JPS58144701A - Method and measuring tool for measuring thickness of covering layer of bathed surface of melted metal bath - Google Patents

Abstract

PURPOSE:To measure the thickness of the coating layer, by vertically piercing and moving a highly corrosion resisting probe into the coating layer of the bathed surface of the melted metal bath, and detecting the change in an electric signal at a high temperature. CONSTITUTION:In the probe 7 for measuring electric conductivity, an electrode 7' is constituted by embedding a pair of metal wires (W, Mo, Pt, and the like) in a rod made of e.g. BN. The electric conductivity of the rod is extremely small at the high temperature. The rod has high corrosion resistance against both slag and melted steel. The metal wires are slightly protruded from the tip of the rod. Wiring is performed so that a pair of the metal wires constitute an impednace measuring circuit. The probe 7 is moved up and down on a mold powder deposited layer 16 on the melted steel in a continuous casting mold at a high speed by using a guide 15 wherein an automatic lifting mechanism is built in. Thus the electric conductivity is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and a measuring tool for measuring the bath ai coating layer thickness of a molten metal bath.

During the metal melting stage, smelting or agglomeration process, especially in the recently developed continuous casting process, slag, which controls the surface coating of the molten metal bath, plays an important role, sometimes actively and sometimes passively. Regarding the former, in particular, research is being actively carried out to develop metal products of better quality in terms of properties, quality, and usage. The properties of the bath FIiJ coating layer itself on the surface of the gold acupuncture bath were conventionally determined by visual inspection. The refinery slag that flows out and finally exists on the surface of the steel bath in the ladle is caused by changes in the components of the bath in the ladle over time, that is, P in the slag, 0. K causes adverse effects such as oxidation of molten steel due to Fe0K in the slag, and the degree of fluctuation in the steel bath composition increases as the fluidity of the slag increases.

Therefore, in addition to investigating ways to reduce the amount of slag mixed in, attempts have been made to solidify the slag by adding MfO and other substances to suppress its fluidity. However, since there is no method to easily and accurately measure the thickness of the fluid molten slag layer, it introduces instability in operational management and is difficult to put into practical use.

On the other hand, in the continuous casting process, which has recently become popular from the perspective of solidifying steel and energy saving, synthetic slag is mixed with aggregate mainly composed of C powder to adjust the melting rate. Regardless of whether the powder is used in the form of powder or granules, as shown in Figure 1, the molten steel surface 2 in the continuous casting mold 1 is exposed to the atmosphere 111 from the molten steel surface IK liquid in contact with the molten steel surface 2. Therefore, the bath molten slag layer 8, the molten layer 8, the sintered layer and the solid powder layer have a stratified structure such as the granular layer 6, and perform the following functions. 〇That is, the first is insulation and heat retention of the molten steel surface, and the eighth is,
The non-metallic inclusions floating from the molten steel are removed from the molten slag layer δ.
8th, between the mold and the solidified shell!
When molten slag flows in as slag fill, it prevents the mold and solidified shell from seizing, and stabilizes the heat transfer from the molten steel to the mold, thereby preventing cracking defects in the slab.・In order to fully demonstrate the above three functions, K is the mold powder on the mold-like molten steel surface, and the thickness of the entire deposited layer of flux composition is determined. control. It is necessary. Regardless of this, the lack of a detection means often causes troubles such as unstable continuous casting operations (breakouts, vertical cracks, etc.).

The present invention has been made in view of the above-mentioned circumstances, and it is possible to accurately, simply and quickly determine the thickness of the bath surface coating layer on the molten metal bath surface, especially when it is deposited in multiple layers. A method that can individually measure the total thickness and the structure of layered sections, that is, the trends of the molten slag layer, semi-molten layer, sintered layer, and solid powder layer, and can be advantageously used in the implementation of the method. This is an attempt to propose a measuring tool.

