JPH02247053A - Method for cooling pinch roll for continuous casting - Google Patents

Abstract

PURPOSE:To restrain bending of a roll and to prevent the development of inner crack in a cast slab by arranging plural cooling holes penetrating a pinch roll for drawing the cast slab in axial direction and controlling cooling water supplying rate to the side in contact with the cast slab according to casting velocity. CONSTITUTION:In continuous casting equipment, the cooled and solidified cast slab 3 is pinched with the pinch rolls 1, 1 and drawn out. Plural cooling holes 11, 12 are provided penetrating toward the axial direction at the center and the prescribed pitch in circular direction in the above pinch roll 1. By supplying the cooling water into these cooling holes 11, 12, the pinch roll 1 is cooled. In the above cooling method, a nozzle header for supplying as injecting the cooling water is divided into the side 21 in contact with the cast slab and the side in no contact with the cast slab having nozzle slits 211, 221, respectively. At the time of lowering the casting velocity by prediction of breakout, etc., in the continuous casting, supply of the cooling water to the cooling hole 12 at the side in contact with the cast slab 3 is increased for the prescribed time through the above divided header 21 at the side in contact with the cast slab. By this method, the above pinch roll 1 is effectively cooled and the bending is restrained and the development of the inner crack in the cast slab is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a cooling method for a vinyl roll for drawing cast slabs in continuous casting equipment.

(b) In conventional continuous paving, molten metal supplied into a mold is cooled while passing through the mold, forming a solidified shell, and then gradually solidified by spray cooling while being guided by support rolls. The slab is then completely solidified and then cut to a predetermined length.

The slab is pulled out by pinching the slab with pinch rolls and pushing it out. At this time, if there is an unsolidified portion inside the slab, cracks will occur at the solidified interface of the slab depending on the pressure of the pinch rolls, and this will develop into internal cracks, causing problems in terms of slab quality.

In addition, in the recent trend of high-speed casting, the unsolidified portion spreads over a wide range, which widens the danger area where internal cracks may occur, making it even more difficult to adjust the pressure of the pinch rolls.

Furthermore, even if the pressure of the support roll is appropriate, if the roll itself is bent (for example, if the curved convex side is in contact with the slab), the pressure applied to the slab will be excessive and there is a possibility of internal cracking. becomes larger.

The bending of this roll is most affected by the deformation caused by heat from the slab. In particular, temporary changes in casting speed due to the top/bottom of casting or prediction of breakout,
Uneven heat occurs in the circumferential direction of the roll, causing bending due to thermal stress.

Conventionally, roll cooling is performed under constant cooling conditions regardless of the slab width or casting speed, so when the casting speed changes, the heat distribution of the roll changes and roll bending occurs.

For example, Japanese Patent Laid-Open No. 62-39065 discloses a method for straightening a roll by cooling the roll. In this method, when the rolls are cooled from the outside, the cooling water is also applied to the slab, which causes the slab temperature to become average - which causes problems with deterioration of internal quality due to surface flaws and changes in the shape of crater ends. .

Conventional internal cooling of rolls is uniform, and even though the temperature of the entire roll can be controlled, uneven heating in the circumferential direction of the roll cannot be prevented, and it takes a very long time to prevent bending. There is.

(c) Problems to be solved by the invention The problems to be solved by the present invention are to effectively cool the pinch rolls for continuous casting to suppress the bending of the mouth-hole, and to prevent the occurrence of internal cracks in slabs caused by this. The purpose is to prevent it.

(d) Means for Solving the Problems The method for cooling a pinch roll for continuous casting of the present invention provides a method for cooling a pinch roll for continuous casting in continuous casting equipment, in which a predetermined pinch is applied to the center and circumferential direction of the pinch roll. By providing a plurality of cooling holes penetrating in the direction, supplying cooling water to the cooling holes, and strengthening the supply of cooling water to the predetermined cooling holes on the side in contact with the slab for a predetermined period of time when the casting speed decreases. The above problem is solved by the following means.

