Black and bright metal bars

As a producer of black or bright metal bars, you are confronted with customer demands for high quality products – and for good reason, since semi-finished products are often used in safety critical parts for public transport, automobiles, construction, etc.

The NOVAFLUX flux leakage system can help you find cracks reliably and reduce scrap and material expenses effectively. It detects cracks as small as 0.1 mm in depth.


Application fields

  • Production type: very high quality bars and seamless tubes

  • Materials: round black or bright steel (ferromagnetic); rolled, straightened or sand blasted

  • Diameter: 10–140 mm (0.39–5.51 in)

  • Production line: offline (single bars and tubes)


Technical data

  • Inspection speed: up to 3 m/s (9.84 ft/s) depending on the test piece diameter

  • Defect resolution: 0.1 mm or better

  • Defect length: 15 mm or more (0.59 in)

  • Sorting classes: S0 (good), S1 (repairable), S2 (scrap)

  • Display: 8-channel

  • Acoustic emission: 83 dB(A) at 1800 rpm without test piece (distance 1 m).

  • Weight (rotating unit): 600 kg (1323 lb)

Black and bright metal bars

PRUFTECHNIK's comprehensive eddy current inspection system EDDYCHEK 5 has proven invaluable to manufacturers of black and bright bar for reliable quality control. The dual inspection strategy provides excellent identification of both longitudinal and transverse defects. The robust rotating system is extremely sensitive to longitudinal cracks and tears while an encircling coil is used to catch transverse flaws.

PRUFTECHNIK offers a series of rotating systems (RS35HS, RS65, RS130) that cover a wide range of tube diameters. They can be used in conjunction with several of our eddy current inspection systems, depending on individual requirements.

  • Offline inspection: For final quality check after straightening, peeling or polishing using conveyor system

  • Continuous drawing lines: Inline inspection of bars, Ø up to 42 mm (1.65 in)

  • Peeling machines, etc.

  • Bar characteristics: All metals; black and bright bar;  Ø 2–120 mm (0.084¾ in)

  • Inspection equipment: Rotating system for the detection of longitudinal flaws in combination with encircling coil for transverse defects

Product Overview

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Sensitive bar testing with the NOVAFLUX inspection system.

Flux leakage testing

The nondestructive flux leakage testing method reliably detects miniscule cracks on black and bright steel bars, thus guaranteeing highest quality at an affordable price.

The material is magnetized to near saturation. Then sensors move along the material in a circular pattern to detect any flux leakage on its surface. Flux leakage verifies the product quality of black and bright steel bar of diameters up to 200 mm, and its test results can be used to sort and salvage repairable material.

Easy integration with testing equipment already at the plant make NDT’s flux leakage application an attractive solution for producers of high quality of black and bright steel bar.



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Eddy current testing

Eddy current testing is a fully automatic, easy-to-install nondestructive testing method that provides reliable test results to verify product excellence. It uses electromagnetic induction to detect flaws in all metal materials.

Eddy current testing works in multiple environments

One of the most important testing methods used by industry today, eddy current testing provides immediate feedback on product integrity, allowing correction of process changes before scrap develops and delivers reliable test results.

Eddy current testing methods

Full-body inspection / Leakage testing

Full-body inspection using 4 segment coils.
  • Internationally recognized test standards: Leakage testing according to SEP, DIN, ASTM, API, BS, JIS, ETTC, ENEL and others
  • Inspection: Full-body inspection using encircling coils or multiple segment coils. Often combined with weld seam testing
  • Materials tested: Any ferrous, nonferrous or austenitic materials
  • Tube size: Up to 12 in (30.5 cm)
  • Production speeds: 1–20m/min (3.3–656 fpm). Depends on production line and welding type
  • Magnetization: For ferrous tubes

Eddy current testing is an excellent means of ensuring that tubing is leak-proof. Tubes are tested by encircling coils or multiple segment coils that completely surround the tube body. The eddy current test equipment paint-marks critical defects and assigns each tube to a sort class according to its quality. Test results are fully documented for future verification of tube quality.

