JPH06297098A - Production of half solidified metal - Google Patents

Abstract

PURPOSE:To continuously and stably produce the half solidified metal by preventing the excessive growth of a solidified shell by the heat extracting heat flow flux of a cooling plate and the shearing strain rate of a solid-liquid boundary, thereby preventing an increase in the torque of a spiral screw type stirrer at the time of cooling molten metal under rotation of this stirrer. CONSTITUTION:The half solidified metal is produced by cooling the molten metal injected into a cylindrical cooling vessel having the cooling plate from the upper part of this vessel under rotation of the spiral screw type stirrer. The excessive growth of the solidified shell is prevented by the heat extracting heat flow flux of the cooling plate and the shearing strain rate of the solid-liquid boundary, by which the increase in the torque of the stirrer is prevented. The relation between the heat extracting heat flow flux of the cooling plate and the shearing strain rate of the solid-liquid boundary satisfies the inequality. The inequality gamma>3.4(m<2>/kcal).q, where gamma: the shearing strain rate (s<-1>) of the solid-liquid boundary, q: the heat extracting heat flow flux (kcal/m<2>.s) of the cooling liquid. As a result, the increase in the torque generated in the stirrer is prevented and the half solidified metal having fine primary crystal grgins and high solid phase rate is continuously and stably produced.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention continuously stabilizes a slurry-like solid-liquid metal mixture (hereinafter simply referred to as semi-solid metal) in which non-dendritic primary crystals are dispersed in a metal (generally an alloy) liquid. It proposes a method for producing a semi-solid metal produced by the above method.

The semi-solidified metal can be processed into materials having good internal quality, a downstream processing step, that is, a rheoform directly processed into a product, or a solidified metal once solidified and then reheated to a semi-molten state for processing. Stable industrial production of semi-solidified metal from its usefulness, such as enabling substantial reduction of processing energy by realizing near net shape in thixocasting, forging, etc. and the possibility of developing new materials. Development of technology is desired.

[0003]

2. Description of the Related Art As a means for continuously producing a semi-solid metal, it is disclosed in, for example, Japanese Patent Publication No. Sho 56-20944 (apparatus for continuously forming an alloy containing non-dendritic primary crystal solids). As shown in the figure, the molten metal at a constant temperature is introduced into the gap between the inner surface of the cylindrical cooling tank and the stirrer rotating at high speed, cooled while applying a strong stirring action, and the resulting semi-solid metal is cooled from its bottom. A mechanical stirring method of continuously discharging (hereinafter referred to as a stirrer rotation method) is known. A method of using electromagnetic force as the stirring method (hereinafter referred to as electromagnetic stirring method)
Is also well known.

As another means, the molten metal is supplied to a gap between a single roll having heat removal ability and rotating around the horizontal axis and a fixed wall formed of a concave curved surface along the outer circumference of the roll, and the roll is rotated. A means for producing semi-solidified metal by the generated shear strain at the solid-liquid interface (hereinafter referred to as a single roll method) is disclosed in JP-A-3-142040 (method and apparatus for continuously producing semi-solidified metal) and JP-A-3-142040. No. 4-238645 (method and apparatus for producing semi-solidified metal).

In any of these means, the solid phase particles in the semi-solidified metal are agitated while cooling the molten metal, whereby the branches of the dendritic primary crystals that are being formed in the melt disappear or shrink. Then, it is formed by being converted into a rounded form.

It is said that the finer the non-dendritic primary crystal grains and the higher the solid fraction of the semi-solidified metal, the more excellent the quality characteristics of the product obtained from the semi-solidified metal. The size becomes finer as the cooling rate increases.

For this reason, as an apparatus for producing semi-solidified metal, an apparatus capable of strong cooling is required. However, strong cooling is performed to produce semi-solidified metal having fine primary crystal grains and high solid fraction. In this case, the apparent viscosity becomes large, so that the fluidity becomes very poor, and it becomes difficult to discharge the semi-solidified metal having a high solid fraction in a continuous and stable manner.

