JP2014050872A - Die-casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die-casting method which is available for a wide variety of products and can extend sufficiently the time for solidification of a molten metal within a cavity.SOLUTION: Thermit reaction between a metal oxide powder and molten aluminum is caused in the time from supply of molten aluminum into an injection sleeve 20 to completion of low-speed movement of the molten aluminum to the tip 20a of the injection sleeve 20 through low-speed movement of a plunger tip 30, resulting in reduction of the metal oxide and oxidation of the aluminum. The heat of reaction of the thermit reaction heats the molten aluminum within the injection sleeve 20, and the molten aluminum heated is fed into a cavity 16. Although the molten aluminum fed into the cavity 16 is cooled because its heat is taken away by a mold 10, the cooling rate is low owing to heating by the heat of reaction of the thermit reaction, thereby leading to a sufficient extention of the time for solidification of the molten aluminum.

Description

  The present invention relates to a die casting method.

  If the mold cavity used for die casting is thin, the contact area of the molten metal to the mold (cavity wall surface) per unit injection amount of the molten metal injected into the cavity is large. It is rapidly cooled and solidified by the mold. When the solidification rate is extremely high, the molten metal solidifies before reaching the cavity, and a partially lost product is formed as a defective product. In order to suppress the occurrence of such defects, the time until the molten metal injected into the cavity solidifies is extended to ensure that the molten metal spreads over the entire area of the cavity, thereby obtaining a thin cast product with good accuracy. Techniques for this have been proposed.

  In Patent Document 1, a metal material (for example, zinc particles) having a composition that lowers the solidification temperature of the molten metal by being melted into the molten metal is supplied into the cavity of the mold, and then the molten metal is injected into the cavity. A die casting method for forming a cast product is disclosed. According to Patent Document 1, the molten metal injected into the cavity and the metal material (for example, zinc particles) previously supplied into the cavity are locally alloyed to lower the solidification temperature of the molten metal. As the solidification temperature of the molten metal decreases, the time until the molten metal injected into the cavity solidifies is extended.

Japanese Patent Laid-Open No. 2003-112243

(Problems to be solved by the invention)
According to Patent Document 1, theoretically, the time until the molten metal is solidified is extended by a decrease in the solidification temperature of the molten metal in the cavity. However, usually, in die casting, the molten metal is filled in the cavity in a short time of several tens to several hundreds of milliseconds, and then immediately cooled and solidified (solidified) from the portion in contact with the cavity wall surface. In this case, since the solidification temperature lowering due to alloying and the solidification of the molten aluminum due to cooling proceed simultaneously, there is a high possibility that the solidification of the molten metal proceeds before the molten metal is alloyed. In particular, when a thin-walled molded product is cast, solidification progresses quickly. Therefore, it seems that the method described in Patent Document 1 cannot substantially extend the time until the molten metal solidifies. In addition, since no exothermic reaction is involved, even if alloyed, if it is rapidly cooled by the mold, it is considered that the effect of delaying solidification of the molten metal due to a decrease in solidification temperature is small. Furthermore, since a metal material such as zinc particles is supplied into the cavity, it can be applied only to products in which such a metal material may adhere to the product surface. That is, applicable products are limited.

  An object of the present invention is to provide a die casting method that can be applied to a wide range of products and can sufficiently extend the time until the molten metal solidifies in the cavity.

(Means for solving the problem)
The present invention includes a mold having a cavity, a cylindrical shape having an internal space, an injection sleeve that communicates with the cavity on one end side thereof, and is movably disposed in the injection sleeve. A die-casting method of an aluminum product using a die-casting machine comprising a plunger tip, a metal oxide supplying step for supplying a metal oxide powder that causes a thermite reaction with aluminum into the injection sleeve, and the metal oxide A molten metal supplying step of supplying molten aluminum into the injection sleeve to which powder has been supplied, and aluminum supplied into the injection sleeve by moving the plunger tip at a low speed toward the one end side of the injection sleeve. A plunger low-speed moving step of moving the molten metal to the one end side of the injection sleeve; A plunger that injects the molten aluminum moved to the one end side of the injection sleeve in the plunger low-speed moving step into the cavity by moving the plunger tip at a high speed toward the one end side of the injection sleeve. A die casting method including a high-speed moving process.

