JPS6089515A - Blowing lance for refining of molten metal - Google Patents

Abstract

PURPOSE:To prevent cracking and stripping of a coating refractory layer owing to oscillation during use of a blowing lance for refining of molten coated with refractories and to extend the service life of the lance by attaching a lumped material consisting of refractories having specific compsn. to the top end of said lance. CONSTITUTION:A coating layer 2 consisting of refractories is formed on the surface of a steel pipe lance 1 to be used in the stage of performing preliminary refining such as desiliconization, dephosphorization, desulfurization or the like of molten iron by blowing powder of carbide, lime, etc. into molten iron to prevent melting of the steel pipe lance by the molten metal and the consequent decrease in the service life thereof. The refractory cooling layer is cracked and stripped by the oscillation in the moltem metal in this case and the coating layer is eroded in short time. a lumped material 3 consisting of Al2O3-SiC-C or MgO-C refractories is attached to the top end of the lance 1 or the part slightly apart from the top end in order to prevent such erosion. The oscillation in the molten iron is thus absorbed and the cracking and stripping of the layer 2 are prevented, by which the decrease in the service life owing to the erosion of the lance is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blowing vessel for molten metal refining, and in particular to improvements in its durability.

During the raw material processing stage of the steelmaking process, silicon in the hot metal from the blast furnace,
In order to remove phosphorus and sulfur, a lance is immersed at an angle in molten metal contained in a molten metal container such as a pig iron mixer, and powders of carbide, lime, etc. are injected with nitrogen gas. . This method is employed, for example, in hot metal desulfurization technology using the ATH method.

This type of lance is generally a steel pipe coated with a refractory material, and has a total length of about 2 to 5 m, and a coating layer thickness of 5 to 20 mm.
Those with a diameter of about 40 to 100 mm are often used. The lance is then placed on an extendable pedestal,
It is inserted and immersed in molten metal, but the angle at the time of insertion is 50~
It is known that the processing efficiency is good when the inclination is 80°.

If the lance breaks during use or a hole develops in a part other than the lance hole, problems such as loss of gas or powder necessary for purification or temporary suspension of operations for replacement may occur.
Lance durability is very important.

Damage to the base/base is thought to occur in the following manner.

That is, the refractory-coated portion of the lance is subject to thermal fluctuations due to repeated use, and during immersion, its dimensions increase due to thermal expansion.
When the process is finished and it is lifted out, it rapidly cools and shrinks. This repeated force heating and cooling causes cracks or thermal distortion to occur inside the refractory, which eventually peels off due to vibration during use, and molten metal penetrates through the cracks, creating holes in the steel pipe and rendering it unusable. state.

In the past, improvements have been made to the material, structure, etc. of the refractory-coated portion of the lance, but nothing satisfactory has been achieved.

The present invention aims to improve the durability of the lance.

The present inventors have focused on the importance of the forces that the car/cell receives during use, particularly vibration acceleration. Since the average density of the lance in use is generally lower than the density of the molten metal, the lance experiences buoyant forces when the lance is inserted into the molten metal. In addition, by blowing gas or powder from the tip of the lance, the molten metal creates a complicated flow within the container, and the metal is subjected to a force due to this flow. Furthermore, the lance is subjected to reaction forces generated when gas or powder is blown into the lance. These forces are caused by the gas flowing in the lance, the wave motion caused by the high speed and high pressure of the powder, the rapid volume expansion of the gas at the moment it is blown into the molten metal, and the gasification response due to thermal decomposition of the powder. The complex waves act on the lance as vibrations. This vibration is not a simple one, but a combination of various frequencies and amplitudes, and the lance that receives the vibration also affects the part of the lance that is immersed in the molten metal, from the top of the molten metal to the lance connection (detachment) part. The parts from the connecting part to the identification end have different dimensions, materials, and surrounding conditions, so the vibration behavior of each part is extremely complicated.

However, the source of these vibrations is predominant at the tip of the immersed part. Therefore, we have considered ways to prevent nozzle punctures or to delay the occurrence of punctures and improve durability by reducing the vibration of this vibration source. And to absorb and reduce vibration force/
They discovered that attaching a fire-resistant lump to the tip of the drum had a remarkable effect, and completed the invention for the drum.

