DE3321375A1 - Method and device for measuring surface defects on metals - Google Patents

Abstract

A method and a device for measuring surface defects on metals is capable, according to the invention, of simultaneously detecting all the defects regardless of whether they are open or not open to the surface or are pit defects and of detecting the defects regardless of their direction of propagation. At the same time, the defects can be differentiated in terms of their properties. For this purpose, a magnetic field detector measures a resultant magnetic field formed by magnetic fields extending along, and perpendicular to, the surface of a specimen (11). The resultant magnetic field is composed of the stray magnetic field which is due to surface defects and is produced by the component of the resultant magnetic field along the surface of the specimen (11), and of the magnetic field which is due to an eddy current and which is produced on the surface of the specimen (11) by the component perpendicular to the surface. <IMAGE>

Description

VON KREISLER SCHONWALD EISHOLD FUES FROM KREISLER KELLER SELTING WERNER

PATENT LAWYERS
_wl . _t , _T ^, Dr.-Ing. by Kreisler 11973

Sumitomo Metal Industries Ltd.

Dr.-Ing. K. Schönwald, Cologne
15, Kitahama 5 -Chome, Dr.-Ing. KW Eishold, Bad Soden

Dr. J. F. Fues, Cologne

Higashl-Ku Dipl.-Chem. Alek von Kreisler, Cologne

OSAKA, Japan DipL-Chem. Carola tfeller, Cologne

^c Dipl.-Ing. G. Selting, Cologne

Dr. H.-K. Werner, Cologne

DEICHMANNHAUS AT THE MAIN RAILWAY STATION

D-5000 COLOGNE 1

June 13, 1983
Sg-Da / Fe

METHOD AND DEVICE FOR MEASURING
SURFACE DEFECTS ON METALS ■ _

The invention relates to a method and a device for measuring surface imperfections on metals.

For testing the surface of metals for defects
Various non-destructive examinations were carried out, using one or more examination methods according to the expected defects. For example, the magnetic investigation method is used to measure the leakage flux,

which is generated by a surface of an examination object, mainly used to remove the imperfections, such as cracks that were expected to extend reasonably wide in a straight line extend and the eddy current investigation method for

such defects, such as holes, which predominantly extend in the direction of the thickness of the object. The magnetic examination method is fundamentally 1. superior in terms of surface imperfections

ORIGINAL INSPECTED

Telephone: (0221) 13 1041 Telex: 8882307 dopa d Telegram: Dompafent Cologne

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investigation for ferromagnetic metals such as iron and steel products, 2. able to measure an internal defect, even if it does not open to the surface, and 3. able to
to examine the position and length of a flaw on the surface, but it is difficult to detect internal flaws with it. On the other hand, the eddy current examination method is advantageous in that 1. the examination result is directly above

an electrical output signal is obtained, 2. that the non-contact method enables a high examination speed allows, 3. that the method is suitable for measuring surface imperfections and hole imperfections, 4. that the scope is broad, since the sub-

search for defects, changes in the object and changes in dimensions, and 5. that the Signal and the void volume have an approximately proportional relationship, on the other hand this is Method disadvantageous in that 1. this method only

can be used for simple material shapes, 2. that a defect deep below the surface is not is measurable and that 3. the influence of foreign materials outside the examination object often causes disturbances.

The magnetic examination method is effective with magnetization perpendicular to the defect, but it is impossible to measure imperfections if the magnetization is in the same direction as the imperfection runs because a magnetic pole is generated at the defect

and the leakage flux from the surface of the object under investigation is very small. At present, however, the following methods are for the application of several magnetic Fields have become possible to detect the imperfections regardless of their direction. For example

ORJGINAL fMSPPCTED

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becomes a steel rod 1, as shown in Fig. 1, directly axially energized to be circumferentially magnetized. A current flows in a winding that is around the steel rod 1 is wound to axially magnetize the rod 1, so that the circumferential magnetization the Surface imperfections la, which extend circumferentially on the rod 1, detects and the axial magnetization such defects Ib recognizes that extend axially on the surface, which is known.

Furthermore, a known investigation method is shown in Fig. 2, which requires two windings 2, 2, which ^{surround a tube I 1} , and a magnet 3, which has opposite magnetic poles on both sides in a diametrical direction in relation to the tube 1 '. The windings 2, 2 and the magnet 3 are arranged in series so that the windings 2, 2, the tube 1 'axially magnetize to thereby detect a circumferential surface flaw 1'b in the magnetic field using a magnetic field detector 2a and the Magnet 3 magnetizes the tube 1 'circumferentially in order to thereby detect an axial surface defect 1'a in the magnetic field by means of a magnetic field detector 3a.