  According to the die casting method of the present invention, after the molten aluminum is supplied into the injection sleeve in the molten metal supply step, the molten aluminum in the injection sleeve is moved to one end side of the injection sleeve in the plunger low-speed moving step. In the meantime, the thermite reaction is caused by the metal oxide powder and the molten aluminum, whereby the metal oxide is reduced and the aluminum is oxidized. The molten aluminum is heated in the injection sleeve by the reaction heat generated by the thermite reaction. The aluminum melt thus heated is supplied into the cavity in the plunger high-speed moving step. The molten aluminum supplied into the cavity is cooled by taking heat from the mold, but the cooling rate is slow because it is heated by the reaction heat generated by the thermite reaction. For this reason, the time until the molten aluminum solidifies in the cavity can be sufficiently extended.

  Further, since the thermite reaction mainly occurs in the injection sleeve, the metal and aluminum oxide generated by the thermite reaction are left in the injection sleeve and do not enter the cavity. Here, although the space in the injection sleeve communicates with the cavity of the mold, a runner, a gate, and the like are usually provided between the space in the injection sleeve and the cavity, and these spaces are interposed through the space. Thus, the space in the injection sleeve communicates with the cavity space. Since the runner and gate are formed as a very narrow space, the solid matter (metal or aluminum oxide) generated by the thermite reaction is blocked by the runner or gate. Therefore, only molten aluminum is supplied to the cavity space. Therefore, since an aluminum molded product with few impurities is produced, the present invention can be applied to a wide range of aluminum molded products.

In the above invention, any metal oxide powder may be used as long as it causes a thermite reaction with aluminum. Typically, triiron tetroxide (Fe ₃ O ₄ ) powder, tin dioxide (SnO ₂ ) powder, dichromium trioxide (Cr ₂ O ₃ ) powder, nickel oxide (NiO) powder, silicon dioxide (SiO ₂ ) Powder and manganese oxide (MnO) powder are suitably used as the metal oxide powder according to the present invention.

  The metal oxide supply step may be a step of supplying the metal oxide powder into the injection sleeve from the one end side of the injection sleeve in a state where the internal space of the injection sleeve is decompressed. According to this, since the internal space of the injection sleeve is depressurized, the metal oxide powder supplied from one end side (the side communicating with the cavity) of the injection sleeve does not move to the cavity side. Move into the injection sleeve. For this reason, metal oxide powder can be efficiently supplied into the injection sleeve. In this case, a suction pump may be connected to the other end side of the injection sleeve by piping or the like, and the internal space of the injection sleeve may be decompressed by operating the suction pump. According to this, the air in the injection sleeve is discharged and decompressed by the operation of the suction pump, and an air flow from one end of the injection sleeve toward the other end is generated in the injection sleeve. Therefore, the metal oxide powder supplied from one end side of the injection sleeve rides on the flow and moves in the injection sleeve. For this reason, the metal oxide powder can be supplied into the injection sleeve more efficiently.

  Further, the injection sleeve is formed with a molten metal supply port for supplying molten aluminum, and the molten metal supply port is preferably closed in the metal oxide supply step. According to this, it can prevent that the metal oxide powder supplied by the metal oxide supply process is discharge | released outside from the molten aluminum supply port.

  The metal oxide powder may be silicon dioxide powder. When the metal oxide is silicon dioxide, the heat of reaction generated when the molten aluminum and the silicon dioxide powder undergo a thermite reaction is very large. For this reason, it is possible to extend the time until the molten metal injected into the cavity is solidified.

It is the schematic of the die-casting machine to which the die-casting method concerning this embodiment is applied. It is a figure which shows the die-casting machine at the time of a preparation process. It is a figure which shows the die-casting machine at the time of a metal oxide supply process. It is a figure which shows the die-casting machine at the time of a molten metal supply port open | release process. It is a figure which shows the die-casting machine at the time of a molten metal supply process. It is a figure which shows the die-casting machine at the time of a plunger low-speed movement process. It is a figure which shows the die-casting machine at the time of a plunger high-speed movement process. It is a figure which shows the metal mold | die for a test. It is a graph which shows the temperature change of each temperature measurement site | part. The temperature of each part when 5 seconds have elapsed after supplying molten aluminum into the recess filled with metal oxide powder, and 5 after supplying molten aluminum into the recess not filled with metal oxide powder It is the graph which showed the difference (temperature difference) with the temperature of each site | part when 2 second passed for every metal oxide powder with which it fills.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of a die casting machine to which an aluminum product die casting method according to this embodiment is applied. In FIG. 1, the die casting machine 1 includes a mold 10, an injection sleeve 20, a plunger tip 30, a powder supply device 40, and a decompression device 50.

