JPH10140260A - Method of precast forming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forming method of semi-molten metal which simply and easily obtains a formed body having fine and spherical thixo-structure in a low cost without using the conventional mechanical stirring method or electromagnetic stirring method. SOLUTION: An alloy M having crystal nuclei, in liquid-state at the liquidus temp. or higher, poured into a holding vessel 30 having >=1kcal/m.h. deg.C heat conductivity, or an alloy having crystal nuclei in solid-liquid coexisting state at less than the liquidus temp. and the forming temp. or higher, is cooled at 0.01 deg.C/s-3.0 deg.C/s average cooling velocity and held just before pressing and forming to crystalize the fine primary crystal in molten alloy. Then, the temp. is adjusted so as to keep the temp. at each part of the alloy incorporated in the holding vessel 30 into the range of a target forming temp. showing a prescribed liquid phase ratio at least till forming with the induction-heating, and this alloy is taken out from the holding vessel and supplied into a metallic mold 60 for forming and press-formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a semi-molten metal, and more particularly, to a liquid alloy having a crystal nucleus poured into a holding vessel, which is in a liquid state at a liquidus temperature or higher, or a liquid having a crystal nucleus. An alloy in a solid-liquid coexisting state at a temperature lower than the phase line temperature or higher than the forming temperature is cooled at an average cooling rate within a certain range and held until immediately before pressure forming, whereby a fine primary crystal is crystallized in the alloy liquid. At the same time, the temperature of each part of the alloy placed in the holding container is adjusted by induction heating so as to fall within a target forming temperature range showing a predetermined liquidus ratio at the latest by the time of forming, and The method of the present invention relates to a method for forming a semi-molten metal in which the alloy is taken out from the mold and supplied to a molding die to perform pressure molding.

[0002]

2. Description of the Related Art Thixocasting has attracted attention recently because it has fewer casting defects and segregation than conventional casting methods, has a uniform metal structure, has a long mold life, and has a short molding cycle. Technology. This molding method (A)
The billet used in (1) is characterized by a spheroidized structure obtained by performing mechanical stirring or electromagnetic stirring in a semi-melting temperature range or utilizing recrystallization after processing. On the other hand, a method of semi-solid molding using a material obtained by a conventional casting method is also known. This is because, for example, a method (B) of adding Zr or a method of using a carbon-based refining agent (C) to generate finer crystals in a magnesium alloy that easily generates an equiaxed crystal structure.
And (D) a method of adding an Al-5% Ti-1% B master alloy as a refining agent to an aluminum alloy in a ratio of about 2 to 10 times that of a conventional aluminum alloy. This is a method in which the primary crystals are heated to a temperature range to form spheroids and molded. Also, for alloys within the solid solubility limit, after heating relatively quickly to a temperature near the solidus, the material exceeds the solidus in order to equalize the temperature of the entire material and prevent local melting. A method (E) of forming by heating gently to an appropriate temperature at which the material is softened is known. Further, a method (F) is known in which a molten aluminum at about 700 ° C. is flowed through an inclined cooling plate to obtain semi-molten aluminum, which is collected in a container and cooled.

On the other hand, unlike a method in which a billet is heated to a semi-melting temperature range and formed, a melt containing a spherical primary crystal is continuously produced and formed without being solidified as a billet. The casting method (G) is known. Further, a method (H) of obtaining a slurry for rheocasting by maintaining a metal, at least a part of which is in a solid-liquid coexistence state, in a semi-molten temperature range by bringing a molten metal into contact with a cooling body and an inclined cooling body is provided. Are known. Further, the molten metal accommodated in the billet case is cooled from the outside of the container or directly into the container while applying ultrasonic vibration to produce a semi-solidified billet, and the semi-solidified billet is taken out from the billet case, and is taken out as it is. A casting apparatus (I) for molding or reheating with a high-frequency induction device to form is known.

[0004]

However, the method (A) described above is complicated in both cases of the stirring method and the method utilizing recrystallization, and has a drawback that the production cost is increased. Further, in the case of magnesium alloy (B), Zr is high, which is a problem in terms of cost. In the method (C), a carbide-based refining agent is used to sufficiently exhibit the refining effect. It is necessary to control Be, which is an antioxidant element, to a low level of, for example, about 7 ppm, which is liable to be oxidized and burned during a heat treatment immediately before molding, which is inconvenient in operation.

On the other hand, in the case of aluminum alloys, the mere addition of a refining agent is about 500 μm,
It is not easy to obtain a structure of fine crystal grains of 00 μm or less. For this reason, there is a method (D) of adding a large amount of a fine agent, but the fine agent easily sediments at the furnace bottom and is industrially difficult and costly. Further, in the method (E), a thixo-molding method characterized by uniform heating and spheroidization of the material by gradually heating after exceeding the solidus line has been proposed. However, it does not change into the thixo structure (the primary dendrite is spheroidized). According to the method (F), semi-molten aluminum exhibiting a structure of spherical particles can be easily obtained, but conditions for molding as it is are not yet established.

