JPH05161945A - Twin drum type strip continuous casting method - Google Patents

Abstract

PURPOSE:To eliminate the defective sealing of a side weir during casting in a twin drum type continuous casting method. CONSTITUTION:At the time of detecting the defective sealing of the side weir, the side weir is immediately pushed to the end surfaces of the cooling drums in the condition of a surface pressure raising quantity A>=0.2kg/cm<2> and a surface pressure raising speed B>=1.0 and B>=-10XA+7kg/cm<2>/sec. By this method, the recovering ratio of the defective sealing can be obtd. at >=80%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously casting a ribbon from a molten metal by a pair of cooling drums.

[0002]

2. Description of the Related Art In the field of continuous casting of metal, there is a twin-drum system (using a pair of cooling drums) as a method for continuously casting a ribbon having a final shape. The outline of this method will be described with reference to FIG. 1. The molten metal M is composed of a pair of cooling drums 1, 1.
Is supplied from a tundish to a basin 4 formed between the side weirs 2 and 2, and then heat is removed through the cooling drums 1 and 1 to form solidified shells on the peripheral surfaces of the cooling drums 1 and 1. The solidified shell is pressure-bonded and integrated in the roll gap portion of the cooling drums 1 and 1 to be sent out as a ribbon S.

In the above method, the side weir is indispensable for sealing the molten metal between the cooling drums, and has a structure as shown in, for example, Japanese Utility Model Application Laid-Open No. 63-90548, and during casting. This side weir is pressed against the end surface of the cooling drum with a constant pressure, or the gap between the cooling drum and the side weir is kept constant to prevent leakage of molten metal between the end surface of the cooling drum and the side weir, or burr formation. Being tried.

[0004]

However, it is difficult to continue stable casting for a long time with the pressing force or constant gap control method. That is, the cause of the seal failure between the side dam and the end surface of the cooling drum is that the gap between the cooling drum and the side dam is equal to or larger than the limit gap into which molten metal is inserted, but even if the pressing force or the gap is constant, the cooling drum Further, both the side dam and the side weir are deformed non-uniformly by preheating before casting and heat from the molten metal during casting, so it is difficult to suppress the gap. The present invention aims to improve such problems during casting.

[0005]

In order to achieve the above object, the present invention provides a method for effectively pressing a side weir, particularly during casting. That is, a feature of the present invention is that a pair of side dams are pressed against both side surfaces of a pair of rotating cooling drums to form a basin, and the cooling drum is rotated to cool the molten metal in the basin to cool the ribbon. In the continuous casting method, the sealing condition between the end surface of the cooling drum and the side weir during casting is monitored, and when an abnormality in the seal of the side weir is detected, the side weir pressing surface pressure is increased by the surface pressure increase amount. A ≧ 0.2 (kg / cm ² ), surface pressure increase rate B ≧ 1.0 and B ≧ −10 × A + 7 (kg / cm ² / sec).

[0006]

The present invention will be described in detail below with reference to the drawings.
The defective sealing of the side weir during casting is mainly caused by the formation of minute metal (burrs) between the end surface of the cooling drum and the side weir, and the formation of a gap therebetween. Therefore, the abnormal state of the side seal can be grasped by knowing the burr state of the cast piece during casting, the molten metal leak from the side dam, the burr adhesion state on the end surface of the cooling drum, and the like.

According to the present invention, as shown in FIG. 1, a monitoring device 6 is installed below the casting device to monitor the presence or absence of the above condition, and when an abnormality of the side seal is detected, the pressing device 5 is immediately exposed to the surface. A pressure rise command is issued to raise the pressure to a predetermined pressing surface pressure, and the gap between the ceramic plate of the side dam and the end surface of the cooling drum is set to the melt insertion limit value or less. Fig. 2 shows the amount of surface pressure rise A and the amount of surface pressure rise to recover the side weir seal defect when a 2.3 mm thin cast piece was cast at a casting speed of 80 m / min using a cooling drum with a drum diameter of 1200 mm and a drum width of 800 mm. The relationship with the speed B is shown.