  The mold 10 includes a movable mold 13 attached to the movable mold plate 11 via a die base 12 and a fixed mold 15 attached to the fixed mold plate 14 and matched with the movable mold 13. The movable mold 13 is configured to be movable in a direction approaching and moving away from the fixed mold 15. When the mold matching surface of the movable mold 13 and the mold matching surface of the fixed mold 15 abut, a cavity 16 is formed between the mold matching surfaces. In this embodiment, the cavity 16 is formed thin. That is, a thin molded product is cast by injecting molten aluminum into the mold 10. Further, a sprue 17 communicating with the cavity 16 and a runner (plan portion) 18 communicating with the sprue are formed between both mold joining surfaces.

  A first passage 131 that opens to the runner 18 and a second passage 132 that has one end communicating with the first passage 131 and the other end opened to the outside are formed in the movable mold 13. A first hydraulic cylinder 61 is embedded in the movable mold 13. A shut-off pin 62 is connected to the first hydraulic cylinder 61, and the shut-off pin 62 moves in the first passage 131 when the first hydraulic cylinder 61 is driven. When the shutoff pin 62 advances to the right from the position shown in FIG. 1 and reaches the forward end position by driving the first hydraulic cylinder 61, the shutoff pin 62 opens the second passage 132 to the first passage 131. Block it. Thereby, the communication between the first passage 131 and the second passage 132 is blocked. When the communication between the first passage 131 and the second passage 132 is blocked by the shut-off pin 62, the shut-off pin 62 moves backward to the left in FIG. The first passage 131 and the second passage 132 communicate with each other.

The powder supply device 40 is connected to the other end side of the second passage 132. As shown in FIG. 1, the powder supply device 40 includes a powder filling tank 41, a pressure feeding device 42, and a supply pipe 43. A metal oxide powder is filled in the powder filling tank 41. The supply pipe 43 connects the powder filling tank 41 and the other end of the second passage 132. The pressure feeding device 42 sends the metal oxide powder in the powder filling tank 41 to the supply pipe 43 together with air. The metal oxide powder sent into the supply pipe 43 when the pumping device 42 is driven is further sent into the second passage 132. In this embodiment, triiron tetroxide (Fe ₃ O ₄ ) powder is exemplified as the metal oxide powder, but any metal oxide (for example, silicon dioxide powder) that causes a thermite reaction with aluminum can be used. Metal oxide powder may be used.

  An injection sleeve 20 is provided so as to penetrate the fixed mold plate 14 and the fixed mold 15. The injection sleeve 20 is formed in a cylindrical shape so as to have an internal space, and its tip (one end) 20 a opens in the die-matching surface of the fixed die 15. When the mold 10 is in the mold-clamping state, the injection sleeve 20 communicates with the cavity 16 through the runner 18 and the gate 17 on the tip 20a side. A molten metal supply port 21 is formed in the side peripheral wall near the rear end (the other end) 20b of the injection sleeve 20 so as to open. The molten aluminum is supplied into the injection sleeve 20 from the molten metal supply port 21.

  A second hydraulic cylinder 63 is attached to the fixed mold platen 14. A rod 64 is connected to the second hydraulic cylinder 63. A sealing plate 65 is attached to the tip of the rod 64. The shape of the sealing plate 65 substantially matches the shape of the molten metal supply port 21. When the rod 64 is advanced downward in FIG. 1 by driving the second hydraulic cylinder 63 and reaches the forward end position, the sealing plate 65 attached to the tip of the rod 64 blocks the molten metal supply port 21. In this state, the molten aluminum cannot be supplied into the injection sleeve 20 from the molten metal supply port 21. When the second hydraulic cylinder 63 is driven and the rod 64 is retracted upward in FIG. 1 while the sealing plate 65 is blocking the molten metal supply port 21, the sealing plate 65 is also raised and the molten metal supply port 21 is opened. The In the state where the molten metal supply port 21 is opened, the molten aluminum can be supplied from the molten metal supply port 21 into the injection sleeve 20.

  A through hole 651 is formed in the sealing plate 65, and the decompression device 50 is connected to the through hole 651. The decompression device 50 includes a vacuum pump (suction pump) 51, a filter 52, an opening degree adjusting valve 53, and a pipe 54. One end of the pipe 54 is connected to the through hole 651, and the other end of the pipe 54 is connected to the vacuum pump 51. A filter 52 and an opening adjustment valve 53 are interposed in the middle of the pipe 54. When the vacuum pump 51 is operated in a state where the molten metal supply port 21 is closed with the sealing plate 65, the air in the injection sleeve 20 is guided to the vacuum pump 51 through the pipe 54. Thereby, the inside of the injection sleeve 20 is depressurized.