In this invention, a pair of electrodes made of a material with high corrosion resistance under high temperature are exposed at the tip of the bath surface coating layer of a molten metal bath in a plane parallel to the surface of the bath. The probe is moved in a direction that vertically penetrates the bath surface coating layer, and changes in the electrical signal generated between the electrodes when penetrating the bath surface coating layer are detected due to the electrical properties specific to the bath surface coating layer. , a bath surface coating layer thickness measurement method of a molten metal bath that is detected along with the moving displacement of a probe. This invention is a method for measuring the bath surface coating layer thickness of a molten metal bath along the molten metal bath surface, on a slag-formed molten layer. A deposited layer of a flux composition containing overlapping powder or granular layers through an intermediate layer such as sinter], resulting from the thermal influence of the electrical properties in each layer of the above stratified divisions during the moving displacement of the globe. It is possible to detect the trend of the stratification as a change in the electrical signal, to detect the intralayer electrical conductor or capacitance of the bath surface coating layer as a change in the electrical signal, and to detect the electrical signal. Let the logarithm of the signal be] and its reciprocal be 10
In addition, this invention consists of a bifurcated molded body made of an insulating material highly resistant to corrosion at high temperatures, each of which has an electrode made of a material highly resistant to corrosion at high temperatures sprayed at its tip. This measuring tool is composed of a glove and a guide for ensuring a vertical posture of the probe with respect to the bath surface coating layer, and is used to carry out the method for measuring the bath surface coating thickness of a molten metal bath.

In the following, the present invention will be explained in detail with regard to the detection of the deposited layer structure of a Franks composition on an example of mold powder on the surface of molten steel in a continuous casting mold.

Now, the inventors have confirmed that in the mold powder deposited layer, each of the layer structures of the above-mentioned layered divisions has unique properties regarding electrical conductivity.

That is, as shown in FIG. 1, the atmosphere side of the mold powder deposited layer is a solid powder layer 6, and the porosity is extremely large, and the effective electrical conductivity is practically zero. In the sintered layer 5, solid particles come into contact with each other, and together with the relatively high temperature inside the layer, the sintered layer 5 has electrical conductivity, although it is small.

Furthermore, the semi-molten layer 4 below it is a layer composed of slag droplets, and at the same time, the aggregate leg powder prevents the droplets from agglomerating. The effective electrical conductivity is smaller than the electrical conductivity of the slag melt itself.

The molten slag layer 8 in contact with the molten steel has a much higher electrical conductivity than each of the eight layers mentioned above.Therefore, when measuring the electrical conductivity in the thickness direction of the mold powder deposit layer, it is found that the electrical conductivity is not uniform. Continuity is detected at the boundaries of the mold powder layer structure, and the thickness of each layer can be easily measured and the mold powder deposit layer structure can be determined.

In addition, when a layer having a different phase structure exists in a place where the negative side is exposed to high mK and the other side is exposed to low temperature, the sf distribution within the layer is the reciprocal of the effective thermal conductivity of each different layer structure. It is well known that there is a temperature gradient proportional to
This phenomenon can be explained by the electrical conduction [6119! When applied to the method for detecting the structure of mold powder deposited layers, the following highly accurate data analysis method can be established.

That is, the dependence of the electrical conductivity of the slag on temperature is of the Arrhenius type and can be expressed by the following equation (1).

λ-eXp, (-to/T) ・・・・・・(
1) λX electrical conductivity, Tom: activation energy, T: II
j On the other hand, the temperature distribution of one layer of powder can be expressed by the following linear function (3) with respect to the distance in the thickness direction of the mold powder deposited layer.

r(x,)=A+Bix, --------<
2) T(x): Temperature A: Temperature trap B on the upper surface of the mold powder deposit layer is a constant proportional to the reciprocal of the effective heat conductive layer of the first layer among the different phase structures in the mold powder deposit layer. , X is the distance from the upper surface of the mold powder deposited layer.

From the above equation (1)%(!I), the following equation (8) is derived.

znλ嘱-偱／〒=-に／(A+BL)c)x/ln
λ-(A + Bix) /I! -Bix -・-
・(8) That is, when the reciprocal of the logarithm of electrical conductivity is put in the thickness direction of the mold powder deposited layer,
A linear relationship with a changing gradient is obtained at the position where the layered structure is facilitated.

Therefore, by measuring the distance between the points where the slope of this plot changes, it is possible to accurately measure the thickness of each structural layer, including the thickness of the molten slag layer of the mold powder deposit layer.

However, there has never been a case in which the structure of different layers of slag with different physical states has been detected by measuring electrical conduction, and there is no case in which the structure of different layers of slag with different physical states has been detected by measuring electrical conduction. In this case, the electric conduction length of the slag existing at a specific location in the PcFi system is not measured, and a bare electrode 1 is used as the electrode.

Assuming that this method is used as is to detect the mold powder deposit layer, even if the electrode tip position passes through a discontinuity point in the layer structure, electrical conduction will be detected at a portion other than the electrode tip. The discontinuity in electrical conductivity detected by the electrode tip is buried in the electrical conductivity signal, making it impossible to expect a precise detection of a layered structure.

