JPH021547A - Method for evaluating deep drawing property of metallic sheet - Google Patents

Abstract

PURPOSE:To execute the evaluation by an appropriate non-destructive measurement as an on-line-like evaluation by deriving a plastic strain ratio by propagating directly an ultrasonic wave to a metallic sheet. CONSTITUTION:A rolling direction propagation plate probe 11 sends/receives an ultrasonic plate wave which is propagated by a prescribed distance in the rolling direction of a sample. A rolling 45 deg. direction propagation plate wave probe 12 sends/receives the ultrasonic plate wave which is propagated by a prescribed distance in the direction inclined by 45 deg. against the rolling direction of the sample. A rolling orthogonal direction propagation plate wave probe 13 sends/receives the ultrasonic plate wave which is propagated by a prescribed distance in the direction orthogonal to the rolling direction of the sample. In this state, the quantity for evaluating a main crystal azimuth component of the sample by using a measured value of each propagation time is derived by a computing element 40. As a result, an in-plane mean value and an in-plane azimuth difference of a plastic strain ratio are derived. In such a way, the evaluation by an appropriate non-destructive measurement is executed as an on-line-like evaluation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for evaluating the deep drawability of a rolled metal sheet such as a low carbon cold rolled steel sheet.

[Prior art]

Cold-rolled steel sheets used for the exterior of products such as automobiles and home appliances are generally deep drawn by press forming, so the workability, especially the deep drawability, is important. It is evaluated based on the ratio of the strain in the width direction to the strain in the thickness direction, which is the so-called plastic strain ratio (also referred to as the Lankford value or r value).

As a method for determining the plastic strain ratio for evaluating deep drawability, for example, a direct method is used in which a tensile test is performed to directly determine the plastic strain ratio.

When using the direct method, a tensile test piece is taken from a steel plate, and a uniaxial tensile test is performed to give the tensile test piece an elongation of 15 to 20%, and the resulting strain in the plate width direction and plate thickness direction is measured. By actually measuring the plastic strain ratio (
r = i n(W/Wo)/l n(8.).

W, W. , t, to: the width and thickness of the test piece before and after stretching are directly determined. The plastic strain ratio actually used is the in-plane average value 7 given by the following formula:
will be adopted.

r=(ro・+2r4.・+r,.・)/4・
・・(1) However, ro・: plastic strain ratio by a tensile test piece taken along the rolling direction; :Plastic strain ratio of tensile test pieces taken in the direction perpendicular to the rolling direction.The lower the in-plane average value of the plastic strain ratio, the higher the value, the higher the deep drawability. The in-plane orientation difference Δr of the plastic strain ratio given by the following equation is an index of the ease with which edge cracks occur.

Δr = (ro, 2 r4s, + rq.,)/2 ・
(2) A resonance method is also used in which the plastic strain ratio is estimated from the Young's modulus obtained by causing a sample of a predetermined size to resonate. In the case of the resonance method, first, a plurality of samples of a predetermined size are prepared from a steel plate and divided into three directions: the rolling direction, a direction inclined by 45 degrees to the rolling direction, and a direction perpendicular to the rolling direction. These samples are then subjected to magnetic distortion using electromagnetic induction to cause them to resonate. Then, the resonant frequency of the resonating sample is determined by electromagnetic induction, and the Young's modulus of each sample is determined from the resonant frequency.

Then, the average Young's modulus (■) and its orientation difference AE given by the following equations (3) and (4) are determined.

1=(■., +2E4s, +E9゜,)/4...
(3) τE= (Eo, 2 Ens, +Eqo,) /
2...(4) However, πo: Average value of Young's modulus of samples taken along the rolling direction π45・: Average value of Young's modulus of samples taken at 45° with respect to the rolling direction ■.・: The average value E and AE of the Young's modulus of the samples taken in the direction perpendicular to the rolling direction are the in-plane orientation difference Δr below the in-plane average value of the plastic strain ratio
Since there is a certain correlation between the two, the in-plane average value of the plastic strain ratio 7° in-plane orientation difference Δr is determined based on this correlation.

