JPS583764A - Charging method for molten metal - Google Patents

Abstract

PURPOSE:To produce a cast ingot of good quality continuously by detecting the weight and temp. of the molten metal in a tundish controlling the rate of the cooling material to be charged into the tundish. CONSTITUTION:After the molten steel in a ladle 1 is flowed into a tundish 6, it is cooled by a cooling material 13 charged from a charger 12 for the cooling material. To control the charging rate of the cooling material, the weight of the molten steel 7 in the tundish 6 is measured with a load meter 8 mounted to the tundish 6 and is inputted to an operator 14, and the temp. of the molten steel 7 is measured with an IR thermometer 5A and is inputted to the operator 14. The target temp. for charging into a casting chamber 10 is beforehand inputted to the operator 14 by a keyboard 15 and the quantity of heat extraction necessary for cooling down to the charging temp. and the weight of the cooling material corresponding to the quantity of heat extraction are calculated. The amt. of the cooling material to be charged into the tundish 6 is controlled in the above- mention manner, whereby the molten steel 7 is cooled and is charged in the form of charging flow 9 into the casting chamber 10 formed by a rotary wheel type continuous casting mold 11.

Description

[Detailed Description of the Invention] The invention relates to a method of pouring molten metal, and in particular, to maintaining the molten metal poured into the mold at an appropriate temperature when continuously pouring the molten metal into the mold for continuous casting. The invention relates to a method for controlling the amount of coolant introduced into molten metal.

In the continuous casting method, a large amount of molten steel is held in a ladle, then dispensed into a tundish installed above the mold chamber, and then continuously injected into the mold chamber from the tundish. In this case, in order to obtain a high-quality ingot, the temperature of the molten steel injected into the mold chamber must be 20 to 4
It is necessary to raise the temperature to 0tZ', and if the injection temperature is higher than this, the solidified shell will break during casting and a huge crack will occur. Furthermore, if the pouring temperature is low, many wrinkles and surface cracks will occur on the surface of the ingot, and in extreme cases, the nozzle of the tundish will become clogged, making continuous casting impossible.

- Also, it generally takes about 70 minutes to pour all the molten steel held in the ladle into the mold. Therefore, in order to stably flow out the molten steel from the ladle at the end of production (that is, when the amount of molten steel in the ladle is close to the minimum value), the temperature of the molten steel in the ladle must be 40° higher than the temperature at which it is poured into the mold. ~600
It has to be of a high degree. The reason for this is that at the end of production, the temperature of the molten steel in the ladle drops and the nozzle is clogged, and the molten steel solidifies in the ladle and no longer flows out.

Therefore, the temperature of the molten steel flowing into the tundish is higher than the temperature at which the molten steel is poured into the mold. For this reason, conventionally, the temperature of the molten steel in the tundish was intermittently measured and a coolant having the same chemical composition as the molten steel was poured into the tundish to cool the molten steel to an appropriate injection temperature. However, this method has the following problems.

Figure 1 shows the injection results when 45 tons of 5D-30 steel were cast using a rotary wheel type continuous casting machine at a casting speed of 4.0 to 4.5 m/-, and when the coolant was injected using the conventional coolant injection method described above. It shows the change in molten steel injection temperature over time. At the initial stage of injection, the tundish is cold, so the injection temperature of the molten steel is at an appropriate temperature, but as time passes, the injection temperature tends to rise due to heating by the molten steel. Therefore, after 5 minutes, a coolant made of 5D-30 steel, which has the same chemical composition as the molten steel, is intermittently added to suppress the temperature rise, but if too much is added, the temperature rises after 40 and 60 minutes. As can be seen at time point, the injection temperature is below the lower limit of the target injection temperature. In this way, in the conventional technology, coolant is injected only by measuring the temperature of molten steel in the tundish.
It was not possible to quickly determine the amount of coolant to be added in response to changes in the amount of molten steel in the tundish during pouring, and it was difficult to control the pouring temperature with high precision.

The purpose of the invention is to provide a method for pouring molten metal that can precisely control the amount of coolant added to the molten metal so that the temperature of the molten metal poured into the mold can be maintained at an appropriate temperature. .

