JPS61235049A - Nozzle for continuous casting - Google Patents

Abstract

PURPOSE:To prevent the C pickup contamination of an extra-low C steel by forming a titled nozzle into the two layers consisting of the fused silica used to constitute the inside where the nozzle does not contact with slag on a molten metal surface and the alumina graphite used to constitute the outside in contact with the slag. CONSTITUTION:The outside 12 of the immersion nozzle 1 where the nozzle contacts with the slag is made of the alumina graphite in order to obviate the increase in the erosion of a part 6 where the nozzle contacts with a slag line 5 on the molten metal surface. The inside 13 where the nozzle does not contact with the slag line 5 is made of the fused silica. The nozzle is further so shaped as to expand upward and is tapered at >=1.5mm/m to prevent a sleeve 11 consisting of the fused silica from falling during casting. The fused silica is formed to 7-30mm thickness at which the cracking thereof is obviated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention can produce ultra-low (C) steel of [C]≦1s ppm, for example, for cold-rolled and surface-treated steel sheets for ultra-deep drawing. This relates to a continuous casting nozzle.

[Conventional technology]

Generally, continuous casting of slag and large-section plumes is performed using a submerged nozzle and powder casting method.

One of the main purposes of this is to prevent molten steel from oxidizing between the tundish and the mold, and another purpose is to float inclusions brought into the mold as much as possible and absorb them into the powder.

Therefore, for the former purpose, when installing the immersion nozzle by the exterior method, it is necessary to maintain a non-oxidized state without drawing air from the joint, and for the latter purpose, it is necessary to maintain the non-oxidized state by not sucking air from the joint. It is important to select a nozzle shape that matches the cross-sectional shape, area, and casting speed of the slab.

The material of the immersion nozzle is related to the operation and quality of continuous casting, such as corrosion damage and nozzle clogging, so it is important to select one that is compatible with the casting steel type and casting conditions. High Mn steel is made of alumina-graphite, which is less susceptible to melting loss due to Mn, while low Mn steel is made of fused silica (frozen silica), which is relatively resistant to thermal shock and is relatively less prone to nozzle clogging.

FIG. 5 is a longitudinal sectional view of a conventional immersion nozzle used in an air seal for continuous casting, and FIG. 6 is a longitudinal sectional view of a conventional tundish immersion nozzle.

In FIGS. 5 and 6, the air seal or stopper one-type immersion nozzle 1 is connected to the mold 2.
It is immersed in the charged molten steel 6 as shown by the arrow.

The material of these air seal or stopper type immersion nozzles 1 is mainly composed of alumina graphite 4, and as shown in FIG. It is being

Note that 8 is a stopper, 9 is a contact surface with the stopper, 10 is an immersion nozzle outlet, and 11 is a sleeve.

Using the immersion nozzle shown in FIGS. 5 and 6, ultra-low [C] steel (for example, [
[C]≦15 ppm), [C] in the alumina graphite 4 is picked up in the molten steel 3. This causes an increase in (C) in the molten steel, so it is common to use phased silica (fused silica) instead of alumina graphite as the material for the immersion nozzle. However, the slag line 5 had poor corrosion resistance and could not be used for a long time.

[Problem that the invention seeks to solve]

The present invention provides an immersion nozzle for use in manufacturing ultra-low (C) steel for ultra-deep drawing cold-rolled or long-face treated steel sheets by continuous casting without reducing erosion resistance against slag and preventing it from melting into molten steel. [C] The purpose is to create a structure that can suppress the pickup to a minimum.

[Means for solving problems]

Regarding the material of the immersion nozzle, phased silica has poor slag erosion resistance and is alumina graphite.In the present invention, the inside of the tundish is made of phased silica ( It consists of two layers: fused silica (fused silica) and alumina graphite on the outside, which is in contact with the slag.

Furthermore, the continuous casting nozzle has a fused silica thickness of 7 to 30 m, and a nozzle shape with a taper of 1.5 m/m or more to prevent the phased silica tube from falling.

As an example of surface-specific aspects, in the case of a one-stop type immersion nozzle,
This continuous casting nozzle also includes a nozzle in which the molten steel stopper contact surface is made of aluminagraphite, while the outer surface that contacts the slag is made of zirconia carbon.

[Effect]

The continuous casting nozzle of the present invention has an inner side (non-slag contact surface).
By having a two-layer structure of phased silica and alumina graphite on the outside (slag contact surface), the drawbacks of phased silica and alumina graphite mentioned above are overcome, suppressing [C] pickup into molten steel and reducing slag. This prevents the erosion resistance from decreasing.

