JPH057978A - Graphite mold release agent for forging molten metal - Google Patents

Abstract

PURPOSE:To provide the graphite mold release agent which has good adhesive ness even to metallic molds of the temp. ranging 100 to 450 deg.C and has a small degree of the deposition of graphite in the metallic molds. CONSTITUTION:The components and compounding ratios of the graphite mold release agent are specified to the liquid mixture contg. (a) 20 to 25wt.% natural graphite powder having a grain size distribution which is in a range of 0.1 to 5mum average grain sizes and in which the particles having <=0.1mum particle size are <=5wt.% and the particles having >=5mum particle size are <=5wt.%, (b) 1.0 to 2.0wt.% carboxy methyl cellullose having 100 to 10000 degree of polymn., (d) 1.0 to 2.0wt.% arom. surfactant, and (d) 0.2 to 0.4wt.% ammonia and the balance water. Further, this liquid is so diluted that the content of the natural graphite powder attains 0.6 to 1.0wt.% at the time of use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphite mold release agent for forming a uniform graphite film on a high temperature mold, and more particularly to a graphite mold release agent suitable for molten metal forging. The molten metal forging method is a method of slowly injecting a molten metal, for example, a molten aluminum (for example, the molten metal forging method is mainly used for die casting of aluminum, which will be described below with aluminum as an example) into the mold at a low speed. , A casting method of solidifying while pouring high pressure to the injected aluminum melt in the mold. Since the molten metal forging method slowly injects the molten aluminum into the mold at a low speed,
There is no generation of pores due to air entrainment, etc., and because the molten aluminum is solidified while applying high pressure, it is a casting method with few defects inside the cast product, and in addition it is a mechanically excellent die casting that is easy to heat treat. It has the advantage that a casting can be obtained.

[0002]

2. Description of the Related Art In a general casting method, a water-soluble mold release agent in which mineral oil, animal or vegetable oil, wax, etc. are emulsified and dispersed in water is often used. A release agent is used. This is because when a water-soluble mold release agent used in a general casting method is used in the molten metal forging method, gas components generated by evaporation of mineral oil, animal and vegetable oil, wax, etc., or thermal decomposition at the time of casting cause pore formation. This is because the graphite film is superior in high pressure transfer property, heat retention property, and hot water flow property as compared with a coating film of mineral oil, animal or vegetable oil, wax, or the like.

[0003]

In order to obtain a casting with excellent porosity and other internal defects inside the casting and excellent mechanical properties by the molten metal forging method, the mold for casting the molten metal should be 100%.
It should be maintained at a temperature in the range of ~ 450 ° C. However, conventional graphite mold release agents have poor adhesion to such high temperature molds and cannot form a uniform graphite film of desired thickness on the molds. The releasability from the cast was not sufficient. Therefore, in order to improve the mold releasability, when a large amount of mold release agent is spray-coated on the inner surface of the mold, the mold temperature is in the range of 100 to 450 ° C due to the cooling action of the water contained in the mold release agent. Since it is lower, the incidence of pores and internal defects increases. As a result, the yield of the die cast casting was reduced. Furthermore, a large amount of spray-coated graphite was deposited in the mold, which caused the die cast casting to have a wall thickness. In order to avoid this, it is necessary to remove the deposited graphite from the mold, which reduces the productivity of the die casting process. In view of the above-mentioned problems with the conventional graphite mold release agent, the object of the present invention is 10
It is an object of the present invention to provide a graphite mold release agent having good adhesion even to a mold having a temperature in the range of 0 to 450 ° C and having a small degree of depositing graphite in the mold.