The first aspect of the invention is to detect the amount, that is, the weight or volume (or the height of the molten metal surface) of the molten metal area in a container in which a coolant is introduced to cool the molten metal, and further to detect the amount of molten metal after the coolant is introduced. The temperature on the way to the mold is detected, and the amount of coolant introduced is controlled with high precision based on these detection signals.

The second aspect of the present invention is to detect the above-mentioned detection signal and the temperature and amount of molten metal flowing into a container into which a coolant is input to cool the molten metal, and to detect the temperature and amount of molten metal based on these detection signals. The amount of input can be controlled more precisely and better.

Hereinafter, embodiments of the invention will be described in detail based on the drawings.

In FIG. 2, a large amount of molten steel held in a ladle 1 flows into a tundish 6, is cooled by a coolant 13 fed from a coolant feeder 12, and then becomes an injection stream 9 of molten steel. The liquid is injected into a mold chamber 10 formed by a rotating continuous mold 11.

Here, as a method of controlling the amount of coolant input, first, the weight of molten steel in the dish 6 is measured using a load meter 8 attached to the tundish 6, and this value is input into the computer 14. The temperature of the molten steel 7 in the cased tundish 6 is measured with an infrared thermometer 5A, and this value is input to the computer 14. The target injection temperature into the mold chamber 10 is input in advance into the keyboard 15 of the computer 14, and the difference between the molten steel temperature in the tandy tube 6 and the injection temperature is calculated based on this injection temperature, and the temperature of the molten steel in the tandy tube 6 is calculated. Multiplying the weight of the molten steel in 6 and including the physical property values of the molten steel and refractory, calculate the amount of heat removal required to cool the molten steel to the reference injection temperature. In addition, the heat removal capacity per weight of the coolant to be poured into the bath/steel is inputted to the computer 14, and based on the calculated value of the heat removal amount described above, the molten steel is cooled to the reference injection temperature. The weight of the coolant corresponding to the amount of heat removal required for this is calculated. In this way, the amount of coolant injected into the tundish 6 is accurately controlled.

Note that instead of measuring the temperature of the molten steel in the tundish 6, the temperature of the molten steel on the way from the tundish 6 to the rotating continuous mold 11 may be measured with an infrared thermometer 5C, and this measured value may be input to the computer 14. See you soon Tanditshu 6
Both the measured value of the temperature of the molten steel inside the tundish 6 and the measured value of the molten steel temperature on the way from the tundish 6 to the rotary continuous mold 11 may be input to the calculator 14 to perform calculations. These can be used depending on the required accuracy.

Next, the temperature of the molten steel and the weight of the molten steel in the tundish 6 are measured manually and input to the computer 14, and the temperature of the molten steel flowing from the ladle 1 into the tundish 6 is measured using a total infrared thermometer 5.
B, the amount of molten steel flowing into the tundish 6 is measured by the load cell 3 attached to the ladle 1, and these measured values are input into the computer 14, and the calculation is performed in the same manner as described above. The amount of coolant injected into the interior can be controlled with greater precision.

In the above embodiment, the weight of molten steel in the tundish 6 is measured by the load cell 8, but the amount of molten steel is measured by a level meter installed in the tundish 6, and the amount of molten steel is added to the tundish 6 per unit time. The inflow amount and the amount of molten steel in the tundish 6 per unit time may be measured, and these measured values may be input to the computer 14 to perform calculations.

The coolant introduced into the tundish 6 is not limited to one having the same chemical composition as the molten steel, but may include iron scraps 1. All metals or alloys such as chromium, manganese, iron alloys, etc. can also be used. When using a metal or alloy that does not have the same chemical composition as the molten steel, it is possible to simultaneously cool the molten steel in the tundish 6 and improve the physical properties of the final casting.

Next, the effects of the present invention will be explained based on specific casting conditions.

Here, the cross-sectional dimensions of the ingot are 130X130X160 (II
For the trapezoidal rotating ring type continuous mold 11 of III), 3.
The aim was to control the injection temperature of molten steel into the mold to 15401: at a casting speed of 8 to 4.4 m/-, and the operation was performed so that the weight of molten steel in the tundish 6 was 2.5 to 3.0 tons. .

