JP2007216252A - Method for cooling die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for cooling a die by which, during the operation of a die, the occurrence of rust as the starting point of cracks to water-cooled holes in which stress caused by thermal fatigue is generated is suppressed, thereby the life of the die can be improved. <P>SOLUTION: In the method for cooling the die, a rust preventive is added to cooling water for cooling the die to prepare alkaline cooling water of a pH of ≥9, the cooling water passing the water-cooled holes penetrated through the inside of the die, and thereafter, the alkaline cooling water is circulated through the water-cooled holes of the die. At this time, as the rust preventive, the rust preventive containing amine is preferable. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a mold cooling method, and more particularly to a mold cooling method suitably used for manufacturing a die-cast product or a forged product.

  Conventionally, molds such as die casting molds and forging molds are provided with water cooling holes inside the mold when molten metal or the like is poured into the mold and then molded to produce die castings or forgings. The temperature of the mold is adjusted by circulating cooling water such as industrial water through a pipe connected to the water cooling hole.

  If rust is generated in the water cooling hole of this mold, it will lead to clogging of pipes and failure of the temperature control device connected to this mold. Therefore, when this mold is removed from the molding apparatus and left (stored), it is usually The rust preventive agent is applied to the mold to prevent the occurrence of rust.

  For example, in Patent Document 1, in an injection mold, compressed air is introduced through a pipe after the molding operation is completed, water remaining in the pipe and the water cooling hole is removed, and the mold is closer to the mold than the position where the compressed air is introduced. Using a device in which a nozzle for dropping the rust preventive agent is attached to the pipe portion, the rust preventive agent is sprayed into the pipe and the water cooling hole. As a result, the water cooling holes of the mold are coated with a rust preventive agent, and the mold is left (stored) in this state, so that the generation of rust can be prevented during the period of storage (storage).

Japanese Utility Model Publication No. 07-40124

  However, such as the method disclosed in Patent Document 1, conventionally, when the mold is left (stored), the process of suppressing the generation of rust has been performed, but the occurrence of rust in the water-cooled holes during the actual operation of the mold. An effective prevention method has not been proposed.

  During the actual operation, since the mold is at a high temperature, the water cooling holes are also exposed to a high temperature, and stress due to thermal fatigue is generated in the water cooling holes. Under such circumstances, when rust is generated in the water cooling holes of the mold due to long-time operation and the corrosion proceeds, the corroded portion becomes a starting point of the crack, and the mold is damaged by the stress corrosion cracking. As a result, there is a problem of shortening the mold life.

  The problem to be solved by the present invention is to suppress the occurrence of rust, which is the starting point of cracks in water-cooled holes where stress due to thermal fatigue occurs during the operation of the mold, thereby improving the life of the mold. An object of the present invention is to provide a mold cooling method that can be used.

  In order to solve the above-described problems, a mold cooling method according to the present invention includes a cooling water for cooling the mold that circulates in a water-cooled hole penetrating through a mold such as a die-cast mold or a forged mold. The gist is that after adding a rust preventive agent to adjust the alkalinity to pH 9 or higher, the alkaline cooling water is circulated through the water cooling holes of the mold.

  In this case, it is preferable to add an rust-preventing agent containing amine to the cooling water to adjust it to an alkaline pH of 9 or higher, and then circulate the alkaline cooling water through the water cooling holes of the mold.

  According to the mold cooling method of the present invention, during the operation of the mold, the alkaline cooling water adjusted to an alkaline pH of 9 or more by adding a rust inhibitor to the cooling water for cooling the mold. Since it distribute | circulates to the water cooling hole of a metal mold | die, generation | occurrence | production of the rust used as the starting point of the crack to the water cooling hole can be suppressed, and, thereby, the lifetime of a metal mold | die can be improved.

  In this case, after adding an amine-containing rust preventive agent to the cooling water to adjust the alkalinity to pH 9 or higher, if this alkaline cooling water is circulated through the water cooling holes of the mold, the rust in the water cooling holes is surely obtained. Can be suppressed.

  Hereinafter, an embodiment of the present invention will be described in detail.

