JPS5837941Y2 - Top blowing lance for outside furnace refining - Google Patents

Description

[Detailed explanation of the idea] The present invention is mainly one of the out-of-furnace refining methods.

The purpose of this project is to prolong the life of lance pipes (hereinafter simply referred to as lances) used in the top-blowing method by improving the structure of the nozzle holes in order to extend their lifespan and stabilize their operations.

Recently, construction of skyscrapers and long bridges has become popular, and as a result, even higher quality steel has become required than before, and the operating conditions for various refining furnaces such as converters have become even more demanding.

On the other hand, as a means of producing high-grade steel while maintaining the productivity of the converter, a technique for processing hot metal outside the furnace has been developed and widely implemented. There are two methods, the bottom-blowing method, and the top-blowing method, but the top-blowing method is the most popular for safety reasons.

The lances used in the top-blowing method include thick and long graphite pipes, or steel pipes with the outside covered with monolithic refractories, but in consideration of cost and repairability, The latter is widely used.

By the way, lances are generally used without preheating or with
Since it is rapidly immersed in high-temperature hot metal after being preheated to about ℃, it is rapidly heated from the outside, while the inside is kept at a relatively low temperature by the carrier gas.

Therefore, thermal stress occurs inside and outside the coating layer, causing cracks on the surface, and in some cases, molten metal enters the coating layer, causing the core pipe to be fused and desulfurization work to be interrupted.

In addition, after desulfurization treatment, the lance is immediately removed from the molten metal, but during the process, the hot metal may flow back into the nozzle.
Alternatively, immediately after pulling up, the hot metal adhering to the coating layer flows downward and enters the nozzle, clogging it, and in many cases, it is discarded after being used only 3 or 4 times.

To solve this problem, an outer steel pipe whose outer surface is lined with a monolithic refractory is lined with an inner steel pipe to form a two-layer pipe with an annular passage, and the nozzle radiation angle (aperture angle) is set at the lower end of the pipe.
Injection lance with individualized porous brick annular nozzles of 0 to 30 degrees (Jikkosho 53 = 4)
7044), and the above-mentioned fusing trouble was somewhat solved.

However, it is difficult to mount the annular nozzle firmly so that it can be used for a long period of time, and the monolithic refractory lining around the annular nozzle may be damaged by the air bubbles ejected from the annular nozzle, resulting in its being discarded. Many, and in addition, rapidly rising carrier gas bubbles,
In some cases, they were scrapped due to local damage caused by hitting the refractory lining above the annular nozzle.

As a result of various improvements to eliminate these drawbacks, the inventors of the present invention have developed a lance that has a long service life and can perform stable desulfurization work by making the nozzle hole have a forced cooling structure with an annular gap. was completed.

Hereinafter, the present invention will be explained in detail with reference to the drawings showing embodiments.

For example, in Fig. 3, 1 is an outer steel tube with its tip (lower end) sealed, 2 is an inner tube with a bottom, and 3 is a double tube with a length of 3 to 4 m. A circular core metal pipe, 4 a mounting flange provided at the upper end of the inner pipe 2, 5 a gas introduction pipe connected to the upper side of the outer pipe 1, 6
is a well-known V-shaped locking hardware welded to the surface of the outer tube 1.

Reference numeral 7 denotes a coating layer with a thickness of 50 to 7 Qmm, in which two (multiple) layers of well-known heat-insulating clay castable and highly corrosion-resistant high alumina castable are constructed on the outer surface of the outer tube 1 by a conventional method. The core metal pipe 3 is completely heat-insulated and protected.

Reference numeral 8 denotes an outer branch pipe, in which a plurality of heat-resistant steel pipes whose cross-sectional shapes are generally circular, oval, or (poly)gonal are welded horizontally or slightly downward near the tip of the long outer pipe 1. There is.

Reference numeral 9 denotes an inner branch pipe, which is a heat-resistant steel pipe with a cross-sectional shape similar to that described above and whose outer diameter is slightly smaller than the inner diameter of the outer branch pipe 8.
A plurality of pieces are welded horizontally near the tip of the inner tube 2 (at a position corresponding to the outer branch tube 8), and the inner branch tube 9 is welded by a conventional method.
are firmly inserted into the outer branch tube 8 in a concentric or coaxial manner.

10 is an annular gap, and a passage having a width of 2 to 5 mm is provided on the outside of the inner branch pipe 9 through which the cooling gas 11 passes.

Note that if the gap size is less than 2 mm, the cooling effect will be insufficient, and if it is more than 5 mm, the bubbles 12 of the rising cooling gas 11 will become too large, and there is a risk that the melt 13 will scatter, so the above range is required. Delicious.

