Quenching/subzero treatment method for heat treatment of low-temperature nickel steel

Abstract

The invention relates to a quenching / subzero treatment method for heat treatment of low-temperature nickel steel, which comprises the following steps: based on characteristics and service conditions of low-temperature nickel steel, performing quenching, rapid cooling and liquid nitrogen subzero treatment on 9Ni low-temperature steel; and performing low-temperature tempering to relieve the internal stress, thus greatly enhancing the strength, toughness and hardness of the 9Ni low-temperature steel. After the treatment, the hardness can be up to HRC31-33, the yield strength is up to 695-705MPa, the tensile strength is up to 750-760MPa, and the low-temperature impact energy of the toughness is up to 250-260J. The technical method is advanced, full and accurate in data, favorable in treatment effect and high in stability, thus being a very ideal low-temperature nickel steel quenching / subzero treatment method. Other types of low-temperature steel can also be treated by using the method.

Description

technical field [0001] The invention relates to a quenching cryogenic treatment method for low-temperature nickel steel, belonging to the technical field of heat treatment methods and applications of low-temperature alloy structural steel. Background technique [0002] A large amount of steel is used in mechanical equipment. The steel used when the design temperature is ≤ -20°C is collectively called low-temperature steel. For example, the steel used in containers and pipelines used in liquefied petroleum gas, liquid nitrogen, and liquid oxygen is low-temperature steel. The steel used in equipment serving in cold regions and refrigerated storage refrigeration equipment is also low-temperature steel. The characteristic of low-temperature steel is that it does not deform at low temperature and can still maintain the mechanical properties of steel. Low-temperature steel is to meet the needs of petrochemical and refrigeration equipment. And developed special steel. [0003] Low...

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Problems solved by technology

[0004] The low-temperature steel with a nickel content of 9% is called 9Ni low-temperature steel, which has good low-temperature toughness and is often used to manufacture liquefied natural gas storage tanks. With the development of the oil and gas industry, the utilization rate of 9Ni low-temperature steel has been greatly increased. However, the heat treatment process of 9Ni low-temperature steel has lagged behind. According to the current conventional heat treatment method, it is difficult to meet the requirements of mechanical properties of 9Ni steel, especially the low strength and toughness, which greatly affects the safety of low-temperature steel used at low temperature.

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