Moreover, in any of the cases (A) to (F),
In order to perform semi-solid molding by the thixo molding method, it is necessary to solidify the liquid phase once and raise the billet again to the semi-molten temperature range, which increases the cost compared with the conventional casting method,
In addition, the billet as a raw material is difficult to recycle, and the liquid phase ratio cannot be increased due to billet handling problems. In the method (G), since the melt containing the spherical primary crystal is continuously generated and supplied, it is more advantageous in terms of cost and energy than thixocast, but the metal comprising the spherical structure and the liquid phase is advantageous. The interlocking of equipment between a machine for producing raw materials and a casting machine for producing final products is complicated. Specifically, when the casting machine fails, the treatment of the semi-molten metal is troublesome.

Further, the method (H) has the following problems. Although it is supposed to be kept in the latter half melting temperature range for a predetermined time in contact with the cooling body, unlike the thixocast method, which is once solidified to form a billet and then molded after reheating, for a predetermined time In the case of forming the semi-molten metal after holding as it is, considering an industrial continuous operation, it is necessary to obtain an alloy having a predetermined liquid phase ratio and a good temperature distribution suitable for forming in a short time. However, it is not possible to obtain a semi-molten metal for rheocasting having a liquid phase ratio and a temperature distribution suitable for molding simply by holding.

In the method (I), a container for cooling the molten metal in the container is used. The upper and lower portions of the metal in the container are easier to cool than the central portion, and a semi-solidified billet having a uniform temperature distribution is obtained. It is difficult. For this reason, if molded as it is, a molded body having an uneven structure can be obtained. In addition, the temperature of the semi-solidified billet once taken out of the billet case needs to maintain the original form of the billet, so that the liquid phase ratio of the semi-solidified billet is difficult to exceed 50%. Therefore, the liquid phase ratio must be about 40%, and therefore, the molding by die casting requires some improvement in injection conditions and the like. Even if the billet once having a liquidus ratio of less than 40% is reheated by a high-frequency induction device, it is difficult to exceed 50% similarly. is there. Also, since it takes time to eliminate the large non-uniformity of the temperature in the semi-solidified billet once formed, the output of the high-frequency device is also necessary although temporarily a high output close to the case of thixo molding,
In addition, it is necessary to install many high-frequency induction devices for high-cycle continuous production.

[0009] In addition, when performing semi-solid molding continuously on an industrial scale, if a casting machine fails, the retention time of the metal in the semi-molten state may be longer than a predetermined retention time.
Unless there is a problem with the metal structure, it is desirable to maintain the temperature at a predetermined temperature. In particular, in the case of the thixocast method in which the temperature is raised from room temperature and held, the metal structure becomes coarse and the billet shape is greatly deformed (the lower part of the billet). The larger the diameter),
In addition, if the temperature of each billet in a semi-molten state cannot be individually controlled, in such a case, it is wasteful because the billet is usually discarded.

The present invention focuses on the problems of the above-mentioned conventional methods, and can easily and easily form a uniform structure containing a spherical primary crystal without using a billet and without using a complicated method. And semi-molten metal suitable for molding with a uniform temperature distribution (up to the semi-molten metal with a higher liquid phase rate than the conventional thixocast method), using a high frequency induction device usually used for thixocast molding It is an object of the present invention to provide a method for obtaining a powder quickly with an output of 50% or less and performing pressure molding.

[0011]

In order to solve such a problem, according to the present invention, in the first invention, a crystal nucleus poured into a holding vessel having a thermal conductivity of 1 kcal / mh ° C. or more is used. An alloy in a liquid state having a liquidus temperature equal to or higher than the liquidus temperature or a solid-liquid coexisting state having a crystal nucleus lower than the liquidus temperature but equal to or higher than the forming temperature is applied at a temperature of 0.01 ° C / s to 3.0 ° C / s. By cooling at an average cooling rate and holding until just before pressure molding, a fine primary crystal is crystallized in the alloy liquid, and the temperature of each part of the alloy placed in the holding container is at least as low as possible by induction heating. By the time of molding, the temperature was adjusted so as to fall within a target molding temperature range showing a predetermined liquid phase ratio, and the alloy was taken out from the holding container, supplied to a molding die, and subjected to pressure molding.

[0012] In the second invention, the induction heating in the first invention may be such that the representative temperature of the alloy whose temperature is lowered in the holding container is from immediately after pouring to a stage at which the temperature does not drop by 10 ° C. or more from the target forming temperature. A predetermined amount of current is passed for a predetermined time, and the temperature of each part of the alloy in the holding container is lowered by -5 from the target forming temperature.
The heating was adjusted so as to be within the temperature range of ° C to + 5 ° C. Further, in the third invention, after the temperature of each part of the alloy in the holding container is adjusted to a target forming temperature range within a predetermined time by induction heating, the frequency is equal to or higher than the frequency used in the induction heating. The alloy was kept at a temperature just before the forming step by induction heating at a high frequency.
Further, in the fourth invention, at least the upper part of the holding container,
Either the lower part was kept warm, or it was heated to a higher temperature than the central part of the holding container, or the upper and lower parts of the holding container were made thinner than the central part of the holding container.

