JPS60115351A - Continuous casting method - Google Patents

Abstract

PURPOSE:To supply stably a molten metal and to obtain a billet having high quality by adjusting the quantity of the heat to be extracted from the molten metal in the part of an immersion nozzle in accordance with the temp. of the molten metal and controlling the temp. of the molten metal to be supplied into a casting mold. CONSTITUTION:When the temp. of a molten metal 2 in a casting mold 5 measured by a thermometer 18 is higher than a prescribed casting temp., a valve driving means 15 is operated by a control circuit 16 for the valve driving means. The opening degree of a valve 14 is increased to increase the flow rate of a cooling medium thereby increasing the quantity of the heat to be extracted from the molten metal 2 flowing down in an immersion nozzle 4 and decreasing the temp. of the metal 2. The temp. of the metal 2 in the mold 5 is kept adequate and the opening degree of the valve 14 is increased or decreased by actuating the means 15 to that the temp. of the metal 2 in the mold 5 is maintained at the prescribed casting temp.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a continuous casting method applied to manufacturing slabs by continuously supplying molten metal into a mold.

(Prior art) In the continuous casting method, molten metal placed in a ladle is transferred into a tundish, and this molten metal is continuously supplied into a mold through a submerged nozzle provided at the bottom of the tundish. This is a method of continuously drawing out slabs formed by solidifying parts one after another, and is significantly more productive than conventional ingot-forming methods, so its adoption is rapidly spreading.

Figure 1 schematically shows the equipment used in such a continuous casting method, in which 1 is a tundish, 2 is a molten metal, 3 is a stopper, 4 is an immersion nozzle, 5 is a mold, 6 is a slab, and 7 is a roll, and the molten metal 2 supplied into the tundish 1 flows into the immersion nozzle 4 when the stopper 3 is raised.
It is supplied into the mold 5 through the mold 5, and is solidified in the mold 5 starting from the outer shell oil to form the slab 6, which is continuously pulled out downward while being guided by the rolls 7.

In continuous casting using such a device, the temperature of the molten metal 2 in the tundish 1 is such that solidification occurs rapidly in the mold 5 and the secondary cooling zone behind it, and at the same time a good solidification structure and macro segregation are formed. It is desirable to keep the temperature of the molten metal 2 as low as possible, but if the temperature of the molten metal 2 is lowered in this way, a solidified portion 8 as shown in FIG. However, by reducing the opening diameter of the immersion nozzle 4 and reducing the flow rate of the molten metal 2, there was a problem in that the level of molten metal in the mold 5 decreased, which could hinder continuous casting.

(Object of the Invention) This invention has been made by focusing on the problems of the conventional art as described above. It is an object of the present invention to provide a continuous casting method that allows a stable supply of steel and continuously produces slabs with a good solidified structure.

(Structure of the Invention) The present invention provides a continuous casting method in which molten metal in a tundish is supplied into a mold through an immersion nozzle, when the temperature of the molten metal in the tundish becomes higher than an appropriate casting temperature, or The temperature of the molten metal in the tundish is set higher than the appropriate casting temperature in advance, and the immersion nozzle portion is appropriately insulated or cooled in accordance with the temperature of the molten metal, thereby preventing melting at the immersion nozzle portion. By adjusting the amount of heat removed from the metal and controlling the temperature of the molten metal supplied into the mold, stable continuous casting can be performed at an appropriate casting temperature without solidifying the molten metal at the immersion nozzle. It is characterized by the fact that

In the continuous casting according to the present invention, in order to adjust the amount of heat removed from the molten metal at the immersed nozzle portion, it is possible to form a cooling medium passage for water cooling or air cooling inside the immersed nozzle, or to It is possible to adopt a mode in which a cooling box, cooling pipes, etc. for cooling medium distribution are installed.

Then, when adjusting the amount of heat removed from the molten metal at the immersion nozzle part, the temperature of the molten metal in the tundish and the mold is continuously measured, and the flow rate of the cooling medium is controlled in accordance with the measured temperature, In this way, the temperature of the molten metal supplied into the mold may be continuously and automatically controlled to an appropriate temperature.

