As a corrosion-resistant structural material, Ni-Mo alloys were mainly used in the early 20th century. There are two industrial grades, one is Ni-Mo-Fe alloy, namely 0Mo20Ni60Fe20 (Haltelloy A), and the other is 0Mo28Ni65Fe5 (Hastelloy B). ), because the former can only solve the problem of hydrochloric acid corrosion below 70 feet, its application range is limited, it has been rarely used since the 1960s, and the latter has become widely used Ni-Mo due to its excellent corrosion resistance. Corrosion resistant alloy. The 0Mo28Ni65Fe5 alloy was born in the 1920s and has had some performance deficiencies during long-term use. To improve these properties, it has been developed to 4 generations of alloys. The second generation alloy is Haslelloy B-2 with low carbon, low silicon and low iron. This improvement solves the problem of intergranular corrosion of Ni-Mo alloy and the corrosion of heat affected zone. However, the alloy has aging brittleness and is in manufacture. Cracks occur in the process. In order to solve the unforeseen defects, the third generation alloy (Hastelloy B-3) and the fourth generation alloy (Hastelloy B) which control the Fe + Ci content have been developed based on the nature of the brittleness and crack occurrence. -4). Controlling the proper Fe + Cr content can suppress the precipitation of harmful p-phase (Ni4Mo), thereby improving the ageing plasticity and SCC resistance of the low-iron alloy. In order to solve the corrosion problem of Ni-Cr-Mo corrosion-resistant alloy in flue gas desulfurization equipment under almost anaerobic reductive acid corrosion conditions, a Hastelloy B-10 alloy was developed in Germany in 1996. The development history and chemical composition of Ni-Mo alloy are shown in Table 7-5 and Table 7-6.