JP2000343200A - Method and machine for casting semi-solid material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a casting method of a semi-solid metallic material used for high quality of a mold casting product such as die cast. SOLUTION: This method comprises a step that a metallic material is made into a molten metal in a first holding furnace 2 and held above high liquid phase temperature in a range of 10-50 deg.C from the liquid phase line, a step that the molten metal is rapidly cooled in a range above the solid phase line temperature so as to generate a primary equiaxed crystal, a step that the molten metal including the equiaxed crystal is held below the liquid phase line temperature but above the solid phase line temperature in a second holding furnace 13 into a given solid phase rate, and a step that the molten metal portion with a given solid phase rate is intermittently pulled out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semi-solid material casting method and a casting machine used for improving the quality of a die casting such as a die cast. Here, semi-solid refers to a state of coexistence of solid and liquid, that is, a state between liquidus temperature and solidus temperature.

[0002]

2. Description of the Related Art Die casting, particularly die casting, is a casting or processing method in which an aluminum alloy or the like is cast into a mold and solidified, and a casting having a complicated shape can be easily formed. , The products have been applied in various fields.
However, since the metal structure of the cast product is a cast structure mainly composed of dendrite, and it is cast at a considerably high casting speed from a temperature usually higher than the liquidus temperature by 100 ° C. or more,
There is an unavoidable occurrence of cavities due to entrainment of air and solidification shrinkage, and there is a quality defect that mechanical properties, particularly elongation and fatigue strength, are lower than those of forged materials.

[0003] Therefore, it is known that mechanical properties, especially elongation, are improved if dendrite growth is prevented in the solidified structure of a cast product and can be made equiaxed or granular. Therefore, in a metal casting method or a molding method in which a molten metal is supplied to a mold and solidified, so-called semi-solid casting in which the molten metal is supplied in a state containing a solid phase component which is a granular crystal and a high pressure is applied thereto is desirable.

In this casting method, the crystal grains are refined by the quenching effect of the mold and unfilled by low-speed / low-temperature material supply.
It has recently become known that prevention of shrinkage cavities not only improves the strength and elongation of products but also greatly improves fatigue strength.

[0005] However, in the conventional semi-solid casting, the molten material is solidified with electromagnetic stirring to keep the billet at a temperature in the solid-liquid coexistence region, and the billet is supplied to a molding machine to produce a product. Due to its high cost, the advantages of semi-solid processing were clear, but its spread was slow.

Recently, a billet which has been subjected to a process of stirring a molten metal at the time of solidification and granulating pro-eutectoid crystals (hereinafter referred to as a semi-solid billet) is reheated to form a solid-liquid coexistence state. It has been reported that the method has been put to practical use and that a significant improvement in the above quality has been obtained.
There are drawbacks that the manufacturing cost is high and that it can be applied only to special applications.

[0007] As described above, the semi-solid machining currently performed requires a process of making a semi-solid billet independent of the actual semi-solid machining process, and usually involves continuous casting after electromagnetic stirring. Expensive, therefore billet price is usually 50% compared to bullion
Or higher.

Since this is gradually heated by a heating device and supplied to the molding machine when it becomes a solid-liquid coexistence state, this heating device also requires space, requires equipment costs, and has a material supplied to the molding machine. Because almost 50% of products are not made into products such as hot springs and runners. The high price of the above-mentioned material cost double raises the price of the product, and there is a disadvantage that the part which does not become a product cannot be recycled in its own process.

On the other hand, a method of rapidly cooling a molten metal by using an inclined cooling plate has been known in principle for a long time, but has not been put to practical use. This seems to be because the experiments so far have been performed at a relatively small flow rate, and it was not practical in terms of productivity for practical use.

A method has also been proposed in which electromagnetic stirring and low-temperature holding are performed at the stage of supplying a molten metal to a die casting machine.
The extent of its practical use is not known. The drawback of this method is that electromagnetic stirring, cooling and molten metal holding are performed almost simultaneously, so it seems that there may be a problem with the stability of the process,
There is no report on the practical application of this method, so it cannot be conjectured.

[0011]

SUMMARY OF THE INVENTION The present invention solves these drawbacks, and does not use a semi-solid billet, does not add a complicated process such as electromagnetic stirring before a molding process such as die casting, and reduces the throughput. It is intended to provide a material supply process to a semi-solid molding process that is realistic, has high productivity, and has low equipment costs.