The surface flaws on the metallic object can be both hole flaws and crack flaws The hole defects are difficult to detect by the aforementioned magnetic inspection method are. Therefore, the measurement of the hole defects should, if necessary, with the eddy current investigation method be carried out, whereby the measurement of the crack-like defects with the magnetic particle measurement (magnetic powder) is carried out with high measuring performance. This resulted in the disadvantage that a Variety of examination methods according to Art

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ORIGINAL INSPECTED BAD ORIGINAL

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Surface imperfections of various types on an examination object with a round cross-section on the To measure circumference and length,

the surface imperfections of various types
to scan and measure at high speed an object with a flat plane surface, such as a steel bar with a rectangular cross-section, and

the surface imperfections of various types
To scan and measure an object with a flat, even surface, such as a steel rod, at high speed and to distinguish the properties of the detected defects.

Such examination methods differ from conventional ones in the application of several magnetic fields according to Fig. 1. The specialty is the detection of defects by the resulting magnetic field, the encloses the magnetic field perpendicular to the surface of the examination object, whereby the defect detection is made possible regardless of the direction and configuration of the defect.

In the following, exemplary embodiments of the invention are explained in more detail with reference to the drawings.

Show it:

Figs. 1 and 2 a schematic representation of the

conventional flaw measuring method using several magnetic fields,

ORIGINAL INSPECTED

332137!

Fig. 3 is a schematic representation of the principle of

Defect measuring method according to the invention 4 shows a side view of an exemplary embodiment with a combination of a magnetic field generator with a magnetic field detector, Fig. 5 is a block diagram of the magnetic field generator

and the detector circuit, Fig. 6 the representation of the rotating magnetic field in a diagram,
7 shows a schematic illustration for explanation

the relationship between the rotating magnetic field and the type of defect, 8 is a block diagram of a modified embodiment of the magnetic field generator "and the detector circuit, FIG. 9 is a side view of a measuring device

for steel tubes,
FIG. 10 shows a schematic representation of an exemplary embodiment for square steels, FIG. 11 shows a side view of an exemplary embodiment

according to Fig. 10,

FIG. 12 shows an enlarged detail from FIG. 11, FIG. 13 shows a section along the line XIII-XIII in FIG. 12,
14 is a schematic representation of a

Exemplary embodiment for steel tubes, FIGS. 15 and 16 are a side view and a

Cross section through the embodiment according to FIG. 14,
Fig. 17 is an explanation of the magnetic field in the

Exemplary embodiment according to FIG. 14, FIG. 18 shows a partially cut-out side view

of an embodiment according to FIG. 14, FIG. 19 shows a longitudinal section through the Embodiment according to FIGS. 14 and

ORIGINAL INSPECTED

Fig. 20 is a block diagram of the electrical

Circuit of the embodiment according to FIG. 14th

With reference to Fig. 3, the invention is essentially characterized in that the opposite Magnetic field generators 12, 12 arranged relative to one another and on both sides of an examination subject 11 generate a magnetic field running parallel to the surface of the object 11, and that at the upper and lower

side oppositely arranged magnetic field generators 13,13 a standing perpendicular to the first magnetic field generate a second magnetic field, so that a magnetic field detector 14 (not shown in Fig. 3, but in Fig. 4), which is arranged above the surface of the object 11, which is located in the aforementioned magnetic fields Measures the magnetic field generated by imperfections.

The magnetic field generators 12, 12 generate the magnetic field, as in the conventional magnetic defect examination and measure the leakage flux in

the part where a magnetic flux is generated 12a intersecting defect 11a exists. The magnetic field generators 12 can generate a direct current field, it but it is advantageous, as described below, to provide the magnetic field generator with an alternating current magnetic field so that a rotating magnetic field is used for the material location to be examined thereby to carry out the defect investigation, which does not include defects that are in the depth of the Object 11 extend, is influenced.

On the other hand, the magnetic field generators 13, 13 generate the alternating current magnetic field to generate an eddy current 13a the surface of the examination subject 11 to induce

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BAD ORIGINAL ORIGINAL INSPECTED ■

Generate IeI to the surface of the object 11. The magnetic field generator 13 consists of a bobbin 13b which is smaller in its length to be traversed by an alternating current as the free limbs of the iron core 12b and a coil 13c wound on the coil core 13b _r. It is arranged in the middle between the free legs of the generator 12 in order to thereby generate a magnetic field perpendicular to the object 11. The magnetic field detector 14 is arranged on the end face facing the object 11 on the magnetic pole of the coil core 13b and is directly opposite the surface of the object 11. Therefore, the magnetic fields on the part of the surface of the object 11 opposite the magnetic field detector 14 are parallel and generated perpendicular to the surface of the object 11, whereby the inspection of flaws is made possible according to the aforementioned principle.

