JPS61154750A - Continuous casting method - Google Patents

Abstract

PURPOSE:To assure the temp. at slab edges to decrease the incorporation rate of coarse particles and to produce a product having good quality by casting the slab without allowing the edges thereof to contact with the rolls of a continuous casting machine. CONSTITUTION:A molten steel is poured into a mold 1 and a hot slab 2 emerged from the outlet side A of the mold is cooled and supported by roll groups 3 and is guided to the discharge side B of the continuous casting machine. The spacing between the rolls 3a and 3b is adjusted at the point C as shown by the line II between, for example, the point A right under the mold and the point B on the discharge side in the continuous casting machine and is thereby expanded to generate a spacing between the slab edges 2c and the rolls 3 to cast the slab without allowing the edges 2c to contact with the rolls 3a and 3b. The temp. difference between the slab edges 2c and the center 2d is thus decreased at the point B, by which the generation rate of the coarse particles owing to the overcooling of the edges is decreased and the quality of the rolled product is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for continuous casting of steel. It has become popular as the steel types that can be applied to it have been expanded.

The continuous casting ratio of steel is on the verge of reaching 95% or more, especially since it is advantageous in terms of improved casting yield, resource saving, and energy saving.

Furthermore, in order to improve productivity, progress is being made toward a direct steelmaking-rolling process, that is, direct rolling, which expands and expands the superiority of the continuous casting method.

In this case, it is required to cast and supply defect-free and stable high-temperature slabs at high speed.

That is, the method of reducing the fuel consumption of the heating furnace by rolling the cast slag as a hot piece or charging it into a heating furnace has been widely known as a technique between continuous casting and rolling.

In this case, the problem is that when rolling the hot slab that comes out of the continuous casting machine, the slab edge part is the part that first undergoes IC solidification in the continuous casting machine, and is far away from the final solidification part of the slab in the continuous casting machine. Therefore, recovery cannot be expected. As a result, the temperature difference ΔT at the slab edge is approximately 200°C lower than that at the center of the slab on the exit side of the continuous casting machine, as shown in Figure 7. When directly rolled under these conditions, the structure is coarse due to the low temperature at the slab edge. As shown in the relationship between the edge temperature and the coarse grain mixing rate in Figure 8, the coarse grain mixing rate (the area amount of the slab edge portion) increases as the temperature decreases.
Deterioration in elongation occurs due to the material.

For this reason, the conventional methods have been to change the fill at the discharge end of the continuous casting machine or to reheat the edge portion. However, direct rolling of high-speed continuous casting-rolling poses an obstacle to stabilizing quality, and a solution to this problem has been desired.

[Problem that the invention seeks to solve]

The present invention reduces the temperature difference ΔT between the edge part temperature of a slab piece and the center part of the slab in the continuous casting method, increases the edge part temperature, and when directly rolled, the slab (coil)
The purpose of the present invention is to provide a continuous casting method for manufacturing high-quality products by reducing the mixing rate of coarse particles at the edges.

[Means for solving problems]

In the continuous slab casting method, a roll (guide roll or nib blower) is generally used immediately after the mold.
), the slab is cooled and supported. Continuous casting rolls such as these are generally those in which a spiral water-cooled groove is cut into the roll shaft and a sleeve with a flat outer surface is fitted over the roll shaft so that the two are integrated, or the two are integrated into a roll shaft with a spiral water-cooled groove cut into the roll shaft. A type in which a water cooling groove is formed through the groove and a sleeve with a flat outer surface is fitted over the groove to integrate the two is used.

The present inventor investigated the heat removal mechanism of the cooling support guide roll immediately below the mold and arrived at the present invention.

In the present invention, when a hot slab is charged into a heating furnace for rolling after casting and directly rolled, the roll of the continuous casting machine is not brought into contact with the edge of the slab in order to ensure the temperature of the edge of the slab. The object of the present invention is achieved by reducing heat loss to the casting.

That is, the present invention is a continuous casting method characterized in that the slab edge portion is cast without coming into contact with the rolls of a continuous casting machine. It is a means to do so.

[For production]

Figure 1 shows the glofil of the continuous casting machine. In Fig. 1, 1 is a mold, 2 is a slab, and 3 is a roll. Molten steel in a ladle is injected into the mold 1 via a tundish, and is discharged from the mold. The continuous casting machine is cooled and supported and guided to the discharge side B of the continuous casting machine.The distance between the rolls during casting in the longitudinal direction of the continuous casting machine (the distance between the upper roll 3m and the lower roll 6b) is the second
It becomes as shown in (I) in the figure.