[0012]

A first aspect of the present invention is a method for casting a semi-solid metal material, comprising the following steps. (A) a step of forming a metal material into a molten metal in a first holding furnace and maintaining the molten material at a liquidus temperature higher than the liquidus temperature in the range of 10 to 50 ° C .; (C) maintaining the melt containing the equiaxed crystal at a temperature below the liquidus temperature and above the solidus temperature in a second holding furnace, A phase ratio;
(D) a step of intermittently taking out the portion of the molten metal having the predetermined solid phase ratio.

A second aspect of the present invention is the method of casting a semi-solid material according to claim 1, wherein said semi-solid material is a die-cast material.

A third aspect of the present invention is a metal semi-solid casting machine comprising the following members. (A) a first holding furnace having a heating means for holding the metal material at a liquidus temperature higher than the liquidus temperature in the range of 10 to 50 ° C. or higher, and a pouring means for discharging the molten metal; Quenching means for quenching the molten metal discharged by the pouring means to generate primary crystal equiaxed crystals; and (c) maintaining the molten metal containing primary crystal equiaxed crystals at a liquidus temperature or lower and a solidus temperature or higher. A second holding furnace having a predetermined solid phase ratio, and a means for intermittently removing a portion of the molten metal having the predetermined solid phase ratio.

In a fourth aspect of the present invention, as the quenching means, a plurality of metal plates are arranged in parallel at a narrow interval at the entrance of the molten metal, at a middle bulge in the middle, and again at a small interval at the exit. And a quenching means arranged so that a pool is formed between the plurality of metal plates, the flow of the molten metal is not interrupted, and the quenching means is arranged to flow down in a rectified state. It is a semi-solid casting machine.

According to a fifth aspect of the present invention, the quenching means comprises:
(A) a horizontally arranged triangular prism dispersing means for dispersing the molten metal flowing down from the first holding furnace; and (b) a multilayer cooling plate for receiving the molten metal dispersed by the dispersing means, wherein a plurality of plates are provided. When the molten metal is arranged side by side at a wide interval at the inlet, and narrower as it goes downward near the outlet of the flow path, and the molten metal is poured between the cooling plates or along the cooling plate,
A metal having a multilayer cooling plate in which the molten metal forms a pool in at least a part of the gap in the vicinity of the cooling means outlet, and in which the flow of the molten metal is not interrupted and flows down by rectification. Is a semi-solid material casting machine.

In a sixth aspect of the present invention, the quenching means comprises:
(A) a triangular pyramid-shaped dispersing means for dispersing the molten metal flowing down from the first holding furnace; and (b) a hot-water pool for storing the molten metal dispersed by the dispersing means at an upper portion, followed by concentric circles. A plurality of slits, the diameter of which is large in the upper part, and is gradually reduced toward the lower outlet, and when the molten metal is poured along the slits, at least one slit is provided near the outlet. A metal semi-solid casting machine characterized by comprising a block in which a molten metal is formed in a gap between portions, a flow of the molten metal is not interrupted, and a block body flows down by rectification.

A seventh aspect of the present invention is a metal semi-solid casting machine, wherein said quenching means is provided with fins for temperature adjustment.

According to an eighth aspect of the present invention, the quenching means comprises a mold release agent applied to a surface in contact with the molten metal. It is a solid material casting machine.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic structure of the present invention is as follows: (1) The target metal is a low-temperature molten metal as close to the liquidus line as possible,
(2) Rapid cooling in the temperature range below the liquidus temperature and above the solidus temperature to generate a large number of fine granular primary crystals, and (3) further slow cooling in a state of a small temperature gradient to grow granular crystals. An object of the present invention is to provide a process for obtaining a semi-solid material in a solid-liquid coexistence range. Forming a final product from the obtained semi-solid material, that is, slag, is a mold forming method, for example, a die casting method.

An embodiment will be described with reference to FIGS. As shown in the figure, the target metal is melted in a first holding furnace 2, for example, a high-frequency furnace, and the temperature of the molten metal 4 is precisely controlled so as to be kept as close to the liquidus temperature as possible. Next, the molten metal is discharged from the first holding furnace, for example, by operating the stopper 2 ', and rapidly cooled by the rapid cooling means 7, 8, 9 to generate a large number of primary crystal nuclei.

