JPH0679019B2 - Deep drawability evaluation device for thin metal sheets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an apparatus for non-destructively evaluating on-line the deep drawability of various metal thin plates required to have workability.

[Prior art]

Since cold-rolled steel sheets used for the exterior of products such as automobiles and home appliances are generally deep-drawn by press forming, their workability, especially deep-drawability, is emphasized.
The deep drawability is evaluated by a so-called plastic strain ratio (also referred to as Rankford value or r value), which is a ratio of strain in the plate width direction and strain in the plate thickness direction generated when the steel plate is stretched.

Then, in order to obtain the plastic strain ratio in order to evaluate the deep drawability, the following method is used. For example, a direct method is used in which a tensile test is performed to directly determine the plastic strain ratio. In the case of this direct method, a tensile test piece is taken from the steel plate, and a uniaxial tensile test that gives an elongation of 15 to 20% to the tensile test piece is performed. By measuring the strain and the plastic strain ratio (r = ln (W / W ₀ ) ln (t / t ₀ ), W, W ₀ , t,
t ₀ : Directly determine the width and thickness of the test piece before and after stretching.

The in-plane average value given by the following equation is adopted as the plastic strain ratio actually used.

= (R _{0 °} + 2r _{45 °} + r _{90 °} / 4) (1) where r _{0 °} : plastic strain ratio due to a tensile test piece taken along the rolling direction r _{45 °} : _{45 ° to the} rolling direction Plastic strain ratio r _{90 °} by the tensile test piece sampled: Plastic strain ratio by the tensile test piece sampled _{90 ° to the} rolling direction The in-plane average value of the plastic strain ratio is that the deep drawability is large. Although it becomes higher and becomes an index for evaluating the deep drawability, the in-plane orientation difference Δr of the plastic strain ratio given by the following equation becomes an index of the likelihood of ear cracking.

Δr = (r _{0 °} -2r _{45 °} + r _{90 °} / 2 ... (2) Also, a resonance method is used in which the plastic strain ratio is estimated from the Young's modulus obtained by resonating a sample of a predetermined size. In the case of the method, first of all, a plurality of samples are sampled from the steel plate in three directions: a rolling direction, a direction inclined by 45 ° to the rolling direction, and a direction orthogonal to the rolling direction. Then, magnetic resonance is applied to the sample by electromagnetic induction to cause the sample to resonate, and the resonant frequency of the resonating sample is determined by electromagnetic induction, and the sang rate of each sample is determined from the resonant frequency. The average Young's modulus and its azimuth difference ▲ ▼ are calculated by the formula and the formula (4).

However, Average Young's modulus of samples taken along the rolling direction Average Young's modulus of samples taken at 45 ° to the rolling direction Average value of Young's modulus of the sample taken in the direction orthogonal to the rolling direction. The value thus obtained, ▲ ▼ is the in-plane average value of the plastic strain ratio, and there is a certain correlation with the in-plane orientation difference Δr. Therefore, the in-plane average of the plastic strain ratio and the in-plane azimuth difference Δr are obtained based on this correlation.

Further, an X-ray method is also used in which the plastic strain ratio is obtained from the intensity of X-rays that are diverted by a specific crystal orientation by X-ray diffraction. In the case of this X-ray method, a test piece, a sample, etc. are not collected from a steel plate as a sample, but the steel plate is directly irradiated with X-rays. This X-ray is diffracted on a specific crystal plane of the steel sheet, but the texture of the sample is estimated by measuring the intensity of the X-ray that is diverted due to the diffraction, and the plastic strain ratio is derived from it. The X-ray method has an advantage that it can be evaluated by nondestructive measurement unlike the above-mentioned direct method, resonance method, and the like.

Further, as with the X-ray method, there is a method using an ultrasonic method as a method that can be evaluated by nondestructive measurement. Specifically, there is a method in which an ultrasonic plate wave is propagated in a predetermined direction of the steel sheet, the propagation velocity in the steel is obtained by a predetermined measuring means, and the result is used to derive the material properties of the steel sheet, for example, the plastic strain ratio ( JP-A-57-66355).