In the fifth invention, the method of cooling the alloy in the holding container is such that at least either air or water is injected from outside the holding container toward the holding container. Further, in the sixth invention, the outside of the holding container is
At least one of air and water at a predetermined temperature can be independently injected from a plurality of different height positions while arbitrarily changing injection conditions and injection timing. In the seventh invention, the liquid phase ratio of the alloy supplied to the molding die is 1.0% or more and less than 75%.

In the eighth invention, as a method of generating crystal nuclei, an alloy poured and stored in a holding vessel using a molten metal having a superheat degree of less than 50 ° C. with respect to a liquidus temperature is used.
The vibrating rod is vibrated by vibrating the vibrating rod while directly contacting the vibrating rod during pouring, or the vibrating rod is vibrated while pouring the alloy into the holding container. Vibration was applied to the holding container. Further, in the ninth invention,
As a method for generating crystal nuclei, B having a superheat degree of less than 50 ° C. with respect to the liquidus temperature is 0.001% to 0.01%.
%, And an aluminum alloy melt containing 0.005% to 0.3% of Ti was poured into the holding container. And the tenth
In the invention of the present invention, as a method for generating crystal nuclei, Sr, whose superheat degree is kept below 50 ° C. with respect to the liquidus temperature, is 0.005
% To 0.1%, or 0.01% to 1.5% of Si.
% And Sr from 0.005 to 0.1%, or C
The molten magnesium alloy containing 0.05% to 0.30% of a was poured into the holding container.

[0015]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, the thermal conductivity is 1 kca.
An alloy in a liquid state having a crystal nucleus or higher having a crystal nucleus poured into a holding container having a temperature of 1 / mh ° C. or higher, or an alloy having a crystal nucleus and having a solid-liquid coexistence in a temperature lower than the liquidus temperature and higher than a molding temperature Is cooled at an average cooling rate of 0.01 ° C./s to 3.0 ° C./s and held until immediately before pressure forming, whereby fine primary crystals are crystallized in the alloy liquid and the holding is performed. The temperature of each part of the alloy placed in the container is adjusted by induction heating so that it falls within a target forming temperature range showing a predetermined liquidus ratio at the latest by the time of forming, and the alloy is taken out from the holding container and formed. Since it is supplied to the metal mold and subjected to pressure molding, the temperature of the alloy before the molding step is ideally controlled, so that an excellent compact having a homogeneous structure including a spheroidized primary crystal can be obtained. .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 12 relate to an embodiment of the present invention. FIG. 1 is a process explanatory view showing a method for forming a semi-molten metal of a hypoeutectic aluminum alloy having a composition higher than the maximum solid solubility limit, and FIG. FIG. 3 is a process explanatory view showing a method for forming a semi-molten metal of a magnesium alloy or an aluminum alloy having an internal composition, FIG. 3 is a process explanatory diagram from the generation of a spherical primary crystal to forming, and FIG. 4 is a metal structure of each process shown in FIG. 5, FIG. 5 is an equilibrium diagram of a typical aluminum alloy, Al-Si alloy, and FIG. 6 is a typical magnesium alloy, Mg-Al
FIG. 7 is a micrograph of a micrograph showing the metal structure of the molded article of the present invention, FIG. 8 is a micrograph of a micrograph showing the metal structure of the molded article of the comparative example, and FIG. FIG. 10 is a graph for explaining the correlation between the temperature distribution of the AC4CH alloy in the container and the cooling rate, FIG. 10 is a graph showing the influence of high frequency induction heating on the temperature distribution of the AC4CH alloy in the holding container, and FIG. 11 is AC4CH in the holding container. FIG. 12 is a graph showing the degree of influence of high-frequency induction heating on the temperature distribution of the alloy, and FIG. 12 is an explanatory diagram showing the degree of influence of high-frequency induction heating and holding on the homogenization of the components of the semi-molten metal after reaching the forming temperature.

In the present invention, as shown in FIGS. 1, 2, 3, 5 and 6, first, the degree of superheat with respect to the liquidus temperature is higher than the maximum solid solubility limit maintained at less than 50 ° C. While pouring the molten hypoeutectic aluminum alloy or magnesium alloy or aluminum alloy with the composition within the maximum solid solubility limit into the holding vessel, the vibrating rod is immersed in the alloy in the holding vessel and brought into direct contact with the alloy. The vibrating rod is vibrated while vibrating the alloy, and immediately after pouring is completed, the vibrating rod is pulled up, thereby separating from the alloy.

