CN1299857C - Deoxidation casting method and deoxidation casting equipment - Google Patents

Abstract

The deoxidation casting method of the invention can deoxidize the oxide film formed on the surface of the molten metal, improve the wettability with the inner surface of the casting model cavity, and cast high-quality products with high casting efficiency. The deoxidation casting method comprises the following steps: reacting a deoxidizing compound produced by reacting a metal gas and an inert gas with molten metal; the oxide film on the surface of the molten metal is deoxidized.

Description

Deoxidation Casting, Aluminum Casting and Foundry Equipment

technical field

The present invention relates to deoxidation casting, aluminum casting and a casting equipment.

Background technique

Many casting methods are known, such as gravity casting, low pressure casting, die casting, squeeze casting, thixocasting. In any of the casting methods, molten metal is poured into a cavity in a casting pattern, solidifying the metal into a predetermined shape. The casting method can be selected according to the material of the molten metal and the product to be cast.

Many kinds of products are cast products. In the case of casting products with complex shapes or high performance, it is necessary to ensure that the cavity is filled with molten metal, does not form casting defects, achieves the specified strength, prevents deformation, and has a good shape.

Aluminum and aluminum alloys are widely used as molten metal materials. When aluminum is cast, aluminum is easy to form an oxide film. Due to the formation of an oxide film on the surface of the molten aluminum, the surface tension of the molten metal becomes greater, thereby reducing the fluidity and welding properties of the molten metal, and sometimes causing casting defects. In order to solve these shortcomings, improvements in many aspects have been studied, such as lubricants, pouring methods, pouring speed, and pouring pressure.

For example, in gravity casting and low pressure casting, the temperature drop of the molten metal can be slowed down by applying a heat-insulating release agent, adjusting the gate arrangement, etc., thereby suppressing poor flow of the molten metal caused by the formation of an oxide film on the surface of the molten metal, Shrinkage, cold insulation and other defects. In die casting, by adjusting the pouring speed, pouring pressure, gate arrangement, etc., molten metal can be filled in a short time under high pressure. In squeeze casting, the vibration pressure can be greatly increased in its gravity casting stage, so that the oxide film can be broken and melted.

However, there are some shortcomings in the conventional casting method, and there is no perfect method at present. In particular, the oxide film formed when the molten metal contacts the inner surface of the casting mold cavity will form cracks and cold shut phenomena on the product surface, and the oxide film prevents the molten metal from being fully filled into the mold. In the case of castings of aircraft and motor vehicles, the surface stress and damaged parts will seriously affect the safety, etc., so it is necessary to use the fluorescent flaw detection method to inspect each casting product. Therefore, the manufacturing cost of the product must be high. Furthermore, the quality and reliability of the product cannot be guaranteed.

Oxide film problems also arise not only in the casting of aluminum, but also in the casting of other materials.

Contents of the invention

The purpose of the present invention is to solve the problems caused by the oxide film produced on the surface of molten metal.

An object of the present invention is to provide a method of deoxidation casting, which can prevent the formation of oxide film on the surface of molten metal, improve its wettability to the inner surface of the casting mold cavity, and can cast high-quality castings with high casting efficiency. quality product.

A second object of the present invention is to provide deoxidizing casting equipment for carrying out the above method.

Deoxidation casting method of the present invention comprises the following steps:

Reacting a deoxidized compound formed by reacting a metal gas with an inert gas with molten metal;

Deoxidizes the oxide film on the surface of the molten metal.

The metal used for the metal gas is selected according to the molten metal. For example, magnesium nitride (Mg ₃ N ₂ ) formed by the reaction of magnesium gas and nitrogen gas can be used as an effective deoxidizing compound that deoxidizes the oxide film formed on the surface of molten metal. Magnesium is stable from room temperature to high temperature and readily sublimes. Therefore, magnesium is suitable for this method. The high deoxidation performance of the magnesium nitride compound can effectively deoxidize the oxide film on the surface of the molten metal.

The deoxidation casting of the present invention relates to a method capable of deoxidizing the oxide film formed on the surface of molten metal to produce pure molten metal. Therefore, in the case of casting with a molten metal that easily forms an oxide film, the method of the present invention can effectively deoxidize the oxide film and perform casting with a pure molten metal well.

By deoxidizing the oxide film on the surface of the molten metal, the surface tension of the molten metal is lowered, the fluidity is improved, and its wettability to the inner surface of the cavity of the casting mold is also improved. Since the pure molten metal contacts the inner surface of the cavity, it can flow easily in the casting mold, that is, the flow performance of the molten metal is improved, and it can ensure that the molten metal is filled into the cavity until its small space.

In one conventional casting method, a lubricant or an insulating mold release agent is used to maintain the casting pattern at a high temperature, thereby maintaining the fluidity of the molten metal. In the method of the present invention, the fluidity of the molten metal is higher, and no lubricant or heat insulating release agent is required. Therefore, the manufacture and adjustment of the casting model is more convenient, and the casting efficiency is higher.

In conventional casting methods, the casting mold is heated to a high temperature to maintain the fluidity of the molten metal. Pouring molten metal into a heated casting mold. The molten metal is solidified by cooling the model. In the method of the present invention, however, the fluidity of the molten metal is high, so it is not necessary to heat the casting mold. Therefore, the molten metal can be solidified in a short time, and the product can be quickly solidified to obtain a product with high toughness, which can prevent the deformation of the product such as sink mark and elongation, so the product quality is high. Casting patterns can be used at room temperature.

