JPS59145719A - Cooling method of lance for stirring molten metal - Google Patents

Abstract

PURPOSE:To extend the service life of a refractories-coated lance to be used for stirring and refining a molten metal and to reduce the cost ratio thereof by continuing to run gas in said lance even after the treatment thereby cooling the metallic pipe of the lance. CONSTITUTION:A lance 3 for stirring a molten metal which consists of metallic pipe 7 and covering refractories 8 enclosing the outside circumference thereof and is provided with a gas passage hole 7' is inserted into the molten iron 4 and slag 5 in a ladle 1 having a cover 2 and gas is bubbled 6, by which the molten iron 4 is stirred and refined. The gas is kept run for a specified time continuously even after the end of the treatment to cool the lance and prevent the rise of its temp. The difference in thermal expansion between the pipe 7 and the refractories 8 is thus decreased and the generation of crack and stripping in the refractories 8 as well as the bend, etc. of the metallic pipe is prevented. Thus, the service life of the lance 3 is extended.

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 is to improve the useful life of the lance.

A refractory-coated lance (hereinafter simply referred to as a lance), in which the outer periphery of a metal tube for blowing gas is coated with a refractory material and is generally called a stirring lance, has a structure roughly shown in the cylinder shown in Figure 2. As schematically shown in Figure 1, the molten metal is immersed in the molten metal in a refining container such as a ladle, and a stirring gas or a refining gas and flux are blown into the bath to stir and refine the molten metal. is used to do. 1st to 2nd
In the figure, symbol (1) is the ladle, (2) is its lid, (3) is the stirring lance, (4) is the molten iron, and (5) is the slag floating above it. Ashi, (6)
(7) is the metal tube of the stirring lance (3), and (7') is the gas passage through the stirring lance (7). It is a hole, and (8) is a coated refractory coated on the outside.
(9) is a flange.

sb in Table 1, the service life of the lance under such conditions without any conventional cooling method is 27.5 times on average for hot metal and 2.8 times for molten steel, as shown later in Table 2. there were.

As a result, there is a problem in that the cost ratio becomes high, and improvements have been desired.

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 calculated from the measured temperature and the coefficient of thermal expansion of the refractory and metal tube. As can be seen in the figure, there is a time difference in the maximum value of temperature that appears after treatment for the refractory and the metal tube, and the maximum value for the metal tube is delayed.

For this reason, as shown in the figure, the coefficient of thermal expansion of metal pipes is about 1.5 times larger than that of refractories, so this, combined with the delay in the temperature curve mentioned above, makes the difference in expansion even more pronounced. Become.

This causes physical strain between the large object and the metal pipe,
You mentioned that cracks and peeling of refractories and bending of metal pipes occur.

Therefore, based on the above findings, the inventors discovered that cracks in coated refractories
K, which reduces the difference in nasal expansion between the refractory and metal pipe after treatment, which causes peeling, only needs to prevent the temperature of the lance from rising after treatment. Instead of stopping at the end of the process, the gas injection continues even after the process ends to prevent the temperature of the lance from rising.
The present invention was developed by paying attention to the following:

That is, the present invention provides a molten metal stirring lance made of a metal tube having a gas passage hole and a refractory material surrounding the periphery of the molten metal stirring lance. This is a method for cooling metal stirring lances.

In the above-mentioned method of the present invention, the gas that is continuously blown in after the completion of the treatment is for the purpose of cooling the lance.
Although the gas that was previously blown may be used, it is preferable to flow a different gas that is cheaper or has a higher cooling effect, such as N2+ air l002. Any material such as Ar may be used.

Table 2 below shows an example of the method of the present invention and a comparative example of 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. . In addition, Figure 4 shows the temperature inside the lance and thermal expansion of Incense Flavoring I66 in Table 2, and the temperature of the metal tube is kept low compared to the temperature inside the coated refractory. The thermal expansion of the metal tube is approximately equal to that of the coated refractory, and no large tensile stress on the coated refractory due to the metal tube occurs.

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

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the stirring lance in the container, Figure 2 is a schematic structural diagram of the stirring lance, and Figure 6 is a line showing the temperature and expansion ratio of the lance metal tube and refractory over time when used in the conventional method. FIG.
Fig. 3 is a diagram showing the time course of temperature and expansion ratio of metal pipes and refractories. Agent Patent attorney: Rodo San Kimura Souji Sasaki Figure 1 Figure 2 Figure 4 Time (q)

Claims (1)

[Claims] A method for cooling a molten metal stirring lance, which is characterized in that when using a molten metal stirring lance made of a metal tube having a gas passage hole and a refractory surrounding the outer periphery, the lance continues to flow gas for a certain period of time even after processing;