JPS633704B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a casting method using a belt-and-wheel continuous casting method, and in particular monitors the temperature change of the rotating wheel during casting and increases or decreases the amount of cooling water depending on the state of the temperature change, thereby producing high quality casting. This allows for stable production of lumps over a long period of time. In the belt-and-wheel type continuous casting method, an endless belt is brought into contact with a part of the outer peripheral surface of a rotating wheel with a groove provided on the outer periphery, a water-cooled mold is formed in the contact section (hereinafter abbreviated as the wrap section), and the mold is Molten metal is poured continuously from one end, and ingots are continuously drawn from the other end. In such continuous casting, the poured molten metal solidifies in the lap section, and the quality of the cast ingot is largely determined by the solidification form in the lap section. However, this lap section is long, occupying 30 to 80% of the circumference of the rotating wheel, and cannot be seen from the outside, so it is extremely difficult to maintain stable ingot quality for a long time. For example, the molten metal in the mold starts cooling at the point where it is poured, and the molten metal that comes into contact with the mold
Since it is cooled only by the mold, the thickness of the solid phase (shell) that first solidifies in the mold is the temperature of the mold,
It depends on the heat capacity determined by thermal conductivity, shape, etc. In addition, a gap (air gap) is created between the molds depending on the thickness of the shell formed immediately after pouring, reducing the cooling ability of the mold.Furthermore, changes in the degree of air gap cause fluctuations in the cooling ability of the mold. Significantly affects lump quality. In the conventional belt-and-wheel type continuous casting method, in order to maintain constant mold quality, the side temperature of the rotating wheel is constantly measured by placing a thermocouple in contact with one or more places on the side of the rotating wheel, and the temperature change is monitored. The amount of cooling water for the mold is controlled accordingly. Generally, after the belt leaves the rotating wheel, a thermocouple is placed in contact with the side surface before and/or after the molten metal is poured to measure the temperature of the rotating wheel and control the amount of cooling water in the mold. However, this method only controls the temperature of the rotating wheel that influences the shape of the shell, and it is difficult to control the dynamic solidification form within the mold. In view of this, the present invention has been developed as a result of studying the control of mold cooling conditions to maintain the optimal dynamic solidification form within the mold in the belt-and-wheel type continuous casting method. A continuous casting method has been developed that allows for continuous casting, in which an endless belt is brought into contact with a part of the outer circumferential surface of a rotating ring with grooves on the outer circumference to form a water-cooled mold.
In continuous casting, the molten metal is poured from one end of the mold and the solidified ingot is pulled out from the other end.
Alternatively, two or more thermocouple insertion holes are provided, and the thermocouples are fixed and installed at arbitrary positions within the insertion holes to measure the temperature rise and fall pattern for each revolution inside the rotating wheel during casting. The system compares the temperature with a preset standard temperature pattern, increases the amount of cooling water when the temperature is high, and decreases the amount of cooling water when the temperature is low, thereby making the temperature pattern of the rotating wheel match the standard temperature pattern. It is something to do. The reason why thermocouples are fixed and installed at arbitrary positions is that although the installation location may be arbitrary, once the location has been decided, temperature comparisons cannot be made unless the thermocouples are fixed. That is, in the belt-and-wheel type continuous casting method of the present invention, for example, as shown in FIG. and the idler wheel 5, and the rotating wheel 1
and a water-cooled mold 6 is formed in the lap section of the belt 2,
In continuous casting, a tundish 7 is provided at one end of the mold 6, molten metal is poured into the mold 6, and an ingot 8 is pulled out from the other end.As shown in FIG. A thermocouple insertion hole 10 is provided in the lower rotating ring 1, a thermocouple 11 is inserted into the insertion hole 10, and its tip 12 is set on the central axis a of the rotating ring 1 at a certain distance from the bottom of the groove 9. Although the rear end of the thermocouple 11 is not shown in the figure, it is connected to a slip terminal provided on the shaft of the plates 13, 13' that support the rotating wheel 1, and the temperature signal inside the rotating wheel is transmitted through the terminal. and display it on the record. In this way, the temperature rise and fall patterns inside the rotary wheel 1 during casting are compared with a preset standard temperature pattern every revolution, and the amount of cooling water for the mold 6 is increased or decreased in accordance with the difference. Here, it is difficult to increase or decrease the amount of cooling water for each revolution of the rotating wheel 1 because the rotating speed of the rotating wheel 1 is fast. By monitoring and increasing the amount of cooling water for the mold 6 when the temperature of the rotating wheel 1 is higher than the standard temperature pattern, and decreasing the amount of cooling water when it is lower, high quality ingots can be produced stably for a long time. This is what I did. In addition, two or more thermocouple insertion holes 10 are provided in the rotating wheel 1.