[Problems to be Solved by the Invention]

The conventional method for evaluating the deep drawability by obtaining the plastic strain ratio has the following problems. That is, when the direct method is used, it takes a lot of time and labor to collect the tensile test piece and measure the strain, and also when the resonance method is used, the work efficiency is inevitably lowered due to the sample collection. Moreover, since all of the above methods require destructive measurement in principle, it is difficult to say that they are suitable as online evaluation methods.

On the other hand, in the case of the X-ray method, non-destructive measurement can be performed and an appropriate online evaluation method can be obtained, but the apparatus used is considerably large and the cost is high, and the plastic strain ratio In order to maintain the measurement accuracy at a constant level, it is necessary to obtain the plastic strain ratio at intervals of about 10 seconds / time, and there is a problem that the online evaluation method still remains dissatisfied. Further, in the case of the method using the ultrasonic method, by propagating an ultrasonic plate wave of an arbitrary mode in an arbitrary direction of the steel sheet, the plastic strain ratio in the arbitrary direction is obtained, but as a method, In many cases, it was not applicable and was not applicable, and there was still a problem as a method for evaluating deep drawability.

Therefore, the present inventors have proposed a practical method capable of online evaluation and deep drawability evaluation, including longitudinal waves of ultrasonic plate waves propagating in the plate thickness direction of a steel plate as a sample and 2
We have already proposed a method of measuring the propagation time of each type of transverse wave, obtaining the velocity ratio between the longitudinal wave and the transverse wave from the measurement results, and further obtaining the plastic strain ratio from the correlation between the velocity ratio and the plastic strain ratio ( Japanese Patent Application No. 62-238183).

However, the method proposed by the present inventors as described above has the following problems.

That is, when performing such online, a measuring device that does not require a contact medium, such as an electromagnetic ultrasonic measuring device, is used.
In such a measuring instrument, when the distance between the thin metal plate and the probe fluctuates due to vibration during measurement, that is, lift-off fluctuation occurs, the impedance of the coil in the probe changes and the circuit constant of the entire measuring circuit system also fluctuates. In addition, the propagation speed of the ultrasonic wave changes due to the temperature change of the sample, which causes an error in the ultrasonic wave propagation time, and a time measurement error of about 10 ns occurs due to the change over time of the probe itself, so-called drift. . For example, if the time measurement value changes by 20 ns, the in-plane average value of the plastic strain ratio becomes
0.1 changes.

FIG. 8 is a graph showing a gap between the sample and the sensor unit, a time measurement value, and an influence of impedance. The horizontal axis represents the gap, and the vertical axis represents the time measurement value ratio (when there is a gap, respectively). Time measurement value / time measurement value when the gap is zero) and impedance ratio are shown.

In the graph, ● indicates the time measurement value ratio, and ○ indicates the impedance ratio (impedance when there is a gap / impedance when the gap is zero).

As is clear from this graph, when the gap changes,
It can be seen that the time measurement value ratio and impedance ratio change significantly.

FIG. 9 is a graph showing the relationship between the temperature of the sample and the plate wave propagation velocity, where the horizontal axis represents the sample temperature and the vertical axis represents the rate of change of the plate wave propagation velocity.

As is clear from this graph, it is understood that the rate of change of the plate wave propagation velocity changes as the sample temperature changes. By the way, it was confirmed that the in-plane mean value of the plastic strain ratio changes by 0.1 when the temperature of the sample changes by 30 ℃.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a deep drawing property evaluation apparatus for a thin metal plate that can more accurately perform online evaluation and appropriate nondestructive measurement.