In this manner, a liquid-state alloy having crystal nuclei at a temperature higher than the liquidus temperature or a solid-liquid coexistence state having crystal nuclei at a temperature lower than the liquidus temperature and higher than the forming temperature is obtained. The alloy in the holding container up to the molding temperature shown,
For example, air at room temperature is injected into the container from the outside of the holding container to cool the container at an average cooling rate of 0.01 to 3.0 ° C./s and hold the container until immediately before pressure molding, whereby fine primary crystals are obtained. Crystallized in the alloy liquid, so that the temperature of each part of the alloy contained in the holding container is within a target forming temperature range showing a predetermined liquidus ratio at the latest by the time of forming by induction heating. The temperature was adjusted, the alloy was taken out of the holding container, supplied to a molding die, and subjected to pressure molding.

Here, the "predetermined liquid phase ratio" means a liquid phase ratio suitable for pressure molding. In high pressure casting such as die casting and squeeze casting, the liquid phase ratio is less than 75%, preferably 40% to 65%. If it is less than 40%, it is not easy to take it out of the holding container 30, and the formability of the taken out material is inferior.

On the other hand, if it exceeds 75%, the material is soft and difficult to handle, and the surrounding air is entrained or molded at the time of insertion into the sleeve for injecting the molten metal in the die of the die casting machine. There is a problem that the metal structure of the casting has segregation and it is difficult to obtain a uniform structure. For this reason, 75% or less, preferably 6%
5% or less. 1.0% to 70% by extrusion or forging
%, Preferably 10% to 65%. If it exceeds 70%, the tissue may be uneven. For this reason, 7
0% or less, preferably 65% or less. Also, 1.0
%, The deformation resistance is high, so it is set to 1.0% or more.
When an extrusion method or a forging method is performed using an alloy having a liquid phase ratio of less than 40%, the alloy is taken out of the holding container at a liquid phase ratio of 40% or more, and then the liquid phase ratio is reduced to less than 40%.

In the present invention, the term "holding container" refers to a metal container or a non-metal container (including a ceramic container), a metal container coated or coated with a metal material on its surface, or a non-metal material. Is a composite metal container. Applying a non-metallic material to the surface of a metal container is effective in preventing metal from adhering. As a means for heating the holding container, there is a method of heating the inside or the outside of the holding container with a heater, but a high-frequency induction device is also applicable. The “representative temperature” in the present invention indicates the central temperature of the alloy placed in the holding container. More specifically, at the center in the height direction of the alloy in the holding container, and
It means the temperature at the radial center position. However, at the time of actual operation, it is difficult to measure the temperatures at both center positions, so at the time of actual operation, a predetermined depth from the surface of the semi-molten metal (for example,
Measure the temperature at 1 cm). Then, from this temperature, the representative temperature is estimated by using the relationship between the representative temperature and the temperature of each part which has been investigated in advance.

In the present invention, the "crystal nucleus generation method" includes a method of generating crystal nuclei using a vibration jig during pouring into a container, and a method of using a low-temperature molten metal containing a refining agent. As a method of generating crystal nuclei, a known technique, for example, Seed Pou using a crystal release method has been proposed.
A ring method (flowing a molten metal on a water-cooled inclined cooling plate) or a method of mixing two liquid phases having different melting points may be employed. According to the present invention, `` vibrating the vibrating rod while vibrating the vibrating rod while immersing the vibrating rod during pouring and directly contacting the alloy that is poured and stored in the holding container, '' It does not mean that the molten metal is poured into the vibrating rod placed in the holding container. In the present invention, the liquid alloy that has accumulated after being placed in the holding container is vibrated by a vibrating rod immersed in the alloy (the vibrating rod is separated from the alloy at the same time as the pouring is completed). ).

The "vibration" of the present invention is not limited to the type of vibration generator and the vibration conditions (frequency and amplitude), but may be a commercially available pneumatic vibrator or electric vibrator. As the vibration conditions to be performed, for example, the frequency is 10 Hz to 50 kHz, preferably 50 Hz to 1 kHz.
z, half amplitude is 1 mm to 0.1 μm, preferably 500 μm
m to 10 μm are desirable.

In order to generate crystal nuclei and obtain a fine spherical structure, Ti and B are added to an aluminum alloy, and Sr, Si and Ca are added to a magnesium alloy. If Ti is less than 0.005%, the effect is small, and if it exceeds 0.30%, a coarse Ti compound is generated and ductility is reduced, so that Ti is 0.005% to 0.30%.
%. B promotes miniaturization in combination with Ti,
If it is less than 0.001%, the miniaturization effect is small, and
Even if added in excess of 1%, no further effect can be expected, so B is made 0.001% to 0.01%. Sr is 0.
If it is less than 005%, the effect of miniaturization is small, and if it exceeds 0.1%, no further effect can be expected, so the content is made 0.005% to 0.1%. 0.005% to 0.1
%, More complex crystal grains can be obtained than by adding Sr alone. If Ca is less than 0.05%, the refining effect is small, and even if added over 0.30%, no further effect can be expected, so Ca is set to 0.05% to 0.30%.

