JPS6347990B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is capable of accurately estimating the remaining thickness of a work brick in a molten metal storage ladle (hereinafter simply referred to as a ladle), thereby reducing the number of processing times until the ladle is lowered. The present invention relates to a method for estimating the residual thickness of work bricks that can extend the life span of the workpiece brick (substantially the life of the pot). The above-mentioned "processing" is used in a wide range of meanings, such as molten metal pretreatment, refining, degassing, inclusion form control, and temporary storage. Processing furnace, converter,
This includes VOD furnaces, AOD furnaces, RH or DH degassing vessels, pig iron mixers, ladles, charging ladle, etc. [Prior art] The method for measuring the remaining thickness of the work brick in a pot is as follows:
A method using a far-infrared laser is widely used.
This is done by first determining the inner diameter D _p of the pot immediately after installing the work brick (when it is new) using a far-infrared laser, and then determining the inner diameter D _o after using it a number of times (referred to as n times) using a far-infrared laser. The above D _p
Based on the difference between D o and D _o , the wear progress of the work brick is determined and the remaining thickness is calculated. [Problem to be solved by the invention] In order to accurately determine the inner diameter D _o using a far-infrared laser, it is necessary to reduce air fluctuations (hygiene phenomenon) by lowering the temperature of the pot. It is. However, since it takes a considerable amount of time to lower the temperature of the pot, when measuring using a far-infrared laser device, it interferes with the continuity of pot operation, has a serious negative impact on productivity, and is very time consuming. If a pot that has been heated to a high temperature is once cooled down, even if it is determined that the remaining thickness is sufficient and the pot has not yet reached the end of its life, a huge heat source is required to reheat the pot. From an economic point of view, it will no longer be profitable. Due to this situation, it is tempting to avoid measuring the residual thickness using far-infrared light if possible, and the timing of measurement is often postponed, and it is difficult to notice that the residual thickness is decreasing. If there is a delay and it is very dangerous, or if you measure the remaining thickness and find that there is not much remaining thickness, it is better to replace it with a new fireproof wall than to reheat and try again. There was a problem in that the pot was judged to have reached the end of its lifespan even though it had not yet reached its end, thereby shortening its effective lifespan. Therefore, it has become desirable to develop a method that enables accurate measurement without interfering with pot operation, especially without using the far-infrared laser method.
As the fireproof wall wears out, the volume inside the pot expands, so it is possible to visually estimate the level of drop in the molten metal level and use this to estimate the approximate remaining thickness. Since the amount of molten metal poured each time is not constant, it is easy to understand that it is wrong to immediately link the cause of the drop in the molten metal level to the wear and tear of the fireproof walls. The present invention has been developed in consideration of these circumstances, and it is possible to accurately estimate the remaining thickness of work bricks in a pot even by visual inspection, thereby substantially increasing the number of processing steps until the pot is lowered. The aim is to provide a method that allows for [Means for Solving the Problems] The method for estimating the residual thickness of work bricks according to the present invention is a method for estimating the residual thickness of work bricks in a molten metal storage ladle. The gist lies in estimating the remaining thickness of the work brick by providing a marker brick that has a lower erosion rate than the work brick and visually measuring the amount of protrusion of the marker brick from the work brick. be. [Function] In the present invention, as shown in FIG. 1, a marker brick 2 having a lower erosion rate than the work bricks 1 is provided in the middle of the arrangement of the work bricks 1. As mentioned above, the erosion rate of the marker brick 2 is slower than that of the work brick 1, so for example, as the number of refining operations increases, the work brick 1 wears out preferentially, and the marker brick 2 becomes the work brick. It will be in a state like that shown in Figure 2, protruding from 1. Note that 3 is a freeboard, 4 is a slag line, 5 is a bottom brick, and 6 is an iron skin. The method of the present invention is characterized in that the residual thickness of the workpiece brick is estimated by visually measuring the amount of protrusion ΔY. However, in making the above estimation, it is necessary to accurately understand the difference in wear behavior between the marker brick and the work brick. In other words, if the marker bricks do not wear out substantially, the above ΔY directly represents the amount of wear on the work bricks, but if it is unavoidable that the marker bricks also wear out, the unit charge number ( For example, if you know the average amount of wear on the marker bricks per 5 or 10 times, and add that amount to ΔY, you will get the amount of wear on the work bricks. Furthermore, if the difference in behavior of the wear amount between the marker brick and the work brick is known in advance, the amount of wear on the work brick can be known by correcting ΔY based on the difference in behavior. In this way, the remaining thickness of the work brick is estimated from the amount of wear on the work brick. By making it possible to accurately estimate the residual thickness in this way, the following advantages are exhibited. Conventionally, even if the pot is expected to reach the end of its lifespan, it has been used to lower the pot for safety reasons, that is, by allowing a considerable amount of leeway in the remaining thickness. However, when it becomes possible to accurately estimate the residual thickness as in the present invention, there is no need to allow for a margin in the residual thickness, and the ladle can be used close to the limit of the residual thickness, resulting in a reduction in the number of times of refining before the pan is lowered. can be increased. There are