  A plunger tip 30 is provided in the injection sleeve 20. The plunger tip 30 is configured to reciprocate within the injection sleeve 20 by driving a hydraulic cylinder (not shown).

  A method for die casting of an aluminum product using the die casting machine 1 having the above configuration will be described below. 2 to 7 are diagrams showing the die casting method according to the present embodiment using the die casting machine 1 for each process.

<Preparation process>
First, the movable mold 13 and the fixed mold 15 are opened, and a mold release agent is applied to a mold wall surface (mold matching surface) that forms the cavity 16 and the runner 18. After the release agent is applied, the mold 10 is closed. Further, a lubricant is applied in the injection sleeve 20. After applying the lubricant, the plunger tip 30 is retracted to the vicinity of the rear end 20b of the injection sleeve 20. When the plunger tip 30 is retracted to the position shown in FIG. 1, the molten metal supply port 21 formed in the injection sleeve 20 is located in front of the plunger tip 30 (leftward in FIG. 1). Therefore, the molten aluminum supplied from the molten metal supply port 21 is filled in the portion of the injection sleeve 20 between the tip 20a of the injection sleeve 20 and the plunger tip 30.

  Further, as shown in FIG. 2, the first hydraulic cylinder 61 is driven to retract the shut-off pin 62 to the left in FIG. When the shut-off pin 62 is retracted to the retracted end position shown in FIG. 2, the first passage 131 and the second passage 132 communicate with each other. Further, the second hydraulic cylinder 63 is driven to advance the rod 64 downward in FIG. When the rod 64 has advanced to the forward end position shown in FIG. 2, the melt supply port 21 formed in the injection sleeve 20 is blocked by the sealing plate 65.

<Metal oxide supply process>
Next, the vacuum pump 51 is operated. Then, the air in the injection sleeve 20 flows from the front end 20 a side to the rear end 20 b side of the injection sleeve 20, and the air flowing to the rear end 20 b side is sucked into the vacuum pump 51 through the pipe 54. Thereby, the inside of the injection sleeve 20 is depressurized. When the pressure in the injection sleeve 20 is reduced to a predetermined pressure, the powder supply device 40 is operated. As a result, the ferric tetroxide powder filled in the powder filling tank 41 enters the second passage 132 through the supply pipe 43, and further enters the first passage 131 from the second passage 132. Since the first passage 131 is open to the runner 18, the triiron tetroxide powder enters the runner 18. The runner 18 communicates with the cavity 16 through the gate 17 and communicates with the space in the injection sleeve 20 on the tip 20a side of the injection sleeve 20. Here, since the space in the injection sleeve 20 is depressurized by the operation of the vacuum pump 51 and airflow is generated from the front end 20a side to the rear end 20b side of the injection sleeve 20, the air enters the runner 18. Most of the ferric oxide tetraoxide powder (metal oxide powder) is supplied into the injection sleeve 20 as shown in FIG. At this time, by adjusting the opening degree of the opening degree adjusting valve 53, the supply amount of the triiron tetraoxide powder into the injection sleeve 20 can be adjusted. Further, the triiron tetroxide powder that has entered the pipe 54 from the injection sleeve 20 is captured by the filter 52. This prevents the ferric tetroxide powder from entering the vacuum pump 51.

<Process for opening molten metal supply port>
After supplying a predetermined amount of triiron tetroxide powder into the injection sleeve 20, the operation of the powder supply device 40 is stopped and the operation of the vacuum pump 51 is stopped. Thereafter, the second hydraulic cylinder 63 is driven to retract the rod 64 upward in FIG. As a result, as shown in FIG. 4, the sealing plate 65 that has blocked the molten metal supply port 21 rises and the molten metal supply port 21 is opened. Further, the first hydraulic cylinder 61 is driven to advance the shut-off pin 62 to the right in FIG. When the shut-off pin 62 reaches the forward end position shown in FIG. 4, the communication between the first passage 131 and the second passage 132 is blocked.

<Melt supply process>
Next, the molten aluminum filled in a molten metal tank (not shown) is poured with a ladle R. Then, the molten aluminum sprinkled by the ladle R is poured into the injection sleeve 20 from the molten metal supply port 21. Thereby, as shown in FIG. 5, the molten aluminum accumulates in a portion between the tip 20 a of the injection sleeve 20 and the plunger tip 30.

