RU2024015C1 - Process of test of plate rolled stock with echo-through method - Google Patents

Abstract

FIELD: ultrasonic testing. SUBSTANCE: ultrasonic testing with use of echo-through method with automatic isolation of time interval of possible emergence of echo-through pulse due to use of additional acoustic channel located exterior to test zone is conducted. Selection of distance between uniaxial radiator and receiver depending on range of thicknesses of tested plate rolled stock and on measurement errors is optimized and velocity of contact liquid (water) is measured in process of test. EFFECT: increased authenticity in detection of surface flaws. 4 dwg

Description

 The invention relates to a control and measuring technique and can be used for ultrasonic flaw detection of plate products, when an echo-through control method can be effectively used.

 The technical task is to develop a method for flaw detection of plate, which allows reliable detection of defects, including near-surface.

 Known echo-through method of ultrasonic testing [1, 2], which consists in through sounding the controlled product, measuring the amplitude of the first transmitted pulse and the amplitude of the echo-through pulse located between the first and second transmitted pulses, determining the fact of a defect based on the ratio of the amplitudes of the echo pulse and the first transmitted pulse.

 The disadvantage of this method is the difficulty of allocating a time period within which an echo pulse from an internal defect may appear, since the length of this time period depends on the thickness of the product being monitored. If you set the time interval manually, then when monitoring sheet metal having a thickness, it is necessary to proceed from the smallest possible thickness of sheet metal so that the second transmitted impulse is not taken as an echo pulse. This leads to an increase in the uncontrolled upper and lower near-surface zones, where near-surface metal defects can be located.

-δτ, где L_р - расстояние между излучателем и приемником в зоне контроля;
L_и - расстояние между излучателем и приемником при прозвучивании толщи воды вне зоны контроля;
С_в - скорость звука в воде;
С_м - скорость звука в контролируемом листовом прокате;
Δt - измеренная разница времен прихода первого прошедшего импульса через толщу воды и через контролируемое изделие;
δτ - поправка на длительность второго прошедшего импульса и погрешность определения Δτ с целью получения заниженного значения Δτ, определения факта наличия дефекта на основании соотношения амплитуд эхо-импульса и первого прошедшего импульса.The closest in technical essence to the invention is a method of control by an echo-through method [3] by simultaneously sounding the water column outside the control zone and the controlled product in the control zone, measuring the difference in the arrival times of the first transmitted pulse through the water column and through the controlled product, measuring the amplitude of the first the pulse passing through the product, measuring the amplitude of the echo pulse in the time interval from the moment the first transmitted pulse passes through the controlled product to the time Spaced from the first transmitted pulse at time
Δτ = 2

-δτ, where L _p is the distance between the emitter and the receiver in the control zone;
L _and - the distance between the emitter and the receiver when sounding the water column outside the control zone;
C _in - the speed of sound in water;
With _m - the speed of sound in a controlled sheet metal;
Δt is the measured difference in the arrival times of the first transmitted pulse through the water column and through the controlled product;
δτ is the correction for the duration of the second transmitted pulse and the error in determining Δτ in order to obtain an underestimated value of Δτ, to determine the fact of a defect based on the ratio of the amplitudes of the echo pulse and the first transmitted pulse.

 The disadvantage of this method is the low reliability of detecting near-surface defects, which is caused by possible errors in determining Δτ and, therefore, an overestimated value of δτ. As a result, the upper and lower uncontrolled near-surface zones increase. The error in determining Δτ is due to the need to set the speed of sound in water, which can vary over a fairly wide range depending on the temperature of the water and the presence of impurities in it.

