JPS602949B2 - die casting equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cold charcoal die-casting device having a cast sleeve with low thermal conductivity and excellent corrosion resistance and wear resistance.

Devices for die-casting zinc-based alloys, aluminum-based alloys, etc. are broadly classified into hot chamber die-casting machines and cold chamber die-casting machines.

The former has a built-in melting furnace and squirts a certain amount of molten metal into the mold from a mouth called a gooseneck to obtain castings, while the latter has a separate melting furnace and pours the molten metal from the spout into the sleeve with a tap. This is a mold that injects this into a mold. The former type is more advantageous because it prevents the formation of cavities in the casting and has better rolling properties. Therefore, when casting zinc-based alloys, for example, it is advantageous in terms of both the productivity and the physical properties of the molded product as described above. A hot chamber type die-casting machine is mainly used, but the melting point of aluminum-based alloys is higher than that of zinc-based alloys, which is about 660 qo or more, which is higher than that of zinc-based alloys, and it can severely corrode many metal materials. Due to these characteristics, the use of the advantageous hot chamber type die-casting equipment has been delayed, and the current situation is that the coal-chasovar-type die-casting equipment, which has inferior productivity and physical properties, is used. The reason why cold chamber type die-casting equipment is inferior in productivity is obvious from its mechanism and is not easy to solve, but the reason why the physical properties of molded products are inferior is that currently the casting sleeve of the equipment is made of SACM-1 (nitrided steel) or SKD-61 (alloy tool steel) or nitrided versions of these steels are used, and when the molten metal comes into contact with the wall of the casting sleeve, a portion of the molten metal is cooled and solidified, albeit locally. When the part is made and filled into the mold,
This is said to result in a non-uniform molded product with a mixture of molten metal and solidified parts.

Furthermore, as mentioned above, aluminum-based alloys violently corrode many metal materials and are subject to harsh operating conditions. Therefore, cast-in sleeves made of steel materials such as those mentioned above are subject to significant wear and tear due to corrosion and abrasion. ~Every 200,000 shots,
There was a problem in that the cast-in sleeve had to be replaced. As a solution to these drawbacks of conventional cast-in sleeves, sleeves made of materials such as ceramics, which have excellent corrosion resistance, wear resistance, and low thermal conductivity, have been developed.
A cold chamber type die-casting device having a casting sleeve with a molded sleeve (hereinafter referred to as a hot sleeve) encased inside has been proposed as an idea. However, the characteristics required for hot sleeves are: (1) Corrosion resistance against molten metals such as aluminum alloys.

■ Has excellent wear resistance.

■ Must have excellent oxidation resistance at high temperatures.

■ Low thermal conductivity and excellent heat retention.

■ Excellent thermal shock resistance that can withstand even when approximately 700 qo of molten metal is poured. ■ Excellent mechanical properties.

Until now, no material has been found that satisfies all of these characteristics, and thus a die-casting device with a hot sleeve has remained an idea and has not been put into practical use.

In particular, when making hot sleeves from ceramics, thermal shock resistance is often an issue, and attempts have been made to apply alumina-based ceramic hot sleeves. The hot sleeve cracked due to thermal shock when poured, making it unusable.

The object of the present invention is to provide a die-casting device equipped with a casting sleeve that has the above-mentioned properties and can withstand the casting of aluminum alloys.According to the present inventors, silicon nitride 70 A hot sleeve formed by molding and pseudo-solidifying a mixed powder consisting of ~99.8% by volume, 0.1-29.9% by volume of magnesium oxide, and 0.1-29.9% by volume of at least one kind of lanthanum group oxide. It has now been found that this object can be achieved by a die-casting machine having a casting sleeve provided with.

To explain the present invention in more detail, first, silicon nitride (
Si3N4) is not attacked at all by molten non-ferrous metals such as aluminum and zinc.