Specifically, the operation proceeds according to the following procedure. In step [1] of FIGS. 3 and 4, the alloy M ₁ , which is a complete liquid, placed in the ladle 10 was poured into a holding container (ceramic container or ceramic coated metal container) 30 in step [2]. The vibrating rod 20 is vibrated by placing the vibrating rod 20 in the alloy, immersing the alloy in the alloy, and bringing the alloy into direct contact with the vibrating rod 20 to vibrate the alloy. Vibration is applied via 40, and immediately after the pouring is completed, the vibrating rod 20 is immediately pulled up, so that crystal nuclei are generated in an alloy in a liquid state and a solid-liquid coexisting state near a liquidus line.

Next, in the step [3], the alloy is added to 0.1.
While cooling the alloy at an average cooling rate of 01 ° C./s to 3.0 ° C./s, the alloy is held in the holding container 30 until immediately before pressure forming, and fine primary crystals are induced while crystallizing in the alloy liquid. By heating (by energizing the heating coil 80 around the holding container 30),
The temperature of each part of the alloy in the container is adjusted so as to fall within a target forming temperature range showing a predetermined liquidus ratio from immediately after pouring to at the latest at the time of forming. In cooling, air (or water) 9 is applied from outside the holding container to the holding container.
Inject 0. If necessary, the upper and lower portions are kept in a semi-molten state in a holding vessel 30 kept or heated with a heat insulating material, and fine spherical (non-dendritic) primary crystals are generated from the introduced crystal nuclei. The alloy M ₂ with a predetermined liquid phase ratio obtained in this way, for example, the step [3] The holding container 30 is inverted as -d, given liquid phase ratio in the injection sleeve 50 of the die-casting machine After inserting the alloy, a molded product is obtained by pressure molding in the mold cavity 60a of the die casting machine.

FIG. 9 is a graph for explaining the correlation between the temperature distribution of the AC4CH alloy in the holding container and the cooling rate, and shows the relationship between the cooling rate (615 ° C. to 585 ° C.) and the temperature distribution of the AC4CH alloy in the holding container 30. It shows the degree of influence, and it can be seen that the temperature distribution increases as the cooling rate increases. In FIG. 9A, FIG.
The case of 3 ° C./s was shown, in which air was injected from the outside of the holding container to cool the container. FIG. 9B shows a case where the cooling rate is 0.2 ° C./s, and a case where the upper and lower portions of the container are kept warm with a heat insulating material and then cooled in the atmosphere.

FIG. 10 is a graph showing the effect of high frequency induction heating on the temperature distribution of the AC4CH alloy in the holding container, and shows the effect of high frequency induction heating on the temperature distribution of the AC4CH alloy in the holding container 30. ing. The representative temperature (the center temperature of the alloy in the holding container) is +3 of the target forming temperature.
After the temperature reaches ° C, the air injection is stopped, and the target temperature is reached, and the high-frequency induction is started.

FIG. 11 is a graph showing the influence of high-frequency induction heating on the temperature distribution of the AC4CH alloy in the holding container, and shows the effect of high-frequency induction on the temperature distribution of the AC4CH alloy in the holding container 30. After the representative temperature (the center temperature of the alloy in the holding container) reaches a temperature (target temperature −11 ° C.) lower by 11 ° C. than the target forming temperature, the air injection is stopped and high-frequency induction heating is started. If the high-frequency induction device starts operating before the target molding temperature is lowered too much, the temperature of each part of the alloy in the holding container 30 can be maintained at the target molding temperature with a low output in a short time. When the high-frequency induction device operates at a temperature of 10 ° C. or more, it is not easy to equalize the temperature of each part in the container, and high output and long-time induction heating are required. Therefore, in the induction heating, a predetermined amount of current is caused to flow once or more for a predetermined time at a stage where the representative temperature of the alloy whose temperature drops in the holding container 30 does not drop by 10 ° C. or more from the target forming temperature.

FIG. 12 is an explanatory diagram showing the influence of high-frequency induction heating and holding on the homogenization of the semi-molten metal after reaching the forming temperature. FIG. 12 is a vertical sectional view showing the state of the alloy in the holding container 30. FIG.
(A) is the state when the molding temperature is reached, FIG. 12 (b)
Is induction-heated at a frequency of 8 KHz with a high-frequency induction device, and 20
FIG. 12 (c) shows a state in which induction heating is performed at a frequency of 40 KHz by a high-frequency induction device, and the state is maintained for 20 minutes. The frequency of the high-frequency induction device before adjustment to the molding temperature is 8
KHz. When reaching the molding temperature (FIG. 12)
Although this does not occur in the state (a), if the holding time is long, as shown in FIG. 12B, of the semi-molten metal in which the liquid phase and the solid phase are uniformly mixed at the outer peripheral portion of the upper portion, A phenomenon in which the liquid phase is unevenly distributed in the upper outer peripheral portion is observed (the black portion in the figure is the liquid phase).

