JPH09192797A - Detector of molten metal surface height of molten steel in tundish - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the height of molten metal surface in a tundish in a high precision. SOLUTION: A float 4 is floated on the molten steel surface 3 in the tundish 1, and a detecting rod 5 is arranged at the upper part of this float 4, and a positional detector 7 for measuring the position of this detecting rod 5 is arranged. By this constitution, in the case of using an induction heating device, the heating in the limited output avoiding a pinch phenomenon can be executed. Further, in the case of using a plasma heating device, the accurate output adjustment can be executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a level detector for molten steel in a tundish.

[0002]

2. Description of the Related Art The temperature of molten steel in a tundish in a continuous casting facility is inevitably lowered at the beginning of casting, at the end of casting, and when ladle is replaced. Such a temperature drop adversely affects the quality of the slab such as non-metallic inclusions and segregation.

In recent years, there has been a technique for heating molten steel in a tundish for the purpose of improving slab quality and yield in order to solve this problem, and two methods, induction heating and plasma heating, have been adopted. In these heating methods, it is necessary to accurately detect the molten metal surface height of the molten steel in the tundish during operation and control the heating device.

For this reason, conventionally, the weight of the entire tundish containing molten steel is measured by a load cell, and the level of molten steel is estimated from the weight and used for controlling the heating device. However, this method is a method of obtaining the molten metal surface height by considering the shape of the tundish inner wall from the total weight of the tundish, and a refractory material is applied to the reference tundish inner wall. The inner wall shape of the tundish will change with use due to the accuracy of construction, wear and tear due to usage conditions, and adhesion of metal. for that reason,
This method cannot accurately detect the level of the molten steel in the tundish and cannot control the induction heating and the plasma heating device with sufficient accuracy.

When the height is detected by the conventional method,
The heating device for molten steel in the tundish will be described below. In an induction heating device, a large amount of induced current is generated in the molten steel circuit of the tundish and the molten steel of the molten metal of the gutter, so that the current and the current attract each other in the gutter. A force is exerted on the molten steel in the groove to shrink the cross section. This action is generally referred to as the pinch effect, which does not become apparent when the level of the molten metal in the tundish is above a certain amount,
When the height of the molten metal decreases, the static pressure of the molten steel decreases, so that the molten steel in the groove begins to contract, and finally the molten steel in the groove becomes cut. The phenomenon in which the molten steel in the ditch is cut is called the pinch phenomenon. Conventionally, as a method of preventing troubles due to the pinch phenomenon, it is general to perform advance prediction based on the molten metal height and limit the power output before the pinch phenomenon occurs.

Therefore, the above method of estimating the molten metal surface height from the molten steel weight is inaccurate, and in order to avoid the pinch phenomenon, there is a margin in the molten metal surface height at which the pinch phenomenon actually occurs. It was necessary to reduce the output from.

In the plasma heating device, a plasma torch and its moving device are installed on the upper part of the tundish, and the output of this plasma arc is represented by the product of the arc current and the arc voltage. Generally, the stability of the plasma is ensured. Therefore, the power supply controls the current, and the current becomes a set value given from the outside. Therefore, it is necessary to increase the arc current in order to increase the output under the condition that the arc current is constant, and the arc current used for heating molten steel is the arc length, if the atmospheric conditions are constant.
That is, it increases in proportion to the distance between the plasma torch and the molten steel surface. When heating the molten steel, insert the plasma torch positioned by the moving device into the tundish, and move the plasma torch linearly in the vertical direction by the moving device according to the height of the molten steel surface to move the position of the cathode electrode at the tip of the plasma torch. Instead, the arc length is adjusted to adjust the output. Therefore, the method of estimating the molten metal surface height from the molten steel weight described above has poor accuracy and causes fluctuation of the arc length, that is, the arc voltage, which is the most important for stable output control of the plasma arc.

[0008]

In order to effectively perform induction heating or plasma heating of the molten steel in the tundish, it is important to detect the molten metal height of the molten steel in the tundish with high accuracy. In the case of an induction heating device, when heating at the end of the casting when the molten metal surface height is low, which originally requires the input of high output power, the molten metal surface height detection error is taken into consideration, and a margin for the error is provided to output from an early stage. There is a problem that you have to control. Further, in the case of the plasma heating device, the error in detecting the height of the molten metal becomes an error in the arc length, that is, an error in the arc voltage, which makes it difficult to adjust the output.

[0009]

The molten steel level detector for molten steel in a tundish according to the present invention provides a molten steel level detector for molten steel in a tundish of a continuous casting facility, which is It is characterized in that it is provided with a float that floats, a detection rod hung vertically on the float, a support guide that vertically supports the detection rod, and a position detector that detects the position of the detection rod.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The structure and operation of a molten steel level detector for molten steel in a tundish according to the present invention will be described with reference to FIG. FIG. 1 is a schematic side view of a molten steel level detector for molten steel in a tundish according to the present invention. In FIG. 1, the molten steel 2 is contained in the tundish 1, and the molten metal surface height L changes during the operation. The float 4 is made of heat-resistant material such as refractory brick having a smaller specific gravity than the molten steel 2 on the molten steel surface 3.
The float 4 is attached with a detection rod 5 made of, for example, stainless steel for pulling out above the tundish. The detection rod is supported by a support guide 6 attached to a bracket installed on the iron skin of the tundish so that it can be raised and lowered. The position of the detection rod 5 is detected by the position detector 7.

The float 4 follows the fluctuations in the height L of the molten metal during operation, so that the detection rod 5 moves up and down. It is possible to measure L.

[0012]

When the molten steel level detector for molten steel in the tundish of the present invention is applied to induction heating or plasma heating of molten steel in the tundish, the following effects can be expected. (1) When applied to an induction heating device, it is possible to perform heating at a limit output that avoids the pinch phenomenon. (2) When applied to a plasma heating device, accurate output adjustment becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a molten steel level detector for molten steel in a tundish according to the present invention.

[Explanation of symbols]

 1 Tundish 2 Molten steel 3 Molten steel surface 4 Float 5 Detection rod 6 Guide 7 Position detector 8 Breckett L Level of molten metal

Claims (1)

[Claims] 1. In a molten steel level detector for molten steel in a tundish in a continuous casting facility, a float floating on the molten metal surface of the molten steel in a tundish, a detection rod hung vertically on the float, and a detection rod supported so as to be vertically movable. And a position detector for detecting the position of the detection rod. A molten steel height detector for molten steel in a tundish.