JPH0273912A - Top blowing oxygen lance - Google Patents

Abstract

PURPOSE:To drastically reduce sticking of spitting metal by coating monolithic refractory material on outer circumferential face at lower part of a top blowing oxygen lance. CONSTITUTION:In the top blowing oxygen lance 1 for a converter, etc., the monolithic refractory material 2 is coated on the outer circumferential face at the lower part of the lance body and also the same coating is executed to about 2/3 area part from upper side of a nozzle tip 5 fixed with welding to the lower end part of the lance 1. Then, as the monolithic refractory material 2, mortar material, caster material, etc., is used, it is coated to about 1-30mm thickness at regular or irregular. By this method, the sticking of the metal 7 caused by spitting is restrained and even if the metal 7 is stuck, it is easily removed.

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 operations is generally a steel pipe with a multi-tube configuration, with scouring 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 body due to spitching, and this solidifies into the base metal 7.
grows in layers. Such a situation may prevent the lance from moving up and down, or may cause the nozzle to become clogged. Therefore, as a measure to prevent metal from adhering to the lower part of the lance, a Cu cover 3 is attached to the outer circumferential surface of the lower part of the lance using means such as welding 4, and Cr plating is applied to the outer circumferential surface of the lower part of the lance outer layer tube to smooth the surface. , measures are taken to prevent or suppress the adhesion of hot metal.

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 Nm3/charge. When the number of charges exceeds 50, metal adhesion gradually occurs, and when the number of charges exceeds 100, the amount of metal adhesion tends to increase significantly. The reason for this is that as the number of charges used increases, unreacted substances in the refining membrane St agent and deP agent, mainly iron oxide, adhere to the Cu cover attached to the outer circumferential surface of the lower part of the lance, and the Cu cover surface This is thought to be because the formation of minute irregularities on the surface creates a situation in which the spitting metal tends to adhere. As confirmed by the inventors, for example, an oxygen flow rate of 200
In the case of 0 Nm3/charge, the thickness of the deposited metal is 30I
III11, and almost the same situation was observed even when Cr plating was applied to the outer peripheral surface of the lower part of the lance. In other words, if the surface precision of the lower outer circumferential surface of the lance or the corresponding area can be maintained smooth at all times, it is possible to prevent the adhesion of spitting metal, but if iron oxide, etc. adhering to the lower outer circumferential surface of the lance or the corresponding area are removed every time, the surface In order to maintain good accuracy, 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, is characterized in that the outer peripheral surface of the lower part of the lance is coated with an amorphous refractory material.

[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 finding that metal adhesion to the lower part of the lance can be significantly suppressed by coating it with a monolithic refractory material such as lance or caster material. 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 explained 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.

Mortar material or caster material is typically used as the monolithic refractory material according to the present invention, but there are no restrictions on the type of the material. However, monolithic refractories containing silica and/or alumina as main components are preferably used, and other examples include mortar materials made of chrome or magnesia, or caster materials. 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 collision of the spitting metal.On the other hand, the impact of the collision of the spitching metal depends on the amount of oxygen blown from the lance. It will increase or decrease accordingly, so in the end it will be 1 to 3 depending on the amount of oxygen blown from the lance.
It is desirable to form it to a thickness of 0 mm.

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. That is, when comparing the convex portions and concave portions of the M layer when the outer circumferential surface of the lower part of the lance is coated with the mortar material or caster material with varying thickness, the convex portions are less likely to have metal adhesion; Even if metal adhesion 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 up to at least 1500 ml+ upward from the lower end of the lance where bare metal adhesion is likely to occur.

[Example] Example 1 As shown in Fig. 1, on the outer peripheral surface of the lower part of the main body of the oxygen lance 1,
Mortar material 2 with a thickness of 5 mm (top-blown oxygen usage: 150 O
(assumed to be Nm3 charge).

Similarly, mortar material 2
coated. When this oxygen lance 1 was inserted into a pig iron mixing car to perform oxygen top-blowing refining and 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 metal removal could be significantly shortened (average metal removal work time: 11 minutes in the conventional example, 7 minutes in the example).As a result, productivity could be dramatically increased.

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 adhesion was further reduced, and the metal could be removed more easily.

In other words, the third part shows the relationship between metal removal time and oxygen injection amount.
As shown in the figure, by coating with mortar material, it was possible to significantly shorten the metal removal time and improve the efficiency of the refining operation.

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 in varying thicknesses. In addition, a caster material was also coated on an area approximately % above the nozzle tip at the tip of the lance.

When this lance 1 was used to carry out oxygen top-blowing refining in a pig iron mixing 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, it is possible to reduce the adhesion of sputtering metal. was able to be significantly reduced.

[Brief explanation of the drawing]

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... Pig mixer car No. 1 Figure 2 Oxygen injection amount (Nm3)

Claims (1)

[Claims] A top-blown oxygen lance characterized in that the outer peripheral surface of the lower part of the lance is coated with a monolithic refractory material.