【Ten Years of Great Development in Chemical Processing Equipment】Breakthroughs in Invar Steel Welding for Large LNG Ships from 1965 to 2008

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Witness the ten-year rapid development of chemical processing equipment; praise the prosperity and strength of modern China. Replies will be rewarded – discussions are welcome. ------------------------------------------- Yinwa steel is essentially a nickel-iron alloy with a composition of 36% nickel, 63.8% iron, and 0.2% carbon. It was first discovered in 1896 by the French physicist C.E. Guialme. It is named Invar due to its property of having a thermal expansion coefficient that approaches zero below the magnetic phase transition temperature, namely the Curie point Tc; the name means “unchanging,” and it is transliterated in Chinese as Yinwa or Yinwa steel. And this phenomenon is known as the Invar Effect. Due to its low coefficient of expansion, low thermal conductivity, and high plasticity and toughness, Invar steel is known as the \"king of metals\" and is widely used in precision laser equipment, aerospace sensors, special transmission cables, and other fields. But its most important application area is, arguably, LNG carriers. In July 2001, after seven months of intensive collaborative efforts, Hudong-Zhonghua successfully built and developed the prototype thin-walled model hull of the LNG ship NO.96, and received approval certificates from the French company GTT as well as from classification societies in the UK, the US, France, Norway, Japan, and other countries. On December 15, 2004, the first LNG carrier was constructed at Hudong Zhonghua. A 147,000 cubic meter LNG carrier has LNG steel welds that are 130 kilometers long; per regulations, none of these welds are allowed to have any leaks. If a leak is found, it will take 1,000 man-hours to redo the work! The thickness of most Inconel steel components on LNG carriers is only 0.7 millimeters. The sheets, welding materials, and automatic welding equipment used in Inconel welding were all utilized for the first time in China. Through efforts to optimize the welding process, nearly 1,000 parameters were identified, and more than 200 new welding procedures were developed. There are thousands of processing steps, and nearly 7,000 items that need to be submitted for approval by GTT Corporation, the American Classification Society, and the shipowner, with a requirement of \"zero errors\". Otherwise, the cost will be extremely high—according to data obtained from foreign shipbuilding companies, the time and financial resources required to redo work once a problem arises are as much as 500:1 compared to normal circumstances! In 2008, Hudong-Zhonghua Shipbuilding Co., Ltd., which is part of China State Shipbuilding Corporation, broke the monopoly held by countries such as South Korea for the first time by building and delivering China’s first large-scale LNG carrier. The process by which China’s Hudong Shipbuilding Corporation in Shanghai successfully built an LNG carrier with a capacity of 147,000 cubic meters was covered in CCTV’s News Broadcast as well as on CCTV9’s Documentary Channel in the program \"Super Projects 5\".