JPS6057411B2 - Mold release agent for Al alloy casting molds - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a mold release agent applied to a casting mold, which is mainly used for mold casting of Al-based alloys, particularly for molten metal forging, which is subject to severe conditions for mold release agents. This is related to drugs.

Casting technology has recently made great progress, and a molten metal forging method has been developed that does not cause defects such as cavities or embrittlement of the material, which are the common beliefs associated with conventional cast products.

It is mainly applied to Al' alloys. In this method, after pouring molten metal into a steel mold, the molten metal is pressurized by moving the flancher or part of the mold, and the molten metal flows into and fills the cavities that are generated during solidification. prevent. In addition, since the product adheres to the inner surface of the mold during cooling, the cooling rate becomes faster, resulting in a significantly finer structure compared to conventional methods.
It becomes possible to strengthen the mechanical properties. In mold casting, a release agent is applied to the surface of the mold, and this coating prevents direct contact between the molten metal and the mold, thereby protecting the mold and reducing friction when removing the product. There are relatively few problems with this coating film in non-pressure methods, but in molten metal forging, which involves plastic deformation of the product, the coating film is likely to break and peel, and only mold release agents that can prevent this are used. was. Conventionally, for this purpose, a water-soluble mold release agent consisting mainly of graphite powder and a water-soluble binder dissolved in water has been mainly used. Since this mold release agent has a different color, if it adheres to a product, it will significantly impair the appearance, so it has been desired to make it colorless or white. The present invention replaces black graphite powder, the main ingredient of conventional agents, with white mica powder, etc., adds a solid lubricant to compensate for the lack of lubricity caused by this substitution, and further It uses organic materials such as glue as a binder and is dissolved and dispersed in water.It has almost the same mold release properties as conventional composition agents, and has the feature that it does not damage the appearance even if it adheres to the product. It is something that has been set.

When this mold release agent is applied to a mold that has been preheated to 150 to 200°C, the water in the solvent evaporates and scatters, and the main material and solid lubricant powder form a laminated coating film on the inside of the mold with the help of a binder. Form.

When the molten metal is injected, the organic binder in the surface layer of the coating decomposes and becomes gaseous. In this layer, between the powdery main materials,
Solid lubricant powder is interposed, and the gap is filled with the gas. In this state, the main material powder can move relatively freely, forming a macroscopically plastic and heat-insulating coating film. As the gas dissipates from this layer, the main powder becomes more easily constrained than in the previous state, but due to the presence of the solid lubricant, the degree of constraint is small and the plasticity of this layer remains. . As already explained, in molten metal forging,
A high-temperature product undergoes plastic deformation when pressurized, but since the coating film has plasticity as described above, it deforms following the surface of the product and does not break. In addition, in the undecomposed region of the binder, since the binder is fixed to the surface of the mold, the coating film does not peel off from the mold and is always interposed between the product and the mold, preventing contact between the two. As time passes after pouring, the interface between the decomposed and undecomposed regions of the binder gradually extends from the surface of the coating film to a deeper place, and eventually reaches the surface of the mold, and the solidified coating film It disappears and becomes a powdery layer. If the molten metal is pressurized while the undecomposed area of the binder remains in the coating film,
The coating film under pressure has sufficient plasticity, and after a sufficient period of time has passed, it becomes a powder, and with the added lubrication effect of the solid lubricant, the product can be easily removed. In addition, due to the lubricating action of the solid lubricant added, the agent of the present invention not only releases molds between one product as described above, but also releases molds between a fixed mold and a movable mold, that is, between a plunger and a mold, between a dowel pin and a mold, etc. It can also be used satisfactorily as a lubricant. The main material used in the material of the present invention maintains a color such as transparent or white that does not significantly impair the beauty of the product even if it adheres to the product, has a flaky grain shape with good film-forming properties, and has a temperature of about 700°C. It is a substance that has heat resistance and corrosion resistance against molten Ae.

Mica, talc, and vermiculite alone and in mixtures meet these conditions. There are main materials suitable for Regarding the heat resistance of the solid lubricant, it is preferable to use a material that does not lose its lubricity even at temperatures of about 700'C. However, even if the solid lubricant on the surface of the separated layer of binder decomposes and loses its lubricity, as long as the lubricant in the deeper part does not lose its performance, the main powder will move in that area. , the plasticity of the coating film is substantially maintained. Therefore, the requirements for heat resistance of solid lubricants are:
It should have lubricity at least at a temperature at which the binder loses its adhesive action. These colors need to be colorless, white, etc. as described for the main material. From these points of view, the most preferable material is boron nitride (which is stable up to at least 900°C).
BN), followed by fluorocarbon (CFl decomposition temperature 320-420°C). In addition to these inorganic substances, melamine cyanurate (abbreviated as MCA) is an organic substance.
, sublimation temperature of 360°C). In addition to being water-soluble, the binder adheres the main material powder and solid lubricant to the surface of the mold, which has been preheated to 150 to 200°C, to form a coating film, which decomposes when the product is removed from the mold. The coating film must be powder-like so that it does not lose its adhesive strength. From these points, glue (an example is fibrillar sodium glycolate, abbreviated as CMC), polyvinyl alcohol,
Organic adhesives such as dextrin, molasses, and adhesives, as well as emulsions of resins such as vinyl succinate, are suitable. The content of the present invention will be explained below with reference to Examples.
Example 1 Mica powder with a particle size of 2μ or less was used as the main raw material by weight.
0% and 5% boron nitride powder as a solid lubricant.
Inventive agent 1 was prepared by adding CMCl% to the remaining amount of the solution in water and stirring to suspend.

