JPH02303657A - Mold for continuous casting - Google Patents

Abstract

PURPOSE:To prevent spouting-up of cooling water and to prevent the degradation of surface quality in a cast slab by constituting separately a continuous casting mold having rectangular cross section and enabling the shift of cooling guide plates attachably/detachably. CONSTITUTION:Two pairs of mold walls 1 mutually faced in the continuous casing assembling mold having the rectangular cross section, are divided into two or more steps to casting direction and downstream mold wall 2 is divided to the lateral direction of the cast slab with cooling water guide plates 3 and further, the pair of cooling water guide plates 3 constituting the downstream mold walls 2 are constituted so as to be attachable/detachable. Further, by pressurized-supplying high viscosity liquid between the most upstream side and the downstream side molds through pipings 13, the gap between the mold walls is controlled and the cooling water is interrupted. By this method, the cooling water in the downstream side mold is prevented from the spouting-up to the upstream side and the damage of the surface quality in the cast slab is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a lower structure of a continuous casting mold.

(Conventional technology) Continuous casting molds usually have a length of 600 = 12 (loam), and the inner wall of the mold is made of a material with high thermal conductivity.
That is, it is made of copper, copper alloy, or the like.

When casting is performed using such a mold, the molten steel is indirectly cooled by a cooling medium (e.g. water) supplied inside the mold wall, and solidification progresses gradually from the part in contact with the mold wall, forming a solidified shell. As the thickness of the solidified shell grows to the extent that it can withstand the hydrostatic pressure of the internal molten steel, the solidified shell contracts, creating a void between the mold wall and the solidified shell.

Particularly in a mold with a rectangular cross section, the solidified slab shell in contact with the center of the wide wall of the mold tends to bulge outward due to the internal molten steel pressure and comes into relatively good contact with the mold wall. There is a tendency for voids to appear conspicuously in the lower part of the mounting side.

This generation of voids significantly reduces the efficiency of heat transfer from the slab to the mold wall, greatly inhibits the growth of the solidified shell of the slab, and causes quality defects such as surface vertical cracks due to uneven thickness of the solidified shell. This is often a major cause of breakout due to damage to the solidified shell. This is a major fundamental problem with the current continuous casting equipment, and is the biggest obstacle to achieving high-speed casting.

Therefore, in the specification and drawings of Patent Application No. 36643 of 1999, the present applicant has proposed that the formation of a solidified shell can be improved and uniformed by preventing the mold cooling ability from decreasing due to the gap between the slab and the mold formed at the bottom of the mold. With the aim of preventing severe wear on the mold walls by improving lubrication and improving lubrication, there is In addition, the downstream mold wall excluding the most upstream mold wall is divided in the slab width direction by a plurality of cooling water guide plates to form a pair of downstream mold walls. We have proposed a continuous casting mold in which the respective cooling guide plates are movable toward and away from each other.

(Problem H to be solved by the invention) The continuous casting mold proposed by the present applicant in Patent Application No. 36643 of 1999 is an excellent invention that can achieve the above-mentioned purpose. As shown in Figure 2, in order to provide the downstream mold with a strong cooling function using a high-speed water film, it is necessary to maintain the average flow velocity of the cooling water at 6 m/sec or more.

However, in this case, there is a concern that the cooling water may blow up toward the upstream mold.

Therefore, in the invention proposed by the present applicant, in order to prevent this cooling water from blowing up, it is desirable to use the uppermost row of cooling water guide plates that constitute the downstream mold as a drain port. Disclosed.

However, subsequent experiments revealed that the average flow rate of cooling water was 15
m/sec, it is possible to prevent the cooling water from blowing up by simply using the top row of the cooling water guide plate as a drainage port, but if the speed exceeds 15 m/sec, the top row of the cooling water guide plate should be used as a drain port. It was found that simply using a drain port could not effectively prevent cooling water from blowing up. This is because the direction of movement of the cooling water and the direction of the drain port are different, making it difficult to change the direction of water that is moving with a large amount of momentum.

However, the solidified shell in the upstream mold part is thinner than the solidified shell in the downstream mold part, and its strength is weaker, so when the cooling water blows up from the downstream mold part, the blown up cooling It is thought that the water causes non-uniform cooling and contributes to the deterioration of the surface quality of the slab.

