【Frontiers in HaiChuan Chemical Technology】Material Development for PWHT Manufacturing Process Without Post-Weld Heat Treatment Based on ECA

Thread Content

Recently, Mitsubishi Heavy Industries Corporation and Nippon Steel Corporation issued a joint statement stating that they have made significant progress in the technology related to the cargo holds of large low-pressure liquefied carbon dioxide transport ships. The new type of steel developed by Nippon Steel has been used in the construction of such ships’ cargo holds, and a post-weld heat treatment (PWHT) exemption technique was developed based on engineering critical assessment (ECA). Thanks to this technology, both parties have recently received the world’s first General Design Approval (GDA) issued by the Japanese Classification Society (NK). This technology is an important part of Mitsubishi Heavy Industries’ efforts to standardize large liquefied carbon dioxide carriers. Through cooperation, both parties aim to develop specialized steel suitable for large liquefied carbon dioxide storage tanks, as well as to establish a PWHT-free manufacturing process based on ECA, thereby achieving a balance between economic efficiency and production efficiency. https://p3-sign.toutiaoimg.com/tos-cn-i-axegupay5k/99f572cb5ac44793a000f6e3ee03d91e~tplv-tt-origin-web:gif.jpeg?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1766026337&x-signature=TSOyRED3ZnhQKynka2yIXWkFvL4%3D Source: Mitsubishi Heavy Industries’ official website. It is understood that the new type of steel developed jointly by Nippon Steel and Mitsubishi Shipbuilding belongs to the TMCP (Controlled Rolling and Controlled Cooling) steel series under Nippon Steel’s “NSCarbolex™ Solution” brand; this steel can enhance the economic efficiency across the entire value chain of carbon capture, utilization, and storage (CCUS). The new steel grade, KF460 in accordance with the NK specifications, features high strength, excellent low-temperature toughness, and cost efficiency; it provides the essential material foundation for the use of PWHT-free technology in the large low-pressure liquid carbon dioxide storage tanks developed by Mitsubishi Heavy Industries. Generally, in the manufacture of large liquefied carbon dioxide storage tanks, if economical high-strength carbon-manganese steel is used, the welds usually need to undergo PWHT in accordance with IGC specifications. However, the heat treatment equipment capable of annealing large storage tanks is extremely limited, which has become the main \"bottleneck\" restricting the enlargement of storage tanks and their stable supply. To address this challenge, Mitsubishi Shipbuilding evaluated the weld integrity using ECA, based on the material properties of the steel plates developed by Nippon Steel. The evaluation results confirmed the feasibility of the PWHT-free manufacturing process, and GDA certification was successfully obtained. The successful acquisition of GDA not only ensures the safety of low-pressure liquefied carbon dioxide storage tanks, but also lays the foundation for improving their economic efficiency and production efficiency, with the potential to significantly reduce the costs associated with transporting liquefied carbon dioxide. Taking this collaboration as an opportunity, Mitsubishi Heavy Industries and Nippon Steel will work together with partners in the liquefied carbon dioxide storage tank manufacturing supply chain to advance the commercialization of new types of steel and low-pressure liquefied carbon dioxide storage tanks.