JPH0366448A - Mold for continuous casting - Google Patents

Abstract

PURPOSE:To stabilize forced cool to a cast slab by forming as dividing one side or both sides of two pairs of mold walls into two or more steps and arranging cooling water passage in most upstream side of the mold at inner face side from backup frame fitting bolt hole. CONSTITUTION:Cross sectional face of the assemble mold for continuous casting is made to rectangle and formed as separating into two steps of upstream side mold 11 and downstream side mold 12. The mold 11 is formed with two pairs of the mold walls. To copper plate 1 constituting the mold wall, plural through-holes are arranged as the cooling water passage 4 and setting position of the through-holes for cooling water passage 4 must be set at the inner wall side of mold from tip part of the bolt hole 3 for fitting backup frame. The downstream side mold wall 12 is constituted as dividing with plural cooling water guide plates 13, and the cooling guide plate 13 is made to shift as attachable/detachable to the cast slab. By this method, the uniform development of solidified sell can be improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a mold for continuous casting, and more specifically, the mold is divided into two or more stages, and furthermore, the mold is formed in two or more stages to prevent breakouts as much as possible. This is related to the mold structure.

(Prior Art) A continuous casting mold usually has a length of 600 to 1200 mm, and the inner wall of the mold is made of a material having high thermal conductivity, such as copper or a copper alloy.

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 surface 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 breakouts 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.

As a mold (equipment) and method for preventing the generation of voids between the mold wall and the solidified shell, we have empirically shown that the inner wall surface (plane) of the mold is inclined inward by an amount corresponding to the average solidification shrinkage rate of the slab in the mold. a mold and method for holding it firmly;
(2) A so-called multi-taper mold and method (Japanese Unexamined Patent Publication No. 125932/1983) have been proposed in which the inner wall of the mold is provided with at least two tapered steps that are continuous in the casting direction. However, with only one or more straight steps of the mold wall and a fixed slope (taper), it is difficult to adapt to the complicated amount of solidification shrinkage that varies depending on various factors such as casting speed, temperature, steel type, etc. It is extremely difficult to bring the solidified shell into contact with the inner wall of the mold while maintaining an appropriate contact surface pressure. It tends to cause severe wear and there are many problems with peeling of the plating layer. Also,■
Either or both of the two pairs of opposing mold walls are divided into two or more stages in the vertical direction, and
A mold in which the lower walls except the uppermost wall are respectively connected to a moving device, and the movable member is provided facing inward of the mold (Japanese Patent Application Laid-open No. 1983-
95451) has also been proposed. In this mold, the lower inner plate, which has an appropriate surface pressure between the slab and the slab, slides back and forth in accordance with the amount of contraction of the slab, thereby reducing the generation of gaps between the slab and the slab. This is designed to prevent abnormal wear on the surface of the lower inner wall plate due to abnormal contact with the pieces. However, as usual, mold powder (Cab-5in) was used as a lubricant on the melted surface in the mold.

- When adding a mixture of base material powder and carbon powder mainly composed of -CaFz-NazO, it does not naturally flow into the gap between the lower mold wall and the slab, so it is difficult to improve the cooling effect of the lower mold and lubricate it at the same time. The improvement in effectiveness is also small.

Therefore, the wear of the lower mold wall is not significantly improved.

On the other hand, as a method of filling the void between the mold wall and the solidified shell with a heat transfer medium to strengthen the cooling of the void, the method is as follows: ■ Powder of graphite, potassium chloride, calcium chloride, sodium chloride, ferrous acid, etc. or by adding rapeseed oil or the like to the mixture and supplying it to the voids (Japanese Unexamined Patent Publication No. 55-92256), and further improving the mixture of graphite particles from the viewpoint of viscosity and thermal conductivity. ■
A method (Japanese Unexamined Patent Publication No. 154351/1982) has also been proposed in which a mixture of vegetable oil (rapeseed oil, etc.) to which 15 to 25% by volume of graphite particles of 1000 mesh or less is added is supplied to the voids. However, these methods of supplying a heat transfer medium have a problem in that, due to poor fluidity, the heat transfer medium cannot reach the fine details of the gaps whose shape changes every moment, and therefore a sufficient heat transfer medium effect cannot be achieved.

Therefore, in view of the above-mentioned points, the present applicant has attempted 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 narrow side of the mold, to promote and make the solidification shell formation uniform, or to improve lubrication. The purpose is to prevent severe wear on the mold walls, and in order to achieve this purpose, one or both of the two pairs of opposing mold walls in a continuous casting assembly mold with a rectangular cross section are cast into slabs. 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. A continuous casting mold characterized in that the respective cooling guide plates are configured to be movable toward and away from each other was proposed in flat-bottomed Patent Application No. 36643.