In conventional gravity casting, a feeding riser is formed in the casting mold, and molten metal is introduced from the feeding riser into the cavity by its own weight. In the present invention, the fluidity of the molten metal in the casting mold is high, so the volume of the feeding riser can be reduced. In a conventional model, the volume of the feeding riser accounts for 50-60% of the model volume. In the method of the present invention, due to the high fluidity of the molten metal, the volume of the feeding riser can be reduced to only 10-20% of the volume of the casting model. Therefore, molten metal can be effectively used, and casting patterns can be easily produced. By reducing the volume of the feeding riser, the solidification of the molten metal can be accelerated, the casting cycle can be shortened, and the casting efficiency can be improved. Moreover, in the present invention, the product is easily separated from the casting model, so the product can be taken out quickly and the casting efficiency is improved.

There are two methods of reacting the molten metal with the deoxidizing compound in the casting mold cavity. A method includes the steps of: forming a deoxidizing compound outside a casting pattern; introducing the deoxidizing compound into a cavity; and pouring molten metal into the cavity. Another method includes the steps of: forming a deoxidizing compound in a casting mold cavity; pouring molten metal in the cavity.

Deoxidizing compounds are deposited on the inner surfaces of the cavity, causing them to react with the molten metal. In order to efficiently deposit the deoxidizing compound on the inner surface of the mold cavity, the metal used for preparing the deoxidizing compound is evaporated to obtain a metal gas, which is reacted with an inert gas such as nitrogen.

The deoxidizing compound can be introduced into the cavity from the outside, and can also be formed in the cavity. In the cavity, there should be an oxygen-free atmosphere first, so as not to reduce the deoxidizing function of the deoxidizing compound. The way to generate an oxygen-free atmosphere is to first pump air into the mold cavity, and then pass in an inert gas to purge the air away.

The method of the present invention can be suitably used for the casting of aluminum or aluminum alloys as molten metal. In aluminum casting, the oxide film formed on the surface of molten aluminum can be easily deoxidized by reacting magnesium nitride produced by the reaction of magnesium gas and nitrogen gas with molten aluminum. In the case of aluminum casting, an oxide film tends to form on the surface of molten metal. By deoxidizing the oxide film with magnesium nitride, high-quality products can be manufactured.

In aluminum casting, there are also two methods of reacting molten metal and deoxidizing compounds in the casting mold cavity. One method comprises the steps of first reacting magnesium gas and nitrogen to form magnesium nitride; introducing the magnesium nitride compound into a cavity; and pouring molten metal into the cavity. Another method includes the steps of: separately introducing magnesium gas and nitrogen gas into a casting mold cavity to form a magnesium nitride compound; pouring molten aluminum in the cavity. Magnesium nitride compound is a deoxidizing compound that is deposited on the inner surface of a cavity containing a core into which molten aluminum is poured. When the molten aluminum contacts the inner surface of the cavity, oxygen is removed from the oxide film on the surface of the molten aluminum through the deoxidation function of the deoxidizing compound, so that the surface of the molten aluminum becomes pure aluminum.

When the molten aluminum contacts the inner surface of the cavity, the oxide film formed on the surface of the molten aluminum is removed by deoxidation, thus preventing shrinkage and surface defects formed on the surface of the product. Especially when casting products with complex shapes, it was not possible to eliminate surface defects in the past. However, with the method of the present invention, excellent products without surface defects can be cast due to the high wettability and capillarity of pure molten aluminum.

In the case of producing magnesium nitride in a cavity, magnesium gas is first introduced into the cavity, and then nitrogen gas is introduced therein. Magnesium is produced by heating magnesium in an inert gas such as argon or a deoxygenated gas such as hydrogen until the magnesium sublimes. Magnesium gas is introduced into the cavity. Magnesium gas is introduced with a non-oxidizing carrier gas. Properly adjust the pressure and flow of the carrier gas. The carrier gas is preferably an inert gas such as argon. After magnesium is sublimated at 700-850°C, magnesium gas can be easily introduced into the cavity by means of carrier gas.

When magnesium gas is introduced into the cavity, the cavity should be in an oxygen-free atmosphere. In order to generate an oxygen-free atmosphere, the cavity can be pre-evacuated or purged with nitrogen. After removing the oxygen in the cavity, the magnesium gas is uniformly introduced into the cavity.

After magnesium gas is introduced into the cavity, nitrogen gas is then introduced into the cavity to form a magnesium nitride compound. The magnesium nitride compound is mainly deposited on the inner surface of the cavity in powder form.

When feeding nitrogen into the cavity, properly adjust the pressure and flow of nitrogen. In order to promote the reaction of nitrogen and magnesium gas, nitrogen can be preheated to heat the casting mold. The reaction time can be 5-90 seconds. If the reaction time is too long, the temperature of the casting model will drop, so the appropriate reaction time is 15-60 seconds.

When injecting nitrogen gas into the mold cavity to prepare magnesium nitride, it is important to prevent the magnesium nitride from reacting with the casting model. Because the molten metal will directly contact the inner surface of the cavity, the surface condition of the molten metal has a great influence on the surface condition of the product. Therefore, the deoxidation effect of the magnesium nitride compound must act on the inner surface of the cavity.

The inner surface of the cavity should not react with the magnesium nitride compound. If there are oxygen radicals etc. which easily react with the magnesium nitride compound on the inner surface of the cavity, the deoxidation function is lost before the molten metal is poured into the cavity. Therefore, it is not suitable to coat oxidized materials such as lubricants and release agents on the inner surface of the cavity. A non-oxidizing material such as graphite can be coated on the inner surface of the cavity. It is also possible to expose the metal surface to the inner surface of the cavity without applying a lubricant or the like. Exposed metal surfaces may be heated or nitrided. When the magnesium nitride compound exists on the inner surface of the cavity, molten metal is poured into the cavity, and the magnesium nitride compound on the inner surface of the cavity reacts with the molten metal to remove oxygen from the oxide film, that is, to deoxidize the oxide film. Through this reaction, the wettability of the molten aluminum is increased, the fluidity on the inner surface of the cavity is higher, and the capillary phenomenon is effective. Since the surface of the molten metal has become pure aluminum, the product has an excellent shape without shrinkage and surface defects.

