JPS63207460A - Method for changing width in continuous casting - Google Patents

Abstract

PURPOSE:To recover the contacting condition and to enable stable high velocity casting without any fear to the development of crack and breakout by intermittently changing cast slab width by stopping a short side for a fixed time at every shifting distance shown in the specific inequality. CONSTITUTION:The width of the cast slab is intermittently changed by stopping the shifting thereof for the fixed time beta sec at every shifting distance alpha shown in the inequality alpha<= (l+lbeta)XVm/Vc (wherein, l+lbeta:distance from meniscus to the lower part of the mold, Vc:casting velocity, Vm:shifting velocity of the short side of the mold) without changing the inclined angle of the short side 2 of the mold and without continuously shifting it. This shifting is executed so that the meniscus point A positions at A' point after shifting the short side 2 by distance alpha, and after stopping for beta sec, it positions at A'' point, and the above each value is decided by calculated value and the actual measured value, so as to satisfy the inequality. Such a shifting is repeated plural times and changing of the width is completed. By stopping it at every distance alpha, for beta sec, the contacting condition between the cast slab 1 and the short side 2 is recovered and stable high speed casting is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a width changing method in continuous casting.

(Prior art and its problems) In continuous casting, in order to improve the operating rate and slab yield, etc., a continuous casting method that changes the slab width without stopping pouring into the mold has been developed. It has been implemented. especially,
A method of directly linking the continuous casting process and rolling process has been put into practical use, and the technology of changing the slab width during continuous casting according to the width of the product sheet is becoming increasingly important.

The structure of the mold that changes the width of the slab is such that the short side of the mold is tilted between the long sides of the fixed mold to accommodate shrinkage caused by solidification of the slab. It is common to advance and retreat using a type drive device, and when changing the width, it is important to shorten the length of the part where the width changes as much as possible and immediately change it to the required width, so in the past, The short side of the slab is moved continuously at a constant speed.

However, in the case of such a movement of the short side of the mold, when the width is widened, the meniscus position A before width change becomes position A', as shown in Fig. 4, and the contact state between slab 1 and mold 2 becomes weak. , the risk of cracking or breakout occurring due to delayed solidification increases. When the width is narrowed, as shown in FIG. 5, the pushing amount becomes excessive, the pull-out resistance increases, the risk of cracking or breakout increases, and there is a risk of damage to the mold 2.

In order to improve this, there is a method of changing the short side inclination attitude before moving the short side, or as shown in Figure 6, changing the short side inclination position successively during width change to maintain the contact between the slab and the mold. Method for improving (JP-A-59-73154, JP-A-60-
No. 12256, Japanese Patent Publication No. 133855, Japanese Patent Application Publication No. 1983
-37253 Publication), but in the former case, it is necessary to change the inclination angle at once, and there is a high risk of breakout, and in the latter case, complicated control is required. Expensive measurement and control equipment is required to accurately hold the upper and lower ends of the short sides of the mold and to control the movement speed of the upper and lower ends of the short sides of the mold.

This invention was proposed in view of the above-mentioned circumstances, and its purpose is to enable stable high-speed casting without the need for complex control or expensive measurement and control equipment, and without the risk of cracking or breakout. The objective is to provide a method for changing widths.

(Means and effects for solving the problem) The width changing method according to the present invention changes the inclination posture of the short side, and without continuously moving the short side, the movement distance shown by the following formula is as follows: For each α, the slab width is changed intermittently by stopping for a certain period of time c.

By stopping for a certain amount of time at certain distances so that the meniscus before moving is positioned within the mold, the width can be changed while restoring the contact between the slab and the mold, making stable high-speed casting possible. Become.

(Embodiment) The present invention will be described below based on an illustrative embodiment.

As shown in Fig. 1, without changing the inclination posture of the short side 2 of the mold, and without continuously moving the short side 2, VC. However, l+lβ: Distance from the meniscus to the bottom of the mold VC: Casting Speed Vm: For each movement distance α expressed by the mold short side movement speed, the slab width is intermittently changed by stopping for a certain period of time β seconds.

In such a movement, the meniscus position A before the width change is located at point A' after moving the short side 2 by α, and after stopping for β seconds, is located at point A'', and each value is It is determined based on calculated values and actually measured values so as to satisfy equation (1).

The width change is completed by repeating such movement a plurality of times.

By stopping for β seconds every distance α, the contact state between the slab 1 and the short side 2 is restored, and stable high-speed casting becomes possible.

Vc=2.0 (m/min), L=0.8 [
m) +Vm=30 [mi/min), α=1
2 [xi).

When the width was changed according to the present invention under the condition of β-10 [seconds], the results shown in FIGS. 2 and 3 were obtained.

As is clear from this graph, in the conventional width change, the contact condition between the slab and the mold deteriorates as the width change begins, but in the present invention, the contact condition before the width change is maintained. .

(Effects of the Invention) As described above, according to the present invention, when the short side of the mold is moved a predetermined distance without being moved continuously,
By stopping for a certain period of time and changing the width intermittently, the contact state can be restored and the contact state before the width change can be maintained, so there is no risk of cracking or breakout, and stable high-speed casting is possible. It becomes possible.

Furthermore, there is an advantage that complicated control and expensive measurement and control equipment are not required.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the width changing method according to the present invention in order; Figs. 2 and 3 are graphs showing the contact state between the slab and the mold when the width is widened and when the width is narrowed; Fig. 4; FIG. 5 is a schematic diagram showing a conventional continuously moving width layering when the width is widened and narrowed, and FIG. 6 is a schematic diagram showing a conventional width change with variable inclination. 1. Slab 2. Mold short side Figure 4 Figure 6 Figure 5

Claims (1)

[Claims] (1) In continuous casting, in which the long side of the mold is fixed and the short side is moved to change the width during casting, the mold can be cast without changing the inclined posture of the short side or without continuously moving the short side. , for each moving distance α shown by the following formula, α≦(l+lβ/Vc)×Vm, where l+lβ: distance from the meniscus to the bottom of the mold Vc: casting speed Vm: mold short side moving speed. A width changing method in continuous casting, characterized by changing the slab width intermittently.