(Problems to be Solved by the Invention) The continuous casting mold previously proposed by the present applicant is an excellent invention that can achieve the above-mentioned purpose, but subsequent research has revealed the following problems regarding lubrication of the most upstream mold. It turned out that there was an underlying problem.

That is, if ordinary mold powder is simply used as a mold lubricant, its residue will accumulate in the space between the most upstream mold and the downstream mold, or in the space between the downstream molds, or on the inner wall of the downstream mold. The problem of burning occurs. Further problems arise when oil is used as a mold lubricant. In other words, normal oil lubrication is oil (
This is a method in which oil (rapeseed oil, etc.) is supplied from the upper end of the mold to the meniscus along the inner wall of the mold. In this case, the oil is burned in the meniscus, and the carbon produced during combustion acts as a solid lubricant and acts as a lubricant between the mold and the slab. encourage.

However, when casting a wide slab at high speed, it is impossible to uniformly supply oil in the width direction of the slab, that is, to provide uniform lubrication using the above-mentioned normal oil lubrication method.

Any of the above methods will cause problems and
The disadvantage is that operational troubles such as outs are more likely to occur.

The present invention has been made in view of the above points, and adopts the multi-stage mold proposed earlier by the applicant. Second, prevention of deterioration of the quality of cast slabs and resulting operational troubles such as breakouts.Secondly, prevention of the occurrence of residual lubricant used in the most upstream mold and its accumulation and seizing on various parts of the mold, resulting in damage to the downstream mold. Deterioration of forced direct cooling function,
Furthermore, the purpose is to prevent operational troubles such as breakouts caused by this, and thirdly, to prevent operational troubles such as breakouts caused by water flow blown up in the direction of the most upstream mold during forced direct cooling in downstream molds. It was proposed.

(Means for Solving the Problems) In order to achieve the above object, a first continuous casting mold according to the present invention has a continuous casting mold having a rectangular cross section. One or both of the mold walls is divided into two or more stages in the slab casting direction, and the cooling water channel of the most upstream mold is provided on the inner side of the backup frame mounting bolt hole.

In addition, the second continuous casting mold according to the present invention includes the first continuous casting mold.
The downstream mold wall of the continuous casting mold except for the most upstream mold is divided in the slab width direction by a plurality of cooling water guide plates, and each of the cooling guide plates forming a pair of downstream mold walls is divided into two parts. It is configured to be movable toward and away from the slab and tiltable.

Further, the third continuous casting mold according to the present invention includes the second continuous casting mold.
Among the continuous casting molds, air jet blowing holes to the slab surface are provided on the upper inner surface of the uppermost downstream mold or on the lower inner surface of the most upstream mold.

In addition, the fourth continuous casting mold according to the present invention includes the second continuous casting mold.
A roll that comes into contact with the slab is rotatably mounted on the upper inner surface of the uppermost downstream mold or the lower inner surface of the most upstream mold among the continuous casting molds.

Furthermore, the fifth continuous casting mold according to the present invention has the second continuous casting mold.
The air jet outlet of the third invention and the roll of the fourth invention are arranged on the upper inner surface of the uppermost downstream mold or the lower inner surface of the most upstream mold among the downstream molds of the continuous casting mold. That's what I'm doing.

(Function) In the present invention, various improvements have been made to the most upstream mold (indirect cooling method) and the downstream mold (direct cooling method) for the following reasons.

(1) As an indirect cooling method for the most upstream mold, we decided to install the cooling water channel on the copper plate to the backup frame closer to the inner wall of the mold than the tip of the bolt hole for the following reasons. In other words, in a conventional indirect cooling continuous casting mold, the inner wall plate of the mold is made of a material with high thermal conductivity, such as copper or copper alloy, and bolts are attached to a steel backup frame on the outside. The structure is such that it is attached, supported and fixed. For this reason, regarding the arrangement of cooling water channels, as shown in FIG. 5(a), the structure is such that cooling water channel slits 2 and mounting bolt holes 3 are alternately arranged in a copper plate 1 or a copper alloy plate.

However, when the mold with this normal cooling channel arrangement method was put into actual operation, the temperature distribution of the copper plate 1 or the copper alloy plate was as shown in FIG. 5(b). That is, during installation, the copper plate 1 or the copper alloy plate mold wall surface at the position corresponding to the third bolt hole became hotter than other parts, and the mold heat extraction rate became uneven in the width direction of the slab. Further, due to the difference in thermal expansion of the copper plate 1 or the copper alloy plate, a bulging phenomenon is observed in the bolt holes 3 during installation, which further promotes the non-uniformity of the heat removal rate from the mold. As a result, the thin solidified shell became non-uniform in the width direction of the slab, which caused breakout. This is particularly noticeable when the casting speed is 2 m/+++in or more.