The thermocouple 11 may be inserted into each insertion hole 10. In this case, each thermocouple 11 is compared with the standard temperature pattern, and the amount of cooling water in the mold 6 is adjusted to reduce the difference. All you have to do is increase or decrease. The amount of cooling water for the mold 6 may be increased or decreased depending on the difference between the standard temperature pattern and the temperature pattern of the rotating wheel 1, but as shown in Fig. Cooling areas 14a, 14b, 14c, 1 where piping is provided and water volume can be controlled independently
4d so that the opening degree of each valve can be automatically adjusted using an electromagnetic valve. In this way, the standard temperature pattern inside the rotating wheel 1 is grasped and set in advance, and this is compared with the temperature pattern for each revolution inside the rotating wheel during casting. The ingot quality is effectively stabilized by detecting the presence or absence of the temperature fluctuation pattern inside the rotary wheel 1 by increasing or decreasing the amount of cooling water at the front stage of the cooling area where a difference is found, and always matching the temperature fluctuation pattern inside the rotating wheel 1 with the standard temperature pattern. This enables stable production of high-quality ingots over a long period of time. Although an example has been described in which the thermocouple insertion hole 10 is provided on the side surface of the rotating ring 1 and the thermocouple 11 is inserted, the invention is not limited to this. For example, the thermocouple insertion hole may be provided in the rotating ring from the inside of the rotating ring 1. A thermocouple may be inserted into this. Although an example was explained in which the cooling area of the mold 6 is divided into four equal parts, the invention is not limited to this. For example, if the length of the cooling area is l, each cooling area 1
The length of 4a is 1/7l, the length of 14b is 2/7l, 14
The length of each cooling zone may be changed such that the length of c is 2/7l and the length of 14d is 2/7l. Furthermore, it may be divided as appropriate, but from the point of view of responsiveness, 4
Splitting is most preferred. The present invention will be described in detail below with reference to examples. In the belt-and-wheel continuous casting method shown in Figure 1, the diameter of the rotating ring is 2000 mm, the wrap angle between the rotating ring and the belt is 210°, and the cross-sectional area of the groove of the rotating ring is
Using a continuous casting machine with ^{a diameter} of 2,600 mm2, molten aluminum was poured at a temperature range of 670 to 720°C, and a caster of 15 to 25 cm/
Casting was carried out at a casting speed of sec. As shown in Figure 2, a thermocouple insertion hole is provided in the rotating ring that reaches the center axis 20 mm below the groove bottom from the side of the rotating ring, and an alumel or chromel thermocouple is inserted into the insertion hole and attached to the axis of the plate. The temperature signal inside the rotating wheel was displayed on the recorder via the provided slip terminal. In this way, the pouring temperature is 700℃ and the casting speed is 20℃.
