Welding is one of the most crucial processes in the manufacturing industry. A weld is a local coalescence of metals or non-metals produced by either heating the metals to welding temperature or with the use of pressure with or without the use of a filler metal. Welding is an exceptionally common staple of many industries, including construction, oil and gas industries, shipping and aerospace. It’s necessary to determine the quality of welds at different times during a product’s lifespan to ensure the weld remains firm, allowing the product to perform as expected. Quality control is needed to ensure safety and product longevity and several types of non-destructive testing can be used to ensure products can continue to perform within the extreme environmental conditions they’re often subjected to.
In this article we discuss the three main types of non-destructive testing which can be used to evaluate the strength of a weld: particle testing, radiographic testing and ultrasonic testing.
Particle testing uses magnetic particles to detect surface and subsurface discontinuities in ferromagnetic materials, such as iron, nickel, cobalt and some of their alloys. The object being tested is magnetised by applying a magnetic field into the part and detecting the flaws by application of fine metallic particles. Magnetic particle testing is particularly useful when surface discontinuities are too small to be seen with the naked eye, during a visual inspection. Particle testing is usually carried out on backchip and final welds after visual inspection.
Radiographic testing, like particle testing, is used to identify flaws in the welds of an object; either those on the surface or on the subsurface of the object. Radiographic testing, however, projects X-Rays or Gamma Rays through the test item and records them on imaging media located on the other side of the test object. Continuous areas will appear light grey on the imaging media and discontinuous areas will appear dark. This is because the consistent areas of the object have absorbed more radiation than those areas where cracks, faults or other defects are present.
Ultrasonic testing is a NDT method which broadcasts ultrasonic waves through a test object. Very small waves (0.1-50MHz) are transmitted into materials to detect flaws or inconsistencies. However, there are some limitations of ultrasonic testing, namely, that it can’t completely guarantee the structural integrity of a weld. Despite this, ultrasonic testing gives length and location along with depth of irregularities within an object. Ultrasonic testing is usually performed on final welds and at setup stage of weld joints.
Contact NDT Australia
If you are looking for non-destructive testing equipment, check out NDT Australia’s online store. We supply a range of NDT technology, including particle testing, radiographic and ultrasonic non-destructive testing equipment. We are open for business Monday to Friday, 7:30am to 4:00pm. Contact our friendly sales team on (02) 9524 0558 to ask any questions or to place an order for any of the products listed on our online store.