When the above-mentioned means are examined from the viewpoint of the discharging ability of the semi-solidified metal, in the single roll method, the discharge of the generated semi-solidified metal is promoted by the rotation of the roll, and the solidified shell attached to the surface of the roll is Since it is scraped off by a scraper, even if the solid fraction of the semi-solidified metal to be discharged is large, there are few obstructive factors for discharging, and the discharging ability is very excellent. However, in the stirrer rotation method and the electromagnetic stirring method, since the supplied molten metal is stirred by rotation around the center of the cooling tank as a rotation axis, the pressure on the wall surface of the cooling tank due to centrifugal force increases. , The discharge capacity will be reduced. Therefore, in the stirrer rotation method and the electromagnetic stirring method, establishment of a technique for increasing the discharge capacity of semi-solidified metal becomes a particularly important issue.

On the other hand, in the stirrer rotation method and the electromagnetic stirring method, if the discharge capacity can be increased, the manufactured semi-solidified metal is passed through a nozzle or directly extruded into a shape such as a round cross section or a square cross section. Enables direct processing of high solid fraction semi-solidified metal (Reoform),
It is a very excellent means for shaping semi-solidified metal, such as billet processing.

From this point of view, the stirrer rotation method is used as a means for improving the ability to discharge semi-solidified metal, as disclosed in Japanese Patent Laid-Open No. 4-124231 (semi-solidified metal manufacturing apparatus), by the inventor of the present invention. Using a spiral screw stirrer,
We have proposed a device that incorporates a means to forcibly feed the semi-solidified metal generated in the cooling tank downward, but there is still room for improvement as it is industrially commercialized.

[0011]

Under the circumstances as described above, the inventors of the present invention further conducted experiments on the stirrer rotation method, and as a result, in the conventional means, even if a paddle is adopted as the stirrer, a spiral screw is used. Even if adopted, the torque of the stirrer increases due to the growth of the solidified shell generated on the inner surface of the cooling tank with the lapse of time after the start of semi-solid metal discharge, and this increase in torque hinders the continuous discharge of semi-solid metal. We came to discover that it would be a factor.

Therefore, in order to take advantage of the excellent features of the stirrer rotation method, it is necessary to prevent the excessive growth of the solidified shell and prevent the torque generated in the stirrer from rising and continuously discharge the semi-solidified metal. Establishing becomes an important issue to be solved.
In view of the above, an object of the present invention is to propose a method for producing semi-solidified metal by the stirrer rotation method, which can advantageously solve such problems and continuously and stably discharge semi-solidified metal.

[0013]

In order to solve the above-mentioned problems, the inventors have studied the torque increasing mechanism of the stirrer including the shape of the stirrer and achieved the present invention. That is, the gist of the present invention is as follows.

In a method for producing a semi-solid metal, in which a molten metal poured from an upper portion of a cylindrical cooling tank having a cooling plate is cooled under the rotation of a spiral screw stirrer, a heat removal heat flux of the cooling plate and A method for producing a semi-solidified metal, characterized by preventing an excessive growth of a solidified shell and preventing an increase in torque of a stirrer by a shear strain rate at a solid-liquid interface.

The method for producing a semi-solid metal according to the item [1], wherein the relationship between the heat removal heat flux of the cooling plate and the shear strain rate at the solid-liquid interface satisfies the following formula (1).

[Equation 2]

The method for producing a semi-solidified metal according to the item or item, wherein the thickness of the solidified shell that grows on the inner surface of the cooling plate is limited according to the value of the set clearance between the cooling plate and the stirrer.

