JP3742001B2 - Impeller for desulfurization - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a desulfurization impeller used for hot metal desulfurization treatment in the metallurgical field.
[0002]
[Prior art]
Hot metal desulfurization by the KR method is performed by putting hot metal into a hot metal ladle, immersing the impeller from above, and rotating the impeller at high speed while introducing the desulfurizing agent, so that the desulfurizing agent is suspended in the hot metal and efficiently desulfurized. How to do it. The impeller immersion time varies depending on the processing equipment and processing conditions, but is approximately 10 to 15 minutes.
[0003]
In general, the impeller 1 is manufactured by attaching an anchor 3 on an iron cored bar 2 as shown in FIG. Since the refractory 4 of the impeller 1 is repeatedly heated and cooled, an alumina / silica / silicon carbide-based casting material having excellent heat-resistant spalling properties is often used. Corrosion resistance does not matter so much, and the surface peeling of the refractory 4 on the blade portion 6 rather than the shaft portion 5 usually determines the impeller life.
[0004]
This is because the immersion in the hot metal 7 and the stand-by for cooling are repeated, so that a large thermal shock is applied and peeling occurs particularly in the blade portion 6 having a complicated shape. In order to increase the refractory life, refractories with higher thermal shock resistance have been used.
[Problems to be solved by the invention]
[0005]
However, when the number of treatments per day is large (for example, 50 charges per day), the refractory is peeled off from the shaft core, the core is melted, and the impeller tip is dropped. A high-strength casting material was applied to this phenomenon, but this could not be prevented.
[0006]
The inventors analyzed the cause of the problem that when the number of treatments per day is increased, the refractory is peeled off from the cored bar, the cored bar is melted and the tip of the impeller is dropped off as follows.
(1) When the number of processes per day increases, the interval between one process and the next process decreases, so the cooling time decreases and the core metal temperature rises.
[0007]
(2) Since the surface of the metal core is in contact with the refractory, the temperature of both is the same at the boundary, but the coefficient of thermal expansion of the metal core (iron) is larger than that of the refractory, so This increases the expansion amount, and tensile stress is applied to the refractory.
(3) Even when the daily processing amount is small, the core metal temperature rises to some extent and a similar tensile stress is generated, but it is considered that the stress was absorbed by the refractory because the stress was small.
[0008]
(4) Refractories are resistant to compressive stress but weak to tensile stress. If the core metal temperature rises and the tensile stress received from the core metal and anchor increases, the refractory material cannot withstand and cracks occur. .
(5) The hot metal penetrates into the cracks that have occurred, melts the cored bar and the anchor, and finally peels off the shaft refractory from the cored bar. If the damage is significant, the blades at the tip end fall off.
[0009]
[Means for Solving the Problems]
In view of such problems, the present invention aims to be able to be used stably even under conditions where the number of treatments per day is high , and between a core metal of an impeller for hot metal desulfurization and a refractory around the core metal, In addition, for the desulfurization, a small gap is provided between the anchor attached to the core metal and the refractory around the core metal and the anchor and the refractory to absorb a difference in expansion due to thermal shock . Impeller is provided.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An impeller for desulfurization according to the present invention includes a metal core and an anchor between a core metal of an impeller for hot metal desulfurization and a refractory around the metal core, and between an anchor attached to the metal core and a refractory around the metal core. And a small gap that appropriately absorbs the difference in expansion due to thermal shock of these refractories .
[0011]
By installing a disappearing material 8 that disappears at a high temperature between the core metal 2 and anchor 3 of the impeller 1 and the refractory 4, the core metal 2 and anchor 3 and the core metal 2 and anchor 3 are used before or during use as shown in FIG. Microscopic gaps 9 and 10 are generated between the refractory 4, and the microscopic gaps 9 and 10 absorb the difference in expansion between the metal core 2 and the refractory 4.
[0012]
When the expansion of the core metal 2 in the radial direction is considered, the expansion of the diameter of the refractory 4 is smaller than the expansion of the diameter of the core metal 2. When the difference in expansion between the metal core 2 and the refractory 4 becomes larger than the thickness of the micro gaps 9 and 10, compressive stress is applied to the refractory 4 side.
