JPH058003A - Method for casting with light rolling reduction in continuous casting - Google Patents

Abstract

PURPOSE:To secure the quality of a cast slab in on-line by precisely detecting the condition with a comparatively simple constitution in the case the solidified completing position is not the prescribed position at the time of casting with light rolling reduction and deciding whether the light rolling reduction effect (center segregation improving effect) exists or not, during casting. CONSTITUTION:Load cells 7A, 7B are set at between bearing parts 5A, 5B and stand frames of upper supporting rolls 4A, 4B in each cast slab supporting roll stand 3A, 5B arranged at upstrem side and downstream side, respectively, in the light rolling reduction applying zone 2 in a continuous caster 1, and loads acted to the cast slab supporting rolls 4A, 4B at the upstream side and the downstream side in the light rolling reduction applying zone 2, are measured, and also while confirming existence of the solidified completing position in the cast slab S at the time of casting with the light rolling reduction in the prescribed position in the light rolling reduction applying zone based on the measured result of these loads, the continuous casting is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light reduction casting method in continuous casting, and in particular, it has been confirmed that light reduction casting is performed on a slab in a state where an effect of improving center segregation of the slab is obtained. However, the present invention relates to a method of light pressure casting.

[0002]

2. Description of the Related Art In light reduction casting in continuous casting, the effect of improving the center segregation of the slab cannot be obtained unless the predetermined positions before and after the solidification completion position in the continuously cast slab are lightly reduced. It is said that. Therefore, it is necessary to know the solidification completion position in light pressure casting.

As one of the methods, a solidification completion position is calculated in advance, and based on the calculation result, a reduction position and a reduction gradient are set before casting, and light reduction casting is performed. In the case of this method, it is not known during casting whether the solidification completion position was within the predetermined range of the light reduction zone calculated. Therefore, it was judged whether or not the cast piece after casting had a light reduction effect (center segregation improving effect) by taking a sulfur print or the like of its cross section.

However, in such a method, there is a variation in the solidification completion position due to a change in conditions during casting (change in casting temperature, casting speed), that is, a variation in the effect of improving the center segregation, and all cast slabs are targeted. It is difficult to judge whether or not there was a center segregation improving effect.

On the other hand, as a method of detecting the solidification completion position during continuous casting, a method of measuring the static pressure of molten steel acting on a slab supporting roll by measuring it with a load cell provided in the bearing portion of the roll (JP-A-1-97051) Or a method of measuring and detecting with a pressure sensor provided on the surface of the roll (Japanese Patent Application Laid-Open No. Sho.
63-174770), or a method of detecting with ultrasonic waves (Japanese Patent Laid-Open No. 60-291455) has been proposed.

[0006]

However, in a roll arrangement having a so-called reduction gradient, in which the distance between the upper roll and the lower roll is narrowed in the casting direction during light reduction casting,
In the method of measuring and detecting the molten steel static pressure described above, since both the light rolling force and the molten steel static pressure are measured, it is possible to accurately detect that the solidification completion position is at a predetermined position within the light rolling application zone. Difficult to do. In addition, in the method of detecting by ultrasonic waves described above, a high-performance instrument must be installed in a high-temperature, high-humidity adverse environment part of the secondary cooling area of continuous casting equipment, which makes maintenance difficult and stable. It is difficult to accurately detect the coagulation completion position.

As described above, although various methods for detecting the solidification completion position of the slab have been conventionally proposed, a method for appropriately detecting the solidification completion position by arranging the solidification completion position in the light reduction zone during casting is still known. Has not been done. For this reason, it is impossible to determine whether or not there is a light reduction effect (center segregation improving effect) during casting, and it is still necessary to take a sulfur print or the like of the cross section of the cast piece after casting.

The present invention has been made based on the above circumstances, and its object is to provide a relatively simple structure.
When the solidification completion position is not located at the specified position during light reduction casting, that state is accurately detected, the presence of the light reduction effect (center segregation improving effect) of the slab is judged during casting, and the slab's online The purpose is to guarantee quality.

[0009]

In order to achieve the above object, a light reduction casting method in continuous casting according to the present invention is a light reduction application zone provided with a reduction gradient when performing light reduction casting in continuous casting. While measuring the load acting on the slab support rolls arranged on each of the upstream side and the downstream side of the, the solidification completion position in the slab during light pressure casting is within the light pressure application zone according to the measurement results of these loads. Continuous casting is performed while checking whether or not it is in a predetermined position.

[0010]

In the present invention, since the load acting on the slab support rolls arranged on each of the upstream side and the downstream side of the light pressure application zone is measured, only the molten steel static pressure can be accurately measured. Therefore, the measurement result of the load acting on the slab support roll during the proper light pressure casting that can sufficiently obtain the effect of improving the center segregation of the slab, and the measurement result of the load when the appropriate light pressure casting state collapses By comparing the above, when the solidification completion position is not located at a predetermined position during light pressure casting, the state can be accurately detected. Further, by this, it is possible to determine whether or not the center segregation improving effect of the slab is present during casting, and guarantee the quality of the slab online.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall schematic configuration view of a continuous casting machine according to the present invention as seen from a side surface, and FIG. 2 is an AA enlarged sectional view of FIG.

In these figures, each of the slab support roll stands 3A, 3B provided on the upstream side and the downstream side of the light pressure application zone 2 of the continuous casting machine 1 has its upper support rolls 4A, 4B. Load cells 7A, 7B are installed between the bearings 5A, 5B and the stand frames 6A, 6B.

