Cold Heading Wire with In-Line Eddy Current Testing
stainless steel cold heading wire
,cold heading wire eddy current tested
,in-line eddy current testing wire
Cold Heading Wire with In-Line Eddy Current Testing
Product Introduction
A cold header converts surface defects into broken tooling. A seam that runs along the wire opens into a crack at the first blow, and a sliver rolls into the head as a lap. Both cost more at your press than at our drawing line, which is why this wire is inspected over its full length before packing.
In-line eddy current testing with an encircling coil detects surface and near-surface discontinuities continuously as the wire leaves the final draw. Defects are marked, and the marked length is either cut out or flagged on the coil tag, according to your acceptance criteria.
Available from 0.15 mm to 12 mm, grades 302, 304, 304Cu, 316L, 410 and 430.
Product Specifications
| Parameter | Specification |
|---|---|
| Grade | 302, 304, 304Cu, 316L, 410, 430 |
| Diameter Range | 0.15–12 mm |
| Diameter Tolerance | ±0.02 mm up to 2.0 mm; ±0.03 mm above 2.0 mm |
| Test Method | Eddy current, encircling coil, in line after final draw |
| Coverage | 100% of coil length |
| Reference Defect | Notch or drilled hole, size agreed per order |
| Defect Handling | Paint mark plus cut-out, or flagged on coil tag |
| Test Record | Indication count and position logged per coil |
| Surface | Bright, soap coated or dry film option |
| Coil Weight | 100–500 kg |
| Reference Standard | ASTM A555, EN 10263-5 |
What the Test Finds
Longitudinal Seams and Cracks
Seams are the defect cold headers fear most, because they run parallel to the axis and open under hoop stress at the die. Eddy current picks them up as a continuous signal along the length.
Slivers, Laps and Rolled-In Matter
Slivers from the billet and laps from poor roll pass alignment show as short, high-amplitude signals. So do inclusions close to the surface.
What It Cannot Find
Eddy current responds to discontinuities that disturb the induced current, which makes it a surface and near-surface method. Internal porosity and deep transverse defects are outside its reach; those are controlled by billet quality and by the upsetting test.
How the Test Runs In Line
Coil and Probe Arrangement
An encircling coil surrounds the wire at the exit of the drawing line. Smaller diameters run through a single coil; larger sizes may use a rotating probe head to cover the full circumference.
Reference Defect and Threshold
The threshold is set against a reference defect agreed at order stage, typically an electro-discharge notch of a stated depth on a sample of the same grade and diameter. The setting is verified at the start and end of each run.
Marking and Cut-Out
When a signal passes the threshold, the line marks the position. Depending on your instruction, the marked length is cut out and scrapped, or left in place and noted on the coil tag so it can be trimmed at your end.
Reading the Test Report
What the Report States
Test speed, coil and probe configuration, reference defect, threshold setting, number of indications and their positions along the coil.
Acceptance Criteria
The acceptance level is agreed per order, because a threshold tight enough for a fastener head may reject wire that is perfectly serviceable for a bent wire form.
Applications
Fasteners for Safety-Critical Assembly
Screws and bolts where a head crack is not an option and incoming inspection cannot cover every coil.
Cold-Formed Parts with Long Forming Sequences
Parts formed in four or more blows, where a small seam has more chances to open.
Wire for Automatic High-Speed Headers
Lines where a tool break costs more than the wire, and where full-length inspection replaces sampling.
Product Advantages
- Full-length inspection rather than end sampling, so a local defect cannot hide in the middle of a coil.
- Defect position is recorded on the coil tag, so your operator knows where the marked length sits.
- Reference defect and threshold are agreed at order stage and verified at the start and end of each run.
- Marked sections can be cut out at our line, so your press never sees them.
- Runs on the same drawing and annealing route as standard cold heading wire, without changing the mechanical properties.
Quality Control
Chemical composition by optical emission, tensile strength and hardness, diameter and ovality, coating weight where applicable, surface condition, plus the eddy current record for each coil. A mill test certificate 3.1 and the test report travel with the shipment.
Selection and Ordering Notes
- State grade, diameter and the forming operation, so the test threshold is set to the defect that actually matters for your part.
- Give the reference defect size you require, or describe the failure you are trying to prevent and we will propose one.
- Confirm whether marked lengths should be cut out at our line or flagged on the coil tag.
- State the acceptance criteria for indication count per coil.
- For parts where internal soundness matters as well, ask for the upsetting test alongside the eddy current record.
Send your part drawing and the defect you need to exclude, and we will set the test threshold and inspection route accordingly.