Furthermore, an X-ray method is also used in which the plastic strain ratio is determined from the intensity of X-rays whose course is changed by a specific crystal orientation using XyA diffraction. When using the X-ray method, the steel plate is directly irradiated with X-rays without taking any test pieces or samples from the steel plate. These X-rays are diffracted by crystal planes specific to the sample, and by measuring the intensity of the X-rays whose course is changed due to the diffraction, the texture of the sample is estimated, and the plastic strain ratio is derived from this. Therefore, unlike the above-mentioned direct method, resonance method, etc., the X-ray method has the advantage that evaluation can be performed by non-destructive measurement.

Furthermore, there is a method using ultrasonic flaw detection as a non-destructive measurement evaluation method similar to the X-ray method.

Specifically, it is a method in which an ultrasonic plate wave is propagated in a predetermined direction of the steel plate as a sample, the propagation velocity in the steel is determined by a predetermined measuring means, and the result is used to derive, for example, the plastic strain ratio ( JP-A No. 57-66355).

[Problem to be solved by the invention]

However, in this method of evaluating deep drawability by determining the plastic strain ratio, for example, if the direct method is used, it takes a lot of time and effort to take a tensile test piece and actually measure the strain, and the resonance method requires a lot of time and effort. However, there are also problems such as an unavoidable decrease in work efficiency due to sample collection. Moreover, since all of the above-mentioned methods require destructive measurements in principle, it is difficult to say that they are suitable as online evaluation methods. On the other hand, when using the X-ray method, evaluation is possible through non-destructive measurement and is an appropriate online evaluation method, but the equipment used is quite large and costs increase, and the plastic strain ratio In order to maintain the measurement accuracy at a certain level, it is necessary to obtain the plastic strain ratio at intervals of about 10 seconds, which is a problem that remains unsatisfactory as an online evaluation method. Furthermore, in the case of using the ultrasonic flaw detection method, the plastic strain ratio in a predetermined direction is determined by propagating an ultrasonic plate wave in a predetermined direction of the copper plate. Therefore, as a method for arbitrarily evaluating deep drawability, As expected, there were some difficulties.

Therefore, as a practical method that enables online evaluation of deep drawability, the present inventors measured the propagation time of the longitudinal wave and two types of transverse waves of the ultrasonic plate wave propagating in the thickness direction of the steel plate. proposed a method of determining the velocity ratio of longitudinal waves and transverse waves from the measurement results and determining the plastic strain ratio from these velocity ratios (Japanese Patent Application No. 62-238183).

In this method, since the crystal orientation distribution of the steel sheet is taken into consideration, it is possible to evaluate the deep drawability as desired. However, this method is not without problems that need to be solved, and the thickness of the sample is, for example, 9.5 mm. There is a practical problem in that when the thickness is extremely thin, such as less than 5 nm, it becomes difficult to separate the bottom echo of ultrasonic waves.

The present invention has been made in view of the above circumstances, and unlike the conventional direct method, resonance method, etc., evaluation can be performed by appropriate non-destructive measurement as an online evaluation method, and it is also capable of evaluation using non-destructive measurement suitable for the conventional X-ray method. In comparison, the plastic strain ratio can be determined easily and quickly, and the plastic strain ratio can also be determined for plated metal thin plates, making it more practical than the conventional ultrasonic flaw detection method. Moreover, the purpose is to provide a deep drawability evaluation method that can be applied to a wide range of thin metal sheets.

[Means to solve the problem]

The method for evaluating deep drawability of a thin metal sheet according to the present invention includes applying ultrasonic plate waves of 30 modes to a rolled thin metal sheet in a rolling direction, in a direction inclined by 45 degrees to the rolling direction, and in a direction perpendicular to the rolling direction. propagate a certain distance in three directions,
By measuring each propagation time and using the measured values to derive a quantity for evaluating the main crystal orientation of the thin metal sheet, the in-plane average value of the plastic strain ratio and the in-plane orientation difference are calculated. is corrected based on the thickness information of the thin metal plate,
Furthermore, for the plated metal thin plate, the propagation time is corrected based on the plating thickness, and the in-plane average value of the plastic strain ratio and the in-plane orientation difference are calculated.

