JPH0587714A - Method and device for measuring quality of cold rolling thin steel plate - Google Patents

Abstract

PURPOSE:To obtain a method and device for measuring a quality by obtaining a modulus of elasticity of a cold rolling thin steel plate and a Lankford value non-destructively. CONSTITUTION:A value of a ratio of a thickness resonance frequency of a transversal ultrasonic wave which propagates in a thickness direction while vibrating in a direction parallel with a rolling direction within a cold rolling thin steel plate to a thickness resonance frequency of a longitudinal ultrasonic wave which propagates in a thickness direction, and a value of a ratio of a thickness resonance frequency of a transversal ultrasonic wave which propagates in a thickness direction while vibrating in a direction perpendicular to a rolling direction within the cold rolling thin steel plate to a thickness resonance frequency of a longitudinal ultrasonic wave which propagates in a thickness direction are measured. A modulus of elasticity of the above cold rolling thin plate and Lankford value (r value) are obtained based on the two types of measured rations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for rapidly and nondestructively measuring the material of a cold-rolled thin steel sheet off-line, and an apparatus therefor, or a method for nondestructively measuring on-line rolling. And the apparatus.

[0002]

2. Description of the Related Art Cold-rolled thin steel sheets are required to have high press formability because they are used for exteriors of automobile bodies and household electric appliances. Cold-rolled thin steel sheet is a polycrystalline body, and its press formability is mostly determined by the so-called texture. Conventionally, press formability has been estimated by the X-ray pole figure method or the Rankford value (r value). However, in the X-ray pole figure method, it takes time because it is necessary to cut a test piece from a cold-rolled thin steel sheet and irradiate it with X-rays for measurement.
Furthermore, it is a destructive measurement method because the test piece must be cut off. On the other hand, the method for measuring the Rankford value requires time because it requires precise measurement of the change in size of the tensile test piece, and it is also destructive because the test piece must be cut from the cold-rolled steel sheet. It can be said to be a measurement method. Proposed a simple method (CAStickels and Moul
d, "The use of Young's modulus for predicting the p
lastic strain ratioof low carbon steel sheets ", Met
Allurgical Transaction Vol.1, pp1303-1312 (1970)), but this method is simple because it uses the empirical correlation between Young's modulus and Rankford value measured by the eigenvibration method. This method is also a destructive measurement method because the test piece must be cut from the cold-rolled thin steel sheet and measured.

Therefore, a method of measuring the sound velocity of ultrasonic waves has been proposed as a method for nondestructively measuring the natural size of a cold-rolled thin steel sheet without the need to cut a test piece. In the method of obtaining the Young's modulus or Rankford value of a cold-rolled thin steel sheet by a nondestructive measurement method (for example, Japanese Patent Application No. 1-29755), the values of K ₁ and K ₂ are measured by a resonance type electromagnetic ultrasonic sensor. At the same time, the velocity V of the SH0 plate wave ultrasonic wave propagating inside the cold-rolled thin steel plate in a direction forming 45 degrees with the rolling direction.
_SHO (45 °) and propagates in the direction forming an rolling direction and the direction parallel or perpendicular SH0 plate wave ultrasonic velocity V _SHO (0
°) or the value of V _SHO (90 °) ratio, K ₃ , must be measured by SH0 plate wave ultrasonic wave of the electromagnetic ultrasonic sensor method.
Requires a H0 plate wave ultrasonic sensor. In particular, it is difficult to make compact because the above-mentioned two sets of sensors are required as the SH0 plate wave ultrasonic wave sensor for measuring K ₃ , and in the case of online non-contact measurement, the SH0 plate wave ultrasonic wave is used. There are problems such as difficulty in stable generation and detection.

Further, in the invention of a deep drawability evaluation apparatus for a thin metal plate (for example, Japanese Patent Laid-Open No. 1-214757), ultrasonic waves of S ₀ mode are propagated in directions of _0, 45, and 90 degrees with respect to the rolling direction, and a certain distance is maintained. The Rank Ford value is obtained by measuring the time it takes to propagate. In this method, three sets of transmitting electromagnetic ultrasonic sensors and receiving electromagnetic ultrasonic sensors are required, and the entire transmitting / receiving device becomes large, 30 cm × 30 cm or more,
Inconvenient to handle.