Next, this molten metal is gradually cooled in a second holding furnace 13, for example, a high-frequency furnace, to grow primary crystal nuclei, thereby obtaining solid-liquid coexistence states 14 and 16 having many granular crystals. This is guided to a piston chamber at the lower part of the furnace, and the piston 18 is intermittently driven to be discharged as a semi-solid material 22, and the slag 26 is discharged.
Get. This material is supplied to a molding process, for example, a die molding machine such as a die cast. Examples of the forming method include a die casting method and a molten metal forging method (squeeze casting method).

An important factor in this process is the rapid cooling means. The quenching means shown in FIG. 1 is shown in detail in FIG. This means 7, for example, a plurality of copper alloy metal plates,
At the entrance of the molten metal, it is arranged in parallel at a narrow interval, in the middle it is arranged in a middle bulge, at the exit it is arranged again with a small interval and parallel, and it is arranged so that a pool can be formed between the plurality of metal plates, This is a quenching means arranged so as to be continuous and to flow down in a rectified state. In this specification, the term “rectification” basically refers to a laminar flow, but refers to a flow state including a partially turbulent flow state. The metal plate includes a pool 72 and cooling fins 71. The pool 72 holds the molten metal, and the fins 71 on both sides radiate heat generated by cooling the molten metal.

Examples of specific dimensions are, for example, the height H1 of the copper plate.
Is 120 mm, the overall width L1 is 400 mm, and the middle part is 200 m
m and 100 mm long fins. The length of the fin can be changed as needed. Exit spacing is approx.
1mm, entrance side (upper side) board interval is about 3mm, opposing board interval is also about 3mm, middle board interval is about 5mm at the middle maximum position,
The distance between the facing plates is also about 5 mm. Therefore, the upper end width L2 is 15 mm, and the lower end width L3 is 5 mm. The above dimensions are one example, and can be appropriately changed depending on the amount of the molten metal to be treated.

FIG. 4B shows the details of the cooling means 8 shown in FIG.
Shown in As shown in FIG. 2, the dispensing means 5 disposed below the first holding furnace to disperse the molten metal to be flowed down is a triangular prism made of metal or refractory arranged horizontally. The multilayer cooling plate receiving the dispersed molten metal is composed of an intermediate pool of water 82 and fins 81 at both ends, and is arranged side by side at a wide interval at the inlet and narrower downward near the outlet of the flow path. When the molten metal is poured between the cooling plates or along the cooling plate, the molten metal forms a pool in at least a part of the gap in the vicinity of the cooling means outlet, and the flow of the molten metal is not interrupted, and the flow is straightened. Flow down.

The size of the above-mentioned hot-water dispensing means is, for example, 10 mm per side.
Is an equilateral triangle. An example of the dimensions of the quenching means is, for example, a quenching means in which three iron plates having a thickness of 1 mm are arranged with the upper entrance side gap being about 5 mm and the exit side gap being about 1 mm, and two sets of these are opposed to each other. So the total length L4 is 400mm and the height H2 is 120m
m, the upper end width L5 is 25 mm, and the lower end width is 5 mm.

The quenching means shown in FIG. 3 is shown in detail in FIG. This means is a metal or refractory triangular pyramid-shaped dispersing means 5 'for dispersing the molten metal flowing down from the first holding furnace.
And a block body for rapidly cooling the molten metal dispersed by the triangular pyramid-shaped dispersing means 5 '. This block has a sump 91 at the top, followed by a plurality of concentric slits 92, the diameter of which is large at the top and which decreases for a time toward the outlet below.

When the molten metal is poured along the gap between the slits, the molten metal is accumulated in at least a part of the gap near the outlet, so that the flow of the molten metal is not interrupted and flows down by rectification. It is a means to make it. This means can use graphite, for example, when the metal is an aluminum alloy.

Specific dimensions are, for example, that the length L7 is 100 mm,
The height H3 is 120 mm, and a reservoir part having a diameter of 80 mm and a depth of 10 mm is provided on the upper part, followed by six through slits. The slit is 8 mm wide at the top and 3 mm wide at the bottom exit.

The second holding furnace 13 has a temperature gradient in which the temperature decreases toward the outlet, and the melts 14 and 16 having a predetermined solid phase ratio are guided from the communication hole 17 to the lower piston chamber to be semi-conductive. It becomes the solid material 22 and is discharged and becomes slag. This slag opens the door 24 and discharges intermittently.
The discharging means 18 may be a piston, a screw, or the like. When it is not desirable to contact the outside air or when the solid fraction is relatively low, an electromagnetic pump can be used.