Light continuous pressure reduction casting is performed by the continuous casting machine 1 having the above-mentioned structure, and when the solidification completion position of the slab S is within an appropriate light pressure reduction applicable zone where the effect of improving center segregation is sufficiently obtained, The static pressure pattern of molten steel applied to the load cells 7A and 7B provided on the slab supporting roll stands 3A and 3B when the pressure was deviated to the upstream side and the downstream side of the application zone was determined by measurement. The conceptual diagram of the obtained pattern is shown in FIG.

FIG. 3a is a diagram showing a pattern when the solidification completion position is within the proper light pressure application zone, and according to the measured curve x of the molten steel static pressure measured, solidification is performed in the light pressure application zone 2. As the static pressure of molten steel begins to decrease with progress, and a proper light reduction pattern in which solidification is completed in the applicable zone 2 is shown, and the effect of improving the center segregation of the slab S is sufficiently obtained.

FIG. 3b is a diagram showing a pattern when the solidification completion position is biased to the upstream side of the appropriate light pressure application zone, and according to the measurement curve y of the measured molten steel static pressure, the light pressure application zone 2 is shown. It was detected by the load cell 7A of the slab supporting roll stand 3A that the static pressure of molten steel had begun to decrease with the progress of solidification before entering the inside, and the solidification completion position was determined from the predetermined solidification completion position within the applicable zone 2 The pattern is on the front side (upstream side), and the expected effect of improving the center segregation of the cast slab S cannot be sufficiently obtained.

Further, FIG. 3c is a diagram showing a pattern when the solidification completion position is deviated to the downstream side of the appropriate light pressure application zone. According to the measurement curve z of the measured molten steel static pressure, the light pressure application zone is shown. The static pressure of molten steel that is still solidifying even after leaving the inside of 2 is detected by the load cell 7B of the slab supporting roll stand 3B,
The pattern is such that the coagulation completion position is behind (downstream side) the predetermined coagulation completion position in the application zone 2, and like the case when the coagulation completion position is biased to the upstream side,
The expected effect of improving the center segregation of the cast slab S cannot be sufficiently obtained.

The origin of the decrease in the static pressure of molten steel with the progress of solidification in the above measurement curves x, y, z is the solid phase fs of the slab center.
Is around fs = 0.3, and the point where solidification is completed is at the position where the solid phase fs at the center of the slab is around fs = 0.7. If this range is lightly pressed, the effect of improving the center segregation of slab S is sufficiently obtained. Be done.

In this way, by grasping the molten steel static pressure pattern as shown in FIG. 3 prior to the light pressure casting, the load cell 7A on the upstream side or the downstream side of the light pressure application zone 2 can be subjected to the light pressure casting. By measuring the molten steel static pressure acting on the side load cell 7B, the solidification completion position is
It is possible to determine during casting that it is in an appropriate position in the light reduction application zone 2 where the effect of improving the center segregation can be obtained. Therefore, the quality of the slab S can be guaranteed online, and it is possible to use the sulfur print after casting. You can save time and effort to confirm the effect of improving the center segregation, and if the effect of improving the center segregation is insufficient, you can immediately remove the part by marking during casting or take measures such as downgrading or soaking. Can handle.

In the above embodiment, one support roller 4A, 4B on the upstream side and the downstream side of the light pressure application zone has been described as an example, but a roll configuration that more appropriately measures only the molten steel static pressure is used. As shown in FIG. 4, is composed of a support roll 4 ′ that supports the unsolidified molten steel portion S ′ in the width direction of the slab S, and a support roll 4 ″ that supports both side portions S ″ of the unsolidified molten steel position. However, the load cell 7 may be installed between the bearing 5 of the upper support roll 4 ′ that supports the unsolidified molten steel portion S ′ and the stand frame 6.

[0020]

According to the light reduction casting method in continuous casting according to the present invention, the solidification completion position moves to the upstream side or the downstream side of the light reduction application zone due to fluctuations in molten steel superheat, casting speed, etc. during light reduction casting. Even in that case, the state can be appropriately detected, and it can be determined whether or not the light pressure casting is properly performed.

As a result, when it is confirmed that the solidification completion position is out of the predetermined light pressure application zone, the corresponding cast piece is regarded as the center segregation defective portion, and the grade down or soaking and diffusion in the next process is performed. Can be performed.

[Brief description of drawings]

FIG. 1 is an overall schematic configuration diagram of a continuous casting machine according to the present invention viewed from a side surface.

FIG. 2 is an enlarged sectional view taken along line AA of FIG.

FIG. 3 is a conceptual diagram of a measurement pattern of molten steel static pressure during light pressure casting according to the method of the present invention, where (a) is a pattern when the solidification completion position is within an appropriate light pressure application zone, (b)
Shows the pattern when the coagulation completion position is biased to the upstream side of the appropriate light pressure application zone, and (c) shows the pattern when the coagulation completion position is biased to the downstream side of the appropriate light pressure application zone.

FIG. 4 is an explanatory view of a support roll of another embodiment on the upstream side and the downstream side of the light pressure application zone according to the present invention.

[Explanation of symbols]

1: Continuous casting machine 2: Light pressure application zone 3A, 3B: Slab support roll stand 4A, 4B, 4 ', 4 ": Support roll 5, 5A, 5B: Bearing part 6, 6A, 6B: Stand frame 7, 7A, 7B: Load cell S: Cast slab x, y, z: Measurement curve of static pressure of molten steel S ': Unsolidified molten steel part S ": Both sides of unsolidified molten steel position

Claims (1)

Claim: What is claimed is: 1. When performing light reduction casting in continuous casting, it acts on the slab support rolls arranged on the upstream side and the downstream side of the light reduction application zone having a reduction gradient. Along with measuring the load, it is characterized by continuous casting while confirming whether the solidification completion position in the slab during light pressure casting is at a predetermined position in the light pressure application zone based on the measurement results of these loads. Casting method in light continuous casting.