JPS60166846A - Measurement of decarburizing reaction in electromagnetic steel plate manufacturing process - Google Patents

Abstract

PURPOSE:To perform the accurate operation control of a decarburizing process by measuring the concns. of steam and CO-gas, by measuring the absorption amounts of electromagnetic wave beam to steam in the vicinity of the surface of a steel plate and CO-gas formed by the reaction of steam and the surface of the steel plate. CONSTITUTION:The electromagnetic wave beam 5 from a beam source 4 transmits a filter 10 passing only a wavelength lambda showing absorbing characteristics to steam to reach a rotary sector 11. Said beam 5 is incident on the interior of a furnace 1' through a window part 11' and propagates through said furnace 1' to be reflected by a reflective mirror 6 while the reflected beam is further reflected by a beam splitter 7 to enter a detector 8. This detection signal is set to I1. The beam 5 is totally reflected by a total reflection mirror 11'' and the reflected beam is reflected by the beam splitter 7 to similarly enter the detector 8. This detection signal is set to I2. In addition, the signal, which is reflected by a total absorbing surface 11''' and detected, is refered as a zero base and set to I3. The mol number (n) of steam per the unit volume in the furnace is calculated by formula. In the formula, alpha is coefficient of attenuation, L is a propagation distance and K is constant. The measurement of CO-gas can be performed in a perfectly similar way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Medical Application) The present invention relates to a method for online measuring the decarburization efficiency in a decarburization annealing furnace in the manufacturing process of electrical steel sheets.

(Prior Art) As is already well known, decarburization annealing is performed in the production of electrical steel sheets, and its main purpose is to primary recrystallize and decarburize the copper sheet, and to generate silica layer scale. In other words, it lies in the formation of an oxide film. Moreover, the formation of the silica layer school and its film properties in this process have a great influence on the subsequent formation of the primary film, that is, the forsterite film, and are important points for the iron loss characteristics of electrical steel sheets as products. .

In such a decarburization annealing process, decarburization is first performed by a reaction between carbon in the steel and water vapor in the atmosphere at C+HxO2CO+Hz, but if the water vapor partial pressure is too high, an oxide film (FeOr Fe5O4, etc.) will form on the surface of the steel sheet. , which inhibits the opportunity for C and HxO to come into contact and suppresses the decarburization reaction, resulting in a severe negative effect on the magnetic properties. In addition, in the latter half of the process, a silica layer scale is formed on the surface of the steel sheet after decarburization, that is, due to the following reaction, etc., 5LOx, 2
Forms an oxide film such as F@0.81 (h).

St + 2HsO-+ SiO snow + 2Hz2Fe
+St +4HsO-+ 2FeO・5to2+ 4)
However, excessive oxidation due to these reactions causes deterioration of adhesion, unnecessarily increased thickness of the surface layer, etc., resulting in deterioration of characteristics and reduction in space factor.

The appropriate composition and amount of these films determine the quality of the glass-like insulating film (referred to as the secondary film), which is mainly made of 7-orsterite (2Mg0.5iOz), through the subsequent high-temperature finishing annealing process. .

In this way, the decarburization annealing step is characterized by allowing both decarburization and oxide film formation reactions to proceed.

Therefore, in order to achieve both sufficient decarburization and appropriate formation of the reaction mixture, careful control of the furnace annealing atmosphere gas, dew point, temperature, time, etc. is important.

For the management of such decarburization reactions, for example,
As disclosed in Japanese Patent No. 43691, the partial pressure ratio PI[, o/PHffi, or dew point of in-furnace steam and water bulk gas has been managed.

