JPS6012256A - Continuous casting method with variable width - Google Patents

Abstract

PURPOSE:To decrease an air gap and moving thrust and to change stably width at a high speed by moving the short pieces of a casting mold used with a continuous casting device at the moving speeds respectively in the upper and lower parts of the short pieces decreased stepwise in the initial and end periods of the movement. CONSTITUTION:A continuous casting method with variable widths consists of fixing the long sides of a casting mold, moving parallel short pieces 1 at the increased angle of inclination and returning the angle of inclination to the prescribed angle at the end of the movement. The reduction of the width of the casting mold by moving the pieces 1 from the left to the right or the expansion of the width by moving the same from the right to the left is accomplished by inclining the top surface 1a of the short piece at a relatively large speed Vm1 for the beginning in the initial period of the movement, then decreasing stepwise the speed to V'm1, inclining said piece by DELTAT'1 to incline the same by DELTAT1 as a whole and to increase a desired angle of inclination, moving parallel the pieces 1, returning the bottom surface 1b of the short piece at Vm3 at the end of the movement, then moving the same by DELTAT'2 at a low speed V'm3 and returning the inclination DELTAT2 as a whole to a prescribed angle, thereby completing the change of the mold width.

Description

[Detailed Description of the Invention] [Object of the Invention] The present invention reduces the air gap and reduces the moving thrust of the short piece when changing the inclination angle of the mold short piece when changing the width during continuous casting. The object is to change the inclination angle, and to provide a method for stably and rapidly changing the width.

[Prior art]

A known technique for changing the mold width during continuous casting is to fix the long sides of the mold and move the short pieces. FIG. 1 shows an example of a well-known variable width mold in which the short pieces are configured to be movable.
It is configured so that it can move forward or backward in the width direction of the slab 2. In this movement of the short piece, for example, as shown in Fig. 2 (when width is reduced) and Fig. 3 (when width is expanded), at the beginning of the movement, the inclination angle α' of the short piece is made stronger than the predetermined angle α during normal operation ( ml), then move the short piece in parallel (
ml) Return to the predetermined angle α during the L-1 movement path period (m3
) methods are also known. FIG. 4 shows the movement of the short piece in the form of a velocity diagram of the top surface 1a and bottom surface 1b of the short piece, taking as an example the case where the width is reduced by 5. At φ in FIG. 4, first, the slab 2 is moved in the direction of width reduction at the speed of the upper surface 1a'QVm1 of the short piece 1, and the inclination angle α' of the short piece 1 is increased by the predetermined angle α. Next, the short piece l is moved in parallel at a speed of vml, and the lower surface 1 b of the short piece l is moved along the movement path where the upper surface IJI of the short piece has reached a predetermined width.
Width reduction is performed by t-Vms. The amount of change in inclination ΔT for obtaining the inclination angle α' during the parallel movement is generally determined by the following equation based on the short piece parallel movement speed Vm2 and the casting speed Vc.

ΔT: Tilt change amount, Vm2: Short piece parallel movement speed:
Inclination change coefficient, vc: Casting speed t: Effective short piece length, Therefore, short piece moving speed Vm2 to implement high-speed width variation
For larger sushi, the inclination change amount ΔT is larger.
Short piece upper surface 1a or short piece lower surface 1b when changing the inclination angle of
If the moving speeds Vml and Vm3 are not increased, the gap between the solidified slab shell and the short wall of the mold (hereinafter referred to as air gap) will become large when changing the inclination angle, causing breakout and the like.

On the other hand, if the moving speed Vml@Vm3 at the time of changing the inclination angle is increased, the deformation resistance of the solidified slab shell increases, and the deformation resistance becomes extremely large at the end of the inclination angle change. Therefore, a thrust force for moving the short piece is required that exceeds the above-mentioned resistance force, and equipment for moving the short piece becomes expensive. Furthermore, if the moving speed when changing the inclination angle is increased, it becomes difficult to ensure the stopping accuracy when changing and stopping the inclination angle. This poor accuracy of the inclination angle affects the quality of the slab. It has a large negative effect on deterioration and breakout.

As described above, if the inclination angle changing speed VmsVm3 is constant, there is a drawback that no matter how fast or slow the inclination angle changing speed is, it has an adverse effect on the slab.

[Configuration 1 of the Invention] The present invention is a variable width continuous casting method in which the long sides of the mold are fixed and the short pieces are moved. In the method of returning to the specified state,
It is characterized in that the speed of the upper part of the short piece is reduced in stages when changing the inclination angle at the beginning of movement, and the speed of the lower part of the short piece is reduced in steps when changing the inclination angle at the end of movement. FIG. 5 shows an example of speed change based on the present invention, and is a speed diagram representing short piece movement during two-width reduction.

In this example, first, the upper part of the short piece is moved at a high speed ml to increase the inclination angle of the short piece l. When changing the inclination angle at the beginning of movement to strengthen this inclination angle, if the short piece upper part leaves only ΔT/ out of the inclination change amount ΔT1, the short piece upper part moving speed is reduced by Vm (i, and the set inclination angle α during parallel movement is ′
Change to Then, the short piece is moved in parallel at a speed of Vm2 to change the width of the mold. When the upper part of the short piece reaches the set width, the moving speed of the lower part of the short piece is reduced to Vm3', and the change of the inclination angle is completed, while leaving an inclination movement amount ΔT2' for the lower part of the short piece.