  The mold cooling method according to the present invention is to adjust the pH of the cooling water to 9 or more by adding a rust inhibitor to the cooling water flowing through the water cooling holes penetrating into the mold, In this method, the adjusted cooling water is circulated through the water cooling holes of the mold to cool the mold.

  Examples of the mold include a die such as a die casting mold, a casting mold, and a resin molding mold for molding a resin by injection molding or compression molding. The mold is formed with water cooling holes penetrating the mold. The water cooling holes are for cooling the mold in order to stably mold by keeping the temperature of the mold constant when molding metal or resin using the mold. Cooling water is circulated through the water cooling holes to cool the mold. The shape of the water cooling holes can be determined as appropriate depending on the shape of the mold and the degree of cooling. For example, when relatively cooling is desired, many through holes may be formed in the mold to increase the contact area between the circulating cooling water and the mold.

  For example, industrial water can be used as the cooling water flowing through the water cooling holes of the mold, and is not particularly limited. The temperature of the cooling water is usually set to room temperature or lower, but the temperature can be appropriately set by a cooling device or the like. Cooling water such as industrial water is neutral near pH 7. Therefore, in the mold cooling method according to the present invention, a rust preventive agent is added to the cooling water to adjust the pH to 9 or more.

  The rust inhibitor added to the cooling water is not particularly limited as long as it is an aqueous rust inhibitor that makes the pH of the cooling water 9 or higher, but contains an amine such as an amine alone or an amine salt of an organic acid. Rust preventives are preferred. In view of volatility and handleability, an amine salt of an organic acid is more preferable.

  Examples of amine-containing rust inhibitors include alkanolamines such as monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, and monobutanolamine, and alkylamines such as monomethylamine, dihexylamine, dicyclohexylamine, and tributylamine. Examples thereof include imidazole derivatives and triazole derivatives. In the alkanolamine or alkylamine, the number of hydroxyalkyl groups, the number of carbon atoms of the hydroxyalkyl group, and the number of carbon atoms of the alkyl group are not particularly limited. Moreover, the amine which has both a hydroxyalkyl group and an alkyl group may be sufficient. Furthermore, diamine, triamine and the like may be used.

  Examples of the organic acid constituting the amine salt of the organic acid include aliphatic or aromatic mono- or dicarboxylic acid, aliphatic or aromatic mono- or relatively high carbon number (for example, about 4 to 20 carbon atoms). Examples thereof include disulfonic acid, urea-based condensates and derivatives thereof. Examples of urea-based condensates include cyanuric acid, isocyanuric acid, hydantoin, uric acid, and allantoin. Derivatives thereof include alkyl groups and acyl groups having a relatively small number of carbon atoms (for example, about 1 to 4 carbon atoms). Can be exemplified. These organic acids may be saturated acids or unsaturated acids. When the organic acid is a dicarboxylic acid or disulfonic acid, it may form a monoester with a saturated or unsaturated mono- or polyhydric alcohol.

  In addition to the amine-containing rust inhibitor, the organic acid metal salt (alkali metal, alkaline earth metal) or inorganic acid metal salt is used as an aqueous rust inhibitor for adjusting the pH of the cooling water to 9 or more. (Alkali metal, alkaline earth metal) or the like may be used.

  Examples of inorganic acid metal salts include nitrites, borates, phosphates, molybdates, and the like. Examples of the alkali metal include lithium, sodium, and potassium, and examples of the alkaline earth metal include calcium and magnesium.

  Furthermore, a rust inhibitor that is emulsified and dispersed in water may be used as an aqueous rust inhibitor that adjusts the pH of the cooling water to 9 or more. Examples of the rust preventive to be emulsified and dispersed in water include, for example, those containing a wax or an oxidized wax obtained by oxidizing a wax as a main component, and an organic acid salt or amine added thereto. At this time, the amine is added for the purpose of emulsifying and dispersing a rust inhibitor containing wax or oxidized wax.