[Effect]

When compared with the conventional direct method, resonance method, etc., the method of the present invention allows the plastic strain ratio to be determined by directly propagating ultrasonic waves to a thin metal sheet without taking a test piece, sample, etc. from the thin metal sheet. Therefore, evaluation using non-destructive measurement is possible as an online evaluation method. In addition, when compared with the conventional X-ray method, the equipment used is simple, and the measurement accuracy can be maintained at a certain level even when determining the plastic strain ratio at short intervals, making it easy and quick. The plastic strain ratio can be determined. Furthermore, when compared to methods using conventional ultrasonic flaw detection, the plastic strain ratio is obtained by introducing the crystal orientation distribution function of the thin metal sheet, so deep drawability can be evaluated as an accurate and direct evaluation quantity. Not only is this possible, but the plastic strain ratio determined as described above is corrected using information on the thickness of the thin metal plate, so the influence of variations in the thickness can be suppressed. In addition, the present invention can also be applied to plated metal thin plates by correcting changes in propagation time due to changes in sound speed based on variations in plating thickness.

[Example 1] The present invention will be described below based on drawings showing examples thereof.

FIG. 1 is a block diagram of the main parts of the apparatus used to carry out the method of the present invention, and numeral 10 in the figure indicates a sensor section that transmits and receives ultrasonic plate waves in the S0 mode. Figure 2 is a graph showing the mode of ultrasonic plate waves, with [frequency x plate thickness] plotted on the horizontal axis and [phase velocity] plotted on the vertical axis. The S0 mode ultrasonic plate wave, which has a sufficiently low frequency relative to the plate thickness of the sample S (hereinafter simply referred to as sample S) and has little velocity dispersion, is in the area circled by a circle in the graph. As shown in FIGS. 3 and 4, the sensor section 10 is a rolling direction propagation plate wave probe disposed on the sample S to transmit and receive the ultrasonic plate waves that propagate a certain distance in the rolling direction of the sample S. 11 and a rolled 45° direction propagation plate wave probe placed on the sample S to transmit and receive ultrasonic plate waves that propagate a certain distance in a direction inclined at 45° with respect to the rolling direction of the sample S. 12, and a plate wave probe 13 that propagates in a direction perpendicular to rolling, which is placed on the sample S to transmit and receive ultrasonic plate waves that propagate a certain distance ■7 in a direction perpendicular to the rolling direction of the sample S. ing.

Specifically, as shown in FIG. 3, the rolling direction propagation plate wave probe 11 has a transmitter 11a that transmits and receives ultrasonic plate waves, and a receiver 11b that receives the ultrasonic plate waves, which are separated from each other by a certain distance. The structure is such that the transmitter 11a and the receiver 11b are connected by a fixed distance axis 11c so that the transmitter 11a and the receiver 11b are placed on the sample S at a distance of 1ζ. , also rolling 45°
The direction propagation plate wave probe 12 and the rolled orthogonal direction propagation plate wave probe 13 have the same structure as the rolling direction propagation plate wave probe 11, and each transmitter 12a, 13a and each receiver. 12b and 13b are arranged on the sample S. And these probes 11.12.13 are
As shown in FIG.
5°, and the probe 13 is arranged at 90°).

Incidentally, in order to avoid interference between the fixed distance axes of the respective probes 11, 12, and 13, it is preferable to make their heights different from each other.

Alternatively, other fixing methods may be used.

Further, as the probe, a transceiver that generates electromagnetic ultrasonic waves may be used.

Each probe 11, 12.13 is an ultrasonic flaw detector 21 equipped with a pulser and a receiver (for example, regarding the probe 11, a balsa 21a and a receiver 21b as shown in FIG. 3).
．． The ultrasonic flaw detectors 21, 22, and 23 are connected to propagation time measuring devices 31, 32, and 33, respectively. and propagation time measuring device 31.32
．． 33, the propagation time T0. required for the three types of ultrasonic plate waves to propagate a certain distance is determined from the ultrasonic waveforms individually obtained by the ultrasonic flaw detectors 21, 22, and 23. .