[Means for Solving the Problems]

The deep drawability evaluation apparatus for a thin metal sheet according to the present invention provides an ultrasonic plate in a rolled thin metal sheet in three directions: a direction parallel to the rolling direction and a direction intersecting the rolling direction at 45 ° and 90 °, respectively. Deep drawability evaluation device comprising a sensor unit for propagating a wave and measuring a time for propagating a constant distance, and a unit for obtaining an in-plane average value of a plastic strain ratio and an in-plane misorientation based on these measured values In, the means for measuring the impedance change of the sensor part due to the variation in the separation dimension between the metal thin plate and the sensor part facing it, the means for measuring the surface temperature of the metal thin plate, and the impedance change obtained by these measuring means. And means for correcting the propagation time of the ultrasonic plate wave based on the temperature change, and means for measuring and correcting the drift of the measuring instrument.

[Action]

In the apparatus of the present invention, this makes it possible to eliminate errors due to sensor lift-off fluctuations and sample temperature fluctuations.

〔Example〕

The present invention will be specifically described below with reference to the drawings showing an embodiment thereof.

FIG. 1 is a schematic side view of a deep drawing property evaluation device according to the present invention (hereinafter referred to as an invented device) applied to a plate making line, in which 1 is a deep drawing evaluation device and A is a strip or the like. A sample is shown.

After the sample A is obtained through the looper, it is conveyed to the next step. On the way, the deep drawing property evaluation device 1 for a thin metal plate, which is the device of the present invention, is arranged, and both sides of the device are suitable for the sample A. Pinch rolls R ₁ and R ₂ that apply tension are arranged.

In the apparatus of the present invention, a deep drawing evaluation apparatus 1 for a thin metal plate comprises a sensor section 2 and an evaluation apparatus main body 3, and the sensor section 2 is provided with an infrared radiation thermometer 4 for measuring the strip temperature.

FIG. 2 is a schematic plan view of the sensor unit, and the sensor unit 2
As shown in FIG. 2, a rolling direction propagating wave probe 11 disposed on the sample A for transmitting and receiving the ultrasonic plate wave propagating in the rolling direction of the sample A by a constant distance L, and the sample A A rolling 45 ° direction propagating plate wave probe 12 arranged on the sample A for transmitting and receiving the ultrasonic plate wave propagating a fixed distance L in a direction inclined by 45 ° with respect to the rolling direction of A rolling crosswise propagation plate wave probe 13 arranged on the sample A for transmitting and receiving the ultrasonic plate wave propagating a predetermined distance L in a direction orthogonal to the rolling direction of the sample A. There is.

The rolling direction propagating wave probes 11, 12, and 13 have substantially the same structure, and the rolling direction propagating wave probe 11 has a third structure.
As shown in the figure.

FIG. 3 is a schematic cross-sectional view of the rolling direction propagating wave probe 11, in which the transmitter 11a that transmits and receives the ultrasonic plate wave and the receiver 11b that receives the ultrasonic wave are separated from each other by a constant distance L. Therefore, the transmitter 11a and the receiver 11b are arranged so as to be opposed to the sample A by the distance fixed shaft 11c. Further, the rolling 45 ° propagating plate wave probe 12 and the rolling orthogonal propagating plate wave probe 12
13 also has a structure similar to that of the rolling direction propagating wave probe 11 described above, so that the transmitters 12a, 13a and the receivers 12b, 13b can be arranged so as to face the sample A. There is.
And these probes 11, 12, and 13 are, as shown in FIG.
The angle with respect to the rolling direction on the sample A is a predetermined angle (0 ° for the probe 11, 45 ° for the probe 12, 90 ° for the probe 13)
It is arranged so that. In addition, in order to avoid mutual interference of the fixed distance axes of the probes 11, 12, and 13, it is preferable to make the heights different from each other. Alternatively, the distance may be fixed by using another means.