Other inventions (for example, JP-A-64-83)
In 322), the sound velocity of three kinds of ultrasonic waves propagating in the same plate thickness direction as in the present invention is measured, and the value K of the ratio of the average sound velocity of two kinds of transverse waves to the longitudinal wave sound velocity is calculated. It has been shown that this K is related to the crystal orientation coefficient W ₄₀₀ and the in-plane average Rank Ford value. Actually, a quadratic regression equation of K and the in-plane average Rank Ford value was obtained from an experimental formula. , K, we are trying to estimate the in-plane average rank Ford value. However, in this method, the ratio of the longitudinal sound velocity to the average sound velocity of two types of transverse waves is taken, so there is only one data, and the crystal orientation coefficient W
_{Since 420} and W ₄₄₀ are not taken into consideration, it is thought that the accuracy will drop. It is generally difficult to measure online the propagation time or the sound velocity in the thickness direction of a thin metal plate having a thickness of about 1 mm or less with high accuracy of relative accuracy of about 1/1000. Further, according to the embodiment, the thin metal plate and the ultrasonic probe are brought into contact with each other for measurement, which is not suitable for online measurement.

[0006]

SUMMARY OF THE INVENTION In order to solve the problem of non-destructive, non-contact online measurement with high accuracy using a compact sensor, the present invention has the above-mentioned resonance frequency ratios K ₁ and K ₂ . An object of the present invention is to provide a method for obtaining an in-plane average value of Young's modulus or an in-plane average value of Rankford value of a cold-rolled thin steel sheet from measured values and three elastic moduli of iron single crystals, and a measuring device therefor. To do.

[0007]

SUMMARY OF THE INVENTION The invention features the following methods and apparatus. (1) The thickness resonance frequency of transverse ultrasonic waves propagating in the thickness direction while vibrating in the direction parallel to the rolling direction inside the cold-rolled thin steel sheet, and the thickness resonance frequency of longitudinal ultrasonic waves propagating in the thickness direction. Ratio value and thickness of transverse ultrasonic waves propagating in the thickness direction while vibrating inside the cold-rolled thin steel sheet in a direction perpendicular to the rolling direction and resonance frequency and thickness of longitudinal ultrasonic waves propagating in the thickness direction. A method for measuring the material of a cold-rolled thin steel sheet, which comprises measuring a value of a ratio with a resonance frequency and obtaining the Young's modulus and Rankford value of the cold-rolled thin steel sheet based on the measured values of the two kinds of ratios.

(2) The process of measuring the ratio and value of the two types, and the sound velocity of the SH0 plate wave propagating in the cold-rolled thin steel plate in a direction forming 45 ° with the rolling direction and the direction parallel to the rolling direction. Alternatively, from the process of considering the ratio of the sound velocity of SH0 plate wave propagating in the direction perpendicular to a constant value as a constant value and the value of the above three types and the known elastic modulus of the iron single crystal, The method for measuring a material according to (1), including a step of approximately calculating an in-plane average value of the rate and the Rankford value.

(3) The electromagnetic resonance apparatus including at least a resonance type electromagnetic ultrasonic wave sensor is used to generate and detect the two kinds of transverse wave ultrasonic waves and the one kind of longitudinal wave ultrasonic waves, and the thickness resonance type frequency. The material measurement method according to (1), wherein the value of the ratio is measured.

(4) The electromagnetic ultrasonic device comprises a coil for passing a high-frequency current for inducing an eddy current in the cold-rolled thin steel sheet, a magnet for applying a predetermined magnetic field to the cold-rolled thin steel sheet, and the vortex. The resonance-type electromagnetic supersonic wave detecting the two kinds of transverse ultrasonic waves and the one kind of longitudinal ultrasonic waves generated by an electromagnetic force generated in the vicinity of the surface of the cold-rolled thin steel sheet due to an interaction between an electric current and the magnetic field. An ultrasonic wave sensor, generating and detecting the transverse ultrasonic waves and the longitudinal ultrasonic waves while sweeping the frequency of the high-frequency current flowing in the coil, and recording the frequency when the detected ultrasonic waves reach a maximum. (3) The material measuring method according to (3), wherein the three types of thickness resonance frequencies are obtained by:

(5) An operation for calculating the Young's modulus and Rankford value of the cold-rolled thin steel sheet based on the electromagnetic ultrasonic wave device and the value of the ratio of the thickness resonance frequency measured by the electromagnetic ultrasonic wave device. (3) The cold rolling thin steel sheet material measuring device according to (3), further comprising: a device, and a copying device including a copying mechanism for making a gap between the resonance type electromagnetic ultrasonic sensor and the cold rolling thin steel plate constant.