This is considered to be caused by the fact that the metal in the holding vessel 30 rises during the high-frequency induction, and the liquid phase in the semi-molten metal floats on the upper part of the vessel mainly due to the stirring force. However, to reduce the stirring power,
After the temperature of the semi-molten metal in the holding container is adjusted to the molding temperature, the degree can be reduced by performing induction heating at a higher frequency. For this reason, after the temperature of each part of the alloy in the container is adjusted to a target forming temperature range within a predetermined time by induction heating, induction heating at a frequency equal to or higher than the frequency used in the induction heating is performed. The temperature of the alloy is maintained until immediately before the forming step.

The differences between the examples of the present invention shown in FIGS. 1, 2, 3, 4 and 11 and the conventional thixocasting and rheocasting methods will be described. The dendrite-like primary crystals crystallized in the temperature range are not forcibly crushed and spheroidized by mechanical stirring or electromagnetic stirring, and the crystal starts from the crystal nuclei introduced into the liquid as the temperature decreases in the semi-melting temperature range. Many primary crystals that evolve and grow are continuously spheroidized by the amount of heat of the alloy itself (it may be heated and held from the outside if necessary) and uniform by low-frequency high-frequency induction heating. This method is characterized by a simple structure and a uniform temperature distribution, and is a very simple and economical method because the step of semi-solidification by reheating the billet in the thixocasting method is omitted.

The nucleation conditions, spheroidization conditions, molding conditions, and the like set in each of the above-described steps, ie, the steps of pouring into the holding vessel 30 shown in FIG. The reasons for limiting the numerical values shown in the present invention will be described below. If the temperature of the molten metal poured into the holding container 30 is higher than the liquidus temperature by 50 ° C. or more,
(1) The generation of crystal nuclei is small, and (2) Since the temperature of the alloy when poured into the container is higher than the liquidus line, the proportion of remaining crystal nuclei is small and the size of primary crystals is small. Large, irregular dendrites are generated.

[0034] For this reason, by setting the pouring temperature to a superheat degree of less than 50 ° C for the liquidus line and to a superheat degree of less than 30 ° C for the liquidus temperature, a finer primary crystal size can be obtained. .

When the upper part and the lower part of the container are not heated or kept warm when the alloy M ₁ poured into the holding container 30 is cooled to a liquid phase ratio suitable for molding, the upper part and / or the lower part of the container are not heated. or dendritic primary crystals are generated in the skin part of the alloy M ₁ of the lower, since the solidified layer is also uneven temperature distribution of the metal growth holding vessel 30, the holding container 30 be heated by high frequency induction When the alloy is inverted and taken out from the container, the alloy having a predetermined liquid phase ratio cannot be discharged from the holding container 30, a solidified layer remains inside the holding container 30, making continuous molding difficult, and the temperature distribution is completely improved. Or not. For this reason, if the holding time until the molding temperature after pouring is short, the upper part of the holding container and / or
Alternatively, the lower part of the holding container is heated from the center part of the holding container, or the temperature is kept, and the upper part and the lower part of the holding container 30 are heated before the pouring as well as the cooling process after pouring as necessary. In addition, since the formation of a solidified layer is suppressed by reducing the thickness of the holding container 30, the discharge of the alloy from the holding container 30 is performed by making the upper and lower thicknesses of the holding container smaller than the thickness of the center portion of the holding container. To facilitate.

The thermal conductivity of the holding container 30 is 1.0 kca
If the material has a temperature of less than 1 / mhr ° C., the cooling time becomes longer and this is industrially inconvenient. Therefore, the thermal conductivity of the holding container 30 is set to 1.0 kcal / mhr ° C. or more. When using the metallic holding container 30, it is preferable to apply a nonmetallic substance (for example, BN, graphite, etc.) to the surface of the holding container 30. The application method may be any of mechanical, chemical, and physical methods. Further, when a gas-permeable container is used as the holding container 30 or when the container is held for a long time, the magnesium alloy and the aluminum alloy are easily oxidized. And so on).
Even when a metal container is used, since the magnesium alloy is easily oxidized, it is desirable to use an inert atmosphere or a CO2 atmosphere. Also, in order to prevent oxidation, Be and Ca can be added to the molten metal in advance for magnesium alloys and Be for aluminum alloys. In addition, the shape of the container 30 is not limited to a cylindrical shape,
A shape suitable for the subsequent molding method may be adopted.

The average cooling rate in the holding container 30 is 3.
If it is faster than 0 ° C./s, it is not easy to keep the temperature within a target molding temperature range showing a predetermined liquidus ratio even by using induction heating, and it is difficult to form a spherical primary crystal. On the other hand, if the average cooling rate is less than 0.01 ° C./s, the cooling time is long, which is inconvenient for industrial production. For this reason,
The average cooling rate is 0.01 ° C./s to 3.0 ° C./s, more preferably 0.05 ° C./s to 1 ° C./s.

When the cooling of the holding container 30 is actively performed, at least one of air and water is sprayed from the outside of the holding container 30 toward the holding container 30, and if necessary, the outside of the holding container 30 is provided at two or more places. The injection conditions and the injection timing are changed arbitrarily independently from the positions at different heights. The substance to be injected, the amount, speed, position, and injection timing of the injection vary depending on the alloy in the holding container 30, the material and thickness of the holding container 30, and the like.

