JP3469877B2 - Steel plate thickness measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] [0001] The present invention relates to a method for measuring the thickness of a steel sheet.
In particular, how to measure the steel plate thickness of tank bottom plate such as fuel tank
About the law. [0002] 2. Description of the Related Art Conventionally, in Japan, a steel plate for storing fuel is used.
Measurement of steel plate thickness using ultrasonic waves on the bottom plate of a cylindrical tank
It is performed according to the notice. That is, 5 mm from the inner surface of the side plate
For annular plates within the inner range of 00 mm, approximately 1
At regular intervals of 00 mm, for example, in a staggered
The thickness of the steel sheet is measured and the rest of the annular
And the bottom plate inside the
The steel plate thickness measurement is performed at the determined fixed point position. And
As a result of the thickness measurement of the bottom plate at the
Problem areas where the amount of reduction is greater than the reference value are detected
And a range of 300mm radius around that part is 30mm
Ultrasonic steel for each designated position divided at intervals
Perform plate measurement to understand the state of steel plate reduction near problem areas
Like that. However, as indicated in the fire notification,
When measuring only fixed point positions specified with an interval, the measurement
If a significant decrease in steel plate thickness is not detected
In fact, significant reductions in steel sheet thickness actually exist in areas other than the fixed points.
Even if it is present, it is overlooked, especially for local corrosion
It is not possible to detect the situation
The reduction in the thickness of the steel plate throughout the bottom plate
There is a problem that can not be. Also, at the fixed point position
When a decrease in steel sheet thickness is detected,
To re-measure the new fixed point,
Can easily and quickly measure the thickness of the bottom plate.
There is a problem that can not be. Because of this, if
Or automatically and continuously over a wide area of the tank bottom plate
A device for measuring the thickness is also used. [0003] The bottom plate of a steel plate cylindrical tank is
Coating to prevent corrosion of the bottom plate
Forming, coating, lining, or thermal spraying)
In many cases, it is made of a steel plate. In addition,
Epoxy, plastic and lining materials
Epoxy, glass flake, FRP, coating material
Is zinc paint and aluminum is the spray material.
You. When measuring the thickness of the tank bottom plate using ultrasonic waves,
Because the sound speed differs greatly between the minute and the steel plate, general supersonic
When measuring from the top surface of the coating using a wave thickness gauge, the actual
Very large measurement to determine bottom plate thickness, ie steel plate thickness
An error occurs. As a countermeasure, remove the film at the corresponding location
To measure the thickness of a sheet by using the multiple echo method
A method of measuring the thickness of a steel sheet with a wave thickness gauge, or
The acoustic thickness gauge and the eddy current-based thickness gauge are separately used together.
Is used. However, remove the coating
Except for the method of measuring the thickness of the steel plate only,
Must be re-coated, and the tank stopped during measurement.
In addition to the time problem that the period is long,
There is an economic problem that costs for film removal and recoating occur.
Was there. Also, use a multi-echo ultrasonic thickness gauge
In the thickness measurement method, there are many
Heavy echo may not be obtained.
The steel thickness is measured continuously over a wide area of the tank bottom plate.
Accurately determine the state of steel plate thickness reduction due to corrosion of the tank bottom plate
It was difficult to make a decision. Ultrasonic thickness gauge and thickness gauge
Is used separately in the area where backside corrosion exists.
It has the advantage of being able to measure thickness,
It is necessary to make a correction in consideration of the difference in sound speed between the steel sheet and the steel sheet.
For this reason, first, any arbitrary on the bottom plate from which multiple echoes can be obtained
At several locations, the total thickness of the coated steel sheet was measured using an ultrasonic thickness gauge.
Thickness and film thickness using ultrasonic thickness gauge
The thickness of each coating is determined using a
Of the ultrasonic wave propagating through the coating
Calculates the speed of sound and compensates for differences in sound speed between the coating and the steel plate
The sound velocity ratio, which is a correction coefficient for performing the above, has been determined. [0004] However, the sound speed ratio
Since the preliminary measurement for determining the
Fixed position, steel plate thickness measurement position, and coating thickness measurement position
It is difficult to match the positions perfectly. For this reason,
Errors due to mismatch of fixed points, artificial errors during measurement, etc.
It is difficult to accurately determine the sound speed ratio.
For example, using the general sound speed in steel sheets and coatings,
The speed ratio is estimated to be about 2, but it is optional on the tank bottom plate.
Select 6 locations for total thickness measurement and multiple echo method
From the measured values of the steel sheet thickness and coating thickness
When calculating the sound speed ratio, 1.86, 2.02, 2.30,
1.98, 2.12 and 2.21. The speed of sound obtained
The ratio fluctuates greatly in the range of 1.86 to 2.30,
Many measurements are required to determine the exact sound speed ratio
Cost, time and factor
The burden increases. And over the entire tank bottom plate
If backside corrosion is observed, use the multiple echo method.
Difficulty measuring the thickness of the steel sheet and unable to accurately determine the sound speed ratio
The case had arisen. The present invention has been made in view of such circumstances.
The measured value of the total thickness including the coating thickness and the steel plate thickness and the coating
Difference in sound speed from the correlation established between the measured values of film thickness
It is possible to determine the sound speed ratio taking into account and obtain the accurate steel plate thickness.
It is an object of the present invention to provide a method for measuring the thickness of a steel sheet. [0005] According to the present invention, there is provided the present invention having the above object.
Such a steel sheet thickness measuring method is a method for measuring the thickness of a coated steel sheet having a coating on its surface.
Ultrasonic thickness gauge that measures the overall thickness including coating thickness and steel plate thickness
And a thickness gauge equipped with a thickness gauge for measuring the thickness of the coated steel sheet.
In the method for measuring the thickness of a steel sheet using a measuring device,
Of the coated steel sheet measured simultaneously using a sheet thickness measuring device
From the correlation between the total thickness measurement value and the coating thickness measurement value,
The sound velocity of the ultrasonic wave when propagating through the steel plate
Ultrasonic sound speed and sound as it propagates through the coating of a coated steel plate
The speed ratio is uniquely obtained by statistical processing, and the sound speed ratio and the previous
The correction value calculated by the product of the coating thickness measurement values is used for the overall thickness measurement.
By subtracting from the constant value, the steel sheet thickness of the coated steel sheet
decide. [0006] A coated steel plate is provided in a thickness measuring device.