(Example) Fig. 2 is a diagram showing an example of the present invention, in which 1 is a tundish, 2 is a molten metal, 3 is a stopper, 4 is an immersion nozzle, 5 is a mold, 6 is a slab, and 7 is a roll. It is. Also,
11 is a cooling box installed around the immersion nozzle 4, 12 is a cooling medium discharge pipe, 13 is a cooling medium inflow pipe, 14 is a valve,
15 is a valve driving means; 16 is a valve driving means control circuit; 17 is a thermometer for measuring the temperature of the molten metal 2 in the tundish 1; 18 is a thermometer for measuring the temperature of the molten metal 2 in the mold 5; 12 is a temperature measuring means.

In this example, JISS 0M42 is used as the molten metal 2.
0 steel (A content of 0.03% by weight) is used.
It was transferred from the ladle at 550°C. Then, with the stopper 3 open, the molten metal 2 is supplied from the immersion nozzle 4 to the mold 5, and during this time, water is poured into the cooling box 11 as a cooling medium from the cooling medium inflow pipe 13, and is discharged from the cooling medium discharge pipe 12. did. The flow rate of the cooling medium at this time is adjusted so that the temperature of the molten metal 2 in the mold 5 as measured by the thermometer 18 is 1515° C., which is an appropriate casting temperature. That is, the temperature of the molten metal 2 in the tundish 1 measured by the thermometer 17 is higher than the predetermined casting temperature as described above, and the temperature of the molten metal 2 in the mold 5 measured by the thermometer 18 is higher than the predetermined casting temperature. If the temperature of the valve 1 is also higher than the predetermined casting temperature, the valve driving means 15 is actuated via the valve driving means control circuit 16, and the valve 1 is activated.
4 is increased to increase the flow rate of the cooling medium, the amount of heat removed from the molten metal 2 flowing down in the immersion nozzle 4 is increased, the temperature of the molten metal 2 is lowered, and the molten metal 2 in the mold 5 is
When the temperature reaches the appropriate casting temperature, check the thermometer 18. By operating the valve driving means 15 via the temperature measuring means 12 and the valve driving means control circuit 16, the opening degree of the valve 14 is kept constant, or the opening degree of the valve 14 is increased or decreased as appropriate to control the molten metal 2 in the mold 5. temperature is maintained at the predetermined casting temperature.

Therefore, the temperature of the molten metal 2 in the tundish 1 is higher than the predetermined casting temperature, and the solidified portion 8 as shown in FIG. 1 is not formed in the immersion nozzle 4, resulting in stable This makes it possible to carry out continuous casting. In addition, since the temperature of the molten metal 2 supplied into the mold 5 is controlled to a predetermined casting temperature that is as low as possible, it becomes easier to obtain a slab 6 with good solidification structure and macro segregation. Variations in the solidification structure, segregation, etc. in the length direction of the slab 6 are significantly reduced, and a slab 6 of constant quality can be obtained.

(Effects of the Invention) As described above, according to the present invention, in a continuous casting method in which molten metal in a tundish is supplied into a mold through a immersion nozzle, the immersion nozzle portion The temperature of the molten metal supplied into the mold is controlled by adjusting the amount of heat removed from the molten metal in the tundish. By setting the casting temperature to a predetermined casting temperature, it is possible to prevent the molten metal from solidifying at the immersion nozzle part as in the conventional method, and the opening diameter of the immersion nozzle is reduced or blocked, making continuous casting impossible. It is now possible to avoid the occurrence of stable re-breakout, and it is possible to produce high-quality slabs with little variation in solidification structure and macro segregation in the length direction with stable operation. It has excellent effects.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a continuous casting apparatus using a conventional continuous casting method, and FIG. 2 is an explanatory diagram of a continuous casting apparatus according to an embodiment of the present invention. 1... Tandish 2... Molten metal 3... Stopper 4... Immersion nozzle 5... Mold 6... Slab 11... Cooling box 17.18... Thermometer Patent applicant Daido Special Steel Co., Ltd. Patent Attorney Yutaka Oshio JP-A-6O-115351 (4) Figure 2

Claims (1)

[Claims] (1) In a continuous casting method in which molten metal in a tundish is supplied into a mold through a submerged nozzle, the amount of heat extracted from the molten metal at the submerged nozzle portion is adjusted according to the temperature of the molten metal, and A continuous casting method characterized by controlling the temperature of the molten metal supplied to the