Therefore, in the present invention, in order to eliminate this non-uniformity in the rate of heat removal from the mold in the width direction of the slab, the cooling water passage 4 is installed on the mold inner wall side with respect to the bolt hole 3, as shown in Fig. 1 (a). Arranged. By doing this, as shown in Figure 1 (b), the mold heat removal rate in the width direction of the slab is made uniform, thereby preventing vertical cracks on the slab surface, and preventing breakage.
The aim was to prevent outs.

The cooling water channels 4 shown in FIG. 1(A) may be provided in the casting direction as in the conventional art, or may be provided in a direction perpendicular to the casting direction. Further, the shape of the cooling water channel 4 may be any shape such as cylindrical or prismatic (square-hexagonal).

(2) Regarding the downstream mold, the reason why the downstream mold is divided in the slab width direction using multiple cooling water guide plates is because the solidified shell bulges only in the center of the wide side. This is because the gap between the center and end portions can be controlled independently. (1) If a wide cooling water guide plate is used, the distortion due to thermal deformation will be large, making it impossible to control the gap size.

Furthermore, in the present invention, regarding the downstream mold, the second to
A fifth invention has been proposed. All of these are aimed at preventing the high-speed water film flow of the direct cooling method used in the downstream mold from blowing up toward the most upstream mold. By preventing this water flow from blowing up, it becomes possible to drastically reduce operational troubles such as breakouts.

First, the cooling water guide plate can be tilted vertically by making the lower end gap larger than the upper end gap between the cooling water guide plate and the slab, which increases the amount of water flowing toward the downstream side. This is to prevent the cooling water from blowing up from the upper end of the guide plate. +1 oblique angle can be made either on the inside (casting side) or on the outside of the vertical.

This is because the amount of solidification shrinkage of the slab differs depending on the steel type and casting speed, so when the amount of solidification shrinkage is large, the slab is tilted inward, and when there is almost no solidification shrinkage, the slab is tilted outward.

In addition, as a method to prevent the high-speed water film flow from blowing up, there is a method in which the water flow is blocked by blowing an air jet from the lower end of the most upstream mold or from the upper end of the cooling water guide plate in the downstream direction of the above-mentioned gap. We thought that a method of mechanically blocking the water flow by arranging a roll at the upper end of the tank would be relatively simple and practical.

According to the present invention having the above configuration, uniform heat removal is made possible in the most upstream mold, which dramatically increases the ability to generate a uniform solidified shell in the most upstream mold. How to uniformly exert the forced direct cooling function of the cooling water guide plate (because it is possible to keep the speed of the high-speed water film flow uniform from the top to the bottom end of the cooling water guide plate), and also prevent the water film flow from blowing up. This makes it possible to significantly reduce operational troubles such as breakouts due to

(Example) The present invention will be described in more detail below based on the accompanying drawings.

FIG. 2 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 11 and a downstream mold 12.

Of these, the upstream mold 11 usually has a tapered mold wall or two pairs of opposing parallel mold walls. As shown in Fig. 1, a plurality of through-holes are provided, and the position of the through-hole for the cooling water channel 4 must be particularly uniform by arranging it closer to the inner wall of the mold than the tip of the bolt hole 3 for attaching the backup frame. It is a mold that functions to remove heat. By the way, the size of the through hole which is the cooling water channel 4,
Although the shape (cylindrical, prismatic, etc.) and arrangement pitch are not particularly limited, in order to ensure a uniform heat removal rate in the width direction of the slab and to generate a uniform solidified shell. By making the through-hole arrangement pitch near the corners coarser than the through-hole arrangement pitch at the center of the width,
More reliable and uniform heat removal is possible. Note that there is no problem with the direction in which the through holes as the cooling water channels 4 are arranged, either in the casting direction or in a direction perpendicular to the casting direction.

On the other hand, the downstream mold 12 is composed of a plurality of cooling water guide plates 13 each having a rectangular shape as shown in FIG. 3(A) or a tortoiseshell shape as shown in FIG. The cooling water guide plate 13 is connected via a link 18 so that the mold wall surfaces forming a pair can move toward and away from each other, and auxiliary cylinders 19 are provided at the upper and lower ends of the cooling water guide plate 13. It is designed so that it can be tilted in the opposite direction.

Figure 3 shows the cooling water guide plate 1 that constitutes the wall of the downstream mold 12.
3, the provisional cooling water guide 13 is provided with 15 rows of water supply ports and 16 rows of drain ports alternately, and the pressure is detected by pressure detectors 17 provided in the water supply section and the drainage section. However, each cooling water guide plate 13 can be moved by the cylinder 14 according to this detected value.