When measuring with an ultrasonic thickness gauge, the ultrasonic waves
Because the sound velocity of a plate propagates through two different materials,
Consider the difference in sound speed between the coating and the steel sheet for the measured values
Correction must be performed. At this time, the corrosion of the steel sheet
Except for the parts that are not
If the thickness is almost constant and the coating material is the same
If the sound velocity ratio between the coating and the steel plate is considered to be almost constant
Therefore, it is considered that the overall thickness increases as the coating thickness increases.
It is. Therefore, many samples obtained simultaneously by the thickness measuring device
Positive correlation between total thickness readings and coating thickness readings
Is considered to hold. Therefore, the total thickness measurement and
Statistics based on the positive correlation that exists between film thickness measurements
Process to propagate the steel sheet part of the coated steel sheet
Ultrasonic sound speed and supersonic wave propagating through the coating of coated steel plate
The sound speed ratio with the sound speed of the sound wave can be obtained. Overall thickness measurement
Measurement and film thickness measurement
Since the sound velocity ratio is determined by applying statistical processing to the
It is possible to determine a sound speed ratio with high performance. Also, the correction value
Is the sound velocity ratio from the correlation between the total thickness measurement value and the coating thickness measurement value.
Is calculated as the product of the measured thickness and the coating thickness.
A positive value can be obtained. [0007]Also,In the steel sheet thickness measuring method according to the present invention,
Where the correlation is the overall thickness measurement and the coating thickness measurement.
Is a linear function of the value, and the sound speed ratio is 1
The measured total thickness measured as a proportional constant of the following function:
And a minimum using all or a part of the relationship between the film thickness measurement values.
Uniquely by the square methodIt is determined.Depending on the thickness measuring device
Between the measured total thickness and the measured coating thickness
Determine the sound velocity ratio by the least squares method based on the correlation
High reliability that reflects the behavior of the actual overall thickness measurement
A high sound speed ratio can be uniquely determined. Where
The total thickness measurement and the coating thickness measurement used for the small square method are
Of the relationship between the measured total thickness and the measured coating thickness
Alternatively, it can be performed using a part. For example, when measuring
Values fluctuated due to artificial influences of steel, corrosion of steel sheet is remarkable
Location, excluding measured values near the weld, etc.
Applying multiplication to determine a more reliable sound speed ratio
can do. [0008] The coated steel sheet has a coating on the surface.
Equipped with an ultrasonic thickness gauge and film thickness gauge
When using a sheet thickness measurement device for measurement,
In the measurement with the provided ultrasonic thickness gauge, the coating surface
The ultrasonic waves emitted from the ultrasonic probe contacting the
It passes through and is reflected by the bottom of the steel plate until it reaches the ultrasonic probe.
Propagation time (2t₀ ) Is measured. Also, with a film thickness meter
Indicates that the coating thickness is directly measured. Therefore, if the coating thickness is T_E ,
Steel plate thickness T_U , The speed of sound in the coating_{C ,} The speed of sound in the steel plate
V_S Then, the relationship of equation (1) is established. t₀ = (T_E / V_C ) + (T_U / V_S ・ ・ ・ ・ ・ (1) In an ultrasonic thickness gauge of a plate thickness measuring device, for example,
If the sound velocity V_S Is calculated as a constant
Therefore, V_S Equation (2) obtained by multiplying
Left side of t ₀ V_S Is a cylinder measured by an ultrasonic thickness gauge
It corresponds to the entire thickness of the tank bottom plate. Here, the corrosion of the steel plate
Overall thickness measurements and coating thickness measurements obtained in less severe locations
For steel sheets, steel sheets are manufactured by rolling.
Since the plate thickness is considered to be almost constant, the expression (2) is
T_E Becomes thicker, the total thickness t of the tank bottom plate
₀ V_S This indicates that the relationship that increases Change
In addition, the sound speed of the ultrasonic waves,
Sound velocity V in the steel plate_S To
When the thickness is measured as a constant, the contribution of the coating thickness is
Speed ratio V_S / V _C (V_S / V_C ) ・ T
_E It is shown that it becomes. t₀ V_S = (V_S / V_C ) ・ T_E + T_U     ..... (2) From the relation of the equation (2), the total thickness (t₀
V_S ) And coating thickness (T_E ) Between the sound velocity ratio V_S / V_C
That the relationship of a linear function with
I understand. Therefore, it exists between the total thickness measurement and the coating thickness measurement.
The proportionality constant (sound
Speed ratio V_S / V_C ) Can be uniquely determined. Decision
Assuming that the specified proportionality constant is k, k is
Velocity ratio reflecting the condition of the coating on the bottom plate of the cylindrical tank and the steel plate
It has become. Equation (2) has an effect on the degree of corrosion of the steel sheet.
(2)
Expression V_S / V_C Is replaced by k, and the steel plate thickness T_U Show
When the equation (3) is obtained, an arbitrary point can be calculated using the equation (3).
From the measured total thickness and the measured coating thickness,_U Determine
Can be T_U = T₀ V_S −k · T_E                 ・ ・ ・ ・ ・ (3) The bottom plate of the cylindrical tank was measured with a thickness measuring device.
The measurement results obtained at this time are shown in FIGS. FIG.
The relation between the total thickness measurement value obtained by the ultrasonic thickness gauge and the measurement value frequency
The total thickness measurement is mainly 13-17 mm.
It is distributed in the range, and the most frequent value is about 14 mm.
FIG. 10 shows the measured values of the film thickness obtained by the film thickness meter and the measured values.
The value frequency relationship is shown, and the measured film thickness is mainly 0.3
Distributed in the range of 5 to 1.5 mm, the most frequent value is 0.65 m
m. Also, the vertical axis indicates the total thickness measurement value,
Thickness measurement as horizontal axis and measurement frequency as height axis
The representation is shown in FIG. Each of the measured values of the total thickness and the thickness of the coating film has a maximum value.
Since there is a frequency value, the stereoscopic display shown in FIG.
Is present, but between the total thickness measurement and the coating thickness measurement.
In other words, the vertical axis indicates the total thickness measurement value, and the
On a plane with the horizontal axis, the greater the coating thickness, the greater the overall thickness
That a linear function relationship holds that
I understand. The horizontal axis represents this relationship, and the vertical axis represents the overall thickness and height.
The frequency of the total thickness measurement is displayed on the axis, and the frequency is displayed schematically.
This is as shown in FIG. In FIG. 12, coating thickness and overall
Between the representative value of the thickness measurement value (for example, the most frequent value or the average value)
Is assumed to be a linear function, and the least-squares method
When the equation is determined, the slope of the most probable line corresponds to k.