[0017]

The present invention will be described in detail below based on experimental results. The semi-solid metal manufacturing apparatus shown in FIG. 1, that is, the hot water receiving tank 5, the cooling tank 6, the holding tank 7, the discharge amount control nozzle 12, and the stirrer 10 rotating at the center of the cooling plate 8 of the cooling tank 6.
By means of an experimental device mainly composed of the torque meter 3 and the torque meter 3, the heat removal heat flux (heat removal speed) of the cooling plate 8 of the cooling tank 6 and the solid-liquid interface, which increase the torque of the stirrer 10 by using the molten Al alloy, The influence of the shear strain rate and the shape of the stirrer 10 was examined.

FIG. 2 shows the stirrer 1 used in this experiment.
In the explanatory view showing the shape of 0, (a) shows a paddle-screw composite type in which a helix screw is attached to the tip of the paddle, and (b) shows an all-screw stirrer 10 of the whole helix screw.

First, the solid phase ratio of the semi-solid metal discharged is
0.45, and the gap between the cooling plate 8 and the rotating stirrer 10 set before pouring the melt 1 (set clearance) is 15 m.
m and stirrer 10 with the elapsed time from the start of discharge
The influence of the shape of the stirrer 10 on the torque increase of
Shown in.

The solid phase ratio of the semi-solidified metal discharged in the above was controlled by adjusting the retention time of the poured molten metal 1 in the cooling tank 6 by the discharge amount control nozzle 12. Further, the heat removal rate of the cooling plate 8 of the cooling tank 6 is calculated based on the temperature rise of the cooling waste water of the cooling tank 6, the measured value of the temperature by the thermocouple embedded in the cooling plate 8, and the like. The two types shown in FIGS. 2 (a) and 2 (b) were about 800,000 kcal / m ² h, which were the same.

As shown in FIG. 3, when the all-screw stirrer 10 is used, the elapsed time from the start of discharge when the torque of the stirrer 10 starts to increase when the paddle / screw composite stirrer 10 is used. It became clear that it became slower than the above, and that making the stirrer 10 into a helical screw is effective for preventing the torque increase of the stirrer 10.

The reason why the torque of the stirrer 10 increases is that the clearance between the stirrer 10 and the solidified shell gradually decreases due to the growth of the solidified shell formed on the inner surface of the cooling plate 8. Therefore, when the shape of the stirrer 10 is changed to the spiral screw, the start timing of torque increase is delayed, which means that the growth speed of the solidified shell is decreased by changing the stirrer 10 to the spiral screw. .

FIG. 4 shows the influence of the shape of the stirrer 10 on the torque increase of the stirrer 10 with the lapse of time from the start of discharge when the set clearance is 20 mm. Here, making the set clearance larger than in the case of FIG. 3 means that the heat removal rate of the cooling plate 8 when the solidification shell approaches the stirrer 10 becomes smaller.

The solid phase ratio of the semi-solidified metal discharged in the above was adjusted by the same method as in FIG. 3 so as to be 0.45. Further, the heat removal rate of the cooling plate 8 decreases as the thickness of the solidified shell formed on the inner surface of the cooling plate 8 increases.

Under the conditions shown in FIG. 4, the torque of the stirrer 10 is increased when the shape of the stirrer 10 is a paddle / screw composite type, whereas the torque is prevented from being increased in the all-screw type under the condition of FIG. is made of.

As described above, the reason why the condition for preventing the increase of the torque generated in the stirring bar 10 exists is that the stirring bar 10 is used.
The violent shear strain rate of the solid-liquid interface generated by the high-speed rotation of No. 2 increases with the growth of the solidified shell formed on the inner surface of the cooling plate 8 as shown in the following formula (2) (the solidified shell and the stirrer 10 As a result, the separation rate of the solidified shell due to the rotation of the stirrer 10 gradually increases, while the growth rate of the solidified shell does not become smaller as the solidified shell grows. This is probably because there are conditions under which the fragmentation rate of the shell and the growth rate of the solidified shell are equal.

[0027]

[Equation 3]

Therefore, the result shown in FIG. 4 is that the growth speed of the solidified shell is slower in the case of using the all-screw stirrer 10 as described above than in the case of using the paddle / screw composite type stirrer 10. That is, the torque of the stirrer 10 can be prevented from increasing at a smaller solidified shell breaking speed, that is, at a smaller shear strain speed at the solid-liquid interface.