7456, T9°, are measured individually. The propagation times T0·, T45·, T, thus measured. Data regarding . is input to the computing unit 40. and arithmetic unit 40
is the expansion coefficient W4° of the crystal orientation distribution function of sample S using those data. , find W44°. And the expansion coefficient W4° obtained as described above. , W44° is manually input to the converter 50, and the converter 50 uses the data to convert the in-plane average value r of the plastic strain ratio and the in-plane orientation difference Δr. The result obtained by the converter 50 is displayed on the display 60.
is now displayed.

Next, the concept underlying the calculation performed by the arithmetic unit 40 and the conversion performed by the converter '50 will be explained.

First, considering the crystal orientation distribution of sample S, its crystal orientation distribution function F (ξ, ψ, φ) is expressed by the following equation.

...(5) However, ξ, ψ, φ: Euler angle Z indicating the relationship between the crystal axis and the axis fixed to the sample, Wlffin: expansion coefficient, and if the sample S is from a cubic crystal. If it is an orthorhombic system with orthotropy of
There is no dispersion of the sound velocity with respect to the plate thickness) frequency S. The speed of the ultrasonic plate wave mode is calculated using the following formula.

However, V3(θ): Speed ρ of 50-mode ultrasonic wave 1 repulsion
: Density μ, λ of sample A: Lamé constant C: Elastic constant θ: Angle between the propagation direction of the ultrasonic plate wave and the rolling direction, and... (8) To, T, S, T, +, - and the expansion coefficient W4°. and the in-plane average value of the plastic strain ratio show a certain correlation as shown in FIG.

Expansion coefficient W4゜O+W appearing in formulas (4) and (5)
440 is calculated by the calculation unit 40 (t/T, ·
Between the values of +2/Ta5- + 1/'T'qo,) and (1/T, -2/Tas・+t/Tq.・), for example, the following equations (8) and (9) As shown in the figure, there is a relationship of linear correspondence, and using this relationship, the expansion coefficient W40+1 + Wa4o can be easily calculated. Note that this calculation is performed by the calculator 40.

Number W4゜. The in-plane average value 7 of the plastic strain ratio is converted from . Physically, this W4゜0 corresponds to the volume fraction of the main orientation components of the texture, and in cold rolled steel sheets in which H1li-set Mi texture is dominant (corresponds to the volume fraction of the 1111 plane, In other words, it corresponds to the r value.

In addition, the in-plane orientation difference Δ between the expansion coefficient W44° and the plastic strain ratio
For example, as shown in FIG. 6, r shows a certain correlation,
Based on this correlation, the in-plane orientation difference Δr of the plastic strain ratio is converted from the expansion coefficient W A 40.

Note that this conversion is performed by a converter 50.

Also, the measured value T. , T41. T9. Using longer propagation distances, V s (0)”, V s (45)”, V
s (90)'' and using these values and equation (4), the following equation is obtained: < Waoo+Waa.

You may also ask for

...θ0) Jb Thus, when determining the in-plane average value of the plastic strain ratio and the in-plane orientation difference Δr of the sample S, that is, the thin metal sheet, and evaluating the deep drawability of the thin metal sheet, a test piece is extracted from the thin metal sheet. Since the plastic strain ratio is determined by directly propagating ultrasonic waves without taking samples, etc. (in contrast to metal thin sheets), it is possible to evaluate by appropriate non-destructive measurement as an online evaluation method. In addition, unlike an X-ray device, the device used is a simple ultrasonic fatigue device, and even if the plastic strain ratio is measured at short intervals (1 second/time in a row), the measurement accuracy remains at a certain level. The plastic strain ratio can be determined simply and quickly.Furthermore, since the plastic strain ratio is determined by introducing the crystal orientation distribution relationship of the thin metal sheet, it is possible to evaluate any deep drawability. In addition, S with low velocity dispersion generated at a sufficiently low frequency relative to the thickness of the thin metal plate
0Mo...(II) Since a one-wave ultrasonic plate wave is used, there is no problem with the bottom echo of the ultrasonic waves.