[0031]

Example 1 Using the apparatus shown in FIG. 1, an Al-6% Si alloy was kept at 630 ° C. and 5 ° C. in a first holding furnace, and the flow rate was controlled with a stopper rod to a maximum of 3 L. At a flow rate of 1 / min. The quenching means is a copper plate having a thickness of about 1 mm which is bent two-dimensionally with a slightly changed bending radius so as to face three sheets at intervals. The surface of the copper plate was spray-coated with boron nitride as a release agent.

The quenching means is made of a copper plate and has a height of 120
mm, the width is 200 mm, and fins with a length of 100 mm are provided at both ends. The distance between the exit plates was about 1 mm, the distance between the entrance (upper) sides was about 3 mm, and the distance between the opposite plates was about 3 mm.
The interval between the plates was about 5 mm at the middle maximum position, and the interval between the opposing plates was also about 5 mm.

In the above-mentioned quenching means, the molten metal forms pools having different heights in the lower part of the swelling. The formation of the pool is not necessarily a necessary condition, but the purpose is to make the flow of the molten metal uninterrupted and to have a turbulent flow close to a laminar flow.

The melt that has flowed out contains primary equiaxed crystals, which are grown in a second holding furnace to obtain a desired solid fraction,
For example, the slag 22 is intermittently sent out at 40%. In this figure, the temperature gradient is downward,
The situation where the solid phase ratio increases as going downward due to the difference in hatching in the figure is shown. The means for sending out the semi-solid material 22 is a piston in this figure.

In the figure, the molten metal flows in through the communication hole 17,
Fill inside the cylinder. When the lid 24 is opened in the direction of the arrow (24 ') and the piston 18 is advanced in the direction of the arrow 20, the material 22 in the cylinder is sent out. The delivery amount was adjusted by the piston stroke, and in this example, the stroke time was about 4 kg and the cycle time was 40 seconds. This slag 26 is supplied to a high-pressure die-casting machine, and the maximum pressure is 12 kg / mm.
^The product was solidified under pressure in ² to obtain a product with extremely high fatigue strength.

Embodiment 2 FIG. 2 shows an embodiment in the case of processing a Mg-9% Al alloy. The first holding furnace, the second holding furnace, and the quenching means 8, the splitting means 5, and the molten metal flow in the middle are all arranged in a chamber filled with an inert gas (not shown), and the contact with the air is completely replaced by nitrogen. To prevent the oxidation of the molten metal to the maximum.

As shown in FIG. 2, the flow of the molten metal was appropriately divided by the flow dividing means 5 when the molten metal held at a low temperature and allowed to flow into the first holding furnace was allowed to flow. The three iron plates having a thickness of 1 mm were arranged so that the gap on the upper side was about 5 mm and the gap on the outlet side was about 1 mm, and they were opposed to each other.

The molten metal was uniformly poured into the upper gap of the rapid cooling means 8.
The molten metal forms primary equiaxed crystals in the quenching means,
The slag 22 is grown in a holding furnace, and discharged when the solid phase ratio reaches a desired value. The cooling plate was an iron plate, and was coated with boron nitride having high release properties. The productivity is almost the same as that of the previous embodiment, and the weight per unit time is smaller than that of aluminum by a lighter weight. The resulting product showed the same superiority as the previous example.

Embodiment 3 FIG. 3 shows an example in which a metal plate is used as the quenching means in the above embodiment, but a hexahedral block provided with a porous flow path is used as the quenching means. This block 9 is made of carbon, has a square upper surface, a side L7 of 100 mm, a height H3 of 120 mm, and a water pool having a diameter of 80 mm and a depth of 10 mm at an upper portion thereof.
Six slit-shaped holes are drilled in connection with this. The holes were 8 mm in diameter at the top and 3 mm in diameter at the bottom outlet.

In this embodiment, the material is kept at a low temperature in a first holding furnace which has been treated with an Al-6% Si alloy, and is discharged, and the molten metal flow is radially divided and distributed by a dividing means 5 '. , Is supplied to the six holes of the rapid cooling means. The liquid level in the quenching means is considered as a standard state as shown in the figure, and the liquid level rises as the flow rate increases and drops as the flow rate decreases. The surface need not be maintained in the quenching means.