In the following an electrical circuit will be explained, which with the magnetic field generators 12 and 13 and the Magnetic field detector 14 is connected as shown in FIG. In Fig. 5 is an embodiment of the electrical Circuit shown. Here, the magnetic field generators 12 and 13 both generate the alternating current magnetic fields. In detail, the oscillators 21 and 22 each generate a sinusoidal oscillation with an angular frequency ω, and their output signals are passed to each winding 12c or 13c of the magnetic field generators 12 and 13, respectively in each case an amplifier 23 or 24 is supplied to generate the magnetic field, an output signal of the Magnetic field detector 14 is supplied to the sample and hold circuits 25 and 26, respectively. The sample and hold circuits 25 and 26 also receive the output signals of the oscillators 21 and 22, respectively, in order to generate the output signal of the magnetic field detector 14 in synchronization with

sample and hold the phase of each output signal. The output signals of the sample and hold circuit 25 and 26 are recorded on recording units 27 and 28, then supplied to comparators 29 and 30 and compared with a preset comparison reference value there in each case so that when the output signal is greater than the reference value, the predetermined signal generated as in the flaw measurement is and counted by flaw counters 31 and 32

will. The flaw counters 31 and 32 are connected to the output terminals of the comparators 29 and 30 are connected, and Markxervorrichtungen 33 and 34 are connected by the comparators controlled to apply color markings to the places where the defect was discovered. There the magnetic field generators 12 and 13, the magnetic field detector 14 and the examination subject 11 relative to one another are moved, the marker devices 33 and 34, as in the conventional devices, in the correct Time controlled at which the body that the

Defect includes emerging from the detection zone of the magnetic field detector 14 after the defect measurement removed.

The oscillators 21 and 22 are driven synchronously to enable their oscillator output signals

have a predetermined phase shift between them. Assuming the two oscillator output signals differ by a phase shift of 90 °, the output signal of the oscillator 21 is represented by sin ω t, while the output

signal of the oscillator 22 represented by cos ω t is, whereby in the case where the sample and hold circuits 25 and 26 the sampling with the clock for Record the peak values of the output signals sin ω t and cos ω t of the oscillators 21 and 22, respectively

Evidence of defects can be carried out with the highest level of sensitivity. In other words: when considering the circuit half which contains the oscillator 21, the leakage flux from a defect through a high one
Signal-to-noise ratio measured in accordance with the clock for the strongest magnetic field, with the result that the crack defect detection signal (a defect parallel to the flux 12a is not detectable) of the magnetic field due to the magnetic field generator 12
is counted by the flaw counter 31, the marking device 33 applying the marking in accordance with the counted value.

Similar to before, on the circuit half of the oscillator 22 in the case where the magnetis seen by the Field, which is formed by the magnetic field generator 13, generated eddy currents through the defect is disturbed, the turbulent magnetic field is matched by a high signal-to-noise ratio measured at the time of the highest turbulence of the magnetic field and the result of the measurement becomes counted by the defect counter 32 and identified by the marking device 34. The oscillator 22 detects the turbulence of the field caused by the eddy current, so that crack defects in

different directions as well as hole-shaped defects can be detected, thereby at least the To enable differentiation of defective cracks, the cross the magnetic flux 12a generated from other voids. With the output signals of the

Sample and hold circuits 25 and 26 (the recorded contents in the recorders 27 and 28) can be further detailed taking into account the information from the defects existing in the object 11 Differentiations are carried out.

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BATH ORIGINAL

ORIGINAL INSPECTED

fen when the inclined defect according to FIG. 7c has presumably been traced. The sample storage is then carried out in accordance with the times for ω t = ir / 4 and 5 -rr / 4, where such
Defects can be detected through a high signal-to-noise ratio.

The output signal of the magnetic field detector 14 is in Connection with the phases of the magnetic fields generated by the magnetic field generators 12 and 13, whereby the imperfections of different shapes in terms of their in-depth cross-section can be tracked down and the shapes can also be differentiated by the sampling time

is changed.

The phase difference between the output signals of the oscillators 21 and 22 is not limited to 90 °, but can be set as required.

The intensity of the magnetic field is the same in any angular direction when the phase difference is set at an angle of 90 ° or 270 °, but it can be increased in a certain direction at an angle other than the above, it being preferable to decide that the phase difference that the
Corresponds to the cross-sectional shape of the flaw, measured in the direction of the depth of the flaw.

Fig. 8 shows a block diagram of another embodiment of the flaw measuring device, in which an oscillator 41 with the angular frequency ω the one
generated magnetic field and an oscillator 42 with the angular frequency mω the other magnetic field. In one

The output signal sin ω t of the one oscillator 41 is individually supplied to the amplifier 43 and thereby amplified in order to be supplied to the winding 12c of the magnetic field generator 12, whereby the magnetic field is parallel
to the surface of the test object 11 is formed. The output signal sin m ω t of the other oscillator 42 is fed to the power amplifier 44 and thereby amplified to be fed to the winding 13c of the magnetic field generator 13, whereby the for

Surface of the object 11 perpendicular magnetic flux is formed. The output signals of both oscillators only need to be different with regard to their frequency (m ^ l), whereby the value of m is not a definite one must be, but preferably a value of

two or greater because of the different roles played by the frequencies in distinguishing the signal components should have on the basis of the two magnetic fields.