The cooling water is supplied to the cooling holes arranged in the circumferential direction by water jetted from the nozzle header, and the nozzle header is divided into two parts: a slab contact side and a non-contact side. Adjustable control of water supply is preferred.

(E) Function When we investigated the roll fluctuation behavior of the pinch roll for continuous casting during casting, it was found that only roll bending occurs after the casting speed is reduced due to predicted breakout. This is because uneven heat is generated in the circumferential direction of the roll due to changes in the roll rotation speed, and bending occurs due to thermal deformation.

In order to prevent this uneven heat, bending can be prevented by strengthening the cooling of the part that is in contact with the slab by using a structure that changes the cooling intensity in the circumferential direction of the roll.

Therefore, cooling holes are provided in the circumferential direction of the pinch roll, and the cooling holes on the side in contact with the slab (for example, the lower cooling hole on the upper roll and the upper cooling hole on the lower roll) are connected to the other cooling holes. The cooling water systems are separated, and each system has a structure that allows variable cooling intensity. When the solek-out prediction is activated and the casting speed does not decrease, the flow rate of cooling water in the cooling hole system on the side in contact with the slab is increased, and the flow rate of cooling water in the remaining systems is decreased to prevent roll deviation. Can prevent heat.

After a certain period of time has passed after the casting speed change, both systems must be returned to the same cooling intensity.

Figure 4 shows the relationship between casting speed and cooling intensity of each system. After changing the casting speed, the time for maintaining cooling conditions varies depending on the width of the slab, secondary cooling conditions, etc., but approximately 5 minutes is required. The roll cooling strength also varies depending on the slab width and secondary cooling conditions, so the cooling water flow rate is usually about 1111/SeC. As the casting speed changes, it is sufficient to reduce the flow rate to about 2 to 3 times the normal flow rate in the system in contact with the slab, and to reduce the flow rate by about 20 to 30% of the normal flow rate in other systems. In some cases, there is no need to reduce it.

The existing cooling hole in the center is used for conventional cooling. At this time, if the cooling water flow direction of the central cooling hole and the cooling water flow direction of the circumferential cooling hole are made opposite to each other, 4N heat in the axial direction of the roll can be prevented.

(F) Embodiment An embodiment of the method of the present invention will be described with reference to FIGS. 1 to 3.

In the pinch roll cooling method of the present invention, a plurality of cooling holes 11 and 12 are provided at a predetermined pinch point in the center and circumferential direction of the pinch roll and axially pass through the pinch roll 1 for drawing slabs of a continuous @ production setting price. is provided to supply cooling water to the cooling holes 11, 1.2, and strengthen the supply of cooling water to the predetermined cooling holes 12.

Cooling water is supplied to the cooling holes 12 arranged in the circumferential direction by jet water from the nozzle header 2, and the nozzle header 2 is divided into two parts: a slab contact side (21) and a non-contact side (22). The water supply to the contact-side split header 21 is controlled in an adjustable manner.

Divided color, ivy 21.22 is arc-shaped nozzle swan 1
~211,221 are provided. Cooling water jetted from the nozzle print 21L 221 flows into each cooling hole 12. The cooling water flowing into each cooling hole 12 flows out from the opposite end.

The split header 21 on the slab contact side has an arc angle θ that allows water to be supplied to at least three cooling holes 12 at the same time, as shown in FIG.
It is preferable to have the following. Usually, this arc angle θ is 3
It is about 0 to 120 degrees.

As shown in FIG. 1, cooling water is supplied to the cooling hole 11 in the center of the roll in the conventional manner. In this case, it is preferable that the direction in which cooling water is supplied to the cooling hole 11 in the center of the roll and the direction in which the cooling water is supplied to the cooling hole 12 in the circumferential direction of the roll are opposite to each other. This is because uneven heat in the roll axis direction can be prevented.

The radial installation of the cooling holes 12 in the circumferential direction is approximately 1/2R to 3.5R of the roll radius R. '4R, is preferable.

Also, the diameter α of the cooling hole 12 is approximately 0.1D-
A range of 1-0.2D is preferred.

