JPS61293629A - Method for discharging slag after casting of ladle having bottom blowing plug - Google Patents

Abstract

PURPOSE:To prevent the sticking of slag to a bottom blowing plug and to extend the life of the plug by ejecting gas from the bottom blowing plug into the slag while the slag exists in a ladle after casting. CONSTITUTION:The molten steel is poured via a nozzle 5 from the ladle 1 contg. the molten steel into a casting mold. A piping 7 for purging is connected to a piping 4 upon ending of the casting and the gas from a tank 8 is supplied to the bottom blowing plug 3 to eject the gas into the slag. The ladle 1 is then titled to discharge the slag in the ladle 1 into a slag receiver 9. The gas is kept ejected from the bottom blowing plug 3 during the slag discharge. The sticking of the slag to the bottom blowing plug 3 is obviated and the clogging of the plug 3 is prevented by such operation. The ejection of the gas is stopped after the end of the slag discharge. The nozzle clogging is prevented and the gas flow rate in the succeeding stirring stage is stabilized by the above- mentioned discharging method.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is for storing molten metal such as molten steel or hot metal, and for stirring the molten metal by blowing gas into the molten metal from a bottom blowing plug provided at the bottom of the molten metal. The present invention relates to a method for discharging slag after casting from a ladle with a bottom blowing plug used.

[Prior Art] Molten steel after being refined in a converter is stored in a ladle with a refractory built into the steel shell and transported to a casting facility. A bottom blowing plug is installed at the bottom of the ladle, and a stirring gas such as Ar gas or nitrogen gas can be blown into the molten steel through the bottom blowing plug.

The molten steel discharged from the converter into the ladle is stirred in a bubbling field by blowing gas through a bottom blowing plug to equalize its temperature, or the molten steel and slag are stirred by gas. This is called ladle refining. Thereafter, the ladle is carried into continuous casting equipment or ingot making equipment, and molten steel is injected into the mold through a nozzle provided at the bottom of the ladle. Immediately after the injection of molten steel is completed and the nozzle is closed, the steel ladle is tilted and the slag remaining in the ladle is discharged into the slag receiver. This empty ladle steel is transported to a ladle repair shop and installed in a bottom blowing plug, for example, 5 ka/
C112 nitrogen gas is passed through to check the flow, piping, etc.

[Problems to be Solved by the Invention] However, the time required for the slag to arrive at the ladle repair shop after the completion of casting varies for each charge, and the properties such as the viscosity and melting point of the slag also vary. For this reason, when the bottom blower plug arrives at the ladle repair shop, the slag has penetrated and adhered to the top surface of the bottom blower plug, and ventilation may not be possible. Then, the bottom blow plug will have to be replaced, and for this reason,
Conventionally, there has been a problem that bottom-blowing plugs have a short lifespan.

In addition, if the ventilation of the bottom blowing plug is poor, sufficient gas will not be blown into the molten steel during the subsequent stirring process, leading to problems in equalizing the temperature of the molten steel and failure in ladle refining due to slag.

[Means for Solving the Problems] The present invention has been made in view of the above circumstances, and has a bottom blowing plug that can extend the life of the bottom blowing plug and maintain good air permeability. The object of the present invention is to provide a method for discharging slag after casting a ladle.

The method for discharging post-casting slag from a ladle having a bottom-blowing plug according to the present invention is a method for discharging post-casting slag from a ladle having a bottom-blowing plug installed at the bottom, in which post-casting slag is present in the ladle. In this state, gas is supplied to the bottom blowing plug and the gas is ejected from the bottom blowing plug into the slag after casting.
Next, after the cast slag is discharged from the ladle, the gas jetting is stopped.

[Embodiments] Hereinafter, embodiments of the present invention will be specifically described with reference to the attached drawings. FIG. 1 is a schematic diagram showing the state of implementation of the present invention. A ladle 1 is suspended from a crane 6,
As shown in FIG. 2, this ladle 1 is constructed by constructing a refractory material inside an iron shell 2. At the bottom of ladle 1,
A bottom blow plug 3 is installed. This bottom blowing plug 3
A gas pipe 4 is connected to the gas pipe 4, and the pipe 4 is connected to an appropriate gas supply source. A nozzle 5 for injecting molten steel is installed at the bottom of the ladle 1, and during casting, this nozzle 5 is opened and molten steel is injected.