The output signal of the magnetic field detector 14 is sent to the synchronous detectors 47 and 48 via the amplification

ker 45 and 46, the synchronous detectors 47 and 48, the output signals from the oscillators 41 or 42 have received in order to thereby the phase detection, based on the oscillation output signals of the oscillators, to execute. Therefore, the leakage flux caused by

the defects caused in the magnetic field generated by the magnetic field generator 12, retrieved by the synchronous detector 47 and the turbulence generated by the defect in the magnetic field generated by the generator 13 is caused by the synchronous detector

30. 48 retrieved so that the output signals of the synchronous detectors 47 and 48 are entered in comparators 49 and 50 and compared with the comparison reference value which is specified therein. The output signals are, if they are greater than the reference

ORiGINAL INSPECTED

The limit value is also counted separately by defect counters 51 and 52, as in the case of the defect measurement, and marked by a common marking device 53, the marking device of course also being separate
can be provided.

In this way the frequency becomes magnetization chosen differently in order to enable the detection of defects in connection with each magnetic field, whereby as Result the differentiation of the type of defect is possible. It is also possible, because of the different frequencies, to generate the rotating magnetic field by oscillation in connection with each phase, whereby the defect detection can be carried out regardless of the cross-sectional shape of the defect in the direction of its depth.

Fig. 9 shows an apparatus in which a tube 11 to be examined extends in the longitudinal direction of the apparatus is moved and rotates around its axis. On both sides of the area in which the object 11 moves are the magnetic poles of the magnetic field

generator 12, which is carried by slide parts 35, 35 and which is magnetically coupled via a yoke 12, arranged opposite to each other. The windings 12c, 12c at the poles are of a (not shown) Power source supplied to the magnetic field

form. A larger part of the magnetic flux of these windings goes through the object 11, which is so arranged it must be that it differs from the circumferential Magnetic field is penetrated evenly. The carriage parts 35,35 are based on a rail 36 on their

both longitudinally extending sides and are freely movable in the longitudinal direction on the rail 36, wherein the rail 36 is arranged horizontally and perpendicular to the direction of movement of the object 11. A feed

'' 33213

winding spindle 37 is arranged below the rail 36 and parallel to it and has at both ends oppositely turned threads, with nuts 38,38 running on the screw turns, which are attached to the Slide parts 35,35 are each attached so that a hand wheel 39 attached to one end of the lead screw 37, clockwise or counterclockwise is rotated around the poles on the magnetic field generator 12 towards the object 11 or from the object 11

dare to move to the same extent. Above the range of motion of the object 11, an air cylinder 40 is mounted, which is directed downwards and which is on its lower end accommodates the magnetic field generator 13 and the magnetic field detector 14, which in combination, such as shown in Fig. 4, are arranged. The magnetic field generator 13 forms a radial in relation to the object 11 Magnetic field, whereby the parallel to the surface of the object 11 and the perpendicular to it Magnetic field just below the magnetic field

Tektors 14 are generated, in this way the aforementioned defect detection is made possible. Of the Air cylinder 40 is controlled to position the magnetic field generator 13 and the detector 14 align and the feed screw 37 is

rotates to align the magnetic field generator 12 in position, thereby adjusting the device to allow objects of different diameters to be examined.

Fig. 10 shows a device for the detection of
Defects in an object 11, which is designed in cross section as a square, such as steel bars or square steel, is used. In general, when the magnetic field generators are assembled with the detector as shown in Fig. 4, perpendicular to the

ORIGINAL INSPECTED

The direction of conveyance of the object 11 is moved during the conveyance, the object surface is on examined a zigzag course. However, such a combination is difficult because of the iron core, which makes the movement device must be dimensioned accordingly large and which makes it difficult to do this quickly to move, so that there is the disadvantage that the examination speed is slow. The device from Fig. 10 has eliminated this disadvantage.

The device is constructed in such a way that a magnetic field generator 12, in which the magnetic poles are opposite to each other on either side of the conveyance area of the object 11 are arranged, the magnetic field parallel to the surface, which with respect to

the defects to be examined is generated. A magnetic field generator 13 opposite the surface, which is to be examined is arranged, and consists of a substantially rectangular air core winding, whose inner dimension is greater than the width of the

Examination area, generates the magnetic field perpendicular to it. A magnetic field detector 14, the inside the winding of the generator 13 is arranged, is in the direction of the width of the object 11 back and forth emotional. In a few words, the magnetic field generators 12 and 13 are stationary while only the lightweight detector 14 is moved.

In the following, the aforementioned device is illustrated with the aid of FIGS. 11 and 12 explained.

On both sides of the range of motion of the object 11, which is rectangular in cross section, in the longitudinal direction must be transported for the inspection of defects, is a magnetic field generator 12 for generating the magnetic

field along the surface (upper surface) of the examination subject 11 is provided. The generator 12 has cores 12d, 12d on which the windings 12c, 12c are wound, as well as a yoke 12e below the object 11 and extending in the width direction thereof, the cores 12d, 12d being partially movable the yoke 12e are each supported via the support plates 61,61.

The movable bearing surfaces 62 are at the lower end
of the support plates 61,61 mounted, the threaded nuts

63,63 are mounted on the lower surfaces of the bearing surfaces 62,62 and the worm with the threaded parts at both ends of a threaded spindle 64 bridges the object 11 in width and points in each case
opposed threads so that the spindle 64 must rotate clockwise or counterclockwise to slide each of the cores 12d on the yoke 12e in the width direction of the object 11, with the cores 12d toward the object
or move away from the object.

