JPS59145722A - Cooling method of lance for stirring molten metal - Google Patents

Abstract

PURPOSE:To extend the service life of a lance for stirring a molten metal used for stirring and refining of the molten metal and to reduce the cost ratio thereof by running water into a metallic pipe provided at the center of the lance after the treatment thereby cooling the lance. CONSTITUTION:A lance 3 for stirring a molten normal formed by covering a metallic pipe 7 having a gas passage hole 7' with refractories 8 is immersed in the molten iron 4 and slag 4 in a ladle 1, and gas and flux are blown to generate gas bubbling 6, whereby the molten iron 4 is stirred and refined. Said lance is removed from the ladle 1 after the treatment and water is run in the pipe 7 to cool the lance, by which the difference in thermal expansion between the pipe 7 and the refractories 8 is decreased and the generation of the crack and stripping in the refractories 8 and the bend, etc. of the pipe 7 is prevented. It is preferable to prevent the decrease in the life owing to wetting of the refractories 8 by attaching a water recovering device consisting of a pipeline 10 with a suction cup to the hole 7' in the lower part of the pipe 7 and recovering thoroughly the cooling water fed into the pipe 7 from the upper part thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of using a refractory-coated lance used for stirring and refining molten metal, in which a metal tube in the center of the lance is effectively cooled after processing; The purpose of this is to improve the useful life of the 2-unit.

A refractory-coated lance (hereinafter simply referred to as a lance), in which the outside of a metal tube for gas injection, which is generally called a stirring lance, is coated with a refractory, has a structure roughly shown in Fig. 2. As schematically shown in the figure, it is used to stir and refine the molten metal by immersing it in the molten metal in a refining container such as a ladle and blowing stirring tank gas or refining tank gas and polylux. There is. In Figures 1 and 2, the symbol (1) is a ladle, and (2) is its lid;
(3) is a stirring lance, (4) is molten iron, and (5
) is the slag floating above it, (61 is the stirring lance when gas is blown into it). (7' is the gas passage hole)
(8) is a coated refractory coated on the outside, and (9)
is 7 Ranoji.

Table 1 Table 1 shows the general usage conditions of lances.
Under such conditions, the service life of a lance without any conventional cooling method was 28 times with molten steel, as shown in Table 2.Therefore, there was a problem of high cost ratio. Improvements were requested.

In order to clarify the cause of the short service life of this lance, the inventors investigated the temperature change of the coated refractory, the bending of the metal tube, etc. The results are shown in FIG. The thermal expansion curve shown in the figure was obtained by calculation from the measured temperature, the refractory material, and the coefficient of thermal expansion. As can be seen in the figure, there is a time difference in the extreme temperature values that appear after treatment for the refractory and the metal tube, and the metal tube becomes extremely thick later. Therefore, as shown in the figure, the coefficient of thermal expansion of the metal tube is approximately 15 times larger than that of the refractory, and this, combined with the delay in the temperature curve described above, further increases the difference in expansion. It was learned that this causes physical strain between the refractory and the metal pipe, causing cracks and peeling of the refractory and bending of the metal pipe.

Therefore, based on the above findings, the inventors discovered that cracks in coated refractories,
In order to reduce the difference in thermal expansion between the treated refractory and the metal tube, which is the cause of peeling, it is sufficient to prevent the temperature of the lance from rising after treatment. The present invention was developed by focusing on the method of cooling the lance metal tube by immediately removing it and pouring water into it after the treatment to prevent the temperature of the lance from rising, which had previously been removed from the container and left unattended.

That is, the present invention provides a molten metal stirring lance comprising a metal tube having a gas passage hole and a refractory material surrounding the outer periphery, which is characterized in that when using the molten metal stirring lance, water is allowed to flow through the lance metal tube after the treatment. This is a method of cooling the lance.

Further, a water recovery device is provided in the lower gas passage hole of the lance,
It is characterized by C that collects water injected from the upper part of the metal tube of the lance.

In the present invention, the reason for injecting water directly from the upper part of the metal tube of the lance taken out of the container after the treatment is completed is to use a fluid with high thermal conductivity in order to prevent the temperature of the lance from rising after treatment. This is because water is the most effective fluid.

In addition, in the uninvented method, the water recovery device provided at the lower discharge port of the metal tube of the lance is a pipe with a suction mound at the lower discharge port of the metal tube (7) of the stirring lance (3), as shown in FIG. A pipe is installed, and the filtrate injected from the upper part of the metal pipe through this pipe is collected in a refrigerant, thereby preventing shortening of the service life of the coated refractory (8) due to wetting. It should be noted that all parts in the figure using the same reference numerals as those in FIG. 2 indicate that there is no change from the conventional one.

Table 2 shown below shows a comparison column of examples of the uninvented method and the conventional method in which no cooling method is applied to the lance after treatment, and the lance was used under the same conditions as in Table 1. I was disappointed.

If the lance is cooled by the method of the present invention, as is clear from Table 2, the service life of the lance is significantly extended regardless of the usage conditions, and the cost ratio is accordingly reduced.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a stirring lance in a container, Figure 2 is a schematic structural diagram of the stirring lance, and Figure 3 is a diagram showing the temperature and expansion ratio of metal tubes and refractories over time when used in conventional methods. , Figure 4 is a cross-sectional view of the water recovery device attached to the lower discharge port of the lance metal pipe. 1 Agent: Patent Attorney Mitsu Kimura Term: Souji Sasaki Figure 1 Figure 2 Figure 3 ;:) CDC Iku 80 hours Open (minutes)

Claims (1)

[Scope of Claims] (]) When using a molten metal stirring lance made of a metal tube having gas passage holes and a refractory material surrounding the outer periphery, the lance is characterized by cooling it by flowing water through the lance metal tube after treatment. A cooling method for molten metal stirring lances. (2) The method for cooling a molten metal stirring lance according to claim 1, wherein a water recovery device is provided in the lower gas passage hole of the lance to recover water injected from the upper part of the metal tube of the lance.