Method for Producing Powder Slush Mold (1) Preparatory Step As shown in FIG. 5A, a powder slash mold 60 having a predetermined shape (length: about 2 m, width: about 1.8 m, thickness: 5. 5 mm) was formed as a nickel electric mold made of pure nickel by performing electrolytic nickel plating at least 6 times.

  In addition, a cross-section structure based on elemental analysis using an electron microscope with EDS after cutting a part of the nickel electroforming template created under the same conditions, further etching with ferrous chloride aqueous solution When looking at the inner product molding surface, the thickness of the first layer is 0.5 mm, the thickness of the second layer is 0.8 mm, the thickness of the third layer is 1.2 mm, and the fourth layer The thickness was 0.6 mm, the thickness of the fifth layer was 1.1 mm, and the thickness of the sixth layer was 1.3 mm.

(2) Heat treatment step Subsequently, the obtained powder slush molding die was inserted into a convection type gas heating furnace, and then the temperature was raised from room temperature to 500 ° C. and held at that temperature for 60 minutes.
Next, the powder slush molding die was taken out from the gas heating furnace, allowed to cool naturally, and annealed for at least 30 minutes.

2. Evaluation of powder slush mold (1) Evaluation 1 (cross-sectional SEM photograph observation)
Part of the powder slush molding die after the heat treatment step was cut, and the presence or absence of a multilayer structure was determined from an electron micrograph with EDS.
A: Almost no multilayer structure is confirmed.
○: A remarkable multilayer structure is not confirmed.
Δ: A slight multilayer structure is confirmed.
X: A remarkable multilayer structure is confirmed.

(2) Evaluation 2 (Vickers hardness measurement 1)
The Vickers hardness at the cut surface in the thickness direction of the powder slush mold is measured according to JIS Z 2244: 2009, and the minimum hardness (average value of the lower three points: MinHv) and the maximum hardness (upper The average value of three points: MaxHv) was calculated.
Then, the difference (ΔHv) between the maximum hardness (MaxHv) and the minimum hardness (MinHv) was calculated as variation.

(3) Evaluation 3 (Measurement of Vickers hardness 2)
Furthermore, the Vickers hardness (5 measurement points) on the surface (product molding surface) of the powder slush molding die was measured according to JIS Z 2244: 2009, and the average value (AveHv) was calculated. Subsequently, the average value (AveHv) of the hardness of the product molding surface was evaluated according to the following criteria.
A: AveHv is a value within the range of 130 to 165.
○: AveHv is a value excluding the above range (130 to 165), and is a value within the range of 125 to 173.
(Triangle | delta): AveHv is a value except the said range (125-173), Comprising: It is a value within the range of 120-180.
(Triangle | delta): AveHv is a value except the said range (120-180), Comprising: It is a value within the range of 110-185.

(4) Evaluation 4 (Surface smoothness: Rz)
Furthermore, in accordance with JIS B 0601 (1970), the ten-point average roughness (Rz) on the surface (product molding surface) of the mold for powder slush molding was measured, and the product molding surface was measured according to the following criteria. The surface smoothness was evaluated.
A: Rz is 0.1 mm or less.
○: Rz is 0.5 mm or less.
Δ: Rz is 3.0 mm or less.
X: Rz is more than 3.0 mm.

(5) Evaluation 5 (durability test)
The obtained powder slush molding die is mounted on the powder slush molding apparatus (manufactured by Nakata Coating Co., Ltd.) shown in FIGS. 6 and 7, and powder slush molding (heating rate: 120 ° C./min, cooling rate: 110 ° C.) / Min) was repeated.
Then, the number of times the powder slush was molded until cracks occurred in the powder slush molding die and the powder slush could no longer be used, and the durability was evaluated according to the following criteria.
(Double-circle): It is 30000 times or more.
○: More than 10,000 times.
(Triangle | delta): It is 1000 times or more.
X: Less than 1000 times.

[Example 2]
In Example 2, after the prepared powder slush molding die was inserted into a convection type gas heating furnace, the temperature was raised from room temperature to 400 ° C. and kept at that temperature for 60 minutes. Heat treatment was performed in the same manner as in Example 1 to evaluate durability and the like.

[Example 3]
In Example 3, the prepared powder slush molding die was inserted into a convection type gas heating furnace, then heated from room temperature to 350 ° C., and kept at that temperature for 60 minutes, followed by heat treatment. Heat treatment was performed in the same manner as in Example 1 to evaluate durability and the like.

[Example 4]
In Example 4, the prepared powder slush molding die was inserted into a convection type gas heating furnace, then heated from room temperature to 600 ° C., and kept at that temperature for 60 minutes, followed by heat treatment. Heat treatment was performed in the same manner as in Example 1 to evaluate durability and the like.

[Example 5]
In Example 5, the prepared powder slush molding die was inserted into a nitrogen gas-filled gas electric heating furnace, and then heated from room temperature to 700 ° C. and held at that temperature for 60 minutes for heat treatment. Except for the above, heat treatment was performed in the same manner as in Example 1, and durability and the like were evaluated.

[Comparative Example 1]
In Comparative Example 1, durability and the like were evaluated in a state where the prepared powder slush molding die was electroformed and not subjected to any heat treatment.

[Comparative Example 2]
In Comparative Example 1, the prepared powder slush molding die was inserted into a convection-type gas heating furnace, then heated from room temperature to 250 ° C., and kept at that temperature for 60 minutes. Heat treatment was performed in the same manner as in Example 1 to evaluate durability and the like.