Next, measurement results obtained using the method of Example 1 will be illustrated. Figure 7 is a graph showing the distribution of measured values of the in-plane average value 7, with the horizontal axis representing the distance from the top of the sample and the vertical axis representing the in-plane average value 7 of the plastic strain ratio. It can be seen that online measurement of the plastic strain ratio can be smoothly performed using the method of the present invention.

In carrying out the method of Example 1, the probes 11, 12, and 13, in which a pair of transceivers are connected by a fixed distance axis, are used to position the transceiver with respect to the sample and with respect to each other. Instead, as shown in FIG. 8, all the transceivers 11a are placed at appropriate positions between a pair of copying rollers 14b, 14b provided on a holder 14a.

11b, 12a, 12b, 13a, and 13b are used to move the sample to the rollers 14b,
14b, transmitting/receiving elements 11a, llb, 12
By sliding on the a+ 12b, 13a, and 13b, the positioning operation becomes easy.

Note that as the transmitter/receiver used here, one that generates electromagnetic ultrasonic waves can be used. FIG. 9 is an explanatory diagram showing the structure of the transmitter/receiver. This transmitter/receiver has a structure in which a probe coil 71 is overlapped with a magnet 70. When a pulse current is applied to the probe coil 71 from a pulser 72, A dielectric current is induced on the surface of the thin plate, and Lorentz force is generated by the interaction between this dielectric current and the magnetic field generated by the magnet.

The direction of the probe coil 71 changes by % of the wavelength of the plate wave generated by the flowing current, and the Lorentz force is generated by changing the direction of the force by 180' every half wavelength. The force generates a plate wave of a predetermined wavelength. After the generated plate wave propagates through the thin plate, it is converted into an electrical signal by the receiving side probe coil 71 using the same principle, and then amplified by the preamplifier 73 and passed through the filter 7.
After the signal is shaped into a predetermined shape in step 4 and further amplified in main amplifier 75, its propagation time is measured by time measuring device 31.

[Embodiment 2] FIG. 10 is a block diagram showing the configuration of main parts of an apparatus used in another embodiment of the present invention. Data D regarding Fi thickness information of steel plate S and flaw detection frequency information output device 3
5, data f regarding flaw detection frequency information is also input. The other configurations are substantially the same as those of the embodiment shown in FIGS. 1 to 4, and corresponding parts are given the same numbers and explanations will be omitted.

In such an embodiment, the equation (12) below corresponds to equation (6) in the explanation of the embodiment shown in FIGS. 1 to 4. That is, assuming that the sample S is an orthorhombic system consisting of cubic crystals and has orthotropic anisotropy, the speed ■(0) at which the ultrasonic plate wave in the S0 mode propagates in the direction of the angle θ (angle with respect to the rolling direction) is: It can be calculated using the following formula that takes velocity dispersion into account.

(Leaving space below) μ: Lame constant: Density of sample S: Detection frequency: Half of the plate thickness of sample S However, 16λ (λ0μ) 8゛3+ +2#)・4μ (λ0μ) λ+2μ C: Jlo 4J2π2 Expansion coefficient W4° according to equation (13) and equation 04. ,W
Since the calculation of 44° is performed as described above (using the information on the thickness of the sample S), the influence of variations in the thickness can be suppressed.

There is a certain correlation between the expansion coefficient W4°O and the in-plane average value of the plastic strain ratio, and the expansion coefficient W4° is based on this correlation. The in-plane average value of the plastic strain ratio can be converted from force 1. In addition, the aforementioned self-expansion coefficient C: Elastic constant W400 + W42G + W440: Expansion coefficient when the crystal orientation distribution function of sample S is expanded into a sphere By the way, typical crystal orientations that occur in sample S, that is, cold-rolled steel sheets, and affect deep drawability. As (110
) <110>, (till <112>, (11
0) <OOb.

(100) <011> , (100) <OOb
etc., but if the probability of existence of these crystal orientations is 1, the expansion coefficient W L a * can be calculated. Conversely, if the expansion coefficient W, , 1 is known, the in-plane average value of the plastic strain ratio and the value of the in-plane orientation difference Δr can be predicted.