<Plunger low-speed movement process>
Next, a hydraulic cylinder (not shown) is driven to move the plunger tip 30 forward from the position shown in FIG. 5 to the left, that is, toward the tip 20 a side of the injection sleeve 20. At this time, the plunger tip 30 is moved at a low speed (for example, 0.2 m / sec.). Due to the low speed movement of the plunger tip 30, as shown in FIG. 6, the molten aluminum accumulated in front of the plunger tip 30 (leftward in FIG. 6) moves to the tip 20 a side of the injection sleeve 20 and reaches the runner 18. Filled with molten aluminum.

上記化学式（１）からわかるように、テルミット反応は発熱反応である。したがって、テルミット反応で生じた反応熱がアルミニウム溶湯に加えられることによってアルミニウム溶湯が加熱される。すなわち本実施形態によれば、射出スリーブ２０内でテルミット反応を起こさせることにより、アルミニウム溶湯が３〜１０秒間に亘り、テルミット反応の反応熱により射出スリーブ２０内で加熱される。例えば、供給されるアルミニウム溶湯が５００ｇであり、供給される四酸化三鉄粉末が１ｇであり、全ての四酸化三鉄粉末がアルミニウムと反応した場合、射出スリーブ２０内のアルミニウム溶湯は、理論上は１０．３℃温度上昇する。 After the molten aluminum is supplied into the injection sleeve 20 in the molten metal supply step, the plunger 30 moves in the injection sleeve 20 at a low speed in the plunger low-speed movement step to move the molten aluminum to the tip 20a side of the injection sleeve 20. It takes about 3 to 10 seconds from when the molten aluminum is supplied into the injection sleeve 20 to when the plunger low-speed moving process is completed. During this time, the molten aluminum in the injection sleeve 20 comes into contact with the triiron tetroxide powder, the thermite reaction shown in the following chemical formula (1) occurs, the triiron tetroxide is reduced to produce iron, and the aluminum is oxidized. As a result, aluminum oxide is produced.

As can be seen from the chemical formula (1), the thermite reaction is an exothermic reaction. Therefore, the molten aluminum is heated by the reaction heat generated by the thermite reaction being added to the molten aluminum. That is, according to this embodiment, by causing a thermite reaction in the injection sleeve 20, the molten aluminum is heated in the injection sleeve 20 by the reaction heat of the thermite reaction for 3 to 10 seconds. For example, when the supplied molten aluminum is 500 g, the supplied triiron tetroxide powder is 1 g, and all the ferric tetroxide powder reacts with aluminum, the molten aluminum in the injection sleeve 20 is theoretically Increases by 10.3 ° C.

<Plunger high-speed movement process>
After the plunger tip 30 moves forward to a desired position and the plunger low-speed moving step is completed, the moving speed of the plunger tip 30 is switched from a low speed to a high speed (for example, 2 m / s). That is, the plunger tip 30 is moved at a high speed toward the tip 20 a side of the injection sleeve 20. Due to the high-speed movement of the plunger tip 30, the molten aluminum that has been moved to the tip 20 a side of the injection sleeve 20 and filled up to the runner 18 in the plunger low-speed movement process is injected into the cavity 16 through the gate 17. At this time, the molten aluminum injected into the cavity 16 is heated by the reaction heat generated by the above-described thermite reaction, so the time until the mold 10 is deprived of heat and solidifies is extended. For this reason, it is effectively prevented that the molten aluminum solidifies before reaching all the parts of the cavity 16. As a result, it is possible to die-cast an aluminum product with good accuracy with no defects.

  Further, since the runner 18 and the gate 17 are narrow (particularly, the width of the gate 17 is extremely narrow), solids such as iron and aluminum oxide generated in the injection sleeve 20 due to the thermite reaction are transferred to the runner 18 and the gate 17. The dams are prevented from entering the cavity 16. Most of these products are deposited on the biscuits Bi formed near the tip 20a of the injection sleeve 20, as shown in FIG.

<Pressurization and removal process>
After the plunger high-speed movement step, a constant pressure is applied from the plunger tip 30 to the cavity 16 side (pressure holding step). After a predetermined time has elapsed, the plunger tip 30 is retracted toward the rear end 20b of the injection sleeve 20, and the mold 10 is opened to take out the product in the cavity 16. A die cast product is manufactured through the above steps.