However, in the conventional technology, the partial pressure ratio or dew point can be determined by measuring the ratio of water vapor and hydrogen before being extracted into the furnace, or the 3rd edition of the Iron and Steel Handbook, edited by the Iron and Steel Institute of Japan. ■ As shown in No. 561, a Dew Probe that utilizes the moisture absorption saturation characteristics of lithium chloride is attached to the furnace, and the dew point is observed by sucking the atmosphere inside the furnace to the outside of the furnace. I'm yelling. However, the space inside the decarburization annealing furnace is vast and it is natural to think that the partial pressure ratio or dew point varies greatly spatially. Therefore, this method does not involve decarburization and oxide film formation. It cannot be said that the true information that is being captured is captured. In other words, since the decarburization reaction and the formation of an oxidized HL film occur when water vapor existing near the surface of the electrical steel sheet reacts with the surface of the steel sheet, the true information is precisely due to the presence of the surrounding air near the surface of the steel sheet. This means that the situation is as follows. Therefore,
It cannot be said that the control in the prior art described above is sufficient to control the decarburization process of electrical steel sheets. However, until now there has been no suitable means for capturing the above-mentioned true information, and therefore no attempt has been made to control the charcoal reaction using this information.

(@Akira's purpose) In view of the current situation, it is an object of the present invention to provide information that contributes to accurate operational control of the decarburization process of electrical steel sheets. That is, the present invention provides a method for simultaneously measuring the fineness of water vapor near the narrow surface of a steel plate where a decarburization reaction occurs and CO gas, which is a reaction product, or the partial pressure of water vapor and CO gas, or their partial pressure ratio PH! The present invention attempts to provide a method for measuring o/Pco.

(Structure and operation of the invention) When an electromagnetic anti-beam with a sufficient wavelength that exhibits absorption characteristics for water vapor and CO gas propagates in space, the electromagnetic wave is When the absorbed beam t changes, r is used to change the partial pressure or partial pressure ratio of water vapor and CO gas, or both, or the water vapor concentration in the close vicinity of the coating surface of the brazed steel plate in the decarburization annealing furnace. The corresponding dew point is measured. Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows the basic configuration of the present invention, in which small holes are provided on both side walls 2 and 2' of a decarburization annealing furnace 1, and windows 3 that transmit electromagnetic waves so as to prevent the atmosphere inside the furnace from leaking. ,3
Seal with '. On the other hand, a light source 4 of an electromagnetic wave 5 that emits an absorption band wavelength for water vapor and CO gas and a beam splitter are positioned opposite to the electromagnetic wave transmission window 3, and a detector 8 is positioned opposite to the beam splitter 7. establish. Further, a reflecting mirror 6 such as a dolly reflector is provided on the outside of the other electromagnetic wave transmitting window 3'. Therefore,
An electromagnetic wave beam 5 is emitted from a light source 4, for example, a beam outside the door (absorption band of water vapor is 1.39 μm, 1.84 μm).

2.7 tlm, 5.5 to 6.5.4 m, etc., and the CO gas absorption band is 4.6 to 4.7 μm), and the decarburized sintered puree is emitted from the electromagnetic wave transmission window 3. Inside the furnace 1
The beam is propagated so as to pass very close to the next point 9' of the electromagnetic steel plate 9 that undergoes an interfacial reaction with the water vapor of The beam passes through the furnace 1', is taken out of the furnace through the electromagnetic wave transmission window 3, is reflected by the beam splitter 7, and is guided to the detector 8. Although the cross-sectional dimension of this electromagnetic wave beam 5 can be controlled to any dimension by optical technology, it is usually desirable that it be in the range of 0.1 mφ to 50 wφ. Although it is desirable that the distance between the beam and the steel plate surface 9' be as small as possible, in reality there are problems such as vibrations on the surface of the steel plate on which it runs, so it is usually desirable that the distance is 0.1 or more and 100 or less. The wavelength of the electromagnetic beam is 1.39 μ period, which is the absorption band of water vapor.

1.84 μm, 2.7 ttm, 5.5-6
．． There are 4.6 to 4.7 μm for CO2 gas absorption, so use one that meets these standards. The electromagnetic wave intensity detected by the extractor 8 changes depending on the amount of steam in the furnace and the CO gas generated by the decarburization reaction. The dew point corresponding to the pressure ratio and the amount of water vapor can be measured online.

In this case, if the electromagnetic wave beam 5 is passed through the electromagnetic steel sheet 9 in the width direction of the electromagnetic steel sheet 9 in the decarburization annealing furnace 1', water vapor and c in the vicinity of the steel sheet 9 can be reduced.