Description of drawings

The invention is described by way of example with reference to the accompanying drawings.

Fig. 1 is a schematic diagram of a deoxidation casting apparatus according to a first embodiment of the present invention.

Fig. 2A is a cross-sectional view of the connecting part of the casting model;

Fig. 2B is the front view of connecting part;

Fig. 3 is the schematic diagram of the deoxidation casting equipment of the second embodiment of the present invention;

Fig. 4 is the schematic diagram of the deoxidation casting equipment of the third embodiment of the present invention;

Figure 5 is a cross-sectional view of another casting model example;

Fig. 6 is the schematic diagram of magnesium feeding mechanism;

Figure 7 is a schematic diagram of another example of a furnace;

Figure 8 is a schematic diagram of another example of a furnace;

Fig. 9 is the schematic diagram of the deoxidation casting equipment of the 4th embodiment of the present invention;

Fig. 10 is the schematic diagram of the deoxidation casting equipment of the fifth embodiment of the present invention;

Fig. 11 is the schematic diagram of the deoxidation casting equipment of the sixth embodiment of the present invention;

Fig. 12 is the schematic diagram of the deoxidation casting equipment of the seventh embodiment of the present invention;

Fig. 13 is the schematic diagram of molten metal and deoxidation compound reaction mode;

Fig. 14 is a schematic diagram of the reaction mode of the molten metal stored in the reservoir;

Fig. 15 is the photomicrograph of the product surface that the inventive method is made;

Fig. 16 is a photomicrograph of the surface of a product produced by a conventional method.

Detailed ways

Some preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

First, the basic principle of the present invention will be described. There are many ways to react deoxidizing compounds and molten metals. For example, the deoxidizing compound may be reacted with the molten metal at the sprue of the casting mold as it is poured through it, or reacted with the molten metal in a ladle, or in a reservoir containing the molten metal Neutralize molten metal reactions. In FIG. 13 , inlets 202 and 204 are formed at the edges of the sprue of the casting pattern 200 . Magnesium gas and nitrogen gas are introduced separately into the sprue so that these gases react with the molten metal being poured into the purring mouth. Magnesium nitride compound is a deoxidizing compound formed in the sprue, and the magnesium nitride compound can react with molten metal. With this structure, when the molten metal is poured into the casting mold, the oxide film formed on the surface of the molten metal can be deoxidized, so that a high-quality product can be cast.

In FIG. 13 molten metal is stored in a ladle 208 . Adding deoxidizing compounds to the molten metal in the ladle can deoxidize and remove the oxide film on the surface of the molten metal. The deoxidizing compound may also be added to the molten metal in a reservoir.

Figure 14 shows another example of the reaction of a deoxidizing compound with a molten metal. Molten metal 206 is held in reservoir 210 . The deoxidizing compound is formed in a bubbler 212 whose lower end is immersed in the molten metal 206 and passed into the molten metal 206 . Magnesium gas and nitrogen gas are passed into the bubbler 212 to form a deoxidized compound, and the deoxidized compound is passed into the molten metal 206 to deoxidize and remove the oxide film on the surface of the molten metal 206 . Due to the removal of the oxide film, the fluidity of the molten metal is higher and high-quality products can be cast.

Fig. 15 is a photomicrograph of the surface of an aluminum product cast by the method of the present invention; Fig. 16 is a photomicrograph of the surface of an aluminum product cast by a conventional method. In Fig. 16, shrinkage was observed on the surface of the product. However, the product casted by the method of the present invention in Fig. 15 has a very smooth surface without shrinkage.

Referring now to Figures 1-5, some embodiments of the present invention are illustrated. In these embodiments, magnesium gas and nitrogen gas are separately introduced into the cavity to form the deoxidized compound, and molten metal is then poured into the cavity.

Fig. 1 shows an outline of a casting facility of a first embodiment. The casting pattern 12 is connected to a reservoir 14 . Through the upward movement of the piston 16 , a defined amount of molten aluminum 18 flows from the reservoir 14 . The molten metal surface is exposed on the inner surface of the cavity 12a. A nitrogen gas cylinder 20 is connected to the casting pattern 12 by a pipe 22 . Nitrogen gas was introduced into the casting pattern by opening valve 24 . A cylinder of argon gas 25 is connected to a furnace 28 by a line 26 . Argon gas was introduced into the furnace 28 by opening valve 30 . The heater 32 heats the furnace 28 . The temperature in the furnace is raised to 800°C or higher to sublimate the magnesium powder.

The argon cylinder 25 is also connected to a tank 36 via a line 34 with a valve 33 in which the magnesium powder is stored. Tank 36 is connected to conduit 26 by conduit 38 , the end of which is connected to conduit 26 after valve 30 . A valve 40 is provided on the conduit 38 . Furnace 28 is connected to casting pattern 12 by conduits 42 and 44 , conduit 44 extending through piston 16 . Pipe 42 is provided with a valve 45 .

Shown in FIGS. 2A and 2B is the connection portion 13 of the casting pattern 12 connected to the pipe 22 .

As shown in FIG. 2A, the connecting portion 13 forms a tapered inner hole whose inner diameter gradually increases outward. A tapered connecting piston (not shown) mounted at the front end of the tube 22 is detachably connected to the connecting portion 13 . The connecting portion 13 is connected to the cavity 12a through some ventilation holes 15 .

