JPH0289541A - Apparatus for continuously manufacturing semi-solidified metal - Google Patents

Abstract

PURPOSE:To obtain apparatus for continuously manufacturing high quality semi- solidified metal by composing a molten metal vessel providing cooling means on the circumferential wall at bottom part having recessed conical face and a stirrer having projecting conical shape arranging lifting position adjusting device and constituting so as to supply the molten metal into gap between the above vessel and the stirrer. CONSTITUTION:The molten metal 20 in a ladle 18 is supplied 19 into a temp. holding vessel 1 and allowed to flow into the cooling stirring vessel 3 held to the fixed temp. In the vessel 3, the molten metal 20 is stirred in cooling stirred zone 29 consisting of the tapered annular gap formed with the recessed conical face of the vessel 3 and the projecting conical face of the stirrer 9. That is, the rotation shown by the arrow mark 24 is given to the molten metal 20 with the stirrer 9 to obtain the semi-solidified metal with the stirring effect. Then, this semi-solidified metal is continuously discharged 21 from a slide valve 7. In this case, the stirrer 9 is rotated at the fixed speed and by detecting 12 the loading torque, the lifting position adjustment of the stirrer 9 is executed with operation of a hydraulic unit 28 and a hydraulic cylinder 17 for lifting to control the semi-solidified metal under the optimum condition of cooling stirring zone 29.

Description

Detailed Description of the Invention (Industrial Application Field) This invention is a method of continuously producing a solid-liquid metal mixture (referred to as a semi-solid metal for simplicity) in which non-dendritic primary crystals are dispersed in a metal melt. The present invention relates to a device for manufacturing.

(Prior art) As disclosed in Japanese Patent Publication No. 56-20944, an apparatus for continuously producing semi-solid metal is used to maintain molten metal supplied to a heat-retaining tank at a constant temperature while producing a cylindrical metal. The metal is introduced into the gap between the stirrer rotating at high speed in a cooling stirring tank, and is subjected to an appropriate cooling action and strong stirring action to form a semi-solid state, and is continuously discharged as semi-solid metal from a nozzle at the bottom. .

This semi-solid metal is produced by vigorously stirring a molten metal (generally an alloy) while cooling it, converting the dendrites that are forming in the molten metal into a rounded shape with the branches disappearing or shrinking. It is formed by

The finer the particles of the non-dendritic primary crystals in semi-solid metals, the better their properties. Therefore, for semi-solid metal manufacturing equipment, ■ A strong cooling effect that can increase the cooling rate as much as possible.

■A stirring effect strong enough to transform dendrites into rounded non-dendritic crystals by eliminating or reducing their branches.

Although these two conditions are essential, conventional semi-solid metal manufacturing equipment that has failed to meet these conditions still has various drawbacks.

(Problems to be Solved by the Invention) Due to structural constraints, the device described in Tokuyo Special Publication No. 56-20944 has a cooling rate of 1°C/sec or less, and a maximum stirring strength of 450 sec-' at the shear strain rate. Moreover, there were also difficulties in temperature control, and in reality very good results were not obtained. The problems found by the inventors in this regard are listed below.

(1) If strong cooling means is employed to increase the cooling rate, a solidified shell is formed on the cooling surface, causing the stirrer to stick and become inoperable.

(2) Although it is effective to increase the rotation speed of the stirrer or reduce the gap between the cooling stirring tank and the stirrer in order to increase the stirring effect, increasing the rotation speed will cause the melt to deteriorate. In addition to the increased tendency of the stirrer to separate from the stirrer due to centrifugal force, which increases the risk of gas entrainment, there is also a limit due to constraints on structural strength. Practically speaking, it cannot be made very small because this causes an increase in viscous resistance.

(3) During unsteady heat transfer such as at the start of operation, excessive cooling may cause the stirrer to stick, making it difficult to start operation in a highly stable manner and making temperature control difficult.

(Means for solving the problem) In general, the stirring effect is proportional to the rotation speed of the stirring bar, but if the rotational gap of the stirring bar is small, a sufficient stirring effect can be obtained without requiring extremely high speed rotation. In addition, we focused on the fact that the main reason for the above-mentioned problems was that the rotational gap of the stirrer could not be arbitrarily controlled during operation, and after repeated development and research, we completed the invention. lead.