[0013]
The thickness of the minute gaps 9 and 10 is not necessarily larger than the difference in expansion. This is because although there is a difference in expansion even when the number of treatments per day is small, it does not lead to the drop of the impeller tip, so that a certain amount of expansion difference can be absorbed.
[0014]
Accordingly, when the diameter of the cored bar is a, the thickness ts of the shaft cored bar portion of the shaft 5 of the material that disappears at high temperature is 0.2 × 10 ⁻³ a ≦ ts ≦ 4 × 10 ^{−. 3} a is preferable. If it is smaller than 0.2 × 10 ⁻³ a, the effect of absorbing the expansion is not sufficient. On the other hand, if it is larger than 4 × 10 ⁻³ a, the minute gap 9 is too large, and a gap is formed at a high temperature between the refractory 4 and the cored bar 2 of the shaft portion 5. This is not preferable because the possibility of the occurrence of destruction is increased. More preferably, 0.4 × 10 ⁻³ a ≦ ts ≦ 2 × 10 ⁻³ a.
[0015]
Further, when the diameter of the core bar is a, the thickness ta of the anchor 3 of the material that disappears at a high temperature is preferably 0.6 × 10 ⁻³ a ≦ ta ≦ 8 × 10 ⁻³ a. It is desirable that the gap ta between the anchor 3 and the refractory 4 is larger than the gap ts between the shaft core and the refractory 4. This is because when the axis of the impeller 1 is considered, the axial length is larger than the radial length. This is because the axial expansion difference is mainly transmitted as stress to the refractory 4 through the anchor 3, and the radial expansion difference is mainly transmitted as stress from the core metal 2 directly to the refractory 4.
[0016]
If ta is smaller than 0.6 × 10 ⁻³ a, the effect of absorbing the amount of expansion in the axial direction is not sufficient. On the other hand, if it is larger than 12 × 10 ⁻³ a, the minute gap 10 is too large and a gap is formed between the refractory 4 and the anchor 3 at a high temperature, so that the role of the anchor 3 cannot be achieved. It is not preferable because there is a high possibility that destruction due to the gap occurs due to the above. More preferably, 1.2 × 10 ⁻³ a ≦ ta ≦ 6 × 10 ⁻³ a.
[0017]
On the other hand, the thickness of the blade cored bar at the blade 6 is not directly related to the above-described shaft peeling. However, since the stress due to the difference in thermal expansion is also generated in the blade portion 6, it is more preferable to create a similar gap in order to suppress this. The thickness at this part may be approximately the same as the thickness ta at the anchor 3 part. Even if there is a difference, there is no problem.
[0018]
When the number of treatments per day increases, the reason why significant damage appears only in the shaft portion is not necessarily clear, but it is considered as follows from observation of the impeller in use. That is, remarkable adhesion of the metal is recognized at the root part of the blade part in use. This is considered that the hot metal was cooled and solidified by the refractory. Even if a crack similar to that of the shaft portion occurs, the surface of the refractory has a bare metal, so that the bare metal does not penetrate. As a result, the occurrence of cracks does not directly affect the life of the refractory.
[0019]
However, in the part where the metal part of the blade part is not attached, the same metal infiltration, refractory material peeling, core metal melting, etc. as in the shaft part occur. The effect of suppressing the damage and increasing the service life can be expected.
[0020]
Various organic substances can be used as the disappearing material that disappears at high temperatures between the core metal and the anchor and the refractory. It is not always necessary to completely disappear at a high temperature, and even if some ash, carbon, etc. remain, there is no problem as long as it has no strength and can be easily destroyed when subjected to stress.
[0021]
Specifically, as the form of the material, a sheet-like material such as fiber, tape, cloth, paint, or film can be used. As materials, various plastics, polymers, organic fibers and the like can be used. The installation method is not particularly limited. For example, a means such as winding a tape, applying a paint, or spray coating a film can be taken.
[0022]
After the disappearance material is installed on the cored bar and the anchor, the casting material for the irregular refractory can be poured around it. Although this construction method is not particularly limited, a method in which a mold is installed and cast is generally used. At this time, a rod-shaped vibrator or a formwork vibrator may be used.