Specifically, the expansion coefficient W4° is obtained using the following side equation and circle equation derived from equation 09. , W44° can be obtained.

w,,, = (Vz (0°) + 2 V"(45') +
V"(90°)4■.") /4AD
...03) W'aao = (V'' (0°)
-2V" (45°) + V2 (90°))/4CD...
04) W44° and the in-plane orientation difference Δr of the plastic strain ratio show a certain correlation, and based on this correlation, the expansion coefficient W44° is determined. The in-plane orientation difference of the plastic strain ratio can be calculated from

Thus, in Example 2, as in Example 1, sample S,
That is, the in-plane average value r and the in-plane orientation difference Δr of the plastic strain ratio of the thin metal sheet are determined, and the plastic strain ratio is determined by directly propagating ultrasonic waves to the thin metal sheet without taking a test piece, sample, etc. from the thin metal sheet. can be obtained, and evaluation using appropriate non-destructive measurement is possible as an online evaluation method. In addition, unlike an X-ray device or the like, the device used is a simple ultrasonic device, and even if the plastic strain ratio is determined at short intervals (for example, 1 second/time), the measurement accuracy can be maintained at a constant level. The plastic strain ratio can be determined simply and quickly. Furthermore, since the warping strain ratio is determined by taking into account the crystal orientation of the thin metal sheet, it is possible to evaluate the deep drawability as desired, and when calculating the plastic strain ratio, corrections are made using the sheet thickness information of the thin metal sheet. Therefore, the reliability of deep drawability evaluation based on the calculation is improved.

Next, the effects of Example 2 will be explained based on specific data.

FIG. 11 shows the expansion coefficient W4° determined by changing the thickness of the sample S and ignoring the velocity dispersion of the plate waves, with the ultrasonic frequency kept constant at IMllz. The deviation (percentage) from the true value of
The thickness of the sample S is shown on the horizontal axis, and the deviation from the true value is shown on the vertical axis. From the figure, the error is within 10% up to a plate thickness of about 0.5 mm, but when the plate thickness is 0.5 m
It can be seen that when the value exceeds m, the error becomes unacceptable.

However, in the case of the method of Example 2, the expansion coefficient W,
, ), ) is corrected using the information regarding the plate thickness, so the calculation accuracy is as shown in Figures 12 and 13.
It improves as shown in the figure. That is, Fig. 12 shows the correlation between the in-plane average value r of the plastic strain ratio obtained by the tensile test and the expansion coefficient W, )6 calculated in carrying out the method of Example 2, and Fig. 13 shows the correlation between the in-plane average value r of the plastic strain ratio obtained by the tensile test and the expansion coefficient The correlation between the in-plane orientation difference Δr of the plastic strain ratio obtained by the test and the expansion coefficient W440 calculated in implementing the method of Example 2 is shown, and an excellent correspondence relationship is observed between the two. Therefore, the expansion coefficient W4°.

, W44° to calculate the plastic strain ratio, the calculation accuracy is improved.

[Example 3] In this example, a plated steel plate in which the surface of a drawn steel plate, which is a base material, has been plated was evaluated for deep drawability. According to the experiments and research conducted by the present inventors, the plating thickness in a plated steel sheet and the sound speed of the s0 mode that propagates this are determined by the plating J
There is a correspondence relationship in which the sound velocity changes depending on the V, but there is a relationship in which the sound velocity distribution within the plate surface does not change. Therefore, by correcting the change in the sound velocity with respect to the plating thickness, it is possible to determine the propagation velocity of the plate wave in the steel plate itself, which is the underlying base material, and using this sound velocity value, the depth It becomes possible to evaluate the drawability.

Figure 14 (a), (b), and (c) show the plating thickness (200
p m.

50 μm, 10 μm) and the speed of sound, with the horizontal axis representing the plate wave propagation direction and the vertical axis representing the sound speed (m/sec). The mark plotted in the graph indicates the sound velocity in an unplated cold-rolled steel sheet, and the O mark plotted in the graph indicates the sound velocity in a plated steel sheet.