If the temperature of the alloy inside the holding container before forming exceeds the target forming temperature by -5 ° C. to + 5 ° C., a molded product having a homogeneous structure cannot be obtained after casting. On the other hand, the temperature of the alloy inside the holding container is adjusted to -5 ° C to + 5 ° C by induction heating.

When the vibrating rod 20 is used to give crystal nuclei to the alloy to be poured, the vibrating rod 20 is used continuously, and cooling is performed from inside or outside to generate a large number of crystals. It is preferable that a non-metallic substance be applied to the surface of the vibrating rod 20. If a rod that can be cooled from the inside without vibration is used, even if a non-metallic substance is applied, a large amount of solidified layer will form on the rod surface when the rod is pulled up from the poured alloy. Adhesion or dendrites are often found in the alloy in the holding vessel. Therefore, when a rod that can be cooled is brought into contact with the molten metal, the rod is vibrated.

If the vibrating rod 20 is used, fine primary crystals can be crystallized in the alloy in the holding container. But,
Dendrites may be generated at the portion in contact with the holding container 30. For this reason, it is preferable to apply vibration to the holding container 30 during pouring.

[0042]

[Table 1]

[0043]

[Table 2]

Table 1 shows the forming conditions of the semi-molten metal before forming, and Table 2 shows the temperature distribution of the metal in the container and the quality of the formed material before forming. The molding was performed by inserting a semi-molten metal into the sleeve 50 and then using a squeeze casting machine as shown in FIG. The molding conditions were as follows: pressure 950 kgf / cm ² , injection speed 0.5 m / s, casting weight (including biscuit)
And the mold temperature was 230 ° C. However, in Tables 1 and 2, No. Numeral 13 indicates the molding conditions and the quality of the molded material when molded using an extruder. The extrusion was performed by inserting a semi-molten metal into a container. The molding conditions are as follows. (1) Extruder specification: 800 t; (2) Extrusion speed (product speed): 80 m / min. (3) Extrusion ratio; 20 (4) Extruded billet diameter: 75 mm

In Comparative Example 14, the representative temperature of the alloy whose temperature drops in the holding container 30 is 10 ° C. with respect to the target forming temperature.
Since the induction heating was performed with the temperature lowered as described above, the temperature could not be kept within the range of -5 ° C to + 5 ° C with respect to the target molding temperature range, and a molded body having a uniform structure could not be obtained.
In Comparative Example 15, although the cooling rate was slow, there was no significant problem with respect to the temperature distribution, but the primary crystal size was 200 μm.
m, which is inconvenient for continuous production. In Comparative Example 16, the holding time by induction heating after the temperature of each part of the alloy in the holding container was adjusted to the target forming temperature range was long, and the frequency was not changed. There was much liquid phase in the part. In Comparative Example 17,
Since the cooling rate is too high, even if induction heating is performed, the temperature cannot fall within the range of −5 ° C. to + 5 ° C. with respect to the target molding temperature range, and a molded body having a uniform structure cannot be obtained. Not only that, a solidified layer is formed inside the container,
It was difficult to remove the semi-molten metal from the container. In Comparative Example 18, since the pouring temperature was high, the crystal nuclei did not remain because the temperature of the molten metal after pouring into the container was high, and a large number of amorphous dendrites were generated. In Comparative Example 19, since the heat retention of the holding container was insufficient, the metal on the upper portion of the holding container was quickly cooled and it was not easy to take out the metal from the holding container (see FIG. 8).

On the other hand, in the present invention 1 to the present invention 13, as shown in FIG. 7, no amorphous dendrites were observed, and a compact having a uniform structure having fine spherical primary crystals was obtained. .

[0047]

As is apparent from the above description,
In the method for forming a semi-molten metal according to the present invention, a compact having a fine and spherical structure can be obtained simply and easily at low cost without using the conventional mechanical stirring method or electromagnetic stirring method.

[Brief description of the drawings]

FIG. 1 is a process explanatory view showing a method for forming a semi-molten metal of a hypoeutectic aluminum alloy having a composition not less than the maximum solid solubility according to the present invention.

FIG. 2 is a process explanatory view showing a method for forming a semi-molten metal of a magnesium alloy or an aluminum alloy having a composition within a maximum solid solubility limit according to the present invention.

FIG. 3 is an explanatory diagram of steps from generation of a spherical primary crystal to molding according to the present invention.

FIG. 4 is a schematic diagram of a metal structure in each step shown in FIG.

FIG. 5 shows a typical aluminum alloy according to the present invention, Al-
FIG. 3 is an equilibrium diagram of a Si-based alloy.

FIG. 6 is a diagram showing a typical magnet alloy according to the present invention, Mg-
FIG. 3 is an equilibrium diagram of an Al-based alloy.

FIG. 7 is a microphotograph showing a metallographic structure of a molded article (AC4CH alloy) of an example of the present invention.

