On November 28, 2021, the high-performance steel materials team led by Professor Dong Han from the School of Materials Science and Engineering of Shanghai University, Hebei Longfengshan Casting Co., Ltd., Qifeng Precision Technology Co., Ltd., Zhoushan 7412 Factory, Jiangsu Institute of Metallurgical Technology, After more than a year of joint research, Shanghai University (Zhejiang) High-end Equipment Basic Parts and Materials Research Institute and other six units have passed the "material production-fastener manufacturing-service evaluation" whole industry chain collaboration, based on the theory of high performance of steel materials, Successfully developed B17.8 and B19.8 steels for ultra-high-strength fasteners using the high-purity iron raw materials produced by Longfengshan Casting, forming a 16.8 and 19.8-grade fastener manufacturing technology.

Through the optimization of materials and heat treatment process, the room temperature tensile strength of 16.8 and 19.8 bolts meets 1600~1770MPa and 1900~2070MPa, respectively. Shear test (according to GJB 3376-1998) results show that the shear force of grade 16.8 and 19.8 bolts reaches 97KN and 115KN respectively; tensile fatigue strength test at room temperature (according to GJB 3376-1998 and GJB715.30A-2002, load ratio = 0.1) The results show that the developed fasteners meet the fatigue life requirements (average fatigue life is not less than 65,000 times, and individual fatigue life is not less than 45,000 times); delayed fracture resistance test (according to GJB 715.12-1990, constant under atmospheric environment Tensile stress was maintained for 96 hours). The results showed that the bolt did not break during the test time, and no cracks were found on the surface and thread of the bolt after unloading; the comprehensive performance of the newly developed ultra-high-strength bolt satisfies the service requirements.