JPH01205847A - Mold for casting - Google Patents

Abstract

PURPOSE:To improve castability and to use a mold for long term by forming ceramic layer to the surface of mold, metallic layer made of base metal of the mold or the base metal as main component to the back face and material, in which composition of these metals and ceramic are continuously changed, to the intermediate part. CONSTITUTION:The surface layer of the mold is formed with only ceramic and as going to the inner part, the content of the ceramic is made to less and the content of the base metal of the mold or the metal having the base metal as the main component is made to more, and the material made of only the base metal of the mold or the base metal as the main component is used to the back face. Therefore, the surface keeps low thermal conductivity of the ceramic and at the same time, the back face has the same coefficient of thermal expansion as the mold main body and by continuously changing the composition of the ceramic and the metal between the surface and the back face, thermal stress is released and the development of gap between the ceramic and the mold main body is restrained and the mold can be stably used for long term.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to casting molds, particularly for casting grids and parts for lead-acid batteries.

Conventional technology and its problems Conventionally, the casting of grids or parts for lead-acid batteries involves aligning a pair of cast iron mating molds engraved with the shape of the grid or parts with a mold release agent evenly applied to the surface. A common method is to pour molten lead alloy through a sprue provided at the top, allow the molten metal to cool and solidify, and then open the mating mold to remove the S artifact.

As is clear from the above-mentioned process, the necessary characteristics for a casting mold material are (1) good thermal shock resistance, sufficient mechanical strength, and little thermal distortion; (2) good flow of molten metal; (3) The M-type properties of the s relics are considered to be good.

The cast iron molds in use have solved the problem of thermal distortion by making the base material thicker and by modifying the machined surfaces so that the mold surfaces match during heating, but when used alone, they have poor glide and flow. Since the molten metal cannot fill every corner of the lattice shape carved into the mold, and the relics are difficult to release from the mold, a release agent is actually applied to the surface of the mold before use.

The mold release agent is used by dispersing cork fine powder and water glass in water, spraying or applying it uniformly to the mold surface with a spray gun or spatula, drying it, and sintering it at about 200 degrees Celsius. Since the layer has good heat insulation and air permeability, it is possible to fill every corner of the complex lattice shape with molten metal, and the cast material can be easily removed from the mold.

However, such mold release agents have practical problems in terms of heat resistance and adhesion, and the life of the mold release agent layer that is not formed is short. But 4-8
The mold release agent had to be reapplied every hour, which further worsened workability and caused problems in the dimensional accuracy of the resulting castings.

As a way to solve these difficulties, the use of ceramics for the entire mold or a part of the mold was proposed in the Tokuko Sho 5G-17.
178 and JP-A-5-7-124565. Although the method of JP-A-57-124565 is considerably improved compared to the conventional method, due to the difference in coefficient of thermal expansion between the ceramic and the base metal of the mold, the gap between the ceramic and the mold body may occur when used for a long period of time. Occasionally, gaps formed and required repair.

Means for Solving the Problems The present invention solves the above-mentioned problems, and its gist is that the surface layer is made only of ceramics, and as it goes inside, the content of ceramics is reduced, and the base metal of the mold or The surface maintains the low thermal conductivity of ceramics by increasing the amount of metal whose main component is the base metal and by using a material whose back side is only the base metal of the mold or a metal whose main component is the base metal. At the same time, the back side is the same v as the mold body! , m expansion rate, and by continuously changing the composition of the ceramics and metals between them to reduce thermal stress and prevent the formation of gaps between the ceramics and the mold body, it can be used stably for a long period of time. This is what made it possible.

Jitsuhokan example The present invention will be explained in detail below with reference to Examples.

Example 1. FIG. 1 is a perspective view of one side of a mold for casting a lattice body for a lead-acid battery according to the present invention.

In the figure, 1 is a cast iron mold, 2 and 3 are silicon nitride (s+, N 4 ) Fm on the surface, Si and N decrease as it goes inside, and iron (Fe) increases at the same time, and Fel on the back surface. 4 is a sprue part for injecting molten lead alloy, 5 is a runner through which high-temperature molten metal flows, 6 is a lattice part for a lead-acid battery, and 7 is a mold to be used oppositely. The matching bottle holes 8 are temperature regulating pipes for heating or cooling the mold.

Figure 2 shows the change in composition of the cross section of the material used for the burial mold.The surface is a ceramic layer, the back is a metal layer, and in the middle, these layers change continuously.For example, a material using the self-combustion method is used. It can be manufactured by

This mold is used with a conventional mold release agent applied to the surface carved with a cast iron grid.

