JPH04200957A - Mold for horizontally continuous casting - Google Patents

Abstract

PURPOSE:To prevent the generation of the recess on the surface of the cast billet by setting the groove in the direction parallel with the casting direction on the inner surface of the mold. CONSTITUTION:The mold 4 has a small tapered part and a brake ring 3 is inserted in it. Plural lines of grooves in parallel direction with the casting direction are set on the inner surface of the mold 4. In order to rapidly cool and solidify the shell flowing in the groove, the distance L between the triple point (the contact point of the mold 4 and the brake ring 3) and the start point 7A of the groove in the casting direction is made more than the same length as width W of the groove 7, less than the stroke S of pulling. Therefore, in the pulling time of the shell, the molten steel flows in to the groove, is rapidly cooled and solidified in the groove, the strong shell is generated and also the regular solidification is progressed, so the generation of the pressure loss of molten steel in the tundish nozzle and the backling of the shell or the deflection is prevented, and the generation of recess of the casting billet is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a mold for horizontal continuous casting, and more particularly to a mold that can prevent dents from occurring on the surface of a cast slab.

[Prior art] As a method of drawing force of slab in horizontal continuous casting method, 0)
The fixed mold-intermittent pulling method involves fixing the mold and moving the casting piece in a pattern of e.g., pulling out, standing still, and pushing back. There is also the vibration-gb)'+continuous drawing method1.In either method, negative pressure is generated in the solid-molten steel part of the mold due to Ll-force loss in the tongue tissue nozzle when the slab is pulled out. This negative pressure acts on the initially solidified shell portion, which has low hot strength, causing the slab to dent. In particular, since gravity is applied to the surface of the slab, this denting tends to be promoted. When a dent occurs in a cast slab, if cracks occur along the dent, it is necessary to remove the dent on the surface and remove the cracks in the dent. In addition, the above-mentioned tundish:
As a step forward, there is a method of shortening the length of the tandem nozzle and increasing the inner diameter, but this poses structural problems and is not a drastic solution.

An example of providing a plurality of slit l-grooves on the inner surface of a horizontal continuous casting mold is known from, for example, Japanese Utility Model Application No. 60-5166 () and Japanese Patent Application Laid-open No. 6:'l-10045. The purpose of the stiffness mentioned above is to reduce the wastage of the mold.In other words, the mechanism of mold wear is due to the solidification of molten steel.7.II':';
It is presumed that the impurities in the mold evaporate, and the impurities accumulate near the solidification start point of the mold, causing chemical damage to the mold.As a countermeasure, the mold is The inner surface has multiple grooves that communicate with the outside air. Therefore, the position and shape of the groove are designed so that molten steel does not enter the groove and block ventilation with the outside air. However, with these first and second means, no effect of preventing the formation of dents on the surface of the slab, as will be described later, is observed.

[Problems to be Solved by the Invention] Therefore, the present invention provides a horizontal continuous casting method in which jJF
To prevent the occurrence of dents on the surface of cast iron, and to omit part of the surface hair-filling work of the dents.

[Means for Solving the Problems] In order to solve the above problems, the present invention has a structure in which, in a horizontal continuous casting mold connected to the side wall of a tundish via a refractory ring, the inner surface of the mold is A plurality of grooves are provided in a direction parallel to the casting direction, and the distance between the starting point of the groove and the point of interest is within the range of 1 width of the opening minus 1 withdrawal stroke, and the end point of the groove is the exit end of the mold. It is characterized by A preferred embodiment of the present invention is characterized in that the opening LI width and depth of the groove are each 80 μm or more.

[Function] Generally, in the horizontal continuous casting method, a horizontally arranged mold is connected to the side wall of the tongue tissue, and a refractory ring (hereinafter referred to as a break ring) is provided on the entrance side of the mold. This break ring serves to control the initial solidification initiation device i' to be uniform in the circumferential direction of the mold. In other words, in the conventional vertical continuous casting method, the position of the molten metal surface was necessarily the initial solidification position, whereas in the horizontal continuous casting method, the molten metal was poured into the tank via the mold or tandate nostle. Because it is installed horizontally on the tissue,
Initial solidification begins at the entry end of the mold (break ring region), which is internally water-cooled. The solidification start position is not uniform around the mold due to the temperature difference between the molten steel in the mold (+'7), the flow rate of the molten steel supplied into the mold, and the gradual fluctuation of the cooling temperature due to the mold. 4 of the initial solidification shell
1-If the structure is non-uniform in the same circumferential direction, the shell will break and the failure will occur.

A dent occurs in the solidified area. Therefore, in order to stably cast water using the continuous casting method 1 and obtain slabs with good surface properties, it is extremely important to control the solidification start position. Therefore, in the horizontal continuous casting method, an insulating break ring is provided at the entrance of the mold in order to control the solidification start position.

For example, as a drawing method for the water/t continuous casting method,
In the example of intermittent drawing of casting IF and lJ, solidification starts at the break ring provided at the inlet end of casting IF and lJ, but drawing is performed when a certain amount of shell is formed, and
At the drawing point A in the figure, molten steel flows between the break ring 3 and the previously generated shell 5b, as shown in FIG. It progresses from solidification to solidification. After performing the drawing for a predetermined stroke and a predetermined time, the drawing is stopped, and during this stationary period (drawing time B in Fig. 6), new molten steel is drawn in the area where new molten steel has flowed due to the drawing. A shell is formed. However, "at first glance, brake ring 3
Although the initial solidification position can be made uniform, microscopically, the difference in the flow of molten steel that occurs near the break ring 3 (
For example, in the casting of a square bloom, the difference between a corner part and a face part) and a slight deviation in the arrival time of molten steel to the tip of the shell due to drawing of the cast member cause non-uniform formation of the initially solidified shell 5a. This non-uniformly generated portion is the starting point of surface defects such as the depression 9 shown in FIG. 5(B).