Therefore, the full-screw type shown in FIG. 2 (b) is used as the stirrer 10 which is advantageous for preventing the excessive growth of the solidified shell, and the shear strain rate at the solid-liquid interface which can prevent the increase in the torque of the stirrer 10 is set. The cooling plate 8 was examined for each heat removal rate. The results are summarized in FIG.

Here, the shear strain rate at the solid-liquid interface was adjusted by changing the rotation speed of the stirrer 10 and calculated from the above equation (2). Further, the heat removal rate of the cooling plate 8 is calculated from the temperature gradient measured by the thermocouple embedded in the cooling plate 8 and the heat transfer coefficient of the material of the cooling plate 8, and in the cooling tank 6 of the poured molten metal 1. It was also calculated and confirmed from the temperature drop, the growth behavior of the solidified shell, and the cooling surface area of the cooling plate 8.

In the above formula (2), the stirring bar 10
The clearance S at which the torque starts to rise is about 0.8 mm according to the analysis result of the torque rising behavior, and this value was also confirmed from the tracer addition test.

The straight line in FIG. 5 is a boundary line which can prevent the torque of the stirrer 10 from increasing, and shows the lower limit of the shear strain rate of the solid-liquid interface required for stopping the growth of the solidified shell according to each heat removal rate. The straight line is represented by the following equation (3).

[0033]

[Equation 4]

It is clear from FIG. 5 that the increase in the torque generated in the stirrer 10 can be prevented by selecting the shear strain rate at the solid-liquid interface according to the heat removal rate. From this result, when it is desired to increase the heat removal rate in order to make the primary crystal grain size of the semi-solidified metal fine, the high shear strain rate of the solid-liquid interface corresponding to the heat removal rate, that is, the region that satisfies the above formula (1) If the operation is carried out in the above manner, there is no hindrance due to the increase in the torque of the stirrer 10, and it is possible to manufacture a semi-solidified metal having a high solid fraction and fine primary crystal grains.

At this time, the lower limit of the shear strain rate at the solid-liquid interface necessary for preventing the increase in the torque of the stirrer 10 can be lowered by using the all-screw type stirrer 10, and the rotation speed of the stirrer 10 can be reduced. Considering that there is an upper limit to the above, by using a spiral screw for the stirring bar 10, it becomes possible to cope with a region of a higher heat removal rate as compared with a paddle type or the like.

Further, in order to perform stable operation, when operating in the high shear strain velocity region of the solid-liquid interface where the torque of the stirrer 10 shown in FIG. 5 does not increase, that is, the region satisfying the above formula (1) is set. By making the clearance sufficiently large, the heat removal rate and the solidification shell growth rate decrease as the solidification shell grows, and conversely the shear strain rate at the solid-liquid interface increases as shown in the above formula (2), and the solidification shell grows. Growth is Figure 5
It stops until it reaches the boundary line, and the clearance at that time becomes a value larger than 0.8 mm mentioned above.

This means that the heat removal rate can be adjusted so that the torque of the stirrer 10 can be prevented from increasing due to the set clearance, and optimization of the set clearance is extremely important for realizing stable operation. Is.

Next, in FIGS. 6 and 7, the solid phase ratio of the semi-solidified metal discharged is adjusted to 0.45 and the set clearance is set to 2
5 shows the influence of the shape of the stirrer 10 on the discharge rate and the discharge flow rate under the conditions shown in FIG.

In these figures, the discharge speed and the discharge flow rate when the all-screw type stirrer 10 is used are higher than those when the paddle / screw composite type is used, and the stirrer 10 is not a spiral screw. It can be seen that not only the effect of preventing the torque increase of the stirrer 10 but also the effect of increasing the production amount is effective. Further, an increase in the discharge flow rate leads to a reduction in troubles such as nozzle clogging in the discharge nozzle, which facilitates stable operation.

