JPH0526868A - Method for measuring temperature and sampling of melted steel in electric furnace - Google Patents

Abstract

PURPOSE:To prevent a probe from hitting against a non-dissolved scrap when dissolving a scrap at an electric furnace with a bottom-blowing gas nozzle and then measuring temperature and performing sampling of a molten steel within the furnace. CONSTITUTION:When a diameter of a bottom-blowing gas nozzle 6 is set to d and a depth of a molten steel 8 is set to h, temperature-measurement and sampling are performed with a cylindrical range with a diameter of D=0.4 h+d which is concentric to the bottom-blowing gas nozzle. Since a flow rate of the molten steel within this range becomes fast, heat transfer coefficient of a surface of a scrap becomes large and dissolution of scrap advances preferentially, thus preventing the probe 4 from hitting against a non-dissolved scrap 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature measuring / sampling method for adjusting a molten steel temperature and a molten steel composition in an electric furnace having a bottom blowing gas nozzle.

[0002]

2. Description of the Related Art Conventionally, temperature measurement and sampling of molten steel in an electric furnace are mainly performed manually in front of the furnace.
These are not only heavy labor work under high temperature, but also very dangerous because they handle molten steel. recent years,
To improve these operations, for example, as described in Japanese Patent Publication No. 54-3398, a sampler holding rod is provided so as to reciprocate in the axial direction, and a device for remote temperature measurement / sampling is developed and introduced. This is being done, and great effects are expected in the improvement of work environment and labor saving.

[0003]

In the operation of an electric furnace, in order to adjust the molten steel composition in the refining period after scrap melting, it is desirable to sample as early as possible and to know the analysis result. Therefore, sampling is performed immediately after the scrap has burned out. However, unmelted scrap generally remains in the temperature measurement / sampling that is performed when the scrap melts down.Therefore, in remote temperature measurement / sampling devices where undissolved scrap remains cannot be confirmed. In many cases, a temperature / sampling probe hits the unmelted scrap and breaks the probe, and the actual situation is that the probe is manually broken to prevent it from breaking.

In view of the above situation, the present invention is capable of smoothly performing temperature measurement / sampling work of molten steel when melted, without the temperature measurement / sampling probe hitting unmelted scrap. The purpose is to provide a temperature / sampling method.

[0005]

According to the present invention, scrap is melted in an electric furnace having a bottom-blown gas nozzle, and in the method for measuring and sampling molten steel in the furnace, the diameter of the bottom-blown gas nozzle is d and the depth of molten steel is h. In this case, the temperature measurement / sampling method for molten steel in an electric furnace is characterized in that the temperature measurement / sampling is performed in a cylindrical range having a diameter D = 0.4h + d concentric with the bottom blowing gas nozzle. In the present invention, when the bottom-blown gas nozzle is composed of a group of thin tubes, the temperature measurement is performed with the diameter of a circle connecting the centers of the outermost thin tubes as d.
Determine the sampling range.

[0006]

It has been confirmed in the study by the present inventors that the bottom-blown gas stirring technology is very effective for improving the molten steel speed of the electric furnace. It turns out that it dissolves earlier. This is because the gas blown from the bottom-blown gas nozzle rises and diffuses while giving energy to the molten steel, and the molten steel flow velocity in this part becomes faster than other parts.As a result, the heat transfer coefficient on the scrap surface increases and scrap melting does not occur. This is because it proceeds preferentially. An investigation of the situation of unmelted scrap at the time of meltdown in an actual furnace revealed that there was almost no unmelted scrap remaining in the range where the upper surface of the molten steel rises due to the bottom-blown gas.

On the other hand, according to the study by the present inventors, the relationship between the molten steel depth and the molten steel swelling area on the upper surface of the molten steel in the case of gas bottom blowing can be expressed as shown in FIG. It was confirmed in the observation results that these agreed well.

According to the present invention, the temperature measurement / sampling probe does not hit the scrap because the temperature measurement / sampling at the time of the scrap remaining burned out is generally performed within the range where there is no unmelted scrap around the bottom blowing gas nozzle. , It becomes possible to smoothly perform temperature measurement and sampling work by remote control.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiment. FIG. 1 is a vertical sectional view of an electric furnace for explaining an embodiment of the present invention. 1 is an electric furnace, 2 is an electrode, 3 is a furnace lid, and 4 is a temperature measuring / sampling probe. This probe is inserted through a through hole provided in the furnace lid 3 and is lifted and lowered by a lifting device (not shown) by remote control. Reference numeral 5 is a holding rod for the probe. Reference numeral 6 denotes a bottom-blown gas nozzle, which blows gas into the molten steel from one or a plurality of locations. The nozzle may also be composed of a group of thin tubes. 7
Shows an image of unmelted scrap immediately after the meltdown. When the temperature measuring / sampling probe 4 is lowered by the elevating device, if it hits the unmelted scrap 7, the probe will break. 8 shows molten steel.

FIG. 2 is a cross-sectional view of the electric furnace for explaining the embodiment of the present invention (a view taken along the line AA of FIG. 1). The shaded area 9 indicates the temperature measuring / sampling range according to the present invention, and the temperature measuring / sampling is performed in a cylindrical area having the shaded area as the upper surface. The diameter D of this hatched portion is the depth of molten steel, and the diameter of the bottom blowing gas nozzle (when the nozzle is composed of a group of thin tubes, the diameter of the circle connecting the centers of the outermost thin tubes).
Is represented by d, D = 0.4h + d.

In order to adjust the composition of molten steel, it is necessary to sample as soon as possible. Therefore, immediately after confirming the burn-through, insert the probe in the shaded area and measure the temperature.
Sampling should be performed. As a result, the probe never hit the scrap.

Therefore, even in the case of a temperature measuring / sampling device of a type in which reciprocating movement is carried out by an elevating device, if the probe is installed so as to be inserted in the range of the shaded portion, remote operation becomes possible. It should be noted that if the probe deviates from the shaded area 9, the probe hits the scrap, and it can be seen that unmelted scrap remains, as shown in FIG.

[0013]

As described above, in the temperature measuring / sampling method for molten steel in the furnace according to the present invention, since the temperature measuring / sampling probe does not hit unmelted scrap, the temperature measuring / sampling device operated remotely can be used. Can work smoothly, which greatly contributes to improving the working environment, saving labor, and improving equipment reliability.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an electric furnace according to an embodiment of the present invention.

2 is a cross-sectional view of an electric furnace of an embodiment according to the present invention (FIG.
(A-A arrow view).

FIG. 3 is a graph showing the relationship between the depth of molten steel and the rising range of molten steel due to bottom-blown gas.

[Explanation of symbols]

 1 Electric Furnace 2 Electrode 3 Furnace Cover 4 Temperature Measuring / Sampling Probe 5 Holding Rod 6 Bottom Blowing Gas Nozzle 7 Unmelted Scrap 8 Molten Steel 9 Temperature Measuring / Sampling Range

Claims (1)

Claim: What is claimed is: 1. A method of melting scrap in an electric furnace having a bottom-blown gas nozzle, measuring and sampling the temperature of molten steel in the furnace, wherein the diameter of the bottom-blown gas nozzle is d, and the depth of molten steel is h. , The diameter concentric with the bottom blowing gas nozzle D = 0.
A method for measuring and sampling molten steel in an electric furnace, characterized by measuring and sampling temperature in a cylindrical area of 4h + d.