JPH10296392A - Coating agent on metallic mold for adjusting heat conduction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means which can easily adjust the heat conductive characteristic of a metallic mold for casting. SOLUTION: In a coating agent containing at least binder and inorganic particles as the main agents, coating layer 7 is formed on the back surface of the metallic mold necessary to heat insulate and used. This coating agent can easily be adjusted to the necessary heat insulating degree by changing this composition and adjusting the thickness of the coating layer. Further, since the coating layer 7 can easily be formed only to the necessary surface position in the metallic mold with applying, etc., the further suitable heat insulation of the metallic mold can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating agent which is fixed to a back surface of a mold such as a casting mold or a die casting mold, which does not define a cavity, and adjusts heat released from the mold. About.

[0002]

2. Description of the Related Art Conventionally, in order to control the temperature of a mold for casting or the like, a heater is provided inside the mold, or the mold is heated by a burner. In areas where these heaters and burners cannot be inserted, the thickness of the mold is reduced to reduce the heat capacity of that area, reduce the heat absorption heat capacity of the molten metal by the mold, and pack a heat insulating material on the back side of the mold The convection of air to reduce the amount of heat radiation from the mold, and increase the thickness of the coating agent applied to the mold surface that defines the cavity of the mold to reduce the heat transfer from the molten metal to the mold. And kept warm by doing.

In the method of reducing the thickness of the mold, when the thickness of the mold is reduced to about 10 mm, the characteristic that the mold temperature changes following the casting cycle becomes remarkable. Therefore, when the mold is opened after the product is released, the temperature of the mold is lowered due to natural heat radiation, and it is likely that a failure occurs at the next shot. The method of filling the heat insulating material was effective when the temperature on the back surface of the mold was high and casting was performed in a steady state, but was ineffective when the casting cycle was low or the casting cycle was pulsating.

The method of thickening the coating film is effective at an early stage when the film thickness is secured because the coating film is worn or peeled, but the coating film is worn or peeled with time. The effect is reduced. That is, this method of thickening the coating film involves casting while the heat retention conditions are constantly decreasing. In particular, in a portion where the mold thickness is 15 mm or less and the mold temperature is about 350 ° C. or less, only the method of increasing the thickness of the coating film can be dealt with, and the method cannot be adopted. In addition, even if all of the above methods are applied, in areas where the supply heat of the molten metal is not sufficient, such as the tip of the molten metal, the final filling part, and the thin part of the product, an appropriate mold temperature cannot be secured, and the molten metal will not turn or shrink. There was a defect.

[0005]

SUMMARY OF THE INVENTION The present invention provides an adjusting die coating agent for adjusting the amount of heat radiated from a casting die other than the above.

[0006]

Means for Solving the Problems The inventor of the present invention has intensively developed a method for keeping a mold warm in order to solve the above-mentioned problems. The fact that forming a heat insulating layer with low heat dissipation and high heat storage on the back surface that does not define the cavity of the casting mold by coating is advantageous for heat insulation during casting, and that the heat insulating layer formed by coating Was found to be effective continuously until the end of the mold life, and was confirmed by actually performing additional tests to complete the coating agent of the present invention.

[0007] That is, the coating agent of the present invention is fixed to the back surface of the casting mold that does not define the cavity, and contains at least a binder and inorganic particles as main components. The coating agent of the present invention is used in the form of a paste, which is used by forming a coating layer on the back surface of a mold requiring heat retention by coating or the like, and fixing it to the mold surface by drying or the like. The required degree of heat retention can be easily adjusted by changing the composition of the coating agent or adjusting the thickness of the coat layer. In addition, since the coating layer can be easily formed only on the surface portion where the mold is necessary by coating or the like, it is possible to maintain the temperature of the mold more appropriately.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The heat-radiation-adjusting mold coating agent of the present invention is fixed to the back surface of a casting mold that does not define a cavity, and contains at least a binder and inorganic particles as main components. The main agent is composed of a binder and inorganic particles.
The inorganic particles constitute the main component of the main agent and determine the thermal characteristics, particularly the heat insulating characteristics of the coating agent of the present invention. As the inorganic particles, thermally stable metals, oxides, nitrides and the like are used. In particular, thermally stable ceramic particles and the like are preferable. Specifically, metal oxides such as silica, alumina and magnesia, clay minerals, carbon materials and the like are preferable. The particle size is not particularly limited, but a fine particle having a diameter of 1 mm or less is preferable because of good workability.

The inorganic particles preferably have excellent heat insulation properties. From this point of view, it is preferable that the obtained coating layer be porous, that the inorganic particles themselves have a space inside, or that they be porous. Such inorganic particles include shirasu balloon, hollow glass beads, silica gel, expanded vermiculite, fibrous talc, diatomaceous earth,
Asbestos, rock surface, soot graphite, bulk glass wool,
Magnesia brick powder, charcoal powder and the like can be mentioned.
In addition, these inorganic particles having excellent heat insulating properties are handled separately from other inorganic particles as a heat insulating agent, and can be used alone with these heat insulating agents or as a mixture with these heat insulating agents and other inorganic particles.

[0010] In many cases, the strength of a coating layer obtained by using a heat insulating agent is reduced. For this reason, it is appropriate that the compounding amount of the heat insulating agent is about 3 to 40% by weight. In order to give the coating layer a low thermal emissivity, inorganic particles having a low thermal emissivity are used. Materials having a low thermal emissivity include Al ₂ O ₃ (thermal emissivity: 0.50), BeO (thermal emissivity: 0.35), MgO (thermal emissivity: 0.20), Zn
O (thermal emissivity: 0.11), TiO ₂ (thermal emissivity: 0.11)
60), CaCO ₃ (thermal emissivity: 0.40), ZrC
(Thermal emissivity: 0.46) or the like can be used.

The amount of the inorganic particles having a low thermal emissivity is not particularly limited. At least about 5% by weight of the composition is required to impart low heat radiation characteristics to the obtained coating layer. When it is desired that the coating layer has a large heat capacity, a metal having a large heat capacity per unit volume and a high specific gravity can be used as the inorganic particles. In addition, inorganic particles exhibiting a specific function, such as inorganic particles having excellent heat insulating properties, inorganic particles having a low thermal emissivity, and inorganic particles having a large heat capacity, are inorganic particles exhibiting those specific functions, or between ordinary inorganic particles. It can be used by mixing with inorganic particles.

The binder functions to fix the inorganic particles to each other and to integrally fix the obtained coating layer to the back surface of the mold. In some cases, such as a clay mineral, which has both inorganic particles and a binder, does not require any other binder. As the binder, inorganic materials such as kaolin clay, potassium silicate, aluminum phosphate, water glass, sodium silicate, and potassium silicate, organic metal compounds such as ethyl silicate, and metal alkoxide can be used. The binder is preferably incorporated in an amount of about 5 to 25% when the total coating agent is 100% by weight.

It is preferable to form a heat ray reflective layer on the coating layer in order to more effectively suppress heat radiation due to radiation. As the heat ray reflective agent, metal Al (heat absorption: 0.19), metal Ag (heat absorption: 0.02),
Metal Ni (heat absorption rate: 0.05) or the like can be used. Specifically, it is preferable to use such a metal foil piece. In addition,
In order to form a heat ray reflective layer, it is necessary to mix the above-mentioned binders with these heat ray reflective agents to integrally fix the heat ray reflective agents and to bond them to a lower coating layer.

[0014] In addition to the above components, the coating agent
It is preferable to mix a liquid such as water, alcohol, or hydrocarbon and use the coating agent in a slurry or paste form. This facilitates application of the coating agent to the back surface of the mold. It is preferable that the liquid be a solvent that dissolves the binder. By using a solvent, the function as a binder can be maximized, and no other liquid is required as a slurry or paste.