The weight of the molten steel 2 in the ladle 1 holding 45 tons of 5D-40 steel was measured using a load meter 3. Further, the temperature of the molten steel flow 4 flowing out from the bottom of the ladle 1 was measured with an infrared thermometer 5B. Roughly, the total weight of the molten steel 7 in the tundish 6 was measured using a load cell 8 attached to the tundish 6, and the temperature of the molten steel 7 was measured using an infrared thermometer 5A. These values were then input into the computer 14. The temperature of injection into the mold chamber 10 is set to 1540 in advance on the computer 14 using the keyboard 15.
C was input, and the temperature difference between this injection temperature and the molten steel flow 4 from the ladle 1 was calculated. The weight of the molten steel flowing into the 17t tundish 6 was measured every 10 seconds using the load cell 3, and was calculated by subtracting the current measured value from the previous measured value using a computer. Then, the amount of heat required to cool the molten steel flow flowing into the tundish 6 at the injection temperature 1 was calculated by multiplying the temperature difference between the temperature of the molten steel flow and the injection temperature by the weight of the molten steel flowing into the tundish 6.

[-In parallel, similar arithmetic processing is performed to calculate the difference between the temperature of the molten steel 7 in the tundish 6 and the injection temperature by the weight of the molten steel in the tundish 6.
Calculate the amount of heat required to cool down to the injection temperature. Based on the cooling amount obtained in this way, input it into the computer 14 from the keyboard 15, and calculate the weight of the cooling amount required for cooling the molten steel from the cooling amount per unit weight of 7'n5D-30 steel at room temperature. , thickness 10+a+, width 50 with coolant injection machine 12
A 5D-30 steel plate measuring 50 m+ was placed in a tundish 6, and the injection temperature was fully controlled. In this case, the interval between the calculation and the injection of the cooling device 13 was set to be every 1 minute during the 5 minutes from the start of injection in the case when the injection was stable, and every 2 minutes after that time when the injection was stable.

FIG. 3 shows fluctuations in the molten steel injection temperature over time in such a control operation for the amount of coolant input. In Figure 3, at the beginning of the molten steel injection operation, the ladle 1 is cold, so the injection temperature is slightly lower than the target injection temperature, but after that, the amount of coolant input is controlled and the injection temperature is lower than the initial injection temperature. This shows that the temperature is controlled within a range of 5C.

As described above, according to the present invention, it is possible to accurately control the temperature at which molten metal is poured into the mold chamber, and therefore it is possible to continuously produce ingots of good quality through stable continuous casting operations. can.

[Brief explanation of drawings]

Fig. 1 is a diagram showing changes in molten steel injection temperature over time in the conventional molten metal injection method, Fig. 2 is a block diagram showing an example of the non-invention, and Fig. 3 is a diagram showing changes in molten steel injection temperature over time according to the present invention. It is a figure showing a fluctuation. 1... Ladle, 2,7... Molten steel, 3.8... Load cell, 4... Molten steel flow, 5A, 5B, 5C... Infrared thermometer, 6... Tandish, 9 ...Injection flow, 10.
... Mold chamber, 11... Mold, 12... Coolant injection machine, 13... Coolant, open during injection Sleeve j Main incoming volume i

Claims (1)

[Claims] 1. After the molten metal is held in the first container, it flows into the second container, where a coolant is poured into the molten metal to cool the molten metal, and then the molten metal is In the method of pouring molten metal into a mold from a second container, the amount of molten metal in the second container is detected, and the temperature of the molten metal on the way from inside the second container to just before the mold is detected. , a molten metal injection method in which the amount of coolant injected into the second container is controlled based on these detection signals. 2. After holding the molten metal in the first container, it flows into the second container, where a coolant is introduced into the molten metal to cool the molten metal, and then the molten metal is transferred from the second container into the mold. In the molten metal injection method, the amount of molten metal in the second container is detected, and the temperature of the molten metal on the way from the second container to just before the mold is detected. Detecting the temperature and amount of molten metal flowing into the second container, and controlling the amount of coolant introduced into the second container based on these detection signals. Molten metal injection method.