JP3519682B2 - Roll cooling method in continuous casting machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention efficiently cools a roll supporting a slab in a continuous casting machine to prevent scale from adhering to the roll surface and to keep the roll surface at an appropriate temperature or lower. Prevent surface deterioration,
The present invention relates to a useful method for cooling a roll for the purpose of extending the roll life.

[0002]

2. Description of the Related Art Molten metal poured into a mold of a continuous casting machine is cooled by the mold to form a certain solidified shell, which is continuously supported by a continuous casting roll such as a pinch roll or a guide roll. Will be pulled out. Here, the continuous casting roll supports a high-temperature slab that reaches 700 to 1500 ° C. while rotating, and thus continuously receives a large heat load.

When the roll in such a severe condition is used repeatedly, not only the surface of the roll is cracked or the surface is oxidatively worn to hinder the transportation of the slab, but also the slab is liable to be damaged. Since bulging causes defects such as internal cracks, replacement and repair are required at appropriate times. However, repeated replacement or repair of rolls is a factor that reduces the productivity of the continuous casting machine, and therefore it is a problem to extend the roll life.

As a method for solving such problems, it has been customary to cool a roll with a cooling medium such as water, and the following methods have been proposed.

In Japanese Patent Laid-Open No. 4-279260, in order to cool the roll by spraying water on it, the roll and the slab are cooled at the same time in order to minimize the facility scale, reduce the maintenance man-hours, and efficiently perform at low cost. Nozzles have been proposed.

However, in the nozzle used in the above method, since the nozzle for cooling the slab and the nozzle for cooling the roll are integrated, only the roll cannot be cooled. Therefore, if such a nozzle is used at a place where cooling of the slab is unnecessary, the surface of the slab is cooled more than necessary, causing surface defects such as cracks. Also, if the nozzles for roll cooling and slab cooling are combined, it becomes difficult to adjust the water amount balance of the water sprayed from each nozzle, so cool both the roll and slab surfaces uniformly and accurately. Is difficult.

In Japanese Patent Laid-Open No. 9-253810, a cooling water channel in the form of a closed flow channel is provided axially symmetrically in the vicinity of the surface layer of the roll core, and the roll is extended from the inside by cooling the roll to suppress temperature rise. I am trying to However, with such internal cooling alone, it is difficult to immediately cool the surface of the roll locally heated by the high temperature slab to bring it into an appropriate temperature range. Further, since the scale attached to the roll cannot be removed, the attached scale may grow and push the surface of the slab.

[0008] Japanese Patent Laid-Open No. 11-26713 proposes a method of bringing a water retaining material into contact with the roll and cooling the roll with cooling water oozing out from the water retaining material. However, the cooling effect is small only with the cooling water that oozes out from the water retaining material, and it is hard to say that sufficient roll cooling is performed. Further, as the number of rolls used increases, the roll surface is worn and the gap between the roll and the water retaining material is widened, so that the cooling effect of the water retaining material is weakened and the wear of the roll may be accelerated.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to efficiently cool a roll in a continuous casting machine to dramatically extend the roll life and replace it. An object of the present invention is to provide a useful roll cooling method that can reduce the frequency of repairs and the like to improve productivity in a continuous casting machine and reduce the cost required for roll maintenance.

[0010]

According to the roll cooling method of the present invention, a mist nozzle or a spray nozzle dedicated to roll cooling is installed on a roll supporting a slab in a vertical bending type or bending type continuous casting machine, From the nozzle, water of 0.3 L per roll (indicating "liter"; the same applies below) / min was sprayed onto the roll to bring the surface temperature of the roll to 600 ° C. or lower, and to prevent bending of the bent portion when continuous casting was stopped. The idea is to stop spraying water on the rolls.

