JPH084880B2 - Continuous casting lubrication method for wide and thin slabs - Google Patents

Description

The present invention relates to a method of lubricating a space between a mold and a slab when continuously casting a wide thin slab at a high speed.

(B) Conventional technology Conventionally, when a slab is generally manufactured by a continuous casting method, the slab thickness is about 200 mm or more.
The operation by powder lubrication is carried out. In recent years, for the purpose of simplifying the rolling process, attempts have been made to directly manufacture a slab that is considerably thinner than before by continuous casting. For example, when the slab thickness is 50 mm or less, the conventional immersion nozzle cannot be used, and even if a very thin flat nozzle is used, nozzle clogging easily occurs and stable large capacity continuous operation cannot be expected. . Also,
The thinner the slab, the higher the speed required for productivity, and the more difficult it becomes to operate stably.

Therefore, open hot water supply is indispensable for stable high-speed continuous casting of thin slabs. Therefore, the conventional powder lubrication cannot be performed, and the oil lubrication performed by the billet continuous casting is necessary.

With a billet with a small cross section, high-speed continuous casting of about 3.5 m / min is possible with oil lubrication.However, for wide cast pieces, the center of the cast piece width is bulging, so the mold and the cast pieces adhere closely. The conventional method of pouring oil from above the meniscus has a high risk of lubrication failure. Furthermore, during high-speed continuous casting, the shell thickness in the mold is thin overall, and the adhesion of the shell to the mold due to bulging is even greater, and it is essential to ensure lubrication. A method of forcibly supplying a lubricant just below the meniscus is known, for example, in Japanese Patent Laid-Open No. 57-58960. This method
If the meniscus falls below the supply hole due to fluctuations in the molten metal surface, there is a risk of seizure and breakout, and it has not been possible to completely guarantee lubrication.

In order to stably operate high-speed casting of wide and thin slabs with open hot water supply, uniform lubrication in the slab width direction is required.
It is difficult to guarantee sufficient lubrication only by a conventional method of pouring oil from the upper portion of the meniscus or a method of supplying a lubricant just below the meniscus.

Furthermore, for the supply of the lubricant from the lower part of the meniscus, the powdered lubricant is inserted through a narrow conduit in the mold, so there is a high risk that the supply will be impossible due to clogging or sintering of the lubricant, Breakout due to poor lubrication is likely to occur.

(C) Problem to be Solved by the Invention The problem to be solved by the present invention is to ensure uniform lubrication in the width direction of the slab during stable high-speed casting of a wide and thin slab, thereby enabling stable operation. To obtain a lubrication method.

(D) Means for Solving the Problem The continuous casting lubrication method for wide and thin slabs of the present invention is, when continuously casting wide and thin slabs, an amplitude of 10 to 10 in a continuous casting mold.
A high-frequency vibration of 500 μm and a frequency of 1000 to 10000 cpm is applied in the thickness direction of the slab, and a liquid lubricant with a boiling point of 1500 ° C or less is supplied from above the meniscus. The above problem is solved by supplying the acid-based lubricant from the lower portion of the meniscus.

(E) Action In the continuous casting lubrication method for wide and thin cast pieces, the lubricant from the upper portion of the meniscus and the lubricant from the lower portion of the meniscus are used together. At the same time, it was found that by vibrating the mold in the thickness direction of the slab at a high frequency, the supply of the lubricant from the lower portion of the meniscus can be effectively prevented from being defectively supplied due to clogging or sintering. At the same time, the effect of high-frequency vibration instead of the conventional oscillation is also obtained, and the surface defects caused by the oscillation marks are significantly reduced.

The lubricant supplied from the top of the meniscus has a boiling point of 1500 ° C.
The following oil-and-fat liquid lubricant has the effect of preventing seizure by producing a clearance in the meniscus portion by gasification of the lubricant. On the other hand, the lubricant supplied from the lower portion of the meniscus is a boric acid powder lubricant having a melting point of 1000 ° C. or lower and a decomposition temperature of 1500 ° C. or higher, and is supplied by a pump. When it comes out of the surface of the mold through the conduit and comes into contact with the slab to melt in the mold, it melts and exhibits a lubricating effect. However, immediately before melting, a sintering phenomenon occurs and the pipe is often clogged.
Further, even if it is not sintered, since the powder is supplied, the powder is often clogged by the resistance of the powder itself, and the supply becomes defective, so that lubrication often fails.