The quenching means can be cooled by fins or water cooling pipes (not shown) if necessary, and can be controlled so that the surface temperature of the hole in contact with the molten metal falls within the range of 50 ° C. to 400 ° C. This method is suitable for a case where the throughput is relatively small, and in the case of this embodiment, it is 2 kg / min. The treatment of the molten metal discharged from the quenching means was the same as in the previous two cases, and the quality of the product was the same.

[0042]

According to the present invention, a semi-solid material can be manufactured by a relatively simple apparatus, and this material is used as a raw material for die forming, particularly, forging (squeeze casting) or die casting. Products with excellent mechanical properties.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a first embodiment of the present invention.

FIG. 2 is a diagram showing an outline of a second embodiment of the present invention.

FIG. 3 is a diagram showing an outline of a third embodiment of the present invention.

FIG. 4 is a diagram specifically showing a rapid cooling means in the present invention.

[Explanation of symbols]

 2 First holding furnace 2 'Stopper 4 Molten 5 Dispersing means 5' Other dispersing means 7, 8, 9 Quick cooling means 10 Molten in rapid cooling means 13 Second holding furnace 14 Molten in second holding furnace 18 Piston 22 Semi-solid material (slag) 26 slag

Claims (8)

[Claims] 1. A method of casting a semi-solid metal material, comprising the following steps. (A) a step of forming a metal material into a molten metal in a first holding furnace and maintaining the molten material at a liquidus temperature higher than the liquidus temperature in the range of 10 to 50 ° C .; (C) maintaining the melt containing the equiaxed crystal at a temperature below the liquidus temperature and above the solidus temperature in a second holding furnace, A phase ratio;
(D) a step of intermittently taking out the portion of the molten metal having the predetermined solid phase ratio. 2. The method according to claim 1, wherein the semi-solid material is a die-cast material. 3. A casting machine for a semi-solid metal material, comprising: (A) a first holding furnace having a heating means for holding the metal material at a liquidus temperature higher than the liquidus temperature in the range of 10 to 50 ° C. or higher, and a pouring means for discharging the molten metal; Quenching means for quenching the molten metal discharged by the pouring means to generate primary crystal equiaxed crystals; and (c) maintaining the molten metal containing primary crystal equiaxed crystals at a liquidus temperature or lower and a solidus temperature or higher. A second holding furnace having a predetermined solid phase ratio, and a means for intermittently removing a portion of the molten metal having the predetermined solid phase ratio. 4. The quenching means comprises: arranging a plurality of metal plates in parallel at a narrow interval at an inlet of the molten metal, arranging them in a middle bulge at an intermediate portion, and again arranging a plurality of metal plates at an outlet at a small interval. Placed so that there is a pool between the metal plates
4. A quenching means arranged so that the flow of the molten metal is not interrupted and flows down in a rectified state.
The described semi-solid casting machine for metal. 5. The quenching means includes: (a) a horizontally arranged triangular prism dispersing means for dispersing the molten metal flowing down from the first holding furnace; and (b) receiving the molten metal dispersed by the dispersing means. A multilayer cooling plate in which a plurality of plate-like cooling plates are arranged side by side at a wide interval at an inlet and narrower as going downward near an outlet of a flow path, and a molten metal is placed between the cooling plates or along the cooling plate. When the molten metal is poured in the vicinity of the cooling means outlet, at least a part of the gap is configured such that the molten metal forms a pool, the flow of the molten metal is not interrupted, and the multilayer cooling plate flows down by rectification. The metal semi-solid material casting machine according to claim 3, characterized in that: 6. The quenching means comprises: (a) a triangular pyramid-shaped dispersing means for dispersing molten metal flowing down from the first holding furnace;
(B) There is a sump in which the molten metal dispersed by the dispersing means is accumulated at the upper part, followed by a plurality of concentric slits having a large diameter at the upper part and a temporary diameter toward the lower outlet. When the molten metal is poured along the gap between the slits, the molten metal is formed in at least a part of the gap near the outlet, and the flow of the molten metal is not interrupted, and flows down by rectification. 4. The metal semi-solid material casting machine according to claim 3, wherein said casting machine comprises: 7. The metal semi-solid casting machine according to claim 4, wherein said quenching means has fins for temperature adjustment. 8. The quenching means according to claim 3, wherein a release agent is applied to a surface in contact with the molten metal.
7. A casting machine for a semi-solid material of a metal according to any one of items 1 to 6.