FIG. 4 is a block diagram of the device of the present invention.
The transmitters 11a, 12a, and 13a in 11, 12, and 13 are respectively pulsars 21,
22 and 23, and the receivers 11b, 12b, 13b are respectively preamplifiers 3
It is connected to 1,32,33. Each pulsar 21, 22, 23 is connected to the trigger circuit 6 with the switch 5 interposed, and the trigger signal generated from the trigger circuit 8 is sequentially input to the pulsar 21, 22, 23 via the switch 5. Then, a signal is output from the transmitters 11a, 12a, 13a so as to oscillate ultrasonic waves on the surface of the sample A.

The preamplifiers 31, 32, 33 are connected to the amplifier 41 with the switch 9 interposed therebetween. The switching device 9 is connected to the standard time signal generator 8, the switching device 9 is operated based on the standard time signal from the standard time signal generator 8, and each preamplifier 31, 32,
The signal 33 is selectively output to the amplifier 41. The signal amplified by the amplifier 41 is output to the time measuring unit 43 through the filter 42.

The time measuring unit 43 includes preamplifiers 31, 32, 33 that have passed through the filter 42.
The signal from the signal processing unit is calculated by calculating the propagation time required for the ultrasonic plate wave to propagate the fixed distance L.
It outputs to 45. The signal processing unit 44 includes the propagation time of the ultrasonic plate wave input from the time measuring unit 43, the temperature of the sample A input from the impedance infrared thermometer 4 input from the impedance measuring instruments 51, 52 and 53, and the standard time signal. The processing described later is performed based on the standard time signal input from the generator 8, the sample thickness information and the ultrasonic plate wave frequency information that are separately input.

The impedance measuring devices 51, 52, 53 are respectively connected to the rolling direction propagating plate wave probe 11, the rolling 45 ° direction propagating plate wave probe 12, and the rolling orthogonal direction propagating plate wave probe 13, and The switch 7 connected to the trigger circuit 6 is connected to the signal processing unit 45 via the switch 7, and the switch 7 operates according to the trigger signal from the trigger circuit 6, and each impedance measuring device 51, 52, 53.
Of the rolling direction propagating plate wave probe 11, the rolling direction propagating plate wave probe 12, and the rolling orthogonal propagating plate wave probe 13 are sequentially synchronized with the signal processing unit 44. It is designed to be output to.

For example, pulsar 21, rolling direction propagating plate wave probe 11, preamplifier
The signal obtained through the 31 path is the switch 9, the amplifier 41, and the filter 4.
2, the signal from the impedance measuring device 51 of the rolling direction propagating plate wave probe 11 passes through the switch 7 which is synchronized with the switching unit 5 when input to the signal processing unit 44 via the time measuring unit 43. Input to 44.

FIG. 5 is a flow chart showing the main signal processing steps performed in the signal processing unit 44. When the measurement value of the ultrasonic plate wave propagation time is input from the time measuring unit 43 (step
S1), it is determined whether or not a predetermined time has elapsed after the start of measurement (step S2), and if the time has elapsed, time calibration is performed (step S3).

That is, the signal processing unit receives the reference time signal from the standard time signal generator 8 every predetermined time, for example, every time when a drift fluctuation may occur in the measuring equipment which is empirically obtained in advance.
44, and based on this, the signal processor from the switch 9
Calibrate the time until it is input to 44. If the predetermined time has not elapsed, impedance correction is performed (step S4). That is, the signal processing unit 44 calculates the lift-off fluctuation amount that causes the impedance fluctuation detected by the impedance measuring device 51, and performs the lift-off correction corresponding to this fluctuation amount.

Similarly, the time measurement values calculated based on the respective measurement signals of the rolling 45 ° direction propagation plate wave probe 12 and the rolling orthogonal direction plate wave probe 13 are also detected by the impedance measuring devices 52, 53. Based on the calculated lift-off fluctuation amount, correction is performed.

Next, sample temperature correction is performed for each propagation time in which the error used for such lift-off fluctuation amount is corrected (step
S5). That is, an error due to a change in plate wave propagation time caused by a change in ultrasonic plate wave propagation velocity due to a change in sample temperature obtained by the infrared radiation thermometer 4 is corrected.

