JPH0241736A - Metallic mold for molding shell mold - Google Patents

Abstract

PURPOSE:To improve wear resistance and to drastically improve the number of times of molding by providing surface treating film of Ni-based metal on the surface of a metallic mold in the metallic mold for molding shell mold composed of the prescribed concn. range of Zr and the balance of Cu. CONSTITUTION:Since the metallic mold for molding the shell mold composed of 0.01-0.3wt.% Zr and the balance of copper has large heat conductivity, heat is uniformly transmitted to the whole metallic mold. The surface treating film of Ni-based alloy formed on the surface of this metallic mold is sufficiently adhered to the metallic mold surface and also is harder than the above copper alloy. It is preferable that the thickness of the surface treating film is made to 20-50mum and it is effective that Ni-based metal for this surface treating film uses Ni or phosphorus-containing Ni. In such a manner, since the surface treating film is hard, this has excellent wear resistance and the number of times of molding is drastically improved and since this is difficult to be peeled off, the excellent metallic mold for molding is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold for making a shell mold that requires wear resistance.

[Conventional technology]

The mold for making shell molds is manufactured by firing shell sand that is supplied with compressed air and filled with compressed air to form shell molds.
It is used after being heated to a temperature of about 50 to 350°C. Conventional molds for making shell molds are made of cast iron or steel, but because these molds have low thermal conductivity, the following problems (a) to (d) occur when using these molds: There was a point.

(a) Many firing irregularities occur in the fired shell mold.

(b) The mold is thermally strained and the shell mold is deformed.

(c) It takes a lot of energy and time to heat the mold to a predetermined temperature.

(d) Shell mold productivity is low.

In order to overcome the above problems, Japanese Patent Application Laid-Open No. 61-27964
As described in Japanese Patent No. 9, a copper alloy was provided consisting of 0.01% by weight zirconium and the balance copper. This copper alloy has high thermal conductivity, so the entire mold can be easily heated to a predetermined temperature, and the mold hardly has any uneven heating. Furthermore, since the mold does not undergo thermal distortion, the shell mold is hardly deformed, and the entire mold can be heated to a predetermined temperature in a short time, so energy consumption can be saved.

[Problem to be solved by the invention]

However, this copper alloy mold has a problem in that it is easily abraded by shell sand supplied by compressed air.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems and to provide a mold for making shell molds made of prepared alloy which has wear resistance.

[Means to solve the problem]

In order to achieve the above object, the shell mold making mold of the present invention contains 0.01 to 3.0% by weight of zirconium, and the rest is copper, and the surface of the mold is treated with a nickel-based metal. It is equipped with a membrane.

The thickness of this surface treatment film is preferably 20 to 50 μm, and it is effective to use nickel or phosphorus-containing nickel as the nickel metal for this surface treatment film.

[Effect]

A mold for making a shell mold containing 0.01 to 3.0% by weight of zirconium and the remainder made of a copper alloy has high thermal conductivity, so heat is evenly transmitted throughout the mold. The nickel-based metal surface treatment film formed on the surface of the mold adheres sufficiently to the surface of the mold and is harder than the copper alloy.

If the zirconium content in this copper alloy is less than 0.01%, the cyclic thermal fatigue strength will not increase, and if it exceeds 3%, the castability will deteriorate and the yield will deteriorate, and further improvement in the thermal fatigue strength will not be possible. I can't get it. Therefore, the zirconium contained in the copper alloy is 0.01 to 3.0% by weight.
shall be. Preferably, it is 0.03 to 3.0%.

In addition, the thickness of the surface treatment film provided on the surface of the mold is 20 μm.
If it is thinner than 50 m, the wear life of the mold surface will be shortened.
If it is thicker than Pm, the plating may peel off or the dimensional accuracy will decrease, so it is preferably 20 to 50 μm.

As a nickel-based metal for the surface treatment film, nickel or phosphorous-containing nickel reduces the decrease in thermal conductivity of the mold and increases wear resistance.

〔Example〕

Embodiments of the present invention will be described with reference to FIGS. 1 to 8.

