WO2004058434A1

WO2004058434A1 - Vacuum die casting and method for production thereof

Info

Publication number: WO2004058434A1
Application number: PCT/JP2003/016541
Authority: WO
Inventors: Yoshio Kaneuchi; Tomoya Imamura
Original assignee: Hitachi Metals, Ltd.
Priority date: 2002-12-24
Filing date: 2003-12-24
Publication date: 2004-07-15
Also published as: JPWO2004058434A1; JP4518256B2; AU2003292610A1; CN1322951C; CN1732058A

Abstract

A vacuum die casting of an aluminum alloy, characterized in that a gas remaining in a bubble in the casting has a composition wherein the content of a H2 gas is less than that of a CO2 gas, as measured by gas chromatography after the release of the bubble by the melting of the casting.

Description

FIELD OF THE INVENTION Field of the Invention

The present invention relates to a vacuum die-cast product of an aluminum alloy having excellent mechanical strength and a method for producing the same, and more particularly to a vacuum die-cast product of an aluminum alloy suitable for transportation equipment having high strength and high toughness and its production. About the method. Background art

Die-casting is a technology for manufacturing metal parts by filling molten metal into the mold at high speed and high pressure. It has higher dimensional accuracy than other manufacturing methods, and has beautiful skin and productivity. Has the advantage of being high. However, the high-speed filling of the molten metal causes the surrounding gas to be entrained in the molten metal, resulting in a large number of air bubbles filled with gas inside the product and inclusions such as oxidized substances formed by the reaction between the gas and the metal. There is a problem that exists. These defects not only reduce the mechanical strength of the product, but also the gas-filled bubbles, especially during heat treatment and welding, become blisters due to the expansion of the internal gas, which significantly reduces the mechanical strength. Therefore, the use of the die-cast product as a structural member has been limited.

The gas contained in the die-cast product includes, in addition to atmospheric components, a combustion gas of a lubricant for a plunger and a release agent for a mold cavity. In order to reduce the entrainment of these gases, a vacuum die-casting method of reducing the pressure inside the mold cavity and making it has been put to practical use.

For example, Japanese Patent Application Laid-Open No. 6-126415 discloses a vacuum die force apparatus for reducing the pressure in the cavity and loading the molten metal into the injection sleeve, which includes a fixed type mounted on a fixed platen, and a movable type forming a cavity together with the fixed type. An injection sleep communicating with the cavity, a plunger moving forward and backward in the injection sleeve, a holding furnace below the injection sleeve for storing the molten metal, and one end connected to the hot water inlet of the injection sleeve, and the other end connected to the injection sleeve. A hot water supply pipe immersed in the molten metal in the holding furnace and a vacuum inside the cavity And a pressure reducing means for reducing the pressure and loading the molten metal in the holding furnace into the injection sleeve via a hot water supply pipe.

However, even with the vacuum die-casting method using this vacuum die-casting device, it is impossible to eliminate the residual gas even if it can be reduced. It is because (1) it is industrially difficult to make the mold cavity completely vacuum, and (2) it is also difficult to completely remove the gas generated from the release agent and lubricant. by.

In particular, in the case of aluminum die-casting, to improve its mechanical properties, it is necessary to (a) prevent hydrogen dissolved in the molten metal from being discharged during solidification to form pores in the product, and (b) hydrogen It is important to remove hydrogen from the molten metal in order to prevent brittleness due to water, and (c) to remove oxygen in order to suppress the formation of inclusions such as oxides. In particular, when oxide films and inclusions are present in aluminum products, the edges around them have a large notch coefficient, which causes cracks due to stress concentration and greatly reduces the toughness of the products.

Conventionally, silicone-based emulsion release agents have been used for die casting of aluminum alloys. The silicone emulsion type release agent is obtained by emulsifying a modified silicone oil with an emulsifier using water as a medium. However, with the emulsion-type release agent, it was found that not only the total amount of gas remaining in the product was large, but also that more than 30% of the remaining gas was H ₂ , C ₂ H ₆ , CH _4, etc. . In particular, because there is more CO2 gas than CO2 gas, there is a problem that the product becomes brittle during heat treatment and welding.