(6) Since the electromagnetic ultrasonic device generates two kinds of transverse ultrasonic waves and one kind of longitudinal ultrasonic waves in the cold-rolled thin steel sheet, a frequency for outputting a high frequency current while sweeping the frequency. An analysis device and a resonance type electromagnetic ultrasonic sensor for detecting the transverse ultrasonic waves and the longitudinal ultrasonic waves, and from the signals detected by the resonance type electromagnetic ultrasonic sensor, the high frequency output from the frequency analysis device The material measuring device according to (5), wherein a signal having the same frequency component as the current is extracted by the frequency analysis device to obtain the value of the thickness resonance frequency ratio.

[0013]

The thickness resonance frequency f _zx of the transverse ultrasonic wave propagating in the thickness direction while vibrating in the direction parallel to the rolling direction inside the cold-rolled thin steel sheet using only the resonance type electromagnetic ultrasonic sensor and in the thickness direction The ratio K _{2 of} the propagating longitudinal ultrasonic wave to the thickness resonance frequency f _zz , and the thickness resonance of the transverse ultrasonic wave propagating in the thickness direction while vibrating inside the cold-rolled steel sheet in a direction perpendicular to the rolling direction. The ratio K ₁ between the frequency f _zy and the thickness resonance frequency f _zz of the longitudinal ultrasonic wave propagating in the thickness direction is measured, and the in-plane average value of the Young's modulus or the in-plane of the Rankford value is calculated by an approximate calculation formula. The average value can be obtained.

First, Japanese Patent Application No. 1-2975 discloses a method for calculating the in-plane average value of Young's modulus by using the above K ₁ , K ₂ and K ₃ .
5 or literature (Katsuhiro Kawashima, "Nondestructiv
e characterization of texture and plastic strain r
atio of metal sheetswithelectromagnetic acoustic t
ransducers "J.Acoust.Soc.America Vol.87, No.2, Februa
ry 1990, pp681-690), and then K ₁ , K ₂
The method of the present invention for approximating the in-plane average value of Young's modulus only by the measured value of is shown.

First, the theoretical background will be described in accordance with the invention of the above-mentioned application. The cold-rolled thin steel sheet is a polycrystalline body composed of many fine iron single crystals (cubic crystals), but when viewed macroscopically, it can be regarded as a continuous body having anisotropy. The thin steel sheet regarded as a continuum is approximately three planes orthogonal to each other (1. rolling plane (xy plane), 2. planes perpendicular to the rolling plane and parallel to the rolling direction (xz plane), 3. It is considered to have plane-symmetrical physical properties with respect to a plane (yz plane) perpendicular to the rolling plane and perpendicular to the rolling direction. However, x is the rolling direction and corresponds to the longitudinal direction of the thin steel sheet. y is a direction perpendicular to this and corresponds to the width direction of the thin steel sheet. z is a direction perpendicular to both x and y, and corresponds to a direction perpendicular to the plane of the thin steel sheet. In such a case, it is already known that the elastic modulus matrix of a thin steel plate has nine different elastic moduli, which can be expressed as follows.

[0016]

[Equation 1]

Here, C _ij represents nine different elastic moduli of the thin steel sheet. On the other hand, the ratio of those having a certain direction (θ, ψ, φ) to the thin steel plate among the many single crystals constituting the polycrystal is the crystal orientation distribution function W (ξ, ψ, φ)
It is known that it can be represented by (hereinafter referred to as CODF) (RJRoe, "Description of crystallite orientatio
n in applied materials ", Journal of Applied
Physics, Vol.36, pp2024-2031 (1965)). Where ξ = cos
θ. It is also known that W (ξ, ψ, φ) can be represented by a series expansion by the generalized Legendre function Z _lmn as in the following equation (2).