Next, specific embodiments of the method of the present invention will be described with reference to FIGS. 5 to 8.

In single-point straightening continuous casting equipment with a curvature radius of 1011,
A slab with a size of 200mm thick x 2000mm wide was cast at a casting speed of 2.0'','' minutes. Low carbon steel shown in Table 1 was used as the steel type. No. 1 strand pinch roll uses the roll cooling method according to the present invention, and No.
A comparison was made using a conventional uniform cooling method for a two-strand pinch roll. Investigate the roll surface temperature change and roll bending during casting.

Both strands No. 1 and No. 2 were cast from the same strand into two molds.

The carbon steel shown in Table 1 was cast. The amount of roll bending and the occurrence of internal cracks were investigated using the method of the present invention for No. 1 strand.

Table 2 Casting speeds range from 2.0 to 1.0 m/min. Fig. 5 shows the changes in the cooling water flow velocity of the N011 strand when the temperature was changed up to 7 minutes. FIG. 7 shows the roll surface temperature change associated with this. Compared to the No. 2 land roll of Comparative Example where the temperature locally rose to 250° C. or higher, almost no temperature change was observed in the method of the present invention. At the same time, the amount of roll bending was investigated using a differential transformer installed in the center of the roll, and the results are shown in Figure 6. Comparative example No.
, a two-strand roll has a periodic variation of about 2 mm,
In other words, it can be seen that while no roll bending was observed, there was almost no change in the method of the present invention compared to when the casting speed was constant.

Next, the size is 200 mm thick and 2000 mm using the same equipment.
When casting a slab with a width of 2.0"/min as shown in Table 2, a breakout prediction occurred and the casting speed temporarily decreased to 0.8111/min. The amount of bending is shown in Fig. 8. In the comparative example No. 2 strand, bending of about 1.51 T1 m occurred, whereas in the method of the present invention, there is almost no change.

In addition, internal cracks were investigated by sulfur printing on the cross section of the slab at this location, and internal cracks occurred in No. 2 strands 1 to land, but no internal cracks occurred in No.] strand. However, the method of the present invention is effective in preventing internal cracking by preventing roll bending.

(1~) Effects According to the method of the present invention, the pinch rolls for continuous 5JJ production can be effectively cooled, so that bending of the rolls can be suppressed and the occurrence of internal cracks in the slab can be prevented.

[Brief explanation of drawings]

FIG. 1 is a front view of a pinch roll for continuous casting to which the method of the present invention is applied. Figure 2 is a cross-sectional view taken along the line ■-■ in Figure 1. FIG. 3 is a cross-sectional view taken from the line ■-■ in FIG. Fourth
The figure is an explanatory diagram showing the principle of the method of the present invention. Figures 5 to 8
The figures are explanatory diagrams of specific embodiments of the method of the present invention. 1: Pinch roll 2: Hepta 21: Ivy to the slab contact side division 22: Ivy to the slab non-contact side division 11. 12: Cooling hole 211. 221: Nostle slit Patent applicant Sumitomo Metal Industries, Ltd. (external 4) Name) Figure 5 I'tlI-■ 2nd day of φ month q, 1st year of the Heisei era, Title of the invention: Method for cooling pinch rolls for continuous casting 6, Relationship with the person making the amendment case

Claims (1)

[Claims] 1. In a pinch roll for drawing slabs of continuous casting equipment,
A plurality of cooling holes are provided at a predetermined pitch in the center and circumferential direction of the pinch rolls, passing through the axis in the axial direction, and cooling water is supplied to the cooling holes so that when the casting speed decreases, the side in contact with the slab is closed for a predetermined period of time. A method for cooling pinch rolls for continuous casting, characterized by strengthening the supply of cooling water to predetermined cooling holes. 2. Cooling water is supplied to the cooling holes arranged in the circumferential direction by water jet from the nozzle header, and the nozzle
2. The method according to claim 1, wherein the header is divided into two parts: a slab contact side and a non-contact side, and the water supply to the contact side divided header is controlled in an adjustable manner.