As is clear from this graph, although the sound speed changes depending on the plating thickness, it can be seen that the sound speed distribution, that is, the amount of sound speed change in the plate wave propagation direction, does not change.

The inventors set the base material thickness to 2d and the plating thickness to Δd.
) A correction formula for the speed of sound (■) was calculated.

However, μFl) + λFa Two elastic constants of steel μm, λ1:
The elastic constant ρF of the plated material, the density ρi of the di-plated material, and the density of the plated material Figure 15 shows the plating thickness Δd (μm) on the horizontal axis, and the velocity of sound in the unplated cold-rolled steel plate versus the velocity of sound in the unplated cold-rolled steel plate on the vertical axis. It is shown by taking the ratio of the speed of sound. In the graph, the O symbol plotted is the calculated value obtained using formula 09, and the . symbol plotted is the measured value.

As is clear from this graph, it was confirmed that the calculated values substantially matched the measured values.

FIG. 16 is a block diagram showing the configuration of the main parts of the apparatus used in the third embodiment. In this embodiment, for the arithmetic unit 40,
In addition to the propagation time which is the output of each propagation time measuring device 31, 32, 33, plate thickness information D from the plate thickness information output device 34, flaw detection frequency information f from the flaw detection frequency information output device 35, and plating thickness information output device 36, plating thickness information Δd is input.

The rest of the structure is substantially the same as the device shown in FIGS. 1-4 and 10, and corresponding parts are given the same numbers.

The contents of the calculation in the calculation unit 40 are as follows.

Propagation times To, +Tas, +Tq input from each propagation time measuring device 3L32, 33. , the plate thickness 2d (d=z plate j ¥) inputted from the base material plate thickness information output device 34, and the plating thickness Δd( inputted from the plating thickness information output device 36).
S in an unplated steel plate based on the thickness of one side) and the transmission/reception time path i9L.

Sound speed of mode ultrasound (electromagnetic ultrasound)■.・, ■4.・V
The following 06), 07), which corresponds to the 09 type with 9G.
08) Calculate according to the formula.

(Left below) Next, use the converter 50 to calculate ■.・, ■4.・, Expansion coefficient W4° when the crystal orientation distribution function of sample S is expanded into a sphere using V2O・. , W44° as below Q9), 12[11
Find it according to the formula.

W, 6゜= (vo,"+ 2 V4."+ Vq
o, "4 vo, zl '...Q9) As mentioned above, there is a linear correspondence between W4゜. and lower, W 4 d. and Δr, and the value of W4゜.1w44゜The value of 7 and Δr corresponding to is output to the display 6o and displayed.

In addition, instead of Q9) and 1211), Rini Example 1 (7)
(to), (Equation 10 may be used.

Figure 17 shows W4°. and r4fL, and the 18th
Figure C is a graph showing the relationship between W44° and Δr.

In Figure 17, the horizontal axis shows the lower price, and the vertical axis shows W4°. In FIG. 18, the horizontal axis represents the r value, and the vertical axis represents W44°.

As is clear from this graph, there is a linear correspondence relationship.

Therefore, as in Examples 1 and 2, by directly propagating ultrasonic waves to the plated ζ plate A-D, the plastic strain ratio can be determined, and the deep drawability can be evaluated online.

