Korean steelmaker’s R&D center invests in X-ray CT for vehicle weld inspection

One of the world’s largest steel-producing companies, POSCO, has invested in an X-ray CT (computed tomography) system for its research and development center in Incheon, Korea. Installed in the summer of 2022 and fully operational by the end of that year, the microfocus XT H 225 ST 2x system was manufactured by the Industrial Metrology Business Unit of Nikon Corporation (https://industry.nikon.com). The equipment includes in its specification the company’s unique Rotating.Target 2.0, which provides industry-leading performance by enabling continuous operation at up to 450W. Consequently, three times higher resolution is delivered in a given scan time or data collection is three times faster for a given resolution. POSCO Songdo R&D Center had been using contract inspection services provided by Nikon since 2021, principally for testing welds on behalf of the steel group’s automotive industry customers that wanted to better understand the performance of its joining processes. During the development of a new, lightweight steel from which it is possible to produce safe automotive parts, the company found that during resistance spot welding tests, the zinc plating penetrated the weld and liquid metal embrittlement (LME) occurred. Having discovered this phenomenon, it set about developing a new variant of the material in which LME does not happen. In order to study the effect, it was necessary to inspect inside the weld and analyze the results, for which purpose non-destructive X-ray CT was essential.

The contract X-ray inspection service and support provided by Nikon proved highly successful, with comprehensive CT results returned within five working days. POSCO was able to ascertain that the effect on weld quality was different, depending on the position of the LME and the extent of its penetration. The results have been submitted to various groups internally and externally and POSCO is now in discussions with various automotive manufacturers to amend LME standards within the industry. The whole process has also allowed the R&D center to appreciate the full capabilities of X-ray CT before buying a system of its own. This had always been foreseen in order to raise weld inspection productivity and to make the equipment available for other quality control duties within the center.

Uhm Sangho, Senior Principal Researcher at the Incheon facility said, “When it came to taking the decision to purchase, we were already familiar with Nikon through our ongoing association with them, so we were able to make an informed choice. In the end, what made us decide in favor of this manufacturer was the high continuous X-ray power generated by the XT H 225 ST 2x. It can be focused onto a very small spot measured in microns, thanks to rapid heat dissipation from the rotating target, which no one else offers.”

He added that the choice of the Nikon solution was influenced by other factors as well. The machine features Half.Turn CT, which almost halves the angle through which a specimen rotates during scanning, nearly doubling processing speed without loss of image clarity. Cost of ownership is low, due in part to the open tube design and the long life and easy exchange of the filament. Additionally, the equipment is easy to calibrate and the software for acquiring and reconstructing the CT data is described as excellent.

As POSCO Songdo R&D Center continues on behalf of its customers to push the boundaries of research in the automotive sector, as well as in other industries that use the steel that the group manufactures, its partnership with Nikon reaffirms its commitment to remaining at the forefront of technological innovation. Both companies are market leaders in their respective fields and each shares the same goal – to revolutionize quality control and maximize productivity throughout all branches of the manufacturing industry.

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