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Zhengyuan Tower Equipment Overcomes the Challenges of Radiographic Testing for Stainless Steel Welds. Author/Source: Zhengyuan Group. Date: 2021-04-09. Clicks: 11. The flaw detection team at Zhengyuan Tower Equipment is a dynamic group; the average age of its members is in their 30s. They work shifts both during the day and at night without pause, yet they receive little attention, and people are even somewhat unfamiliar with them. Why? This is because flaw detection is always a type of work where hard work goes unnoticed and efforts remain unseen; however, those who work in this field must obtain professional certification in non-destructive testing before they can work ； The quantity and performance specifications of the instruments and equipment must meet relevant regulatory requirements, and the operating procedures are subject to supervision throughout the entire process; any deviation is not permitted. Flaw detection is a task that requires high technical skills, long working hours, and strict safety precautions. If no one can see it, then naturally there is no way to pay attention to it. Faced with increasing production demands, stricter quality requirements, and the absolute necessity to maintain strict isolation measures, all the employees in the flaw detection team, driven by a spirit of hard work and determination, have trained diligently, pursued innovation, improved efficiency, and thus promoted production. The road ahead is long and arduous; one must keep seeking high and low. New inspection technologies keep emerging, and there is no existing experience to draw on in work. Everyone must strive to combine the three principles of \"using one’s brain actively, using one’s eyes actively, and using one’s hands actively,\" seek advice from experienced workers when faced with problems, and continuously summarize experience, thereby improving the overall level of inspection techniques. Recently, Zhengyuan Tower Equipment undertook the task of manufacturing a stainless steel pressure vessel. The root welds of the stainless steel cylinder butt joints (designated as B14-B22, A14-A21) are made of S31603 material with a thickness of δ=12 millimeters. After X-ray inspection of these welds, multiple intermittent linear shadows were detected on the film. Inspection personnel are also confused upon seeing such images; they initially conclude that these images do not indicate any dangerous defects such as cracks, lack of penetration, or lack of fusion in the welds. The exact cause cannot be determined yet. However, according to NB/T 47013.2-2015 \"Non-destructive testing of pressure equipment – Part 2: Radiographic testing\", such images are not allowed to exist, and the film in question is considered unqualified. The team leader immediately reported this issue to the company’s production department. The production office convened the process room and on-site welders to discuss countermeasures together. Everyone should carefully examine each step of the welding process, review the details of the welding procedure qualification documents (JHP11534/JHP00171), and compare the specific sequence of operations, in the hope of identifying any factor that might cause strip-like patterns on the radiographic films. After intense discussion, a preliminary consensus was reached: there is no issue with the welding process; the welds showing strip-like patterns should be surface-ground before further testing. The production office specifically arranged for welders with proficient skills to carry out the work. Subsequently, another radiographic inspection was conducted on a weld that had been ground and repaired, and the strip-like patterns were still present on the X-ray film. The presence of strip-shaped shadows makes it difficult for inspection personnel to determine appropriate evaluation criteria, preventing the production of radiographic films that meet quality standards. This creates an irreconcilable conflict between inspection quality and production progress, and the issue of strip-shaped shadows troubles everyone involved. Under the leadership of the company’s chief engineer, technical professionals from areas such as production, process engineering, and flaw detection held a specialized technical seminar. Everyone worked together to identify problems and their causes, striving to find effective solutions. Ultimately, the following objectives were set: First, it is necessary to prove whether the strip-shaped shadows represent actual defects ； Secondly, identify the specific cause of the shadow appearing ； Another thing is to take specific measures to eliminate the impact of shadows. With clear goals, everyone took active action. The flaw detection personnel are fully aware of the seriousness of their task, knowing that a one-day delay in production means a shorter timeline and a significant increase in costs. Unutilized labor, equipment depreciation, and material consumption are constantly eroding a company’s profit margins. The flaw detection personnel faced the challenges head-on, sought standards and relevant information, drew on various sources of knowledge, sought professional expertise, and looked for ways to solve the problems. As the saying goes: Pressure creates motivation. Someone asked whether the company’s “TOFD imaging detector” can determine whether the “strip-shaped shadows represent actual defects” Without delay, the flaw detection personnel developed the process, adjusted the equipment, and carried out on-site testing all in one go. Through process comparison and professional evaluation, as well as comprehensive judgment by the flaw detection personnel, it was determined that the test results were affected by the coarse grains of the stainless steel. Although the TOFD images were a bit blurry, it could be confirmed that no linear defects were present in the weld; in other words, the linear shadows on the film did not represent actual defects. To date, the interim achievements have provided great encouragement to everyone. Immediately afterwards, the inspection personnel found through online research that when assembling austenitic stainless steel plates, after welding one side using submerged arc welding, gas tungsten arc cutting is used on the other side of the weld to remove residual material. If the root cleaning process is not carried out properly, intermittent shadow streaks are likely to appear on the X-ray film. By combining the on-site production conditions and conducting analysis and discussions, they finally identified the cause of the problem. Austenitic stainless steel has a coarse grain structure, which tends to cause diffraction patterns during radiographic testing. After root cleaning of the weld using carbon arc gas gouging, a carburized layer about 0.1 mm thick remains on the inner surface of the weld. Since the carburized layer was not completely removed, radiation exposure exacerbates the diffraction phenomenon, resulting in linear shadows on the film. Time waits for no one; the production department promptly arranged the work to eliminate the defects, with inspectors overseeing the entire process. After removing the residues, the inside of the groove was polished using a grinder to ensure that the grinding depth exceeded 0.1 mm, thereby allowing the carburized layer to be completely removed. At the same time, the flaw detection team adjusted the process parameters in a timely manner, increased the radiation energy, and minimized the impact of radiation diffraction patterns on the film as much as possible. After three days and nights of continuous work, the welded joints, once processed, were subjected to radiographic testing again, yielding satisfactory test results. Change leads to adaptability; adaptability ensures longevity. The personnel of the Zhengyuan Tower Equipment Inspection Team always adhere to innovation and serving production, strive to improve their skills, and meet challenges; they will surely make further efforts in future production processes to achieve new accomplishments.