FIG. 8 shows the influence of the shape of the stirrer 10 on the ratio of the amount of heat of the temperature drop of the molten metal to the total amount of heat removed from the cooling plate 8 (hereinafter referred to as molten metal cooling efficiency) in the experiment of FIG. . As is clear from FIG. 8, it is understood that the molten metal cooling efficiency is increased by using the all-screw stirrer 10. The reason for this is that by changing the shape of the stirrer 10 to a spiral screw, the growth rate of the solidified shell becomes slower as shown in FIG. It is thought that it was distributed.

As described above, when the semi-solidified metal is produced by the stirrer rotation method using the spiral screw stirrer 10, the solid-liquid interface according to the heat removal rate (heat removal heat flux) of the cooling plate 8 is obtained. Adopting the shear rate, satisfying the region where the torque of the stirrer 10 does not increase shown in FIG. 5, that is, the above formula (1), and further, solidifying shell generated on the inner surface of the cooling plate 8 according to the initially set clearance. By limiting the thickness, etc., it is possible to prevent the excessive growth of the solidified shell generated on the inner surface of the cooling plate 8, avoid the increase of the torque of the stirrer 10 and the trouble of the discharge nozzle, and to improve the solid phase up to 0.45 which was difficult in the past. The rate of semi-solidified metal can be discharged continuously and stably.

[0042]

【Example】

Example 1 An explanatory view of a semi-solid metal manufacturing apparatus in which an experiment was carried out is shown in FIG. The main configuration of this apparatus includes a hot water receiving tank 5, a cooling tank 6 having a cooling plate 8, a holding tank 7, a stir bar 10, a discharge amount control nozzle 12 (sliding nozzle), and a torque meter 3. In addition, in FIG. 1, 1 is a molten metal, 2 is a stirring motor, 4 is a tundish, 9 is a cooling spray of the cooling plate 8, and 11 is each heater of the hot water receiving tank 5 and the holding tank 7.

In the production of semi-solidified metal by the above apparatus, the stirrer 10 is used with two types of paddle-screw composite type and full screw type shown in FIGS. 2 (a) and 2 (b), respectively. Each of the hot water tank 5 and the holding tank 7 has a heater 11
Also, the discharge amount control nozzle 12 is burner (not shown).
After sufficiently preheating with the above, the molten metal 1 adjusted to an appropriate temperature is injected from above the device through the tandem 4, and the semi-solid metal is removed by removing heat from the cooling plate 8 of the cooling tank 6 and stirring by rotating the stirrer 10. And the solid fraction of the semi-solidified metal to be discharged is adjusted by controlling the residence time in the cooling tank 6 with the discharge control nozzle 12, and the desired solid fraction from the discharge control nozzle 12 is adjusted. It was carried out by discharging the semi-solidified metal.

In the experiment, an Al-10 mass% Cu alloy was used, the solid phase ratio of the discharged semi-solidified metal was 0.45, and the set clearance, that is, the gap distance between the cooling plate 8 of the cooling tank 6 and the stirrer 10 was 15 mm. , Stirrer 10 by torque meter 3
The time-dependent change of the torque generated in the was measured. Further, the ratio of the amount of heat corresponding to the temperature drop of the molten metal to the total amount of heat removed from the cooling plate 8 at that time, that is, the cooling efficiency of the molten metal was investigated. The results are shown in FIGS. 3 and 8.

FIG. 3 is a graph showing the influence of the shape of the stirrer 10 on the change over time in the torque generated in the stirrer 10 when the set clearance is set to 15 mm from the start of discharging semi-solidified metal. The torque generated in the stirrer 10 in the above is the torque generated in the initial stage due to mechanical loss or the like.

As shown in FIG. 3, the time-dependent change in the torque generated in the stirrer 10 varies depending on the shape of the stirrer. In the case of the all-screw type stirrer 10, the torque rises more than in the case of the paddle / screw composite type. The start time is delayed, and the growth speed of the solidified shell becomes slower by changing the shape of the stirrer to a spiral screw.