A casting method implemented using the casting apparatus 10 will be described below.

First, valve 24 is opened and nitrogen gas is introduced from cylinder 20 into casting pattern 12 through line 22 . The nitrogen gas is introduced, and the air inside the casting mold 12 is purged or exhausted. In the upper part of the casting mold 12 there are vent holes (not shown in the figure), from which air is exhausted so that the inside of the casting mold 12 is an oxygen-free atmosphere. Valve 24 is closed immediately after air is purged from casting pattern 12 . While purging air from the casting pattern, valve 30 is opened to pass argon gas into furnace 28, where an oxygen-free atmosphere is also created.

Afterwards, the valve 30 is closed, the valve 40 is opened, and the magnesium powder stored in the tank 36 is passed into the furnace 28 by means of argon pressure. At this time, the flow rate and pressure of argon are adjusted by a flow regulator. Owing to use heater heating furnace 28 to 800 ℃ or higher temperature, the magnesium powder that feeds just sublimates, has produced magnesium gas.

Then, valve 40 is closed, valves 30 and 45 are opened, and magnesium gas is introduced into casting mold 12 through lines 42 and 44 . At this time, the flow and pressure of argon were adjusted. After the magnesium gas is introduced into the casting mold 12, the valve 45 is closed, the valve 24 is opened, and the nitrogen gas is introduced into the casting mold 12. As the nitrogen gas is introduced into the casting mold 12, the magnesium gas reacts with the nitrogen gas in the cavity 12a of the casting mold 12 to produce a magnesium nitride compound (Mg ₃ N ₂ ). The magnesium nitride compound is deposited in powder form on the inner surface of the cavity 12a.

In this state, the piston 16 moves upward, causing the molten metal stored in the reservoir 14 to be poured into the casting mold 12 . The molten aluminum 18 poured into the casting pattern 12 reacts with the magnesium nitride compound deposited on the inner surface of the cavity 12a. Through this reaction, the magnesium nitride compound removes oxygen from the oxide film formed on the surface of the molten aluminum 18, thereby deoxidizing the molten aluminum surface to form a pure aluminum surface. Oxygen remaining in the casting mold 12 or contained in the molten aluminum 18 becomes magnesium oxide or magnesium hydroxide contained in the molten aluminum 18 . The amount of magnesium oxide or magnesium hydroxide is very small and will not have adverse effects on aluminum products.

Since the magnesium nitride compound deposited on the inner surface of the cavity 12a removes oxygen from the oxide film formed on the surface of the molten aluminum 18, pure aluminum is obtained when the aluminum solidifies, so that aluminum can be cast without forming an oxide film. The metal surface is in contact with the inner surface of the cavity 12a, and the magnesium nitride compound is fixed on the inner surface of the cavity 12a without loss, so that deoxidation of the molten metal can be ensured. The surface condition of the inner surface of the cavity 12a has a great influence on the shape of the product. Since the magnesium nitride compound is ensured to be formed and fixed on the inner surface of the cavity 12a, a product with a good shape can be cast.

The magnesium nitride compound can prevent the formation of an oxide film on the surface of the molten aluminum 18, reduce the surface tension of the molten metal 18, and improve the wettability, fluidity, operability and smoothness of the molten metal 18. Therefore, high-quality aluminum products without shrinkage can be cast.

It should be noted that in this embodiment, nitrogen gas is introduced into the cavity 12a from the gas cylinder 20, and the air in the cavity 12a is exhausted. An inert gas such as argon may be used instead of nitrogen to evacuate the air. Air is exhausted to prevent the magnesium nitride compound and oxygen from reacting in the cavity 12a.

To evacuate air from the cavity 12a, nitrogen or argon gas is introduced into the cavity 12a. Air can also be sucked out of the mold cavity 12a by the vacuum pump 52 to create an oxygen-free environment in the mold cavity 12a. In this case, the valve 19 is opened to evacuate the cavity 12a through the pipe 17, and then the valve 19 is closed to introduce magnesium gas into the cavity 12a (see FIG. 1).

Nitrogen gas is introduced into the cavity 12a, and when the magnesium nitride compound is produced therein, argon gas is introduced into the cavity 12a, and the argon gas is used as a carrier gas of the magnesium gas. But there are some ventilation holes in the mold cavity 12a, these ventilation holes will discharge the gas in the mold cavity when pouring molten metal 18, make the pressure in the mold cavity 12a drop gradually after pouring molten metal 18. Due to the reduced pressure, fresh air will intrude into the cavity 12a. To prevent the intrusion of air, valve 24 is opened and nitrogen gas is supplied from gas cylinder 20 to cavity 12a while molten metal 18 is being poured. The amount of nitrogen supplied is equal to the sum of the amount of exhausted air and the amount of nitrogen consumed by forming magnesium nitride compounds. The amount of nitrogen gas consumed can be known from the amount of magnesium gas supplied to the cavity 12a. The nitrogen supply is controlled by a flow meter 21 and a valve 24 on line 22 .

In the above embodiments, the method of the present invention is applied to gravity casting. The deoxidation casting method of the present invention is not limited to gravity casting.

Referring now to Fig. 3, a second embodiment of the present invention will be described. The casting model 12 is composed of an upper mold part 50 and a die part 51 . That is, the method of the present invention can be applied to high pressure casting. Unlike the gravity casting casting mold described in the first embodiment, the casting mold 12 of the second embodiment has high airtightness.