Since the average value of the gas, that is, the components involved in interfacial reactions, is measured, it becomes possible to perform process control and material control that are completely different from the management of conventional electromagnetic steel decarburization annealing furnaces. Furthermore, since the electromagnetic beam can be detected at a diagonal speed, continuous measurement can be carried out at all times even when the steel plate 9 is traveling in the furnace 1'.

Here, the measurement principle of the present invention will be explained in detail.

Now, the distance 2 of the wavelength λ that exhibits absorption characteristics for water vapor
If the intensity of infrared rays at is Iw (Z), then Lam
According to the Bert-Beer law, hp is generally given by the following equation.

Iw(Z) = Iw(o)eXP C-αw-mW
HZ ) - (1) where w (0) 2 Intensity at z = 0, that is, incident intensity nw: Number of moles of water vapor per unit performance 9 αW: Attenuation coefficient of infrared rays for water vapor Fig, 1, reflected from the light source If the distance to the mirror is t, then
Since the propagation distance is L = 21, substituting Z = L into equation (1), we get: Therefore, the logarithms of both sides are rearranged as 9. In equation (3), L and αW are divided by a constant, so , detection intensity i
The number of moles of water vapor, nW, can be determined from the ratio of w(L,) and the incident intensity Iw(0).

By the way, in Figure 1, it is assumed that the furnace space is an open system, humidifying AX gas is supplied from the outside so that the dew point inside the furnace is kept constant, and the pressure inside the furnace is maintained at 1 atm. . At this time, if the partial pressure of steam in the furnace is Pw, the furnace volume is V1, the number of moles of steam is Nw, and the ambient temperature inside the furnace is T (K), then Pw-V = Nw-ft-T Curve (4) is It will come true. Here R is the gas constant.

In equation (4), the water vapor moles per unit volume are ! Since IW = NW/y, PW is given by the following equation.

p v = nw −R−T −−−−−・−・(5)
In other words, the steam partial pressure PW in the reactor is expressed as JJ by equation (3).
The nw is measured and the furnace temperature T is obtained using equation (5).

Furthermore, as shown in FIG. 2, there is a unique relational expression between the saturated water vapor pressure Pw and the corresponding dew point tw (C), so if Pw is equal, tw can be obtained.

On the other hand, the number nco of moles per unit volume of CO gas in the furnace and its partial pressure pco are also given by the following equations in exactly the same way.

Pco −n Co ・R−T −・− (7) Also, (
From equation 3) and equation (6), equation (8) becomes equation (5) and equation (7).
Equation (9) is obtained from Eq.

In particular, equation (9) is a ratio of the partial pressure of water vapor, which is the cause of interfacial reaction, and the partial pressure of CO gas produced by the reaction, and is therefore an appropriate index representing the reaction state.

Figure 3 shows a professional diagram of the measurement system.

The above is the principle of the present invention. FIG. 4 shows an example of a configuration embodying this principle. In FIG. 4, an electromagnetic wave beam 5 from a light source 4 passes through a filter 10t that passes only a wavelength λ exhibiting absorption characteristics for water vapor, reaches a beam splitter 7, and then reaches a rotating sector 11.

The sector l↓ has a completely transparent window portion 11', a total reflection mirror LLN and a total absorption surface 11''. Sector 11
rotates and when the window portion 11' comes into the optical path of the electromagnetic wave beam 5, the beam 5 propagates into the furnace 1', is reflected by the reflection mirror 6 provided on the furnace side wall 2', and returns to its original state. The optical path is returned and reflected by the beam splitter 7 to the detector 8.
to go into. This detection signal is set to 11. Also sector 11
When the total internal reflection of 2-i 1' is in the optical path, the beam 5
is totally reflected there, reflected by the beam sinter 7, and similarly enters the detector 8. This detection signal is assumed to be 2. Furthermore, when the total absorption surface 11/# is in the optical path, the signal reflected and detected here is assumed to be the zero base. Each detection signal can be written as follows.

If = ks Ia (0) @XF (-αn'Z
o−αn L)+I b−=αQ−I! = kg l
2(0) exp (-αn'Zo) + Ib -
・・・=・Al Kobatake=Ib ・・・・・・・・・(6) Here, kl r kz is a constant including the reflectance of the mirror and the geometric coefficient of the optical system. n/ is the rotation. sector 11
and the optical path distance between the beam splitter 7 and the detector 8,
Ib is a detection noise value including ambient background light. Four to (6)
If we create the formula jJ(It Is)/(Iz l5)k, (
2) Formula: where k=total/kt=(constant).

