JP2952098B2 - Roll Breakage Detection Method in Continuous Casting Equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting breakage of a roll in a continuous casting facility.

[0002]

2. Description of the Related Art As shown in FIG. 1, a continuous casting equipment includes a ladle supporting device 1, which comprises a crane, a stand, a trolley, etc., a tundish 2, a mold 3, a slab cooling support and guiding device 4, a drawing straightening device 5, a cutting device. The slab cooling support and guide device 4 and the drawing and straightening device 5 are generally formed of rolls. As shown in FIG. The roll 6 is held down by a plate-shaped segment body 7.

[0003] Continuous casting equipment is roughly classified into a vertical type and a type shown in FIG.
There are curved type rolls as shown in
In particular, a large slab rolling stress is generated in each roll of the bending roll band, so that the roll is likely to break.If the roll breaks, the balance of the slab rolling stress is broken, cracks occur in the solidified shell, and quality defects occur in the product. In addition, it is dangerous because it can cause serious damage to equipment. Therefore, it is necessary to inspect the rolls. However, some rolls are difficult or impossible to observe from the outside. This is the case with segment rolls, where the outside is covered with the segment body and cannot be observed from the outside.Therefore, after stopping the equipment during regular inspection and repair, remove the segment body and At present, only one of these is observed and checked. However, removing and attaching the segment body one by one to inspect the roll requires considerable labor and labor, and the inspection work is complicated.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a detection method capable of detecting breakage of a roll which cannot be inspected by external observation or is difficult.

[0005]

A method for detecting breakage of a roll according to the present invention is to obtain a solidified shell thickness at each roll arrival point in advance for each casting condition such as a steel type, a casting speed, and a slab cooling pattern. When an internal crack in the slab due to breakage is detected, the distance from the slab surface to the position where the internal crack occurs is measured, and a roll corresponding to the solidified shell thickness that matches the measured value is estimated as a broken roll.

[0006] Examples of the detection means include a sulfur print test, a macro etch test, and an ultrasonic flaw detection test. The measurement of the distance from the slab surface to the position at which an internal crack occurs is performed, for example, by applying a scale and visually observing. Or using an image analysis device.

[0007]

A description will be given of an example in which internal cracks in a slab are detected by a sulfur print test. When the balance of the slab draft stress is lost due to the roll breakage and cracks occur in the solidified shell, MnS in the unsolidified molten steel is suction-concentrated into the cracks and breaks out. Using this phenomenon, internal cracks are detected by a sulfur print test. That is, after the cut surface of the slab is polished and mirror-finished, photographic paper dipped in an aqueous solution of dilute sulfuric acid is adhered to the finished surface. Then, the MnS precipitated by being concentrated by suction in the cracks reacts with the dilute sulfuric acid absorbed in the photographic paper to generate H ₂ S. This H ₂ S reacts with AgX in the photographic paper to form Ag ₂ S, and Ag ₂ S adheres to the cracked portion of the photographic paper that has been peeled off. FIG.
Shows an example of a sulfur print test surface, in which a central segregation 9 appears, and an adhesion spot 8 of Ag ₂ S on photographic paper becomes an internal crack. Next, the distance c from the slab surface to the crack occurrence position is measured using a scale or the like.

On the other hand, the thickness of the solidified shell of the slab at each roll position is determined in advance for each casting condition such as steel type, casting speed, and slab cooling pattern. FIG. 4 shows the relationship between the thickness of the roll and the solidified shell under the same casting conditions as when the above-described internal cracks occurred. The roll corresponding to the measured distance c was obtained by using the solidified shell thickness curve in this figure as a calibration curve. , It becomes a broken roll.

The upper and lower rolls sandwiching the slab can be classified according to whether the segregation occurs on the upper side or the lower side on the sulfur print test surface. In another example, internal cracks are detected by a macro etch test. That is, the polished cut surface is immersed in a hydrochloric acid solution, and the corroded cut surface is visually observed to detect internal cracks.

[0010] In still another example, an internal crack is detected by an ultrasonic inspection test. Then, it is subjected to image processing, and the length from the surface to the position where the internal crack occurs is read.

[0011]

EXAMPLE No. of curved continuous casting. No. 1 to No. For each of the rolls in each segment up to 9, the thickness of the solidified shell of each roll when 0.17C medium-carbon killed steel was cast at a speed of 1.6 m / min was determined by a known calculation formula. FIG. 4 shows the relationship between each roll and the thickness of the solidified shell under this condition.

FIG. 3 shows the result of detecting the internal cracks generated under the above casting conditions by the sulfur print test. The broken roll is estimated from the thickness of the solidified shell corresponding to the distance c to the internal cracks measured by the scale. However, when the segment body was removed and the corresponding roll was inspected, a broken roll was found.

[0013]

According to the detection method of the present invention, for example, a part of a roll which is covered with a segment body and cannot be inspected by external observation or difficult is removed, such as a segment roll. Roll breakage can be detected as it is without any modification to the equipment, and it is relatively easy to detect, so early detection of roll breakage is possible, and therefore quality such as internal cracking is reduced. Generation of abnormal slab material can be minimized, and serious equipment accidents can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic view of a curved continuous casting facility.

FIG. 2 is an enlarged sectional view of the main part.

FIG. 3 is a view showing a sulfur print test surface.

FIG. 4 is a diagram showing a relationship between a roll and a thickness of a solidified shell.

[Explanation of symbols]

2 ... Tundish 3 ... Mold 4 ... Slab cooling support and guide device 5 ... Pulling correction device 6 ... Roll 7 ... Segment body

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-75866 (JP, A) JP-A-52-41128 (JP, A) JP-A-50-17329 (JP, A) 248757 (JP, A) Japanese Utility Model Application Showa 53-158714 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) B22D 11/16 104

Claims (2)

(57) [Claims] 1. When the solidification shell thickness of a slab in each roll is previously determined for each casting condition such as steel type, casting speed, slab cooling pattern, and the like, and internal means of the slab due to roll breakage is detected by a detecting means. A method for detecting a broken roll in a continuous casting facility, comprising measuring a distance from a slab surface to a position where an internal crack occurs, and estimating a roll corresponding to a solidified shell thickness that matches the measured value as a broken roll. 2. The method according to claim 1, wherein the roll is a segment roll.