Therefore, by vibrating the entire mold at high frequency, clogging of the powder is prevented, and even if it is sintered, the friction with the conduit is reduced, so that the powder can be supplied thereafter. Furthermore, the vibration of the mold is 10 to 500 μm in amplitude and 100 in frequency.
By using a high-frequency vibration of 0 to 10000 cpm, the vibration of the mold itself has a lubricating effect, and conventional oscillation is not necessary, so that the surface defects caused by the oscillation mark are also greatly reduced. It is sufficient to supply the lower part of the meniscus within 100 mm below the meniscus. Preferably, it is changed according to the casting speed, and it may be within 100 mm below the meniscus at 3 m / min or less and within 150 mm below the meniscus at 3 to 5 m / min, and within 200 mm at 5 m / min or more.

(F) Embodiment An embodiment of the lubrication method of the present invention will be described with reference to FIG. The molten steel is supplied into the mold 1 by the open hot water supply stream 7 to form the cast pieces 6. The liquid lubricant 12 from the upper part of the meniscus 15 is naturally dropped from the header 11 along the mold wall, and becomes the vaporized lubricant 13 at the meniscus 15. The powder lubricant 14 from the lower part of the meniscus 15 is supplied from the tank 9 by the pump 8 to the communication hole 10 provided immediately below the meniscus of the mold 1 through the pipe 16.

The mold 1 has an amplitude of 10 to 500 μ by the vibration generator 2.
m, a high-frequency vibration having a frequency of 1000 to 10000 cpm is applied in the thickness direction of the slab 6. As a result, lubrication between the mold 1 and the slab 6 is achieved, and the friction of the powder lubricant 14 in the communication hole 10 is also reduced, so that the lubricant can be easily supplied. Mold 1
The smooth vibration is assured by the bearing and elastic member 5 provided on the base 4. The slab 6 is guaranteed to smoothly descend by the bearing 3.

 Next, a specific example of the actual implementation will be described.

In a single-point straightening continuous casting machine with a bending radius of 10 m, a wide thin slab having a thickness of 50 mm and a width of 1800 mm was cast at a high speed at a casting speed of 7 m / min on a slab. Open hot water is supplied from the steel types shown in Table 1, and normal oscillation,
The high frequency vibration of the method of the present invention was applied to the second strand.

As the lubricant from the upper part of the meniscus, repseed oil was used. As the lubricant from the lower part of the meniscus, the boric acid-based lubricant shown in Table 2 was used. 170 mm below the meniscus
Supplied in position. The repseed oil is supplied by dropping naturally from the header 11, and the boric acid-based lubricant is supplied by a pump.
The pressure was supplied up to ² kg / cm ² . Mold vibration condition is NO.1
Strand 6mm, cycle number 200cpm, NO.2 strand amplitude 120μm, frequency 6000cpm
Was used.

Figure 2 shows the breakout rate. This makes the effect of the method of the present invention clear. Also, looking at the No. 1 strand, it was found that poor lubrication from the bottom of the meniscus causes breakout.

(G) Effect According to the lubrication method of the present invention, the lubrication between the slab and the mold is ensured, and the constrained continuous casting of wide and thin slabs can be stably operated.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a casting mold for wide and thin cast pieces to which the lubrication method of the present invention is applied. Figure 2 is a graph showing a comparison of breakout rates. 1: Mold, 2: Vibration generator 3: Bearing, 4: Base 5: Elastic member, 6: Slab 7: Hot water flow, 8: Pump 9: Tank, 10: Communication hole 11: Header, 12: Fluid lubrication Agent 13: Gas lubricant, 14: Powder lubricant 15: Meniscus, 16: Pipe

Claims (1)

[Claims] 1. When continuously casting wide and thin slabs, a continuous casting mold has an amplitude of 10 to 500 μm and a frequency of 1000 to 10000 cpm.
High-frequency vibration is applied in the thickness direction of the slab, and the boiling point is 15
Continuous wide thin cast piece characterized by supplying liquid lubricant below 00 ℃ from the upper part of meniscus and boric acid lubricant with melting point below 1000 ℃ and decomposition temperature above 1500 ℃ from lower part of meniscus Casting lubrication method.