(Confirmation of heating of molten aluminum by thermite reaction)
The effect of this embodiment was confirmed using the test mold 70 shown in FIG. The test mold 70 has a prismatic shape with a height of 120 mm, and the cross-sectional shape perpendicular to the height direction is a square with a side of 100 mm. Further, the test mold 70 is formed with an inverted frustoconical recess 71 opened at the upper end surface thereof. The height of the recess 71 is 100 mm, the diameter of the opening circle is 60 mm, and the diameter of the bottom circle is 40 mm. The molten aluminum was poured into the concave portion 71 from the upper end opening by using gravity, and the concave portion 71 was filled with the molten aluminum. At this time, the temperature change of the molten aluminum in the recess 71 when the bottom portion of the recess 71 is preliminarily filled with metal oxide powder that causes a thermite reaction with aluminum, and the recess when the recess 71 is not filled with anything. The temperature change of the molten aluminum in 71 was measured. The temperature measurement sites are sites A, B, and C shown in FIG. The position of the part A is a depth position of 40 mm from the center of the upper end opening circle of the concave part 71, the position of the part B is a depth position of 70 mm from the center of the upper end opening circle of the concave part 71, and the position of the part C is the concave part. The depth position is 95 mm from the center of the upper end opening circle of 71. Other test conditions are as shown below.
-Material of molten aluminum poured into the recess 71: ADC12
-Temperature of molten aluminum poured into the recess 71: 700 ° C
・ Temperature of test mold 70: 250 ° C. ± 15 ° C.
・ Types of metal oxide to be filled: SiO ₂ , CuO, Fe ₃ O ₄
-Amount of metal oxide powder to fill: 3 g

  FIG. 9 is a graph showing the temperature change at each temperature measurement site. FIG. 9 (a) shows the temperature change at site A, FIG. 9 (b) shows the temperature change at site B, and FIG. 9 (c) shows the site change. The temperature change of C is represented respectively. The horizontal axis of each graph is the elapsed time (seconds) after supplying the molten aluminum to the recess 71, and the vertical axis is the measured temperature (° C.) of each part. In each graph, the graph created by connecting the temperature measurement values indicated by ◯ represents the temperature change of each part when the molten aluminum is supplied to the recess 71 not filled with the metal oxide, and indicated by Δ. The graph created by connecting the measured temperature values represents the temperature change when the molten aluminum is supplied to the recess 71 filled with the triiron tetroxide powder as the metal oxide powder, and the measured temperature value indicated by × The graph created by linking represents the temperature change when supplying molten aluminum to the recess 71 filled with silicon dioxide powder as the metal oxide powder, and the graph created by linking the temperature measurement values indicated by □, It represents a temperature change when molten aluminum is supplied to the recess 71 filled with copper oxide powder as a metal oxide powder.

  As can be seen from FIG. 9, when the metal oxide powder is filled in the recess 71, the temperature of the molten aluminum at the same elapsed time is higher than when it is not filled. From this, it can be seen that when molten aluminum is supplied to the recess 71 filled with the metal oxide powder, a thermite reaction occurs in the recess 71, and the molten aluminum in the recess 71 is heated by the reaction heat, and the temperature rises. .

  Moreover, in all the measurement parts (part A, part B, part C) in the recessed part 71, when the metal oxide powder is filled into the recessed part 71, compared with the case where it is not filled, it is the same elapsed time. The temperature of the molten aluminum is high. From this, it can be seen that the molten aluminum is heated by the reaction heat of the thermite reaction throughout the recess 71.

  FIG. 10 shows the temperature T1 of each part when 5 seconds have passed since the molten aluminum was supplied into the recess 71 filled with the metal oxide powder, and the aluminum in the recess 71 not filled with the metal oxide powder. It is the graph which showed the difference (temperature difference T1-T2) with respect to temperature T2 of each site | part when 5 seconds passed since supplying molten metal for every metal oxide powder with which it fills. As can be seen from FIG. 10, regardless of the difference in the metal oxide powder, the temperature difference at the site C, that is, the temperature difference at the position closest to the bottom surface position of the recess 71 filled with the metal oxide is the largest. In addition, when silicon dioxide powder is used as the metal oxide powder, the temperature difference is very large compared to the case where other metal oxide powders are used. From this, it was found that the use of silicon dioxide powder as the metal oxide powder allowed the longest time from injection of molten aluminum into the cavity to solidification of the molten aluminum.