no particular restrictions on the mounting position or number of the marker bricks, but the following formats may be used. (1) As shown in FIG. 3a, the marker bricks 2 are arranged continuously along the circumferential direction of the pot 7. There is no particular restriction on the height at which the marker bricks 2 are provided. However, it is preferable to provide it at the top because it is easier to see visually. (2) Arrange marker bricks 2 and work bricks 1 alternately as shown in Figure 3b. However, since these bricks have different coefficients of thermal expansion, so-called joint openings may occur during smelting, and in some cases, bricks may fall out. Therefore, care must be taken when arranging them alternately as shown in FIG. 3b. (3) Two marker bricks 2 may be arranged so as to face each other as shown in FIG. 3c, and in this case, the number of marker bricks 2 can be reduced. (4) Provided at only one location as shown in Figure 3d. In this way, even one location is sufficient as a guide for visual measurement. (5) Although the above is a case in which the height of the marker bricks 2 is constant, it is not excluded that the heights may be variously changed to carry out the arrangement of the above (1) to (4). By the way, there are no particular restrictions on the materials of the marker brick 2 and work brick 1, but as marker bricks
Examples of MgO-C and work bricks include Al ₂ O ₃ -C. As described above, the method of the present invention introduces a marker brick as a guide for determining when it is time to lower the pot, and by visually observing the protruding length of the marker brick, it achieves accurate determination of when it is time to lower the pot. It is. An example of how to determine the amount of protrusion of the marker brick, which is a guideline for determining when to take down the pot, and how to determine when to take down the pot is as follows. (1) First, determine the erosion rates of the work brick and marker brick under the desired refining conditions (refining temperature, amount of refining, and refining time). Here, the values are: work brick: a ₁ to a ₂ mm/time, sign brick: b ₁
~b ₂ mm/times. Note that a ₁ and b ₁ are values considered to be minimum, and a ₂ and b ₂ are values considered to be maximum. However, a ₂ > a ₁ > b ₂ > b ₁ . (2) If the thickness of the work brick and marker brick before refining is A and B (however, B≧A), then the residual thickness y ₁ of the work brick and the residual thickness y ₂ of the marker brick are respectively expressed by the following formulas. . _y1 =A-( _a1 - _a2 )n... _y2 =B-( _b1 - _b2 )n...However, n indicates the number of times of refining. Incidentally, FIG. 4 illustrates these relationships. (3) Here, the residual thickness difference ΔY between the work brick and the marker brick
[ΔY= _y2 − _y1 =(B−A)+{( _a1 ~ _a2 )−( _b1 ~
b ₂ )}n], this is [(B-A)+(a ₂ -b ₁ )n] ~[(B-A)+(a ₁ -b ₂ )n]... … was found to be a value within the range (because
The difference between y ₂ = B-b ₁ n and y ₁ = A-a ₂ n is the minimum value, y ₂
= B-b ₂ n and y ₁ = A-a ₁ n because the difference is the maximum value). (4) By the way, the remaining thickness of the work brick for the pot is approximately Cmm.
It is determined that the pot has reached the end of its lifespan and needs to be removed. The above C is a value known from experience. (5) Let this C be y ₁ = A-a ₂ n and y ₁ = A-a ₁ n _.
Substituting into , n=A-C/a ₂ and n=A-C/a ₁ are obtained, respectively. Then, by substituting these n into the above formula, we get
As the range of residual thickness difference ΔY: [(B-A)+a ₂ -b ₁ /a ₂ (A-C)] ~ [(B-A)+a ₁ -b ₂ /a ₁ (A-C)] ... is obtained. (6) That is, when the residual thickness difference ΔY falls within the above range, the work brick residual thickness becomes Cmm. Therefore, the operator can decide that it is okay to continue the refining work until the visually measured residual thickness difference ΔY falls within the above range. The method of the present invention will be specifically explained below by giving examples, but the method of the present invention is not limited to these examples and may be modified as appropriate in accordance with the purpose of the preceding and following descriptions. can. [Example] Free boat: Alumina brick, slag line:
MgO-C, work brick: Al ₂ O ₃ -C, marker brick:
The operation was carried out with MgO-C, bottom brick: alumina brick, thickness of work brick before use: 80 mm, and thickness of marker brick before use: 90 mm. From past operational results, it has been found that the erosion rates of Al ₂ O ₃ and MgO-C are 0.4 to 0.6 mm/time and 0.1 to 0.3 mm/time, respectively. In the above operation, if the protrusion amount is 30 to 35 mm (pot bricks may fall off when the remaining thickness is less than 40 to 50 mm. This determines the usage limit of the bricks. MgO-C
When the difference in protrusion between the Al ₂ O ₃ -C brick and the Al 2 O 3 -C brick becomes 30 to 35 mm, the residual thickness of the Al ₂ O ₃ -C becomes 50 mm. A pot that was said to be able to be used only once,
It can be safely used up to about 75 times, and the number of times it can be refined before being removed from the pot has been increased. An example of the results is shown in Table 1.

[Table] [Effects of the Invention] Since the present invention is configured as described above, it is possible to accurately estimate the remaining thickness of the workpiece brick in the pot even by visual inspection, and thereby the processing up to the pot lowering can be easily estimated. We were able to provide a method for estimating the residual thickness of work bricks that can be repeated many times.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view of a ladle used in carrying out the method of the present invention, FIG. FIG. 4 is a diagram showing the arrangement of marked bricks, and FIG. 4 is a diagram showing the relationship between the remaining thickness and the number of refining operations. 1... Work brick, 2... Marker brick, ΔY...
Protrusion amount.

Claims (1)

[Claims] 1 A method for estimating the remaining thickness of work bricks in a molten metal storage pot, in which a marker brick with a lower melting rate than the work bricks is provided in the middle of the arrangement of the work bricks, and the amount of protrusion of the marker brick from the work bricks is calculated. A method for estimating the residual thickness of a work brick in a molten metal storage pot, the method comprising estimating the residual thickness of the work brick by visually measuring the residual thickness of the work brick.