JPH0670244B2 - Lance pipe for molten metal processing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is for treating molten metal, which is used for blowing various treatment agents into molten metal such as hot metal or molten steel when refining in a ladle, a mixed pig car, etc. Regarding lance pipe.

[Conventional technology]

For the purpose of cleaning the molten metal or its pretreatment,
Gas is used as a carrier from a lance pipe immersed in a molten metal, and a treating agent is blown therein. As the lance pipe used for this blowing, generally, a steel pipe is used as a core material, and its surroundings are covered with castables supported by studs. This lance pipe has resistance to melting damage due to treatment agent, molten metal, slag, etc., resistance to abrasion due to gas bubbling, heat caused by repeated treatment (repeated immersion of lance pipe in molten metal). Resistance to impact is required. Among them, as measures against melting loss and wear, for example, JP-A-59-203777 proposes to use rod-shaped ceramics and steel fibers in order to prevent cracking and peeling due to thermal shock.

Also, the so-called low cement castable, which has high heat resistance from the conventional castable, is changed to an aggregate according to each processing application, and reduces alumina cement while combining various ultrafine powders, has been developed and used, and has achieved results. . For example, a high-alumina low-cement castable is used as the hot metal treatment lance pipe, and a low-cement castable such as fused alumina or sintered alumina is used as the molten steel cleaning lance pipe.

[Problems to be Solved by the Invention]

However, in low-cement castables, as the temperature of the steel pipe used as the core material of the lance pipe rises, the refractory material with a lower expansion coefficient than the steel pipe cracks due to the expansion stress of the core material, causing a problem of reduced durability of the lance pipe. There is.

In terms of crack suppression, positively change the mineral composition by reacting with the materials themselves such as magnesia, sillimanite, kyanite, andalusite, quartz, etc. compounded in castables used for lance pipes, or by reaction with other materials in the compound. The technique of trying to suppress cracks due to the expansion difference by causing residual expansion by performing the above, a technique of suppressing cracks by adding various fibers in the compound, graphite, carbon, SiC, etc. Technology to suppress cracking by adding expansive high thermal conductive material, or technology to suppress cracking of refractory material by arranging heat-insulating irregularly shaped material in the steel pipe of core material (for example, actual development Sho 59-51054 However, the sufficient effect has not been obtained yet.

In the method of arranging the heat insulating irregular shaped material on the outer periphery of the core material, the corrosion resistance is not sufficient when directly contacting the molten metal,
It is necessary to form a two-layer structure in which a dense castable having corrosion resistance is arranged in a portion in contact with the molten metal. This structure has the drawback of being complicated and time-consuming to construct.

Thus, it can be said that the current life of the lance pipe is rate-limited by the crack.

[Means for Solving the Problems]

The present invention has been made to advantageously solve the above-mentioned problems of the prior art, and is characterized in that a castable lining layer containing 1 to 20% by weight of a hollow fire-resistant heat-insulating material is provided on the outer periphery of a steel pipe. A lance pipe for treating molten metal is provided.

[Action]

Steel pipes having gas permeation holes are conventionally known,
A conventional means such as a stud is used to fix the refractory material surrounding the outer circumference. The hollow fireproof heat insulating material according to the present invention,
It is widely used for refractory insulation bricks and heat-resistant castables, and has spherical particles with voids inside. It has fire resistance, high single grain strength, and excellent heat insulation properties. The refractory composition containing the compound has excellent heat insulating properties. Alumina, mullite, aluminosilicate, etc. can be used as the material. The properties are shown in Table 1. From the viewpoint of uniform dispersibility and suppression of deterioration of expression strength, a particle size of 3 mm or less is desirable. The refractory degree should be set according to the treatment temperature of the target molten metal, but it is desirable that it is at least 1200 ° C or higher, and if it is lower than this, the desired heat insulating effect is exhibited with softening and melting. become unable. Furthermore, the blending amount is set variously according to the use conditions (temperature, permeation time, use frequency, lining thickness, vibration state, etc.)
A range of weight% is suitable. If this value is less than 1% by weight, the heat insulating effect is insufficient, and if it exceeds 20% by weight, uniform dispersion becomes difficult and strength development becomes insufficient.
The gas and the treated powder are easily worn due to back attack generated when discharged from the lance pipe, vibration due to bubbling, and the like.