This is considered for the following reasons. In other words, since the mold cavity has a temperature of about 300 ° C, the use of an aqueous mold release agent causes almost all of the water to evaporate. Release agent adheres. Since the surface temperature of the mating surface is low, the moisture in the release agent remains without evaporating. For this reason, even if the pressure is reduced after clamping, the release agent is sucked into the cavity from the gap between the movable mold and the fixed mold and continues to evaporate. The same phenomenon occurs when an aqueous release agent adheres to the movable part behind the nest. As a result, the degree of vacuum in the cavity does not decrease and the amount of hydrogen gas generated increases. Since gas entrainment is likely to occur near the surface of the mold cavity, the gas-containing pores are often near the surface of the article. When heat treatment or welding is performed on a product having such gas-containing pores, the gas in the pores expands, and the pores become so-called blisters, which become B-shaped protrusions protruding from the surface of the product. Prestars can be the starting point for cracks and fractures when loaded.

If the gas sealed in the pores is hydrogen, it is absorbed by the product during heat treatment or welding, causing deterioration of the product. Therefore, it was found that it is necessary not only to reduce the entrainment of gas during vacuum die casting, but also to reduce the proportion of hydrogen in the entrained gas. Purpose of the invention

Accordingly, it is an object of the present invention to provide a vacuum die-casting product which is suitable not only for a small number of bubbles in which gas remains but also for a small proportion of hydrogen in the gas in the gas bubble, and is therefore suitable for undercarriage parts of transport equipment and vehicle body components. It is to provide.

Another object of the present invention is to provide a method for reliably manufacturing such a vacuum die-cast product. DISCLOSURE OF THE INVENTION

In light of the above objectives, as a result of intensive research, heat release and welding have been achieved by using a release agent that not only generates a small amount of gas wound into the molten metal during vacuum die casting but also generates a small amount of hydrogen gas. The present inventors have found that a vacuum die-cast product which does not cause blistering and hydrogen embrittlement problems can be obtained even when the above method is performed, and reached the present invention.

That is, in the vacuum die-cast aluminum alloy product of the present invention, when the gas remaining in the bubbles is released by dissolution of the product and measured by gas chromatography, the composition of H ₂ gas is smaller than that of the C 0 ₂ gas. It is characterized by having.

50% of the total amount of gas remaining in the vacuum die casting铸造article is preferably C0 ₂ gas. The total amount of residual gas is 20 cm3 / 100 g or less at any point. It is preferably 10 cms / 100 g or less on average for the entire product.

C0 ₂ gas of the residual gas is preferably not more than 9 cm ^3/100 g as an average of the entire Kagamizo products. Further, the total amount of H ₂ gas, CBU gas and C ₂ H ₆ gas is preferably 5 cm3 / 100 g or less on average for the entire manufactured product.

The proportion of H ₂ gas in the residual gas is preferably 15% or less, more preferably 10% or less. Further, the total amount of CH ₄ gas, C ₂ gas and CO gas is preferably 20% or less as an average of the entire manufactured product.

The vacuum die-casting product of the present invention is preferably used for undercarriage parts of transport equipment or body component parts.

In the method for manufacturing a vacuum die-cast product according to the present invention, the aluminum alloy melt is charged into the injection sleeve by reducing the pressure in the mold cavity, and then the plunger fitted to the injection sleeve is advanced to move the inside of the injection sleeve. When the gas remaining in the air bubbles of a vacuum die-cast product is released by dissolution of the product and measured by gas chromatography, the gas is less than the CO ₂ gas. The method is characterized by applying a synthetic water substantially free of water as a release agent to a mold cavity so as to have a small composition, and then performing a structure.

It is preferable that the chemically synthesized oil contains 70% by mass or more of silicone oil and has a kinematic viscosity of ²⁰⁰ _× 10 −2 m ² / _s or less. Further, it is preferable to apply a lubricant substantially free of water into the injection sleeve. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic cross-sectional view showing one example of a vacuum die casting apparatus (in a mold opened state) used in the present invention.

FIG. 2 is a schematic cross-sectional view showing a state in which the vacuum die casting apparatus of FIG. 1 is clamped, and a molten aluminum alloy is charged in an injection sleeve.

Fig. 3 is a schematic cross-sectional view showing a state in which the plunger of the vacuum-die-casting apparatus that has been clamped is pushed into the injection sleeve, and the molten aluminum alloy is injected into the mold cavity. Figure 4 is a graph showing the degree of vacuum in the cavity from the start of hot water supply to the completion of injection.