That is, the number of moles of water vapor per unit volume in the furnace, n, is calculated by the formula α◆. Therefore, the calculation mechanism 12 connected to the detector 8
By performing the above calculation, the value can be immediately obtained (see Figure 3). In this configuration, it is of course important that the beam 5 propagate near the surface 9 of the electromagnetic steel sheet.

Although the method for measuring water vapor has been described above as an example of the configuration, the measurement of CO gas can be carried out in exactly the same manner. Alternatively, both absorption wavelength beams can be propagated on the same optical path so that both @ can be measured simultaneously.

(Example) Next, examples of the present invention will be shown.

(Example 1) A measurement and sequence of water vapor according to the present invention is shown. In the configuration shown in FIG. 4, a halogen bulb is used as the light source 4, and as the filter 10, λ=1.39 μm1 half width Δλ=0.15
A μm interference filter was used.

The beam 5 was propagated at a distance of 10 m from the material surface 9' with a beam diameter of 3 mm. Germanium (G) is used as the detector 8.
o) The element was used.

A fixed amount of N2 gas containing water vapor was supplied into an open furnace set at an ambient temperature of 820° C. 1 Using the above-described configuration, the number of moles of water vapor in the furnace and its water vapor pressure were measured. As the number of moles per unit volume nW, n = 3.5 m
When the water vapor partial pressure was measured according to equation (5), Pv = 0.32 24 in atm.
It was 0 easy H. Furthermore, when the dew point was determined from this h according to Figure 2, it was found to be 70°C during tw.9 On the other hand, when the gas inside the furnace was sucked out of the furnace and the dew point was measured with a commercially available lithium chloride dew point meter, it was found to be 71°C. there were. Since both dew point measurements were in close agreement, it was verified that the measurement of water vapor molar ambiguity and water vapor partial pressure by this method was correct.

(Example 2) Similarly, CO gas measurement was attempted using the configuration shown in FIG. A blackbody furnace at 800° C. was used as the light source 4, and an interference filter of 224.68 m1 Δλ=0.1 μm was used as the filter io. Also, as a detector 8, HgCd'
A PE element was used. 1. Supply CO gas from a cylinder into a furnace set at room temperature so that the molar concentration is nco"" 1.8 mol/In'. With the above configuration, α◆
When we measured the CO gas molarity corresponding to the formula, we found that n(
0 = 1.9 mol 7m'' was a value close to the supply molar concentration. Substituting this value into equation (7), the partial pressure of CO gas PCO = 0.047 atm = 35.7 +
I got the wfig.

(Example 3) A measuring device with the configuration of Examples 1 and 2 was prototyped and installed on the wall of a continuous decarburization annealing furnace for electromagnetic steel. The average dew point of lO■) and the average CO gas surface level were continuously monitored for a long time, and the results shown in FIG. 5 were obtained. From this result, it is clear that the CO gas degree changes with time. This measurement was carried out under normal sitting conditions, so the changes in both signals were small, but when an abnormal signal occurred (the line speed changed or the temperature changed), this measurement signal was immediately used. By controlling this, a Q-stable decarburization annealing process can be realized.

In these examples, a nitrogen lamp or a blackbody furnace was used as a light source, but other light sources such as a xenon lamp or a nitrogen lamp, a semiconductor laser, a C(h laser), etc. A tunable laser can also be used. Also, a wavelength band in the microwave region that exhibits absorption characteristics for water vapor and CO gas can also be used.

However, this method accurately measures the progress of the decarburization state of the electrical steel sheet, that is, the progress of the interfacial reaction, by carrying out the method at multiple locations in the longitudinal direction (travel direction of the steel sheet) of the decarburization annealing furnace. be able to.