As for the material of the mold of the first example, as shown in Table 1, sample Nα1 is the mold of the invention material, and nickel is coated on a copper alloy containing 0.3% by weight of zirconium to a thickness of 20 to 50 μm. They were electrolytically plated, and Nα2 to Nα8 are comparative materials. N
α2 to Nα5 are those using the above-mentioned copper alloy, Nα2 is the one using electroplated chromium to a thickness of 20 to 30 μm, and Nα2 is the one using the above-mentioned copper alloy.
α3 is a mold with a tin diffusion coating applied to a thickness of 15 to 25 μm, No. 4 is a mold coated with tungsten sprayed to a thickness of 2° to 30 μm, and No. 5 is a mold without surface treatment. No. 6 is for normal cast iron (FC25) back mold, Nα7 is for spheroidal graphite cast iron (FCD45) back mold,
Note that 8 is for the copper (SKD61) back mold, and Nα6
-8 also had no surface treatment.

The results of actually measuring the Vickers hardness of the surface of each mold are shown in Table 2. The Pinkers hardness of the inventive material Nα1 sample was 700, which was a good value, and Nα2 showed an even better result.

Table 2 Note that Nα1 to Nα4 are the hardnesses of the surface-treated portions.

Each of these molds was heated from the back with a gas burner under certain conditions, and the heating time and the temperature of the mold's inner surface at that point were measured, and Figure 2 shows the state of temperature change. .

From Figure 2, when the shell sand firing temperature is 320°C, the heating time for the inner surface of the mold to reach that temperature is 70 to 80 minutes for conventional iron molds (Nα6 to 8). On the other hand, Nα1 is about 30 minutes, which indicates that the mold made of the invention material has excellent thermal conductivity.

Next, the relationship between the temperature of the inner surface of the mold and the amount of strain in the mold was investigated. As shown in Figure 3, 400 rIn vertically and 600 rIn horizontally.
The back side of a mold with a thickness of 100 mm was heated, the deflection generated in the mold was measured as the amount of distortion in the mold, and the relationship between the amount of distortion and the temperature of the inner surface of the mold was shown. is shown in Figure 4. The amount of strain at the specified temperature of 320℃ is (
For Nn6-8), it is 0.4 mm or more, whereas Nα
1 and Nα5, there is almost no distortion. In other words, it can be seen that there is almost no strain in both cases where the copper alloy is subjected to nickel surface treatment and when no surface treatment is applied. This is because the better the thermal conductivity, the smaller the temperature difference between the heated surface and the inner surface, the smaller the difference in the amount of superthermal expansion with a smaller temperature difference, and the smaller the amount of distortion. If the amount of strain is 0.31 or more, when shell sand is blown into the mold, the shell sand will blow out from the mating surfaces of the mold, which poses a problem in use.

Further, among the molds mentioned above, Table 3 shows the temperature of the inner surface when the back side of the mold made of the invention material Nα1 and the ordinary cast iron mold Nα6 was heated to 5o to 350°C with a gas burner.

Table 3 From Table 3, it can be seen that at Nα1, there is almost no temperature difference between the back side and the inner side, and the amount of strain is small.

2nd Example Made of each material shown in Table 1, length: 400 mm, width: 6
00mm, thickness 100mm was made, 2.5 to 3
．． Shell sand was blown at a pressure of 0 kg/cJ and blown into the mold. After producing 1000 shell molds using this method, the amount of wear on each mold was measured. The results are shown in FIG. It can be seen that the mold of the present invention (Nα1) has as little wear as the copper alloy mold (Nα2) with chromium surface treatment and is superior.

3rd Example A mold made of the material shown in Table 1 (Nα1 to 7) with a length of 10 mm
, or - A mold with a side of 10 mm and a length of 50 mm was subjected to an abrasion test and a surface peel test.

The abrasion test was carried out using the apparatus shown in Figure 5, in which mixed water containing 5% by weight of silica sand was placed in the alluvial sand tank 2, and the test piece 3 was rotated in the tank at a circumferential speed of 10 m/=8 seconds by the electric motor 1. After 13 and 25.50 hours, the abrasion weight of each test piece was measured. The results are shown in FIG. Regarding the type of surface treatment, nickel electrolytic plating (Nα1) and chrome electrolytic plating (Nα2) have almost the same wear weight, while tin diffusion coating (N(13) and tungsten spraying (Nα4)
is better than the case of

Furthermore, in comparison with conventional mold materials, in the case of Nα1, which is made by electrolytically plating a copper alloy with a thickness of nickel of 20 to 50 μm, it wears more than ordinary cast iron (Nα6) and spheroidal graphite cast iron (Nα7). Next, in the surface peel test, in order to eliminate the influence of the binder and mold release agent contained in the shell sand when molding the shell mold, Nα1~5 of the above test piece was The sample was heated to 300'C, held, coated with a release agent and blown with shell sand, and the heating and cooling cycle shown in FIG. 7 was repeated to examine the releasability of the surface treatment film. As a result, chrome electrolytic plating (
In the case of the surface treatment films of Nα2), tin diffusion coating (N(13), and tungsten spraying (Nα4), it peeled off after 3 to 6 cycles, while the surface treatment film of nickel (Nα1) peeled off even after 500 cycles. There was no peeling.

