JPH03297546A - Method for oscillating mold for vertical type continuous casting - Google Patents

Abstract

PURPOSE:To achieve stable high velocity casting by relatively advancing/ retreating one pair of mold faces at only one time during executing plural times of vertical oscillations to a mold for vertical type continuous casting having plural pairs of mold faces. CONSTITUTION:The mold for vertical type continuous casting is formed by making casting space with two pairs of the mold faces of mold long side 1 and mold short side 2. During executing N times (N>=2) of the vertical oscillations to the mold, one pair of the mold faces composed of the mold long side 1 are relatively advanced (approached)/retreated (separated) at only one time. During ascending the mold, one pair of the mold faces are retreated, and during descending, these are advanced. Lower parts of the mold faces are taken as a fulcrum and only upper parts are opened/closed. By this method, flowing condition of mold powder into between the mold face and solidified shell is adjusted and breakout can be prevented.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a continuous metal casting method, particularly a method of vibrating a casting mold in vertical continuous casting, which does not cause breakout even in high-speed casting. be.

<Prior art> When performing continuous casting in a vertical continuous casting machine,
The mold is vibrated vertically and at the same time mold powder is added to the molten steel in the mold to reduce the friction between the mold surface and the solidified shell.

The action of this mold powder is closely related to the vibration conditions of the mold, and it is important to adjust the vibration conditions so that an appropriate amount of mold powder flows into and is consumed between the mold surface and the solidified shell.

In general, a method is used in which the mold vibration method GJ, the mold vibration speed ■, is a sine wave as shown in Figure 2, but in this case, the amount of mold powder consumed is It is known that the speed depends on the positive strip time T, which is smaller than the drawing speed of the slab. Also,
It is also known that high speed casting tends to reduce mold powder consumption and increase restraint breakouts and slab surface defects. In order to solve these problems, we have developed a method to reduce the viscosity of mold powder and
As shown in Japanese Patent No. 955, the negative strip time T
A method has been disclosed in which the vibration waveform of the mold is made into a biased sine waveform, which is deviated from a sine waveform, by shortening the Tr waiting time.However, this method complicates the vibration mechanism and increases the The reality is that there are problems such as destabilization of surface defects, and that fully satisfactory results have not been obtained.

Further, as shown in U.S. Patent No. 3,494,411, there is a method in which a vertical water-cooled mold is used and the mold is vibrated in the vertical direction in the same direction as the casting direction, and in the horizontal direction perpendicular to the casting direction. is also disclosed. However, this method has a problem in that the inflow amount of mold powder cannot be adjusted in accordance with the casting conditions because the vertical vibration and the horizontal vibration are performed independently.

<Problems to be Solved by the Invention> In view of the above-mentioned current situation, the present invention controls the inflow amount of mold powder by increasing or decreasing the distance between the mold and the solidified shell in accordance with the material to be cast. This invention has been made in order to provide a method of vibrating a vertical continuous casting mold that can stabilize high-speed casting and prevent breakage.

Means for Solving the Problem> The present invention is characterized by: A vibration method for a vertical continuous casting mold characterized by relatively advancing (approaching), receding (separating), and sweeping.
■When the mold is rising, the distance between the mold and the solidified shell is increased by retracting the pair of mold surfaces, and when the mold is descending, the distance between the mold and the solidified shell is increased by advancing the pair of mold surfaces. A method for vibrating a vertical continuous casting mold as described in the preceding item (1), characterized in that the distance is reduced, and (1) the vertical vibration period of the mold causes a pair of mold surfaces to retreat over the entire positive strip time period or during a period of time. The method is characterized in that the distance between the mold and the solidified shell is increased by moving the pair of mold surfaces forward during the whole or part of the negative strip period, and the distance between the mold and the solidified shell is decreased by moving the pair of mold surfaces forward. In the method of vibrating a vertical continuous casting mold described in the previous section, the pair of mold surfaces relative to the cast metal are advanced (approached) by opening and closing the upper part of the mold, using the lower part of the mold surface as a fulcrum.・The previous item ■, ■ characterized by retreating (separating)
Or the method of vibrating a vertical continuous casting mold described in (2).

For Kusaku The operation of the present invention will be explained below with reference to the drawings.

In FIG. 2, Z is a sine waveform indicating the position of the mold due to glue vibration, and ■□ indicates the vibration speed of the mold at that position. When the mold reaches the highest point, the mold vibration speed V8 becomes 0, when the mold starts to descend, the vibration speed (i) gradually becomes faster, and when the mold reaches the lowest point, the vibration speed (i) becomes zero.

When the mold starts to rise again, the vibration speed increases.

Also, the longitudinal vibration of the mold and the drawing speed of the slab■. ■ The vibration velocity of the mold in correlation with the . However, the drawing speed of the slab ■. The slower time is called the positive strip time T2, and the time faster than the slab drawing speed Vc is called the negative strip time Tll.

As shown in FIGS. 4(a) to 4), the present invention has a method in which the vibration of the vertical continuous casting mold moves the mold backward over the entire positive strip time or during a period of time or during the rise of the mold.・The distance between the solidified shells is increased from X to It is possible to reduce the frictional force between the mold and the mold surface, thereby preventing restrictive breakout caused by the solidified shell sticking to the mold surface. This kind of operation is performed once every N times of longitudinal vibration (see Figure 3,
In the case of N-3).