Furthermore, in the present invention, an air jet is provided at the upper end of the cooling water guide plate 13 in order to prevent cooling water from blowing up from the downstream mold in the direction of the upstream mold 11 and to prevent operational troubles such as breakouts caused by this. Air jet blowout hole 21. Alternatively, a roll 22 may be provided to shut off the cooling water.

In addition, by making at least one of the water supply port 15 and the drain port 16 into a slit-like long hole as shown in FIG. 3(A), the water film formed between the slab 20 and the cooling water guide plate 3 Achieves uniform flow of cooling water within the tank.

Next, the effect of the present invention is %I U'! We will explain the results of experiments conducted to achieve this goal.

4 to 10 m of low carbon aluminum killed steel weighing 50 tons per heat
A slab having a thickness of 105 mm and a width of 11,050 ff1 was produced using a continuous casting machine equipped with a two-stage continuous casting mold shown in FIG.

The length of the upstream mold used at this time was 350 ms (length 250 mm below the meniscus), and the downstream mold was equipped with a strip-shaped guide plate (width: 100 ms) as shown in Figure 3 (A).
22 pieces (1 m, length: 550 mm) were attached.

The details of the cooling channel of the upstream mold are shown below.

[Details of the through holes that make up the cooling channel of the upstream mold] ■
Installation position of the through hole Distance f2 from the mold surface to the center of the through hole: 15 m Width direction casting pitch P: 19 m Through hole installation direction: Casting direction ■ Through hole size Cylindrical hole, diameter d: 10 mm φ In this way, during casting, the cooling channel penetrates Casting was performed by supplying cooling water to the holes at a flow rate of 9 m/s.

(Details of the water supply port and drain port on the cooling water guide plate) ■Water supply port:
Height 1.5aa x Width 12m ■Drain port: Height 2.2m + Ax Width 12M ■Mutual spacing between water inlet and drain port: 2 Inll each ■ Distance between water inlet row and drain port row: 50 cabinets ■ Cooling water guide plate slope Angle θ−
0.1 degree (horizontal distance between upper and lower ends 1.0 mob) Air jet blowout: Height 1.0 aa x Width 90 m During casting, the average water film thickness δ was maintained at 0.5 mm. Then, casting was carried out with the cooling water flow rate in the range of 10 to 15 m/s.

Figure 4 shows the occurrence of breakouts as an indicator of operational trouble. The difference between the method of the present invention and the conventional method becomes more pronounced as the casting speed increases, and the casting speed is 4 m/win.
In this case, the breakout rate is lower than that of the conventional method.
/20 or less.

(Effects of the Invention) As explained above, according to the present invention, the uniformity of solidified shell formation in the upstream mold is improved and the slab is strongly cooled and stabilized in the downstream mold, and as a result, these The synergistic effect enables stable high-speed casting of 4 m/++in or more.

[Brief explanation of drawings]

Figure 1 (a) is a plan view showing an example of the most upstream mold main part constituting the mold of the present invention, (b) is a diagram showing the temperature distribution of the copper plate during casting, and Figure 2 is the mold of the present invention. FIG. 3 is a cross-sectional front view of one embodiment of the invention, and FIG. 3 is an explanatory diagram of the cooling water guide.
(A) is an enlarged front view of the upper left part of the strip-shaped guide plate showing the first embodiment; (B) is a front view showing the main part of the second embodiment;
(C) and (D) are cross-sectional side views, Figure 4 is a diagram of the experimental results, and Figures 5 (A) and (B) are Figure 1 (A) of the conventional mold.
This is the same drawing as (b). 4 is a cooling channel, 11 is an upstream mold, 12 is a downstream mold,
13 is a cooling water guide plate, 14 is a cylinder, 18 is a link, 19 is an auxiliary cylinder, 21 is an air jet outlet, and 22 is a roll. Figure 1 (a) 2nd:! . (hey)

Claims (5)

[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 A mold for continuous casting, characterized in that the mold cooling channel is provided on the inner side of the backup frame mounting bolt hole. (2) The downstream side mold wall of the continuous casting mold according to claim 1, except for the most upstream side mold, is divided in the slab width direction by a plurality of cooling water guide plates to form a pair of downstream side mold walls. A mold for continuous casting, characterized in that each of the cooling guide plates is configured to be movable toward and away from the slab and tiltable. (3) the lower inner surface of the most upstream mold according to claim 1, or
3. A continuous casting mold, wherein the uppermost downstream mold of the downstream mold according to claim 2 is provided with an air jet blowing hole to the surface of the slab. (4) A mold for continuous casting, characterized in that a roll that contacts the slab is rotatably mounted on the upper inner surface of the uppermost downstream mold among the downstream molds according to claim 2. (5) A continuous mold, characterized in that the air jet outlet according to claim 3 and the roll according to claim 4 are arranged on the upper inner surface of the uppermost downstream mold among the downstream molds according to claim 2. Casting mold.