FIG. 8 is a graph showing the influence of the shape of the stirrer 10 on the cooling efficiency of the molten metal (the ratio of the amount of heat corresponding to the temperature drop of the molten metal to the total heat removal amount of the cooling plate 8). As is clear from FIG. 8, the cooling efficiency of the molten metal is higher in the case of the all-screw type stirrer 10 than in the case of the paddle / screw combined type stirrer 10, although the heat removal rates are almost the same. In order to change the shape of the stirrer 10 into a spiral screw,
It is also shown to be effective in improving the cooling efficiency of the molten metal.

Next, the change over time of the torque generated in the stirrer 10 was measured by the same method as above with the set clearance set to 20 mm. In addition, the discharge rate and discharge flow rate of the semi-solid metal at that time were also investigated. When the stirrer 10 is a paddle / screw composite type, the discharge speed and the discharge flow rate are values near the start of torque increase, and in the case of the full screw type, values after the growth of the solidified shell is stopped are adopted.

FIG. 4 is a graph showing the influence of the shape of the stirrer 10 on the change over time of the torque generated in the stirrer 10 when the set clearance is set to 20 mm from the start of discharging the semi-solidified metal. In the above description, the torque generated in the stirrer 10 excludes the torque initially generated due to mechanical loss or the like.

As shown in FIG. 4, when the set clearance is increased to 20 mm as compared with the case of FIG. 3 (the heat removal rate at the limit where the torque of the stirrer 10 does not increase becomes small), the paddle screw combination The mold stirrer 10 cannot prevent the increase in the torque generated in the stirrer 10, but the use of the all-screw stirrer 10 can prevent the increase in the torque.

FIG. 6 is a graph showing the influence of the shape of the stirrer 10 on the discharge rate of the semi-solid metal, and FIG. 7 is a graph showing the influence of the shape of the stirrer 10 on the discharge flow rate of the semi-solid metal. . As shown in FIGS. 6 and 7,
The discharge speed and the discharge flow rate of the semi-solidified metal also differ depending on the shape of the stirrer 10, and the discharge performance is better when the full screw type is adopted.

As described above, in the production of semi-solidified metal by the stirrer rotation method, the stirrer 10 is generated by optimizing the set clearance, that is, the heat removal rate, by using the stirrer 10 having a spiral screw. It is possible to prevent an increase in the torque that occurs, and to increase the discharge amount, so that it is possible to stably discharge the semi-solidified metal to a range where the solid fraction is higher than in the conventional case.

Example 2 Similar to Example 1, an experiment was conducted using the semi-solid metal producing apparatus shown in FIG. As the stirrer 10, the full screw type shown in FIG. 2 (b) was used. JIS-52 for the experiment
No. 02 AC4C, JIS H-5302 ADC12, and JIS H-4000 2024 were used.

Then, the heat removal rate of the cooling plate 8 of the cooling tank 6 is adjusted by changing the set clearance, the amount of cooling water, the material and structure of the cooling plate 8, and the heat removal rate is adjusted by the cooling plate 8.
It was calculated from the temperature gradient and the heat transfer coefficient measured by a thermocouple embedded inside. The shear strain rate at the solid-liquid interface was adjusted by the rotation speed of the stirrer 10 and calculated from the equation (2).

It was calculated based on these experiments. FIG. 5 shows the relationship between the heat removal rate of the cooling plate 8 and the shear strain rate at the solid-liquid interface, which can prevent the torque generated in the stirrer 10 from increasing. As is clear from FIG. 5, the increase in the torque generated in the stirrer 10 is within the range in which the shear strain rate of the solid-liquid interface shown in FIG. This can be prevented by selecting a range that satisfies the relationship of the above formula (1). Therefore, if the operation is performed under the above conditions, the torque of the stirrer 10 does not increase and the semi-solidified metal having a high solid fraction can be continuously and stably discharged.