[0004]

As a result of research and experiments, the inventors of the present invention have found that the adhesion of the graphite mold release agent to the high temperature mold is mainly determined by the particle size distribution of graphite, the degree of polymerization of carboxymethyl cellulose and its addition. It was found that the amount depends on the amount, and based on these facts, the above object was achieved by defining the compounding ratio of the components of the release agent, which is the feature of the present invention. That is, the features of the present invention are: (a) particles having an average particle size in the range of 0.1 μm to 5 μm, 5% by weight or less of particles having a particle size of 0.1 μm or less, and particles having a particle size of 5 μm or more. Is 20 to 25% by weight of natural graphite powder having a particle size distribution of 5% by weight or less, (b) 1.0 to 2.0% by weight of carboxymethylcellulose having a polymerization degree of 100 to 1000, and (c) an aromatic surfactant.
1.0 to 2.0% by weight, and (d) ammonia from 0.2
A graphite mold release agent for forging of molten metal, which is a mixed liquid containing 0.4% by weight and the balance being water, which is diluted with water so that the content of natural graphite powder becomes 0.6 to 1.0% by weight when used.

The natural graphite powder used in the present invention is
Commercially available ones can be used, but the average particle size is in the range of 0.1 μm to 5 μm, particles with a particle size of 0.1 μm or less are 5% by weight or less and particles with a particle size of 5 μm or more are 5% by weight. It should have the following particle size distribution. The average particle size is 0.
If the particle size is 1 μm or less, or if particles with a particle size of 0.1 μm or less are contained in an amount of 5% by weight or more, graphite is oxidized during injection of the molten aluminum and becomes CO ₂ gas, which remains as pores in the casting. This is because the cast product becomes a defective product. On the other hand, when the average particle size is 5 μm or more, or when 5% by weight or more of particles having a particle size of 5 μm or more are contained, the amount of graphite powder deposited on the mold increases. If you leave it as it is and continue to use it, defects such as missing pieces of the casting will increase,
It is necessary to remove the graphite deposited on the mold, which reduces productivity. In the present invention, the degree of polymerization of carboxymethyl cellulose used is defined as 100 to 1000, and the addition amount of carboxymethyl cellulose is 1.0.
To 2.0% by weight. When the degree of polymerization of carboxymethyl cellulose is 100 or less, the viscosity of the release agent is insufficient and the adhesion between the release agent and the mold at high temperature is reduced, and a uniform graphite film cannot be obtained. Difficulty in moldability causes scratches, cissing and the like. On the other hand, when the degree of polymerization of carboxymethyl cellulose is 1000 or more, the viscosity of the release agent increases, the moisture contained in the release agent does not evaporate, the drying property of the release agent decreases, and the water content when pouring the molten aluminum is reduced. Causes evaporation and causes porosity in the casting. If the amount of carboxymethyl cellulose added is 1.0 wt% or less, the viscosity of the release agent will be insufficient and the adhesion between the release agent and the mold at high temperature will decrease, and a uniform graphite film cannot be obtained. As a result, a difficulty in releasability occurs, causing galling, cissing and the like. Conversely, the amount of carboxymethyl cellulose added is 2.
When the content is 0% by weight or more, carboxymethylcellulose is thermally decomposed during pouring of molten aluminum, and the generated gas causes generation of pores in the casting. In addition, the binder effect of carboxymethyl cellulose increases the deposition of graphite powder in the mold.

In the present invention, the aromatic surfactant is used in an amount of 1.0 to 2.0% by weight in order to secure the dispersibility of the graphite powder. It is not necessary to use a special surfactant as the surfactant to be used, and a commercially available aromatic surfactant can be used. The reason why the amount of aromatic surfactant added is 1.0 to 2.0% by weight is that even if 2% by weight or more is added, the effect does not increase so much and the effect of the present invention is impaired.
This is because the effect of addition is small when the content is less than wt%. Further, in the present invention, in order to stabilize the dispersion of graphite and prevent the deterioration of the release agent, commercially available aqueous ammonia having a concentration of 25% is added to adjust the concentration of ammonia to 0.2 to 0.4% by weight. The reason why the amount of ammonia added is set to 0.2 to 0.4% by weight is that even if 0.4% by weight or more is added, the effect does not increase so much and the effect of the present invention is impaired, and if it is 0.2% by weight or less, the effect of addition is small. is there. The balance of the release agent according to the present invention is water, and water is used as a dispersion medium. Further, from the viewpoint of coating property of the release agent and distribution of graphite upon use, it is diluted with water so that the content of natural graphite powder is 0.6 to 1.0% by weight and used as an aqueous solution. In the present invention, the content of the natural graphite powder as the release agent is set to 20 to 25% by weight in order to obtain a uniform suspension-like dispersion of the natural graphite powder by good mixing. Also, when using a release agent, the content of natural graphite powder should be 0.6 to 1.0% by weight.
The reason for diluting the release agent is that if the content of the natural graphite powder is diluted to a predetermined weight% from the beginning of the production of the release agent, the volume of the release agent increases, which is inconvenient for transportation.