Casting was carried out under constant conditions at cm/sec and total cooling water flow rate of 1000/min, and the temperature fluctuation pattern inside the rotating ring and the surface quality of the ingot were investigated. In a casting machine with a wrap angle of 210° where the casting wheel and belt are in contact, the wrap length of 3600 mm is divided into four equal parts, each with a cooling zone of 900 mm, and the cooling zone,
,,. The total amount of cooling water is 1000/
min, but the amount of water flowing to each cooling area is 200/
min, 300/min, 300/min, and 200/min. Casting was carried out in this state, and the signal from the thermocouple set at a position 20 mm from the bottom of the casting groove was displayed on an oscilloscope. The typical results are shown in FIG. The figure shows the temperature fluctuation pattern for each rotation inside the rotary wheel during casting. If the ingot temperature is below 480℃ and large cracks occasionally occur on the ingot surface, C
This is a case where sweating and many minute cracks are observed on the surface of the ingot at a temperature of 510℃ or higher. In other words, pattern B corresponds to surface flaws and/or surface deterioration of the rotating wheel when heat transfer from the ingot to the mold is excessive, the ingot temperature is low, and the ingot temperature is high. Stress concentrates on the surface of the ingot and large cracks form. In pattern C, heat transfer from the ingot to the mold is insufficient, the ingot temperature is high, and the temperature of the rotating wheel is low, and an air gap occurs between the ingot and the rotating wheel immediately after the start of casting. This indicates that heat transfer is not occurring smoothly. By monitoring the temperature change pattern inside the rotary wheel during casting in this manner, it becomes possible to grasp the solidification form within the mold, and it also becomes possible to know the degree of ingot quality. Although the results shown in FIG. 3 are the results obtained under the same casting conditions, there are differences in the temperature change inside the rotating ring. This is due to a change in the thickness of the very thin coating material applied to the rotating wheel.
This coating material uses rapeseed oil or soot, but it is currently very difficult to measure the thickness of this coating, and it is also difficult to control the coating thickness, so the coating material does not vary evenly during casting. This is a phenomenon in which the quality of the ingot is not stable under the casting conditions, and is recognized from time to time in the production process. In FIG. 3, the amount of water flowing into each cooling zone was the same as at the start of casting, but a temperature pattern was shown on the oscilloscope that was different from the mold temperature obtained at the start and standard times. For pattern B, the casting wheel temperature in the cooling area is standard A.
The water volume in the cooling area has been increased from 200/min to 250/min to make it the same as standard A.
increased to As a result, the temperature pattern in the cooling zone matched that of standard A, but the temperature in the cooling zone was still 15℃ higher than that of standard A, and as a result of gradually increasing the water flow rate in the cooling zone from 300/min.
The water flow rate was 320/min, which matched standard A. That is,
By setting the amount of water in each cooling zone to 200, 320, 300, and 250/min, the temperature distribution of the thermocouple set in the casting ring matched standard A, and the large cracks that had occurred on the ingot surface disappeared. Sound ingots can now be obtained. On the other hand, when pattern C was obtained, the temperature of the casting wheel in the cooling zone was low, so the water amount in the cooling zone was reduced by 200/
When the speed was gradually decreased from min to 180/min, the temperature distribution in the cooling region matched Standard A. However, since the temperature in the cooling zone is about 10℃ lower than standard A, when the water flow rate in the cooling zone is gradually reduced from 200/min, the temperature distribution matches that of standard A at a flow rate of 190/min, and the overall temperature pattern is It became type A and no micro defects were generated. The difference in the temperature change of the casting wheel during casting is integrated in each cooling region against the standard temperature pattern shown in advance on the oscilloscope, and if the average temperature difference exceeds 5°C, the increase or decrease of the cooling water is determined. I started it. In the present invention, the cooling conditions are controlled so that the temperature change pattern inside the rotating wheel is always constant (for example, pattern A in FIG. 3) even if the thickness of the coating changes. That is, as shown in Fig. 1, in the belt-and-wheel type continuous casting method, the lap section between the rotating wheel and the belt is divided into four equal parts, and a cooling area is formed in which the water volume can be controlled using separate piping systems.
The valve opening of each cooling zone can be automatically adjusted using a solenoid valve. These cooling zones are written as No., No., No., No. in order from the one closest to the spout.