[Comparative Example 3]
In Comparative Example 1, the prepared powder slush molding die was inserted into a convection type gas heating furnace, then heated from room temperature to 300 ° C., and kept at that temperature for 60 minutes, followed by heat treatment. Heat treatment was performed in the same manner as in Example 1 to evaluate durability and the like.

評価１：電子顕微鏡観察
評価２：ΔＨｖ
評価３：ＡｖｅＨｖ
評価４：表面平滑性（Ｒｚ）
評価５：耐久性試験

Evaluation 1: Electron microscope observation evaluation 2: ΔHv
Evaluation 3: AveHv
Evaluation 4: Surface smoothness (Rz)
Evaluation 5: Durability test

As described above in detail, in the case of an electroforming mold that is a mold used for powder slush molding, the product molding side portion is heated to a very high temperature and then cooled. There is a feature that the stretch deformation of the product molding side part is remarkable.
Therefore, by performing a predetermined heat treatment / annealing treatment, a powder slush molding die having a multilayer crystal structure in a cross section in the thickness direction is effectively made into a single layer and a uniform metal crystal. It can be set as the powder slash molding die which consists of a structure.

That is, variation in Vickers hardness can be reduced, and as a result, a mold for powder slush molding that is excellent in heating characteristics and the like, and excellent in durability, and an efficient manufacturing method of such a mold for powder slush molding A production method and an efficient powder slush molding method using the production method can be implemented.
Therefore, even if the structure of the electroforming mold is complicated, the generation of cracks can be effectively prevented, and the harsh heating conditions (for example, the heating rate is 100 ° C./min or more) and the cooling conditions ( For example, even if the cooling rate is 100 ° C./min or more, for example, a powder slush molding die that can withstand 30,000 times or more of powder slush treatment can be obtained.

Therefore, according to the powder slush molding method of the present invention, the durability of the powder slush molding die can be improved and it can be used for a long time.
That is, not only the cost of the powder slush molding die itself can be reduced, but also the time for replacement work can be omitted, and the manufacturing cost of the predetermined skin by the powder slush molding can be suppressed to a considerably low level.

In addition, it seems that the powder slush molding die having a multilayer crystal structure is effectively a single layer and a powder slush molding die having a uniform metal crystal structure. An unexpected effect that the thermal conductivity in the thickness direction is improved by 10% or more can be obtained.
Therefore, even under the same heating temperature and cooling conditions, it is possible to quickly heat or cool to a predetermined temperature.
Therefore, not only the cost of the powder slush molding die itself can be reduced, but also the production efficiency can be increased and the production cost can be kept low.

10: Powder slush molding device 52: Far-infrared heater panel 52a: Electrode 52b: Heat-resistant member 54: Thermal insulation blanket material 55: Cooling device 60: Powder slush molding die 61: Frame 88: Powdering device 92: Powder Resin 94: predetermined skin 98: spray device 108: hammer

[Example 5]
In Example 5, the prepared powder slush molding die was inserted into a nitrogen gas-filled gas heating furnace, then heated from room temperature to 700 ° C., and kept at that temperature for 60 minutes for heat treatment. Were heat-treated in the same manner as in Example 1 to evaluate durability and the like.

Claims (8)

Powder slush molding mold used for powder slush molding,
A powder slush molding die characterized in that a difference between a maximum Vickers hardness and a minimum Vickers hardness in a cross section in the thickness direction of the powder slush molding die is set to a value of 30 Hv or less.   2. The powder slash molding die according to claim 1, wherein a maximum Vickers hardness (MaxHv) in a cross section in the thickness direction of the powder slash molding die is set to a value within a range of 110 to 200 Hv.   3. The powder slash molding die according to claim 1, wherein a minimum Vickers hardness (MinHv) in a cross section in the thickness direction of the powder slash molding die is set to a value within a range of 90 to 160 Hv. .   The powder slash molding die according to any one of claims 1 to 3, wherein the surface of the powder slush molding die has a Vickers hardness (AveHv) in a range of 110 to 180 Hv. .   The powder slush molding die according to any one of claims 1 to 4, wherein the powder slush molding die has a surface roughness (Rz) of 0.1 mm or less.   The thickness is set to a value within the range of 0.5 to 3 mm, and the powder slash molding die according to any one of claims 1 to 5. A method for producing a powder slush molding die, comprising the following steps (1) to (3).
(1) A step of preparing a powder slush molding die having a predetermined shape (2) A step of heat-treating the prepared powder slash molding die at a temperature of 350 to 600 ° C. for 20 to 180 minutes (3) The difference between the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MinHv) in the cross section in the thickness direction of the powder slush molding die is annealed in the powder slush molding die (ΔHv = MaxHv−MinHv). ) To a value of 30 Hv or less A powder slush molding method using a powder slush molding die, comprising the following steps (1 ′) to (4 ′):
(1 ′) Powder in which the difference (ΔHv = MaxHv−MinHv) between the maximum Vickers hardness (MaxHv) and the minimum Vickers hardness (MinHv) in the cross section in the thickness direction of the powder slash molding die is 30 Hv or less Step of preparing slush molding die (2 ′) Step of heating the powder slush molding die to 230 ° C. or higher (3 ′) Powder resin against the product molding surface of the powder slash molding die A step of forming a predetermined skin by slush molding (4 ′) a step of cooling the powder slush molding die to a temperature of 50 ° C. or lower

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