[0018]

[Equation 2] Here, θ, ψ, and φ are Euler angles used to represent the relationship between the single crystal and the thin steel plate. Further, ξ = cos θ. W (ξ, ψ, φ) is a function expressing the ratio of the amount of a single crystal having a certain direction (θ, ψ, φ) to a thin steel plate and is called a crystal orientation distribution function. W _lmn is a CODF coefficient. Of these, W ₄₀₀ , W ₄₂₀ , W ₄₄₀
Is known to be related to the elastic properties of polycrystalline bodies.

In the case of cold rolled thin steel sheet, as described above, 9
Have different elastic moduli C _ij , but these have 6 independent variables, namely the three elastic moduli C ⁰ ₁₁ , C of the iron single crystal.
⁰ ₁₂ , C ⁰ ₄₄ and three CODF coefficients W ₄₀₀ , W ₄₂₀ , W
It is known to be expressed by the following formula (3) by ₄₄₀ (CMSayers, "Ultrasonic velocities in ani
sotropic aggregates ", Journal of Ph
ysics D, Vol.15, pp2157-2167 (1982)).

[0020]

[Equation 3] Here, the CODF coefficients W ₄₀₀ , W ₄₂₀ and W ₄₄₀ are as shown in the following equations (4), (5) and (6).

[0021]

[Equation 4]

The various modes of ultrasound associated with the present invention are shown in FIG. The thick arrow indicates the propagation direction of ultrasonic waves, and the thin arrow indicates the vibration direction of ultrasonic waves. These arrows are drawn on the outer side of the thin steel plate, but it is for convenience, and it goes without saying that all the actual ultrasonic waves propagate inside the thin steel plate. V _zz is the sound velocity of a longitudinal wave propagating in the plate thickness direction, V _zx is the sound velocity of a transverse wave which is deflected in the rolling direction and propagates in the plate thickness direction, V _zy
Represents the sound velocity of a transverse wave that is deflected in the direction perpendicular to the rolling direction and propagates in the plate thickness direction. V _SHO (0 °) is the sound velocity of SH0 mode plate wave that is deflected in the direction perpendicular to the rolling direction and propagates in the rolling direction in the rolling direction, and V _SHO (90 °) is deflected in the rolling direction and the rolling direction is in the rolling direction. V _SHO (45 °) represents the speed of sound of the SH0 mode plate wave propagating in the direction perpendicular to, and V _SHO (45 °) represents the speed of sound of the SH0 mode plate wave propagating in the rolling plane in the direction of 45 ° with the rolling direction. The resonance frequency ratios K ₁ and K ₂ are obtained by using the equations (7) and (8), and the sound velocity ratio K ₃ is obtained by using the equation (9).

[0023]

[Equation 5]

Here, f _zym , f _zxn , and f _zzl are the m-th resonance frequency and rolling direction of transverse ultrasonic waves that propagate in the thickness direction of the cold-rolled steel sheet and vibrate in a direction perpendicular to the rolling direction. It is the n-th resonance frequency of the transverse ultrasonic wave oscillating in the direction parallel to and the 1-th resonance frequency of the longitudinal ultrasonic wave oscillating in the thickness direction.

The velocity of sound when the traveling direction of the SH0 plate wave coincides with the rolling direction is V _SHO (0 °), and the velocity of sound when the traveling direction is 45 ° with the rolling direction is V _SHO (45 °).
And t ₀ and t ₄₅ are times required to propagate the same distance when the traveling direction of the SH0 plate wave is 0 ° and 45 ° with the rolling direction, respectively.

Although equations (4) and (5) have already been known (CMSayers and DRAllen, "The influence of stress"
on the principal polarization directions of ultra
sonicshear waves in textured steel plates ", Journal
of Physics D, Vol.17, pp1399-1413 (1984)), formula (6) was first discovered by Japanese Patent Application No. 1-29755. According to the equations (4), (5) and (6), the values of three elastic coefficients (C ⁰ ₁₁ = 23) of the already known iron single crystal are known.
_{^{7GPa, C 0 12 = 141GPa,}} C 0 44 = 116GPa) resonant frequency ratio By utilizing K _1, K _2, and the sound velocity ratio K ₃
All of W ₄₀₀ , W ₄₂₀ , and W ₄₄₀ can be obtained by calculation simply by measuring If W ₄₀₀ , W ₄₂₀ , and W ₄₄₀ are obtained, by substituting them into equation (3),
It is possible to obtain individual elastic coefficients C _ij .