2. Hard and has excellent wear resistance.

3. Excellent oxidation resistance at high temperatures, hardly oxidized in air up to 1100°C.

4. Low thermal conductivity and good heat retention.

5 Extremely good thermal shock resistance.

It is a material that is extremely suitable for the hot sleeve of the injection cylinder of a die-casting machine, but it has the disadvantage that a molded body strong enough to withstand use cannot be bound by normal methods due to its poor anti-caking property. be.

For this reason, currently Si3N4 ceramic molded bodies are produced by hot press molding with the addition of a small amount of competitive striation accelerator, reaction firing method in which a molded body of metal Si powder is nitrided at high temperature and converted to Si3N4, It is obtained by adding an agent and condensing under normal pressure, but the hot press method has a drawback in terms of productivity, and the molded product obtained by the reaction competitive method has a porosity of about 20%. Another drawback is that the metal seeps into the interior, and the strength is low.

On the other hand, in the case of the atmospheric pressure Akyo silk method, if a conventional sintering accelerator such as alumina is used, a dense molded body cannot be obtained unless a large amount of this is added to the silicon nitride. There was a problem in that the excellent properties such as corrosion resistance and thermal shock resistance were significantly impaired by large amounts of additives.
However, when magnesium oxide and at least one type of lanthanum group oxide are simultaneously added to silicon nitride as a brazing accelerator,
In the case of condensation, even if the amount added is smaller than conventional ones, the densification is sufficiently good, so the molten metal does not seep in at all, and the unique properties of silicon nitride are maintained without being impaired at all. Moreover, it has the advantage of having sufficient strength.

The lanthanum group is a general term for 15 elements ranging from lanthanum with atomic number 57 to lutetium with atomic number 71.
Now, listing each element in numerical order: lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, promethium Pm, samarium Sm, europium E, ligadolinium G0, terbium Th, dysprosium Dy, holmium Ho, erbium Er, thulium Tm, ytterbium Yb, It is lutetium Lu. Most of these elements form trivalent oxides, but cerium mainly forms tetravalent oxides, and praseodymium Pr60, . Terbium Tb exists stably in the form TA07.
Any of these oxides can be used satisfactorily in the present invention, but the effect when using cerium dioxide Ce02 is great, and due to the synergistic effect with magnesium oxide, even a small amount of addition results in extremely good densification. Thus, in the die-casting apparatus of the present invention, the hot sleeve is made of silicon nitride 70~
99. Magnesium oxide is added to ol% as a competitive mackerel promoter.
．． 1-29. Wol% and at least one kind of lanthanum group oxide from 0.1 to 29. It is obtained by preforming a raw material mixed powder to which Wol% is added into a desired shape, and heating and brazing the preform to a temperature of 1600 to 1800 oo in a non-oxidizing atmosphere. The blending ratio of the raw material mixed powder and the pseudo-condensation atmosphere and temperature in the production of the hot sleeve are limited by the following reasons. First of all, in order to maintain the properties unique to silicon nitride, the total amount of additives added must be 30% or less, and if more than this amount is added, the sintered body will become denser. Although there is no change in the corrosion resistance, the corrosion resistance and thermal shock resistance are significantly impaired. In addition, in order to obtain a compact, high-strength molded product with low porosity, the total amount of the accelerator added should be 0. Magnesium oxide and lanthanum group oxide must each be added at 0.1 vol% or more, and the total amount of these added must be 0.1 vol% or more. is less than ol%, or the total amount added is 0. Even if the amount is above 0.1 vol.%, if either of the dawning accelerators is less than 0.1 vol.%, only a molded article with a high porosity can be obtained. The competitive atmosphere must be non-oxidizing in order to prevent oxidation of silicon nitride, and is particularly preferably a nitrogen or a mixed atmosphere of nitrogen and hydrogen. Further, the firing temperature must be 1,800 qo or less to prevent sublimation and decomposition of silicon nitride, and 1,600° C. or higher to ensure rapid progress of the firing.
The competitive setting promoters, magnesium oxide and lanthanum group oxides, do not necessarily need to be added in the form of oxides from the time of blending the raw materials, but may be added in the form of nitrates, etc., which change to oxides during the setting process. . In the present invention, such a case is also included in the bag, and in that case, the amount is blended so that when it is converted into an oxide, the amount as described above will be obtained. Next, an example of the structure of the ceramic hot sleeve of the present invention will be explained with reference to the drawings.