Furthermore, the thickness of the phased silica is 7 to 30 m, preferably 10 to 60 m in the case of a submerged nozzle for an air seal pipe, as a thickness that does not cause breakage.

In addition, in order to prevent the phased silica pipe from falling during casting, the taper of the upper width should be 1.5 ws/m or more, preferably 3 wa for taper 1 in the case of an internal tundish immersion nozzle.
By applying more than s/m, it will not peel off during casting.

In the case of a tundish immersion nozzle of the internal type, the outer portion VC1 that contacts the slag surface may be made of zirconia carbon as in the conventional case, and the other outer portion may be made of alumina graphite.

Next, embodiments of the present invention will be described below.

An example is shown.

〔Example〕

FIG. 1 is a longitudinal cross-sectional view of a submerged nozzle used in the air seal for continuous casting of the present invention, and FIG. 2 is a longitudinal cross-sectional view showing an embodiment of an intercalated tundish submerged nozzle.

In the immersion nozzle 1 shown in FIG. 1, in order to prevent major erosion of the contact portion 6 with the slag line 5 on the molten steel surface, the outer side 12 that contacts the slag is made of alumina graphite, and the inner side 13 that does not make contact is made of alumina graphite. The material is fused silica. Generally speaking, the nozzle shape is made wider, and in order to prevent the fused silica sleeve 11 from falling during casting, a taper of 1.5 vm/m or more is applied, and the thickness is set so that the thickness of the fused silica does not break. 10-30
■It was closed.

In addition, in the one-stopper type immersion nozzle 1 shown in Fig. 2, conventional zirconia carbon is used in order not to change the erosion resistance of the contact portion 6 with the slag line 5 on the molten steel surface.
In order not to change the erosion resistance of the stopper contact surface 9 at the upper part of the nozzle, alumina graphite is used, and the inner part 16 is made of fused silica. Furthermore, the nozzle shape has a wide taper. Taber is attached at least 3m/hL, and the thickness of the fused silica is 7 as long as it does not break.
~30■.

Using the immersion nozzle configured as described above, ultra-low carbon material ([C
]≦15ppm) RH (degassing treatment) to [C] pick-up from the refractory between the slabs (marked with a *)
A comparison between the conventional nozzle (marked O) shown in FIGS. 5 and 6 is shown in FIGS. 6 and 4, respectively. As is clear from Figures 3 and 4, the RH end (C) (pPm) and the CC of the slag.
) According to the relationship graph with ppm, by using the nozzle of the present invention, the [C] pickup was improved by sp ppm, and it became possible to suppress the EC) big amplifier to o ppm.

〔Effect of the invention〕

The continuous casting nozzle of the present invention does not reduce the erosion resistance against slag when producing ultra-low [C] steel for ultra-deep drawing cold-rolled or shishome-treated steel sheets by continuous casting, and does not reduce corrosion resistance to molten steel. C) Big amplifier can be kept to a minimum, which is impossible with conventional nozzles.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a first embodiment of the present invention applied to an immersed nozzle for air sealing, FIG. 2 is a vertical cross-sectional view of a second embodiment of the present invention of an internal tundish immersed nozzle, and FIG. FIG. 4 shows the RH in the first embodiment and the second embodiment, respectively.
The relationship graph between the end [c] and the slab [C], and FIGS. 5 and 6 are longitudinal sectional views of a conventional air seal immersion nozzle and an interpolated tundish immersion nozzle, respectively. In the figure, 1: immersion nozzle, 2: tundish or mold, 6: molten steel, 5: slag line, 6: contact area with slag, 7: zirconia carbon, 9: contact surface with stopper, 11 Ni sleeve, 12 Ni slag outside in contact with, 16: inside. In each figure, the same reference numerals indicate the same or corresponding parts. Agent Patent Attorney Sanro Kimura Figure 3 Figure 4 RHIM Ryo CO (ppm) R
HP-Complete (C) (ppm) No. 5rIl Fig. 6

Claims (4)

[Claims] (1) A continuous casting nozzle characterized in that the inner side, which does not come into contact with the slag in the tundish or mold, is made of fused silica, and the outer side, which comes into contact with the slag, is made of two layers of alumina graphite. (2) The continuous casting nozzle according to claim 1, wherein the thickness of the fused silica is 7 to 30 mm. (3) The continuous casting nozzle according to claim 1, wherein the nozzle shape is wide at the top and tapered by 1.5 mm/m or more. (4) The continuous casting nozzle according to claim 1, wherein the surface of the nozzle that contacts the molten steel stopper is made of alumina graphite, while the outer surface that contacts the slag is made of zirconia carbon.