JPH0270358A - Mold for continuous casting - Google Patents

Abstract

PURPOSE:To reduce the development of depression and longitudinal crack in continuous casting for the specific steel by arranging plural recessed parts to the position corresponding to water passage at front face of mold copper plate having the water passage at back face. CONSTITUTION:The water passages 1a are formed at the back face of the mold copper plates 1 and the back plates 2 are fitted. At the front faces of this copper plates 1, the continuous casting mold is formed. Then, at the position corresponding to the water passages 1a at the front faces of the mold copper plates 1, plural vertical grooves 1b as recessed parts for preventing uneven cooling to the width direction of the mold copper plates 1 are arranged. By this method, the development of the depression and longitudinal crack can be reduced in the continuous casting of the steel containing peritectic reaction range, for example, SUS304, etc.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a continuous casting mold, and in particular, to an effective method for reducing casting defects such as surface cracks that occur in slab strands due to uneven cooling of molten metal within the mold. This is what we are trying to avoid.

(Prior Art) The following documents are referred to as prior art that attempts to improve continuous casting molds in order to avoid casting defects that are feared to occur in continuous casting of steel.

・Prior art-1 (Japanese Patent Publication No. 57-11735) A diameter or width of 2.5 mTO is installed on the front or part of the inside of the mold.
A continuous casting mold having a large number of concave portions having a ratio of 20% to 90% of the total area (see FIG. 16).

・Prior art-2 (Japanese Unexamined Patent Publication No. 61-180649) A vertical groove is provided in the center of the long side of the mold, and an inclined groove is provided in the contact area with the short side of the mold, and each of these grooves has a depth of 0.3 mm or more. , width 2. Continuous casting mold with a pitch of 5.0 or less and a pitch of 5.0 or less (see Figure 17).

・Prior art-3 (Japanese Unexamined Patent Publication No. 61-92756) Width 250 along the casting direction within 300 mts from the upper end of the mold
~750 μm, depth 60-300 μm 1 area ratio 20-9
Continuous casting mold with grooves that meet the 0% condition (No. 18)
(see figure).

・Prior art-4 (Tetsu to Hagane: No. 68, No. 4 (1982)
), 5159) Continuous casting mold (
(See Figure 19).

・Prior art-5 A continuous casting mold (see Fig. 20), which is equipped with a spacer in the rear slit portion of the area corresponding to the meniscus of the copper plate mold to strongly cool the copper plate and slab in that area.

(Problems to be Solved by the Invention) 1) Regarding uniform slow cooling during continuous casting, all of Prior Art 1 to 4 have a structure in which grooves etc. are processed on the surface of the mold copper plate, resulting in slow cooling as a whole ( However, cooling of the mold copper plate in the lateral direction was uneven, making it difficult to achieve uniform slow cooling. Therefore, cracks occur on the surface of the slab strand due to the uneven formation of shells, which becomes an impediment to hot charging, direct rolling, etc., and is a major hindrance to realizing maintenance-free steel with a peritectic reaction zone. This was a contributing factor.

2) Regarding uniform strong cooling during continuous casting, low-carbon aluminum killed steels are generally mass-produced steels, and high-speed casting is performed for such steels due to their low sensitivity to cracking, especially longitudinal cracking. . Therefore, in order to ensure a sufficient shell thickness at the lower end of the mold, various strong cooling measures have been taken, such as extending the mold copper plate, making the mold copper plate thinner, or increasing the amount of cooling water supplied for cooling the mold copper plate. However, in conventional continuous casting molds, as the mold copper plate is strongly cooled, the degree of non-uniform cooling increases, resulting in fine vertical cracks on the subscale surface of the slab, which poses a problem during direct rolling.

In particular, in a structure using a spacer as in Prior Art 5, by reducing the cross-sectional area of the cooling water passage,
Strong cooling is possible because the linear velocity of cooling water in the slits increases, but the difference in cooling capacity between areas with cooling slits and areas without cooling slits is further expanded, so the temperature difference on the surface of the slab (amplitude Δ
T) becomes large, and surface defects such as vertical cracks are likely to occur.

It is an object of the present invention to propose a mold for continuous casting that can realize uniform cooling and advantageously avoid casting defects such as vertical cracks.

(Means for Solving the Problems) The present invention includes a mold copper plate having a water passageway on the back surface and forming a continuous casting mold on the front face thereof, and a mold copper plate with a width corresponding to the water flow passageway on the front surface of the mold copper plate. This continuous casting mold is characterized by having a plurality of concavities and convexities that prevent non-uniform cooling in the direction.

Now, FIGS. 1(a) and 1(b) show schematic diagrams as an example of a continuous casting mold according to the present invention. In the figure, 1 is a mold copper plate forming a continuous casting mold, and the back surface of this mold copper plate 1 is shown in FIG. It is provided with a water passage 1a and a plurality of vertical grooves 1b at positions corresponding to the water passage on the front surface thereof. Reference numeral 2 denotes a back plate that fixes and holds the mold copper plate 1 via mounting bolts 2a.