Each of these cooling zones was controlled as follows using the flowchart below, and the temperature fluctuation inside the rotating wheel was always kept constant to stabilize the quality of the ingot. For example, understand the temperature pattern of the rotating wheels and compare it with the standard temperature pattern. If there is a difference in No., increase or decrease the amount of cooling water for No., and if there is no difference in No., increase or decrease the amount of cooling water for No. Increase or decrease the amount of cooling water. In the same way, if there is no difference between No. and No., increase or decrease the amount of cooling water for No., and when there is no difference between No., No., No., and No. Increase or decrease the amount of cooling water for No. Also No.
, No., No., When there is no difference in No., the amount of cooling water is kept constant without changing. That is, (1) The temperature change pattern inside the rotating wheel is determined by a thermocouple inserted inside the rotating wheel. (2) Compare with the set standard temperature pattern and determine whether there is a difference. (3) First, determine whether there is a difference from the number closest to the spout. That is, the quality of the ingot and the form of solidification within the mold depend on the solidification state at the initial stage of casting, and under normal operation, temperature fluctuations tend to occur from No. (4) Increase or decrease the amount of cooling water in the cooling area before the cooling area where a difference from the standard temperature pattern is observed. That is, it is controlled as follows. Cooling area where a difference was observed Cooling area to be controlled No. → No. No. → No. Cooling area where a difference was observed Cooling area to be controlled No. → No. No. → No. (5) Cooling water control is Although it is possible to change the amount of cooling water in multiple cooling areas at the same time,
Only one cooling zone was controlled per revolution. This is a better control method in terms of preventing hunting and the like. The total number of large flaws, medium flaws, and small flaws on an average of 1 hour for the ingots continuously cast in this manner was investigated.
The results were compared with conventional method a, in which the cooling water was controlled manually while monitoring the quality of the ingot, and conventional method b, in which the water amount was controlled by placing a thermocouple in contact with the side of the rotating ring to keep the temperature constant. The results are shown in Table 1. The casting conditions were an ingot temperature of 700°C, a casting speed of 20 cm/sec, and a total amount of cooling water of 1000/min.

[Table] From Table 1, the ingots cast by the method of the present invention are:
It can be seen that the occurrence of defects is significantly reduced compared to ingots cast by the conventional method. As described above, according to the present invention, one or more thermocouples are inserted into the rotating ring in the belt-and-wheel type continuous casting method, and the amount of cooling water in the cooling area is controlled by the temperature change. It is possible to produce defect-free ingots stably for a long period of time, and has a significant industrial effect.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the method of the present invention;
FIG. 2 is a cross-sectional view of the rotating ring shown in FIG. 1, and FIG. 3 is an explanatory diagram showing a temperature change pattern for each rotation inside the rotating ring during casting. DESCRIPTION OF SYMBOLS 1...Rotating wheel, 2...Belt, 3...Presser wheel, 4...Tension wheel, 5...Idler wheel, 6...Mold, 7...Tundaishu, 8...
Ingot, 9...Groove, 10...Thermocouple insertion hole, 11...Thermocouple.

Claims (1)

[Claims] 1. A water-cooled mold is formed by bringing an endless belt into contact with a part of the outer peripheral surface of a rotating ring having a groove on the outer periphery, and molten metal is continuously poured from one end of the mold, and In continuous casting, in which the solidified ingot is pulled out from the end, one or more thermocouple insertion holes are provided in the rotating ring, and the thermocouples are fixed and installed in the insertion holes at arbitrary positions, and the rotating ring is used during casting. By measuring the internal temperature rise and fall pattern for each revolution and comparing this with a preset standard temperature pattern, if the temperature is high, the amount of cooling water is increased, and if the temperature is low, the amount of cooling water is decreased. A continuous casting method characterized by matching the temperature pattern of a rotating wheel with a standard temperature pattern. 2 Divide the mold cooling area of the rotary ring into multiple parts, compare the temperature rise and fall pattern for each rotation inside the rotary ring during casting with a preset standard temperature pattern, and compare the temperature rise and fall pattern of the mold cooling area of the previous stage of the cooling area where a difference has occurred. The continuous casting method according to claim 1, wherein the amount of cooling water in the cooling zone is increased or decreased.