What are the methods for non-destructive testing of steel castings?

Non-destructive testing is one of the most commonly used methods in the production of steel castings. Non-destructive testing is the detection of defects in surface and internal quality and precision while ensuring that castings are not damaged. . This article will introduce the non-destructive testing according to the testing method of steel castings.

There are many methods for nondestructive testing, and there are four main types commonly used in production: magnetic particle inspection, ultrasonic flaw detection, radiographic inspection, and liquid penetrant inspection.

-VT (Visual Testing)
The Visual Testing is one of the most widely used test method to investigate the surface aspect and observe potential discontinuities or failures, which should be detected under proper lighting conditions, monitored by an instrument able to measure the light intensity, the light meter.
-UT (Ultrasonic Testing)
The Ultrasonic testing is often performed on raw materials but can be also performed on critical areas to have an accurate and reliable detection of material discontinuities: an ultrasonic transducer (Ultrasound test instrument) sends high-frequency vibrations into a material section to find discontinuities which, if found, reflect the vibrations back to the transducer; the result is translated and displayed on an oscilloscope to reveal their extent and location.
-PT (Penetrant Testing)
The Penetrant testing, also called Liquid or Dye Penetrant Inspection, is generally used to locate and detect surface defects (cracks, porosity, leaking points) on non-ferrous and ferrous materials: testing fluid (penetrant) penetrates into the surface-breaking discontinuities and, after adequate penetration time, a developer should be applied: the penetrant is drawn out by capillary action so that an invisible crack becomes visible.
-MT (Magnetic Particle Testing)
The Magnetic Particle Testing is generally used to locate and detect surface sub-surface discontinuities in ferromagnetic materials. The area to be tested is magnetized by direct electric current transmission by a magnetic joke; in case of discontinuity, the magnetic field flowing through the specimen is interrupted and leakage field occurs, iron particles are then applied to the detected area and cluster to form an indication directly over the discontinuity. The indication can be visually detected under proper lighting conditions.

-PMI (Positive Material Identification)
The Positive Material Identification is the elemental identification and quantitative determination in percentage of metallic alloys, without regard to form, size and shape,