However, it is also possible to apply a conventional mold release agent to the surfaces of Si, N2, and the like.

As mentioned above, the mold of the present invention can be used at high temperatures (approximately 450 to 500°C).
) The surface layer is SlsN a at the sprue part where the molten metal is injected and the runner directly below it, and SlsN a as it enters the interior.
This is a structure in which i and N are decreased, e is increased at the same time, and a buried mold whose back surface is made of a material made of Fe is arranged. Conventional molds have the disadvantage that the release agent layer, particularly in the sprue area where high-temperature molten metal is injected and the runner area immediately below, is susceptible to thermal deterioration and peeling.

Since this part has a simple shape and is small, it is easy to form a material without warping or distortion.

In order to improve the submerged flow, it is particularly effective to make the runners thicker in this area, and it is also effective to roughen the surface to improve heat insulation and air permeability.

The structure of the buried mold part can be devised so that it can be slid into the cast iron mold, or it can be fixed together with screws.

Next, the casting workability using the mold of the present invention shown in FIG. 1 was evaluated using a mold A that does not use a conventional ceramic investment mold and a material made only of Si, N, and ceramics in the investment mold part of FIG. Table 1 shows the results of comparing the mold B used.

Table 1 Note that the production yield of the grid refers to the number of grids that can be manufactured after application of the mold release agent until the next time the mold release agent needs to be reapplied.

The yield of the lattice body is similar to that of conventional mold B and is superior to that of conventional mold A. Furthermore, although the yield of the lattice body was excellent in the conventional mold B, it required repair every 6 to 9 months, but the mold according to the present invention could be used for more than 5 years without repair.

Example 21 Using a material in which the surface layer is made of boron nitride (8N), the content of BN decreases and the Fe − content increases as it goes inside, and the back surface consists of only Fe, the ball and inter-cell connections were made. We created molds for lead parts such as. Since the mold for lead parts is small and the above-mentioned materials are easy to manufacture, the above-mentioned materials were used not only for the sprue but also for the mold walls that form the parts. In addition, the surface of 88 was roughened by sandblasting using fine particles.

Table 2 shows the results of a comparison of the workability of casting parts using the mold according to the present invention with that when using a conventional mold.

Table 2 Lead parts often require excellent dimensional accuracy, and it is not possible to apply a large amount of mold release agent to the molds used to manufacture them, so mold release agent is frequently applied. I had to.

However, the surface of the mold according to the present invention is made of BN ceramics and has low thermal conductivity, and the roughening of the surface further improves heat insulation and air permeability, eliminating the need to apply a mold release agent and dramatically improving casting workability. Improved.

In addition, since the content of BN and Fe changes continuously from the 88 surface to the metal part, as in the case shown in Figure 2, the thermal stress caused by the difference in thermal expansion coefficient is alleviated, and the mold metal part and the surface ceramic There were no gaps between the parts, and it could be used stably for a long period of time.

These molds are used not only for casting grids and parts for lead-acid batteries, but also for casting other steel products, nonferrous metals such as aluminum, copper, zinc, and their various alloys, and injection molding molds for plastics. Application is possible.

It is also conceivable that it could be applied to mechanical parts that combine the properties of ceramics, such as i1 heat resistance and chemical resistance, with the properties of metals, such as high strength, high toughness, and high thermal conductivity.

In that case, the ceramic material is TiB, , 2rB
Borides such as 2°-B, nitrides such as AIM, 8N, VN, HoSi2. Silicides such as TaSi2, H
gS, chalcogen compounds such as WSe, A120s
, TtO2,S! Oxides such as Oi and their composite compounds, etc., have metal parts made of Fe, Cu, AI, N.
By using I and various other pure metals and various alloys thereof, it is possible to obtain 8-piece molds or machine parts depending on the purpose.

Effects of the Invention As detailed above, the casting mold according to the present invention not only has extremely excellent casting workability, but also can be used stably for a long period of time, and has great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of one surface showing an example of a mold for casting a lattice body for a lead-acid battery according to the present invention, and FIG. 2 is a diagram showing changes in composition in a cross section of the material used in the investment mold. 1... Cast iron mold, 2, 3... Buried mold, 4...
Sprue part, 5... Runway, 6... Lattice part, 7...
Pin hole, 8...Temperature control pipe

Claims (1)

[Claims] 1. The surface layer is made of ceramics, the content of ceramics is decreased as it goes inside, and the base metal of the mold or a metal whose main component is the base metal of the mold is increased, and the back side is the base metal of the mold or A casting mold characterized in that it uses a material consisting only of a metal whose main component is the base metal.