ここで、Ｔ_０はキャビティに充填する直前の射出スリーブ内のアルミニウム溶湯温度（Ｋ）、Ｔはキャビティ内で流動が停止したときのアルミニウムの温度（Ｋ）、Ｔ_ｍは金型温度（Ｋ）、ｈはアルミニウム金属から金型への熱伝達率（Ｗ／ｍ^２Ｋ）、Ｌは、成形される鋳造品の周長（アルミニウム溶湯が流れる方向に垂直な断面における鋳造品の外周の長さ）（ｍ）、Ｘは流動長（ｍ）、ρはアルミニウムの比重（ｋｇ／ｍ^３）、Ｃｐはアルミニウムの比熱（Ｊ／ｋｇ・Ｋ）、ｕはキャビティを流れるアルミニウム溶湯の流速（ｍ／ｓ）、Ａはキャビティの断面積（ｍ^２）である。 Incidentally, the flow length of an aluminum die-cast product can be obtained based on the following formula.

Here, T ₀ is the molten aluminum temperature (K) in the injection sleeve immediately before filling the cavity, T is the aluminum temperature (K) when the flow stops in the cavity, and T _m is the mold temperature (K). , H is the heat transfer coefficient from the aluminum metal to the mold (W / m ² K), and L is the circumference of the cast product to be formed (the length of the outer periphery of the cast product in a cross section perpendicular to the direction in which the molten aluminum flows) ) (M), X is the flow length (m), ρ is the specific gravity of aluminum (kg / m ³ ), Cp is the specific heat of aluminum (J / kg · K), u is the flow velocity of the molten aluminum flowing through the cavity (m / s), A is the cross-sectional area (m ² ) of the cavity.

  As can be seen from the above formula, there is a correlation between the molten aluminum temperature in the injection sleeve and the flow length, and the higher the molten aluminum temperature in the injection sleeve, the longer the flow length. Therefore, depending on the required flow length (that is, the length of the thinly formed cavity), the type of the metal oxide powder is appropriately selected so that the temperature of the molten aluminum rises to the temperature for obtaining the flow length. can do.

  As described above, in the die casting method of the present embodiment, the metal oxide supplying step of supplying the metal oxide powder causing the thermite reaction with aluminum into the injection sleeve 20, and the injection sleeve 20 supplied with the metal oxide powder. The molten metal supply process for supplying molten aluminum into the inside, and the plunger tip 30 is moved at a low speed toward the distal end 20 a side of the injection sleeve 20, so that the molten aluminum supplied into the injection sleeve 20 is transferred to the distal end 20 a side of the injection sleeve 20. And a plunger low-speed moving step for discharging air between the plunger tip 30 and the tip 20a of the injection sleeve 20 and a high-speed movement of the plunger tip 30 toward the tip 20a of the injection sleeve 20 The tip 20a side of the injection sleeve 20 in the low-speed movement process The moving aluminum melt including a plunger speed movement step of injecting into the cavity 16.

  According to the die casting method according to this embodiment, after the molten aluminum is supplied into the injection sleeve 20 in the molten metal supply process, the molten aluminum in the injection sleeve 20 is moved to the tip 20a side of the injection sleeve 20 in the plunger low-speed movement process. In the meantime, the thermite reaction is caused by the metal oxide powder and the molten aluminum, thereby reducing the metal oxide and oxidizing the aluminum. The molten aluminum is heated in the injection sleeve 20 by reaction heat generated by the thermite reaction. The molten aluminum thus heated is supplied into the cavity 16 in the plunger high-speed moving step. The molten aluminum supplied into the cavity 16 is cooled by being deprived of heat by the mold 10, but the cooling rate is slow because it is heated by the reaction heat generated by the thermite reaction. For this reason, the time until the molten aluminum solidifies in the cavity 16 can be extended sufficiently.

  The thermite reaction mainly occurs in the injection sleeve 20, and the thermite reaction and generation of reaction heat accompanying the reaction are not affected by the cooling action of the mold 10. That is, the heating of the molten aluminum by the thermite reaction and the cooling of the molten aluminum by the mold 10 do not proceed simultaneously. For this reason, the molten aluminum can be reliably heated in the injection sleeve 20. In addition, since the time required for the plunger low-speed movement process to be completed after the molten aluminum is supplied to the injection sleeve 20 is as long as about 3 to 10 seconds, the thermite reaction can be sufficiently caused in the injection sleeve 20. Therefore, the molten aluminum can be sufficiently heated in the injection sleeve 20.