  The rust preventives described above can be used alone or in combination. For example, when an amine-containing rust inhibitor is used, the above-mentioned inorganic acid metal salt, a metal salt of a carboxylic acid having about 8 to 16 carbon atoms, a metal salt of a dibasic acid having 9 to 12 carbon atoms, etc. are combined. Can do.

  In addition, in the salt of an organic acid and the salt of an inorganic acid, the mixing ratio of the acid component and the alkali component may be equal, or the alkali component may be in an excessive ratio.

  The rust preventive agent is preferably added to the cooling water so as to have a concentration of about 0.001 to 0.1% by weight in consideration of the rust preventive effect and the increase in the viscosity of the liquid due to the addition. At this time, a desired pH (9 or more) is obtained.

  In addition to the above-mentioned rust preventive agent, this cooling water contains antioxidants, antifoaming agents, mineral oils, surfactants, antiseptics, antifungal agents, non-ferrous as necessary, as long as the effects of the present invention are not impaired. Various additives such as metal anticorrosives and hard water softeners can also be added.

  The mold cooling method according to the present invention can be carried out by circulating cooling water having a pH of 9 or more by adding the above rust preventive by means of an apparatus for circulating ordinary cooling water. For example, a method of storing cooling water having a pH of 9 or more by adding the above rust preventive to a water tank, connecting the water tank and a water cooling hole of a mold with a pipe, and circulating the cooling water through a pump, etc. Can be illustrated. In addition, when there are parts made of resin, such as piping, an alkali-resistant one that is not affected by a highly alkaline liquid having a pH of 9 or higher may be used.

  According to the mold cooling method as described above, the occurrence of rust in the water cooling holes, which has been a problem during operation, can be suppressed. And by suppressing generation | occurrence | production of rust by inhibiting generation | occurrence | production of the intergranular corrosion of a water-cooled hole, it can prevent that a crack generate | occur | produces in this water-cooled hole which has generate | occur | produced the stress by thermal fatigue. Thereby, the lifetime of a metal mold | die can be improved.

  Next, examples will be described in detail.

〔Test conditions〕
Evaluation mold material: Hot working tool steel SKD61 (HRC46)
Evaluation liquid: Liquid D consisting of industrial water (pH = 7.2) and three types of rust-proof water (liquid A (pH = 10. 2) obtained by adding a predetermined amount of a rust inhibitor to industrial water (pH = 7.2). 5), B liquid (pH = 9.5), C liquid (pH = 7.8) in total 3 types of rust preventives: manufactured by Yushiro Chemical Co., Ltd., trade name “Yushiloop WH3”
Melting temperature of aluminum alloy: 700 ° C

[Test operation]
FIG. 1 shows a schematic cross-sectional view of a die casting mold used for the evaluation test. The operation of producing a die-cast product was repeated by pouring molten aluminum alloy (700 ° C.) into the internal cavity 16 surrounded by the fixed die 12 and the movable die 14 of the die-casting die 10 and die-casting. At this time, the cooling water was circulated through the water cooling holes 18 (hole diameter = 10φ) of the die casting mold 10 to adjust the temperature of the mold.

〔Evaluation methods〕
(Rust generation)
The state of the water-cooled holes every 500 times of die casting was observed with an endoscope to examine whether or not rust was generated in the water-cooled holes. Further, when rust was generated, the number of repetitions of die casting until rust was generated was examined.

(Cracking)
After die-casting was repeated 3000 times, the water-cooled hole portion of the mold was cut, and the presence or absence of cracks in the water-cooled hole was examined.

(Example 1-2)
Die-casting is repeated while circulating anti-rust water A (pH = 10.5) or anti-rust water B (pH = 9.5) as cooling water, and whether or not rust occurs in the water cooling holes. The number of repetitions of molding and the presence or absence of cracks in the water-cooled holes were examined. FIG. 2 shows an endoscopic photograph of the water cooling hole for confirming whether or not rust is generated in the water cooling hole. Moreover, the cross-sectional photograph of the water cooling hole which confirms the presence or absence of the generation | occurrence | production of the crack to a water cooling hole is shown in FIG. These results are summarized in Table 1.