 The technical result of the invention is to increase the reliability of detection of surface defects.

l_max+l

, где l_max, l_min - наибольшая и наименьшая толщины контролируемого толстолистового проката;
δ_CM , δ_CB - относительные погрешности задания скорости звука в толстолистовом прокате и измерения скорости звука в воде.This is achieved by the fact that they additionally measure the difference in the arrival times of the first transmitted pulse through the water column outside the control zone and in the control zone in the absence of a controlled product and determine the speed of sound in water by the expression
With _in = (L _p - L _u ) / Δ t _o , where t _o is the measured difference in the arrival times of the first transmitted pulse through the water column outside the control zone and in the control zone in the absence of a controlled product; and the distance between the emitter and the sound receiver when sounding the water column is selected from the ratio
L _and = L _p -

l _max + l

, where l _max , l _min - the largest and smallest thickness of the controlled plate;
δ _CM , δ _CB are the relative errors of setting the speed of sound in plate hire and measuring the speed of sound in water.

 The essence of the invention lies in the creation of measurement conditions under which the error in calculating the time interval is reduced and it is possible to more accurately approach the second transmitted pulse when measuring the amplitude of the echo pulse. These conditions consist, firstly, in measuring the speed of sound in water and, secondly, in using the distance between the emitter and the receiver when sounding the water column outside the control zone, which ensures the smallest error taking into account the possible thickness range of the controlled products.

 In the proposed method, two operations are introduced - measuring the difference in the arrival times of the first transmitted pulse through the water column outside the control zone and in the control zone in the absence of a controlled product and installing a transmitter and receiver at a certain distance when sounding the water column that were not previously used to increase the reliability of detection of surface defects at control of plate hire.

 In FIG. 1 shows a sounding diagram of a water column outside a control zone and a controlled product in a control zone; in FIG. 2 - echo-through measurement method; in FIG. 3 is a functional diagram of a device that implements the method; in FIG. 4 is a timing diagram explaining the operation of the device.

 The invention allows to more reliably determine the zone of occurrence of the echo pulse during the control of plate in a wide range of thicknesses, and the end of this zone is determined while minimizing the possible error. An echo pulse may appear immediately after the first transmitted pulse and be located before the beginning of the second transmitted pulse. Therefore, to determine the end of the zone of appearance of the echo pulse, it is necessary for the appearance of the second transmitted pulse to know the arrival time of the second transmitted pulse.

In the invention, the calculation of the arrival time of the second transmitted pulse is carried out by measuring the moment of arrival of the first transmitted pulse through the water column. Indeed, if for the time t = 0 we take the moment of emission of an acoustic pulse both in the control zone and outside the control zone, then the moment of arrival of the first transmitted pulse outside the control zone is t ₁ = L _and / C _в , where С _в is the speed of sound in water , at the moment of the arrival of the first transmitted pulse in the control zone, t ₂ = (L _p - l) / C _in + l / C _m , where l is the current thickness of the rolled plate being controlled, C _m is the speed of sound in the metal.

+

Очевидно, что ΔT = t₃-t₂ =

выражая l из предпоследнего выражения и подставляя в последнее, получим
ΔT = 2

(1)
Из (1) видно, что величину ΔТ удалось выразить без знания толщины l (так как величины L_р, L_и известны заранее, Δt, С_в предложено измерять, С_м однозначно определяется маркой контролируемого металла). Реально величина ΔТ определяется с погрешностью, причем наиболее существенную погрешность вносят ошибки задания С_м и измерения С_в.In this way,
Δt = t ₂ -t ₁ =

+

Obviously, ΔT = t ₃ -t ₂ =

expressing l from the penultimate expression and substituting the latter, we obtain
ΔT = 2

(1)
From (1) it is seen that the magnitude of? T was able to express without knowledge thickness l (since the values L _p, L _and known in advance, Δt, _C. proposed measure, C _m is uniquely determined by the controlled metal mark). Actually, the ΔТ value is determined with an error, and the most significant error is introduced by the errors of the task C _m and the measurement C _c .

dC_в +

dC_м, (2) можно считать составляющую погрешности Δ_в, обусловленную погрешностью ΔС_в, равной
Δ_в=

C_в, (3) а составляющую погрешности Δ_м, обусловленную погрешностью ΔС_м, равной Δ_м=

