JPH05132752A - Method for thermally spraying ceramic on casting mold - Google Patents

Abstract

PURPOSE:To produce a casting mold without need for a facing in casting by applying a thermally sprayed ceramic film rich in resistance to thermal shock on the contact surface of the mold with molten metal. CONSTITUTION:The surface of the matrix (a) of a casting mold is blasted, and then a metallic material (alloy consisting essentially of aluminum and chromium) is thermally sprayed to form a metal layer (b). A mixture of the metallic material and a ceramic (yttria-stabilized zirconia) is thermally sprayed on the layer (b) to form a cermet layer (c). A ceramic is thermally sprayed on the layer (c) to form a ceramic layer (d). Consequently, a casting mold without need for a facing is obtained, casting is simplified, the production capacity is improved, and a stabilized-quality product is obtained.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic spraying method for forming a ceramic sprayed coating suitable for a casting mold and a jig attached to the casting mold (both of them are called a mold).

2. Description of the Related Art In the conventional die casting method, the die is applied to the die after every casting or every casting for the purpose of preventing seizure of the die and molten metal, releasing the casting, improving the material of the casting, etc. The mold is done. When this coating is performed, a coating device for the mold and a kneading and drying device are required, and a device for removing the coating material from the casting is also required, which leads to an increase in equipment and processes. Also, in order to overcome casting defects caused by the strength, drying properties and cooling rate of the casting material, the selection of the type of coating material, the thickness of the coating material, etc. has become an important know-how and very strict management is required. Has been done. On the other hand, the ceramic spraying technique is a commonly used technique and is widely used. However, up to now, no examples have been found applied to casting molds. The reason for this is that the thermal spray coating cannot withstand the thermal shock due to repeated use at a very high temperature of about 1400 ° C. and peels off.

DISCLOSURE OF THE INVENTION According to the present invention, a ceramic spray coating is applied to a mold to make it a permanent coating type, thereby eliminating the coating type work performed for each casting and managing the above-mentioned coating type. The aim is to solve the problems, shorten the casting process, reduce the equipment, and improve the product quality.For this reason, the heat insulation and thermal shock resistance greatly exceed those of conventional products, and the severe conditions during casting The present invention provides a method for forming a ceramic sprayed coating capable of withstanding heat.

As a result of earnest research to solve the above problems, the inventor has completed a mold that can be cast without a coating material by applying a special ceramic spray coating on the molten metal contact surface. It was done. Therefore, when this mold is used, a cast product made of a good material can be obtained due to the heat insulating property of the ceramic, and the dense structure of the ceramic sprayed coating prevents seizure of the mold and the molten metal, and also allows the mold to be released from the mold. A great effect was obtained. As the ceramic spraying method for the die of the present invention, any method such as gas spraying, plasma spraying, reduced pressure plasma spraying, etc. is used, and the heat-insulating and heat-resistant properties of the multi-layer spraying or concentration gradient spraying method on the molten metal contact surface of the die. It forms a ceramic sprayed coating with excellent impact properties.

The ceramic sprayed coating according to the method of the present invention has a cermet sprayed layer or a metal-ceramics grading layer,
By selecting the materials for forming these and setting the film thickness, the heat insulation and thermal shock resistance are dramatically improved compared to conventional dies, and thus it was impossible until now. A ceramic sprayed coating that can withstand the use of a casting mold is obtained.