(Comparative Example 1-2)
It was carried out in the same manner as in Example 1-2, except that the D liquid consisting of the rust preventive water C liquid (pH = 7.8) or the industrial water (pH = 7.2) was circulated as the cooling water. FIG. 2 shows an endoscopic photograph of the water cooling hole for confirming whether or not rust is generated in the water cooling hole. Moreover, the cross-sectional photograph of the water cooling hole which confirms the presence or absence of the generation | occurrence | production of the crack to a water cooling hole is shown in FIG. These results are summarized in Table 1.

  As in Comparative Example 2, when the D liquid consisting of industrial water (pH = 7.2) was circulated through the water-cooled holes, as shown in Table 1 and FIG. 2, when die casting was repeated 500 times, The generation of rust was confirmed in a part of the water cooling holes (such as the upper right in FIG. 2), and after 2000 times, the generation of rust was confirmed throughout the water cooling holes. Then, as shown in FIG. 4, after the die casting was repeated 3000 times, it was confirmed that cracks occurred in the curved portion R of the water cooling hole shown in FIG. It was.

  In addition, as in Comparative Example 1, when rust prevention water solution C (pH = 7.8) was circulated through the water-cooled holes, it was confirmed that rust was generated in the water-cooled holes when die casting was repeated 2000 times. It was done. After the die casting was repeated 3000 times, it was confirmed that cracks occurred at the curved portion R of the water-cooled hole shown in FIG.

  On the other hand, when the rust preventive water A solution (pH = 10.5) was circulated through the water cooling holes as in Example 1, the die casting was repeated 3000 times as shown in Table 1 and FIG. Later, it was confirmed that no rust was generated. As shown in FIG. 3, it was confirmed that no cracks occurred in the curved portion R of the water-cooled hole shown in FIG. 1 even after the die casting was repeated 3000 times.

  Similarly, as in Example 2, when the antirust water B solution (pH = 9.5) was circulated through the water cooling holes, rust was generated in the water cooling holes after 3000 times of die casting. It was confirmed that there were no cracks and no cracks.

  Thus, when the industrial water which does not add a rust preventive agent was circulated to the water cooling hole of a metal mold | die, the rust generate | occur | produced in the water cooling hole and the crack generate | occur | produced. And even if a rust preventive agent is added to industrial water, when the pH is not 9 or higher, rust and cracks are similarly generated in the water-cooled holes, but by adjusting and managing the pH to 9 or higher, It was found that it was possible to suppress the occurrence of rust and prevent the water cooling holes from cracking.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  For example, in the above embodiment, the presence or absence of rust and the presence or absence of cracks are evaluated using one rust inhibitor, but other rust inhibitors may of course be used. In short, a rust inhibitor may be added to the cooling water used for cooling the mold and the cooling water adjusted to pH 9 or higher to cool the mold.

It is a schematic sectional drawing of the die-cast metal mold | die used for the evaluation test of an Example and a comparative example. It is an endoscopic photograph of the water cooling hole which confirms the presence or absence of generation | occurrence | production of the rust to the water cooling hole in an Example and a comparative example. It is a cross-sectional photograph of the water cooling hole which confirms the presence or absence of generation | occurrence | production of the crack to the water cooling hole in an Example. It is a cross-sectional photograph of the water cooling hole which confirms the presence or absence of generation | occurrence | production of the crack to the water cooling hole in a comparative example.

Explanation of symbols

10 Die casting mold 12 Fixed mold 14 Movable mold 16 Cavity 18 Water cooling hole R Curved part of water cooling hole

Claims (2)

  After adding a rust preventive agent to the cooling water for cooling the mold that circulates through the water-cooled holes penetrating the inside of the mold such as a die-cast mold or a forged mold, the pH is adjusted to an alkali of 9 or higher. A method for cooling a mold, wherein alkaline cooling water is circulated through the water cooling hole of the mold.   The rust preventive agent containing an amine is added to the cooling water to adjust the pH to 9 or higher, and then the alkaline cooling water is circulated through the water cooling holes of the mold. Mold cooling method.