A magnetic field generator 13 for generating a magnetic field perpendicular to the surface of the examination subject 11 is located above the surface and uses an air core winding that consists of an elliptical view Coil hollow body 13d, which extends in the width direction of the object 11, as well as a winding 13c, which is wound on the bobbin 13d, with the air core coil on the upper Surface of both ends is mounted on the lower surface of a U-shaped mounting part 65,65, respectively, and the mounting parts 65,65 on the upper surface on the lower surface of a support plate 66 of a follow-up mechanism is mounted. A cylinder support plate

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6 7 is provided on the support plate 66 of the follow-up mechanism and carries on the upper surface a cylinder 68, the piston rod 69 of which protrudes downwards. The piston rod 69 is through the cylinder support plate
67 guided and at the outer end carries the follow-up mechanism 66 via a universal connection 70 in its upper center, thereby allowing the support plate 66 to move freely and obliquely in relation to the piston rod 69, the support plate 66 of the

Successor mechanism has roles not shown on their underside. These are on side panels attached, which are arranged in the transport direction of the object 11 front and rear. The roles are on provided both broad sides of the object 11 to come into rotating contact with the object and its Curvature to follow.

On the underside of the support plate 66 is at one end transverse to the object -11 via an L-shaped attachment 72 a motor 71 is mounted. An output shaft 71a of the mo-

gate 71 extends inward and is at its outer end with a threaded rod 74 coaxially across a coupling 73 connected, the threaded rod 74 at both ends in the mounting parts 65,65 over Bearing is mounted so that it is clockwise

direction or opposite according to the rotation of the motor 71 can rotate. The threaded rod 74 is also passed through the upper part of a detector housing 75 and engages therein in a threaded nut, so that the housing 75 on the threaded rod 74 transversely to the object 11 of the rotational movement in the clockwise direction or opposite to the threaded rod 74 is moved following.

13 shows a section along the line XIII-XIII

ORIGINAL INSPECTED

'in'-' Pig. 12. The lower part of the housing 75 is arranged in a cavity of the bobbin 13d of the magnetic field device 13 and guide rollers 76, 7 * 6 rotatably in contact-with the-upper surface of the bobbin
13d ^{are in:} relation to the direction of movement on both sides of the housing 75 mounted so that they 13d move rotationally in contact "with the spool body when the housing 75 is moving and also a rotational movement äes'Gehäuses 75, caused by the rotation the business

prevent wiridestange 74. ~ The housing 75 is on the

- '■' ■ floor area open. By ^; this opening is the upper end ^; 14 a receiving detector holder 77 inserted slidably in the magnetic field detector, the housing 75, £ ^r n ^which: "is arranged a compression spring 82" to the holder ¥? ⁿ next ^: below ^; to press. The magnetic field detector 14 is "the Detektbrhälters deim ^ lower end" 77 inserted titnS ^ äuf ^ the üritersuehungsoberfläche downward ^J \ in "toward the object 11), -wherein the Detekfeorhältefan the lower end a carrying shoe 78 ϊή so that the investigation surface of the detector 14 -'over the shoe '78 with. the examined surface of the object'- ^J ll ίή contact- '. ^{r ::} '.-j.:>: - ~.: - i

You ^{: i} Öewirid: estange 74- ■ '"is rotatably mounted at the end facing away from the mounting side" of the motor-7ί on a mounting part 65 via a bearing and connected via a coupling 73 with - ° eifiem ^: position detector ■ 80 *, the one

'-'- ■ Potentiometer or' a rotary encoder is used. The Pösitiönsde-tektof '80 is attached to the support plate 66 of the PfäöRfolgemechanIsmus via an L-shaped attachment 72, so that the movement of the magnetic field detector i "4 -" due to -der Drehurig ^r -der thread rod 74 in Ührrieigefrichtung "or vice versa the PositiOnsäetektor ^ SO in the direction ^; transversely "to the object 11 is measured. In addition, "kennaei'chriet the reference drawing ° 81: in Pig-. 12

ORIGINAL INSPECTED BAD ORIGINAL

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Line cables to carry the signal between the magnetic field detector 14 and the signal processor.

The mode of operation of such a device is explained in more detail below. In Fig. 11, the lead screw 64 first rotated in order to establish a distance between the cores 12d, 12d on the magnetic field generator 12, which corresponds to the width of the transported object 11. Then the piston rod 69 is on the cylinder 68 withdrawn to move the magnetic field generator 13 and detector 14 to a safe area above the conveyance area of the object 11 to bring. Then the magnetic field generators 12 and 13 with Powered. In this state, the object 11 is inserted. Then by a detector, for example through a photoelectric tube, the entry of the object 11 into the defect detection zone is detected and the piston rod 69 on the cylinder 68 is moved forward until the shoe 78 is on the detector holder 77 against the examination surface of the object 11

bumps. The motor 71 is controlled to rotate the threaded rod 74, so that the housing 75, which the Detector holder 77 carries, is moved in the air core part of the bobbin 13d transversely to the object 11 and the Shoe 78 slides on the examination surface with Contact moves. Here, the magnetic field detector 14 detects the superimposed magnetic field that is in the vicinity the examination surface of the object 11 is generated in order to carry out the defect detection on the examination object.