In the second embodiment, the pipeline 53 is branched from the pipeline 22 , the pipeline 22 connects the nitrogen cylinder 20 to the casting mold 12 , and the pipeline 53 is connected to the depressurization pump 52 . A valve 54 is provided in the middle of the conduit 22 . The cavity 12a is connected to the outside by a pipe 55 on which a valve 56 is mounted.

In the casting apparatus of this embodiment, valves 24 and 56 are first closed, valve 54 is opened, and then depressurization pump 52 is operated to evacuate casting mold 12 to create an oxygen-free environment therein. Simultaneously, argon gas is introduced into furnace 28 from cylinder 25, valve 33 is opened, argon gas enters tank 36, and magnesium powder is sent into furnace 28 from tank 36. The magnesium powder is sublimated in the furnace 28, producing magnesium gas. With valves 54 and 56 closed, valve 45 is opened and magnesium gas is introduced into casting mold 12 together with argon.

Thereafter, valve 56 is closed, valves 24 and 54 are opened, and nitrogen gas is introduced from cylinder 20 into casting pattern 12 . After the nitrogen gas is introduced into the casting mold 12, the magnesium gas and the nitrogen gas react with each other, and the magnesium nitride compound powder is deposited on the inner surface of the cavity 12a.

In this case, molten aluminum is poured into the cavity 12a by the upward movement of the die portion 51 . At this time, on the inner surface of the cavity 12a including the inner surface of the upper mold part 50 and the inner surface of the die part 51, the magnesium nitride compound is covered, and the same as the first embodiment, it can prevent the molten aluminum 18 surface from being formed during casting. form an oxide film.

In this embodiment, the inner surface of the cavity 12a is heat-treated to form ferric oxide. In Fig. 3, symbol 12b represents the heat-treated layer of ferric oxide. The ferric oxide layer does not react with the magnesium nitride compound on the inner surface of the cavity 12a. Therefore, the deoxidizing function of the magnesium nitride compound can be maintained, and the oxide film on the molten aluminum 18 can be effectively deoxidized. In addition to the heat treatment described above, the inner surface of the cavity 12a can also be effectively nitrided. When the molten aluminum 18 is to be poured, the die part 51 is pressurized, the valve 56 is opened, and the molten aluminum 18 is conveniently poured.

Referring now to FIG. 4, a casting apparatus 10 of a third embodiment will be described. In those embodiments described above, the magnesium gas is produced outside the casting mold. While in the third embodiment, as shown in FIG. 4, a heating portion 32a is provided at the bottom of the casting mold 12, which includes a heat conducting member 71, a heater 72 for heating the heat conducting member 71, and a heater for preventing heat conduction to the casting mold. 12 A heat insulator 73 for keeping the temperature of the heat-conducting part at 800°C or higher. With this structure, magnesium can be sublimated within the casting mold 12 , that is, magnesium gas is generated within the casting mold 12 .

In this embodiment, the cavity 12a of the casting mold 12 is evacuated by the depressurization pump 52, or the air is purged from the cavity 12a by introducing an inert gas such as argon into the cavity 12a. Then, the magnesium in the cavity 12a of the casting mold 12 is heated to sublimate it, and nitrogen gas is introduced from the cylinder 20 into the cavity 12a to deposit a magnesium nitride compound on the inner surface of the cavity 12a.

The inner surface of the cavity 12a is pre-coated with a non-oxidizing material 12c. When the magnesium nitride compound is formed, the non-oxidizing material 12c will not react with the magnesium nitride compound, and the deoxidizing function of magnesium nitride can be maintained. When the molten aluminum 18 is poured into the casting mold 12, the oxide film formed on the surface of the molten aluminum is deoxidized and removed, so casting is performed with pure aluminum. Since it is casted from pure aluminum, high-quality products without shrinkage and surface defects can be cast.

Referring now to FIG. 5, another example of a casting pattern 12 having a magnesium gas inlet and a nitrogen gas inlet is illustrated. In the casting mold 12, a piston 16 is housed in the gate 11a and can move in the vertical direction. The gate 11a is connected to the cavity 12a through the pouring channel 11b. The magnesium gas inlet 44a is connected to the middle of the pouring channel 11b and the pipe 42 . The cavity 12a is formed between the stems 23a and 23b, which are arranged vertically. Nitrogen inlets 22a and/or exhaust holes 17a are provided in the sockets 23a and 23b. The sockets 23a and 23b and the cavity 12a are connected by connecting channels 15 . One of the magnesium gas inlet 44a, the nitrogen gas inlet 22a and the suction hole 17a is preferably used as a vent hole to exhaust air from the molten metal 18 as it is poured into the cavity 12a.

In the casting model 12 of this embodiment, nitrogen gas is introduced into the cavity 12a through the nitrogen inlet 22a, and air is purged from the cavity 12a. Then, magnesium gas and argon carrier gas are introduced into the cavity 12a together through the magnesium gas inlet 44a. A magnesium nitride compound is formed in the cavity 12a. In the case of evacuating the cavity 12a in advance, it can be done through the suction hole 17a.

As shown in FIG. 5 , magnesium gas and nitrogen gas are introduced into the cavity 12a of the casting mold 12 through different ways, so that the tubes 22 and 42 can be prevented from being blocked by deposits, easy to maintain and improve casting efficiency.

Figures 6-8 show other examples in which a metal such as magnesium is evaporated and the evaporated metal gas is passed into the cavity of the casting mold.

In FIG. 6, a fixed amount of magnesium powder is fed into the furnace 28. As shown in FIG. A tank 120 storing magnesium powder is connected to the furnace 28 by a pipe 122 fitted with valves 124 and 126 and between the valves 124 and 126 is a fixed volume storage section 128. The fixed amount storage section is cylindrical, and the amount of magnesium powder stored therein is controlled by adjusting its length and/or inner diameter.