Further, it is desirable to control the amount of water sprayed onto the roll (hereinafter sometimes referred to as "roll cooling water amount") so as to satisfy the following formula (1) according to the casting speed. Q ≧ 5.0 Vc−3.0 (1) [however, Q: roll cooling water amount (L / min), Vc; casting speed (m / min)]

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Under the circumstances described above, the present inventors have realized a roll cooling method capable of efficiently cooling a roll in a continuous casting machine and dramatically extending its life. Aimed at the research, As a result, if the amount of water sprayed in the method of cooling the roll from the outside by spraying water on the roll is regulated, even if the cooling form of the roll is not specifically regulated, the temperature at which the abrasion of the roll surface is significantly suppressed is reached. It was found that the roll surface temperature can be lowered and the roll life can be dramatically extended.

FIG. 1 is a graph showing the relationship between the roll surface temperature and the roll wear amount index. The roll wear amount index is
It was determined by measuring the diameter of the central part of the roll when the roll kept at a predetermined temperature was used for 6 months. It can be seen from FIG. 1 that when the roll surface temperature exceeds 600 ° C., the crystal grain size of the roll surface structure becomes large and the hardness of the surface is lowered, resulting in a marked change in the material and the roll surface being significantly worn. If the rolls are significantly worn in this way, there arises a problem that the slab is not smoothly conveyed in the continuous casting machine.

Therefore, the surface temperature of the roll is preferably suppressed to 600 ° C. or lower, more preferably 300 ° C. or lower. Even if the surface temperature of the roll is too low, the sprayed water does not evaporate and is transmitted to the roll and applied to the slab, which easily causes surface defects such as cracks on the slab surface. It is preferably 100 ° C. or higher.

In the experiment of FIG. 1 described above, the material of the roll surface is stainless steel, but the present invention does not specify the material of the roll surface, and the material of the roll surface is stainless steel. Besides the material, it can be applied to, for example, Inconel. Further, the type of steel to be cast is not limited, and the present invention can be applied during casting of low alloy steel, machine structural steel, Mn steel, free cutting steel, bearing steel, spring steel and the like.

FIG. 2 shows the relationship between the amount of roll cooling water and the roll surface temperature. From this graph, as described above, it is possible to reduce the amount of wear on the roll surface by keeping the roll surface temperature below 600 ° C. , 0.3 L / m per roll
It turns out that it is necessary to spray more than in water on the roll. The preferable amount of roll cooling water is 2 L / min or more, but it is more preferable to appropriately adjust the amount according to the installation location of the roll. Fig. 3 shows the arrangement of rolls in a continuous casting machine (schematic diagram). The influence of cooling water for slab and the heat load from the slab differ depending on the installation location of the roll. The amount of water is also different.
Therefore, for example, in the roll unit 1 of FIG.
L / min or more, roll part 2 0.3 L / min or more, roll part 3 2 L / min or more, roll part 4 2 L / min or more, roll part 5 2 L / min or more,
2 L / min or more in the roll section 6, 2 L / min in the roll section 7
/ Min or more is more preferable.

If the amount of cooling water for the roll is too large, water may be applied to the slab and surface defects such as cracks may occur on the surface of the slab. Therefore, the amount of cooling water per roll is 1
It is preferable to suppress it to 0 L / min or less, and more preferably 5 L / min or less in the roll unit 1, 4 L / min or less in the roll unit 2 and 3 L / min in the roll unit 3 depending on the installation location of the roll shown in FIG. less than min, 3L in roll section 4
/ Min or less, 3 L / min or less in the roll unit 5, 3 L / min or less in the roll unit 6, and 3 L / min or less in the roll unit 7.

The above-mentioned mist nozzle or spray nozzle is exclusively for roll cooling, and the roll cooling method of the present invention is a method of spraying water from the nozzle onto the roll to cool only the roll from the outside. Not something to do. When the roll cooling water is applied to the slab, surface defects such as cracks will occur on the surface of the slab, so it is desirable that the water sprayed on the roll should not reach the slab as much as possible.

Further, in the method of the present invention, a mist nozzle or a spray nozzle is used for spraying water on the roll. However, when the mist nozzle is used, fine water droplets can be dispersed uniformly to cool the roll surface uniformly. Because you can
It is preferable to use a mist nozzle. The amount of cooling water can be controlled by providing a flow control valve.

FIG. 4 shows the relationship between the casting speed and the roll surface temperature depending on whether or not the roll is cooled. The roll is cooled by spraying 2 L / min of water per roll. As shown in FIG. 4, by performing roll cooling, the roll surface temperature can be significantly reduced regardless of the casting speed.