C_м, (4) При переходе от (2) к выражениям (3) и (4) дифференциалы заменены приращениями, как и принято при анализе погрешностей. Вычисляя частные производные от выражения (1), получаем

= -

,

=

где ΔL = L_р - L_и . Учитывая, что Δt =

+

имеем

= -

;

=

Подставляя последние выражения в (3) и (4), получаем
Δ_в =

C_в (5)
Δ_м =

C_м (6)
Видно, что при уменьшении толщины листового проката Δ_вувеличивается, а
Δ_м уменьшается, и наоборот. Таким образом, самое неблагоприятное значение Δ_в реализуется при l_min, а Δ_м - при l_max, т.е.Indeed, due to the fact that the speed of sound in water depends on temperature, the presence of impurities, salinity, etc., due to spatial inhomogeneities in the distribution of the speed of sound in water, C _in cannot be determined with a high degree of accuracy. The same can be attributed to the speed of sound in a metal. We estimate the errors in ΔT caused by the errors C _in and C _m Since d (ΔT) =

dC _to +

dC _m , (2) we can consider the component of the error Δ _in , due to the error ΔC _in , equal to
Δ _in =

C _in , (3) and the error component Δ _m , due to the error ΔС _m equal to Δ _m =

C _m , (4) When passing from (2) to expressions (3) and (4), the differentials are replaced by increments, as is customary in the analysis of errors. Calculating the partial derivatives of the expression (1), we obtain

= -

,

=

where ΔL = L _p - L _and . Given that Δt =

+

we have

= -

;

=

Substituting the last expressions in (3) and (4), we obtain
Δ _in =

C _in (5)
Δ _m =

C _m (6)
It is evident that with decreasing thickness of the sheet metal _in Δ increases, and
Δ _m decreases, and vice versa. Thus, the most unfavorable value of Δ _in is realized at l _min , and Δ _m - at l _max , i.e.

C_в, (7)
Δ_{м max} =

C_м (8)
Чтобы обеспечить в двух крайних случаях l = l_min и l = l_max, допустимую погрешность требуется выбрать Δ_вmax= Δ_мmin . Тогда на границах области изменения l погрешности определения ΔТ будут совпадать, тем самым будет обеспечиваться наиболее равномерная погрешность во всем диапазоне контролируемых толщин. Приравнивая правые части выражений (7) и (8) и учитывая, что ΔL > l_min (это должно выполняться, чтобы первый прошедший через толщу воды импульс пришел раньше первого прошедшего импульса в зоне контроля), получаем
(ΔL-l_min)

= l

Обозначая через δС_в = ΔС_в/С_в, δС_м = ΔС_м/С_м где δС_в, δС_м - относительные погрешности определения скорости звука в воде и в металле соответственно, окончательно получаем L_р-L_и =

l_max+l_min (9) Выражение (9) входит в формулу изобретения. Например, если l_max = 60 мм, l_min = 10 мм, а δС_м/δС_в = 2/3, то L_р - L_и = 50 мм.Δ _{in max} =

C _in , (7)
Δ _{m max} =

C _m (8)
In order to ensure in two extreme cases l = l _min and l = l _max , the permissible error is required to choose Δ in _max = Δ _mmin . Then, at the boundaries of the region of variation l, the errors of determination of ΔТ will coincide, thereby ensuring the most uniform error in the entire range of controlled thicknesses. Equating the right-hand sides of expressions (7) and (8) and taking into account that ΔL> l _min (this must be done so that the first pulse passing through the water column arrives before the first transmitted pulse in the control zone), we obtain
(ΔL-l _min )

= l

Denoting _in δS = ΔS _in / _C, δS ΔS _m = _m / _m where C δS _a, δS _m - relative error in determining the velocity of sound in water and metal, respectively, we finally obtain L _{p u} = -L

l _max + l _min (9) Expression (9) is included in the claims. For example, if l _max = 60 mm, l _min = 10 mm, and δС _m / δС _в = 2/3, then L _p - L _and = 50 mm.