With regard to the movement of the housing 75, i.a. Magnetic field detector 14 and other carries at a predetermined distance, the motor 71 can turn in reverse Turn the direction of rotation to move the housing 75 back.

ORIGJNAL INSPECTED ^

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because. In this way, the housing 75 will zigzag up within a predetermined width of the examination surface of the advancing object 11 is moved, the predetermined width correspondingly the width of the object 11 is determined.

The guide rollers 76, which are mounted on both sides of the housing 75, rotate on the top surface of the bobbin 13d due to contact with it, thereby facilitating the movement of the housing 75 and to prevent the housing 75 from rotating together with the lead screw 74.

In addition, rollers are not shown on both sides of the magnetic field generator 13 in relation to Direction of movement on the support plate 66 of the successor

mechanism mounted that is in contact with the rotatable The examination surface of the object 11, the support plate 66 being inclined via a universal connection 70 is freely movable, so that the detector holder 77 can follow a curvature of the object 11. Furthermore

the detector holder 77, since it is pressed downward by the compression spring 82, follows the unevenness of the examination surface, so that damage to the holder need not be feared.

In the following another embodiment will be explained, which is able to remove various imperfections Type to be examined over the entire circumference and the entire length of an object with a round cross-section.

Fig. 14 is a perspective view of this embodiment and Figs. 15 and 16 are more
Representations of it. A ring-shaped electromagnet 4 for generating a concentric with the examination object

ORIGINAL INSPECTED

tric alternating current magnetic field is within the transfer zone of the object (steel tube), which is in the longitudinal direction is conveyed, arranged. The electromagnet 4 has four magnetic poles 4a and 4a on its inner circumference 4b with mutual angular spacing of 90 °, the opposing poles 4a, 4a by windings 6a, 6a and the other opposite poles 4b, 4b each formed by the windings 6b, 6b will. An alternating current ia = Im sin ω t flows through the windings 6a, 6a at the poles 4a, 4a as an excitation current and an excitation current ia = Im cos ω t, which differs from the first excitation current in phase by ττ / 2, flows through the windings 6b, 6b at the poles 4b, 4b. This means that vertically crossing magnetic "fields" are created generated, the intensity of which Ha and Hb changes with time. Hence the composite magnetic field changes of both fields its orientation over time by following the change in intensity of both fields. In In other words: In the center of the ring-shaped electromagnets, the field intensity Hc is due to the alternating current phase shift constant and the rotating magnetic field with the rotational speed ω t is formed. In a few words, assuming that the virtual magnetic poles rotate, the eddy current continues generating Position away from the rotating magnetic field their rotation. The opposite to the outer circumference of the object 11 arranged magnetic field detector 14 measures the turbulence of the magnetic field · if a defect exists, whereby the defect is detected. on the other hand

it is assumed that the object 11 is circumferentially magnetized by the opposite poles 4a, 4a or 4b, 4b or the virtual magnetic poles so that the voids in the direction of the flow and on the other hand perpendicular to the circumferential direction proven by the leakage flux due to the imperfections

ne ti see poles 4a and 4b gevrie.'celt. Sfcütz

Discs 94 and 95, each at its center

säSSibHP? ί & ϊ-ΏφίλΙ wß & ^ §a &'§ £ & £ r%) - * Flux 5a circumferentially to generate a magnetic field in the longitudinal direction of the object

EY8 ^r f9! £ SfecYi ^e 9 $ § ⁿ is en one axial end of the cylindrical 'part 93 et; -; a in the axial center

d _r

25th t8§iei4gi

The Bs drawing symbol Θ denotes the orientation of the virtual pole

OR ₁₀ JNAL, NSPECTH ₃ ^ BADORIGINAL ^

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- -25 -

11 in its edge area, the stray field caused by the imperfections from the circumferential magnetic field 40a, which is generated by the ring-shaped electromagnet 4, and the axial magnetic field 5a, the
is generated by the ring-shaped magnet coils 5.5. In a case where there is a hole-like defect, the detector 14 measures the turbulence of the magnetic field caused by the turbulent eddy current due to the defect, thereby detecting the defects. The magnetic field detector 14 is rotated at a lower speed than the speed of rotation of the magnetic field, so that the phase position of its position coincides with that of the virtual pole of the rotating magnetic field. The magnetic field de-

detector 14 scans the outer periphery of the object 11 spirally in connection with the forward movement of the object 11, whereby a precise inspection of the flaws over the outer circumferential surface of the object 11 is carried out.