FIG. 8 is a micrograph of a micrograph showing a metal structure of a molded product (AC4CH alloy) of a comparative example.

FIG. 9 shows AC4CH in a holding container according to an embodiment of the present invention.
5 is a graph illustrating a correlation between a temperature distribution of an alloy and a cooling rate.

FIG. 10 shows AC4C in a holding container according to an embodiment of the present invention.
It is a graph which shows the degree of influence of high frequency induction heating on the temperature distribution of H alloy.

FIG. 11 shows AC4C in a holding container according to an embodiment of the present invention.
It is a graph which shows the degree of influence of high frequency induction heating on the temperature distribution of H alloy.

FIG. 12 is an explanatory diagram showing the degree of influence of high-frequency induction heating and holding on homogenization of the components of the semi-molten metal after reaching the forming temperature according to the example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Ladle 20 Vibration stick 30 Holding container (metal container or non-metal container) 40 Vibration device 50 Injection sleeve 60 Mold 60a Mold cavity 70 Heat insulation material 80 Coil 90 Air (or water) M Molten metal T Holding time t Container Inner metal temperature

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasunori Harada 1980 No. Yama, Kogushi-ji, Obe-shi, Ube-shi, Yamaguchi Ube Industries, Ltd. Machinery & Engineering Division

Claims (10)

[Claims] 1. An alloy in a liquid state having a crystal nucleus or higher having a crystal nucleus poured into a holding container having a thermal conductivity of 1 kcal / mh ° C. or higher, or a liquid alloy having a crystal nucleus having a temperature lower than the liquidus temperature. An alloy in a solid-liquid coexisting state at a temperature of 0.01 ° C /
By cooling at an average cooling rate of s to 3.0 ° C./s and holding until just before pressure molding, fine primary crystals are crystallized in the alloy liquid, and the alloy put in the holding container is cooled. The temperature of each part is adjusted by induction heating so as to fall within a target molding temperature range showing a predetermined liquid phase ratio at the latest by molding, and the alloy is taken out from the holding container and supplied to a molding die. A method for forming a semi-molten metal, which is performed by pressure molding. 2. The induction heating is performed in such a manner that the representative temperature of the alloy whose temperature falls in the holding container is 10 ° C. with respect to the target forming temperature immediately after pouring.
By the time the temperature does not decrease, a predetermined amount of current is passed for a predetermined time, and the heating is adjusted so that the temperature of each part of the alloy in the holding container falls within a temperature range of −5 ° C. to + 5 ° C. with respect to the target forming temperature. The method for forming a semi-molten metal according to claim 1, wherein 3. After the temperature of each part of the alloy in the holding container is adjusted to a target forming temperature range within a predetermined time by induction heating, a frequency equal to or higher than the frequency used in the induction heating is used. 3. The method for forming a semi-molten metal according to claim 1, wherein the temperature of the alloy is maintained until just before the forming step by induction heating. 4. Heating at least one of the upper and lower portions of the holding container, heating the holding container to a higher temperature than the central portion of the holding container, or reducing the thickness of the upper and lower portions of the holding container 4. The method for forming a semi-molten metal according to claim 1, wherein the thickness is smaller than a central portion of the metal. 5. The method for cooling an alloy in a holding container according to claim 1, wherein at least one of air and water is injected from outside of the holding container toward the holding container. Method for forming semi-molten metal. 6. Injecting air or water of at least a predetermined temperature independently from two or more different height positions outside the holding container independently from two or more different height positions by arbitrarily changing injection conditions and injection timing. The method for forming a semi-molten metal according to claim 5, which is made possible. 7. The method for forming a semi-molten metal according to claim 1, wherein the liquid phase ratio of the alloy supplied to the forming die is 1.0% or more and less than 75%. 8. A method of generating crystal nuclei, comprising: using a molten metal having a degree of superheat of less than 50 ° C. with respect to a liquidus temperature, to an alloy poured and stored in a holding vessel, and a vibrating rod during pouring. The vibrating rod is vibrated by vibrating the vibrating rod while directly contacting the vibrating rod, or the vibrating rod is vibrated while the vibrating rod is vibrated while the alloy is being poured into the holding vessel. The method for forming a semi-molten metal according to claim 1, wherein the metal is provided. 9. As a method for generating crystal nuclei, B having a superheat degree of less than 50 ° C. with respect to a liquidus temperature is 0.001%.
The method for forming a semi-molten metal according to claim 1, wherein a molten aluminum alloy containing 0.005% to 0.01% and 0.005% to 0.3% of Ti is poured into the holding container. 10. A method for producing crystal nuclei, wherein Sr, whose superheat degree is kept below 50 ° C. with respect to the liquidus temperature, is 0.0%.
Containing 0.05% to 0.1%, or 0.01% to Si
The magnesium alloy melt containing 1.5% and 0.005 to 0.1% of Sr or 0.05% to 0.30% of Ca is poured into the holding container. Forming method of semi-solid metal.