The signal processor 44 is the propagation time T _{0 °} of the plate wave after as mentioned above the correction, T _{45 °,} first using a T _{90 °} of data (step S6) (1 / T _{0 °} + 2T _{45 °} + 1 / T _{90 °} ) and (1 / T _{0 °} -2T
_{45 °} + 1 / T _{90 °} ) is calculated, and the expansion coefficients W ₄₀₀ and W ₄₄₀ of the crystal orientation distribution function of the sample A are obtained using the calculation result (step S7). Then, the in-plane average value of the plastic strain ratio and the in-plane azimuth difference Δr are obtained using the data on the expansion coefficients W ₄₀₀ and W ₄₄₀ obtained as described above (step S8), and the results are displayed on the display unit 45 ( In step S9), it is determined whether or not the end of the sample A has been reached (step S10), and if it has not reached the end, the process returns to step S1 and the above-described process is repeated.

Next, the content of the calculation performed by the signal processing unit 44 will be specifically described.

First, regarding the crystal orientation distribution of the sample A, the crystal orientation distribution function F (ξ, ψ, φ) is represented by the following equation (5).

However, ξ, ψ, φ: Euler angle indicating the relationship between the crystal axis and the axis fixed to the sample Z _L mn: Expansion function W _L mn: Expansion coefficient And sample A is an orthotropic anisotropic crystal composed of cubic crystals. Assuming that the orthorhombic system has properties, the velocity of the S ₀ -mode ultrasonic plate wave at a frequency that is sufficiently lower than the plate thickness of sample A (there is no dispersiveness of sound velocity with respect to the plate thickness) Calculated in 6).

However, V _S (θ): Velocity of ultrasonic plate wave in S ₀ mode ρ: Density μ of sample A, λ: Lame constant C: Elastic constant θ: Ultrasonic plate wave propagation direction and rolling direction Angle and In this case, the equation (6) is transformed into the following equation (7).

Expansion coefficients W ₄₀₀ , W appearing in the equations (6) and (7)
₄₄₀ is between the values of (1 / T _{0 °} + 2 / T _{45 °} + 1 / T _{90 °} ) and (1 / T _{0 °} -2 / T _{45 °} + 1 / T _{90 °} ) calculated previously, for example, There is a linear correspondence relationship as shown in the following expressions (8) and (9), and the expansion coefficients W ₄₀₀ and W ₄₄₀ can be easily calculated by using this relationship.

The calculation is performed by the calculator 40.

However, Since the expansion coefficient W ₄₀₀ and the in-plane average value of the plastic strain ratio have a constant correlation as shown in FIG. 6, for example, the in-plane average value of the expansion coefficient W ₄₀₀ to the plastic strain ratio is based on this correlation. Convert r.

Physically, this W ₄₀₀ corresponds to the volume fraction of the major orientation component of the texture, and corresponds to the volume fraction of the {111} plane in the cold-rolled steel sheet in which the {111} texture is dominant, That is, it corresponds to the value.

Further, since the expansion coefficient W ₄₄₀ and the in-plane orientation difference Δr of the plastic strain ratio have a constant correlation as shown in FIG. 7, for example, based on this correlation, the expansion coefficient W ₄₄₀ to the in-plane orientation of the plastic strain ratio The azimuth difference Δr is calculated.

From the measured values T _{0 ゜} , T _{45 ゜} , T _{90 ゜} , use the propagation distance L
V _S (0) ² , V _S (45) ² , V _S (90) ² are calculated, and W ₄₀₀ , W as shown in the following equations (10) and (11) using those values and the equation (6).
You may ask for ₄₄₀ .