It is well known that the Young's modulus E (α) of a thin steel sheet in the rolling plane in the direction forming an angle α with the rolling direction can be expressed by the following equation (10) (F. Boric and GAAl).
ers, "Measurement of the elastic properties of roll
ed sheet "Trans.Metal.Soc.AIME 233,7-11 (1965)). 1 / E (α) = S ₂₂ sin ⁴ α + S ₁₁ cos ⁴ α + (S ₆₆ + 2S ₁₂ ) sin ² α cos ² α ( 10) However, S ₁₁ = (C ₂₂ C ₃₃ -C ₂₃ ² ) S S ₂₂ = (C ₁₁ C ₃₃ -C ₁₃ ² ) S S ₁₂ = (C ₁₃ C ₂₃ -C ₁₂ C ₃₃ ) S S ₆₆ = 1 / C ₆₆ S = 1 / (C ₁₁ C ₂₂ C ₃₃ + 2C ₁₂ C ₂₃ C ₁₃ −C ₁₁ C ₂₃ ²
-C ₂₂ C ₁₃ ² -C ₃₃ C ₁₂ ² )

It can be obtained by substituting the nine elastic coefficients C _ij of the thin steel sheet obtained by the above method into the equation (10) and calculating the Young's modulus E (α). The average value of the Young's modulus in the rolling plane is calculated using the following equation (11). E = [E (0 °) + 2E (45 °) + E (90 °)] / 4 (11)

Next, the method proposed in the present invention, that is, K
_A method for approximating the in-plane average value of Young's modulus from the measured values of ₁ , K ₂ , the sound velocity ratio K ₃ regarded as constant, and the three elastic coefficients of the iron single crystal is shown. (3), (4),
As can be seen from the equations (5), (6), (10) and (11), the Young's modulus represented by K ₁ , K ₂ and K ₃ is the parameters K _P · K _M and K _{3 of the} equation (12). It is represented by.

[0030]

[Equation 6]

As a result of measuring 500 cold-rolled thin plates, K _P =
0.32 to 0.37, K _M = -0.04 to 0.0, K ₃
= 0.94 to 1.024. Therefore, for the combinations of the parameters K _P , K _M , and K ₃ of 5 points at equal intervals within the above range, for a total of 125 points, the above (3) to (1
FIG. 3 shows the simulation result calculated by substituting into the equation (2). As can be seen, the in-plane average value of Young's modulus is three variables K ₁ , K ₂ , K ₃ , or K _P , K _M , K.
_Although it is a function of ₃ , the contribution rate of K ₃ is very small, and at K _P , K _M , and K ₃ in the above range, the change in the in-plane average value of Young's modulus is about 0.2 GPa. Therefore, K ₃ = 0.96
If so, the Young's modulus error is ± 0.6 GPa at most, and the Young's modulus is ± 0.09% with respect to 240 GPa. The same result is obtained by using the average value obtained by integrating E (α) in the equation (10) without using the average value in the equation (11). K like this
_The in-plane average value of the Young's modulus can be approximately calculated only by _P , K _M, that is, K ₁ , K ₂ . Measured values of K ₁ and K ₂ and K ₃ =
In-plane mean value of Young's modulus approximated by 0.96 and K ₁ ,
FIG. 4 shows the strong correlation with the in-plane average value of Young's modulus calculated strictly from K ₂ and K ₃ . Using this result, the in-plane average value of the Rankford value can be obtained by further approximating the empirical relationship between the Young's modulus and the Rankford value using the least square method.