□゛However, by burying the electrode wire in a rod made of a material whose electrical conductivity is extremely small even at high temperatures and allowing the electrode wire to protrude slightly from the tip of the rod, it is possible to measure local electrical conductivity. As shown in Figure 2, the 10-p 7 for measuring electrical conductivity has extremely low electrical conductivity even at high temperatures, and can greatly increase the detection rate of the mold powder deposited layer structure. A pair of metal wires (W, Mo, Pt, etc.) are embedded in a rod made of, for example, BN, which has high corrosion resistance for both steel and molten steel, and these metal wires are slightly protruded at the tip of the rod to form the electrode 7'.
and a pair of gold 14iI #I[ to configure a normal impedance measurement circuit. In FIG. 1, 8 is a high-frequency voltage transmitter for applying a potential, and 9 is a round resistor that extracts the current flowing in proportion to the electrical conductivity of the medium to be measured between the electrodes 12 of the blowchit as a voltage.
This voltage value is an alternating current signal, which is inconvenient to record, so it is converted to direct current via the φ converter 10, amplified by the DC amplifier 11, and recorded on the later-described position needle 13. It is preferable that the arithmetic circuit 18 process this as a reciprocal of the logarithm and record it on the recorder 14.

GLOBECH uses a poid 16 incorporating an automatic lifting mechanism (as shown) to move the mold powder deposited layer 18 on the self-melting steel of the continuous casting mold up and down at a constant speed while adjusting the electrical conductivity. FIG. 8 shows an example of the gain/loss signal produced by the O recorder 11 that records the voltage signal.

The record in Figure 8 was obtained when the blowbutch was lifted from the molten steel house and moved upward through the mold powder deposit layer, but the changes in the signal that followed the changes in the layer structure were clear. This makes it possible to detect the structure of the powder deposit layer with sufficient accuracy.

That is, in FIG. 8, the signal between 1 and 6 shows a high value and is stable, which indicates that the detection electrode 7' was in molten steel with high electrical conductivity. In this case, the signal gradually decreases, indicating that the electrode 7' is located within the molten slag layer 8.

The sudden signal drop between c- and 6 after drying indicates that the electrode plate is in the semi-fn molten layer 4 directly below the molten slag layer 8, and similarly, K d % e is the sintered layer 5, and e-fr&
Reflecting the fact that J1#i is the solid powder layer 6, here the electrode 7' is exposed to the atmosphere and the electrical conductivity is no longer detected.Meanwhile, the recorder 14 indicates that the obtained electrical conductivity is no longer detected. The fourth graph plots the reciprocal of the logarithm of the conductivity signal against the moving distance of the detection end.
Points of layer structure change corresponding to a-f in FIG.

By the way, in the past, regarding the structure of the mold powder deposit layer, the layer was pumped out as a whole, cooled and solidified, and then cut into pieces and the cross section was examined, but this was done in a destructive test. This method is not practical as a method for detecting the layer structure of mold powder deposits in the process of continuous casting, since various operations are required and time is required to determine whether or not the mold powder is deposited.

On the other hand, according to the present invention, the stratification and structure of the mold powder deposited layer can be determined non-destructively and quickly, and as a result, the continuous casting operation is stabilized. The company is extremely large.

Regarding the Brogou construction used for the above-mentioned electrical conductivity detection, a rod with extremely low electrical conductivity is buried at the tip of the rod with an electrical conductivity as high as that of slag. It is suitable for bulk molded bodies.

Insulators suitable for the main body of gloves include BN, etc., and 8
1. N4,Aj,O,,MjOlZrO,,810j.

BaO or the like may be used, and graphite or other high melting point metals such as Mo, W%Pt, and Ta may be used as the electrode wire.

The electrode spacing of the blowch is 5 to 80 m (preferably around the K2O trend; if it is too narrow, molten slag may bridge between the electrodes and interfere with the detection of stratification).
In this respect, if the electrode exposed surface of the probe is made into a single plane, there is a possibility that the molten slag will adhere to this surface and cause a similar problem, so it is necessary to make it bifurcated as shown in FIG. 8.

For metal INK used for electrodes, the outer diameter is 0.2 to 0.5M.
It seems to be in the range l1, and the tip exposure is 0.5 after ''.
It is preferable to make it about the size of a dragon. An electrode that is too thick also causes bridging S<, tC If the tip is not exposed for a long time, there is a disadvantage of melting. Although the case of detecting a change in K has been described, measuring capacitance in addition to electrical conductivity is also suitable for the purpose of this invention.

