JPH0469205B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a top-blown oxygen lance used in a refining furnace such as a hot metal pre-furnace or a converter. This invention relates to a top-blowing oxygen lance that suppresses adhesion, prolongs the time it takes for the amount of metal adhesion to increase, and, on the other hand, shortens the working time for metal removal.

[Prior art] For example, in a dephosphorization operation in a pig iron mixer 8 as shown in FIG. let The top-blown oxygen lance used in the above operation is generally a steel pipe with a multi-tube configuration, with refining oxygen passing through the center and cooling water passing through the outer pipe to cool the lance body. A nozzle tip 5 made of pure copper is detachably attached to the tip of the lance.

However, hot metal adheres to the outer circumferential surface of the lower part of the top-blown oxygen lance main body by spitting, solidifies, and the metal 7 grows in layers. In such a situation, the raising and lowering of the lance may be hindered or the nozzle may become clogged. Therefore, as a measure to prevent metal from adhering to the lower part of the lance,
Measures such as attaching the Cu cover 3 using means such as welding 4 or applying Cr plating to the lower outer circumferential surface of the lance outer layer tube to smooth the surface to prevent or suppress the adhesion of hot metal are taken. There is.

However, when a Cu cover is attached to a top-blown oxygen lance, the effect of preventing metal adhesion is limited to about 50 charges under operating conditions where the amount of oxygen blown per charge is 800 to 2000 Nm ³ /charge. If the amount exceeds that level, metal adhesion will gradually occur,
When the charge exceeds 100, there is a tendency for the amount of metal adhesion to increase significantly. The reason for this is that as the number of charges used increases, unreacted substances in the refining desiliconization agent and dephosphorization agent, mainly iron oxide, are attached to the outer peripheral surface of the lower part of the lance.
This is thought to be because the surface pitting base metal adheres to the Cu cover and forms minute irregularities on the surface of the Cu cover, creating a situation in which the surface pitting base metal easily adheres. The inventors have confirmed that, for example, in the case of an oxygen flow rate of 2000Nm ³ /charge, the thickness of the deposited metal reaches 30mm, and the thickness of the deposited metal reaches 30mm, and the thickness of the deposited metal reaches to the outer peripheral surface of the lower part of the lance.
Almost the same situation was observed even when Cr plating was applied. In other words, if the surface accuracy of the lower outer circumferential surface of the lance or the corresponding area can be maintained smooth at all times, it is thought that adhesion of spitting metal can be prevented. In order to keep it in good condition, the removal work requires considerable effort and time, and the amount of work increases significantly. In particular, there is a problem in that it is extremely difficult to improve surface precision beyond a certain level.

[Problems to be Solved by the Invention] The present invention has been made in view of these circumstances, and provides a top-blown oxygen lance that is less likely to cause base metal adhesion due to spitting in hot metal pretreatment furnaces and converters. The purpose is to

[Means for Solving the Problems] The top-blown oxygen lance of the present invention, which achieves the above object, has the following features: the lower outer peripheral surface of the lance is coated with an amorphous refractory material, and the outer surface is formed with unevenness. It has a gist.

[Function] As a result of various studies to solve the above-mentioned problems, the present inventors have found that instead of forming a coating layer made of a metal material such as a Cu cover or Cr plating on the outer peripheral surface of the lower part of the lance, mortar The present invention was completed based on the knowledge that if the lance is coated with a monolithic refractory material such as lance or caster material, metal adhesion to the lower part of the lance can be significantly suppressed. Although the reason why such excellent effects are obtained in the present invention has not necessarily been clarified, the mortar material and caster material mentioned above can be formed into any shape (the relationship between shape and adhesion). (This will be described later) It is possible to coat the outer peripheral surface of the lower part of the lance with any desired thickness, and since it is made from fine powdered refractory material, its surface precision is high, and it also has excellent surface accuracy between the hot metal and the mortar and caster materials. This is thought to be due to the property of low wettability due to the high interfacial energy between them.

