JPS58141830A - Mold coating material for die casting - Google Patents

Abstract

PURPOSE:To provide a mold coating material for die casting which is so formulated as to prevent sand burning and misrun in the stage of the casting by compounding mica and metallic powder or metallic oxide powder to water soluble salt added with a surfactant. CONSTITUTION:A mold coating material for die casting prepd. by adding mica, metallic powder such as aluminum powder or metallic oxide into an aq. soln. contg. an anionic surfactant, etc., a suitable defoamer, and water soluble salts such as potassium silicate as a binder, and mixing and agitating the mixture. Such coating material is coated on the inside surface of the cavity of dies and molten metal of an aluminum alloy or the like is supplied therein, whereby die casting is accomplished. The generation of sand burning and misrun is prevented by such mold coating material even if the rate of injection of the molten metal is decreased. Since the material has excellent coatability and a mold releasing property, the cast products having high dimensional accuracy and contg. no cavities, etc. are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating agent for mold casting, which is particularly suitable for die casting methods in which the injection speed of molten metal is slowed down, among mold coating agents used in mold casting.

The die casting method, which is a pressure casting method, is widely used due to its advantages in terms of improving productivity. In order to improve the circulation of the molten metal without lowering the temperature of the molten metal, the injection speed is significantly increased and the injection pressure is increased.

In such a die-casting method, the molten metal circulates quickly within the cavity, so there is no need to take into account cooling of the molten metal through the cavity. For example, a mixture of a heat-resistant metal powder such as A1 powder and a carbonaceous material such as graphite suspended in an aqueous solution containing a water-soluble resin is used as a binder.

However, increasing the injection speed of the molten metal has the disadvantage of entraining air and creating cavities inside the cast product. For this reason, the inventors increased the temperature of the mold and slowed down the injection speed (
It was discovered that by doing so, the occurrence of blowholes was reduced.

However, if the injection speed is slow (this may lead to problems with the flow of the metal), it is possible to avoid this by applying a heat-insulating mold coating used in the gravity casting method inside the cavity; There is a problem with the variety of life etc., so it cannot be applied.

In view of the above-mentioned conventional problems, the present inventors have created the present invention to effectively solve the problems.The purpose of the present invention is to improve the injection speed of molten metal in pressure casting methods such as die casting methods. It is an object of the present invention to provide a mold coating agent for mold casting which has excellent coating properties and mold releasability without causing baking or poor water flow even if it is delayed.

Preferred embodiments of the present invention will be described in detail below.

First, 5% of dialkyl sulfone co-phosphate, which is an anionic surfactant, is added as a wetting agent to water.
Add 15Qcc of aqueous solution, 20CC1 of N-octyl alcohol as an antifoaming agent, and 20f of potassium silicate solution, which is a water-soluble salt as a binder, and mix and stir for 5 to 10 minutes to minimize the generation of bubbles.Next, , metal aluminum powder 450 and synthetic mica (sodium Φ
Aqueous solution containing 15% (including fluorine and tetrasilicon) 1.51
and mix and stir for 10 to 15 minutes to obtain the desired coating agent.

Spray the above mold coating onto the surface of the mold cavity preheated to approximately 200°C, blow off the excess mold coating remaining in the cavity recess with compressed air, and reduce the coating material to a maximum film thickness of approximately 4μ. And so. □After that, aluminum alloy (AD
(equivalent to C12) with a casting pressure of 220, sprue speed of 0.5 m
/sec, and the molten metal was supplied into the cavity at a temperature of 700° C., and a cylinder block for an automobile was die-cast.

The resulting product has excellent dimensional accuracy and casting surface because the mold coating has a maximum film thickness of 4 μm, and also has excellent dimensional accuracy and casting surface because the mold coating contains mica, which has an excellent heat insulating effect. Moreover, since mica is highly interosseous and exhibits excellent fluidity when in contact with water, the mold coating agent can easily adhere to and transfer to the product, making it easy to apply the coating after each casting. Applying a mold will not have any negative effects.

Next, an experiment comparing the thermal insulation properties of the mold coating agent according to the present invention and conventional mold coating agents for die casting and gravity casting coating agents will be described with reference to the accompanying drawings.

The experiment was carried out using an apparatus as shown in FIG. Various types of coating agents are applied, and aluminum alloy (AD) is applied from above the device.
C12 equivalent) 1.5# molten metal 4 was supplied under the conditions of 700°C and 30% pressure, and the relationship between the temperature of the mold 1 and the elapsed time was compared for each mold coating agent, and the results were Shown in the figure.

As is clear from FIG. 2, the heat insulation properties of the mold coating agent according to the present invention are dramatically superior to those of conventional die casting mold coating agents.
It can be seen that it is roughly equivalent to a coating agent for gravity casting.

Furthermore, since the mold temperature before casting in the die-casting method is generally 150 to 200°C, if we compare the mold coating agent of the present invention and the mold coating agent for gravity casting in this temperature range, it is found that the mold coating agent of the present invention is superior to the mold coating agent for gravity casting. It can be seen that it has excellent heat insulation properties and therefore has excellent hot water circulation properties.

As is clear from the above explanation (according to the present invention, surfactants are added to the coating agent applied to the inner surface of the cavity of die casting, which slows down the injection speed of the molten metal and prevents the formation of cavities, etc.). The composition is made by mixing water-soluble salts with mica, which has excellent heat insulating properties and fluidity, and metal powder or metal oxide powder that has the same coating properties as above, so it has good circulation during casting and prevents seizure. Since this does not occur, it is possible to obtain a product with excellent dimensional accuracy and no inclusion of blowholes, etc.The mold coating agent of the present invention is easy to adhere to and transfer to the cast product, so it is easy to apply the mold after each casting. Furthermore, since it does not contain carbonaceous substances unlike conventional materials, it has many advantages such as improving the working environment.

[Brief explanation of the drawing]

The drawings show the experimental results of the present invention; FIG. 1 is a schematic side view of the experimental apparatus, and FIG. 2 is a diagram showing the experimental results. In the drawings, 1 is a mold, 2 is a thermocouple, and 3 is a bottom member. Patent applicant Honda Motor Co., Ltd.

Claims (1)

[Claims] A coating agent for mold casting, which is a mixture of mica to which a surfactant has been added and metal powder or metal oxide powder, which is adhered to and transferred to cast products and is used to coat the mold each time casting is performed.