Next, a method of measuring the resonance frequency ratios K ₁ and K ₂ will be described. Thickness resonance frequencies f _zz , f _{zx of} ultrasonic waves propagating in the thickness direction in a thin steel plate having a thickness of 2 mm or less,
It is already known that the standing wave method (also referred to as “thickness resonance method”, hereinafter referred to as “resonance method”) using electromagnetic ultrasonic waves is suitable for measuring f _zy (SAFillim).
onov, BABudenkov, and NAGlukhov, "Ultrasonic cont
actless resonance testing method ", Soviet Journal o
f Nondestructive Testing, No.1, pp102-104 (1971)).
FIG. 2 shows an electromagnetic ultrasonic sensor for this resonance method. FIG. 2A is a sectional view seen from the front. This electromagnetic ultrasonic sensor has a rotationally symmetrical structure. FIG. 2 (b) is viewed from above and shows the eddy current, electromagnetic force, etc. generated by this electromagnetic ultrasonic sensor. When a high frequency current is applied to the flat circular coil shown in FIG.
φ induces. On the other hand, a magnetic field is generated in the thin steel plate by the permanent magnet. The magnetic field has a component Bz perpendicular to the surface of the thin steel plate,
It has a component Br that is distributed in parallel and radially to the surface of the thin steel sheet. Due to the interaction between Iφ and Bz, an electromagnetic force Fr that is distributed radially and parallel to the surface of the thin steel sheet is generated. Also I
An electromagnetic force Fz perpendicular to the surface of the thin steel sheet is generated by the interaction between φ and Br. The electromagnetic force Fr is a component Fx parallel to the rolling direction.
And the component Fy perpendicular to the rolling direction can be divided. F
A longitudinal wave V _zz propagating in the sheet thickness direction is generated by z, a transverse wave V _zx is deflected by Fx in the rolling direction and propagating in the sheet thickness direction, and is deflected in a direction perpendicular to the rolling direction by Fy. A transverse wave V _zy that propagates in the _{vertical direction} is generated. The above-mentioned permanent magnet is for generating a magnetic field in the thin steel plate, and may be used in place of the electromagnet.

The ultrasonic waves thus generated are detected in the opposite physical process. The frequency of the high-frequency current flowing in the coil is f = nV / (2d) (V = sound velocity, d = plate thickness, n = integer)
It is known that a standing wave is generated in the thickness direction of a thin steel plate when the above condition is satisfied. The frequency represented by this formula is obtained by generating and detecting ultrasonic waves according to the above process while sweeping the frequency of the high frequency current flowing in the coil, and recording the frequency at which the detected ultrasonic waves reach their maximum. be able to. A method of detecting a resonance frequency by applying a broadband pulse current to the resonance type electromagnetic ultrasonic sensor to generate an electromagnetic ultrasonic wave and Fourier-transforming a received signal may be used. In this case, frequency sweep is not necessary. According to the equations (7) and (8), since it is the resonance frequency ratio, it can be seen that the thickness d of the thin steel plate is erased and it is not necessary to measure. Since the measurement of the thickness d of a wide thin steel sheet requires measurement by X-ray or the like, the fact that this is not necessary is very preferable in practical use.

Finally, a method for obtaining the in-plane average value of Young's modulus or the in-plane average value of Rankford value by measuring the resonance frequency ratios K ₁ and K ₂ of the cold-rolled thin steel sheet during online threading will be described. Nominal plate thickness for measuring two resonance frequencies of n-th transverse ultrasonic wave and one resonance frequency of (n / 2) th longitudinal ultrasonic wave using the resonance electromagnetic ultrasonic sensor,
By setting the measurement frequency band from the approximate values of the three types of ultrasonic sonic speeds and sweeping the frequency in this frequency band, the above three types of resonance frequencies can be measured, and K ₁ and K ₂ can be measured. Since this measurement time can be 0.01 seconds or less, it can be assumed that the material of the thin steel sheet that runs during this time is constant and the plate thickness is constant. Therefore, the in-plane average of Young's modulus or Rank-ford average is obtained. You can get the value. A wideband pulse current may be applied to this electromagnetic ultrasonic sensor to generate an electromagnetic ultrasonic wave, and the received signal may be Fourier transformed to detect the resonance frequency, and a method of measuring K ₁ and K ₂ may be used. ..

[0035]

[Examples] With respect to 100 thin steel sheets, K ₁ and K ₂ were actually measured using a resonance type sensor, and K ₃ = 0.96 was set, and an in-plane average value of Young's modulus was approximately obtained. According to the method described in Japanese Patent Application No. 1-29755, K ₁ , K ₂ , K ₃
FIG. 4 shows a comparison with the in-plane average value of Young's modulus which was measured and strictly determined. 10 measured by the approximate method of the present invention
Average value of Young's modulus of 0 thin steel plate in the rolling plane (=
[E (0 °) + 2E (45 °) + E (90 °)] / 4)
And Rankford value (r
Value) within the rolling surface (= [r (0 °) + 2r
The relationship with (45 °) + r (90 °)] / 4) is shown in FIG. When the relational expression of Young's modulus and Rankford value is quadratic-approximated by the method of least squares, the standard deviation of the residual is about 0.1, and the average value of the Rankford value in the rolling plane can be obtained. FIG. 6 shows a comparison between the Rankford value (r) obtained by the method of the present invention and the Rankford value obtained by the tensile test.