This will be explained in detail below.

As shown in Fig. 1, in a continuous slab casting machine, generally, a method is adopted in which the short side 2 of the mold is clamped by the long side 1 of the mold. The movement of the mold is achieved through a hydraulic circuit. During casting, the long side of the mold
If too much gap is created between the short sides of the mold, molten steel will easily enter the gap and cause casting troubles. Therefore, the amount of mold retraction (X, -X,) is within 1 mm, and 0,5 mm.
It is desirable to keep it within the range.

In addition, in this method, the reason why the long side mold is not moved in the horizontal direction for each vertical vibration is that when the long side mold 1 returns to its original position, that is, when it approaches the short side mold 2, the control Due to inconvenience, the long side mold 1 is the short side mold 2.
This is to prevent and reduce deformation of the mold due to collision with the mold. For this reason, horizontal vibration is performed once every N times of vertical vibration. The value of N depends on the mold material (strength, hardness, etc.) and casting conditions (vibration frequency).

It may be determined empirically depending on the casting speed, etc.), and in the embodiment of the present invention, 2 to 10 is optimal.

On the other hand, considering the frictional force between the mold and the solidified shell, the frictional force F applied to the solidified shell can be estimated as the shearing force of the mold powder between the mold and the solidified shell.

This force F is expressed by the following formula.

x However, A: Contact area between the mold and solidified shell μ: Mold surface
Viscosity of the mold powder that has flowed between the solidified shells 7: Relative velocity between the mold surface and the solidified shell (positive strip time), and increasing the distance X between the mold and the solidified shell during the positive strip time as in the present invention is effective because it is inversely proportional to the frictional force F. This can prevent the occurrence of restrictive breakout, which is a particular problem during high-speed casting.

In addition, as shown in FIGS. 4(e) and 4(f), by retracting the mold or gradually retracting it while the mold is rising (including a part of the positive strip time), the mold can be removed.
It goes without saying that the same effect can be expected even if the distance between the solidified shells is increased and a sufficient amount of mold powder is allowed to flow in.

The pattern (trajectory) when opening and closing the long side mold is as follows.
It is not necessary to limit the waveform to the example shown in FIG. 3; for example, a continuously changing sine wave or cosine wave may be used.

In the present invention (example), the distance between the mold and the solidified shell is adjusted by simultaneously moving the upper and lower parts of the mold forward and backward using hydraulic cylinders, as shown in FIG. As shown in FIG. 6, the same effect can be obtained by adjusting the distance between the mold and the solidified shell by opening and closing only the upper part using a hydraulic cylinder or the like, using the lower part of the mold as a fulcrum.

<Example> (Example 1) When a slab of low carbon aluminum killed steel is cast by vibrating the mold by the method of the present invention, the amount of mold powder flowing into the space between the mold and the solidified shell and the occurrence of breakout are as follows: Table 1 shows a comparison with the case where the mold is vibrated using a conventional sine waveform.

As is clear from Table 1, when the mold is vibrated according to the method of the present invention, the occurrence of breakouts is significantly reduced.

■ ■ 5... Solenoid pulp for opening and closing the upper clamp, 6...
・Solenoid valve for opening/closing the lower clamp, 7... Hydraulic morph, 8... Hydraulic tank, 9... Water-cooled mold, 10... Mold powder, If... Molten steel, 12... Solidified shell, Y: slab pulling direction, T: positive strip time, Tll: negative strip time, xo: enlarged mold.
Distance between solidified shells, xl... Distance between normal mold and solidified shell, ■6... Longitudinal vibration velocity of mold, VC... Pulling speed of slab, Z... Longitudinal vibration displacement of mold .

Claims (1)

[Claims] 1. The pair of mold surfaces are moved relatively forward only once during vertical vibration of a vertical continuous casting mold that creates a casting space with the two mold surfaces N times (N≧2). A method of vibrating a vertical continuous casting mold characterized by (approaching) and receding (separating) a mold. 2. While the mold is rising, the pair of mold surfaces are moved back to increase the distance between the mold and the solidified shell; while the mold is descending, the pair of mold surfaces are moved forward to increase the distance between the mold and the solidified shell. 2. The method of vibrating a vertical continuous casting mold according to claim 1, wherein the vibration of a vertical continuous casting mold is reduced. 3. When the longitudinal vibration period of the mold is during the whole period or a period of the positive strip time period, the pair of mold surfaces is retreated to increase the distance between the mold and the solidified shell, and when it is during the whole period or a period of the negative strip time period, 2. The method of vibrating a vertical continuous casting mold according to claim 1, wherein the distance between the mold and the solidified shell is reduced by advancing the pair of mold surfaces. 4. Claim 1, characterized in that by opening and closing only the upper part of the mold with the lower part of the mold surface as a fulcrum, the pair of mold surfaces relative to the cast metal are moved forward (approaching) and retreating (separating). The method of vibrating a vertical continuous casting mold according to 2 or 3.