〔effect〕

As detailed above, according to the method of the present invention, when evaluating the deep drawability of a thin metal sheet, the plastic strain ratio can be easily and quickly determined by non-destructive measurement, and the problem of ultrasonic bottom echoes can be solved. By avoiding this, the plastic strain ratio can be effectively and arbitrarily determined. Furthermore, by using a transmitter/receiver that uses electromagnetic ultrasonic waves as its generation principle, there is no need to use a couplant between the thin plate and the transmitter/receiver, which facilitates online operation and improves time measurement accuracy. In addition, since the sound velocity is corrected according to the thickness of the thin metal sheet to be evaluated, the accuracy of deep drawability evaluation can be improved. Furthermore, the present invention has excellent effects such as being able to accurately evaluate the deep drawability of plated metal thin plates and the like, and having a wide range of applications.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of the main parts of the device used to carry out the method of Example 1, Fig. 2 is a graph showing each mode of the ultrasonic plate wave, and Fig. 3 is a block diagram showing the configuration of the main parts of the device used to carry out the method of Example 1. A vertical cross-sectional view showing the sonic flaw detector and the sample, Fig. 4 is a plan view showing the relationship between each transmitter/receiver of the plate wave probe and the sample, and Fig. 5 shows the inner surface average value 7 of the plastic strain ratio and the crystal orientation distribution. Expansion coefficient W4° of function. 6 is a graph showing the correlation between the in-plane orientation difference Δr of the plastic strain ratio and the expansion coefficient W44° of the crystal orientation distribution function. FIG. A graph illustrating the measurement results, FIG. 8 is a perspective view showing another aspect of the probe in the device used to carry out the method of Example 1, and FIG. 9 is the structure of the transceiver that generates electromagnetic ultrasound. FIG. 10 is a block diagram showing the configuration of the main parts of the device used in Example 2 of the present invention, and FIG. 11 shows the expansion coefficient W4° obtained while ignoring the velocity dispersion of the plate wave. 12 and 13 are graphs showing the deviation from the true value of W4° corresponding to the plate thickness. , a graph showing the comparison results between W44° and data obtained by a tensile test, FIG. 14 (a). (b) and (c) are graphs showing the relationship between plating thickness and plate wave propagation velocity, Fig. 15 is a graph showing the relationship between plating thickness and sound speed ratio of cold rolled steel sheet and plated steel sheet, and Fig. 16 The figure is a block diagram showing the configuration of the main parts of the apparatus used in the third embodiment of the present invention, and FIGS. 17 and 19 show the expansion coefficient W4° calculated in carrying out the method of the present invention. . It is a graph showing a comparison result between W44° and data obtained by a tensile test. 10...Sensor part 11...Rolling direction propagation plate wave probe 12...Rolling 45° direction propagation plate wave probe 13...
Rolling orthogonal direction propagation plate wave probe 21.22.23...Ultrasonic flaw detector 31.32.33...Propagation time measuring device 40...Calculator 50...Converter 60...Display Applicant S: Cold-rolled steel sheet (thin metal sheet) as a sample Patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Kawa
Noboru No 1.0 2.0 Plate thickness (mm) ++ Figure T by tensile test Figure 1.0 1.5 Figure 7 Figure tensile test △T1 straight B Figure

Claims (1)

[Claims] 1. S_ with sufficiently low velocity dispersion generated in a rolled thin metal plate at a sufficiently low frequency relative to the plate thickness.
0 mode ultrasonic plate waves were propagated a certain distance in three directions: the rolling direction, a direction inclined at 45° to the rolling direction, and a direction perpendicular to the rolling direction, and the propagation time of each was measured. deep drawability of a thin metal sheet, characterized in that the in-plane average value of the plastic strain ratio and the in-plane orientation difference are determined by deriving a quantity for evaluating the main crystal orientation component of the metal thin sheet using the measured value. Evaluation method. 2. S_0 mode ultrasonic plate waves are applied to the rolled metal thin plate at a certain distance in three directions: the rolling direction, a direction inclined at 45° to the rolling direction, and a direction perpendicular to the rolling direction. The in-plane average value of the plastic strain ratio and the in-plane orientation difference are calculated by propagating the plastic strain and measuring each propagation time, and using the measured values to derive a quantity for evaluating the main crystal orientation component of the metal thin plate. A method for evaluating deep drawability of a thin metal sheet, characterized in that during the calculation, correction is performed using sheet thickness information of the thin metal sheet. 3. S_0 mode ultrasonic plate waves are applied to the plated rolled metal sheet in the rolling direction, in a direction inclined by 45° to the rolling direction, and in a direction perpendicular to the rolling direction.
To propagate a certain distance in a direction, measure each propagation time, correct this propagation time based on the plating thickness, and use the correction value to derive a quantity for evaluating the main crystal orientation component of a thin metal plate. A method for evaluating deep drawability of a thin metal sheet, characterized by calculating an in-plane average value of a plastic strain ratio and an in-plane orientation difference.