[0056]

EFFECTS OF THE INVENTION The present invention provides a method for producing a semi-solidified metal by a stirrer rotating method using a spiral screw stirrer. By optimizing the above, it is possible to prevent an increase in torque generated in the stirrer, and to continuously and stably produce fine primary crystal grains and a high solid fraction semi-solidified metal.

According to the present invention, a rheoform for directly processing a semi-solid metal, a thixocast for solidifying the semi-solid metal and then reheating it into a semi-molten state, and a near net shape in forging are realized. By doing so, the processing energy can be greatly reduced, and it is possible to develop new materials that take advantage of the characteristics of semi-solidified metal, and the effects are enormous.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a semi-solidified metal manufacturing apparatus used in an experiment.

FIG. 2 is an explanatory view showing the shape of a stirrer used in an experiment. (a) is an explanatory view of a paddle / screw composite type stirrer in which a spiral screw is attached to the tip of the paddle. (b) is an explanatory view of an all-screw type stirrer having a helical screw as a whole.

FIG. 3 is a graph showing the influence of the shape of the stirrer on the change over time of the torque generated in the stirrer when the set clearance is set to 15 mm from the start of discharging semi-solidified metal.

FIG. 4 is a graph showing the influence of the shape of the stirrer on the change over time of the torque generated in the stirrer when the set clearance is set to 20 mm from the start of semi-solid metal discharge.

FIG. 5 is a graph showing the relationship between the heat removal rate of the cooling plate and the shear strain rate of the solid-liquid interface, which can prevent an increase in the torque generated in the stirrer.

FIG. 6 is a graph showing the influence of the shape of a stirrer on the discharge rate of semi-solidified metal.

FIG. 7 is a graph showing the influence of the shape of a stirrer on the discharge flow rate of semi-solidified metal.

FIG. 8 is a graph showing the influence of the shape of the stirrer on the cooling efficiency of the molten metal.

[Explanation of symbols]

 1 Molten Metal 2 Stirring Motor 3 Torque Meter 4 Tundish 5 Hot Water Tank 6 Cooling Tank 7 Holding Tank 8 Cooling Plate 9 Cooling Spray 10 Stirrer 11 Heater 12 Emission Control Nozzle

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[Procedure amendment]

[Submission date] June 14, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

[0027]

[Equation 3] ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 24, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

[0027]

[Note 3] [Note] γ = 2 · r ₁ · r ₃ · Ω / (r ₃ ² −r ₁ ² ) −−− (2) r ₃ = r ₂ −d = S + r ₁ where γ: solid-liquid Interfacial shear strain rate (s ^-1 ) r ₁ : Stirrer radius (m) r ₂ : Cooling tank radius (m) Ω: Stirrer angular velocity (rad / s) S: Clearance r ₃ : Molten metal radius in cooling tank ( m) d: solidified shell thickness (m)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyoshi Takahashi, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Stock Company Rheotec (72) Akihiko Namba 1, Kawasaki-cho, Chuo-ku, Chiba Stock Company In rheotech

Claims (3)

[Claims] 1. A method for producing a semi-solid metal, in which a molten metal injected from an upper portion of a cylindrical cooling tank having a cooling plate is cooled under the rotation of a stirrer in the form of a spiral screw, and a heat removal heat flow of the cooling plate. A method for producing a semi-solid metal, characterized by preventing excessive growth of a solidified shell and preventing an increase in torque of a stirrer by means of a shear strain rate between a bundle and a solid-liquid interface. 2. The method for producing a semi-solid metal according to claim 1, wherein the relationship between the heat removal heat flux of the cooling plate and the shear strain rate at the solid-liquid interface satisfies the following expression (1). [Equation 1] 3. The method for producing a semi-solidified metal according to claim 1, wherein the thickness of the solidified shell growing on the inner surface of the cooling plate is limited according to the value of the clearance set between the cooling plate and the stirrer.