The present invention has been made in view of the above problems, and
It is an object of the present invention to provide a continuous casting mold that can prevent the surface quality of slabs from being damaged by preventing cooling water from a downstream mold from blowing up into an upstream mold.

(Means for Solving the Problems) The present invention has been accomplished based on the results of various experiments and research conducted by the inventors in order to achieve the above object, and the gist thereof is as follows: In a continuous casting assembly mold having a rectangular cross section, one or both of the two opposing mold walls are divided into two or more stages in the slab casting direction, and the most upstream mold wall is The downstream mold wall excluding the downstream mold wall is divided in the slab width direction by a plurality of cooling water guide plates, and the respective cooling guide plates constituting the paired downstream mold wall are configured to be movable towards and away from each other. A means for press-feeding a highly viscous liquid between an upstream mold and a downstream mold following the mold is provided.

(Function) By adopting the configuration described above, the present invention can control the distance between the slab and the mold wall to be uniform in the width direction of the slab, and can also increase the cooling water blown up from the downstream mold. Can be completely blocked by viscous liquids.

(Example) The present invention will be described below based on an example shown in FIGS. 1 to 3.

FIG. 1 shows an embodiment of the present invention, and shows an assembly structure in which a continuous casting mold is divided into two parts, an upstream mold 1 and a downstream mold 2.

Incidentally, the upstream mold LL usually has a tapered mold wall or two pairs of opposing parallel mold walls.

On the other hand, the downstream mold 2 is composed of a plurality of cooling water guide plates 3 each having a rectangular shape or a hexagonal shape (not shown) shown in FIG. The mold walls are connected through the mold wall so that the mold wall surfaces forming a pair can move toward and away from each other. Further, the cooling water guide plate 3 is provided with five rows of water supply ports and six rows of drain ports alternately, and as shown in FIG. , each cooling water guide plate 3 can be moved by the cylinder 4 according to this detected value.

In addition, in order to prevent the cooling water from blowing up in the direction of the upstream mold 1, it is preferable that the uppermost row of the cooling water guide plate 3 be used as a drain port.

Furthermore, by forming at least one of the water supply port 5 and the drain port 6 into a slit-like elongated hole, a uniform flow of cooling water within the water film formed between the slab 10 and the cooling water guide plate 3 can be realized. . Note that 9 in FIG. 1 indicates a spring.

In the gap between the above-mentioned upstream mold 1 and downstream mold 2, a high-viscosity liquid jet nozzle 11 is placed at a common level position on the long and short sides of the mold, and stores the high-viscosity liquid. A highly viscous liquid is supplied from a tank 12 via a pipe 13 at a required pressure. It is desirable that this pressure be adjusted to a level that balances the static pressure of the molten steel at the outlet of the jet nozzle 11 so as to have the function of supporting the solidified shell. If this pressure is lower than the static pressure of molten steel, the solidified shell cannot be supported in the gap at the boundary.

As shown in FIG. 3, the outlet part of the jet nozzle 11 is
The outlet shape is a slit, and the slit hole 1
It is preferable to provide a plurality of pores 15 up to 4 so that a highly viscous liquid can be supplied.

This is because when the slit shape is used, the highly viscous liquid spreads uniformly in the circumferential direction of the entire slab in order to completely block the cooling water blowing up from the downstream mold to the upstream mold. Note that it is preferable that the slit hole portion 14 be arranged so as to have a downward slope as shown in FIGS. 1 and 2.

High viscosity liquid can block cooling water from blowing up because the high viscosity liquid film acts as a barrier and absorbs the upward kinetic energy of the cooling water, and the liquid itself is also highly viscous. This is because it will not flow unless a shearing force of .

The viscosity of the liquid is preferably about 100 to 10,000 times higher than the viscosity of water in the temperature range between the mold and the slab. According to experiments conducted by the present inventors, if the viscosity is less than 100 times that of water, even at the minimum speed of 6 m/sec for cooling water to achieve one of the objects of the present invention, the shear force This is because the liquid will flow and cannot be shut off. On the other hand, from the viewpoint of shutoff, the higher the viscosity, the better; however, if the viscosity exceeds 10,000 times, the fluidity will be extremely reduced, making it impossible to actually supply liquid between the slab and the mold.