Magnesium powder is supplied to the furnace 28 from a fixed quantity storage section 128 . First, close the valve 124, open the valve 126, argon gas is passed into the tank 120 from the cylinder 25, and a fixed amount of magnesium powder is provided from the tank 120 to the fixed amount storage section 128. Then, valve 33 is closed, valves 30 and 124 are opened, and magnesium powder is introduced into furnace 28. At this time, the flow meter 129 was used to observe the amount and pressure of the argon gas sent from the cylinder 25 . With the above structure, the supply of magnesium powder to the furnace 28 can be ensured.

In FIG. 7, the casing 100 is made of a heat insulating material, and its upper surface is opened. The furnace chamber 101 of the furnace 28 consists of a heat-resistant material. A cover 102 covers the furnace cavity 101 and is fixed to a flange 104 with screws 103 . There is a heater 105 between the furnace chamber 101 and the casing 100 to heat the furnace chamber 101 .

The cover 102 has three opening portions 106 , 107 and 108 which are connected to the oven chamber 101 . An introduction pipe 109 is connected to the pipe 26 , the pipe 26 is connected to the tank 36 , and the introduction pipe 109 enters the furnace chamber 101 through the opening portion 106 . The lower end of the introduction pipe 109 is open and located near the bottom of the furnace chamber 101 . The thermocouple 110 enters the furnace cavity 101 through the opening portion 107 . A discharge pipe 111 is connected to the pipe 42 , which is connected to the casting mold 12 , and the discharge pipe 111 passes through the opening portion 108 . The upper end of the pipe 111 is located above the furnace chamber 101 and is open to the air.

Six plates 112a-112f made of heat-resistant material are arranged in parallel with a predetermined distance apart in the vertical direction. The lead-in tube 109 passes through holes drilled in the plates 112a-112f. The lower end of the introduction pipe is opened in the space between the bottom of the furnace chamber 101 and the lowermost plate 112a.

A through hole 114a is drilled in the lowermost plate 112a, spaced apart from the introduction pipe 109. As shown in FIG. Plates 112a-112f have through holes 114a, 114b and 114, respectively, which are vertically staggered.

A partition 116b is provided on the bottom surface of the plate 112b. The spacer 116b divides the space between the plates 112a and 112b into two parts: one part is connected to the through hole 114a; the other part is connected to the through hole 114b. Note that there is a small gap between the bottom surface of the partition 116b and the upper surface of the plate 112a. So, the two parts are connected to each other through this small gap. There are partitions 116 in the spaces between adjacent plates 112b-112f, and there are also small gaps in these spaces.

Magnesium gas can be produced in the furnace cavity 101 . Firstly, magnesium powder is fed from tank 36 into furnace chamber 101 by means of argon pressure through pipes 226 and 109 . Since the magnesium powder is very light, the magnesium powder and the argon gas are sprayed into the lower part of the furnace chamber 101 and dispersed thereon. However, the space in the furnace is divided into staggered spaces by the plates 112a-112f. When the magnesium powder rises in the staggered space, the magnesium powder sublimates to form magnesium gas, and it takes a certain time to fully sublimate all the magnesium powder. In the furnace 28, the space in the furnace chamber 101 is vertically divided into multiple subspaces, and the magnesium powder and argon enter the lowermost subspace of the furnace chamber 101 together, so the dispersion of the magnesium powder is limited, and it takes a certain time to rise these magnesium powders. . With this structure, the magnesium powder can be fully heated and fully sublimated, and no magnesium powder will enter the casting mold 12 through the pipe 111 . Magnesium gas in the furnace 28 is fed into the cavity 12a of the casting mold together with argon gas used as a carrier gas.

In FIG. 8 , magnesium flakes 140 are fed into a furnace 28 where they are melted and evaporated, and the resulting magnesium gas is passed into the cavity of the casting mold 12 . An air lock chamber 142 is formed on the upper part of the furnace 28, and the air lock chamber is airtight, and magnesium flakes 140 are stored therein. A prescribed amount of magnesium flakes 140 is dropped into the furnace 28 . Be to open flashboard 144, make magnesium sheet enter in the furnace 28 from air lock chamber 142. Magnesium flakes 140 are melted in furnace 28 . After a predetermined amount of magnesium flakes is supplied to the lock chamber 142 , the lid 146 is closed, and argon gas is introduced from the cylinder 25 into the lock chamber 142 . Then, the air in the air lock chamber is exhausted from the discharge pipe 148 , creating an oxygen-free atmosphere in the air lock chamber 142 . Magnesium gas from the furnace 28 is fed into the cavity of the casting mold 12 together with argon gas from the cylinder 25 used as a carrier gas.

Referring now to FIGS. 9-11, fourth to sixth embodiments are illustrated. In each embodiment, magnesium gas and nitrogen gas are pre-reacted outside the casting mold 12 to produce magnesium nitride compound (Mg ₃ N ₂ ), and the nitrogen After the magnesium compound is introduced into the cavity, molten metal is poured into the cavity.

A casting apparatus 10 of a fourth embodiment is shown in FIG. 9 . The casting pattern 12 is connected to a reservoir 14 in which molten metal 18 is stored. By the upward movement of the piston 16 , a prescribed amount of molten aluminum 18 is poured into the casting mold 12 . A nitrogen gas cylinder 20 is connected to the casting pattern 12 by a pipe 22 . Valve 24 is opened, nitrogen gas is introduced into casting pattern 12, and the air in casting pattern 12 is purged. Gas cylinder 20 is connected to furnace 28 by line 26 and valve 30 is opened to introduce nitrogen gas into furnace 28 . The heater 32 heats the furnace to a temperature of 800° C. or higher to sublimate the magnesium powder. The gas cylinder 20 is connected by a pipe 34 to a tank 36 in which magnesium powder is stored. The tank 36 is connected by a tube 38 to that part of the tube 26 where the valve 30 is located in the furnace 28 . The tube 38 is fitted with a valve 40 . Furnace 28 is connected to casting pattern 12 by conduits 42 and 44 , which extend through piston 16 into casting pattern 12 . The structure of the connecting portion 13 connecting the pipe 22 to the casting mold 12 is the same as that of the first embodiment shown in FIG. 2 .

