Radiography and ultrasonic testing are non-destructive tests that find internal defects in castings without cutting them open. Radiography passes X-rays or gamma rays through the part to make an image, while ultrasonic testing sends sound waves into the metal and listens for echoes from flaws.
They are usually applied to pressure parts, safety-critical parts and heavy steel castings. For most general iron castings, they are used on first samples and on a sampling basis, not on every piece.
Radiography
In radiography, radiation passes through the casting onto film or a digital detector. Thinner or hollow areas let more radiation through and show up darker. Gas holes, shrinkage, inclusions and cracks appear as shapes that a trained interpreter can grade.
Grading is usually done by comparing the image with reference radiographs. ASTM publishes reference radiograph standards for steel castings, and EN and ISO standards cover radiographic testing of castings. Your order should name the standard and the acceptance severity level for each zone.
Radiography gives a permanent record, which is useful for disputes. It is slower, needs radiation safety controls, and becomes harder on very thick sections.
Ultrasonic testing
In ultrasonic testing, a probe sends high-frequency sound into the metal. Flaws reflect the sound back, and the instrument shows their depth and size. It works well on thick steel sections and is quicker and more portable than radiography.
It needs a reasonably smooth surface and a skilled operator. Coarse grain structures, common in some cast metals, scatter the sound and make interpretation harder. EN 12680 covers ultrasonic testing of castings, with separate parts for steel and for SG iron, and ASTM has its own methods.
Surface methods
Two other tests look for cracks that break the surface:
- Magnetic particle testing works on ferromagnetic metals such as iron and carbon steel, showing cracks as lines of fine iron particles.
- Dye penetrant testing works on any metal, including stainless steel, using a coloured or fluorescent dye drawn into cracks.
Who does the testing
Some Gujarat foundries have in-house radiography or ultrasonic equipment, while many send parts to outside testing laboratories. Either way, the operator should hold a recognised qualification, for example under ISO 9712 or ASNT schemes, at the right level for the method.
Ask for the procedure, the operator's qualification and sample reports before production starts. Testing that shows up only at the end is often rushed. If you want an independent result, a third-party inspection can witness or repeat the tests.
Writing the requirement
- Name the method, the standard and the acceptance level on the drawing or order.
- Mark the critical zones, since a part does not need the same level everywhere.
- Say how many parts are tested: all, first samples only, or a sample from each heat.
- Say whether repair welding is allowed and whether repaired areas must be retested.
Next step
The defects these tests find are described in common casting defects. We help set realistic test requirements and arrange witnessed testing before shipment. To discuss your parts, book a free sourcing review.