JPH03174958A - Submerged nozzle for continuous casting - Google Patents

Abstract

PURPOSE:To produce a sound slab without involving mold flux by regulating ratio of the total area of two molten metal spouting holes and the area of vertical inner hole in a nozzle to the specific value at the time of continuously casting the molten metal into the slab with the vertical type nozzle having two molten metal spouting holes in the longitudinal direction in a mold. CONSTITUTION:The molten metal of Cu base alloy, etc., is poured through the inner hole 3 while directing the spouting holes 2 in the nozzle 1 having the vertical inner hole 3 of diameter d2 and two horizontal direction spouting holes 2 of diameter d1 to long wall side direction of the longitudinal mold 4, to continuously cast the slab of Cu base alloy. In this case, the ratio of the value A1 total area of the nozzle spouting holes 2, 2 to the A2 area of nozzle inner hole 3 is made to (A1/A2)<=1.1. The sound Cu base alloy slab can be continuously cast without involving the mold flux into the mold 4.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a continuous casting immersion method for supplying molten metal to a mold with an open top that is used when continuously casting slab slabs of copper-based alloys. Regarding nozzles.

[Conventional technology]

The continuous casting method is a method in which the molten metal from the tundish or the molten metal discharged from the melting furnace into the gutter is fed into a water-cooled copper mold, the molten metal is cooled in the mold and solidified one by one, and the slabs are continuously pulled out from the mold. It is widely used as a casting method for steel and non-ferrous metals.

Generally, when casting slab slabs of copper-based alloys by the continuous casting method, a rectangular through-hole mold is used, which consists of a pair of opposing short mold pieces and a pair of long mold pieces, and To supply the molten metal from the gutter into the mold, an inverted T-shaped nozzle is used that spouts the molten metal perpendicular to the casting direction, taking into consideration the surface of the slab and the occurrence of pinholes inside the slab. is used.

As shown in FIG. 1, this nozzle generally has a cylindrical ejection port 2 along the center line of a cross section perpendicular to the casting direction of the nozzle 1. The mold 4 is attached to a tundish or trough so that the molten metal is ejected parallel to the long pieces of the mold 4.

In order to stably cast slabs with few casting defects using the continuous casting method, heat must be removed uniformly within the mold, and a sufficient amount of mold flux must be supplied to coat the surface of the molten metal within the mold. It is important to maintain the lubricity of the slab and to prevent mold flux from getting caught inside the slab.

[Problem that the invention attempts to solve]

However, in the above conventional technology, depending on the amount of molten metal supplied into the mold, the jet flow of molten metal from the nozzle may engulf the mold flux covering the surface of the molten metal into the mold, and the engulfed mold flux may solidify into a shell. There is a problem that it is trapped inside the slab and remains inside the slab.

The mold flux remaining inside the slab appears as a surface defect in the subsequent manufacturing process of the copper-based alloy strip, and is a major constraint on surface quality, contributing to a decrease in yield.

The present invention has been made in view of the above circumstances, and it is possible to stably produce a sound slab slab of a copper-based alloy without causing mold flux to be drawn into the mold during continuous casting of a copper-based alloy. The object of the present invention is to provide a continuous casting method for copper-based alloys.

[Means to solve the problem]

In order to solve the above object, the present inventor has investigated the occurrence of surface defects due to the shape of the immersion nozzle and the entrainment of mold flux into the slab slab when casting slab slabs of copper-based alloy by continuous casting method. We have conducted extensive research into the relationship between

As a result, by selecting the ratio between the sum of the cross-sectional areas of the two nozzle nozzles and the cross-sectional area of the inner hole, surface defects caused by the entrainment of mold flux into the slab slab that appears in the subsequent manufacturing process can be reduced. to reduce, i.e.
It was discovered that it is possible to suppress mold flux from getting caught up in the slab slab.