By the way, when changing the inclination angle, the timing of increasing the inclination angle and then shifting to parallel movement and the timing of returning the inclination angle to a predetermined angle α and stopping the movement of the lower part of the short piece are determined by, for example, the cylinder device f31.32 shown in FIG.
It is determined by detecting the stroke of the short piece l or by detecting the positions of the upper and lower surfaces 1a and lb of the short piece l. Based on the detected value, a parallel movement start command and a stop command are issued to the drive devices such as the cylinder devices 31 and 32. Therefore, unlike the conventional method, the parallel movement start command and stop command are issued directly from the high-speed movement state. When you start or stop movement, the above
Due to the time difference between when it is detected that the lower surface position has reached the set position and when the parallel movement actually starts or stops, the upper and lower surface positions have a large error with respect to the set position.

Therefore, the angle of inclination α' during parallel movement and the predetermined angle α after returning to normal operation do not match the optimal angle set in advance, causing breakouts and surface flaws.

On the other hand, when width reduction is carried out, if the lower part of the short piece with a thicker solidified shell is moved at high speed, the thrust will become larger. Figure 6 shows the short piece being moved in the conventional high-speed state (in the direction of width reduction).
This shows the changes in the thrust acting on the short piece when the short piece is moved, and it can be seen that the thrust increases rapidly especially when returning to the predetermined angle α at the end of the movement. As described above, the present invention reduces the speed of the upper and lower parts of the short piece stepwise when changing the inclination angle at the beginning and end of the short piece movement, so that even if there is the time difference mentioned above, the amount of movement (including deviation) This makes it possible to keep the angle of inclination of the short pieces to a minimum and change the inclination angle of the short pieces with high precision. In addition, as shown in FIG. 7, the speed decreases at the end of the inclination angle change when the thrust of the short piece increases rapidly, so the thrust can be greatly reduced, and therefore the drive of the cylinder devices 31, 32, etc. There is no longer a need to increase the equipment capacity.

Now, in the example of FIG. 5 mentioned above, ΔT1 and ΔTl'
, ΔT2 and ΔT2'', and V m 1 and 7m (, VmB
The relationship between VmB and short piece moving speed (Vml, Vm2
, VmB)Also, in the above example, the movement speed was reduced only once when changing the inclination angle, but if the width variable speed v is very large or the inclination change amount ΔT becomes large, etc. Even if it is reduced multiple times or continuously, the effects of the present invention described above can be obtained. Also, in the case of width expansion, it is possible to perform short piece movement in the same manner as in the example of width reduction. FIG. 8 is a diagram showing the speed of the upper and lower surfaces 1a and 1b of the short piece when the width is expanded.

As described above, according to the present invention, it is possible to increase the moving speed V, Vrr+4 when changing the inclination angle, and the time required to change the inclination angle can be shortened. It can sufficiently follow the piece solidified shell, reduce the air gap, and further reduce the short piece moving speed to Vm1' at the end of the change in inclination angle.
, Vm3', it is possible to reduce the deformation resistance of the solidified slab shell, and to improve the stopping accuracy with respect to the target when changing the inclination angle.

〔Example〕

The present invention was carried out when a slab having a width of 1000 mm and a thickness of 250 m was reduced to a width of 900 km during continuous casting.

In this embodiment, as shown in FIG. 7, the casting speed Vc=1.
6m/af* vml = Vms = 48m/”, V
ml' = Vm3'-24H/jl&, 7m2 =
Width reduction was performed at 32WrM/-. At this time, ΔT1 and ΔT2 are calculated using the following formulas.The slope change coefficient was set to 0.7, and the effective short piece length t was 772 m. Therefore, ΔT
II and ΔT2' are the amount of deviation when moving to V m 3' (3+ in vml = Vms = 48#/-)
The number of songs was set to 4, taking into consideration the following:

As a result, in this example, in order to reduce the deformation resistance force of the slab shell when changing the inclination angle and improve the accuracy of stopping the inclination angle, compared to the case where the slab was moved at a constant speed of v = 7m3 = 24mm/-. The angle of inclination was reduced to 0.8 m. In addition, the deformation resistance of the slab solidified shell and the accuracy of stopping the inclination angle at the final stage of changing the inclination angle were maintained at the same level as before.

As described above, according to the present invention, when changing the inclination angle when changing the width of the rod, it is possible to reduce the air gap, reduce the movement thrust of the short piece, and change the inclination angle with high precision.

〔Effect of the invention〕

With the present invention, when changing the inclination angle, by reducing the air gap and short piece movement thrust and improving the inclination angle stopping accuracy, high-speed width changes during continuous casting can be stably performed, and breakout can be achieved while maintaining good slab quality. It is possible to carry out variable width continuous casting without such troubles, and the effect is very large.

[Brief explanation of the drawing]

1 to 4 show conventionally well-known embodiments,
Figure 1 is a cross-sectional structural diagram of a variable width mold, Figure 2 is a structural diagram showing an example of a width reducing method, Figure 3 is a structural diagram showing an example of a width expanding method, and Figure 4 is a structural diagram showing an example of a width increasing method.
The figure is a velocity diagram of the upper and lower surfaces of the short piece when the width is reduced. Figures 5, 8 and 9 are velocity diagrams of the upper and lower surfaces of the short piece based on the present invention. Figures 6 and 7 are velocity diagrams of the upper and lower surfaces of the short piece when the width is reduced. 6 is a diagram showing how the thrust force generated in the short piece changes, FIG. 6 is based on the conventional method, and FIG. 7 is based on the method of the present invention. In the diagram, l is a mold short piece, 2 is a slab, ax; az is a patent attorney representing cylinder equipment Masamitsu Akizawa and 2 others

Claims (1)

[Claims] Q) In a variable width continuous casting method in which the long side of the mold is fixed and the short piece is moved, the short piece is moved in parallel by increasing the inclination angle, and the inclination angle is returned to a predetermined angle on the moving path.
A variable width continuous casting method characterized in that the speed at the top of the short piece is gradually reduced at the beginning of the movement, and the speed at the bottom of the short piece is gradually reduced at the end of the movement.