FIG. 5 is a schematic perspective view showing an example of the vacuum die-cast product of the present invention, and FIG. 6 is a micrograph showing the metal structure of the vacuum die-cast product having a vacuum-like shrinkage cavity.

Figure 7 is a micrograph showing the metal and tissue of a vacuum die-cast product having voids in which gas remains.

FIG. 8 is a micrograph showing a state in which voids in which gas remains have become prestars by heat treatment. BEST MODE FOR CARRYING OUT THE INVENTION

[1] Vacuum die-casting products

The total amount of residual gas in a vacuum die-cast product depends not only on the manufacturing method but also on the shape of the product. For example, a simple flat plate shape can reduce the total amount of residual gas.However, for die-cast products that require complex shapes, it is not possible to determine whether the manufacturing method was optimal only with the total amount of residual gas. difficult. Thus, the ratio of C0 ₂ gas及Pi H ₂ gas remaining in the gas as well the total amount of residual gas is important in determining the quality of the vacuum die force strike铸造products.

The total amount and composition of the residual gas generated by the thermal decomposition of the release agent and the lubricant can be measured only after removing the gas remaining in the bubbles of the product, but in order to completely remove the residual gas, Must dissolve. However, the molten aluminum alloy reacts with oxygen and water vapor to produce aluminum oxide, which consumes oxygen and reduces the water vapor to hydrogen gas. The total amount and composition of the gas do not completely match the total amount and composition of the gas present in the manufactured product. Therefore, in this specification, simply referring to “total amount and composition of residual gas” shall mean the total amount and composition of residual gas extracted by dissolving the product unless otherwise specified.

Specifically, the product is melted at 700 ° C in an Ar atmosphere decompressed to 4 × 10 ³ kPa, and the generated gas is gas chromatographed with an Ar carrier gas at a flow rate of 50 ml / min. The mixture was poured into a parallel split column of a mattography analyzer (GC-8AIT, manufactured by Shimadzu Corporation) and analyzed by gas chromatography. The analysis time is 15 seconds. The total amount and composition of the residual gas are measured under the above conditions unless otherwise specified.

The residual gas is not uniformly contained in the product, but varies depending on the location. In concrete terms, less the total amount of the residual gas in the out sprue portion near錶造products, and the proportion of the C0 ₂ gas of the residual gas is high, the farthest portion (the vacuum pump side) the remaining gas from the sprue And the proportion of CO2 gas in the residual gas tends to be low. Therefore, in the vicinity of the gate, the part farthest from the gate, and in the middle part, the test pieces were sampled from 3 to 10 places, and the amount and composition of the residual gas were measured for each test piece, and the measurement of each part was performed. Values and their averages need to be determined.

The total amount of residual gas 20 is preferably at cms / 100 g or less, and preferably Ru der 10 cm ^3/100 g or less as an average of the entire铸造products the most common sprue portion near. If the total amount of residual gas exceeds these upper limits, presters are generated during (heat treatment of the product) and welding, causing not only poor appearance but also a decrease in mechanical strength. The total amount of residual gas is preferably Ri good not more than average 8.0 cm ^3/100 g. In addition, the gas amount is expressed in the standard state (20 ° C, 1 atm) unless otherwise specified, regardless of the gas type.

The upper limit of the amount of CO ₂ gas is also preferably 9 cms / 100 g on the average of the entire manufactured product. The lower limit of the amount of the co ₂ gas is not limited, but in many cases it is preferably about 2.5 cm ³ as an average of the entire product. In the case of high-speed filling such as die casting, CO gas is very fine, less than 10 m, and is dispersed as bubbles in the manufactured product. Such bubbles have a very small notch coefficient and a very low stress concentration due to their spherical shape.

Other gases total amount of (CH _4, C ₂ ¾ and ¾) is preferably not more than 5 cm ^3/100 g as the average of the entire鐃造products. Although N ₂ gas is inert, in order to prevent the occurrence of Bliss coater, 7 cm ³ / is preferably at 100 g or less as an average of the entire錶造product, equal to or less than l cm ^3/100 g Is more preferred. When N ₂ gas is at 7 cm ^3/100 g than vacuum mold Kiyabiti it is insufficient.