The feature of this invention is that a plurality of grooves are provided in the inner surface of the mold in a direction parallel to the casting direction, and molten steel is forced to flow into the grooves to forcibly generate a solidified shell along the grooves. be. The reason why this invention prevents dents in slabs is that by solidifying regularly in the grooves, an initial solidified shell is uniformly generated, and further, by rapidly solidifying in the grooves, the strength of the shell can be increased. By,
The purpose is to ensure an initial solidification state in which only the pressure loss of the molten steel in the tundish nozzle and buckling and deflection of the shell due to the shell's own weight occur.

[Examples] Examples of the present invention will be described in detail below with reference to the drawings. Figure 4 shows an example of a horizontal continuous casting apparatus. One end of the mold 4 is connected to the side wall 18 of the tongue tissue 1 via the nozzle 2, and a break ring 3 is inserted into the side of the mold. The molten steel M that has flowed into the tundish 1 is introduced into the mold 4 and solidifies in the mold 1 and 4. The solidified slab 9 is intermittently pulled out by the pulling device 6.

FIG. 1 shows an example of the mold according to this embodiment. The mold 4 has a small taper at its entry end, into which the break ring 3 is inserted. The inner surface of the mold 4 is provided with a plurality of grooves 7 (6 grooves per surface in the figure, 16 grooves in total) in a direction parallel to the casting direction. The reason why the groove 7 is provided in the mold is that, as shown in Fig. 5(C), when the shell is drawn, molten steel flows into the groove 7 and is rapidly solidified in the groove 7, thereby forming a strong shell 5C. This is to make it 4F. The shape of the groove 7 should be at least large enough to allow molten steel to flow in, and it is desirable that the width and depth are both 80 μm or more. If the groove 7 is too large, it will be necessary to remove the protruding shell generated by the groove 7.
The width (W>) and depth (D) of the groove 7 shown in the figure are preferably 2 mm or less. In order to more rapidly solidify the shell flowing into the groove, the l-point 8 (
The distance (L) between the contact point between the mold 4 and the break ring 3) and the starting point 7A of the groove in the casting direction is equal to and less than the width (W) of the groove 7, and less than or equal to the drawing stroke (S). There is a need.

The reason is that if the distance (1,) is shorter than the width W of the groove 7, the shell 5C1 solidified in the groove 7 one stroke before
Since the molten steel M1 newly flowing into the groove 7 in FIG. 5(C) flows (for example, 5d) and connects with each other before it solidifies, the rapid solidification effect is impaired. If the distance (1,) is greater than the drawing stroke, molten steel will not flow into the groove 7, and the targeted shell cannot be strengthened. distance 11
! If t(+,,) is within the range of +ff, the distance (1,) for multiple grooves should be calculated by taking into account the slight time lag in the flow of molten steel into the tip of the shell when drawing the slab. It can also be changed.

The end point 713 of the groove is located at the outlet end 41 of the mold 4 so that the shell can pass smoothly through the groove.

In this example, the starting point 7A of the groove 7 is set at a position 2 mm111 away from the point 8 in the casting direction, and the width of the groove (W) -
The depth (D) was 0.4 mm and the depth (D) was 0.6 mm. The number of grooves 7 was set at 10 mm intervals. - As shown in FIG. 7, the results obtained in Example 1 were able to significantly reduce the dents on the surface of the slab by providing grooves on the inner surface of the mold.

In the following explanation, an example of a mold with a rectangular cross section has been given, but the present invention can also be applied to molds with a round cross section.

[Effects of the Invention] According to the present invention, a groove is provided in the inner surface of the mold in a direction parallel to the casting direction, so that molten steel flows into the groove when the shell is pulled out, and is rapidly solidified in the groove. A strong shell is formed and regular solidification progresses, which prevents hackling or bending of the shell due to the pressure loss of the molten steel in the tundish nozzle and the shell's own weight, and almost eliminates the occurrence of dents in the slab. It is possible to have none at all.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the mold according to the present invention, and FIG.
The figures are A-A parent diagram of Fig. 1, Fig. 3 is a cross-sectional view of the groove provided on the inner surface of the mold, Fig. 4 is a vertical cross-sectional view showing the overall configuration of the horizontal continuous casting apparatus, and Fig. 5 (A ) and FIG. 5(B) are longitudinal sectional views showing the state of solidified shell formation in a general horizontal continuous casting method, and FIG. 5(C) is a longitudinal sectional view showing the state of solidified shell formation in this example. FIG. 6 is a diagram showing an example of a drawing pattern, and FIG. 7 is a diagram 1-1 showing the effect of the embodiment. 1... Tan tissue, 2... Tan dish nozzle, 3... Break ring (refractory ring), 4...
... Mold, 5... Shell, 6... Pulling device, 7...
・Groove, 8... Triple point, 9... Agent for slab holding permit applicant

Claims (1)

[Claims] 1. A horizontal continuous casting mold (
In 4), a plurality of grooves (7) are provided in the inner surface of the mold (4) in a direction parallel to the casting direction, and the distance (L) between the starting point (7A) of the groove (7) and the triple point (8) is set as the groove. opening width (W) or more,
A mold for horizontal continuous casting, characterized in that the range is equal to or less than the drawing stroke (S), and the end point (7B) of the groove (7) is the mold outlet end (4B). 2. The horizontal continuous casting mold according to claim 1, wherein the opening width (W) and depth (D) of the groove (7) are each 80 μm or more.