The production of the graphite release agent according to the present invention does not require a special apparatus or a special method, and the above-mentioned compounding agents are put in an appropriate container and premixed in advance, and then an appropriate palindrome method is used. The water-soluble mold release agent for forging of molten metal according to the present invention is prepared by sufficiently mixing at room temperature and atmospheric pressure with a mixer such as a ball mill.
When used, the graphite mold release agent according to the present invention is diluted with water to form an aqueous solution having a natural graphite powder content of 0.6 to 1.0% by weight and applied to a mold by spraying or brushing. Hereinafter, the present invention will be described in more detail based on examples.

[0008]

【Example】

Example 1 The ingredients listed below were added in the amounts shown below, and the ingredients were thoroughly mixed at room temperature in a laboratory ball mill.
A graphite mold release agent was obtained. Natural graphite powder (the particle size distribution is shown in Table 1) 4.8 Kg Carboxymethyl cellulose Polymerization degree 100 160 g Carboxymethyl cellulose Polymerization degree 800 80 g (Nichirin Chemical Industry Co., Ltd.) Aromatic surfactant (sodium naphthalene sulfonate) 300 g (manufactured by Kao Corporation) 25% ammonia water 300 g Water 14.36 Kg Total 20.0 Kg

Table 1 Particle size distribution of natural graphite powder used in Example 1 D (μm) F (%) R (%) 5.00 <0.0 0.0 5.00-1.00 36.3 36.3 1.00-0.10 60.4 96.7 0.10-0.00 3.3 100.0 The above particle size distribution is based on the Horiba centrifugal automatic particle size distribution measuring device.
Measured by CAPA-500, D is the particle size, F is the particle weight% for each particle size classification, and R is the cumulative total of the particle weight% for each particle size classification. In order to evaluate the performance of the graphite mold release agent of Example 1 obtained as described above, it was diluted 30 times to 40 times with water, and the adhesion to the mold and the graphite mold were subjected to the following conditions. The degree of deposition, that is, the non-depositability of graphite, was tested, and the results are shown in Table 2 by a two-stage evaluation of ◯ and ×. Further, the graphite mold release agent of Example 1 was applied every time the molten metal forging was performed to obtain 1
The molten metal forging was performed 000 times, the defective rate of the cast was calculated, and the results are also shown in Table 2. Performance test conditions Mold temperature 200 ° C to 350 ° C Melt composition Aluminum forging pressure 98 MPa

Table 2 Evaluation results Adhesiveness Graphite non-depositing Product defect rate Example 1 ○ ○ 2% Example 2 ○ ○ 1.5% Comparative example 1 ○ ○ 25% Comparative example 2 ○ × 20% Comparative example 3 ○ × 18 % Comparative Example 4 × ○ 21% Comparative Example 5 × ○ 10%

Example 2 120 g of carboxymethyl cellulose having a degree of polymerization of 800 and water
A graphite mold release agent according to the present invention was prepared in the same manner as in Example 1 except that 14.32 Kg was added, and the performance was evaluated in the same manner as in Example 1, and the results are shown in Table 2. It was shown to. Comparative Example 1 Graphite separation prepared in the same manner as in Example 1 except that natural graphite powder having an average particle size of 0.08 μm was used in place of the natural graphite powder having the particle size distribution shown in Table 1 used in Example 1. Comparative Example 1 was used as the mold agent, the same evaluation as in Example 1 was performed, and the results are shown in Table 2. Comparative Example 2 Graphite release prepared in the same manner as in Example 1 except that natural graphite powder having an average particle size of 7 μm was used in place of the natural graphite powder having the particle size distribution shown in Table 1 used in Example 1. The agent was used as Comparative Example 1, the same evaluation as in Example 1 was carried out, and the results are shown in Table 2.

Comparative Example 3 250 g of carboxymethyl cellulose having a degree of polymerization of 100 and 250 g of carboxymethyl cellulose having a degree of polymerization of 800 were also measured.
A graphite mold release agent prepared in the same manner as in Example 1 except that 500 g was used, was evaluated in the same manner as in Example 1, and the results are shown in Table 2. Comparative Example 4 80 g of carboxymethyl cellulose having a degree of polymerization of 100 and 80 g of carboxymethyl cellulose having a degree of polymerization of 800 were also measured.
A graphite mold release agent prepared in the same manner as in Example 1 except that 160 g was used, was used as Comparative Example 1 and evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 5 The following compounding agents were compounded in the amounts shown below, and the compounds were thoroughly mixed at room temperature in a laboratory ball mill and Comparative Example 5
A graphite mold release agent was prepared. The graphite release agent of Comparative Example 5 obtained was evaluated in the same manner as in Example 1, and the results are shown in Table 2. Comparative Example 5 contains 5% by weight or more of natural graphite powder having a particle size of 0.1 μm or less, and contains carboxymethylcellulose in an amount of 2.0% by weight or more. Properties, graphite non-deposition property, and product defect rate are inferior to the examples. Natural graphite powder (the particle size distribution is shown in Table 3) 5.0 Kg Carboxymethyl cellulose Polymerization degree 100 400 g Carboxymethyl cellulose Polymerization degree 800 100 g (Nichirin Chemical Industry Co., Ltd.) Aromatic surfactant (sodium naphthalene sulfonate) 100 g (manufactured by Kao Corporation) Ammonia water with a concentration of 25% 300 g Water 14.1 Kg Total 20.0 Kg

Table 3 Particle size distribution of natural graphite powder used in Comparative Example 5 D (μm) F (%) R (%) 5.00 <0.0 0.0 5.00 to 1.00 14.4 14.4 1.00 to 0.10 77.9 92.3 0.10 to 0.00 7.7 100.0 The particle size distribution is measured by the Horiba centrifugal automatic particle size distribution analyzer CAPA-500 as in Example 1, and D is the particle size,
F represents the weight% of particles in each particle size category, and R represents the cumulative total of the particle% in each particle size category. As shown in Table 2, the graphite mold release agents of the examples have good adhesion to the mold and non-deposition of graphite in the mold, and the defective rate of cast products is much higher than that of conventional products. Very low. On the other hand, in the comparative example, the adhesiveness to the mold, the non-deposition of graphite in the mold, and / or the defective rate of the cast product are not preferable.

[0015]

EFFECTS OF THE INVENTION The present invention has good adhesiveness to molds, releasability and graphite non-deposition property depending on the specific particle size distribution of the above-mentioned natural graphite powder according to the present invention, the releasing agent component and the specific compounding ratio thereof. In 1
Provided is a graphite release agent which forms a graphite film having a uniform film thickness on a mold at 00 ° C to 450 ° C. Thereby, the present invention prevents the yield reduction of the die casting product due to the pores and internal defects of the die casting, and prevents the lack of wall thickness of the die casting due to the deposition of graphite in the mold and the deposition of graphite. This has the effect of avoiding a decrease in productivity due to the removal work.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yuuo Yada 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Ikuo Suzuki 1, Toyota Town, Aichi Prefecture, Toyota Motor Co., Ltd. ( 72) Inventor Akira Seki 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd.

Claims (1)

Claims (a) The average particle size is from 0.1 μm to 5 μm.
20% to 25% by weight of natural graphite powder having a particle size distribution of 5% by weight or less of particles having a particle size of 0.1 μm or less and 5% by weight or less of particles having a particle size of 5 μm or more. (B) 1.0 to 2.0% by weight of carboxymethylcellulose having a degree of polymerization of 100 to 1000, (c) 1.0 to 2.0% by weight of an aromatic surfactant, and (d) 0.2 to 0.4% by weight of ammonia. A graphite mold release agent for molten metal forging, which is a mixed solution of which the balance is water and which is diluted with water so that the content of the natural graphite powder becomes 0.6 to 1.0% by weight when used.