Further, the spout holes 14 are formed by embedding the entire outer circumferential surface of the outer branch pipe 8 with the coating layer 7 as described above using a conventional method.

Next, the effects of the lance of the present invention will be explained with reference to an embodiment in a ladle.

First, the lance is attached to the elevating mechanism (both not shown) of the desulfurization equipment, and then the hose and cooling gas 11 (both nitrogen or argon) hose to the mounting flange 4 and gas inlet pipe 5, respectively.
Connect to.

Next, while slightly ejecting only both gases from the ejection hole 14 (inner branch pipe 9 and annular gap 10), the metal is immersed to a predetermined depth in the hot metal 13 at about 1500°C stored in the ladle,
Desulfurization treatment was carried out by blowing a required amount of desulfurization agent together with carrier gas 15 from the submerged branch pipe 9 for 20 minutes.

In the lance of the present invention, a carrier gas 15 and a cooling gas 1 are passed through the inner branch pipe 9 and the annular gap 10, respectively.
1 is blown into the moving hot metal 13, so the hot metal 13 is removed from the vicinity of the tip of the spout hole 14.

Therefore, the outer branch pipe 8 and the inner branch pipe 9 are mostly filled with hot metal 1.
Since the inner branch tube 9 does not come into contact with the inner branch tube 3, its tip is not damaged and is kept in its original shape for a long period of time.In particular, the inner branch tube 9 is cooled from both sides by these gases, thereby further preventing thermal damage.

Further, the carrier gas 15 is not accelerated while being surrounded by the cooling gas 11 ejected from the annular gap 10 in a cylindrical shape, and is ejected quite far into the hot metal 13; As mentioned above, since there is almost no damage, the ejection direction is always maintained in a constant horizontal or downward direction for a long period of time (many times).

Therefore, the bubbles 16 of the carrier gas 15 containing the desulfurization agent
Since the gas hardly hits the coating layer 7 above the ejection hole 14, local damage unlike the conventional case does not occur.

In this way, it is possible to prevent damage to the nozzle 14, which has conventionally been the main cause of short life, and at the same time, as a secondary effect, damage to the coating layer 7 can also be prevented.

Furthermore, the reaction of the desulfurizing agent is promoted by the stirring action of the bubbles 12 of the cooling gas 11, so if the jetting pressure or jetting amount of the cooling gas 11 and the carrier gas 15 is appropriately adjusted by a conventional method, the treatment can be carried out. The time is shortened, the desulfurization rate is improved, and the hot metal 13 and the like will hardly enter the ejection hole 14 after the desulfurization treatment and solidify and block it as described above.

As a precaution, the slag line section of the lance was slightly melted and damaged after five desulfurization treatments, and its use was discontinued from a safety standpoint. When the conventional lance shown in Figure 2a was disassembled and investigated, the above effects were confirmed.

As described in detail above, the lance of the present invention has a simple structure with a nozzle hole having an annular gap, but it is mainly used to prevent damage to the nozzle hole and blockage after use, and secondarily to prevent the nozzle from being damaged and blocked after use. It also prevents local damage to the layer and extends its service life from 5 to 50%.
This can be extended to six times (compared to three to four times in the past), and stable operation can be achieved by reducing replacement or repair work.

In addition, it is useful for steelmaking operations, such as improving productivity and desulfurization rate and producing high-quality steel.

Although the present invention has been explained based on an example in the desulfurization treatment process of hot metal, the present invention is not limited to this in any way, and can be widely applied to outside furnace refining of hot metal (dephosphorization, desiliconization), etc. It is applicable.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a conventional lance, FIG. 2 is a schematic vertical cross-sectional view showing the injection hole of the same conventional lance, and FIG. 3 is a schematic vertical cross-sectional view showing the usage of the lance of the present invention. In the figure, 1... outer tube, 2... inner tube,
7...Coating layer, 8...External branch pipe, 9...
...Inner branch pipe, 10...Annular gap, 14...
...It is a blowhole.

Claims (1)

[Scope of utility model registration request] An outer tube 1 with a fire-resistant coating layer 7 on its outer surface and an inner tube 2
In a top-blowing lance for out-of-furnace refining that is equipped with an internal tube, an inner branch pipe 9 connected to the bottom of the inner tube 2 is inserted into an outer branch tube 8 connected to the bottom of the outer tube 1 near the tip. A top blowing lance for out-of-furnace refining, characterized in that an ejection hole 14 having an annular gap 10 is formed at the top of the lance.