FIG. 18 is a partially cut-out front view of a concrete embodiment, and FIG. 19 is a longitudinal section thereof, in which a cylindrical drum 91 in the transfer zone of the object, which is in the longitudinal direction is moved further, is mounted on a plate 92 concentric with the object 11. The drum 91 has in the middle on the inside of its circumference an annular electromagnet 4, which is concentric is mounted to the drum 91 via angle plates 93 on her. On the upper and lower and the right one and the left part of the ring-shaped electromagnet 4 are two pairs of magnetic poles 4a and 4b radially inward, so that the two magnetic fluxes in the center of the electromagnet 4 are perpendicular cross. The windings 6a and 6b are respectively

ORIGINAL INSPECTED

■ ·· "· ■ '332137

wound on the magnetic poles 4a and 4b. Support disks 94 and 95, each in its center a have concentric with the drum 91 through hole, are each on both end faces of the drum 91 attached. Annular magnet coils 5.5 are each concentric on the outer side surfaces of the support disks 94 and 95 mounted.

A disk-like mounting plate 96 has a round concentric with the drum 91 in its center

Hole on and is on the inner peripheral surface of the Drum 91 fixed between the ring-shaped magnet and the support disc 94. The circular borehole takes a cylindrical part 98 rotatably approximately in its axial center via a bearing 97, so that the object 11 is moved within the cylindrical part 98. A flange 98a is at one axial end of the cylindrical part 98 approximately in the axial center of the drum 91. On the outer peripheral surface of the cylindrical Part 98 on the direction of movement of the

A belt pulley 101 is mounted on the side facing away from the object 11. A timing belt 103 is through a recess, not shown, on a pulley 101 and a pulley 102, which on a Output shaft of a laterally arranged motor 100

is mounted, guided so that the rotary movement of the motor 100 on the cylindrical part 98 via the pulley 102, the timing belt 103 and the pulley 101 is transmitted, thereby the cylindrical part 98 is rotated.

At two diametrically opposite symmetrical positions on the outer end surface of the flange 98a on cylindrical part 98 are sensor holders 105, 105, in which magnetic field detectors 14 are located, radially

ORiGJNAL INSPECTED

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332137E

movable via connecting mechanisms 10 4,104 assembled. The connecting mechanisms 104, 104 each have a leaf spring 106, 106 around each sensor holder 105.105 to press radially inwards.

A slip ring 107 is fixed between the flange 98a and the mounting plate 96, and a grinding brush 108 in grinding contact with the slip ring 107 is mounted on the mounting plate 96 via a connector 109 so that a signal "from a magnetic field detector
14 in the respective sensor holders .105 via the slip ring 107 and the grinding brush 108 from the device to the outside.

Fig. 20 shows, by way of example, a block diagram of an electrical circuit for the above device. In

In this drawing, the windings 6a, 6b are wound on the magnetic poles 4a and 4b on the annular electromagnet 4 and receive the alternating currents
Im sin _ω t and Im cos ω t, which differ in their phase by ir / 2, and which are each generated by an oscillator 111 via power amplifier 112. The rotating magnetic field, which changes its orientation over time, is formed in the central part of the ring-shaped electromagnet 4. The ring-shaped magnetic coils 5, 5 receive a direct current which is supplied from a direct current source and which is amplified by a power amplifier 114, whereby the axial magnetic field is generated on the outer surface of the object 11. The excitation current for each ring-shaped solenoid 5 is not of direct current

limited, but can also be alternating current.

The magnetic field detectors 14,14, which are in the sensor holders 105 are located, measure the leakage magnetic field, the

332137

is generated by the crack-like defects located on the outer surface of the object 11, and which extend in circumferential and axial directions, as well as the turbulence of the magnetic field that causes
is when the eddy current induced by the rotating magnetic field is disturbed by hole-like surface defects or other defects that are present on the outer peripheral surface of the object 11, so that each measurement signal is transmitted to each amplifier 115

the grinding brushes 108 and the slip ring 107 is supplied and amplified with the amplifier 115 and thereafter supplied to a comparator 116 which receives an output of each amplifier, i.e., an output of each magnetic field detector 14 compares. If "the difference between the two signals is so great that the one detector 14 determines the existence of a disadvantageous defect, the marker 117 carries a Marking at the location of the defect, the output signal of each amplifier 115 being a recording

Processing device 118 is supplied so that the measurement signal from each detector 14 is recorded there.

In a device constructed in this way, the motor 100 is controlled to drive the cylindrical member 98 to rotate within the drum 91 while the object

11 is moved forward. Then each sensor holder 105 lies with its lower surface on the outer one Circumferential surface of the object 11 and moves in context with the rotation of the cylindrical part 98 and the forward movement of the object 11 in a spiral

on this, making the surface imperfection inspection is carried out. In this case, each sensor holder 105 lies, since each of theirs lies radially on the Object 11 is pressed via the leaf spring 106, exactly on the outer surface of the object 11 in order to

OR (GINAL fNSPECTED

332137;

by reliably following the small vibrations or curvatures of the object 11.

The number of the magnetic field detectors in the aforementioned embodiment may be one or more
be.