The composition of the residual gas, is necessary ¾ gas is less than C0 ₂ gas is there. Preferably, at least 50% of the total amount of residual gas is C02 gas. By satisfying these conditions, most of the gas in the bubbles is inert, so that the product does not become brittle during heat treatment or welding.

Since H ₂ is severe reduction in the mechanical strength of铸造article by hydrogen embrittlement is 15 percent to average even locally, preferably the proportion of H ₂ is Ru der than 15% to the total amount of residual gas, More preferably, it is 10% or less. It is preferable that CH ₄ , C ₂ H ₆ and CO, which are decomposition products of the release agent, be as small as possible in order to reduce the total amount of residual gas and obtain stable mechanical strength. Specifically, the total amount of CH ₄ , C 2 H 6 and CO is preferably in a range of 20% or less based on the total amount of the residual gas.

[2] Vacuum die casting method

(1) Release agent

In the present invention, a chemical synthetic oil substantially free of water is used as a release agent as a gas generating source. This non-aqueous release agent can significantly reduce the amount of application as compared with a conventional aqueous emulsion type release agent, so that the residual gas amount of the vacuum die-cast product obtained can be reduced.

As a synthetic oil substantially free of moisture, for example, silicone oil

70 mass ⁰ /. The above is included, and the balance is preferably polyolefin or paraffin. Preferred silicone oils include dimethyl silicone oil, -olefin modified silicone oil, methylstyryl silicone oil, methylphenyl silicone oil, alkylaryl modified silicone oil, and methyl hydrogen silicone oil. Examples of polyolefin include low molecular weight polyethylene, polypropylene, polybutene-1, and poly4-methylpentene-1. It is preferable that the polyolefin be reduced in molecular weight by an oxidation reaction, if necessary, and also be improved in compatibility with silicone oil. Since these components have a large amount of carbon, the proportion of CO ₂ gas in the gas generated by decomposition increases.

The spraying of the mold Kiyabiti surface in view, kinematic viscosity of at 40 ° C in synthetic lubricant ^{^{200 X 10- 6 m 2 / s}} (200 cSt) or less, preferably 100 X 10- ⁶ m ² / s (100 cSt) or less Lower, more preferably ^{^{50 X 10- 6 m 2 / s}} (50 cSt) or less. The kinematic viscosity described in this specification was measured using AKV-201 manufactured by Tanaka Scientific Instruments, based on JIS K 2283. If the kinematic viscosity exceeds 200 X 10-6 m ² / s, it cannot be applied as a release agent to the mold cavity surface thinly and uniformly, and the amount applied per unit area increases. As a result, the total amount of gas to be volatilized by the molten metal exceeds the 10 cm ^3/100 g. In addition, if a release agent having a kinematic viscosity within the above range is used, the release agent applied to the mating surface of the movable mold and the fixed mold closes the gap between the movable mold and the fixed mold when the mold is clamped. It prevents the atmosphere from entering the cavity and plays a role in increasing the degree of vacuum in the mold cavity.

Additives to the synthetic oil include surfactants, preservatives, antiseptics, lubricants, viscosity modifiers, and the like. The amount of these additives is preferably 3% by mass or less based on the total amount of the synthetic oil so as not to impair the function of the synthetic oil.

In order to apply the release agent thinly and uniformly on the surface of the mold cavity, it is preferable to spray the release agent. Therefore, it is preferable not to use powders such as graphite, mica, tanolek, kaolin, boron nitride, and fluorinated graphite, or to set the particle size and the addition amount to such an extent as not to hinder fogging.

(2) Lubricant

In order to maintain the lubricity of the sleeve and the plunger, it is preferable to use a powder lubricant which does not substantially contain water. For example, metal oxides such as PbO, sulfides such as molybdenum disulfide and tungsten disulfide, ceramics, graphite, polymer compounds, etc. are added to wax or paraffin in an appropriate amount, and a granular powder of about 0.1 to 2 mm Preferably, it is in the body.