[0023]
【Example】
In the desulfurization impeller of the KR method, the damage state and the life were compared between the case where the material 8 disappearing between the core metal 2 and the anchor 3 and the refractory 4 was installed and the case where the material 8 was not installed. The impeller 1 has a shaft portion 5 having a core metal diameter a = 300 mm, a refractory outer diameter of 600 mm, and a length of 1200 mm. Four blades are installed on the lower side, and each blade has a size of 400 × 850 × 600 mm on an outer dimension of the refractory 4 on a core metal 2 of 300 × 500 × 120 mm. An anchor is attached to the cored bar 2.
[0024]
The refractory 4 used was a casting material of alumina / silica / silicon carbide, and the chemical composition was 65% for Al ₂ O ₃ , 25% for SiO ₂ , and 11% for SiC. In the example, plastic was applied to the core metal 2 and the anchor 3 so that ts = 0.3 mm = 1.0 × 10 ⁻³ a and ta = 1.0 mm = 3.3 × 10 ⁻³ a. On top of that, a refractory 4 was poured and applied. On the other hand, in the comparative example, the refractory was poured directly onto the cored bar and the anchor.
[0025]
When the treatment amount per day was 30 to 33 charges, the life was 220 to 250 charges in any case, and the damage state was not significantly changed. On the other hand, when the processing amount per day was 48 to 50 charges, the life of the example was 250 to 265 charges, and the damage that determined the life was a loss of blades. However, in the case of the comparative example, the life decreased to 150 to 165 charge, and the damage that determines the life was dropping of the blade portion due to the loss of the shaft portion. Thus, the superiority of the present invention was confirmed.
[0026]
As described above, it is preferable that the fine voids of the desulfurizing impeller disappear during the desulfurization treatment, in order to save energy, but it can also disappear by heating to a high temperature separately in advance. .
[0027]
【The invention's effect】
As described above, in the present invention, the core between the impeller core for hot metal desulfurization and the refractory around the core, and between the anchor attached to the core and the refractory around the core, Since the micro-gap that absorbs the difference in expansion due to thermal shock between the gold and anchor and these refractories is provided , even when the number of treatments per day is large in desulfurization such as the KR method, It is possible to absorb the difference in expansion from the refractory at the section, to prevent the refractory of the impeller from cracking and to prevent the molten metal from penetrating and dropping off the refractory, and to improve the durability of the impeller.
[0028]
Then, a thin forming material such as a sheet, tape, or paint is disposed between the core bar and anchor of the desulfurizing impeller and the refractory, and disappears at a high temperature , depending on the sheet thickness, tape thickness, and paint film thickness . By providing a minute gap that absorbs the thermal shock expansion difference , a uniform minute gap can be easily provided between the core and anchor of the desulfurizing impeller and the refractory, as described above. An effect can be given.
[0029]
As described above, it is preferable that the fine voids of the desulfurizing impeller disappear during the desulfurization treatment, in order to save energy, but it can also disappear by heating to a high temperature separately in advance. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a state in which a desulfurization impeller is immersed in hot metal,
FIG. 2 is an enlarged cross-sectional view of a metal core, an anchor, and a refractory part according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Impeller 2 ... Core metal 3 ... Anchor 4 ... Refractory 5 ... Shaft part 6 ... Blade | wing part 8 ... Vanishing material 9, 10 ... Micro gap

Claims (2)

Thermal shock of the core metal and the anchor and these refractories between the core metal of the impeller for hot metal desulfurization and the refractory around the core metal, and between the anchor attached to the core metal and the refractory around the core metal An impeller for desulfurization, characterized in that a micro-gap that absorbs the difference in expansion caused by each is provided. A thin forming material such as a sheet, tape, or paint is disposed between the core bar and anchor of the impeller for desulfurization and the refractory around them, and the sheet thickness, tape thickness, paint film disappears at high temperatures. The impeller for desulfurization according to claim 1, wherein a minute gap that absorbs a difference in expansion of thermal shock due to thickness is provided.

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