The reason why there is less peeling in the case of nickel surface treatment is that the coefficient of thermal expansion of nickel (1,279X 10-5/'C) is larger than that of chromium (0,82X 10-5/'C). The difference from the coefficient of thermal expansion (1,86X 10-'/'C) of a copper alloy containing 3% by weight of zirconium is small;
Therefore, the tensile thermal stress generated in the surface treatment film due to the difference in thermal expansion coefficient becomes smaller, and the force for peeling the surface treatment film becomes smaller, so it is thought that this is because it is strong in thermal fatigue strength due to repeated stress and becomes difficult to peel off.

Figure 8(B) shows the case of chromium electrolytic plating (Nn2) in which a peeling part 7 is seen at the interface between the copper alloy 4 and the surface treatment film 5, and the case of nickel electrolytic plating with no peeling seen in Figure 8(A). A microscopic photograph of the metal structure of the cross section of the mold is shown for the case of the copper alloy 4 which has been subjected to the surface treatment film 5 by plating.

Combining the first to third examples above, the case where the copper alloy containing 0.3% by weight of zirconium is subjected to nickel surface treatment has less thermal distortion and is superior in both wear resistance and molding frequency. Moreover, since there was no peeling of the surface treatment film, it is considered to be the most excellent.

Furthermore, after forming a nickel surface treatment film on the copper alloy, 3
It was found that heat treatment maintained at 50 to 450°C for about 1 hour was as good as or better than the case without heat treatment.

Note that when the copper alloy is surface-treated with phosphorus-containing nickel by electroless plating, hard compounds such as Ni and P are present in the nickel matrix, so the same effect as in the case of nickel surface treatment (Nα1) is obtained. It was confirmed that it has. In this case, the phosphorus content is preferably 8 to 10% by weight.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

Shell casting molds made of copper alloy containing 0.01 to 3.0% by weight of zirconium and surface-treated with nickel-based metals have a hard surface treatment film and are excellent in wear resistance, making it possible to reduce the number of molding cycles. This is dramatically improved, and since the boundary between the copper alloy and the surface treatment film is difficult to peel off, an excellent mold for making shell molds can be obtained.

Then, the thickness of the surface treatment film provided on the surface of the mold was set to 20~
By setting the thickness to 50 μm and by using nickel or phosphorus-containing nickel as the nickel-based metal for the surface treatment film, the above effects become even more remarkable.

[Brief explanation of the drawing]

Figure 1 shows 100% shell sand applied to the molds of the invention material and comparative material.
This is a graph showing the results of measuring the wear amount of each mold when blowing up to 0 times, and Figure 2 shows the test results regarding heating time and mold temperature when heating from the back side of the mold with a gas burner. FIG. 3 is an explanatory diagram showing the method of measuring the amount of strain during heating of the mold, and FIG. 4 shows the test results regarding the temperature and amount of strain of the mold in the heating test of the mold. FIG. 5 is a partial cross-sectional view showing the schematic structure of the wear amount measuring device, FIG. 6 is a graph showing the wear test results of molds using the invention material and comparative material, and FIG. 7 is a graph showing the surface FIG. 8(A) is an explanatory diagram showing heating and cooling cycles in a peel test of a treated film, and FIG. FIG. 8(B) is a photograph showing the metal structure of the cross section of the mold where the chromium electroplated film of the comparative material has peeled off from the copper alloy. 5...Surface treatment film

Claims (1)

[Claims] 1. A shell mold making mold comprising 0.01 to 3.0% by weight of zirconium and the remainder being copper, characterized in that a surface treatment film of a nickel-based metal is provided on the surface of the mold. Molding mold. 2. The shell mold making mold according to claim 1, wherein the surface treatment film has a thickness of 20 to 50 μm. 3. Claim 1 or 2, wherein the nickel-based metal is either nickel or phosphorous-containing nickel.
The mold for making shell molds described in .