CS250000B1 - Dip pipe for continuous casting - Google Patents

Abstract

Submersible tube for continuous casting it consists of a cylindrical part (1) on which it is connected over the rounded transition / 2 / diffuser / 3 /, whose angle / 4 / extension is in the range from 8 ° to 20 °. Diffuser diameter ratio (3) to the diameter of the cylindrical portion (1) is in the range from 1.2 to 2.8.

Description

(54) Submersible tube for continuous casting

Submersible tube for continuous casting consists of a cylindrical part (1), which is connected through a rounded transition (2) diffuser (3), whose angle (4) is in the range of 8 ° to 20 °. The ratio of the diffuser diameter (3) to the diameter of the cylindrical portion (1) is in the range of 1.2 to 2.8.

The present invention relates to an immersion tube for continuous casting.

In a continuous casting, for example steel, molten metal flows from the tundish into the crystallizer, which is essentially a water-cooled bottom without a glass. At the walls of the crystallizer, the metal solidifies and at the bottom of the crystallizer, the solidified crust must be so strong that it can withstand the effect of the ferostatic pressure of the still liquid core. After further cooling the continuous casting is divided into the required lengths.

In order to improve the quality of the cast metal, in particular of stainless steels, the sinks commonly used in ladles for pouring into chill molds are not used for filling the crystallizer, but rather dip tubes.

There are different requirements on immersion tubes than for sinks. In addition to its main function, the same as that of the sink, that is, the inlet of the metal to the mold, the immersion tube protects the molten metal from contact with air and is therefore submerged below the liquid metal level in the crystallizer. protects metal from contact with air. However, appropriate geometric shaping can influence the quality of the continuous casting even more.

In crystallizers of roughly square cross section, a cylindrical tube of constant diameter is most often used. The metal flows vertically into the crystallizer, and the availability of the current below the surface is large, so that the non-metallic inclusions are clogged so deeply that they cannot float to the surface, they are retained inside the bar, thus impairing its quality.

Also, the temperature field is considerably uneven, which affects the formation of cracks. Therefore, tubes with two or more side openings, with radial outflow, have been designed which are closed at the bottom by the bottom.

While the availability of the current is reduced, the holes weaken the tube walls and the bottom is torn off at the beginning of the casting when the tube is subjected to mechanical and thermal shock. A large change in the direction of the metal flow inside the tube causes tube erosion and these ceramic particles also worsen the purity of the bar.

With an approximately square cross-section of the bar, the metal stream strikes at a relatively high velocity against the bar being formed and is locally milled, which increases the risk of rupture.

If the hole axes are horizontal or inclined downwards, the bulk of the metal flows down the wall and carries the inclusions into the bar.

These drawbacks are eliminated by a continuous casting dip tube consisting of a cylindrical portion followed by a diffuser according to the invention having a diffuser extension angle of between 8 ° and 20 ° and a ratio of the diffuser outlet diameter to the diameter of the cylindrical part within from 1.2 to 2.8.

The advantage of the immersion tube according to the invention is to reduce the flow rate of the jet and thus the momentum of the jet and the kinetic energy of the flow of metal flowing into the crystallizer. This substantially reduces the current availability and facilitates the non-metallic inclusions to float to the surface, both because they are introduced to a shallower depth and because the velocity of the current carrying the inclusions down is slower.

Since the metal stream is parallel to the tube wall, there is minimal erosion of the tube, which again reduces the number of non-metallic inclusions in the bar, increasing the purity and hence the quality of the bar. The tube does not bark and therefore the risk of rupture is much less than that of tubes with side openings. The tube is also more uniform than the cylindrical tube, which again increases the quality of the bar.

The invention and its effects are explained in more detail in the description of an embodiment thereof according to the accompanying drawing which shows a cross-sectional elevational view of a continuous casting immersion tube according to the invention, including its placement between a pan and a crystallizer.

In the dip tube according to the invention, the cylindrical portion 1 is followed by a rounded transition 2 and then a diffuser 6. Depending on the operating conditions, the diffusion angle θ is between 8 ° and 20 °. The ratio of the diameter of the diffuser 2 to the diameter of the cylindrical portion 1 is ϊ from 1.2 to 2.8.

For practical purposes, for example, an optimum angle of 15 [deg.] Has been used for a crystallizer having a cross-section of 0.32 * 0.28 m at an angle of 4 [deg.] With a diameter ratio of diffuser 2 to cylindrical portion of two.

At a small angle of expansion 4, the current penetrates well below the surface as in the cylindrical tube. At a wide spread angle θ, the current does not follow the walls of the diffuser 3, the output velocity, momentum and kinetic energy of the current are large, and therefore the current availability is large. With the optimum shape of the submerged tube, the current follows the walls of the tube over most of the tube, but the diffuser 3 can operate with a slight current cut-off, but increased kinetic energy dissipation over the shortest possible path is desirable here.

In certain cases, the diffuser 2 can be provided with ribs. The longitudinal ribs, however, are not intended to create a smooth flow, as in the case of pouring into the ingot molds by the top, but to prevent a possible widening of the flow separation from the diffuser wall 3 around the circumference of the tube.

With the dip tube, when the angle of extension and cross-section ratio are correctly selected, the current availability is substantially reduced by half or more compared to the cylindrical tube, and the flow in the crystallizer is organized more conveniently with respect to inclusions separation and temperature uniformity.

The continuous casting immersion tube according to the invention is particularly useful in metallurgy and heavy engineering.

Claims (1)

SUBJECT OF THE INVENTION Submersible tube for continuous casting, consisting of a cylindrical part, followed by a diffuser through a rounded transition, characterized in that the angle (4) of diffuser extension (3) is in the range of 8 ° to 20 ° and diffuser diameter ratio (3) to the diameter of the cylindrical portion (1) ranges from 1.2 to 2.8.