 When using the echo-through monitoring method, the amplitudes of the echo pulses appearing between the first and second transmitted pulses are measured. Moreover, each defect corresponds to two symmetrically located echo pulses (Fig. 2). To detect a defect, it is enough to measure the amplitude of any echo-through pulse. Since the first echo pulse in time can be masked by the first transmitted pulse, it is important when measuring the echo pulse to approach the second transmitted pulse as close as possible, but at the same time ensure that the second transmitted pulse is not taken as an echo pulse.

It follows that the time interval for measuring the amplitude of the echo pulse should be selected from the moment of the end of the first transmitted pulse through the controlled product to the time lag from the time of the arrival of the first transmitted pulse through the controlled product
Δτ = ΔT - δτ, (10) where ΔТ is determined from (1), and δτ - from the condition for compensation of the calculation error ΔТ so that Δτ is always less than the true value of ΔТ. The value of δτ should be selected when setting up a device that implements the proposed method. Expression (10) corresponds to that given in the claims.

To determine the speed of sound in water, it is proposed to measure the same gap between the first transmitted pulses to two channels (one in the control zone and one outside the control zone, only in the absence of the product being monitored. Then the indicated time interval is Δt _o = (L _p - -L _and ) / C _in and, therefore, C _in = (L _p - L _and ) / Δt _o . Measurements of Δt _o can be carried out before the start of control or between controlled products.

 Note that the proposed method allows you to effectively control not only plate products, but also other products of variable thickness with parallel surfaces.

The values of l _min and l _{max are} selected based on the technical requirements for the control device. So, when controlling the rolled plate under l _min and l _max understand the smallest and greatest thickness of the metal rolled on this mill.

 A device that implements the proposed method consists of a pulse generator 1, emitters 2, 3 acoustic vibrations, receivers 4, 5 acoustic vibrations, an amplitude discriminator 5, an amplitude-time discriminator 6, a temporary discriminator 7, a time interval meter 8, pulse shapers 9, 10 , buffer memory 11, calculator 12 and indicator 13.

l_max+l

, где L_р - расстояние между излучателем 2 и приемником 4;
l_max, l_min - наибольшая и наименьшая толщины контролируемого толстолистового проката; δС_м, δС_в - относительные погрешности задания скорости звука в толстолистовом прокате и измерения скорости звука в воде.Initially, the water column outside the control zone and the controlled product in the control zone are simultaneously heard. To do this, acoustic pulsers 2, 3 are excited by a pulse generator 1 (timing diagram 14 in Fig. 4), whereby the emitter 2 and its corresponding receiver 4 are located in the control zone, and the emitter 3 and its corresponding receiver 5 are outside the control zone. The distance L _and between the emitter 3 and the receiver 5 is selected from the condition
L _and = L

l _max + l

where L _p - the distance between the emitter 2 and the receiver 4;
l _max , l _min - the largest and smallest thickness of the controlled plate; δС _m , δС _в - relative errors of setting the speed of sound in plate steel and measuring the speed of sound in water.

 Then measure the difference in the arrival times of the first transmitted pulse through the water column and through the controlled product, the amplitude of the first transmitted pulse through the product and the amplitude of the echo pulse. To do this, the signals received by the receiver 4 (timing diagram 15) and receiver 5 (timing diagram 16) are processed using the amplitude discriminator 5 to measure the amplitude of the echo pulse, the amplitude-time discriminator 6 to determine the moment of arrival of the first pulse passed through the product and measure the amplitude this pulse and the temporary discriminator 7 to determine the moment of arrival of the first pulse passing through the water column.

 All three discriminators at the first input are reset to the initial state by a pulse from the second output of generator 1 (timing diagram 17), which arrives before the appearance of the first pulse passing through the water column.

 The amplitude-time discriminator 6 and the time discriminator 7 go into standby mode of arrival of the corresponding first transmitted pulse.

