Republic Steel Corporation

Ltv Steel Company, Inc.

Rupublic Steel Corporation

James M Toth

Richard M Harris

Richard F Abramczyk

Steven J Aron, Jr

Gerald R Coy

Benjamin J Ross

Tyler W Judd

David A Valek

Method and apparatus for performing eddy current flaw inspection on workpiece material such as steel bar stock. A drive mechanism propels a workpiece longitudinally along a workpiece path. An array of electromagnetic transmitter coils is disposed about the workpiece path. An electromagnetic source energizes the transmitter coils under control of multiplexing circuitry. The multiplexing circuitry and source actuate respective transmitter coils in a predetermined iterative sequence. The sequential actuation induces eddy currents in the workpiece at a succession of locations extending iteratively about the workpiece circumference. Circuitry coupled to multiple, differentially wound sensing coils detects variations in eddy current produced in the workpiece and utilizes these detected variations to produce flaw indicating signals.

Electronically scanned eddy current flaw inspection

Method and apparatus for scanning a generally cylindrical workpiece for flaws. A cylindrical metallic sleeve is rotatably supported about a workpiece path of travel. Two differentially wound energization coils surround the sleeve near two apertures in the sleeve. The coils are energized with a high frequency signal that induces eddy currents in the workpiece. The apertures periodically disrupt the eddy current inducing magnetic fields and enhances signals from the coils indicative of the presence of flaws in the workpiece.

Eddy current flaw detector having rotatable field defining sleeve for

An eddy current inspector for imaging of a workpiece shape. A differentially wound test coil mounted next to a workpiece path of travel is energized with a time varying signal to set up eddy currents in the workpiece. A field modifying sleeve is rotated with the field to periodically disrupt the eddy current inducing field. Two signals from the coil, a flaw signal and a shape signal, are time multiplexed and scaled to present a real time image of a workpiece surface as well as the orientation and severity of flaws existing at the workpiece surface.

Method and apparatus for examining a workpiece

A workpiece 18 classifying and marking system 10 is disclosed. The system includes a probe 12 for generating signals in response to the detection of defects along the workpiece length as that workpiece rotates and traverses past the probe 12. Circuitry coupled to the test head analyzes defects according to severity and classifies the workpiece as either 'good', 'salvageable', or 'scrap'. The circuitry also causes a marker 14 to affix a flaw indicating mark to the workpiece at the flaw location. The circuitry includes a flaw detection circuit 60, a defect classifying circuit 72, a timing control circuit 70, and a marker delay circuit 74. The timing control 70 transmits timing signals of different frequency to the defect classifying 72 and marker control 74 circuits and coordinates their operation. The defect classify circuit 72 divides the workpiece into quadrants and can sense the length of any flaws in each quadrant as the workpiece passes the probe 12. The detection of a flaw causes the timing control circuit to resynchronize itself by centering the flaw within a workpiece quadrant thereby preventing the flaw from 'wandering' out of the quadrant. The circuitry is controllable by the user to change workpiece classification as a function of the use to which the workpiece is to be put.

Workpiece defect severity classifier with timing circuit to divide

Method and apparatus for detecting, classifying and marking defects in

An eddy current flaw detection system for inspecting a workpiece for surface flaws is described. The system has a search unit for mounting a pair of eddy current search coils in close proximity to a workpiece at locations which are longitudinally spaced with respect to the workpiece. The system is disclosed in the environment of a workpiece support and transport mechanism which causes a workpiece to rotate and move axially with respect to the search unit. Coil energizing and detection circuitry is provided having a pair of eddy current channels. Each channel energizes a connected one of the search coils to induce eddy currents within a workpiece at slightly different energization frequencies. Each channel has an output for producing signals indicating the presence and severity of detected flaws. The coil energization at different frequencies results in each coil responding to self induced eddy currents rather than currents induced by the other of the two coils. Processing circuitry is provided having a pair of inputs each connected to a respective eddy current channel output. The processing circuitry algebraically multiplies concurrently received eddy current channel output signals to produce a resultant signal. The disclosed signal correlation circuitry will not process a signal from a single coil. Accordingly, the axial separation of the search coils establishes a minimum length of surface flaw which will be detected. The value of the resultant signal indicates the severity of the detected surface flaw.

Eddy current surface flaw detection employing signal correlation

A method for viewing a glowing steel body such as a billet for flaw inspection or identification. The process identification includes the step of providing identifying indicia on a surface of the billet. The billet is viewed by illuminating the billet with a source of bright light to create shadows so that the indicia or flaws can be seen, and viewing the billet from behind a protective device which permits intermittent viewing of the object. Apparatus for carrying out the method includes a shutter by which the light emitted by the billet is attenuated. The shutter employs a pair of rotatable disks having spaced, parallel axes of rotation and the disks are overlapped near their peripheries. Each disk includes a viewing opening disposed near its periphery. When the disks are rotated in the same direction and at different angular speeds, the viewing openings periodically are aligned for short periods of time. The apparatus also includes a pulsed light source having a xenon flash lamp connected across capacitors. The shutter includes a timing mechanism so that the lamp is flashed when the shutter permits viewing of the object.

Method and apparatus for viewing glowing objects

An ultrasonic flaw detector for detecting irregularities in an object, such as a pipe, having a segment of annular cross-section. The detector includes a transducer with an involute transmitting surface for sending ultrasonic signals into the object at equal non-radial angles of incidence. The detector further includes transmission apparatus for maintaining a constant physical relationship between the transducer and the pipe and interpretive apparatus for correlating reflections of ultrasonic signals within the object with irregularities.

Ultrasonic inspection

A method and apparatus for calibrating an eddy current inspection system is disclosed which utilizes electronic workpiece flaw simulator circuitry for simulating a response produced by a flaw in a ferromagnetic calibration workpiece. The inspection system includes a detector probe which generates an electromagnetic field and is responsive to changes in the electromagnetic field. The workpiece flaw simulator circuitry is positioned in the electromagnetic field adjacent the detector probe. The workpiece flaw simulator circuitry controllably alters the electromagnetic field near the detector probe in a manner similar to a change in the field which would result from a workpiece having a defect of known severity passing through the field. In a preferred embodiment, the workpiece flaw simulator circuitry includes a reaction coil and a resistive loading network which are coupled together to produce inductive and resistive components of impedance in the simulator circuitry. The loading network is adjustable to provide differing predetermined loadings on the reaction coil to the electromagnetic field sensed by the detector probe and thus simulate defects of known severity in the type of workpiece under test.

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Lyndhurst, OH, United States of America

James M Toth