(3) anore mini alloy

The aluminum alloy that can be used in the present invention is not particularly limited, and examples thereof include aluminum alloys such as Al-Si-Cu, Al-Si-Mg, and Al-Mg, such as ADC3, ADC5, ADC10, and ADC12. For example, 5 to 20% by mass of Si, 1% or less of Mg, 10% or less of Cu, 1% or less of Ti, 1% or less of Fe, 1% or less of Mn, balance A1 and inevitable impurities Aluminum alloy or 2% or less Si, 1% or less Mg, 10% or less Cu, 1% or less Ti, 1% or less Fe, 1% or less Mn, balance A1 and inevitable impurities Strong aluminum alloys can be used.

Hydrogen dissolved in the aluminum alloy melt can be reduced to less than 0.2 cm3 / 100 g by degassing. The amount of oxygen及Pi carbon in the aluminum alloy in the molten metal is less than 0.1 cm ^3/100 g.

(4) Vacuum die casting equipment and decompression of mold cavity

If the depressurization of the mold cavity is sufficient, the residual gas in the manufactured product contains almost no nitrogen. Therefore, it is preferable that the degree of depressurization of the mold cavity be as follows.

The vacuum die-casting apparatus preferably has a mechanism for charging the molten metal in the holding furnace into the injection sleeve by reducing the pressure in the mold cavity. Specifically, a vacuum die casting apparatus 10 illustrated in FIGS.

The vacuum die casting apparatus 10 communicates with a cavity 16 formed by a fixed mold 16c attached to a fixed platen 16a, a movable mold 16d attached to a movable platen 16b, and a fixed mold 16c and a movable mold 16d. An injection sleeve 11 attached to a fixed die 16c, a plunger 12 moving back and forth within the injection sleeve 11, a holding furnace 13 below the injection sleeve 11 for accommodating the molten aluminum alloy M, and one end of the injection sleeve 11. The hot water supply pipe 14 has the other end 14a immersed in the molten metal M in the holding furnace 13, the cutoff pulp 18a communicates with the cavity 16, and the cavity 16 through a pipe 18b. A vacuum pump 18 for reducing the pressure in the cavity 16 to a vacuum state and sucking the molten metal M in the holding furnace 13 into the injection sleeve 11.

The holding furnace 13 is placed on a lift 15, and the level of the molten metal M is kept constant by moving the lift 15 up and down. The hot water supply pipe 14 is made of ceramic with an inner surface coated with BN to prevent a reaction with the molten metal M, and the lower end 14a is an orifice shape. The outer periphery of the hot water supply pipe 14 is surrounded by a heater (not shown), and keeps the hot water supply pipe 14 close to the temperature of the molten metal M.

As shown in FIG. 1, the vacuum die-casting apparatus 10 includes an apparatus 20 for applying a mold release agent made of a synthetic oil containing no water to the mold cavity 16 and an apparatus 30 for applying a non-aqueous lubricant to the sleeve 11. Have. Release agent coating device 20 is arm 22 A nozzle 21 for spraying a release agent is provided at the tip of the mold, and the release agent is sprayed on the surface of the mold cavity 16 with the movable die 16d opened from the fixed die 16c. The amount of the release agent used in each cycle is preferably 0.3 to 50 g / m ² , more preferably 1.0 to 25 g / m ² , based on the surface area of the mold cavity 16. The lubricant ejection device 30 has a nozzle 32 for spraying the powder lubricant 31 from the mold cavity side opening of the sleeve 11 when the mold is opened. The amount of the lubricant used per cycle is preferably 0.3 to 30 g / m ² , more preferably 0.5 to 20 g / m ² , based on the inner peripheral area of the sleep 11.

As shown in FIG. 4, with the movable mold 16d and the fixed mold 16c closed, the interior of the cavity 16 is evacuated to a vacuum (for example, 50 kPa or less, preferably 20 kPa or less, more preferably 10 kPa or less, particularly 5 kPa or less). kPa or less). Due to the reduced pressure in the cavity 16, the pressure inside the injection sleeve 11 is also reduced, and the molten metal M in the holding furnace 13 is loaded into the injection sleeve 11 via the hot water supply pipe 14 (FIG. 2). 2 ~: After evacuating the cavity 16 for L0 seconds, the plunger 12 is pushed into the sleeve 11, and the molten metal M is filled into the cavity 16 (Fig. 3). After the injection, the plunger 12 is retracted, the movable die 16d is separated from the fixed die 16c, and the solidified product is removed from the cavity 16.