EXAMPLES Various elements constituting the method of the present invention will be described below. 1. As the thermal spray material, there are various materials for each purpose, such as metal, ceramics, composite material of metal and ceramics (hereinafter referred to as cermet), and physical properties and chemical properties depending on the difference of these materials. There is a big difference. In the present invention, it is necessary to select a thermal spraying material whose characteristics meet the usage conditions of the mold, the usage conditions of the mold differ depending on the casting purpose such as the type and shape of the casting, and the combination of the spraying materials is a metal. , The most suitable for each of ceramics and cermet. 2. The thermal spray coating needs to have a certain thickness in order to obtain a heat insulating effect, and it is necessary to change the thickness depending on the type and size of the casting. Further, since the thermal spray coating intermittently contacts the high temperature molten metal, it is necessary to prevent peeling due to thermal shock. In the present invention, a metal spray layer, a cermet spray layer, and a ceramic spray layer are coated in this order on the surface of the mold base material, or a multilayer spray coating, or a concentration gradient spray coating that gradually shifts from the metal spray layer to the ceramic spray layer. It is a thing. It is desirable that the thickness of the sprayed coating be uniform in every part of the mold, and the cermet sprayed layer can be formed of a plurality of layers depending on the application. 3. As a thermal spraying method, the present invention is carried out by using any facility such as gas thermal spraying, plasma thermal spraying, reduced pressure plasma thermal spraying and the like. The attached drawings show a cross-sectional view in which a sprayed layer is formed on a mold, and FIG. 1 shows multilayer spraying, in which a metal sprayed layer b, a cermet sprayed layer c, a ceramic are formed on the surface of a mold base material a. This is a method of forming a sprayed layer in the order of the sprayed layer d. FIG. 2 shows concentration gradient thermal spraying, in which the lowermost layer is 100% metal and the uppermost layer is 100% ceramic material on the surface of the mold base material a by gradually changing the mixing ratio of the two. This is a method of forming the transitional layer e. This concentration gradient thermal spraying method has an advantage over the multilayer thermal spraying method in that it is less likely to peel off and the thermal spraying process is shortened. However, since the thermal spraying equipment becomes complicated and the thermal spraying is difficult depending on the size of the mold, which method should be selected must be decided depending on the cost and the type of the mold. FIG. 3 is an embodiment diagram, and the surface to be sprayed of the mold (1) is subjected to a blast treatment so that the spray material is easily adhered. Blast powder is applied to the mold (1) so that the surface to be sprayed is evenly polished. After completion of this cleaning, it is confirmed that no impurities are attached to the surface to be sprayed. Next, the mold (1) is set in the plasma spraying machine, and the metal material (alloy mainly consisting of nickel, aluminum and chromium) is sprayed until the set thickness is reached to form the metal sprayed layer (2). A material obtained by mixing a metal material and a ceramic material (yttria-stabilized zirconia) in a fixed ratio is sprayed thereon to form the first intermediate layer (3). Further, the ceramic material is sprayed with the mixing ratio of the metal material and the ceramic material being higher than that of the first intermediate layer to overlap the second intermediate layer (4), and finally only the ceramic material is sprayed to spray the ceramic sprayed layer (5). ) Is formed to complete the thermal spray coating. Argon is used as the primary gas and hydrogen is used as the secondary gas for this thermal spraying, and the mold is preferably rotated so as to obtain a uniform coating surface.

A. By using a ceramic sprayed mold, it is not necessary to apply a mold to the mold, and there is no need for a mold material, a facility for making a mold material, and a facility for removing a mold material. (2) The mold coating process and mold material removing process in the casting process are not required, and productivity can be improved. C. Since the coating type is not required, the variation of the coating type for each casting is small and the management thereof is not required. D, casting defects (sand scum, blown, etc.) due to the coating mold can be eliminated. E, Product quality fluctuations due to variations in coating material thickness are eliminated. F. Since the mold coating material is not used, dust is not generated by the mold coating material, and it is possible to purify the air in the factory and prevent the machinery from being contaminated. It has various effects.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a coating formed by a multi-layer thermal spraying method. FIG. 2 is a cross-sectional view of a coating formed by the concentration gradient spraying method.
FIG. 3 is a cross-sectional view of a film formed according to the example.

[Explanation of symbols]

 (1), a ... Mold base material (2), b ... Metal sprayed layer (3) ... First intermediate layer (4) ... Second intermediate layer (5), (d) ... Ceramic sprayed layer (E) ... Metal-ceramics graded layer

Claims (2)

[Claims] 1. A mold for casting which does not require a coating mold at the time of casting and a jig attached to the mold, characterized in that a ceramic sprayed coating having a high thermal shock resistance is applied to the molten metal contact surface. 2. A ceramic spraying method suitable for a casting mold and a jig attached to the casting mold, wherein a ceramic sprayed coating having a high thermal shock resistance is applied to the molten metal contact surface and a coating mold is not required at the time of casting.