In addition, in order to examine the effect of adding a solid lubricant, 15% of the mica powder, CMCl. A comparative example consisting of 5% balance water was prepared in a similar manner. Example 2 Inventive agent 2 was prepared by reducing the amount of mica in Example 1 to 7.5%, replacing the solid lubricant with 7.5% fluorocarbon, and keeping the other conditions the same as in the former.

Example 3 In Example 2, the solid lubricant had a particle size of 0.5 to 5p.
of 7.5%, and the binder was CMCl. Inventive agent 3 with a concentration of 5% was prepared.

Further, 15% of graphite powder having a particle size of 10 μm or less was added to and suspended in water in which CMCl% was dissolved to prepare a conventional example. Performance evaluation of these mold release agents was performed as follows.

That is, the mold is made of steel, and the inner diameter, height, and width are each 40 mm.
, 100, and 50wn, and upper and lower circular rods having an outer diameter of 39.7 mm, and after heating these to 150° C., the above-mentioned mold release agent was applied. Molten metal is 12% Si-A
Heat e-alloy (JIS, AC3A) to 700°C, pour it into the cavity formed by the outer diameter and the lower mold, and after pouring,
Pressure was applied with the upper die within seconds. Pressure load is 10r11
, and after applying pressure for 3 hours, the product was taken out from the mold. After cooling, the surface condition of the product was observed to determine whether there was any seizure. This test was repeated 10 times, and the number of times seizure occurred was used as a measure of mold release performance. Table 1 shows the compositions of the agents of the present invention and comparative agents described in Examples and the results of their performance evaluation. The following can be seen from this table.

That is, when Comparative Agent and Inventive Agent 1 are compared, the addition of the solid lubricant significantly improves the mold releasability. Furthermore, Inventive Agents 1, 2, and 3 show that solid lubricants can be used satisfactorily even if they do not necessarily maintain lubricity up to the temperature of the molten metal. The lower limit of the amount of solid lubricant added in the present invention agent is determined by the amount at which the lubricating effect between the main materials of the coating film starts to be noticeable, and the upper limit is determined from the amount of the main material necessary to sufficiently coat the inner surface of the mold. is determined.

As a result of experimentally determining both, (solid lubricant) / (main material)
It has been found that a range of 2.3 to 0.1 by weight is effective. Further, the amount of the binder needs to be 0.5 to 15% based on the sum of the amount of the main material and the solid lubricant. If the amount added is below this range, it will be impossible to form a coating film with sufficient mechanical strength, and if it is above this range, the viscosity of the liquid will become too high during the production of this agent, making it difficult to uniformly coat the main material and solid lubricant. This is because it takes a long time to disperse the particles. As shown in the examples, it is not necessary to add only one type of solid lubricant used in the present invention, and even if two or more types are used, as long as the sum of their amounts is within the above range, Demonstrates sufficient mold release performance.

In addition to the white substances mentioned above, it is of course possible to add black solid lubricants such as graphite and molybdenum disulfide as long as the amount is small and does not impair the appearance of the product. Adding emulsion wax, silicone, or water-soluble silicone oil to this agent improves mold release performance. The reason for this is that these fill the pores in the paint film and vaporize during pouring to form a heat insulating layer, improving the heat insulation and plasticity of the paint film, and their addition improves mold release. . If this mold release agent is diluted with water to a concentration suitable for the application method,
Workability can be improved, and if necessary, it may be preferable to add a small amount of a surfactant or rustproofing agent, but the effect of the present invention does not change even with the addition of these agents. This mold release agent can be used not only for molten metal molding as already explained, but also as a mold release agent for die casting, low-pressure casting, and non-pressurized Al alloys, which place less burden on the mold release agent. It's possible.

Claims (1)

[Claims] 1. A water-soluble white mold release agent to be applied to an Al alloy casting mold, the main composition of which is one or more of mica, talc, and vermiculite; A binder made of an organic substance, a white or colorless solid lubricant having lubricity up to the decomposition temperature of the binder, and water, the solid lubricant having a weight of 0.1 to 2. 3
A mold release agent characterized in that the binder comprises 0.5 to 15% of the sum of the main material and the solid lubricant. 2. The mold release agent according to item 1 above, wherein the main component of the solid lubricant is one or more of boron nitride, carbon fluoride, and melamine cyanurate. 3. The mold release agent according to item 1 above, wherein the binder is an emulsion of glue, polyvinyl alcohol, dextrin, molasses, casein, and vinyl succinate.