The output of each magnetic field detector 14 does not depend on the mutual comparison of the comparators en 116, but the comparators can carry out the detection of existing defects in the in a comparison reference value is established for each.

ORiGJNAL iNSPECTED

ORIGINAL INSPECTED

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Claims (11)

EXPECTATIONS 1. ) Procedure for measuring surface imperfections
Metals, characterized in that
a resulting magnetic field, which is formed by magnetic fields that run along and perpendicular to the surface of an object to be examined (11), that a magnetic field detector (14) measures the resulting magnetic field that is generated from the stray magnetic field due to the surface imperfections caused by the component of the resulting magnetic field is obtained along the surface of the examination object (11), and the magnetic field is due to an eddy current which is obtained on the surface of the examination object (11) through the component perpendicular to the surface. 2. The method according to claim 1, characterized in that the corresponding to the resulting magnetic field The varying measurement signal of the magnetic field detector (14) is broken down into the components of each of the two Magnetic fields, whereby the surface imperfections are evaluated. 3. The method according to claim 2, characterized in that the resulting magnetic field of several alternating currents is generated, each of these alternating currents in a mutually determined phase relationship flows. copy 4. The method according to claim 2, characterized in that the resulting magnetic field of several alternating currents different frequency is generated. 5. Procedure for measuring surface imperfections Metals, characterized in that the alternating current magnet field in the radial directions of an im Cross-section of a round object to be examined (11) is generated is to form a rotating magnetic field and that also in the axial direction of the examination subject (11) a magnetic field is formed, so that the magnetic fields and the magnetic field that affects the Surface imperfections of the examination subject (11) is measured by a magnetic field detector (14) that surrounds the object to be examined rotates. 6. Device for measuring surface points on metals characterized by the following parts: a first magnetic field generator (12) which generates a magnetic field along the surface of the examination subject (11), a second magnetic field generator (13) which generates a magnetic field perpendicular to the surface of the examination subject (11) generated, a magnetic field detector (14), which is arranged in both magnetic fields crossing at right angles and which measures the magnetic field perpendicular to the surface of the examination object, and a signal processing circuit for decomposing the output signal of the magnetic field detector (14) into the components of the magnetic fields generated by the first and second magnetic field generators (12) and (13) be generated. 7. Apparatus according to claim 6 _f, characterized in that the first and second magnetic field generators (12,13) have oscillators (21,22) whose oscillation phases are different from one another. 8. Apparatus according to claim 6, characterized in that the first and second magnetic field generators (12,13) have oscillators (41,42) which differ in their oscillation frequency. 9. Device for measuring surface imperfections on metals, characterized in that first magnetic field generators (12) are arranged on both sides transversely to the examination subject, which in his Is moved longitudinally, the magnetic field along the surface to be examined of the object to be examined (11), is formed that a second magnetic field generator (13) opposite the examination surface is arranged, wherein the second generator (13) is hollow on the inside and is transverse to the examination subject extends, thereby forming a magnetic field perpendicular to the examination surface that a magnetic field detector (14) in the hollowed out part on the second magnetic field generator (13) and measures the resultant magnetic field obtained from each of the magnetic fields and from the stray magnetic field due to the surface imperfections on the examination surface and the magnetic field is due to an eddy current on the examination surface, whereby the magnetic field detector is moved back and forth in the transverse direction of the object in order to scan the examination surface. 10. Device for measuring surface imperfections Metals, characterized in that a first magnetic field generator on both sides of an examination object, which is moved in its longitudinal direction, is arranged, creating a magnetic field along the examination surface is generated on the examination subject (11) that a second magnetic field generator (13) is arranged opposite the examination surface, with the second generator (13) inside is hollow and extends in the transverse direction of the examination subject, creating a magnetic field is formed perpendicular to the examination surface that in the hollow part of the second magnetic field generator a magnetic field detector (14) is arranged, which detects the resulting magnetic field from the surface imperfections stray magnetic field caused by each of the magnetic fields is obtained, and from the magnetic field created by eddy currents on the examination surface measures, the magnetic field detector moving back and forth in the transverse direction of the examination subject is to scan the examination surface and that a signal processing circuit the output signal of the magnetic field detector (14) into the components of the first and second magnetic field generators generated magnetic fields. 11. The device according to claim 10, characterized
characterized in that the first and second magnetic field generators have oscillators (21,22) whose oscillation phases differ from one another. .W- ^{:: f:} 332137s * mn n with L e on on d dift ⁿ tei fSaff ^e oa? ^ _:! ^ ines 4a "fine ■ _f XJ? ^ _ς ^. ro tier it ^ u ^ t.as. _T < , .. to measure sagged magnetic field. - -?.-..., -., -., - ■ .- .. Method nachteiiia. 5. ^ iu; "c ^: i that 1, this i-.". da £ eiae ^. ^versenen , which are connected to this core and are diametrically symmetrical, v.'ir-d, '..vr.ä - ^ r- the i ^ y ^ rfläv ^ e of the un- ^ r- :; orclcvi _g