This invention has a molten metal tank with a cooling means on the bottom circumferential wall and a stirring bar rotating at the center of the bottom circumferential wall, and provides a cooling stirring effect while supplying molten metal to the gap between the bottom circumferential wall and the stirring bar. In an apparatus for continuously producing semi-solid metal, the bottom peripheral wall has a concave conical surface, the stirring bar corresponding thereto has a convex conical surface, and a cooling stirring zone is provided with a tapered annular gap formed by these. An apparatus for continuously producing semi-solid metal, characterized in that the stirrer is equipped with a lifting/lowering position adjusting device with respect to the molten metal tank, thereby making it possible to control the gap between the stirrer and the cooling stirring zone. be.

The apex angle of the cone forming the tapered annular gap of the cooling stirring zone is in the range of 30" to 120°, and the stirrer is equipped with a torque detector in its rotational drive system, and It is further useful to be able to control the raising/lowering position adjustment of the stirrer by adjusting the output according to variations in the load torque.

Now, in this invention, both the so-called cooling/stirring surface of the molten metal and the corresponding stirring bar are conical surfaces,
By moving the stirrer up and down, the gap in the cooling stirring zone can be controlled arbitrarily. Moreover, it is more preferable to automatically control this gap by measuring the viscous resistance torque.

In this way, the cooling/stirring tank can use strong cooling means, and even if a solidified shell is formed, it is possible to maintain an optimal gap and provide sufficient stirring effect, making it possible to maintain high-speed rotation. Not only is this unnecessary, but it is also easy to start operation, and even during regular operation, a self-coating state can be easily achieved, and there is no staining caused by fireproofing.

The specific configuration of this invention will be explained below with reference to FIG.

The semi-solid metal manufacturing apparatus according to the present invention includes a heat insulating tank 1, a cooling stirring tank 3, a discharge device 5, a stirring bar 9, and drive mechanisms 10 to 14 for the stirring bar 9. The heat-retaining tank 1 is a molten metal container lined with refractory material, and an induction heating coil is provided around its outer periphery, and the heat-retaining tank 1 is heated by supplying electric power 23.
The molten metal 20 inside is heated and maintained at a constant temperature. The cooling stirring tank 3 connected to the bottom of the heat-retaining tank 1 has an inverted conical inner surface, and a water-cooling jacket 4 is formed around it to allow cooling water 22 to pass therethrough for direct forced cooling. . Therefore, the heat retaining tank 1 and the cooling stirring tank 3 are nothing but a molten metal tank with a cooling means provided on the bottom peripheral wall.

A discharge part 5 is connected to the bottom of the cooling stirring tank 3, and an electric heater 6 is provided in the discharge part 5, and electric power 23 is supplied to this to maintain a constant temperature state, and the semi-solid metal passing through the discharge part 5 is heated. Solidification is prevented and the discharge amount is controlled by a slide gate valve 7 attached to the discharge section 5.

The upper part of the heat-retaining tank 1 is covered with a furnace M8 provided with a charging port 8' for molten metal raw material. Although not shown, the atmosphere of the heat-retaining tank j can be adjusted by blowing an inert gas or the like.

On the other hand, the stirring bar 9 has an inverted conical stirring surface corresponding to the cooling stirring tank 3, and the stirring bar 9 is installed at the center of the cooling stirring tank 3, and , can be rotated in the direction of an arrow 24 at a predetermined rotational speed by an electric motor 14.

The deceleration support device 11 and the electric motor 14 are connected through a torque detector 12, more preferably through a torque limiting joint 13, so that the electric motor 14 continues to rotate even when the stirrer 9 is stopped.

The driving mechanisms 10 to 13 of the stirrer 9 as a whole are the elevating frame 1.
5, and thereby the stirrer 9 is raised and lowered in the direction of the double-headed arrow 25. The elevating frame 15 is supported by guide rolls 16 and connected to an elevating hydraulic cylinder 17, and by the operation of pressure 28' from a hydraulic unit 28, it is raised and lowered up and down along arrows 25 using the guide rolls 11 as a guide. , position control is also possible.

(Function) Now, the molten metal 19 that has been placed in the ladle 18 is supplied into the heat-retaining tank 1 through the charging port 8'.

The molten metal 20 is maintained at a constant temperature in the heat-retaining tank 1 and flows into the cooling stirring tank 3 .