FIG. 13 shows the film thickness on the horizontal axis and the entire vertical axis from the relationship of FIG.
As representative values (average values) of thickness, representative values of coating thickness and overall thickness
(Average value), which indicates the relationship between the coating thickness and the overall thickness.
Assuming linear function relationship with representative value (average value), minimum
When the slope of the most probable straight line is obtained by the square method, the value is 2.
086 (correlation coefficient at that time is 0.992)
Value estimated using the general sound speed of the plate and coating (about 2)
Indicates a good match. [0013] BRIEF DESCRIPTION OF THE DRAWINGS FIG.
First, an embodiment embodying the present invention will be described.
Provide understanding of Akira. Here, FIG. 1 shows an embodiment of the present invention.
Of the sheet thickness measuring device applied to the steel sheet thickness measuring method according to the state
Fig. 2 is a block diagram of the equipment.
FIG. 3 is a front view of a front measuring cart of the plate thickness measuring device,
FIG. 4 is a side view of a front measuring cart of the thickness measuring apparatus, and FIG.
Block diagram and diagram of the data processing system of the same thickness measuring device
6 is a plan view of a plate whose thickness is to be measured, and FIG.
Split shape of bottom plate of cylindrical tank measured by thickness measuring device
FIG. 8 is a plan view showing the state, and FIG.
Of the thickness of the annular and bottom plates of the cylindrical tank
FIG. As shown in FIGS. 1 to 4, one embodiment of the present invention
Thickness measuring device applied to the steel sheet thickness measuring method according to the embodiment
10 is on a bottom plate 31 made of a coated steel plate of a cylindrical tank.
A measuring unit 12 including a traveling measurement cart 11;
A calculation / display unit 13 for processing measurement data from the
Water supply for supplying water, which is an example of a couplant, to the fixed carriage 11
And a part 14. These are described in detail below.
I will tell. The calculation / display unit 13 and the water supply unit 14 are shown in FIG.
2 to 4 are not shown. As shown in FIGS. 1 to 3, the measuring unit 12
The front bogie 15 and the rear bogie 16 which are connected and
The measurement cart 11 is provided. Lower part of front bogie 15
The opening 17 provided in the center has a plurality of
Child carts 18 and 19 are provided. Each child cart 18,
19 is attached to the frame 20 and its front, rear, left and right
With a universal wheel 21 and at the center of each of the child bogies 18 and 19
Are reflection type ultrasonic probes 22, 2 as shown in FIG.
3 are arranged. And the rear part of each child carriage 18 and
A film thickness meter 24, 25 is provided at the front of each child carriage 19, respectively.
Have been killed. With such a configuration, the reflection
Type ultrasonic probes 22 and 23 are arranged in the width direction of the measurement cart 11.
And the total thickness in the entire width direction of the measuring cart 11
Enables measurement. Each of the child bogies 18 and 19 is a universal joint mechanism.
Front bogie 1 via gimbal mechanisms 26 and 27 as an example
5 are mounted side by side in the width direction of the front bogie 15
Swivel carts 18 and 19 regardless of vertical swing
The ring 21 is always in contact with the tank bottom 30 of the cylindrical tank.
Cars 18 and 19 move. That is, general
The tank bottom 30 is not a perfect plane but has a undulation
And locally welding the joint of the bottom plate 31
Because of the presence of corroded and corroded spots,
There are protrusions. Each child has such irregularities on the bottom surface 30 of the tank.
The bogies 18 and 19 move following and are attached to these
The ultrasonic probes 22 and 23 are always in a constant gap G (see FIG. 3).
Can move on the tank bottom surface 30
ing. Reference numerals 28 and 29 indicate the front left of the front bogie 15.
The right wheel and the rear left and right wheels are shown. A child carriage 18 arranged in front of the opening 17
And the child bogies 19 arranged on the rear side are at the same intervals, respectively.
It is arranged side by side in the width direction of the measurement cart 11,
The child bogie 19 in the rear row is attached to the child bogie 18
Are shifted by a half pitch (X / 2 in FIG. 3).
Have been. Thus, the ultrasonic probes 22 and 23 are mounted.
Trolleys 18, 19 with respect to the traveling direction of the measurement trolley 11.
And the sub-carts 18 and 19 in each row are flat.
In a staggered or zigzag pattern
The reasons are as follows. The ultrasonic probes 22 and 23 are fixed at the flaw detection area.
Each of which has a width of
Because it is attached, its frame 20 and free wheels 21
, The ultrasonic probes 22 and 23 adjacent in the same row
The approach distance L (see FIG. 3) is necessarily limited.
You. For this reason, for example, the child bogies 1 in the front row arranged in a horizontal row
8 alone, the adjacent ultrasonic probe
A band-shaped unmeasurable region is generated in the middle part of 22. this
Belt-like unmeasurable area caused by running of the child cart 18
The area is measured by the ultrasonic probe 23 of the rear carriage 19 in the back row.
So that each child can move with respect to the direction of movement of the front bogie 15.
The child cart 19 is arranged at the center position between the carts 18 and
The non-measurable region of the ultrasonic probe 22 is moved to the other ultrasonic probe 2
3 can be measured. In addition, each supersonic
The ultrasonic pulses from the wave probes 22 and 23
Fired, but those that can be used effectively for measurement
Super sound emitted from narrower part (effective beam width)
Waves. Therefore, in each row of the child bogies 18 and 19,
The pitch X between the centers in the width direction of the child carts 18 and 19 is adjacent to each other.
Only with a width that does not interfere with the ultrasonic probes 22 and 23
Is not less than twice the effective beam width of each of the ultrasonic probes 22 and 23.
It needs to be below. Here, the unmeasurable area of one row of ultrasonic probes
The width of the area is wide, that is, the unmeasurable area is
When the width is more than half of the mounting pitch,
The entire area is measured even for a group of placed ultrasonic probes.
In this case, three or more rows of ultrasonic
By providing a group of the tentacles in a step shape,
It is possible to measure the entire area in the width direction. In addition, the reflection type
As the acoustic probes 22 and 23, for example, a transmitter and a receiver
Split-type ultrasonic probe having separate transducers (ie,
Acrylic resin, polystyrene resin, etc.
Transmitting and receiving ultrasonic waves through wedges
Then, the bottom plate 31 of the cylindrical tank that is close to the transmission pulse is
Ultrasonic wave reflected from upper surface (that is, tank bottom surface 30)
Reflected by the bottom surface (back side) of the bottom plate 31 without being affected by the
Can be received, and the local
Can accurately measure the distance to the typical thinned part
You. [0020] The sub-carts 18 and 19 are provided respectively.