That is, the present invention provides a lance body (1) with a fire-resistant plate a (2), and a fire-resistant coating (2) on the tip of the lance.
According to the present invention, the main body (1) of the lance is made of a steel pipe, and the main body (1) of the lance is made of a steel pipe, and the main body (1) of the lance is made of a steel pipe. The surface is coated with a fire-resistant material (2
) has been applied. A refractory lump (3) is attached to the tip of such a lance for the purpose of absorbing and reducing vibrations generated during immersion in molten metal. If the wall thickness of such a refractory block (3) is too small, sufficient vibration absorption and reduction effects cannot be expected; on the other hand, if it is too thick, there will be a weight burden and economic burden. Although the 7 increases, the effect of 7 does not improve much, so it is about 003 to 10 times the radius of the space, especially 1.
Approximately 0 to 3 times is suitable. In addition, the length of the lump (3) (the length in the axial direction of the lance) does not need to be too thick as long as a certain amount of weight and mechanical strength can be obtained, and it is usually about 115 to 1150 of the lance length. It is selectively determined as appropriate from the range according to its shape, etc. Further, the shape of the lump (3) is not particularly limited as long as it surrounds the coating (2), for example, a cylindrical third shape as shown in FIGS.
In addition to the prismatic cylindrical shape shown in the figure, it may also be spherical, elliptical, etc., and cylindrical shapes are particularly preferred because they are easy to mold and have a good weight balance. Regarding the attachment position of the lump (3) to the lance, as shown in FIG. 1, the tip of the lance is most preferable, but it may be attached slightly to the rear of the tip as shown in FIG. In this case, if the mounting position is too far to the rear of the tip, there is a risk that not only will it have a negative effect on the vibration absorption and reduction effect of the lump (3), but also that the lance on the tip side of the lump (3) will vibrate. Since there is a risk of breaking the lance, care should be taken not to exceed at least 1/3 of the length of the lance, and the range from 115 to the tip is preferable.

The lump (3) is formed from a refractory material that is difficult to be corroded by molten metal, and as such a refractory material, its softening and melting temperature is equal to or higher than the temperature of the molten metal, and it has excellent fire resistance and corrosion resistance. materials, such as high alumina A
n208-8iO-0 series refractory, MgO-0 series refractory,
Plastic refractories, castable refractories, etc. that have heat resistance of 1400° C. or higher are used.

Various methods can be used to attach the lump (3) to the tip of the lance. For example, one or more of the above-mentioned fireproof materials may be mixed with a binder and then pounded onto the tip of the lance. Alternatively, a method of wrapping the mixture, a method of pushing the tip of the paste into the kneaded material filled in the frame and press-fitting it, a method of making a hole in a block-shaped refractory material, inserting it into the tip of the paste, and using mortar etc. You can also use methods such as fixing with. FIG. 3 shows a case in which it is adhesively fixed with mortar (4).

In the present invention, the source of vibration caused by refractory lumps in particular at the tip of the lance is the tip of the immersed part, and in the present invention, the source of vibration, which can be called a source of vibration, is the tip of the lance. In particular, since the lump (3) was installed, this lump (3)
) effectively absorbs and reduces vibrations, preventing cracks in the fire-resistant coating (2) that would otherwise be caused by vibrations, as well as the insertion of molten metal, and preventing holes and breakage in the lance body (1). The period of time can be extended and the durability of the lance can be significantly improved.

This improvement in lance durability is achieved with each use of lance.
Lump (3) It can be further improved by building up and reinforcing it with all refractories.

Table 1 below shows the results of the durability test for the 8 inventors and B and comparative surfaces C and D.

In addition, when conducting this comparative test, the length was 3.5 m and the outer diameter was 34 mm.
The main body is made of carbon steel pipe for high pressure piping (
1) Add 20% by weight of water glass to chamotte powder with a particle size of 3ッ1m or less and knead the refractory material to a thickness of 10m.
After being uniformly coated with m, a lance was manufactured by drying at 200° C. in a drying oven, and this lance was used as a comparative surface. In addition, the lances to which the lump (3) was attached under the conditions listed in the table below were designated as Invention Product A, Invention Product B, and Comparative Surface C. The degree of vibration was measured using a spectrum analyzer. In this method, a vibrator is attached to the top of the lance, and the acceleration of the vibration applied to the vibrator is converted into a ridge signal, which is then displayed on an oscilloscope.

U.S. Photograph the waveform of an oscilloscope and measure the height of the wave on the CRT ) is expressed as a ratio.

As is clear from Table 1, by attaching lumps to the housing, the number of service life increases and the vibration that causes damage changes greatly. In the case of comparative product C, the swing width was small, but it broke from below the mounting position. From this fact, it can be seen that by moving the mounting position of the lump upwards from the nozzle outlet, the vibration behavior changes. In other words, it is thought that the comparative product C, which was installed in the center, broke due to severe vibrations below the installation position. Comparative products have a low service life and are discarded due to holes or breakage in the lance core due to peeling of the covering material, whereas inventive product A
In and B, the vibration is clearly smaller, which leads to an increase in the service life.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention, FIG. 2 is a sectional view taken along the if line in FIG. 1, FIG. 3 is a sectional view showing an example of changing the shape of a lump, and FIG. It is a longitudinal cross-sectional view which shows the example of a change of the attachment position of a lump. In the figure, (1) is the lance body, (2) is the fire-resistant coating,
(3) is a lump, and (4) is mortar. [The above] Agent: Ei Saegusa, Patent Attorney Nippon Figure 1, Engineering Figure 2 L, 1 Figure 4

Claims (1)

[Claims] ■ A lance in which the lance body (1) is coated with a fire-resistant coating (2), and a fire-resistant block (3) is attached to surround the fire-resistant wave a (2) at the tip of the lance. A blowing lance for refining molten metal.