Further, FIG. 4 shows that when the amount of roll cooling water is constant, the roll surface temperature rises as the casting speed increases. That is, the roll surface temperature is easily influenced by the casting speed. Therefore, in the present invention, in order to keep the roll surface temperature below a certain temperature, it is preferable to control the amount of roll cooling water according to the casting speed. In this way, by increasing or decreasing the amount of roll cooling water according to the casting speed, the roll surface temperature can be kept at 600 ° C or less to extend the roll life regardless of the casting speed, and the roll is cooled more than necessary. It is possible to prevent the sprayed water from dropping on the slab without evaporating and overcooling the slab to cause defects such as cracks on the surface of the slab.

FIG. 5 shows the relationship between the casting speed and the slab defect occurrence rate according to whether or not the roll cooling water amount is controlled. The case where the roll cooling water amount is kept constant at 8 L / min regardless of the casting speed, The amount of roll cooling water is controlled according to the casting speed, that is, the casting speed is 0.70, 0.85, 0.90,
For 1.0 and 1.05 m / min, the amount of water sprayed onto the roll was 1, 1.5, 2.0, 2.5, and 3.
This is a comparison of the slab defect occurrence rates at 0 L / min.

From FIG. 5, by controlling the amount of roll cooling water according to the casting speed, the occurrence rate of slab defects is remarkably reduced, and no slab defects are found at a casting speed of 0.85 to 1.05 m / min. You can see that it has become.

As a method of adjusting the amount of cooling water according to the casting speed, it is effective to satisfy the following formula (1), for example. Q ≧ 5.0 Vc−3.0 (1) [however, Q: roll cooling water amount (L / min), Vc; casting speed (m / min)]

By the way, during continuous casting, in addition to connecting different steel types, the continuous casting machine may be forced to stop completely, such as when replacing the tundish nozzle or the tundish. In such a case, if the roll is continuously cooled, the temperature of the roll cooling portion drops extremely because the roll itself is stopped, the cooling water does not evaporate and drops into a slab,
The slab is partially cooled and surface defects such as cracks occur.

Therefore, when continuous casting is stopped in the vertical bending die or the bending die continuous casting machine, the bending portion (roll portion 3, roll portion 4, roll portion 5, roll portion 6, and roll portion 7 in FIG. It is also necessary to stop the spraying of the rolls) to the roll at the same time.

Incidentally, the rolls other than the above, that is, the rolls of the roll portion 1 and the roll portion 2 in FIG. 3 described above are in the vertical portion, and even when the cooling water sprayed on the roll surface does not evaporate and becomes a water drop, casting is performed. Since there is no risk of it being caught on one side, roll cooling may be continued when continuous casting is stopped.

Further, when the casting is restarted after the continuous casting is stopped, it is preferable to restart the roll cooling at the same time.
FIG. 6 shows the surface temperature of the roll when the continuous casting and the roll cooling are restarted after the casting is stopped by rotating the roll 9 using the radiation type temperature measuring device 8 installed on the upper part of the roll as shown in FIG. However, the height of the peak in FIG. 6 represents the height of the roll surface temperature. The high temperature peak in FIG. 6 shows the surface temperature of the roll portion 10 that was in contact with the slab when the casting was stopped, and the first measurement result and the second measurement of the roll portion 10 in order from the left end peak. The results are shown.

From FIG. 6, immediately after restarting the roll cooling,
The part that was in contact with the slab is hot regardless of the presence or absence of roll cooling, but by restarting the roll cooling, the part where the roll surface temperature is high is immediately cooled to below the predetermined temperature and the surface temperature becomes uniform. Become. On the other hand, when the roll is not cooled, the part with a high roll surface temperature remains held for a long time, and the roll surface structure of only this high temperature part changes and wears, resulting in uneven wear of the roll. It causes inconvenience such as

[0030]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and may be appropriately applied within a range compatible with the gist of the preceding and the following. Modifications can be made and implemented, and all of them are included in the technical scope of the present invention.