(Function) The surface temperature of the slab becomes non-uniform in the width direction in the areas where the water passage 1a formed on the back surface of the mold steel plate 1 is present and the area where it is not, as shown in FIGS. 2 and 3, for example. Even if grooves as shown in FIG. 4 are provided over the entire surface of the copper mold plate, the absolute value of the surface temperature only increases, and it is very difficult to reduce the temperature amplitude.

Therefore, in this invention, as an example, a plurality of vertical itb are provided on the surface of the mold copper plate in the area where the water passage 1a is provided, and an air gap A is provided only in the area of this groove during continuous casting, for example, as shown in FIG. Uniform cooling was achieved by reducing the amount of heat removed from the slab corresponding to that area.

FIGS. 6 to 10 show other examples of continuous casting molds according to the present invention, together with the surface temperature distribution of the slab at that location. In particular, local supercooling in the width direction of the mold copper plate 1 is prevented. If possible, grooves (in this case, the groove size will be small) may be provided on the surface of the copper plate in areas where there is no water passage 1a, and in this case it is advantageous to perform uniform slow cooling.

The size (depth, width, pitch) of the groove 1b provided on the surface of the copper mold plate may be set to W' that satisfies the following conditions (see FIG. 11).

■ w<w'<W W: Width of water passage (+y++n) W': Formation range of groove (mm) W: Pitch of water passage (mm) Here, for example, if W = 35 mm and w = 5 mm, 5 (+yun) <w'< 35 (mm) if the condition (2) is satisfied. In short, water passage 1a
It is only necessary that the surface area per unit length on the surface of the mold copper plate at the portion provided with is larger than that in other areas.

FIG. 12 is a graph showing the relationship between the amount of heat removed from the mold copper plate 1 and the temperature difference ΔT on the slab surface when the continuous casting mold according to the present invention is used. The temperature difference ΔT of the slab is extremely stable at 2 to 5 degrees Celsius on the slow cooling side and 4 to 8 degrees Celsius on the strong cooling side, whereas in Fig. 13, which shows an example of a conventional continuous casting mold, The temperature difference ΔT on the surface of the slab was 30 to 80°C.

In the above example, there are multiple ! <K
Although the explanation has been made on the case where the vertical grooves are provided, it goes without saying that the same effect can be obtained by using horizontal grooves, parallel grooves, shore blasting, etc. instead of the vertical grooves.

(Example) Width (w
'> Vertical grooves with a groove depth of 1ml11, a groove width of 0.8+++m, and a pitch of 1.5fflI11 so that the slab surface temperature is uniform in the width direction over a range of 10 mm (500 μm N! plating after groove machining, 50 more
Continuous casting was carried out using a mold having a structure as shown in FIGS. 14 and 15, which was coated with μm chrome plating.

As a result, the surface temperature of the slab in the width direction is almost stable, and there are no problems such as vertical cracks or unevenness (depression) on the slab surface.
It was confirmed that because the shell is uniformly reinforced, restraint breakouts and the like are also reduced.

In particular, the mold shown in FIG. 15, in which the spacer 6 was provided in the water passage 1a, enabled strong uniform cooling.

(Effect of the invention) According to the present invention, a steel including a peritectic reaction region, for example, 5us
304.5us430.5us420J, [:+1
It can reduce depressions and vertical cracks in 2XIO-3% ordinary steel, etc. and greatly increase the maintenance-free ratio.

Furthermore, according to the present invention, cracking defects can be reduced even in continuous casting of low carbon aluminum killed steel, etc., so the amount of scale-off can be reduced, and low-temperature heating has become possible.

[Brief explanation of the drawing]

Figures 1 (a) and 4 (b) are explanatory diagrams of the structure of a continuous casting mold according to the present invention, and Figures 2, 3, and 4 are cross-sections of main parts of the continuous casting mold and the shape of slabs in these parts. Figure 5 is a diagram showing the surface temperature distribution; Figure 5 is an explanatory diagram of the casting situation; Figures 6, 7, 8, 9 and 10 are cross-sections of main parts of the continuous casting mold according to the present invention; Figure 11 is a diagram showing the temperature distribution on the slab surface at different locations, Figure 11 is an explanatory diagram of the groove formation procedure, Figures 12 and 13 are graphs showing the relationship between the temperature difference ΔT on the slab surface and the amount of heat removed from the mold copper plate. Figures 14 and 15 are cross-sections of essential parts of the pond continuous casting mold according to the present invention, and diagrams showing the temperature distribution on the surface of the slab in these parts; Figures 16, 17, 18, and 19; Figure and 20th
The figure is a schematic diagram of a conventional molded copper plate, and FIG. 21 is a graph showing the relationship between the temperature difference ΔT on the slab surface and the amount of heat removed from the molded copper plate. 1... Mold copper plate, 1a... Water passage 1b...
・Vertical groove 2...Back plate 2a...
・Mounting bolt 3... Shell 4... Powder 5... Molten steel 6... Spacer

Claims (1)

[Claims] 1. Equipped with a mold copper plate that has a water passageway on the back side and forms a continuous casting mold on the front side thereof, and has a plurality of unevenness on the front surface of the mold copper plate at a position corresponding to the water flow passageway to prevent uneven cooling in the width direction of the mold copper plate. A continuous casting mold characterized by being provided with.