Non Destructive Testing

Non Destructive Testing

Non-destructive testing (NDT), also known as non-destructive testing (NDT), refers to heat, sound, light, electricity, magnetism, etc. caused by the abnormality of the internal structure of the material or the existence of defects without damaging the object to be tested. Changes in physical quantities to detect internal and surface defects of various known engineering materials, components, structural parts, etc.

Our NDT Capabilities Include:

-- X-Ray testing -- one of the best non-destructive inspection methods for detecting internal defects of castings.

In this method, the tested product is exposed under x-ray radiation. Parts of the radiation are absorbed by the product, and the remaining portion of the radiation exposes the radiographic film. Dense material withstands the radiation penetration, so the film is exposed to a lesser degree in those areas, giving the film a lighter appearance. Less dense materials allow more penetration and correlates to darker areas on the film. Any hole, crack or inclusion that is less dense than the casting alloy is revealed as a dark area. X-Ray testing is able to find internal defects of investment casting product including gas porosity and gas holes, shrinkage which appears as dendrite/filamentary/ jagged, cracks and so on.

-- Material Analysis -- In the process of investment casting, the composition of material need to be changed when it is molten according to our clients’ requirements. Therefore, material composition is one of the most important properties of our products. It influences all the casting’s physical properties, ranging from the fluidity and castability of the metal when it is poured to the mechanical strength, toughness and corrosion resistance of the finished product. Meanwhile, many cast alloys have coarse segregated micro and macro structures which themselves pose challenges when it comes to accurately determining their composition. The selection of material not only affects the performance of casting products, but also affects the cost of investment casting. Right selection of material makes high quality products and saves you deals of money. That’s why the material analysis is a necessary and crucial inspection method for every foundry.

-- Hardness Testing -- Hardness is one of metallic properties of castings and is defined as the resistance of the permanent mechanical deformation. Hardness testing is a quality test used in foundries to measure the properties of cast metals and their suitability for different applications. Its popularity is due to the non-destructive nature of the test, and its relationship with other mechanical properties. Hardness tests are performed after casting, cleaning and heat treatment of casting products. In the same heat treatment process, the hardness of the casting depends on the amount of carbon in the material. Foundries infer the tensile stress of a material based on the hardness test result. The higher the carbon contents, the higher the hardness of the material is. High hardness affects its cutting performance and makes machining processing difficult. However, if the hardness is too low, the strength of the casting parts and the wear resistance are reduced.

-- Magnetic Particle Inspection -- one of non-destructive testing (NDT) methods used to detect cracks at the surface of ferromagnetic materials such as steels and nickel-based alloys. Magnetic particle detection utilizes the interaction of the magnetic leakage field at the defect of the work piece with the magnetic powder. It takes advantage of the difference in magnetic conductivity of surface and near-surface defects of steel investment casting parts, such as cracks, slag, hairlines, etc. After magnetization, the magnetic field at the discontinuity of these materials will be changed. A magnetic leakage field will be generated on the surface of the work piece, where a part of the flux leakage is formed. Thus it attracts the magnetic powder formed and accumulated at the defect. It is called magnetic mark. Under appropriate light conditions, the defect position and shape are shown. Observing and explaining the accumulation of these magnetic powder, inspectors can find out the defects on casting parts.

-- Ultrasonic Inspection -- Ultrasonic nondestructive testing, also known as ultrasonic NDT or simply UT, is a method of characterizing the thickness or internal structure of a test piece through the use of high frequency sound waves. The frequencies, or pitch, used for ultrasonic testing are many times higher than the limit of human hearing, most commonly in the range from 500 KHz to 20 MHz. The time interval between the transmitted ray and reflected ray is recorded by a cathode ray oscilloscope. Any crack or void in the casting results in reflection or some of the sound from the crack which appears as a pip between the two pips representing the thickness of the casting. The depth of the crack from the surface of the casting can be easily calculated from the distance between these pips.

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