Since the molten metal M can be manufactured without being brought into contact with the atmosphere by the vacuum die casting device 10, oxidation of the molten metal M and entrainment of gas are reduced. After the completion of the vacuum die-casting, a mold release agent is sprayed on the surfaces of the cavities of the fixed type 16c and the movable type 16d which are opened again, and a lubricant is sprayed on the inner surface of the sleep 11. By repeating this operation, a desired number of vacuum die-cast products are produced.

[3] Applications

The manufactured product obtained by the vacuum die-casting method of the present invention not only has a small residual gas amount but also a small proportion of hydrogen gas which causes brittleness during heat treatment and welding. There is little risk of generation of prestar and there is no decrease in mechanical strength. In addition, the vacuum die-cast product of the present invention has few oxides and inclusions, which are the major causes of the decrease in toughness. Therefore, it can be used as undercarriage parts for transportation equipment and vehicle body components that require high strength and high toughness. ' The present effort will be described in more detail by the following examples, but the present invention is not limited thereto. Example 1

Using a 1000-ton die-casting machine with the structure shown in Figs. 1-3, 9.3% Si, 0.5% Mg, 0.9% Fe, 0.1% Mn, 0.05% Cu, 0.07% An aluminum alloy containing Ni and 0.2% Zn (A360 of ASTM B85) was vacuum-die-casted to produce a snowmobile seat component 40 shown in FIG. The casting temperature of the die-cast melt was 670 ° C, and the gate speed of the melt was 20-40 m / sec at high speed.

The mold release agent is obtained by blowing air into atactic polypropylene melted at 220 ° C and oxidizing it.

[Wacker-Chemie Wacker TN manufactured by GMBH] is completely stirred and mixed. A small amount of fungicide was added to the mixture. The addition amount of each component, the silicone oil is 85 mass ^_0/0, § isotactic polypropylene 14.9 wt ^_0/0, fungicides 0.1 ^_0/0 der ivy. Kinematic viscosity at 40 ° C of the releasing agent was ^{5 10-6 m 2 /s~1.0 x 10 '} 4 m 2 / s ~ 100 cSt). This release agent was sprayed on the surface of the mold cavity 16 at a rate of 2.5 g / m ² per cycle.

Astrol powder GW-23 (manufactured by Hanano Shoji Co., Ltd.) containing Tanolek, natural graphite and synthetic wax as a powder lubricant was applied to the inner peripheral surface of the sleeve 11 at an amount of 1.5 g / m ² per cycle. Fog.

The vacuum die casting錶造product obtained under a reduced pressure of 4 out taken from the mold, the sprue portion near the mirror forming products Roiota, out disconnect the valve 18a adjacent portion P ₂ and a central portion P ₃ a test piece , each specimen was dissolved in 700 ° C in an Ar atmosphere in the vacuum chamber pressure was reduced to 4X 10- ³ kPa, the Ar carrier gas at a flow rate of the generated gas 50 ml / min, gas chromatographic analysis apparatus (GC -8AIT, manufactured by Shimadzu Corporation), and the total amount and composition of gas were measured by gas chromatography for 15 seconds. Sprue portion near Pi及Pi total residual gas in the valve vicinity of P ₂ (normal state) and composition, as well as the total amount of residual gas (standard state) and composition Table 1 shows the average value of Pa.

According to the JIS standard (JIS Z 2241), a 6.5 mm wide, 3 mm thick and 100 mm long plate-shaped test piece cut out from the vicinity of the gate of a vacuum die-cast product manufactured in the same manner Tensile strength, 0.2% strength and elongation were measured with a gauge length of 25 mm. Table 2 shows the results. Comparative Example 1

Vacuum die casting was performed in the same manner as in Example 1 except that silicone oil emulsion (trade name: TSM6352, manufactured by GE Toshiba Silicone Co., Ltd.) was used as a release agent. The silicone oil E Mar Ji is 15 mass% of modified recone oil, 2.0 wt ^_0/0 emulsion polypropylene, 0.3 wt% of Etokishii匕A alcohol emulsifier, 2.0 wt% of a corrosion inhibitor, with balance water Had. The silicone oil emulsion was further diluted 40 times with water and sprayed onto the surface of the mold cavity at a rate of 300 g / m ² per cycle.