The deoxidation casting method carried out in the casting facility 10 will now be described.

First, the valve 24 is opened, and nitrogen is introduced into the casting mold 12 from the steel cylinder 20 through the pipe 22 until the casting mold 12 is filled with nitrogen. Air from the casting pattern 12 is blown out through vent holes (not shown). Then, valve 30 is opened and nitrogen gas is introduced into furnace 28 .

Afterwards, the valves 24 and 30 are closed and the connection piston of the tube 22 is separated from the connection part 13 . Valve 40 is opened and magnesium powder is passed from tank 36 into furnace 28 together with nitrogen. The magnesium powder is sublimated in the furnace 28 and the magnesium gas reacts with the nitrogen so that the magnesium nitride compound gas is introduced into the casting mold 12 through lines 42 and 44 . The magnesium nitride compound is deposited in powder form on the inner surface of the cavity 12a of the casting pattern 12 .

The piston 16 is then moved upwards, pouring molten aluminum 18 into the casting pattern 12 . The molten aluminum 18 and the magnesium nitride compound react on the inner surface of the cavity 12a of the casting mold 12, the magnesium nitride compound removes oxygen from the oxide film formed on the surface of the molten aluminum, and the molten aluminum becomes pure aluminum. Some of the oxygen remaining in the cavity or contained within the molten aluminum 18 becomes magnesium oxide or magnesium hydroxide, but is still contained within the molten aluminum 18 . Magnesium oxide and magnesium hydroxide are present in small quantities and are chemically stable compounds, so they do not adversely affect the aluminum product. Excess air is vented out of the casting pattern 12 through vent holes (not shown).

As described above, the magnesium nitride compound removes oxygen from the oxide film formed on the surface of the molten aluminum 18, and the oxygen remaining in the cavity or contained in the molten aluminum 18 becomes magnesium oxide or magnesium hydroxide and is contained in the molten aluminum. 18 in. Therefore, no oxide film exists on the surface of the molten aluminum 18 .

Since there is no oxide film, the surface tension of molten aluminum will not increase, the fluidity, operability and wettability of molten aluminum 18 are improved, and high-quality aluminum products with high smoothness can be cast.

The amount and density of the magnesium nitride compound in the casting pattern 12 is not limited. Even if the density of the magnesium nitride compound is low, the nitrogen gas and the magnesium nitride compound can still fill the casting mold 12, which can greatly reduce the amount of oxygen in the casting mold 12 and prevent the formation of an oxide film.

Nitrogen does not have to be passed through the casting mold 12 beforehand. That is, the nitrogen gas and the magnesium nitride compound can be passed directly into the casting pattern 12 and air can be exhausted therefrom.

In a fourth embodiment, the deoxidation casting of the present invention is applied to gravity casting. The method of the invention is not limited to this embodiment.

Referring now to Fig. 10, a fifth embodiment will be described. The casting pattern 12 for high pressure casting includes an upper mold portion 50 and a die portion 51 . Unlike the fourth embodiment shown in FIG. 9, the casting pattern 12 shown in FIG. 10 has higher airtightness. The cavity 12a of the casting mold 12 is connected to the decompression pump 52 through the pipe 53 instead of the pipe 22 (see FIG. 9 ) for introducing nitrogen gas. The tube 55 connects the cavity 12 a to the outside of the casting pattern 12 . On pipes 52 and 55 are valves 54 and 56 respectively.

In this embodiment, the magnesium nitride compound is deposited in the casting pattern 12 by opening valve 54 and closing valve 56 to evacuate air from the casting pattern 12 to create an oxygen-free environment. In this case, when the magnesium nitride compound is deposited in the casting mold 12, deoxidation does not start as well, so that the magnesium nitride compound can be effectively used for deoxidation of the oxide film formed on the surface of the molten metal 18. Note that valve 56 may be opened during high pressure casting to allow easy pouring of molten metal 18 into casting mold 12 .

Referring now to Fig. 11, a sixth embodiment will be described. A tank 36 storing magnesium powder is connected to the furnace 28, and a nitrogen gas cylinder 20 and an argon gas cylinder 25 are connected to the furnace 28. The pipe 26 connected to the tank 36 and the cylinder 25 and the pipe 22 connected to the cylinder 20 both extend to the inner surface near the bottom of the furnace 28 . 22 a and 26 a of tubes 22 and 26 extend in furnace 28 . The furnace 28 is connected to the casting pattern 12 by a pipe 42 , the lower end of which pipe is open above the furnace 28 .

In the sixth embodiment, valves 24 and 45 are first opened, nitrogen is introduced into furnace 28 and casting mold 12 through pipes 22 and 42, and the air in furnace 28 and casting mold 12 is purged or exhausted. Then, valves 24 and 45 are immediately closed. Note that by opening valve 30 and introducing argon, the furnace 28 and casting mold 12 can be purged of air.