Eddy current sensors are used for the film thickness meters 24 and 25.
You. If there is a coating on the surface of the tank bottom 30,
The total thickness measured by the contacts 22 and 23 is the sum of the coating thickness and the steel plate thickness.
The thickness includes the total thickness. So, a vortex-type sensor
The actual coating thickness is measured by the thickness gauges 24 and 25
Then, the total thickness measurement obtained by the ultrasonic probes 22 and 23
Try to get more accurate measurements by subtracting from the constant
You. Here, the entirety obtained by the ultrasonic probes 22 and 23
The measured body thickness is the total thickness determined based on the speed of sound in the steel sheet.
Therefore, when subtracting the coating thickness, the difference in sound speed between the coating and the steel plate
It is necessary to correct the film thickness in consideration of the thickness. A rotary is provided on the front side of the front bogie 15 described above.
An encoder 32 is provided.
The rotational speed of the wheel 33 attached to the input shaft is detected,
The traveling distance of the measuring cart 11 can be electrically measured.
ing. The rotary encoder 32 is attached
The frame 34 is vertically movable or freely movable on the front bogie 15
Mounted on the wheel of the rotary encoder 32 at all times
33 rotates in contact with the tank bottom surface 30
You. Then, as shown in FIG. 2 and FIG.
At the front and rear of the upper side of the car 15, both the left and right sides are supported via support bases 35 and 36.
The horizontal guide wheel 37 has a part protruding from side to side.
It is provided in a state. This horizontal guide wheel 37 is
When the side bogie 15 is located near the inner side surface of the tank side plate
, The horizontal guide wheel 37 abuts the inner surface of the tank side plate
And can move smoothly. In addition, horizontal
By extending the protruding length of the id wheel 37, the tank
Repeat measurements in the direction along the inner surface of the side plate.
It becomes possible. For example, the protrusion length of the horizontal guide wheel 37
By extending the length to 275mm, the tank can be run twice
The entire area from the inner surface of the side plate to 550mm can be detected.
You. An eye bolt 38 is provided on the front side of the support base 35.
One end of the lever measuring cart 11 was fixed to the eyebolt 38
It can be pulled with a rope or the like. Further, as shown in FIGS.
A water distribution unit 39 is provided at the upper part of the car 15 and is disposed in front and rear.
Hose connections (nipples) 40, 41
Front bogie 1 using a flexible hose (not shown)
5 through the water supply holes provided in each ultrasonic probe 2
Water is supplied to the water sprinkling section provided at the lower end of 2, 23.
Gap between the ultrasonic probes 22 and 23 and the tank bottom surface 30
Is filled with water. By this, super sound
Ultrasonic waves are reliably propagated from the wave probes 22 and 23 to the bottom plate 31
As well as the reflected wave from the bottom plate 31
It can be propagated to the children 22 and 23. The rear carriage connected to the front carriage 15
The car 16 is provided on the bogie frame 42 in front, rear, left and right.
With four wheels 43 and a lid 44 on it
A box 45 is provided.
5 is provided with the controller 46 of the eddy current sensor.
Have been. The controller 46 controls the bottom of the tank.
The thickness of the coating applied on the surface of the plate 31 is calculated and calculated.
Output to the display unit 13; The eddy current
Although the principle of the sensor is well known, an alternating current is applied to the detection coil.
When the distance from the upper surface of the lower bottom plate 31 increases, it is detected.
When the impedance of the knowledge coil decreases,
Is compared with a pre-measured reference to detect the coating thickness
It is supposed to. Note that the cover 44 of the storage box 45 is
It is also possible to arrange the display of the controller 46. At the rear end of the rear bogie 16, a detachable
A handle 47 for operation of a predetermined height (about 60 to 90 cm) is provided.
The operator holds the handle 47 and holds the measuring cart 1
1 can be moved back and forth
You. This measurement can be performed by removing the handle 47.
Decrease the overall height of the trolley 11 and place it above the tank bottom 30
The measurement trolley 11 goes under the piping arranged in the tank.
The bottom plate 31 can be inspected.
Therefore, when the handle 47 is removed,
The height H can be, for example, about 200 mm.
To lower it further, the front carriage 15 and the rear carriage
Approximately 100 mm by separating from car 16
You can also. At the rear of the rear carriage 16, each ultrasonic probe
Connect the signal lines of the tentacles 22 and 23 to the controller 46
Signal line and power supply line, signal line of the rotary encoder 32,
And a bundle of control lines for the switch 48 for measurement start / end.
Cable 49 is provided. This cable 49 is at the base
Is fixed to the rear bogie 16 by the cable stopper 50
Have been. In addition, the switch 48 described above is operated and tabulated.
The signal is sent to the indicator 13 and the entire bottom plate 31 of the tank is
Starting and ending the measurement of body thickness and coating thickness
You. The water supply unit 14 shown in FIG.
A water tank 51 capable of storing water, and a water tank 51
Pump 52 for pumping water from the pump and discharge from the pump 52
Pump having a solenoid valve 53 for turning on and off the water
Start and stop of the operation of 52, and turn on the solenoid valve 53
Off indicates the start and end of the measurement provided on the measurement cart 11.
The signal of the switch 48 is transmitted to the computer of the operation / display unit 13.
56, and based on the instructions of the computer 56,
Done. Distribution of water between the water supply unit 14 and the measurement cart 11
Part 39 is connected by a flexible hose 54
And, if necessary, replace the water from the water tank 51 with an ultrasonic probe.
It is supplied between the tanks 22 and 23 and the tank bottom surface 30. As shown in FIG. 1 and FIG.
3 sends a predetermined signal to each of the ultrasonic probes 22 and 23.
And receives output signals from the ultrasonic probes 22 and 23
A multi-channel ultrasonic thickness gauge 55 and the ultrasonic thickness
55 are connected via an I / O board (not shown).
And a computer 56. This ultrasonic thickness gauge
55 is a multi-channel type and a plurality of ultrasonic waves connected thereto
While sending pulse signals to the probes 22 and 23,
Upon receiving the pulse signal detected by the tentacles 22 and 23, the bottom plate 31
Measuring the overall thickness of the
To 56. Also, the computer 56
The film thickness meters 24 and 25 are connected via the controller 46,
Rotary encoder 32 via counter board 57
Are connected respectively. In addition, the computer 56
CPU, RAM, ROM, auxiliary storage device, and I / O
(For example, an A / D converter)
On your computer, use the preset programs described below.
Depending on the system, the rotary encoder 32 and the controller 4
6, and processing of signals output from the ultrasonic thickness gauge 55
To calculate the steel plate thickness of the bottom plate 31,
Output to the output device (display or printer) to which it belongs
It is supposed to. The outline of the system of the computer 56 is as follows.
As shown in FIG. 5, the storage device such as a hard disk
A board drawing program 5 that performs the actual processing of the display unit 13
8, steel plate thickness display program 59, measurement program 60,
And a sound speed ratio determination program 61 are stored. Less than
Below, these are explained in detail. The above-mentioned drawing plan
The program 58 is arranged around the bottom plate 31 of the tank.
Number of annular plates and the size of the bottom plate 31
Input basic data necessary for creating a tank board layout diagram
By this, a plan drawing of the bottom plate 31 of the tank is created.
(See FIG. 7). This procedure (ie, program)
To calculate the position information of one board, and
Alone can be displayed alone on a CRT or the like.
Here, the created tank board drawing is used as the drawing data 62.
File. The measurement program 60 performs the measurement.
Arbitrary corner of the bottom plate 31 for the slab (unit plate)
(Or a specific position) with the origin as the distance from this origin
Enter the measurement direction and the measurement direction.
Total thickness measured according to the tally encoder measurement length
The data consisting of the measured values and the film thickness measured values is used to store position information in the plate.
Is added. The data is incremented by 1 every time a certain distance
Points / channel, ie one data for one subsection
Save the data. Many data in one subsection
The representative value (for example, the minimum overall thickness measurement).
Save as the data of the category. Drawing plan program 58
The plate of the object to be measured using the drawing data 62 created in
Select a corner to use as the origin. Along the tank circumference
Considering the case where the measurement cart 11 is run,
Enables thickness measurement even when the measuring cart 11 is running in an arc.
ing. The measurement position to be created and the overall thickness, steel plate thickness
(Calculated from equation (3) with k = 2), and
Save a file with information as the first measurement data 63
Exist. The sound speed ratio determination program 61 completes all measurements.
When the measurement is completed, the total thickness and the thickness in the first measurement data 63 are determined.
Using each measured value of the film thickness, the tank bottom to be measured
Determine the sound velocity ratio between the steel plate and the coating on the plate, and from the equation (3)
Find the corrected steel sheet thickness and calculate the measurement position and the corrected steel sheet thickness.
Save a file with information as the second measurement data 64
It exists. Determination of sound velocity ratio, gauge of corrected steel sheet thickness
Calculation and creation of the second measurement data 64 are performed in the following procedure.
U. 1) From the first measurement data 63, the measured value of the overall thickness is
Measurement that exceeds a predetermined value, for example, 90% or more of the design steel sheet thickness
Data (overall thickness measurement and corresponding coating thickness measurement
Value). 2) The extracted coating thickness measurement values are arranged in order of magnitude. 3) The degree of the total thickness measurement value corresponding to the coating thickness measurement value, respectively.
From the number distribution, a representative value of the total thickness measurement (eg, the most frequent value or
Average). 4) The representative value of the measured total thickness is t₀ V_S , Film thickness measurements
T_E As t₀ V_S And T_E During the period, t in equation (2)₀ V
_S = (V_S / V_C ) ・ T_E + T_U Holds the linear function relation of
, The proportionality constant (V_S / V_C )
To determine. 5) Change the corrected steel sheet thickness to T_U , The determined proportionality constant (V_S
/ V_C ) As k, T in equation (3)_U = T₀ V_S −k ・
T_E The corrected steel sheet thickness from the measurement position and the corrected steel
Create a file with the thickness information and create the second measurement data
Save as 64. Next, the steel plate thickness display program 59 will be described.
As will be described, the steel sheet thickness display program 59 displays the
Using the first measurement data 63, the second measurement
Creation of steel plate thickness distribution map for each plate using constant data 64
And the creation of an overall steel sheet thickness distribution map
U. These are described below, but first, the steel
The creation of the thickness distribution map will be described. Drawing data 62
The first measurement data 63 or the plotting data 62 and the second measurement data
Using the constant data 64, the steel
A color-coded display according to the plate thickness is performed. CRT (D
First measurement data 63 is applied to one pixel of
An appropriate representative value of (second measurement data 64) is displayed.
Thus, the following processing is performed. That is, as shown in FIG.
In addition, for example, one plate 65 is connected to the first measurement data 63 (first
2 (measurement data 64) was collected (one in the measurement direction).
Is divided into grids each having a fixed interval of one side, and this one grid is
The cell is referred to as a cell 66. Next, the first measurement data 63 (the second
Calculate the position and steel plate thickness from the measurement data 64) and
The steel sheet thickness data is set in the cell 66. Try to set
If the steel sheet thickness data has already been set in the cell 66
If so, perform a predetermined operation (for example, obtain the minimum value),
The steel plate thickness data of the cell 66 is updated. Where generated
File as a steel plate thickness data P for each plate
To save. Then, the entire board is displayed on the CRT.
To calculate the pixel size. Note that this pixel size is
66 so as to be an integral multiple of the area of 66. This number
The stopped cell is referred to as a block 67 (note that the block
67 and pixels are in a one-to-one relationship). A specific example is as follows. (Example) The number of CRT pixels is 640 x 480, and the horizontal length of the board is 7.
If the cell size is 200 mm and the cell size is 5 mm, 7200/640 = 11.25 / 12 (mm / pixel)
Lift 12/5 = 2.25 / 3 (cell / pixel) rounded up As described above, a 3 × 3 cell corresponds to one pixel. Soshi
Then, the cell 66 is stored in the block 67 obtained by the above method.
And perform a predetermined operation (for example, to obtain the minimum value)
The representative value of block 67 is calculated, and the
For each table value, a color code is displayed according to the thickness of the steel sheet. More than
By the procedure, the appropriate color classification distribution by the representative value can be displayed.
You. Next, creation of the entire steel sheet thickness distribution map
explain. Steel plate thickness data for each plate created by the above method
Using P, the entire bottom plate 31 of the tank is made to have a steel plate thickness.
The corresponding color display is performed. One CRT pixel to display
Follow the steps below to display the appropriate representative value of the measured data.
Work. First, the entire bottom plate 31 of the tank was measured
Constant multiple of the interval at which the sample was taken (constant interval in the measurement direction) (example
(For example, 5 times). This one grid
Is called a cell H. And from the steel plate thickness data P for each plate,
The steel sheet thickness data is set in the corresponding cell H. Set
Steel plate thickness data is already set in cell H
If the minimum value is obtained, a predetermined operation is performed.
), And updates the steel sheet thickness data of the cell H. here,
The generated file is referred to as the entire steel sheet thickness data Q. Next, the entire tank bottom plate is displayed on the CRT.
Calculate the pixel size as follows (become an integer multiple of cell H)
To do). Block the cells H organized by this number
Called D. Block D and pixels have a one-to-one relationship.
Shows a specific example. (Example) Number of CRT pixels is 640 x 480, diameter of tank bottom plate
Is 48000 mm and the size of one side of the cell is 25 mm
Combination 48000/480 = 100 (mm / pixel) 100/25 = 4 (cell / pixel) From the above, it is considered that a 4 × 4 cell corresponds to one pixel.
Become. The cell H obtained by the above method is stored in each block D.
Perform a fixed operation (for example, obtain the minimum value)
Calculate the representative value of the block D.
Color-coded display according to the thickness of the steel sheet. Follow these steps
Thus, an appropriate color-coded distribution based on the representative value can be displayed. Next, the thickness of the steel sheet according to one embodiment of the present invention will be described.
The measuring method will be described. For the ultrasonic probes 22 and 23
Measurement of the total thickness of the bottom plate 31 of the cylindrical tank by the transmitter
The ultrasonic pulse emitted from the coating, steel plate, steel plate bottom
Radiation, steel plate, and coating in this order, and reach the receiver.
Ultrasonic probe because it is done by measuring the time
The total thickness measured at 22 and 23 is the sum of the coating thickness and the steel plate thickness.
Become thick. On the other hand, the thickness measured by the film thickness meters 24 and 25
Is only the film thickness. Therefore, the ultrasonic probes 22, 2
3. Measured by the thickness gauges 24 and 25 from the total thickness obtained in
The bottom plate of the cylindrical tank
Bottom plate of actual cylindrical tank without removing 31 coatings
A steel plate thickness of 31 is obtained. In the width direction, six units are set (one unit is hidden in FIG. 3).
On the child carts 18 and 19
The provided ultrasonic probes 22 and 23 and the thickness gauge 24,
25 is a measuring cart 1 under a certain positional relationship when viewed in plan.
1 so that one position in the measuring cart 11
What is the positional relationship with the bottom plate 31 of the cylindrical tank?
If it is known, the ultrasonic probe 2 in the child carriages 18 and 19
The measurement positions of 2, 23 and the film thickness meters 24, 25 are circles.
The position corresponding to the bottom plate 31 of the cylindrical tank is known. Obedience
A rotary trolley for measuring the traveling distance
Attach the coder 32 to the specific position of the bottom plate 31 of the cylindrical tank.
By monitoring the distance traveled from the device,
The measurement positions of the probes 22 and 23 and the film thickness gauges 24 and 25 are
The position of the bottom plate 31 of the ink
It is possible to specify the coating thickness at the specific position and the total thickness at the same time.
Can be measured. Thus, the ultrasonic probe 2
Overall thickness according to 2, 23, coating with thickness gauge 24, 25
Combine thickness and measured value of rotary encoder 32
The thickness of the steel plate at a specific position in the bottom plate 31 of the cylindrical tank
Can be requested. Also, the relationship between the position and the thickness of the steel sheet is drawn.
When displayed on the surface, it extends over the entire bottom plate 31 of the cylindrical tank.
It is possible to grasp the state of steel sheet thickness reduction due to steel sheet corrosion
it can. Measurement of steel plate thickness of bottom plate 31 of actual cylindrical tank
Then, the measurer preliminarily sets the value on the bottom plate 31 of the cylindrical tank.
The measurement cart 11 is manually moved along the determined route.
And measure. The traveling speed of the measurement trolley 11 is
Is determined in consideration of the processing speed of the
The measurement is performed at a running speed of 00 mm / sec. In addition, this
In the embodiment of the present invention, the measurement trolley 11 is a hand-operated type.
To set up a sensor or decide the course in advance
In addition, the measurement cart 11 may be of a self-propelled type. [0039] The base tank in the tank where the approach height is restricted
Under a structure such as a vehicle, a handle provided on the rear bogie 16.
By removing the hand 47, the measurement cart 11 can enter
Thus, the bottom plate 31 of the cylindrical tank can be measured. Also after
The side carriage 16 has a controller 46 for the film thickness meters 24 and 25.
Height H is an example
For example, it is about 200 mm, but the height of the front bogie 15 is
For example, the height can be about 100 mm. This
Therefore, the front bogie 15 is separated from the measuring bogie 11 or
When the measurement is performed with the front bogie 15 alone,
It is possible to measure up to a gap of about 0 mm. in front
How to move the front trolley 15 when measuring with the trolley 15 alone
As an example of the method, an eyebolt provided at the front end of the front bogie 15
A method of attaching a string to the toe 38 and towing it can be adopted. Tan
Within the plane of the bottom plate 31 of the
Measurement near obstacles such as this plate
An active area is inevitably generated. Also in this case, the front bogie 15
Reduce or reduce the unmeasurable area by separating or offsetting
It is possible to do. In this embodiment, the ultrasonic probe 2
2, 23, effective beam width 25 mm, under static condition
Diameter in the range of 5 to 35 mm with respect to the measurement direction
The one that has the ability to detect a 2 mm flat bottom hole is
As a total of 24 and 25, the thickness in the range of 0 to 2 mm is measured.
The eddy current type sensor that can be
The measurement accuracy is 0.1%, and forward and backward distance measurement is possible.
I use something that can be used. In this case, the ultrasonic probe 2
Steel plate in case of combining eddy current sensor with 2, 23
The thickness measurement accuracy is ± 0.1 mm. The measurement data indicates that the moving distance is, for example, 5 mm.
Find the minimum value from all data read until
And use this as a representative value for the 5 mm
56 (see FIG. 5). Ultrasonic
The pulse repetition frequency of the thickness gauge 55 is 500Hz to 2k.
Hz, and one ultrasonic wave from the ultrasonic probes 22 and 23
The range measured by pulse transmission and reception is 25mm x 3
mm (25 mm is the ultrasonic probe 22,
Effective beam width perpendicular to the direction of movement of 23, 3 mm
Effective beam width). Therefore, the measurement cart 11 is set to 500 to
Undetected moving direction even when moved at a speed of 1000 mm / sec
No scratch area occurs. Accordingly, the thickness measurement according to one embodiment of the present invention
In the device, measurement is performed in the following steps as described above.
Will do. 1st process (Tank bottom plate splitting by board drawing program 58
Create diagrams) Before the measurement, create a bottom plate plan based on the tank drawing.
You. Second step (measurement by measurement program 60) Select the plate from which to start the measurement from the bottom plate plan view. Third step (selection of origin of measurement start position) Select the origin of the measurement start position from the corner of the plate. Fourth step (input of measurement start position) Enter the measurement start position at the distance from the origin selected in the third step.
Power. Fifth step (selection of measurement direction) Select the measurement direction from up, down, left and right. Sixth step (selection of measurement mode) Select straight-line driving or circumferential driving. Step 7 (start of measurement) The reference of the measurement trolley 11 at the measurement start position input in the fourth step
At this point, the switch 48 for starting measurement is pressed. That
Then, push the measuring cart 11 in the measuring direction selected in the fifth step.
While doing the measurement. Eighth step (end of measurement) When the measuring cart holder comes to the end point of the plate in the measuring direction,
The switch 48 for ending the measurement is pressed. Ninth step (next measurement) The measurement cart 11 is moved to the next measurement start position, and the fourth step is performed.
And the eighth step is repeated. This makes it possible to measure the target plate
Complete. Tenth step (creation of steel plate thickness distribution map for each plate) Using the steel plate thickness display program 59, set the plate to be measured
A color-coded display according to the thickness is performed. Eleventh step (next plate measurement) Repeat the second to tenth steps, and repeat
Complete the board measurement. Twelfth step (creation of thickness distribution map) Using the steel plate thickness display program 59, the entire tank bottom plate
A color code is displayed according to the thickness of the steel sheet. Thirteenth process (Create a steel plate thickness distribution diagram for each plate after all measurements are completed)
Success) Using the steel plate thickness display program 59, the second measurement data
Color classification table according to the thickness of the steel plate with the target plate modified from 64
Perform the following. Fourteenth step (Creating a diagram of the entire steel sheet thickness distribution after completion of all measurements)
Success) Using the steel plate thickness display program 59, the second measurement data
Colors corresponding to the steel plate thickness, with the entire tank bottom plate modified from 64
Display. Subsequently, the plate thickness measuring device 10 was set to an inner diameter of 22 m.
Applied to the thickness measurement of the bottom plate 31 of the cylindrical tank
This will be further described. The contents of the measurement are set in the initial
It is divided into constant condition setting, measurement method, and measurement result display. [Initial condition setting] Tank inner diameter, number of annular plates, bottom plate
The computer 56 of the calculation / display unit 13 calculates the size of the basic plate.
To enter. The computer 56, based on the input data,
Draw the annular plate and divide the entire bottom plate vertically or horizontally,
Draw a bottom plate split map while further dividing each of the split areas.
To achieve. The divided areas are automatically numbered.
You. FIG. 7 shows the thickness of the bottom plate 31 of the cylindrical tank having an inner diameter of 22 m.
FIG. 3 shows a bottom plate section diagram created when measurement is performed. In addition, this
The processing such as is described in detail in the above section.
It is omitted here. [Measurement condition setting] The number of the plate to be measured from the bottom plate
Select (see Fig. 7) and measure the plate with the selected number
Determine the origin, measurement start point and measurement direction. [Measurement method] a) Input the position of the measurement start point by displacement from the origin. b) Match the reference point of the measurement cart 11 to the measurement start position
Then, the switch 48 for starting the measurement is turned on. c) The measuring cart 11 is moved at a speed of 500 to 1000 mm / sec.
Move in the measurement direction. The measurement cart 11 indicates the measurement direction.
The laser oscillator laser previously installed
The optical axis of the laser beam and the traveling direction of the measurement cart 11 match.
To move. d) Measurement is completed when the measuring cart 11 reaches the end point of the plate.
Switch 48 is turned on. e) From the end point position, move the measurement cart 11 to the next measurement start position.
Move. Note that the direction perpendicular to the measurement direction of the measurement cart 11 (9
In the case of movement in the 0 ° direction, use a cart that moves in the orthogonal direction.
did. The cart that moves in the orthogonal direction is loaded with the measurement cart 11 and
Dedicated platform that moves in the direction perpendicular to the measurement direction of the fixed carriage 11
It is a car. f) The above steps a) to e) are repeated to select the plate of the selected number.
When the measurement trolley 11 moves on the entire inner surface,
The measurement of the plate ends. g) Select the number of the plate to be measured next from the bottom plate
Perform a) to f). h) Measurement of thickness of all plates is completed in the bottom plate
That the thickness measurement of the bottom plate 31 of the tank has been completed
become. [Measurement result display] During the measurement, the steel
Real-time measurement results of sheet thickness according to the degree of sheet thickness
Color-coded on the screen to show the steel plate thickness reduction status on the screen.
Wear. During the measurement, the measurement object
Since the sound velocity ratio of the ultrasonic wave in the coating is not known,
The steel plate thickness is calculated from equation (3) using the approximate value of 2.
You. After measurement, k is determined for the measurement object
Then, from the equation (3), using k determined in the bottom plate plan view,
Color-coded display of the calculated steel thickness according to the thickness of the steel
And select a plate with an arbitrary number, and color distribution chart of steel plate thickness
And vertical and horizontal sheet thickness cutting at any position in the selection plate
The state of the surface can be displayed on the screen. These screen contents
Is output by a color printer, which is an example of an output device.
it can. In addition, the average steel sheet thickness and the minimum steel sheet thickness for each sheet number
Displays and outputs the value and distribution of the area over a certain steel plate thickness
It is possible to Bottom plate of cylindrical tank with inner diameter of 22m
Example of steel plate thickness reduction situation obtained in 31 thickness measurement
The design steel plate thickness (annular plate part: 12 mm, bottom plate
Part: 9 mm) as 100%)
FIG. 8 shows the situation of the conversion. In addition, the bottom plate 31 of the cylindrical tank
Tables 1 to 6 show the measurement results for each plate shown in the bottom plate
The thickness of the steel plate obtained over the entire bottom plate 31 of the cylindrical tank
Table 7 shows the relationship between the areas. Note that such processing is
Since it has been described in detail in the above description, the description is omitted here. [0047] [Table 1] [0048] [Table 2][0049] [Table 3] [0050] [Table 4] [0051] [Table 5] [0052] [Table 6][0053] [Table 7] The embodiment of the present invention has been described above.