That is, the O mark in the figure indicates a seal failure recovery rate of 80% or more, but in the region where a high seal failure recovery rate is obtained, the surface pressure increase amount A is 0.2 kg / cm ² or more. Pressure rise rate B is 1kg / cm ² / sec or more and -10 × A
It can be seen that it is in the range of +7 kg / cm ² / sec or more. The larger each value is, the more preferable it is, but the upper limit of surface pressure rise is determined by the saturation of recovery effect of seal failure and the strength of the side weir. For a side weir lined with a ceramic plate, A = 6 kg / cm ² The upper limit of speed is determined by the performance of the pressing device, and B = 150 kg / cm ² /
It was sec.

The pushing surface pressure may be increased continuously or stepwise, and the side seal defect detection is mechanical,
It may be either optical (for example, displacement meter, CCD camera, spot radiation thermometer, etc.) or naked eye. An example of a method for controlling the pressing surface pressure is shown in FIG. Initially, pushing surface pressure P ₁
After casting until time A, the surface pressure increased and P ₂
Therefore, the seal is in a defective state until time B. During this time, burrs are generated between the drum end surface and the side weirs, which causes a reaction force in the side weirs to increase the surface pressure, and the surface pressure is balanced between them.

Therefore, at time B, a command for increasing the surface pressure is issued to activate the pushing device 5, and the surface pressure is rapidly increased to P ₃ (regional surface pressure of the present invention). As a result, the gap opened by the burr is reduced (the burr is buried in the side weir), the burr is removed as the wear progresses, and the defective seal is recovered. Then, after a lapse of time C, the indentation surface pressure P ₁ is returned to the initial value and the casting is continued.

The side seal failure phenomenon is rapidly deteriorated because the once leaked molten metal further promotes the deterioration of the sealing property. Therefore, it is necessary to activate the pushing device as soon as possible when a seal defect is detected. Therefore, the surface pressure P
_{When 2} is detected, a command is immediately given to the pushing device to shorten the time AB as much as possible. If the side weir is pushed into the end face of the cooling drum under the above pushing conditions, 80% of the sealing failure will occur.
You can recover with the above probability.

[0012]

[Example] A SUS304 stainless steel was cast at a casting speed of 80 m / min by using a casting device using a cooling drum having a diameter of 1200 mm and a width of 800 mm and a side dam lined with a ceramic plate, and using a stepping cylinder as a pressing device. did. CCD as a seal failure detection means
A camera was used.

When performing the above-mentioned casting, the rate of recovery of defective seals was determined by changing the rate of increase in the surface pressure of the side dam and the amount of increase. This is shown in Table 1.

[0014]

[Table 1]

As is clear from the above table, all the comparative examples indented under the conditions outside the scope of the present invention obtained a recovery rate of defective sealing of less than 80%, but within the scope of the present invention, all of them were recovered. It was possible to obtain a seal failure recovery rate of 80% or more.

[0016]

According to the present invention, the defective seal generated can be immediately recovered, so that a stable seal for a long time can be obtained and the casting yield can be greatly improved.

[Brief description of drawings]

1 is a schematic perspective view of an apparatus for carrying out the present invention.

FIG. 2 is a diagram showing the relationship between the amount of increase in the in-contact surface pressure and the surface pressure increase rate.

FIG. 3 is a diagram showing a relationship between time and surface pressure in implementing the present invention.

[Explanation of symbols]

 1, 1 ... Cooling drum 2, 2 ... Cooling drum end surface 3, 3 ... Side weir 4 ... Hot water pool 5 ... Pressing device 6 ... Monitoring device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoichi Wakiyama 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Plant (72) Inventor Hidenori Hattori 4-chome Kannon Shinmachi, Nishi-ku, Hiroshima Prefecture 6-22 No. 22 Mitsubishi Heavy Industries Ltd. Hiroshima Works

Claims (1)

[Claims] 1. A pair of side dams are pressed against both end faces of a pair of rotating cooling drums to form a basin, and by rotating the cooling drum, the molten metal in the basin is cooled to continuously form strips. In the method of casting, the sealing condition between the end surface of the cooling drum and the side weir during casting is monitored, and when abnormal occurrence of the seal of the side weir is detected, the side weir pressing surface pressure is increased by the following conditions. Characteristic twin drum type thin strip continuous casting method. Surface pressure increase amount A ≧ 0.2 (kg / cm ² ) Surface pressure increase speed B ≧ 1.0 and B ≧ −10 × A + 7 (kg / cm ² / sec)