<Example> In casting of a steel cast piece 13 such as low alloy steel, machine structural steel, Mn steel, free cutting steel, bearing steel, or spring steel in a continuous casting machine, as shown in FIG. Using the mist nozzle 11, water 12 in the form of mist was sprayed onto the roll 9 from the opposite direction of the slab 13 for cooling. Use a 13Cr stainless steel surface material as the roll,
The amount of cooling water per roll is as shown in FIG.
0.4 L / min, roll part 2 0.5 L / min,
Roll part 3 is 2 L / min, roll part 4 is 2 L / mi
n, 2 L / min for roll unit 5, 2 L / m for roll unit 6
in, and the roll unit 7 was set to 2 L / min. As other experimental conditions, the casting speed was 0.97 m / min on average,
We cast 460 charges per month. The roll was continuously used under such conditions, and the spread index between the roll surfaces with respect to the roll usage period was obtained. The roll surface spread index was calculated by measuring the roll diameter when the continuous casting machine was stopped. Further, as a comparative example, without performing roll cooling, also in the case of making the other experimental conditions similar to the above method,
The roll surface spread index for the roll usage period was obtained. The results are shown in FIG.

As shown in FIG. 9, by cooling the rolls, wear of the rolls due to heat load was reduced and spread between the roll surfaces could be suppressed. It has been found that the wear of the roll rapidly progresses as the time elapses, the spread between the roll surfaces becomes significantly large, and it becomes easy to hinder the transportation of the slab.

[0033]

The present invention is constituted as described above, and when water is sprayed onto a roll in a continuous casting machine to cool it, if the amount of water specified in the present invention is sprayed, the surface of the roll is kept below a certain temperature. It was possible to suppress the progress of wear by suppressing to, and it was possible to significantly extend the roll life. By extending the roll life in this way, it is possible to save the trouble of frequent roll replacement and repair, improve the productivity of the continuous casting machine, and reduce the cost required for roll maintenance. It was

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between roll surface temperature and roll wear index.

FIG. 2 is a graph showing the relationship between the amount of roll cooling water and the roll surface temperature.

FIG. 3 is a schematic view showing an arrangement state of rolls in a continuous casting machine.

FIG. 4 is a graph showing the relationship between the casting speed and the roll surface temperature, with or without roll cooling.

FIG. 5 is a graph showing the relationship between the casting speed and the slab defect occurrence rate according to whether the roll cooling water amount is controlled or not.

FIG. 6 is a diagram showing changes in roll surface temperature when roll cooling is restarted after casting is stopped.

FIG. 7 is a schematic view showing a method for measuring a roll surface temperature.

FIG. 8 is a schematic diagram illustrating an embodiment of roll cooling.

FIG. 9 is a graph showing a roll surface spread index with respect to a roll usage period according to presence or absence of roll cooling.

[Explanation of symbols]

1 roll part 1 2 roll section 2 3 Roll part 3 4 roll section 4 5 Roll part 5 6 Roll section 6 7 Roll 7 8 Radiation type temperature measuring device 9 rolls 10 Roll part that was in contact with the slab when the casting was stopped 11 mist nozzle 12 Mist-like water 13 slab

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 2000-126854 (JP, A) JP 2-247053 (JP, A) Actual development HEI 7-3851 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B22D 11/128 340 B21B 27/10 B22D 11/16

Claims (2)

(57) [Claims] 1. A vertical bending die or a bending die continuous casting machine.
Kicking established the mist nozzle or spray nozzle of the roll cooling dedicated to roll to support the cast piece, spraying from the nozzle one per 0.3 L / min or more water roll on the roll, 600 ° C. The surface temperature of the roll If you do the following
At the same time, spraying water on the rolls at the bending part when continuous casting is stopped
A method for cooling a roll in a continuous casting machine, which comprises stopping the scraping . 2. The roll cooling method for a continuous casting machine according to claim 1, wherein the amount of water sprayed onto the roll is controlled so as to satisfy the following formula (1) according to the casting speed. Q ≧ 5.0 Vc-3.0 (1) [However, Q: roll cooling water amount (L / min), Vc: casting
Build speed (m / min)]