■ is a flange for attaching to the die plate,
It is a cast-in sleeve body made of steel, etc., which is equipped with Western hot water ○■ for pouring molten metal, and in addition to this, a ceramic hot sleeve made of the silicon nitride ceramics mentioned above is used as an inner cylinder and cannot be removed. It's ironclad. Similar to the pouring spout ■, the ceramic hot sleeve ■ is provided with a pouring spout ■ so that it almost coincides with the position of the western wound opening ■ after completion. Hot water is injected from the right side of the figure into a mold (not shown) on the left side by applying pressure with a plunger (not shown). Examples are given below. Of course, the present invention should not be limited to these examples. Example 1 A raw material powder prepared by mixing silicon nitride, magnesium oxide, and various lanthanum group oxides in various amounts was molded using a rubber press, and heated and phosphorized at 1700°C for 1 hour in a nitrogen atmosphere to form an outer mold of 900 mm and an inner diameter of 600, length 100 The fastener was obtained.

This competitive body was put into 70,000 A molten metal from room temperature, held for 1 minute, taken out, and cooled to room temperature with compressed air, repeating a rapid heating/cooling cycle to determine whether cracks would occur due to thermal shock. I looked into it. For comparison, similar tests were conducted in the case where the composition was outside the scope of the present invention and in the case of an alumina dawn stripe. Table 1 shows the composition of the test specimen and the results of the thermal shock test. Table 1 Example 2 Silicon nitride 95 vol%, magnesium oxide ol%, 2
After rubber press molding a mixed powder consisting of cerium oxide (ol%), it was heated and sintered at 1,750 °C in a nitrogen atmosphere for 1 hour to obtain a hollow cylindrical feeder with an outer diameter of 600 mm, an inner diameter of 450 mm, and a length of 60 mm. Ta.

Stand this composite body on asbestos and put 700qo inside it.
of aluminum molten water was poured into the tank, and the temperature change over time was measured at three points below the top and five points inside from the inner wall. For comparison, the same test was also conducted on a cylinder of the same size made from SKD61. In the case of SKD61, the temperature decreased by 50°C within 3 seconds after injection, and the temperature continued to decrease rapidly thereafter, whereas in the case of silicon nitride ceramic, the temperature decreased by only 20°C even after sand 4. It has been found that by using this as a hot sleeve in a casting machine, it is possible to eliminate the situation where the cooled and solidified part and the molten metal are injected into the mold as a mixture. Ta.

Example 3 The casting cylinder shown in the attached diagram, which was equipped with a hot sleeve molded and solidified using the same composition and the same method as Example 2, was inserted into a die-casting machine with a mold clamping force of 80 tons to perform die-casting of aluminum alloy. .

While the conventional die-casting machine reached the end of its life after 100,000 to 200,000 shots, the die-casting machine of the present invention shows almost no wear or damage to the hot sleeve even after 200,000 shots, and can continue to operate. It was possible.

[Brief explanation of drawings]

The drawing is an illustration of a cast sleeve with a hot sleeve made according to the present invention. 1... Cast sleeve body, 3, 6... Western wound, 4
…hot sleeves.

Claims (1)

[Scope of Claims] 1. Molding a mixed powder consisting of 70 to 99.8 vol% silicon nitride, 0.1 to 29.9 vol% magnesium oxide, and 0.1 to 29.9 vol% of at least one kind of lanthanum group oxide, A die-casting device characterized by having a cast-in sleeve fitted with a sintered hot sleeve having low thermal conductivity and excellent wear resistance and corrosion resistance. 2. The die casting apparatus according to claim 1, wherein the lanthanum group oxide is cerium dioxide (CeO_2).