  Further, metal, aluminum oxide, or the like is generated in the injection sleeve 20 by the thermite reaction. Here, the space in the injection sleeve 20 communicates with the cavity 16 via the runner 18 and the gate 17. Since the runner 18 and the gate 17 are formed as a narrow space, the solid matter (metal or aluminum oxide) generated by the thermite reaction is blocked by the runner 18 or the gate 17. Therefore, only the molten aluminum is supplied to the cavity 16, and the solid matter generated by the thermite reaction is deposited on the biscuits Bi formed near the tip 20 a of the injection sleeve 20. Therefore, since an aluminum molded product with few impurities is produced | generated, a wide aluminum molded product can be manufactured.

  Further, in the metal oxide supply step, metal oxide powder is supplied into the injection sleeve 20 from the tip 20a side of the injection sleeve 20 in a state where the internal space of the injection sleeve 20 is decompressed. By depressurizing the internal space of the injection sleeve 20, the metal oxide powder supplied from the tip 20a of the injection sleeve 20 can be moved into the injection sleeve 20 without moving to the cavity 16 side. Therefore, the metal oxide powder can be efficiently supplied into the injection sleeve 20. Further, a vacuum pump 51 is connected to the portion near the rear end 20b of the injection sleeve 20 by a pipe 54, and the vacuum pump 51 is operated to reduce the internal space of the injection sleeve 20. For this reason, the air in the injection sleeve 20 is discharged and decompressed by the operation of the vacuum pump 51, and a flow from the front end 20 a side to the rear end 20 b side of the injection sleeve 20 is generated in the injection sleeve 20. Therefore, the metal oxide powder supplied from the tip 20a side of the injection sleeve 20 rides on the flow and moves in the injection sleeve 20. Therefore, the metal oxide powder can be supplied into the injection sleeve 20 more efficiently.

  The injection sleeve 20 is formed with a molten metal supply port 21 for supplying molten aluminum. In the metal oxide supply process, the molten metal supply port 21 is closed with a sealing plate 65. For this reason, the metal oxide powder supplied into the injection sleeve 20 is prevented from being discharged from the molten metal supply port 21 to the outside. In addition, when silicon dioxide is used as the metal oxide powder, a large reaction heat can be generated, so that the time from when the molten aluminum is injected into the cavity 16 to solidification can be extended longer.

DESCRIPTION OF SYMBOLS 1 ... Die casting machine, 10 ... Die, 13 ... Movable type, 15 ... Fixed type, 16 ... Cavity, 17 ... Spout, 18 ... Runner, 20 ... Injection sleeve, 20a ... Front end (one end), 20b ... Rear end ( The other end), 21 ... molten metal supply port, 30 ... plunger tip, 40 ... powder supply device, 41 ... powder filling tank, 42 ... pressure feeding device, 43 ... supply pipe, 50 ... decompression device, 51 ... vacuum pump (suction pump) 52 ... Filter, 53 ... Opening adjustment valve, 54 ... Piping, 61 ... First hydraulic cylinder, 62 ... Shut-off pin, 63 ... Second hydraulic cylinder, 64 ... Rod, 65 ... Sealing plate, 70 ... For testing Mold, 71 ... recess, 131 ... first passage, 132 ... second passage, 651 ... through hole

Claims (4)

A mold in which a cavity is formed, an injection sleeve which is formed in a cylindrical shape so as to have an internal space and communicates with the cavity on one end side thereof, and a plunger tip which is movably disposed in the injection sleeve; A die casting method for aluminum products using a die casting machine comprising:
A metal oxide supplying step for supplying a metal oxide powder that causes a thermite reaction with aluminum in the injection sleeve;
A molten metal supplying step of supplying molten aluminum into the injection sleeve supplied with the metal oxide powder;
A plunger low-speed moving step of moving the molten aluminum supplied into the injection sleeve to the one end side of the injection sleeve by moving the plunger tip at a low speed toward the one end side of the injection sleeve;
A plunger that injects the molten aluminum moved to the one end side of the injection sleeve in the plunger low-speed moving step into the cavity by moving the plunger tip at a high speed toward the one end side of the injection sleeve. A high-speed movement process;
Including die casting method. In the die-casting method according to claim 1,
The metal oxide supply step is a step of supplying the metal oxide powder into the injection sleeve from the one end side of the injection sleeve in a state where the internal space of the injection sleeve is decompressed. . In the aluminum die-cast molding method according to claim 2,
A molten metal supply port for supplying molten aluminum is formed in the injection sleeve, and the molten metal supply port is closed in the metal oxide supply step. In the aluminum die-casting molding method according to any one of claims 1 to 3,
The aluminum oxide powder casting method, wherein the metal oxide powder is silicon dioxide powder.

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