As the monolithic refractory material according to the present invention, mortar material or caster material is typically used, but there are no restrictions on the type of the material. However, monolithic refractories mainly composed of silica and/or alumina are recommended, and other examples include mortar materials and caster materials made of chromium or magnesia. It is desirable that the coating layer made of mortar material or caster material be formed to a thickness that can withstand mechanical damage caused by the impact of the spitting metal, while the impact of the impact of the spitting metal corresponds to the amount of oxygen blown from the lance. Therefore, it is desirable to form the film with a thickness of 1 to 30 mm depending on the amount of oxygen blown from the lance.

On the other hand, it is common to cover the outer peripheral surface of the lower part of the lance with mortar material or caster material to a uniform thickness. It is desirable that the coating thickness be varied regularly or irregularly. In other words, when the outer peripheral surface of the lower part of the lance is coated with the mortar material or caster material of varying thickness, comparing the convex portions and concave portions of the coating layer, the convex portions are less likely to have metal adhesion; Even if gold deposition occurs, it will be concentrated exclusively in the recesses. Since the metal that adheres and accumulates in these recesses is formed independently of each other with the protrusions as boundaries, it is difficult for the amount of accumulated metal to increase due to integration of the adhered metal, and the amount of metal accumulated in the recesses remains constant. When it becomes heavy, the base metal alone or together with the surface layer of the coating material will peel off and fall due to its own weight. In order to more reliably exhibit the effect of preventing metal adhesion due to variations in coating thickness, the variation in coating thickness, that is, the difference between the maximum coating thickness and the minimum coating thickness, should be 5 mm or more. desired.

Further, in the present invention, it is desirable to form the above-mentioned coating layer in an area extending at least 1500 mm upward from the lower end of the lance where metal adhesion is likely to occur.

[Examples] Example 1 As shown in Fig. 1, the outer circumferential surface of the lower part of the main body of the oxygen lance 1 was coated with mortar material 2 to a thickness of 5 mm (assuming a top-blown oxygen usage amount of 1500 Nm ³ charge). Also, about two-thirds of the area from the upper side of the nozzle tip 5 fixed by welding to the lower end of the oxygen lance 1 was similarly coated with the mortar material 2. This oxygen lance 1 was inserted into a pig iron mixing car to carry out oxygen top-blowing refining, and when the amount of metal deposited after the treatment was completed, the amount of deposited metal was significantly reduced compared to the conventional example (without coating). The time required for gold removal was significantly shortened (average metal removal work time: 11 minutes in conventional example, Example 7).
) As a result, we were able to dramatically increase productivity.

On the other hand, in the case of a lance in which a coating layer with unevenness was formed on the outer peripheral surface of the lower part of the lance by changing the coating thickness of the mortar material (difference between maximum coating thickness and minimum coating thickness: 8 mm, average unevenness difference: 5 mm) , the amount of metal deposited was further reduced, and the metal could be removed more easily.

In other words, Figure 3 shows the relationship between metal removal time and oxygen injection amount, and as shown in the figure, coating with mortar material can significantly shorten metal removal time and improve the efficiency of smelting operations. did it.

Example 2 In the same manner as in FIG. 1 (Example 1), the lower outer peripheral surface of the lance 1 was coated with caster material with varying thickness. Approximately two-thirds of the area from above the nozzle tip at the tip of the lance was also covered with caster material.

When this lance 1 was used to carry out oxygen top-blowing refining in a pig iron mixer car, it was possible to obtain the same excellent effect of preventing base metal adhesion as in Example 1 (in the case of covering with mortar material).

[Effects of the Invention] The present invention is constructed as described above, and by using a top-blown oxygen lance whose lower outer peripheral surface of the lance is coated with mortar material, caster material, etc. to an appropriate thickness, adhesion of spitting metal can be prevented. We were able to significantly reduce this.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the example lance, FIG. 2 is an explanatory diagram showing the refining situation in the pig iron mixing car, and FIG. 3 is a graph showing the relationship between the amount of oxygen blown and the metal removal time. 1... Lance, 2... Mortar material, 3... Base metal, 4... Welded part, 5... Nozzle tip, 8...
Mixed iron car.

Claims (1)

[Claims] 1. A top-blown oxygen lance made of a steel pipe that is placed above the molten steel and blows oxygen gas downward, the lower outer peripheral surface of the lance is coated with a monolithic refractory material to form irregularities on the outer surface. A top-blown oxygen lance characterized by: