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FIELD OF INVENTION
The present invention relates to a method for non-destructive measurement of
ultrasonic time of flight for a fixed distance in rolling direction for example 45
and 90 degree to the rolling direction. The invention further relates to a method
of predicting formability r bar in cold rolled and annealed steel sheets by
correlating these ultrasonic parameters, sample thickness and composition of the
grades of steel sheets. More particularly, the invention relates to an in-situ
method of ultrasonic measurement including co-relation of device features to
accurately and quickly predict r-bar in cold rolled and annealed steel sheets.
BACKGROUND OF THE INVENTION
The cold rolled and annealed steel sheets develop directionally (anisotropy)
which shows change in mechanical properties like elastic modules, yield strength,
ductility in different directions. Generally minimum and maximum values of these
quantities occur at 0°, and around at vicinity of 45° and 90° with respect to the
roiling direction. When forming a sheet metal, practical consequences of
directionality, a measure of formability, include phenomena for example, excess
wrinkling, puckering ear forming, local thinning or rupture, which might lead to
scraptring of the steel sheets. A more serious consequence may be the downtime
required to correct the manufacturing process.
The severity of directionality (a measure of formability) in conventional method is
measured as plastic strain ratio defined as

where ew is the strain ratio in the width direction and
et is that in the thickness direction.

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The normal anisotropy is defined as

The phenomenon 'anisotrophy' or r bar has been found to be a parameter to
control the drawability and hence formality of the steel sheets. Usually it is
measured by destructive methods of testing in which the samples need to be cut
from the sheets. These methods include tensile testing and magnetostrictive
oscillator technique to determine resonance frequency in a specified specimen
length, r bar values can also be determined by other technique like XRD (X-ray
diffraction) which is again destructive, include localized measurements, time
taking and tedious.
Thus, there exists a need for a method for no n-destructive ultrasonic
measurements to quickly predict r bar which provides larger volume for
ultrasonic waves to interact with the different crystallographic planes which
incorporate the directionality (a measure of formability) in the steel sheets.
OBJECTS OF THE INVENTION
Accordingly, it is an object of the present invention to propose an in-situ method
of ultrasonic measurement including co-relation of device features to accurately
and quickly predict r-bar in cold rolled and annealed steel sheets which is non-
destructive and does not need to cut the sheets to prepare samples for testing.
Another object of the invention is to propose an in-situ method of ultrasonic
measurement including co-relation of device features to accurately and quickly
predict r-bar in cold rolled and annealed steel sheets which allows larger volume
of ultrasonic waves to interact with different crystallographic planes which
incorporate the directionality in the steel sheets.

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A further object of the invention is to propose an in-situ method of ultrasonic
measurement including co-relation of device features to accurately and quickly
predict r-bar in cold rolled and annealed steel sheets which can be carried-out on
the shop floor Itself.
A still further object of the invention is to propose an in-situ method of ultrasonic
measurement including co-relation of device features to accurately and quickly
predict r-bar In cold rolled and annealed steel sheets which adapts digital
ultrasonic flow director and direct contact process using two probes.
Yet another object of the invention is to propose an in-situ method of ultrasonic
measurement including co-relation of device features to accurately and quickly
predict r-bar in cold rolled and annealed steel sheets which is capable of being
performed online by mere use of additional instruction.
SUMMARY OF THE INVENTION
Experimental results have proved that using two surface waves probes of
frequency 4 MHz (one transmitter and another receiver fixed in a Perspex sheet
at a fixed distance) and measuring the time of flight of ultrasonic waves from
transmitter to receiver, it is possible to predict the formability r bar in cold roiled
and annealed sheets within an accuracy of ± 1.69%. For this, a device feature
relationship for correlating the time of flights in rolling direction (To) as well as
those at 45 and 90 degrees with respect to rolling direction (T45) and (T90)
respectively, including %C, %Mn, %P, % MA (microalloying elements), % A1
hardness in HRB and the formability r bar, has been established- The device
feature relationship leading to measurement of r bar according to the invention is
: r bar = (0.160761*A + 0.221348*B + 0.222373*C - 0.61272*D - 3.15983E +
C.946728*F + 28.3329*G - 6.01249+H + 1.048401*1 - 0.04484*] + K)

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where,
A = T0
B = T45
C = T90
E = %C
F = % Mn
G = % P
H = % Tl
I = % A1
] = Hardness value, HRB
K = 3.55564

The time of flight are measured in micro µ sec. The chemical composition is in
weight %. The correlation to-efficient r square is found to be 0.9947.
Accordingly, there is provided An in-situ method of ultrasonic measurement
inducting correlating of device features to accurately and quickly predict r-bar in
cold rolled and annealed steel sheets, comprising providing a digital ultrasonic
flaw detector, and a computer controlled pulse receiver; providing atleast two
probes fixed in a perspex sheet at a fixed distance; measuring ultrasonic time of
flights using the atleast two probes and the flaw detector in the directions 0D, 45°
and 90º with respect to rolling direction in different steel sheets*, correlating the
measured time of flights with the device features of the steel sheets including
the formalcibility r bar to establish a device feature relationship such as:


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and annealed steel sheets by application of the established device feature
relationship.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig, 1 - a pictorial view showing measurement of Time of Flight of ultrasonic
wave from transmitter to receiver at 45° to the rolling direction
Fig. 2 - a pictorial view showing a typical RF signal for measurement of Time of
Flight of ultrasonic wave between transmitter to receiver.
Fig. 3 - a schematic diagram showing angles from the rolling direction along
which time of flight was measured from the RF signals.
Fig, 4 - a graphical representation showing correlation between measured r bar
using Module r bar tester and ultrasonically predicted r bar in CQ, DQ, EDD and
IF grades of cold rolled and annealed steel sheets.
Fig. 5 - a graphical representation showing error in ultrasonically r bar values.
Fig. 6 - shows a graphical representation of the linear line fit graph between To
and predicted r bar which although shows a poor correlation but the trend
indicates decrease in r bar with increase in To,
Fig. 7 - shows a linear line fit graph between T45 and predicted r bar which
shows a good correlation and the trend indicates decrease in r bar with increase
inT45

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Fig. 8 - shows 3 linear line fit graph between T90 and predicted r bar which
shows a poor correlation but the trend indicates decrease in r bar with increase
in T90-
Fig. 9 - shows a linear line fit graph between Tbar and predicted r bar which
shows a fair correlation and the trend indicates decrease in r bar with increase in
Tbar
Fig. 10 - shows a linear line fit graph between % C and predicted r bar which
shows a good correlation and the trend indicates decrease in r bar with increase
in % C.
Fig. 11 - shows a linear fine fit graph between % Mn and predicted r bar which
shows a good correlation and the trend indicates decrease in r bar with increase
in % Mn.
Fig. 12 - shows a linear line, fit graph between % P and predicted r bar which
shows a poor correlation but the trend indicates decrease In r bar with increase
in %Mn.
Fig. 13 - shows a linear line fit graph between % 71 and predicted r bar which
shows a fair correlation but the trend indicates increase in r bar with increase in
% Mn.
Fig. 14 - shows a linear line fit graph between % AI and predicted r bar which
shows a poor correlation but the trend indicates decrease in r bar with increase
in % Mn.

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Fig. 15 - shows a linear line fit graph between hardness and predicted r bar
which shows a good correlation and the trend indicates decrease in r bar with
increase in hardness HRB.
DETAILED DESCRIPTION OF THE INVENTION
As shown in the accompanying figures constituting graphical and schematic
diagrams. The surface wave of ultrasound generally travel along the surface of a
material at a depth of 1(one) wavelength from the surface. While traveling, it
interacts with the detailed structure of the medium in which it travels. In cold
rolled and annealed steel sheets the wave velocity changes in different directions
from the rolling direction depending upon the intensity of different
cryatallographic: planes., which govern directionality (a measure of formability) in,
the steel sheets.
As time of flight is directly related to the ultrasonic velocity its value in 0, 45 and
90 degree from the rolling direction along with the chemistry like %C, %Mn, %P,
%MA (micro-alloying elements) % AI and hardness in HRB can be correlated
with the r bar.
It has been observed from the correlation that decreasing %C, %Mn, %P and
thickness of the test sample increases r bar value and hence the formability of
the steel sheets. Increase in microalloying elements increase r bar value and
decrease in Tbar which indicates an increase in r bar.
Such device feature relationship can be used for non-destructive prediction of r
bar in cold rolled and annealed steel on the shop floor.

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EXPERIMENTAL WORK
Details of the materials used for ultrasonic evaluation :
CQ, DQ, FDD, IF grades of steel produced by TATA STEEL
Details of the Digital Ultrasonic Equipment & Surface Wave Probe:
Make 7 Model : Ultrasonic Flaw detector EPOCH-4, and computer controlled
Pulser Receiver PR-5800, Panametrics, USA.
Probe : 4MHz, 8x9 mm, 90° angle (Surface wave)
Technique : Through transmission using two probes fixed in a Perspex sheet at a
fixed distance as shown in Fig. 1, Time of flight was measured from the RF
signals by as shown in Fig, 2.
Couplant: Machine oil
The details of the samples considered for ultrasonic measurements have been
shown in Table 1 and Table 2. r bar was measurement by Magnetostrictive
Oscillator Technique in the directions as shown in Fig. 3, Ultrasonic time of flights
In the directions 0º, 45° and 90° from the rolling direction in different sheets
were measured in CQ, DQ, EDD, IF grades of steel sheets, These were tested for
r bar measurement using Magnetostrictive Oscillator Technique and the results
tabulated in Table 3.

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Table 1: Chemical compositions of different grades of steel sheets used fro time
of flight measurement by ultrasonic technique.
Coil# %C %Mn %P %S %S1 %C %Cu %A1 %N %TI
1 0.002 0.08 0.01 0.008 0.007 0.0271 0.007 0.0037 28 0.067
2 0.003 0.07 0.01 0.009 0.006 0.024 0.005 0.030 32 0.060
3 0.003 0.08 0.01 0.010 0.007 0.018 0.009 0.040 34 0.070
4 0.070 0.47 0.01 0.008 0.007 0.013 0.006 0.034 32 0.000
5 0.060 0.510 0.02 0.006 0.009 0.037 0.006 0.048 52 0.000
6 0-070 0.500 0.01 0.006 0.008 0,025 0.005 0.054 30 0.000
7 0.070 0.500 0.01 0.006 0.008 0.025 0.005 0.054 30 0.000
8 0.050 0.470 0.01 0.005 0.008 0.019 0.005 0.052 33 0.000
9 0.060 0,510 0.02 0.007 0.064 0.025 0.004 0.050 35 0.000
10 0.030 0,220 0.02 0.006 0.006 0.024 0.005 0.048 36 0.000
11 0-035 0.180 0,01 0.009 0,007 0.025 0.005 0.037 39 : 0.000
12 0.030 0.170 0.02 0.011 0.007 0,032 0.005 0.048 43 0.000
Table 2: Mechanical properties of different grades of steel sheets used for time
of flight measurement by ultrasonic technique.
Coil# Grade Hardness, HRB UTS, Mpa YS, MPa % Elongation r bar
1 IF 32 299 147 49 1.9
2 IF 35 295 134 50 1.91
3 IF 29 304 157 49 1.92
4 DQ 56 337 214 41 1.41
5 DQ 59 337 220 38 1.59
6 DQ 57 337 215 40 1.5
7 DQ 56 337 214 41 1.52
8 DQ 55 326 212 40 1.52

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9 CQ 60 - - - 1.43
10 CQ 44 331 225 40 1.44
11 EDD 37 288 169 48 1.81
12 EDD 50 308 153 50 1.7
Table 3: Time of fights measured by ultrasonic in different grades of steel sheets
Coil# Grade Thickness, mm TD,µs T45,µsec T90,µsec Tbar,µ sec
1 IF 0.80 46.38 46.49 49,48 47.21
2 IF 0.90 49.77 46.33 50,00 43.10
3 IF 0.80 49.48 46.17 46,63 47.11
4 DQ 0.97 48.67 47.21 49.85 48.23
5 DQ 0.97 49.07 47.44 49.39 48.46
6 DQ 0.97 49.5 47.68 49.86 48.68
7 DQ 0.97 49.57 47.46 49.83 48.58
8 DQ 1.17 49.37 47.14 49.22 43.21
9 CQ 0.95 48.55 47.41 48.55 48.21
10 CQ 0.71 48.53 47.35 48.53 48.17
11 EOD 0.80 45.63 46.80 45.65 46.22
12 EDD 0.80 48.61 47.19 49.17 48.04
A correlation has been obtained to predict r bar as shown In equation (1) and
Fig, 4. A good correlation has been obtained between the measured r bar ad
ultrasonically predicted r bar.

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WE CLAIM
1. An in-situ method of ultrasonic measurement including correlating of
device features to accurately and quickly predict r-bar in cold rolled and
annealed steel sheets, comprising:
- providing a digital ultrasonic flaw detector, and a computer
controlled pulse receiver;
- providing atleast two probes fixed in a perspex sheet at a fixed
distance;
- measuring ultrasonic time of flights using the atleast two probes
and the flaw detector in the directions 0D, 45° and 90° with respect
to rolling direction in different steel sheets;
- correlating the measured time of flights with the device features of
the steel sheets including the formalcibility bar to establish a
device feature relationship such as:

- non-destructive prediction of r-bar in cold rolled and annealed steel
sheets by application of the established device feature relationship.
2. The method as claimed in claim 1, wherein the device features comprises
composition of the material constituting the steel sheets including its
hardness.
3. The method as claimed in claim 1, wherein magnetostrictive oscillator
technique is used in measurement of r-bar,
4. The method as claimed in claim 1, wherein the atleast two prattles
comprises one each transmitter and receiver.

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5. An in-situ method of ultrasonic measurement including correlating of
device features to accurately and quickly predict r-bar in cold rolled and
annealed steel sheets as substantially described herein with reference to
the accompanying drawings.

PURPOSE:To perform on-line decision of the material characteristics of a steel plate and its anisotropy during traveling by measuring the rate of propagation of elastic wave in the steel plate. CONSTITUTION:AY-cut crystal oscillator is used as a transverse wave transmitter. A radio receiving terminal 1 and a transmitting terminal 2 are made in one piece and are so set that both are located always at a constant distance. The center C of a bar connecting both is aligned roughly to the center of the plate width on the traveling line of a steel plate P, and the bar is made rotatable around the central axis C. Water nozzles 3, 4 are provided in order to acoustically couple a transmitter and a surface to be inspected as well as a receiver and the surface to be inspected. The terminals 1, 2 are turned around the normal axis of the steel plate to measure the rates of propagation in the plural directions within the surface. Usually, the values in the three directions; a rolling direction, a 45 deg. direction and a 90 deg. direction, are measured at constant periods or intermittently. The average rates of propagation of the steel plate or the average modulus of rigidity of the steel plate is calculated from the measured values of the rates of propagation in the respective directions; at the same time, the in-surface anisotropy of the material characteristics of the steel plate is evaluated from the modulus G of rigidity in the respective directions.