Rotational testing

Online testing of steel bar with rotating system RS35HS and EDDYCHEK 5
  • Products tested: All seamless products that are round or off-round
  • Production types: Straightening lines, continuous drawing lines, offline final inspection
  • Inspection: Integrated into production line or used in final offline inspection
  • Materials tested: Ferrous, austenitic, nonferrous metals
  • Test piece diameter: 1,9 –140 mm (0.075–5.512 in)


PRÜFTECHNIK's rotating systems are designed specifically to identify longitudinal, homogenous cracks and fissures found at the surface of the test piece. They are used for products that have a tendency to show longitudinal defects but do not have seam welds. Because the encircling coil is ideal for finding short transverse defects, it is often used in conjunction with the rotating system for a comprehensive testing strategy. 

PRÜFTECHNIK offers a series of rotating systems (RS20, RS35HS, RS65, RS140) to cover a wide range of tube diameters. They are particularly easy to operate and maintain and are extremely robust to withstand the industrial environment. Precise test piece guidance and a lift-off compensation system ensure accurate test results.

Eddy current inspection equipment suited for use with the rotating system includes the EDDYCHEK S, EDDYCHEK 5 advanced ROT and the EDDYCHEK 610, depending on the testing capabilities required.

Inline testing

Inline testing
    • Input control: Identification of bad quality material, e.g. rolled wire (drawing lines for thick wire), bar, tube or pipe
    • Quality control: Detection of defective areas in test material and assignment of test piece to a quality category
    • Process control: Monitoring of production lines to avoid scrap, e.g. through transport mechanisms causing periodic defects
    • Final inspection: Assurance of crack-free material
    • Typical defects: Laps, holes, longitudinal cracks, tension cracks from annealing (wire), damage from transport devices (tube, bar, wire), damage through defective drawing lines (wire) or rollers (hot rod)

    Inline testing of tube, bar, and wire takes place in the production line at the time the material is produced. It assures that the material is free of cracks, holes and other material defects or periodic defects as even small surface defects can lead to defective end products, critical in items such as surgical instruments. Eddy current testing is extremely successful in detecting surface defects at various stages during the production process. For the best test results, encircling testing is used together with rotational testing. This testing method is also highly recommendable for hot environments such as hot rolled bar or hot rolled ferrous rod production.

    Offline testing

    Final quality check with encircling coil and magnetizing unit.
    • Offline inspection: Final inspection of cut-to-length tubes, e.g. after drawing to precise diameter (precision tubes)
    • Conveyors: PRÜFTECHNIK also provides conveyor systems for transporting tubes
    • Materials tested: Any ferrous, nonferrous or austenitic materials
    • Magnetization: Required for ferrous metals
    • End-to-end testing: Eddy current sensors are used for distinguishing individual pieces in end-to-end testing

    Tubes are tested offline for a final quality check before delivery. Also, tubes that were sorted to scrap in the course of inline testing during production may be retested offline for more precise classification or for cutting out of defect-free sections. PRÜFTECHNIK supplies complete, customized conveyor systems and testing tables for offline inspection.

    PRÜFTECHNIK offers a wide variety of eddy current inspection equipment that ranges from the most basic testers to powerful inspection systems with wide-reaching capabilites for integration into central production control systems and 8-channel inspection using multiple coil systems.

    End-to-end testing
    The eddy current sensor EDDYSENSOR is used instead of a light barrier to distinguish between individual test pieces in end-to-end testing.

    Butt weld / Seam weld detection

    EDDYSENSOR detects butt welds along steel wire.
    EDDYSENSOR detects weld seams along steel pipes

    Butt weld
    Butt welds cannot be identified by simple detectors such as the light barrier or proximity switch. The EDDYSENSOR locates the butt weld using eddy current testing methods and transmits a signal to the control unit.


    Weld seam
    The EDDYSENSOR eddy current equipment is ideal for detecting a weld seam so that the seam can be positioned where needed for tube-forming processes such as bending.

    Weld seam testing

    Weld seam testing with 2 segment coils.
    • International test standards: Weld seam testing according to SEP, DIN, STM, PI, BS, JIS, ETTC, ENEL, etc.
    • Welding lines: All welding methods such as TIG, laser, HF and ERW welding
    • Materials tested: Ferrous, austenitic, duplex grades, nonferrous aluminum, copper, brass, titanium and german silver
    • Combination inspection: Simultaneous weld seam testing and full-body inspection
    • Line speeds: 0.1–200 m/min (0.3–660 fpm)
    • Tube sizes: 0.5–600 mm (0.2–23½ in)

    Eddy current testing readily identifies flaws in the weld seam regardless of what welding procedure is used. The defects are color-marked and the tube is assigned a sort class according to its quality. Test results are fully documented for future reference.