That is, the hot piece slab 2 in the conventional method is cooled and solidified while being cooled and guided and supported by the rolls 3 in the continuous casting machine, and subjected to primary and secondary cooling by the combination of spray between the rolls. and 6b is adjusted and reduced as shown in FIG. The roll spacing can be adjusted by using 6b, which is supported on a fixed shaft, and 6b, which is supported on a movable shaft.
A is performed by adjusting the upper roll 6a by, for example, hydraulic pressure. The state of the slab between the rolls 6a and 6b in this case is as shown in FIG. 5, but in this case, the temperature difference ΔTFi between the slab edge portion 2C and the slab center portion 2d at eight points on the discharge side of the continuous casting machine is as shown in FIG. 200 as shown in
As shown in FIG. 8, when rolling is carried out at a temperature of 10.degree.

The present invention applies to the inside of a continuous casting machine, for example, in FIGS. 1 and 2.
Between point A directly under the mold shown in the figure and point B on the discharge side, the width is widened by adjusting the distance between the rolls 3a and 3b at point 0 (as shown in Figure 10) in Figure 2, and as shown in Figure 4. As shown, a gap is created between the slab edge portion 2C and the roll 3, and the slab edge portion 2C is connected to the rolls 6a and 3.
It is cast without contact with b.

That is, the present invention makes it possible to prevent heat loss to the rolls by not allowing the slab edge portion 2C to come into contact with the roll 3. This reduces the temperature difference ΔT between the slab edges and raises the temperature of the slab edge portion 2C by approximately 40°C compared to the conventional method.As a result, in direct rolling, the temperature of the slab (coil) center 2d and the edge portion 2C after hot rolling is As shown in Figure 6, it was possible to reduce the roughness by about 10~b compared to the conventional button.As a result, it was possible to reduce the generation rate of coarse grains due to overcooling of the edge part, making it possible to improve the quality of rolled products. .

〔Example〕

Continuous casting machine is busy, width 750-1600m thickness 220m
Casting slabs of ~225 parrots 1-2.5”/.

Continuous casting was carried out under the following conditions: in this case, the roll spacing was adjusted as shown in FIG. As a result, it was confirmed that the temperature difference ΔT between the slab edge 2C and the central part 2d at the discharge end B of the continuous casting machine was 160°C as shown in Fig. 5.The slab ( (coil) The temperature difference between the center and the edge part is as shown in Figure 6, and the edge part temperature has increased by 15 degrees Celsius compared to the conventional coil.As a result,
The ratio of coarse grains in the edge portion after rolling was also reduced, and there were no problems with the material quality. Furthermore, as a result of being able to prevent heat loss to one roll, it has become possible to reduce fuel consumption by 60 to 40%.

〔Effect of the invention〕

According to the continuous casting method of the present invention, in order to reduce the temperature difference between the slab edge part and the center by appropriately cooling the slab edge part and increase the temperature, the ratio of coarse grains in the edge part after rolling in direct rolling is reduced. It was possible to roll a product with no material problems.

The present invention is a useful continuous casting method that makes direct rolling production more efficient and reduces fuel consumption.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a continuous casting machine, Figure 2 is an explanatory diagram showing the roll spacing in the longitudinal direction of the continuous casting machine, Figures 6 and 4.
The figures are schematic diagrams showing the state of the slab between rolls in the conventional method and the present invention, respectively. FIG. 5 is a temperature distribution diagram in the width direction of the slab in the present invention. FIG. 6 is a slab (coil) of hollow rolling in the present invention and the conventional method. FIG. 7 is a temperature distribution diagram in the slab width direction in the conventional method; FIG. 8 is an explanatory diagram showing the relationship between slab edge temperature and coarse particle mixing rate in the conventional method. Figure 1: mold, 2: slab, 2C varnish slab joint part, 2d varnish slab central part, 515&. 6b Two rolls, A: Mold exit side, B: Continuous casting machine exit side, C: Roll interval expansion point ◇ Note that the same symbols in the drawings indicate the same or the same function. Agent Masashi Sanro Kimura Figure 2? J4 figure 5 rg figure 6 figure 7 figure 7 engineer, Te 7 history figure 8 - e, → 1 yujun - also

Claims (2)

[Claims] (1) A continuous casting method characterized by casting the slab edge portion without contacting the roll of a continuous casting machine. (2) The continuous casting method according to claim 1, characterized in that the distance between the rolls is adjusted and the distance between the rolls is once widened midway through the continuous casting machine.