 At the moment of arrival of the first transmitted pulse through the water column, the time discriminator 7 generates a pulse (time diagram 19), which starts the time interval meter 8. At the moment of arrival of the first transmitted pulse through the controlled product, the amplitude-time discriminator 6 generates a pulse at its first output (time diagram 18), which stops the time interval meter 8 and starts the pulse shaper 9, and at the second output, the amplitude of the first transmitted pulse.

Shaper 9 pulses after a time equal to the duration of the emitted pulse generates a pulse (timing diagram 20), supplied to the third input of the amplitude discriminator 5 and puts it into standby mode of the echo pulse, and shaper 10 pulses through time τ _s generates a pulse (timing diagram 21 ) supplied to the fourth input of the amplitude discriminator and stopping its operation. At the output of discriminator 5, an amplitude of the echo pulse is formed. In this case, the pulse shaper 10 receives information on the duration of the interval Δτ between the first transmitted pulses and the moment of arrival of the first transmitted pulse from the receiver 4 at the first input, and information on the water velocity recorded in the buffer memory 11 at the second input.

 To fill the buffer memory 11, the difference in the arrival times of the first transmitted pulse through the water column outside the control zone and in the control zone in the absence of a controlled product is additionally measured. To this end, in the proposed device, the output of the time slot meter 8 is also connected to the first input of the buffer memory 11, and information about the absence of a monitored product that allows updating the buffer memory is supplied to the second input.

 The fact of a defect is determined based on the ratio of the amplitudes of the echo pulse and the corresponding first transmitted pulse through the controlled product. The indicated ratio is determined by the calculator 12, the first input of which receives the amplitude of the echo pulse, and the second input the amplitude of the first transmitted pulse. The calculator 12 divides the amplitude of the echo pulse by the amplitude of the first transmitted pulse and compares the specified ratio with a threshold.

 The threshold value depends on the sensitivity of the control and is selected in accordance with the recommendations of GOST 22707-88. Steel plate. If the amplitude of the first transmitted pulse is less than the predetermined small value, then this already indicates a defect and the calculator 12 does not calculate the ratio of the amplitudes of the echo pulse and the first transmitted pulse. The monitoring results are displayed on indicator 13.

Claims (1)

METHOD FOR CONTROLING THICK-TYPE RENTAL BY ECHO-THROUGH METHOD, consisting in the fact that at the same time sound the water column outside the control zone and the controlled product in the control zone, measure the difference in time, arrival of the first transmitted pulse through the water column and through the controlled product, measure the amplitude of the first passed through the product pulse, measure the amplitude of the echo pulse in the time interval from the moment of the end of the first transmitted pulse through the controlled product to the point in time, which is not equal to the time of arrival and the first transmitted pulse through the controlled product for a while
Δτ = 2

-δτ ,,
where l _p is the distance between the emitter and the receiver in the control zone;
o _u is the distance between the emitter and the receiver when sounding the water column outside the control zone;
C _b is the speed of sound in water;
C _m is the speed of sound in a controlled sheet metal;
Δt is the measured difference in the arrival times of the first transmitted pulse through the water column and through the controlled product;
δτ - correction for the error in determining Δτ in order to obtain an underestimated value of Δτ,
determine the fact of a defect on the basis of the ratio of the amplitudes of the echo pulse and the first transmitted pulse through the controlled product, characterized in that they additionally measure the difference in the arrival times of the first transmitted pulse through the water column outside the control zone and in the control zone in the absence of the controlled product and determine the speed of sound in water by expression
C _in = (L _p - L _and ) / Δt _o ,
where Δt _o is the measured difference in the arrival times of the first transmitted pulse through the water column outside the control zone and in the control zone in the absence of a controlled product,
and the distance between the emitter and the sound receiver when sounding the water column is selected from the ratio
L _and = L _p -

l _max + l

,
where l _max , l _{min the} largest and smallest thickness of the controlled plate;
δC _m , δC _in - relative errors of setting the speed of sound in plate hire and measuring the speed of sound in water.

Images