Next, FIG. 7 shows an outline of a measuring system for measuring the above K ₁ and K ₂ online to obtain the in-plane average value of Young's modulus or the in-plane average value of Rankford value. Reference numeral 1 denotes a host computer, which transmits and receives steel plate information (for example, steel plate number, plate thickness, plate thickness resonance frequency, etc.) of cold rolled thin steel plates and measurement results. 2 is a calculator of measuring device, 3
Is a transmission amplifier, 4 is a resonance type electromagnetic ultrasonic sensor, 5 is a copying device, 6 is a cold-rolled thin steel plate, 7 is a reception amplifier, 8 is a gate,
9 is a frequency analyzer, 10 is an entrance side bridle roll, 11
Is the outgoing bridle roll. The calculator 2 of the measuring device controls the frequency analyzer 9, calculates the resonance frequency ratios K ₁ and K ₂ using the data obtained from 9, and calculates the Young's modulus and the Rankford value. The electromagnetic ultrasonic device includes a transmission amplifier 3, a resonance type electromagnetic ultrasonic sensor 4, a reception amplifier 7, and a gate 8. The copying apparatus 5 is for making a gap between the resonance type electromagnetic ultrasonic sensor 4 and the cold rolled thin steel sheet 6 constant or for raising and retracting the gap. The bridle rolls 10 and 11 are for suppressing the flapping of the cold-rolled thin steel sheet 6. Even if the resonance type electromagnetic ultrasonic sensor is not installed at the position of the bridle roll 10 or 11, it may be installed at a mechanism that suppresses flapping of the cold-rolled thin steel sheet. The solid line shows the flow of signals or information, and the broken line shows the flow of control.

FIG. 8 shows the results obtained by measuring the rolling in-plane average value of the Rankford value (r value) of the cold-rolled thin steel sheet during online threading every 5 m. The results measured by the method of the present invention are shown by □, and the results obtained by cutting out this cold-rolled thin steel sheet with a tensile tester are shown by ◯. As can be seen from FIG. 8, the range of the Rankford value is small, but it corresponds to the value measured by the tensile tester.

[0038]

As described above, in the present invention, only the resonance type electromagnetic ultrasonic sensor is used to completely nondestructively and without polluting the cold rolled steel sheet, and the resonance frequency ratios K ₁ and K.
By using ₂ , it is possible to obtain the in-plane average value of Young's modulus or the in-plane average value of Rankford value by an approximate arithmetic expression. The in-plane average of the Young's modulus of the cold-rolled thin steel sheet or the in-plane average of the Rankford value can be easily and quickly measured off-line. Furthermore, because the sensor can be made compact and high-speed measurement is possible, it is possible to measure the in-plane average value of the Young's modulus of the cold-rolled thin steel sheet or the in-plane average value of the Rankford value even during online rolling, which is effective for online quality control ..

[Brief description of drawings]

FIG. 1 is a diagram showing propagation directions and vibration directions of ultrasonic waves of various modes related to the present invention.

FIG. 2 is a diagram showing a resonant electromagnetic ultrasonic sensor for generating and detecting a longitudinal ultrasonic wave and two kinds of transverse ultrasonic waves propagating in the thickness direction of a thin steel plate.

FIG. 3 is a diagram showing a relationship between changes in K ₃ and average values of Young's modulus in a plane.

FIG. 4 is an in-plane average value of Young's modulus and resonance frequency ratios K ₁ and K ₂ , which are approximately obtained from measured values of resonance frequency ratios K ₁ and K ₂ and sound velocity ratio K ₃ = 0.96 according to the present invention. And sound velocity ratio K
_The figure which compared the Young's modulus in-plane average value calculated | required from the measured value of ₃ .

FIG. 5 shows the relationship between the average value (E) of the Young's modulus in the rolled surface obtained by the method of the present invention and the average value (r) of the Rankford value obtained by the tensile tester in the rolled surface. Fig.

FIG. 6 shows the relationship between the average value (r) of the Rankford values obtained by the method of the present invention in the rolled surface and the average value (r) of the Rankford values obtained by the tensile tester in the rolled surface. FIG.

