JPS59107755A - Heating method of molten steel in tundish - Google Patents

Abstract

PURPOSE:To minimize evaporation of a molten steel while maintaining the uniform temp. of the molten steel and preventing local overheating to an ultra-high temp. by subjecting the molten steel in a heating chamber under heating by plasma arc heating to gas stirring. CONSTITUTION:A bottom gas blowing device 17 is so arranged that it can blow inert gas into a heating chamber 12. While the molten steel existing in the chamber 12 is heated by a plasma torch 15, the inert gas is blown from the device 17 toward the inside of the chamber 12. The effect of maintaining the uniform temp. of the molten steel, eliminating the local overheating to an ultra- high temp., and improving the efficiency of heating is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to heating molten steel in a tundish by plasma arc.

Attempts have been made in the past to heat molten steel in a tundish of continuous casting equipment for purposes such as secondary refining, promotion of levitation of inclusions, and prevention of nozzle clogging. In this case, it is preferable to use a plasma arc as the heating source from the viewpoint of molten steel contamination, heating efficiency, etc. Plasma arc heating is a method of locally heating the molten steel present in the heating chamber, in which an arc is generated by equipping the top of the heating chamber, whose lower end is immersed in the molten steel, with a plasma torch as an electrode for generating an arc. It is.

However, the heating method described above has the following five problems that need to be solved. In other words, as is well known, in plasma arc heating, molten steel is locally heated to extremely high temperatures, which causes evaporation of the molten steel, which adheres to the plasma torch etc. and generates an arc. Since the molten steel flows from the inflow side from the ladle to the injection side to the continuous casting, the locally heated molten steel is mixed uniformly, making it difficult to maintain the overall temperature uniformly.As a result, the refractory This may cause local melting of objects, nozzle clogging, breakouts, etc.
This will cause a great deal of trouble to the operation of the plant.

The purpose of this invention is to solve the above problems all at once. The purpose of this invention is to bottom-bubble the molten steel in the heating chamber with a harmless gas while it is being heated by plasma arc heating. By trying to equalize the temperature of the molten steel in the tundish, it is easy to equalize the temperature of the molten steel in the tundish, and by constantly supplying new molten steel to the heat receiving surface from the plasma torch, it is possible to prevent local extremely high temperatures. In this way, evaporation of molten steel is minimized and plasma arc heating is performed efficiently and stably.

FIG. 1 is a general view showing an example of an apparatus for carrying out the method of the invention.

A shows a ladle, B shows a rolled tundish having a lid 4 on a container 3, and C shows a plasma arc heating device. The mechanism is a sliding nozzle device installed at the bottom of the rattle, and 2 is a long nozzle installed at the bottom, which is inserted into the shield tundish B through a hole 5, and this hole 5 is sealed with bellows lO or the like. Reference numeral 9 is a stopper for a immersion nozzle (not shown) into the mold, and hole 8 is a hole.

Similarly, it is sealed with a bellows lO or the like.

Additionally, the lid 4 is provided with a viewing window 6, a preheating lower, and the like.

The main components of the plasma arc heating device C are a front wall 13 and a rear wall 1, which are provided on the lid 4 and whose lower ends are immersed in the molten steel.
It consists of a heating chamber 12 having a heating chamber 4 and a plasma torch 15 installed at the top of the heating chamber 12.゛) indicates the power supply electrode (anode).

Although this example shows a dipping type from above, other types may be used. A plasma gas such as M gas is blown into the plasma torch 15, and the torch 15 is cooled by suitable means.

17 is a bottom gas blowing device provided according to the present invention;
Inert gas can be blown into the heating chamber 12.

Note that 18 and 19 indicate the upper weir for solo cutting.

While the molten steel existing in the heating chamber 12 is being heated by the plasma torch 15, inert gas is blown into the heating chamber 12 from the gas blowing device 17, thereby making the temperature of the molten steel uniform. 1. Eliminate local ultra-high temperature heating, improve heating efficiency, and obtain the above-mentioned effects.

Examples will be described in detail below.

Example tandish; Rudol 1 strand 14.4
Injection temperature: 1560℃ Saw J type: Cold-rolled material, low carbon A-killed steel heating device; LOOKW DC, arc plasma heating chamber gas blowing device; Porous nozzle installed under heating chamber 1, Ar flow rate 1004/ mln and toshida.

The results obtained using the above specifications were as follows.

(1) Temperature of molten steel (The temperature of molten steel at the exit side of the heating chamber is shown in Figure 2.) In the case of inlaying without using the device of the present invention, the temperature in the vicinity of the molten metal surface for several tens of minutes was extremely high, and the uniformity of sieving of the molten steel was poor. By using one device that could not be secured, we were able to maintain a nearly constant temperature from the surface to the depth of about 400 ms.

Furthermore, the temperature can be increased by approximately 15°C compared to conventional methods, making it possible to lower the tapping temperature and perform low-temperature casting.

(2) Amount of Torch Metal Adhesion When using the device of the present invention, operational problems caused by metal adhesion to the torch can be improved.2 By using the present device, stable operation can be achieved.

(3) Effects on refractories If the device of the present invention is not used, localized high temperature areas will be generated, resulting in significant damage to refractories.

Although stable operation was not possible, these problems were resolved by using this equipment.

[Brief explanation of drawings]

FIG. 1 is an overall sectional view showing an example of an apparatus used for carrying out the method of the present invention, and FIG. 2 is a chart of molten steel temperature in the example. C Plasma arc heating device 12... Heating chamber 15... Plasma torch 6... Anode 17... Inert gas blowing device tie? ] Figure 2 θ /θ02θθ 3θθ 4θ
θID Yumen Riki and others! g commercial square (m side)

Claims (1)

[Claims] A method for heating molten steel in a tundish, which performs plasma arc heating on molten steel existing in a heating chamber immersed in molten steel in a tundish, and further includes stirring the molten steel in the heating chamber with gas during heating.