Castable is mullite in the coarse-grained area of refractory aggregate,
High alumina and fused alumina such as bauxite, andalusite, sintered alumina, spinel, zirconia,
Zircon and the like are suitable, but they are not particularly limited. These are excellent in corrosion resistance and thermal shock resistance, and also have relatively low thermal conductivity, so they meet the object of the present invention.

Among the refractory aggregates, if necessary, in the fine powder region forming the matrix, a material having higher purity than that in the coarse particle region and a material that is hard to wet such as SiC, artificial graphite, natural graphite, or carbon black are mixed. These compounds have the effect of suppressing the melt loss of castables.

In addition to the above refractory aggregate, a metal such as metallic silicon, metallic aluminum, metallic zinc, or a carbonitride such as SiC, Si ₃ N ₄ , BN, or B ₄ C is blended, if necessary. Addition of these has effects such as imparting castable oxidation resistance and improving sintering strength.

Further, after firing which is generally carried out, it is represented by quartz, viroferrite, andalusite, magnesia, etc. for imparting a residual expansion property, and stainless fiber etc. for suppressing peeling when a crack occurs. It is effective to mix various fibers. The material can be stainless steel, chrome fiber, or the like. The shape can be straight, waved, twisted, or dock horn with thickened ends. 0.4 ~ 0.5mmφ, length 25 ~ 30
mm, aspect ratio (fiber length / fiber diameter ratio) is 30 or more,
About 60 is suitable. Steel fiber usage is 0.5
-5% by weight is preferred.

More desirably, alumina cement is added. The amount of alumina cement is preferably 1 to 8% by weight from the viewpoint of melting resistance. In addition, if necessary, ultrafine metal oxides such as silica and alumina are added to reduce the amount of alumina cement,
The castable sintering strength can be improved.

Lance pipe covered with castable as above,
By suppressing the temperature rise of the steel pipe of the core material that is normally used by the hollow heat insulating material, it is possible to suppress the thermal stress generated between the steel pipe and the castables with different expansion rates, and the steel pipe is permanently deformed. Elastic limit temperature (500-700
C.) or less, cracks generated inside the castable due to these can be suppressed.

Next, the present invention will be described in detail with reference to Examples.

<Example 1> Table 2 shows the results of the use as a lance pipe material for hot metal pretreatment and the test results in the laboratory. Comparative Example 2 which was extremely excellent in resistance to cracking when castable alone
In the silicon carbide castable of No. 3, although the melting loss was slight, a longitudinal crack (longitudinal direction) that reached the core material after a few charges was generated, and the durability was lowered. On the other hand, in Comparative Example 1, the durability is extended due to the effects of lowering the thermal conductivity and increasing the residual line change rate as compared with Comparative Example 2. In Example 1 in which 5% by weight of the hollow fire-resistant heat insulating material was introduced on the basis of this, a greater effect was obtained.

<Example 2> Table 3 shows the results of use as a lance pipe material for molten steel refining. By introducing 3% by weight of hollow electrofused alumina into the conventionally used electrofused alumina low cement castable (Comparative Example 3), the meltability was less deteriorated, cracks were suppressed, and peeling did not occur. We were able to extend the average usage charge.

[Advantages of the Invention] As described above, according to the present invention, the hollow fire-resistant heat-insulating material is dispersed and mixed in the castable material, so that the molten metal of the core material (generally carbon steel tube) forming the lance pipe is It suppresses the temperature rise, suppresses the thermal stress generated by the expansion difference between the castable covering the core and the elastic limit temperature of the core (generally 500 to 700 for carbon steel pipes).
C.), and it is possible to suppress cracks in the castable due to permanent deformation and suppress cracks that shorten the life of the lance pipe.

Claims (1)

[Claims] 1. A hollow fireproof heat insulating material is provided on the outer circumference of a steel pipe in an amount of 1 to 20.
A lance pipe for treating molten metal, which is provided with a castable lining layer containing wt%.