FIG. 7 is a diagram showing an outline of a measurement system for obtaining an in-plane average value of Young's modulus or an in-plane average value of Rankford values online.

FIG. 8 is a diagram showing a Rankford value (r value) measurement result of a cold-rolled thin steel sheet during online threading.

[Explanation of symbols]

 1 High-order computer 2 Measuring device computer 3 Transmitting amplifier 4 Resonance type electromagnetic ultrasonic sensor 5 Copying device 6 Cold rolled thin steel plate 7 Receiving amplifier 8 Gate 9 Frequency analyzer 10 Incoming bridle roll 11 Outgoing bridle roll

Claims (6)

[Claims] 1. A thickness resonance frequency of transverse ultrasonic waves propagating in the thickness direction while vibrating inside the cold rolled thin steel sheet in a direction parallel to the rolling direction and a thickness resonance frequency of longitudinal ultrasonic waves propagating in the thickness direction. And the thickness resonance frequency of transverse ultrasonic waves propagating in the thickness direction while vibrating in the direction perpendicular to the rolling direction inside the cold-rolled thin steel sheet and longitudinal ultrasonic waves propagating in the thickness direction. The value of the ratio to the thickness resonance frequency of the
A method for measuring the material properties of a cold-rolled thin steel sheet, characterized in that the Young's modulus and the Rankford value of the cold-rolled thin steel sheet are obtained based on the value of the seed ratio. 2. The process of measuring the ratio and value of the two kinds, and the sound velocity of SH0 plate wave propagating in the cold rolled thin steel sheet in a direction forming 45 ° with the rolling direction and a direction parallel to the rolling direction or The Young's modulus of the cold-rolled thin steel sheet was determined from the process of considering the ratio of the sound velocity of SH0 plate waves propagating in the direction perpendicular to the sound velocity as a constant value and the value of the three types of ratios and the known elastic modulus of the iron single crystal. And a step of approximately calculating an in-plane average value of the Rankford value. 3. An electromagnetic ultrasonic device including at least a resonant electromagnetic ultrasonic sensor is used to generate and detect the two types of transverse ultrasonic waves and the one type of longitudinal ultrasonic wave, and to detect the thickness resonant frequency. The material measuring method according to claim 1, wherein the value of the ratio is measured. 4. The electromagnetic ultrasonic device comprises a coil for passing a high-frequency current for inducing an eddy current in the cold-rolled thin steel sheet, a magnet for applying a predetermined magnetic field to the cold-rolled thin steel sheet, and the eddy current. And the magnetic field, the resonance type electromagnetic ultrasonic wave for detecting the two kinds of transverse ultrasonic waves and the one kind of longitudinal ultrasonic waves generated by the electromagnetic force generated in the vicinity of the surface of the cold-rolled steel sheet. By generating and detecting the transverse ultrasonic wave and the longitudinal ultrasonic wave while sweeping the frequency of the high-frequency current flowing through the coil, and recording the frequency when the detected ultrasonic wave reaches a maximum. The material measuring method according to claim 3, wherein the three types of thickness resonance frequencies are obtained. 5. An electromagnetic ultrasonic device and an arithmetic device for calculating Young's modulus and Rankford value of a cold-rolled thin steel sheet based on a value of a ratio of the thickness resonance frequency measured by the electromagnetic ultrasonic device. 4. The material measuring device for a cold-rolled thin steel sheet according to claim 3, further comprising: and a copying apparatus including a copying mechanism for making a gap between the resonance type electromagnetic ultrasonic sensor and the cold-rolled thin steel sheet constant. 6. A frequency analysis in which a high frequency current is output while sweeping the frequency because the electromagnetic ultrasonic device generates two kinds of transverse ultrasonic waves and one kind of longitudinal ultrasonic wave in the cold rolled steel sheet. An apparatus and a resonance type electromagnetic ultrasonic sensor for detecting the transverse ultrasonic waves and the longitudinal ultrasonic waves, and from the signals detected by the resonance electromagnetic ultrasonic sensor, a high frequency current output from the frequency analysis device 6. The material measuring device according to claim 5, wherein a signal having the same frequency component as that of is extracted by the frequency analyzing device to obtain the value of the ratio of the thickness resonance frequencies.