The coating agent of the present invention is mixed with an appropriate solvent or dispersion and used as a slurry or paste. The application to the back surface of the mold can be performed using a brush, a spatula, or an appropriate nozzle. The thickness of the coating can be varied depending on the portion to be applied, and the heat insulation ability can be differentiated. In addition, it is possible to adjust the heat insulating property by shaving the once formed coating layer and peeling off the coating layer at a predetermined portion, or by reducing the thickness of the coating layer. As a result, it is possible to provide an optimal heat insulating property in a portion on the back surface of the mold.

The applied slurry or paste can be formed into a coating layer by evaporating and dispersing a solvent and a dispersion medium which are usually blended. In a special case, the coating layer may be formed by heating with hot air or flame. The coating layer formed with the coating agent of the present invention has a high mechanical strength because it contains a binder, and is stable in gold unless a large stress such as mechanical breakage, chipping, or peeling is applied. Attached to the mold. Therefore, once the optimum coating layer is formed, its characteristics can be exhibited for a long time.

The heat insulating performance by the formation of the coating layer varies depending on the composition of the coating agent used. As an example, the heat insulating performance of a coating agent using 60% of alumina particles, 25% of kaolin clay and 15% of sodium silicate is shown. A 10 mm thick steel plate (material: SKD)
-61), one side of the steel sheet is heated with hot air of 570 ° C, and when the thermocouple embedded in the center in the thickness direction of the steel sheet reaches a steady state of 550 ° C, heating with hot air is performed. The thermocouple was stopped and allowed to stand naturally in the room, and the time until the temperature indicated by the thermocouple reached 350 ° C. was measured. Table 1 shows the relationship between the conditions such as the presence or absence of the coating agent on the heating side of the steel sheet, the presence or absence of the coating layer with the above-mentioned coating agent, and the time until 350 ° C.
And put it together.

As a coating agent, a commercially available die coat 140 (mainly composed of magnesium silicate and sodium silicate), which is a commercial product, to be applied to the mold surface of an aluminum casting mold was used. The coating thickness was 100 μm. The coating layer was formed by adding water to the coating agent to form a slurry, applying the slurry with a brush, and drying. The thickness of this coating layer is also 100 μm
And

[0019]

[Table 1] In Table 1, Test No. No. 5 uses glass wool instead of the coating layer according to the present invention. No. 1 in Table 1.
3 and No. 3 As is clear from FIG. 4, when the coating layer according to the present invention was formed on the back surface of the steel sheet, the temperature drop was slow, and the heat insulating effect was exhibited. Note that test N
o. Insulation effect is lower than glass wool of No.5,
It is difficult to fix the glass wool to the back surface of the steel sheet, and it is also difficult to change the thickness, and it is difficult to obtain a predetermined heat insulating performance using the glass wool. On the contrary,
By increasing the thickness of the coating layer according to the present invention, heat insulating properties can be improved, and any heat insulating properties can be easily provided.

[0020]

Embodiments will be described below with reference to embodiments. In the embodiment, a low-pressure casting mold for low-pressure casting of an aluminum wheel whose main section is shown in FIG. 1 is used. The low-pressure casting mold includes a lower mold 3 fixed on the upper surface of a casting machine lower base 2 located above the aluminum melt 1, an upper mold 4 located above the lower mold 3, and a lower mold 3 and an upper mold 4. It is composed of a horizontal die 5 arranged around the periphery.

FIG. 1 shows the lower mold 2, the upper mold 3 and the horizontal mold 5.
Shows a combined state, and a casting cavity 6 is formed between the three. A stalk 21 through which the molten metal passes is formed in the lower base 2 of the casting machine. In addition, lower mold 3
Of the wheel 21 is formed in a ring shape with the stalk 21 as the center, and the lower mold portion 32 of the cavity portion 61 forming the radially extending portion of the center portion of the wheel is a thin portion. I have. The upper die 4 forming the cavity portion 61 is also provided with a ring-shaped cavity 41 corresponding to the ring-shaped cavity of the lower die 3, and the upper die portion 42 is a thin portion.

In this low-pressure casting mold, shrinkage occurs at a bent portion which extends in the centrifugal direction of the wheel to be cast and extends substantially perpendicularly from the wheel in the centrifugal direction. The cavity 6 corresponds to the cavity portion 62. In the present example, the coating agent of the present invention was used to eliminate this shrinkage. In low-pressure casting, a mold wash 65 containing sodium aluminate silicate as a main component is applied to a mold surface defining the cavity 6,
A film having a thickness of 100 ηm was formed. Molten temperature 6 for molten metal
An aluminum alloy melt at 90 to 720 ° C. was used. And mold temperature 380-450 ℃, casting pressure 0.45k
g / cm ² , coagulation time 140 seconds, and filling time 15 seconds.

As shown by reference numeral 7, the coating layer was formed on a portion of the cavity portion 62 where the shrinkage occurred, which was to be the back surface of the mold. The thickness of the coating layer was 0.5 mm. No. 1 shown in Table 2 was used as the coating agent. 1 color N
o. The test was performed on 13 types of 13 types. Also, for comparison, No. No action was taken on 51, N
o. The test using glass wool in place of the coating layer 7 was also performed on 52.

[0024]

[Table 2] As is clear from Table 2, the test Nos. 1 to
No. By applying the 13 coating agents to the mold and forming the respective coating layers, the rejection rate was 8
It improved to 6% or more. In addition, the sample without a coating layer was designated as Test No. As shown in 51, the closing rate is 78%,
Test pieces using glass wool were tested. As shown in 52, the closing pass rate was 82%.

In particular, the test No. Those using 13 coating agents achieved a closing pass rate of 100%. In this embodiment, the pass rate is set to 100% by changing the composition of the coating agent. However, the pass rate can be increased by adjusting the thickness of the coating layer to be formed.

The test No. 2 shown in Table 2 was used. On the surface of the coating-in layer obtained in 13, the following two kinds of heat ray reflective agents were applied, and a heat ray reflective layer having a thickness of 50 μm was overcoated to form a hand. One heat ray reflector is composed of 10% potassium silicate, 40% water and 50% aluminum metal powder, and the other heat ray reflector is 10% potassium silicate, 40% water and 50% nickel metal powder.
It consists of The mold having the coating layer having the heat ray reflective layer formed by any of the heat ray reflective agents had a rejection rate of 100%.

This example also shows that the coating agent of the present invention has excellent properties as a heat release regulator for a casting mold.

[0028]

The heat-radiation-adjusting mold coating agent of the present invention can suppress the heat radiation of the mold simply by applying it to the back surface of the mold to form a coating layer. As a result, it is possible to effectively reduce casting defects that occur when the heat radiation of the mold is inappropriate.
In addition, it is easy to increase the thickness of the coating layer by coating, or to reduce the thickness by shaving, and the heat radiation characteristics of the mold can be easily adjusted, which is extremely convenient for use. Also,
The coating layer formed is relatively strong, sufficiently withstands vibrations, heat shock, and the like acting on the casting mold, and can maintain its characteristics for a long period of time.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a casting mold for low-pressure casting used in Examples.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Aluminum molten metal 2 ... Casting machine lower base 3 ... Lower mold 4 ... Upper mold 5 ... Horizontal mold 6 ... Cavity 7 ... Coating layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ryuichi Masuda 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Automobile Co., Ltd. Inventor Toshiki Ishikawa 36-3 Higashiishine, Kariya City, Aichi Prefecture Sanwa Yuka Kogyo Co., Ltd.

Claims (4)

[Claims] 1. A heat-dissipation-adjusting mold coating agent fixed to a back surface of a casting mold that does not define a cavity and containing at least a binder and inorganic particles as main components. 2. The coating agent according to claim 1, wherein the main agent includes a heat insulating agent having a higher heat insulating property than the inorganic particles. 3. The coating agent according to claim 1, wherein the main agent comprises a low heat radiation agent having a lower heat emissivity than that of the inorganic particles. 4. The coating agent according to claim 3, wherein the low heat radiation agent is used as an overcoating agent.