That is, the immersion nozzle for continuous casting according to the present invention is a two-hole immersion nozzle for continuous casting in which molten metal is ejected perpendicularly to the casting direction. It is characterized in that the ratio to the internal hole cross-sectional area A2 is in the range of A1/A, ≦1.1.

The present invention prevents mold flux from being drawn into the mold by setting the ratio of the cross-sectional area of the two ejection holes of the immersed nozzle to the cross-sectional area of the inner hole A2 of the immersed nozzle to 1.1 or less. It is something to do.

The reason for this is that in the continuous casting using a two-hole immersion nozzle in which the ratio of the cross-sectional areas is greater than 1.1.

The jet flow of molten metal spouted from the immersion nozzle becomes a biased flow,
The molten metal does not constantly eject perpendicularly to the mold strip, but irregular flow occurs just below the mold flux coating surface, and at this time, the mold flux gets caught up in the slab slab, and as mentioned above, it interferes with subsequent production. This is because they appear as surface defects during the process.

Note that the submerged nozzle ejection port cross-sectional area and submerged nozzle inner hole cross-sectional area herein refer to the submerged nozzle ejection port 2 shown in FIG.
This is the area of the circular cross section of the inner hole 3.

〔Example〕

The present invention and its effects will be specifically explained below using experimental examples.

This experiment was conducted using two types of brass using a two-hole immersion nozzle in which the ratio of the sum of the cross-sectional areas of the two nozzle holes shown in Table 1 and the cross-sectional area of the inner hole of the immersion nozzle was changed using the continuous casting method. A slab was cast, and then the number of surface defects appearing on the surface of the strip manufactured by rolling was counted.

These results are shown in Table 1 along with comparative examples.

As can be seen from Table 1, the ratio of the sum of the cross-sectional areas of the two nozzle orifices of the submerged nozzle calculated from the diameter d of the nozzle ejection port and the diameter d2 of the nozzle inner diameter to the cross-sectional area of the inner hole of the submerged nozzle is 1.1 or less. All of the examples of the present invention exhibited no defects on their surfaces.

Furthermore, in comparative examples where the cross-sectional area ratio between the sum of the cross-sectional areas of the two ejection holes of the immersed nozzle and the cross-sectional area of the inner hole of the immersed nozzle was 1.1 or more, defects occurred on the surface of the strip.

Table 1 (Note 1) (Note 2) The cross-sectional area ratio is the nozzle jet hole diameter d1 and the nozzle inner hole diameter d.
2 represents the ratio of the sum of the cross-sectional areas of two nozzle ejection holes and the cross-sectional area of the nozzle inner hole, respectively calculated from 2.

The number of surface defects indicates the average number of surface defects present on 1 square meter of the strip surface.

Therefore, when a slab slab of a copper-based alloy is cast using the immersion nozzle for continuous casting according to the present invention, a slab slab of a copper-based alloy that is sound and free from casting defects due to entrainment of mold flux can be obtained.

〔Effect of the invention〕

According to the present invention described above, it is possible to stably cast a sound slab slab of a copper-based alloy free of casting defects due to entrainment of mold flux.

[Brief explanation of drawings]

FIG. 1 shows a two-hole immersion nozzle according to an embodiment of the present invention, (a) is a longitudinal sectional view, (b) is a side view, (c) is a cross-sectional view, and FIG. 2 is a two-hole immersion nozzle. This is an explanatory diagram showing the position of the nozzle attached to the mold, and the arrows in the diagram indicate the flow of molten metal ejected from the nozzle. Engineering: Nozzle, 2: Nozzle outlet, 3:
... Nozzle inner hole, 4... Mold.

Claims (1)

[Claims] (1) In a two-hole immersion nozzle for continuous casting in which molten metal is ejected perpendicularly to the casting direction, the ratio of the sum A_1 of the cross-sectional area of the two ejection holes of the immersion nozzle to the cross-sectional area A_2 of the inner hole of the immersion nozzle is A_1/ A immersion nozzle for continuous casting, characterized in that A_2≦1.1.