Next, the results of experiments conducted to confirm the effects of the present invention will be explained.

2 to 6 m of low carbon aluminum killed steel weighing 50 tons per heat
A continuous casting machine equipped with a two-stage continuous casting mold shown in FIG.
A slab of 50 cm was produced. The length of the upstream mold used at this time was 350cm (the length below the meniscus was 250cm).
22 rectangular cooling water guide plates (width: 100 m, length 2550 m) shown in Fig. 1 were attached to the downstream mold ((10 on the mold wide side, 1 on the mold sandwiching side) x 2. ).

Details of the water inlet and drain outlet of the cooling water guide plate are as follows.

Water inlet: Height 1.5g x Width 12! I11 drain: height 2
．． 2 cabinets x width 12II 111 Interval between water inlets and drains: 2aa each Horizontal pitch of water inlets and drains: 1
4mm + Distance between water supply port row and drain port row: During 50 castings, the flow rate of cooling water in the downstream mold was set at 6 to 40 m/sec.
Casting was performed by changing the temperature within the range of c.

As the ejection nozzle of the apparatus of the present invention, a slit hole portion having a width of 10 m and a depth of 5 mm, and pores having a diameter of 3 m were arranged at equal intervals of 14 m in the horizontal direction.

Further, as the highly viscous liquid, two types of commercially available silicone oils with a viscosity of 200 cp and 3000 cp were used.

Furthermore, for comparison, an experiment was conducted using only a two-stage continuous casting mold (same shape, size, and specifications) that does not use a jet nozzle at the same casting speed, and the blow-up state of cooling water was compared.

As a result, as the casting speed increases, the speed of cooling water from the downstream mold gradually increases from 6 m/sec. The blowing up of the cooling water became more intense, and at a cooling water speed of 15 m/sec, it was observed that the cooling water entered the upstream mold.

On the other hand, in the case of the present invention, 200 cp as a highly viscous liquid
When using silicone oil, the cooling water speed is 2.
No blow-out to the upstream mold was observed up to 5 m/sec, but at 25 m/sec or more, the liquid film of silicone oil was broken by the cooling water and turned into a mixture of cooling water and silicone oil, which flowed upstream. It started to blow out into the side mold. Furthermore, when using 3000 cp silicone oil as a highly viscous liquid, the maximum flow rate is 40 m/sec.
Until then, no cooling water was observed blowing up, and it was completely shut off.

As mentioned above, by appropriately selecting a high viscosity liquid,
It is possible to effectively block cooling water from blowing up from the downstream mold.

Furthermore, in the present invention, even when the casting speed was increased, the solidified shell thickness was maintained, and the surface quality of the slab was also good without wear on the downstream mold wall or increase in frictional force.

(Effects of the Invention) As explained above, according to the present invention, it is possible to prevent the mold cooling ability from decreasing due to the voids formed at the end of the wide side of the mold and the lower part of the clamping side, to improve and make the solidified shell formation uniform, and to Improved lubrication prevents severe wear on the mold walls, and also prevents cooling water from the downstream mold from blowing up into the upstream mold, allowing slabs with good surface quality to be produced stably.

[Brief explanation of drawings]

FIG. 1 is a drawing showing an embodiment of the mold of the present invention, FIG. 2 is a side view showing a section of a cooling water guide plate portion, and FIG. 3 is an explanatory view of a jet nozzle. 1 is an upstream mold, 2 is a downstream mold, 3 is a cooling water guide plate, 4 is a cylinder, 5 is a water supply port, 6 is a drain port, 7 is a pressure sensor, 8 is a ring, and 11 is a jet nozzle.

Claims (1)

[Claims] (1) In a continuous casting assembly mold having a rectangular cross section, one or both of the two opposing mold walls are divided into two or more stages in the slab casting direction, and the most upstream side The downstream mold wall other than the mold wall is divided in the slab width direction by a plurality of cooling water guide plates, and the cooling guide plates forming the pair of downstream mold walls are configured to be movable toward and away from each other. A continuous casting mold, further comprising means for press-feeding a highly viscous liquid between the most upstream mold and the downstream mold following the mold.