(Effect of % light) As explained above, the present invention detects the concentration of water vapor and CO gas near the next surface of the electrical steel sheet in the decarburization annealing furnace, and corresponds to the respective partial pressures and partial pressure ratios, as well as the amount of water vapor. It is possible to measure the dew point, and this information is information on interfacial reactions that directly affect the quality of electrical steel sheets.
It provides a new decarburization reaction measurement that did not exist before, and has great effects such as being able to utilize fixed values of various states for the decarburization annealing process or quality control of the electrical steel sheet.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the measurement principle of the present invention, Figure 2 is a graph showing the relationship between saturated vapor pressure and dew point, Figure 3 is a block diagram of the measurement system of the present invention, and Figure 4 is a diagram of the method of the present invention. An explanatory diagram showing an example, FIG. 5 shows the measurement results of the average dew point and average CO gas concentration near the steel plate in a 14L magnetic steel continuous coal-burning annealing furnace to which the present invention is applied. 1: Decarburization annealing furnace, 1': Inside the decarburization annealing furnace, 2.2': Side wall, 3.3': Electromagnetic wave transmission window, 4: Light source, 5: Electromagnetic wave beam, 6: Reflection mirror, 7: Beam splitter -, 8: Detector, 9: Electromagnetic steel plate, 9': Electromagnetic steel plate surface, 10: Filter, 11: Rotating sector, 11': Transmission window part, 1
1": Total reflection mirror, 111y/+, total absorption surface. Applicant: Minoru Aoyagi, Patent Attorney, Shin Nihon MM Co., Ltd. Figure 2 0 20 40 60 80 (00 (・c) Dew point Figure 3 Procedure Amendment (Voluntary) Display of the case dated March 10, 1985 Patent Application No. 9192 λ of 1985 Name of the invention Method for measuring decarburization reaction in the manufacturing process of electrical steel sheet 3, person making the amendment Relationship with the case Patent applicant address 2-6-3 Otemachi, Chiyoda-ku, Tokyo Name (6
65) Nippon Steel Corporation Representative Takeshi 1) Yutaka 4, Agent 〒101 8. Contents of amendment (1) The following sentence is inserted between lines 14 and 15 on page 11 of the specification. “Here, Ico(0): Incident intensity corresponding to the CO gas absorption wavelength at distance z=:0 Ico(Z): Incident intensity corresponding to the CO gas absorption wavelength at distance 2 αco: Attenuation coefficient of infrared rays for CO gas.” (2)
"(See Figure 3)" on page 14, line 5 is corrected to "(See Figures 3 and 4)." (3) Correct the drawings in Figures 3 and 4 as shown in the attached sheet.

Claims (4)

[Claims] (1) Near the surface of the electrical steel sheet located in the decarburization annealing furnace,
An electromagnetic wave beam having a wavelength that exhibits absorption characteristics for water vapor and CO gas is passed through, and the amount of absorption of the electromagnetic wave beam by water vapor near the surface of the steel sheet and CO gas generated by the reaction between the water vapor and the surface of the steel sheet is measured. A method for measuring a decarburization reaction in an electrical steel sheet manufacturing process, which is characterized in that the concentration of water vapor and CO gas is measured. (2) T located in the decarburization annealing furnace! An electromagnetic wave beam having a wavelength that exhibits absorption G properties for water vapor and CO gas is passed near the surface of the electrical steel sheet, and the water vapor near the surface of the steel sheet and the CO gas generated by the reaction between the water vapor and the surface of the steel sheet are A method for measuring a decarburization reaction in an electrical steel sheet production process, characterized by measuring the concentration of water vapor and CO gas by measuring the absorption f of an electromagnetic wave beam, and further calculating their respective partial pressures and partial pressure ratios. (3) Near the surface of the electrical steel sheet located in the decarburization annealing furnace,
An electromagnetic wave beam having a wavelength that exhibits absorption characteristics for water vapor and CO gas is passed through, and the concentration of the electromagnetic wave beam is measured by measuring the absorption cap of the electromagnetic wave beam for the water vapor near the surface of the steel sheet, and the dew point can be determined from the concentration. A method for measuring decarburization reactions in the manufacturing process of electrical steel sheets. (4) A method for measuring a decarburization reaction in an electromagnetic steel sheet manufacturing process according to claims 1 to 3, characterized in that an electromagnetic wave beam is passed in the width direction of the electromagnetic steel sheet.