The present invention is not limited to this embodiment,
For example, the film thickness measurement values are arranged in order of magnitude, and
Representative of the measured thickness and the overall thickness measurement for the coating thickness measurement
Least squares using values (eg, most frequent or average)
The sound velocity ratio between the steel sheet and the coating was determined from
It is arranged in the order of size and divided into sections having a predetermined width.
The most frequent value or average value as the coating thickness measurement value representing the interval,
The most frequent value or average as the total thickness measurement value representing each section
Of sound velocity ratio between steel plate and coating by least squares method using values
May be. [0055] 【The invention's effect】Claim 1In the steel sheet thickness measurement method described
Of coated steel sheet measured at the same time using a thickness measuring device
From the correlation between the overall thickness measurement value and the coating thickness measurement value,
Velocity of ultrasonic wave when propagating through the steel plate part
The sound velocity ratio to the sound velocity of the ultrasonic wave when propagating through the coating
After the measurement of the total thickness and coating thickness of the
And the correction value of the measured film thickness using the sound velocity ratio.
And determine the thickness of the coated steel sheet from the measured total thickness
The need for prior measurement to determine the sound speed ratio.
Therefore, the work efficiency of steel plate thickness measurement can be improved.
In addition, the reliability of the correction value of the coating thickness measurement value based on the sound speed ratio is
This makes it possible to accurately measure the thickness of the steel sheet. [0056]Further, according to the present invention,Steel plate thickness measurement method
In other words, the correlation is the primary relationship between the total thickness measurement value and the coating thickness measurement value.
And the sound speed ratio is proportional to the proportionality constant of the linear function.
The relationship between the measured overall thickness and the measured coating thickness
Uniquely determined by least square method using all or part
After the measurement of the total thickness and the measurement of the coating thickness are completed,
A highly reliable sound speed ratio can be determined in a short time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of each device of a sheet thickness measuring device applied to a steel sheet thickness measuring method according to an embodiment of the present invention. FIG. 2 is a side view of a measuring unit of the plate thickness measuring device. FIG. 3 is a front view of a front measuring cart of the plate thickness measuring device. FIG. 4 is a side view of a front measuring cart of the thickness measuring apparatus. FIG. 5 is a block diagram of a data processing system of the thickness measuring apparatus. FIG. 6 is a plan view of a plate whose thickness is to be measured. FIG. 7 is a plan view showing a state in which the bottom plate of the cylindrical tank is split by the plate thickness measuring device. FIG. 8 is an explanatory diagram showing the thickness of the annular plate and the bottom plate of the cylindrical tank measured by the plate thickness measuring apparatus. FIG. 9 is a frequency distribution diagram showing a distribution state of measured values of the total thickness obtained by the ultrasonic thickness meter. FIG. 10 is a frequency distribution diagram showing a distribution state of measured film thickness values obtained by a film thickness meter. FIG. 11 is a frequency distribution diagram showing a distribution state of an overall thickness measurement value and a coating thickness measurement value. FIG. 12 is a schematic diagram of a frequency distribution showing a distribution state of a measured value of an entire thickness and a measured value of a coating thickness. FIG. 13 is a graph showing a relationship between a film thickness and a representative value (average value) of the entire thickness. [Explanation of Signs] 10: thickness measuring device, 11: measuring cart, 12: measuring unit,
13: calculation / display unit, 14: water supply unit, 15: front trolley, 16: rear trolley, 17: opening, 18, 19: child trolley, 20: frame, 21: free wheel, 22, 23: super Acoustic probe, 24, 25: film thickness gauge, 26, 27: gimbal mechanism, 28, 29: wheels, 30: tank bottom, 31:
Bottom plate, 32: rotary encoder, 33: wheel, 3
4: frame, 35, 36: support, 37: horizontal guide wheel, 38: eyebolt, 39: water distributor, 40, 4
1: hose connector (nipple), 42: bogie frame,
43: wheels, 44: lid, 45: storage box, 46: controller, 47: handle, 48: switch, 49: cable,
50: cable stopper, 51: water tank, 52: pump,
53: solenoid valve, 54: hose, 55: ultrasonic thickness gauge, 5
6: Computer, 57: Counter board, 58: Sheet drawing program, 59: Steel plate thickness display program, 60:
Measurement program, 61: sound velocity ratio determination program, 62:
Plotting data, 63: first measurement data, 64: second measurement data, 65: plate, 66: cell, 67: block

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tatsuya Fukunaga 4-18 Konan, Minato-ku, Tokyo Asahi Engineering Co., Ltd. (72) Inventor Hiroyuki Haga 4- 1-8 Konan, Minato-ku, Tokyo Asahi Engineering Co., Ltd. (72) Inventor Fuminori Kiyota 4-10-13 Ibori, Kokurakita-ku, Kitakyushu-shi, Fukuoka Prefecture New Japan Non-Destructive Inspection Co., Ltd. 4-10-13, Ibori New Japan Non-Destructive Inspection Co., Ltd. (72) Inventor Yasuhiko Wakibe 4-10-13, Ibori, Kokurakita-ku, Kitakyushu-city, Fukuoka Prefecture Yuji Nishimura 4-10-13 Ibori, Kokurakita-ku, Kitakyushu-shi, Fukuoka Pref. New Japan Non-Destructive Inspection Co., Ltd. (56) References JP-A-6-88720 (JP, A) JP-A-8-3 04062 (JP, A) JP 2001-50736 (JP, A) JP 2002-228431 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 17/00-21/32 G01N 29/00-29/28

Claims (1)

(57) [Claims 1] An ultrasonic thickness gauge for measuring the coating thickness of a coated steel sheet having a coating on its surface and the overall thickness including the steel sheet thickness, and measuring the coating thickness of the coated steel sheet. In the method for measuring the thickness of a steel sheet using a thickness measuring device provided with a thickness gauge, from the correlation between the measured value of the total thickness of the coated steel sheet and the measured thickness of the coating thickness, which are simultaneously measured using the thickness measuring device. The sound speed ratio between the sound speed of the ultrasonic wave when propagating through the steel plate portion of the coated steel plate and the sound speed of the ultrasonic wave when propagating through the coated steel plate portion of the coated steel plate is uniquely determined by statistical processing, and the sound speed ratio and The steel plate thickness of the coated steel sheet is determined by subtracting the correction value calculated by the product of the film thickness measurement values from the overall thickness measurement value , and the correlation is obtained by comparing the total thickness measurement value and the film thickness measurement. Value of
It is a relation of a linear function, and the sound velocity ratio is a linear function.
The measured total thickness and the previous
Least squares using all or part of the relationship
A steel sheet thickness measurement method that is uniquely determined by the method.