On the other hand, a tank 8 storing a purge gas such as Ar gas or N2 gas is installed on the floor or on a crane, and the purge gas 7 is connected to the tank 8. By connecting this purge pipe 7 to the bottom blowing plug 3, gas can be blown out from the bottom blowing plug 3.

Molten steel is tapped into the ladle 1 constructed in this manner from a converter, and is transported to a bubbling field.

In this bubbling field, the piping 4 and the bottom blowing plug 3
Ar gas or N2 gas is blown into the molten steel through
Molten steel is stirred with gas. Thereby, the temperature and composition of the molten steel are made uniform. Alternatively, the ladle is carried into a ladle refining facility, where molten steel and slag are similarly gas-stirred through a bottom blowing plug, and the molten steel is refined by the slag.

Next, the ladle 1 is transported by a crane 6 to a casting facility for continuous casting or ingot making, and molten steel is injected into a mold through a nozzle 5. After the casting process is completed, connect the purge pipe 7 to the pipe 4.
Connect to. Then, gas is supplied from the tank 8 to the bottom blowing plug 3 via the pipes 4 and 7, and the gas is jetted from the bottom blowing plug 3 into the slag. Next, the ladle 1 is tilted as shown in FIG. 1 to discharge the slag in the ladle into the slag receiver 9. During this slag discharge, gas is being blown out from the bottom blowing plug 3, so that the slag does not stick to the bottom blowing plug 3, and clogging of the bottom blowing plug 3 is prevented. After the sludge has been removed, the ladle 1 is transported to a ladle maintenance shop where the gas flow rate of the bottom blow plug is checked.

The pressure of the purge gas in the tailings is preferably 2 g/ClN2 or higher. In Figure 3, the horizontal axis shows the purge gas pressure during slag discharge, and the vertical axis shows the flow rate check (pressure 5 kg).
FIG. 2 is a graph showing the relationship between the two gas flow rates (by nitrogen gas of 012). As is clear from this figure, in order for the bottom blowing plug 3 to have sufficient air permeability (check flow rate is 30ON+/min or more) after the slag is drained, the purge pressure during the slag must be 2 kg/C12 or higher. is necessary.

Figure 4 shows the initial flow rates of bottom-blown gas obtained in the following gas agitation processes when gas purge is performed during slag drainage and when gas purge is not performed as in the conventional case. It is a graph diagram shown as frequency. As is clear from this figure, the initial flow rate is low in the conventional case (outlined) and is 30ON+/min in most cases, whereas the initial flow rate is high in the case according to the present invention (shaded), and in most cases is 30ON+/min or more.

[Effects of the Invention] According to the present invention, slag is prevented from sticking to the bottom blowing plug, and the need to replace the bottom blowing plug due to nozzle blockage can be avoided. Therefore, the life of the bottom blowing plug can be extended from the conventional 5 to 7 charges to 15 to 16 charges. Further, in the subsequent gas stirring process, a gas flow rate of 30 ON+/min or more can be stably obtained.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the implementation state of this invention, Fig. 2 is a schematic diagram of a ladle, Fig. 3 is a graph diagram showing the relationship between purge gas pressure and flow rate, and Fig. 4 shows the effects of this invention. It is a graph diagram. 1: Ladle, 3: Bottom blowing plug, 4, 7: Piping, 5: Nozzle, 8: Tank. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In a method of discharging post-casting slag from a ladle with a bottom-blowing plug installed at the bottom, gas is supplied to the bottom-blowing plug while the post-casting slag is present in the ladle, and the slag after casting is discharged from the bottom-blowing plug. A method for discharging post-casting slag from a ladle having a bottom-blowing plug, the method comprising: discharging gas from the ladle, discharging the post-casting slag from the ladle, and then stopping the discharging of the gas.