Thereafter, valve 30 is closed, valves 33, 40 and 45 are opened, and magnesium powder is supplied from tank 36 into furnace 28 together with argon gas. Simultaneously, valve 24 is opened and nitrogen gas is introduced into furnace 28 . The furnace 28 is heated at 800°C or higher to sublimate the magnesium powder. Magnesium powder passed into the furnace 28 sublimes to produce magnesium gas, whereby the magnesium gas reacts with nitrogen to form a magnesium nitride compound, which is an example of a deoxidizing compound. Argon is used as a carrier gas to feed the magnesium nitride compound into the cavity of the casting mold 12, and the magnesium nitride compound is deposited on the inner surface of the cavity in the form of powder.

Molten aluminum is poured into the cavity while the magnesium nitride compound is being deposited on the inner surface of the cavity. In the cavity, the molten aluminum and the magnesium nitride compound react on the inner surface of the cavity, resulting in deoxidation of the oxide film formed on the surface of the molten aluminum while casting.

Referring now to Figure 12, a seventh embodiment is illustrated in which the means for generating magnesium gas is separate from the reaction chamber, such as the furnace 28. The main part 151 of the magnesium gas generating device 150 is made of heat insulating material. The main part 151 is heated to 800°C or higher by the heater 32a. The pipe 26 is connected to a tank in which magnesium powder is stored, and the argon tank is connected to the main part 151 . The main part 151 is connected to the furnace 28 by a pipe 152 . A nitrogen cylinder 20 is connected to a furnace 28 by a line 22 .

In this embodiment, magnesium powder is supplied via line 26 to the device 150 for generating magnesium gas by means of argon gas. The incoming magnesium powder is heated and sublimated, producing magnesium gas. Magnesium gas is passed into furnace 28 via line 152 . , the pipe 152 is preferably heated by a heater 154 to maintain the temperature of the magnesium gas.

Nitrogen is passed through line 22 into furnace 28. The tubes 152 and 22 are opened, the two tubes facing each other in the furnace 28, so that the magnesium gas and the nitrogen gas collide with each other in the furnace 28. By introducing magnesium gas and nitrogen gas into the furnace 28, the two gases react to form a magnesium nitride compound (deoxidized compound).

The high temperature of the furnace 28 is maintained by the heater 33 to accelerate the mutual reaction of the two gases and introduce the active deoxidizing compound into the cavity 12a of the high temperature casting mold 12. Therefore, deoxidizing compounds can be effectively used for molten metals. Preferably, the furnace 28 is mounted on the casting mold 12 so as to be very close to the cavity 12a. The connecting channel 156 connects the furnace 28 to the gate of the casting pattern 12 or to some part near the cavity 12a. Since the molten metal enters the cavity 12a immediately after reacting with the deoxidizing compound, the fluidity of the molten metal in the cavity 12a is improved, so that the molten metal can be effectively cast.

In the above embodiments, pure aluminum is used as the molten metal, but other metallic materials, such as aluminum alloys containing silicon, magnesium, copper, nickel, can be used as the cast metal. In the present invention, the term "aluminum" includes aluminum alloys.

In addition to aluminum and aluminum alloys, other metals such as magnesium, iron and their alloys can also be cast according to the method of the present invention.

The invention may take other specific forms without departing from the spirit or essential characteristics thereof. Therefore, some embodiments herein are only for illustration, not constituting limitation to the present invention, the scope of the present invention determined by the claims rather than the foregoing description, and all changes within the meaning and equivalent scope of the claims included in the claims.

Claims (8)

1. A deoxidation casting method, the method may further comprise the steps: A deoxidizing compound produced by reacting a metal gas and an inert gas reacts with molten metal, thereby deoxidizing the oxide film on the surface of the molten metal; said metal gas and said inert gas are reacted outside the casting mold to produce a deoxidizing compound, and said deoxidizing compound is introduced into a cavity of the casting mold, and then molten metal is poured into the cavity; and The deoxidizing compound is introduced into the casting mold cavity using an inert gas as a carrier gas. 2. The method according to claim 1, characterized in that an oxygen-free atmosphere is created in the mold cavity and the deoxidizing compound is then introduced into the mold cavity. 3. The method according to claim 2, characterized in that the oxygen-free atmosphere is generated by evacuating the casting mold cavity. 4. The method of claim 2, wherein the oxygen-free atmosphere is created by introducing an inert gas into the cavity and purging air from the cavity. 5. The method of claim 1, wherein said mold cavity is pressurized with a gas that is non-reactive with said deoxidizing compound within the mold cavity, and the molten metal is poured into the pressurized mold cavity. 6. The method according to claim 1, characterized in that when the molten metal is poured into the mold cavity, the deoxidizing compound reacts with the molten metal to deoxidize the oxide film on the surface of the molten metal. 7. The method of claim 1, wherein The magnesium nitride compound produced by the reaction of magnesium gas and nitrogen gas reacts with molten aluminum to deoxidize the oxide film on the surface of molten aluminum; The magnesium gas and the nitrogen react outside the casting mold to produce a magnesium nitride compound, and then introduce the magnesium nitride compound into the mold cavity of the casting mold, and then pour molten aluminum into the mold cavity; Argon was used as a carrier gas for introducing the magnesium nitride compound into the cavity of the casting mold. 8. A deoxidation casting equipment, wherein the magnesium nitride compound prepared by reacting magnesium gas and nitrogen gas reacts with molten aluminum, and the oxide film on the surface of molten aluminum is deoxidized by the magnesium nitride compound, the equipment comprising: A casting pattern with a cavity into which molten aluminum is poured to cast aluminum in a predetermined shape; a reaction chamber separate from the casting pattern; means for introducing nitrogen and magnesium into said reaction chamber; A device for introducing a magnesium nitride compound produced by reacting magnesium gas generated by heating and sublimating magnesium with nitrogen gas in said reaction chamber, together with an inert carrier gas.

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