Non-Destructive Hardness Testing of Every Part with Eddy Current

✨Non-Destructive Hardness Testing of Every Part with Eddy Current✨

Abnormal heat treatment or mixed steel grades are among the most dangerous defects because they are invisible: dimensions and weight match a good part, and the problem is found only in hardness testing or at the customer.

This article explains non-destructive hardness testing with eddy current, which checks every part.

■ Problems with conventional hardness testing

Tested parts are destroyed
Only a few samples per lot can be checked
When a problem is found, the whole lot is often scrapped because good parts cannot be separated

■ How eddy current testing works

A coil driven by alternating current creates a magnetic field.

When a metal part passes through, eddy currents flow in its surface.

Material composition, hardness after heat treatment, microstructure, shape and cracks change the signal; the tester compares it with a good master part and judges OK or NG without touching the part.

■ What it detects

Hardness abnormalities: under-hardened, over-hardened or not heat-treated
Mixed steel grades
Cracks and deep scoring, e.g. bolt head cracks
Shape or size differences and parts that skipped a process

It works on electrically conductive metals such as steel, stainless steel, aluminium and brass.

Resin and rubber parts need vision inspection instead.

■ Eddy current systems available in Thailand

FTS-eddy1: manual, non-contact tester using a master coil and a test coil; ideal for urgent lots; 100% inspection of lots of 10,000–100,000 parts.
FTS-eddy1 Auto Sorter: with a parts feeder for automatic loading and OK/NG sorting.
ELOTEST IS3 + VIZION sorting machine: eddy current and vision inspection together at 150–300 parts per minute.
High-speed eddy current standard machine: 360° bolt head crack inspection at up to 300 parts per minute.

Details and videos: eddy current testers.

■ When to use eddy current

Safety-critical parts where every piece must meet hardness
A lot suspected of mixed material, where you want to rescue good parts instead of scrapping it
To stop destructive sampling