In the cooling stirring zone 29, which is formed by a tapered annular gap formed by the concave conical surface of the cooling stirring tank 3 and the convex conical surface of the stirring bar 9, the stirring bar is heated under the strong cooling effect of the water cooling jacket 4. A semi-solid metal is obtained by the stirring effect by the rotation shown by the arrow 24 of 9. This semi-solid metal is continuously discharged from the slide gate valve 7 in the direction of arrow 21.

In this case, the stirrer 9 rotates at a constant speed, and by detecting the load torque with the torque detector 12, the stirrer is 9 to control the state of the cooling stirring zone 29 to the optimum state. Even if a thick solidified shell is generated in the cooling stirring zone 29 due to strong cooling and excessive torque is generated, the torque is limited. Since the electric motor 14 is not stopped by the joint 13 even though the stirring bar 9 is stopped, operation can be resumed immediately by slightly widening the gap between the cooling stirring zone 29.

FIG. 2 shows the behavior occurring in the cooling stirring tank 3.

In this invention, in order to increase the cooling rate as much as possible, a copper plate 4' is used on the cooling surface of the water cooling jacket 4, and strong cooling can be achieved by passing cooling water at a high speed of 22 degrees to the back surface of the copper plate 4'. .

The molten metal that enters the gap between the cooling plate 4' and the stirrer 9 is
It comes into direct contact with the cooling plate 4' and is forcibly cooled to form a solidified shell 30. The thickness (d) of this solidified shell 30 is determined by the balance between the cooling capacity and the stirring effect. However, it is very unstable during operation, and tends to form thickly, especially at the start. Next, the stirring effect provided by the rotation of the stirrer 9 is proportional to the circumferential speed of the stirrer and inversely proportional to the gap, and is generally expressed as a function of the shear strain rate. As for the rotation speed, it is generally difficult to achieve a circumferential speed of 10 m/s or more due to constraints on centrifugal force, gas entrainment, and structural strength of the device, and high-speed rotation is not preferable from the standpoint of safety. Therefore, in order to provide a sufficient stirring effect, the most practical method is to maintain an appropriate gap.

However, when the solidified shell 30 is formed with a thickness d by performing strong cooling, the actual gap becomes (c-d) compared to the gap (c) on the device. Even if this gap is extremely unstable, if it becomes too small, excessive torque will be generated and there is a risk of sticking due to solidification, so a safe large gap C is selected in the design to provide a sufficient stirring effect. I couldn't.

In this invention, since the cooling stirring zone 29 has a tapered annular shape with an apex angle of 2θ, when the stirring bar 9 is raised by the stroke S as shown by the arrow 25, the radial gap is C' =
Increases to C+5sin θ. In other words, it becomes possible to control the gap.

In general, it is most ideal for a stable cooling stirring zone to have a cylindrical surface, which means that the stirring effect remains constant, that is, the radius of rotation remains constant, and by adjusting the length of the cylinder, a sufficient stirring area can be obtained. It is from. On the other hand, if a conical surface is used, the gap can be adjusted arbitrarily as described above, but in order to obtain a sufficient stirring area, the radius of rotation will change significantly, and the stirring effect will not be constant. It disappears.

Therefore, in order to obtain as stable agitation effect as possible when using a conical stirrer, the cooling stirring zone 29 is designed to have a radius of rotation as large as possible and a short axial length. Here, the apex angle 2θ of the conical surface is 30° ~ 1
A range of 20' is suitable.

In addition, in this invention, a stirring tank and a stirring bar having an inverted conical surface have been described, but a combination of a stirring tank and a stirring bar having a regular conical surface in which the gap can be adjusted by raising and lowering the stirring bar is applicable. Naturally, this is included within the scope of this invention.

(Embodiment) FIG. 3 shows a plurality of cooling/stirring tanks 2 at the bottom of a tundish 201 which is an intermediate container for molten metal according to the present invention.
02 and a stirrer 207 are provided, semi-solid metal 213 independently produced by each is supplied to each mold 211,
An example of continuously manufacturing a semi-solid metal billet 216 is illustrated. The container 201 is a container lined with fireproof material, and a predetermined number of cooling stirring tanks 202 are installed at the bottom of the container.
can be installed.

The cooling stirring tank 202 has an inverted conical surface on its inner surface, and most of the tank is a water-cooled jacket 1-203, and forced cooling is possible by passing cooling water 214 therethrough. A discharge part 204 and a slide gate valve 206 are attached to the bottom of the cooling stirring tank 202, and electric power 215 is supplied to an electric heater 205 to heat the manufactured semi-solid metal 213.
Continuously discharge while preventing coagulation.