The same measurement as in Example 1 was performed on a test piece cut out from the vicinity Pi of the obtained manufactured product. The results are shown in Tables 1 and 2. The gas remaining in the product of Comparative Example 1 was 8.8 cm3 / 100 g, which was not only larger than that in Example 1, but also a composition containing a large amount of H ₂ gas, C ₂ H ₆ gas and CH ₄ gas. Had. This is probably because an aqueous release agent was used. The mechanical strength of the product of Comparative Example 1 was lower than that of the product of Example 1. Example 2

In order to increase the amount of residual gas to be almost the same as in Comparative Example 1, the vacuum die-cast product was manufactured in the same manner as in Example 1 except that the amount of the chemically synthesized oil-based release agent was increased to 4.5 g / m ^2. Was fabricated, and the relationship between the composition of the residual gas and the mechanical strength of the manufactured product was examined. The residual gas amount in the test piece cut out from the part near the gate was Pi 7.7 cm3 / 100 g. Tables 1 and 2 show the residual gas composition and mechanical strength measured in the same manner as in Example 1. From Tables 1 and 2, it can be seen that the mechanical strength is clearly improved from Comparative Example 1, although the residual gas amount is almost the same as Comparative Example 1. Example 3

A vacuum die-cast product having a more complicated shape than in Example 1 was produced, and the total amount and composition of the residual gas were measured in the same manner as in Example 1. Table 1 shows the results. The total amount of residual gas is suppressed to 7.1 cm ^3/100 g, and H ₂ gas was less than the CO ₂ gas. Although Preparative On and Ho in Example 1 and different residual gas was N _2, this is because the mold Canon Activity has been made complicated shape than in Example 1, the degree of vacuum in Kiyabiti is about 25 kPa, It is considered that exhaust was not always sufficient. Comparative Example 2

A vacuum die casting having the same shape as in Example 1 was manufactured by a conventional vacuum die casting method in which the molten metal was supplied into the sleeve and then depressurized, and the total amount, composition, and mechanical properties of the residual gas were measured. First, the same aluminum alloy melt as in Example 1 was directly poured into the injection sleeve, the injection sleeve was air-tight, and then inert gas and the same release agent as used in Example 1 were supplied. The pressure inside the sleeve was reduced as follows. Thereafter, the plunger was advanced, and the molten metal was filled into the mold cavity. The cycle time was the same as in Example 1.

The total amount, composition, and mechanical strength of residual gas in the vicinity Pi of the gate of the obtained vacuum die-cast product were measured in the same manner as in Example 1. The results are shown in Tables 1 and 2. In Comparative Example 2, since the pressure in the mold cavity was reduced after pouring into the sleeve, the decompression time was short. Therefore, it can be seen that the inside of the sleeve was not sufficiently exhausted, and the amount of N ₂ and H ₂ was increased. Residual gas amount was 21.75 cm ^3/100. The mechanical strength of the product of Comparative Example 2 was very low. table 1

(2) Pa: average value.

Pi: Near the gate.

P ₂ : Near the vacuum pump. Table 2

Example 4

The vacuum die-cast product manufactured in Example 1 was placed in a heat treatment furnace at 500 ° C in an air atmosphere for 4 hours, and then poured into hot water at 60 ° C to perform a solution treatment (T6 treatment). . Next, the fabricated product was subjected to an aging treatment at 150 ° C for 2 hours. No blisters were generated on the surface of the article heat-treated in this way. This is closed This is probably because the shrinkage nest did not expand due to the heat treatment because the inside of the nest was almost vacuum.

A test piece was cut out from the heat-treated structure, and voids inside the structure were examined. Fig. 6 is a micrograph showing the metal structure of the manufactured product, and the dark portion in the center of Fig. 6 is a void. Most voids were shrinkage cavities formed during the solidification shrinkage of the molten aluminum alloy. It can be seen that the shrinkage cavities have a smooth shape and are almost in a vacuum state, so they do not cause a decrease in mechanical strength.