In this way, the in-plane average value of the plastic strain ratio of the sample A, that is, the metal thin plate and the in-plane azimuth difference Δr are obtained, and the deep drawability of the metal thin plate is evaluated. Therefore, it is possible to obtain the plastic strain ratio by directly propagating ultrasonic waves to the metal thin plate without collecting test pieces, samples, etc. from the metal thin plate, and it is possible to perform evaluation by an appropriate nondestructive measurement as an online evaluation method. . Further, unlike the X-ray apparatus, a simple ultrasonic apparatus can be used, and even if the plastic strain ratio is obtained at short intervals (for example, 1 second / time), the measurement accuracy can be maintained at a constant level. Therefore, the plastic strain ratio can be obtained easily and quickly. Furthermore, since the plastic strain ratio is calculated by introducing the crystal orientation distribution relationship of the thin metal plate, it is possible to evaluate the arbitrary deep drawability and to generate at a frequency sufficiently lower than the thickness of the thin metal plate. Since the S ₀ mode ultrasonic plate wave with low velocity dispersion is used, the bottom echo of the ultrasonic wave does not pose a problem.

In the above embodiment, in order to perform positioning of the transmitter and receiver with respect to the sample and positioning between the transmitter and receiver, in the case where the probe 11, 12, 13 is fixed to a fixed distance shaft with a pair of transmitters and receivers. However, instead of this, a pair of copying rollers rollingly contacting the surface of the sample A may be provided in the sensor unit 2.

〔effect〕

As described in detail above, according to the apparatus of the present invention, when evaluating the deep drawability of a thin metal plate, the plastic strain ratio is determined by using the plate wave propagation time that can eliminate the error due to the lift-off fluctuation and the error due to the sample temperature fluctuation. Since the present invention can be obtained, the present invention exhibits excellent effects such as deep drawing of a thin metal plate with high accuracy and online.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an on-line configuration of the device of the present invention, FIG. 2 is a schematic plan view showing the relationship between each transmitter / receiver of a plate wave probe and a sample, and FIG. An enlarged vertical cross-sectional view of the ultrasonic flaw detector and the sample, FIG. 4 is a block diagram of the device of the present invention, FIG. 5 is a flowchart showing a processing process of a signal processing unit in the device of the present invention, and FIG. 6 is an inner surface average of plastic strain ratios. A graph showing the correlation between the value r and the expansion coefficient W ₄₀₀ of the crystal orientation distribution function, and FIG. 7 is a graph showing the correlation between the in-plane orientation difference Δr of the plastic strain ratio and the expansion coefficient W ₄₄₀ of the crystal orientation distribution function, FIG. 8 is a graph showing the relationship between lift-off change, probe impedance, and ultrasonic plate wave propagation time, and FIG. 9 is a graph showing the relationship between sample temperature and plate wave propagation velocity. 2 …… Sensor part, 3 …… Deep drawing property evaluation device body 6 …… Infrared radiation thermometer 8 …… Standard time signal generator 11 …… Rolling direction propagation plate Wave probe 12 …… Rolling 45 ° direction propagation plate Wave probe 13 …… Rolling orthogonal propagation plate wave probe 21,22,23 …… Pulser 31,32,33 …… Preamplifier, 43 …… Time measuring unit 44 …… Signal processing unit 51,52,53 …… Impedance measuring instrument, A …… Sample

Claims (1)

[Claims] 1. An ultrasonic plate wave of S ₀ mode is propagated in a rolled thin metal sheet in three directions, a direction parallel to the rolling direction and a direction intersecting with the rolling direction at 45 ° and 90 °, respectively. In a deep drawability evaluation device comprising a sensor unit for measuring a time for propagating a constant distance, and means for obtaining an in-plane average value of a plastic strain ratio and an in-plane orientation difference based on these measured values, the metal thin plate Based on the impedance change and the temperature change obtained by these measuring means, a means for measuring the impedance change of the sensor part due to the variation of the separation distance from the sensor part facing this and a means for measuring the surface temperature of the thin metal plate. And a means for correcting the propagation time of the ultrasonic plate wave, and a means for measuring and correcting the drift of a measuring instrument.