On the other hand, a stirrer 207 having an inverted conical surface corresponding to the cooling stirring tank 202 is connected to a drive device by a drive shaft 208, and is rotated as shown by an arrow 209 and raised and lowered as shown by an arrow 210.
Position control is possible. The molten metal 212 in the dumpster 201 is maintained within a constant temperature range, flows into the tapered annular gap between the cooling/stirring tank 202 at the bottom and the stirring bar 207, that is, the cooling stirring zone, and is cooled by the water cooling jacket 203. Due to the effects of both cooling and stirring by the rotation of the stirrer 207, it becomes a semi-solidified state, and is continuously discharged via the discharge section 204 and the slide gate valve 206.

The semi-solid metal 213 continuously discharged from each cooling stirring device is directly supplied to the corresponding continuous casting mold 211 to produce a product billet 216.

In this case, the stirrer 207 is raised and lowered as described above, and can be controlled to maintain an appropriate gap between the cooling surface and the stirrer.

The production capacity of the apparatus of this invention varies depending on the physical properties of the target metal and the target solid phase ratio (ratio of solidified crystals present in the melt), but is determined by the cooling and stirring area, and is sufficient for conventional continuous casting technology. It is applicable and greatly useful for improving the quality of conventional cast products and reducing the heat load on equipment. Furthermore, by simply changing the mold 211, it is fully applicable to general casting processes.

(Effects of the Invention) The semi-solid metal manufacturing apparatus implementing the present invention exhibits the following effects.

(1) Strong cooling enables operation with an appropriate minimum gap, making it possible to increase the cooling rate to over 10°C/sec, making it possible to produce semi-solid metals with fine primary crystal grains and excellent properties. It has a large production capacity and is practical because it can be especially strongly cooled.

(2) Since stirring is performed with an appropriate minimum gap, a sufficient stirring effect can be obtained even if the rotation speed is less than half that of conventional ones, eliminating the danger of gas entrainment due to high-speed rotation. All structural, strength and safety issues in device design are resolved.

(3) The quality of semi-solid metal is stable because it can be operated while maintaining an appropriate minimum gap.

(4) It is possible to cope with the formation of an excessive solidified shell at the start, making it easy to start classes. In addition, even during long-term continuous operation, torque fluctuations are monitored during operation, so stable operation is possible without accidents.

[Brief explanation of the drawing]

Fig. 1 is an overall explanatory diagram showing the configuration of the present invention in cross section of the main parts, Fig. 2 is an enlarged view showing the action in the cooling stirring zone according to the invention, and Fig. 3 is an embodiment of the invention. FIG. 1...Heating tank 2...Induction heating coil 3
...Cooling stirring tank 4...Water cooling jacket 5.
...Discharge part 6...Electric heater 7...Slide gate valve 8...Lid 8'...Charging port
9... Stirrer 10... Drive shaft 11.
・・Deceleration support device 12・・Torque detector 13・
...Torque limiting joint 14...Electric motor 15
...Elevating frame 16...Guide roll 17...
・Hydraulic cylinder 18 for lifting...Ladle 2
6... Torque indicator needle 27... Controller 2
8... Hydraulic unit 7) Figure 1

Claims (1)

[Claims] 1. It has a molten metal tank with a cooling means on the bottom peripheral wall and a stirrer rotating at the center of the bottom peripheral wall, and supplies molten metal into the gap between the bottom peripheral wall and the stirrer. In an apparatus that continuously produces semi-solid metal by providing a cooling stirring effect, the bottom peripheral wall has a concave conical surface, the corresponding stirrer has a convex conical surface, and a Taber annular gap is formed by these. Continuously discharging semi-solid metal, comprising: a cooling stirring zone; and the stirring bar is equipped with a lifting/lowering position adjusting device with respect to the molten metal tank, thereby making it possible to control the gap between the cooling stirring zones. equipment manufactured in 2. The apparatus according to claim 1, wherein the apex angle of the cone forming the tapered annular gap of the cooling stirring zone is in the range of 30° to 120°. 3. The stirrer is equipped with a torque detector in its rotational drive system,
3. The apparatus according to claim 1 or 2, wherein adjustment of the vertical position of the stirrer can be controlled by adjusting output according to fluctuations in load torque via an indicator and a controller.