That is, the structure of the mold powder deposited layer can be detected from the capacitance detected by the nine electrodes to which an alternating current voltage is applied.

If conditions are selected in which the AC voltage is sufficiently small so that electric polarization does not occur, the detected capacitance will be the capacitance of the interfacial electric double layer. Furthermore, even within the same phase, the value of electric double layer capacitance differs because the mobility of ions that exist near the electrode interface and make up the electric double layer differs depending on the internal temperature. K becomes. Utilizing this principle, by measuring capacitance, it is possible to perform detection similar to measuring layer structure by measuring electrical conductivity.

This pigeonhole electrode plate is connected to an automatic impedance measuring machine so as to constitute the west terminal part of the normal impedance measurement method, and the capacitance component is continuously measured and continuously recorded on the recording needle. The figure shows the good signal obtained in this way as the distance from the molten steel surface to the upper surface of the mold powder deposit layer.

In FIG. 6, the signal between a' and b' indicates that the electrode is within the molten steel.

This corresponds to the fact that the interfacial electric double layer capacity between the electrode and the molten metal is extremely small ◇ On the other hand, the interfacial electric double layer capacity between the molten slag electrode is extremely large and has a positive temperature dependence, so b1~
The area between C' can be determined to be a molten slag layer.

In the molten layer, which is a horizontal layer filled with bath molten slag, the capacitance decreases due to the presence of voids. The capacitance between the electrode and the solid also depends on the porosity of the solid. A large powder layer is determined to be between 6'' and f'.

The method of the present invention can be advantageously applied to the analysis of the structure of the nine mold powder deposited layers listed in each of the above embodiments, but it can also be applied to continuous casting tumble pushers and ladles, as well as various refining vessels. Of course, the method of the present invention can also be advantageously applied to the evaluation of the properties of slag and 7 lux compositions.

Having said the above, according to the present invention, the thickness and other properties of the bath surface coating layer covering the molten metal bath surface can be detected on the spot, and immediate countermeasures can be taken depending on the suitability of the detection. O that can enable the execution of

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the stratified structure of a mold powder deposited layer in a continuous casting mold; FIG. Figure 8 is a graph showing changes in the electrical conductivity of a single layer of mold powder in the direction of thickness of the powder layer.
The figure is a graph showing the change in the powder thickness direction of the signal obtained as the reciprocal of the logarithm by processing the electrical conductivity signal. 15... Guide O Patent Applicant Kawasaki Steel Corporation Figure 1 Figure 2 Figure 3, Figure 4

Claims (1)

[Scope of Claims] 1. To the sea surface coating layer of a molten metal bath, a pair of electrodes made of a material with high corrosion resistance under high temperature are exposed at their tips in a plane parallel to the bath surface to form an insulator with high corrosion resistance from round height to bottom. A probe made of material) is moved in the IK direction vertically penetrating the sea surface coating layer, and due to the electrical properties inherent to the sea surface coating layer, when it penetrates the bath surface coating layer, a change in the electrical signal generated between the IK electrodes is observed. of,
A method for determining the thickness of the bath surface covering layer of a molten metal bath, which is characterized by detecting the movement and displacement of a globe. The final layer, which overlaps through an intermediate layer such as sinter or sinter, is a deposited layer of 7 lux composition including a granular layer, and during the movement displacement of the globe, the electrical properties in each layer of the above stratification are changed. 2. The method according to claim 1, wherein the trend of stratification of the skeleton is detected as a change in the electrical signal derived from the thermal shock of the body. A method according to claim 1 for detecting an intralayer electrotransmission device in a sea surface coating layer as a change in an electrical signal. The method according to claim 3, wherein the capacitance in the bath surface coating layer is detected as a change in the electric signal. The method described in Claim 1!1% m, 8 or No. O a A11i Highly corrosion resistant material, which detects the logarithm of the signal for a good electrical signal and processes its reciprocal as a function of the movement displacement of the globe. A molten metal bath formed by a globe consisting of a bifurcated molded body made of an insulating material with high corrosion resistance at high temperatures, each having an electrode exposed at its tip, and a guide for ensuring a vertical posture with respect to the bath surface coating layer of the 10-plate. An instrument for measuring the thickness of sea surface coating.