In order to examine whether or not the pre-star was generated by the heat treatment, the volume expansion coefficient of the product by the heat treatment was measured. Table 3 shows the results. Since the volume expansion coefficient after the heat treatment is small, it can be seen that there are few bubbles containing the residual gas serving as a prestar. No blistering was observed even when the product of Example 1 was welded. From these results, it can be seen that the manufactured product of Example 1 has extremely small variation in strength. Comparative Example 3

The article of Comparative Example 1 was subjected to a heat treatment in the same manner as in Example 4, and the presence or absence of the blister and the volume expansion coefficient were measured. Table 3 shows the results. Figure 7 shows the metal structure of this product. From Fig. 7, it can be seen that most of the voids contain residual gas and are almost granular. Therefore, as shown in Fig. 8, blisters were observed in the heat-treated product. Such structures do not have the mechanical strength required for use under conditions of severe vibration, such as undercarriage parts or body components of transportation equipment. When welding was performed on the product of Comparative Example 1, a pre-star occurred. Comparative Example 4

The heat-treated article of Comparative Example 2 was subjected to the same heat treatment as in Example 4, and the presence or absence of the blister and the volume expansion coefficient were measured. Table 3 shows the results. In Comparative Example 4, more blisters were generated than in Comparative Example 3. Table 3

Industrial applicability

As described in detail above, according to the present invention, it is possible to obtain a vacuum die-cast product of an aluminum alloy in which not only the amount of residual gas is small but also the amount of hydrogen in the residual gas is reduced. Such a vacuum die-cast product is suitable for undercarriage parts for transportation equipment and vehicle body components, etc., which require high strength and high toughness.

Claims

The scope of the claims

1. A vacuum die-cast product of an aluminum alloy, the gas remaining in the air bubbles of the vacuum die-cast product is H ₂ gas when measured by gas chromatography after being released by melting of the product. There vacuum die casting錶造article characterized by having a composition less than C0 ₂ gas.

2. claimed in vacuum die casting铸造product according to claim 1, vacuum die casting铸造product more than 50% of the total amount of the residual gas is characterized in that it is a C0 ₂ gas.

3. The vacuum die-cast product according to claim 1, wherein a total amount of the residual gas is 20 cms / 100 g or less at any position.

4. The vacuum die-cast product according to any one of claims 1 to 3, wherein a total amount of the residual gas is 10 cm3 / 100 g or less as an average of the entire product. .

5. In the vacuum die casting錶造article according to any one of claims 1 to 4, and wherein the 9 cms / 100 g or less der Rukoto average C0 ₂ gas of the entire鎵造product of the residual gas Vacuum die casting.

6. In the vacuum die casting铸造article according to any one of claims 1 to 5, H ₂ gas, 5 cm ^3/100 g or less total amount of CBU gas及Pi C ₂ H ₆ gas as an average for the entire铸造products A vacuum die-casting product characterized by the following.

7. The vacuum die-cast product according to any one of claims 1 to 6, wherein a ratio of H ₂ gas to the remaining gas is 15% or less.

8. The vacuum die cast product according to claim 7, wherein a ratio of H ₂ gas in the residual gas is 10% or less.

9. Claim: a vacuum die casting錶造article according to any one of 1-8, the total amount of the residual gas, CH ₄ gas, the total amount of C2H ₆ gas and CO gas is鍚造products overall Vacuum die-casting product characterized in that it is less than 20% on average.

10. The vacuum die-cast product according to any one of claims 1 to 9, wherein the vacuum die is used as a suspension part or a vehicle body component of a transportation device. Cast products.

11. After the molten aluminum alloy is loaded into the injection sleeve by reducing the pressure in the mold cavity, the plunger fitted to the injection sleeve is advanced to fill the molten metal in the injection sleep into the cavity. A method of producing a vacuum die-cast product by performing gas chromatography after gas remaining in bubbles of the vacuum die-cast product is released by dissolution of the product. as the gas having a composition less than co ₂ gas, vacuum die cast铸造product a synthetic oil which is substantially free of moisture and performing錶造after application to the mold Kiyabiti as a mold release agent Manufacturing method.

12. The method of manufacturing a vacuum die casting铸造article according to claim 11, said chemical synthetic oil comprises a silicone oil 70 mass% or more and a kinematic viscosity of less 200 X 10- ^² m ² / s Characterized by the method of manufacturing vacuum die-cast products.

13. The method for producing a vacuum die-cast product according to claim 11 or 12, wherein a lubricant substantially free of moisture is applied to the inside of the injection sleeve.