Low-temperature 9Ni steel two-phase region quenching heat treatment method

Abstract

The invention discloses a low-temperature 9Ni steel two-phase region quenching heat treatment method. The method specifically comprises the following steps of S1, firstly, machining a 9Ni steel blockinto four 70 mm X 80 mm X 14 mm steel plates; S2, performing heat treatment on the steel plates; S3, cutting the samples into metallographic samples with the size of 14 mm X 14 mm X 3 mm, and then embedding the metallographic samples into cylindrical block bodies with the diameter of 32 mm through cold embedding; S4, performing surface treatment on the samples; S5, observing the phase compositionof microstructures of the samples subjected to surface treatment through a scanning electron microscope; S6, scanning martensite (200) and (211) and austenite (200), (220), and (311) through XRD to calculate the content of the rotary austenite; and S7, machining the workpieces subjected to heat treatment into impact samples and tensile samples according to the national standard. According to the method, by exploring the quenching temperature of a two-phase region, the obtained microstructures are fine and uniform, and the strength and the low-temperature toughness reach the optimal ratio underthe condition that the temperature of the two-phase region is 640 DEG C and the temperature is kept for 30 min.

Description

technical field [0001] The invention relates to the technical field of heat treatment technology, in particular to a heat treatment method for two-phase region quenching of low-temperature 9Ni steel. Background technique [0002] As the world's energy consumption continues to grow, people are increasingly interested in the use of natural gas, especially as a clean and high-calorie energy source. Liquefied natural gas (LNG), mainly composed of methane and a small amount of minor components such as ethane, propane, and nitrogen, is a clean energy source widely used as a domestic and industrial fuel due to its abundance, versatility, and clean-burning properties . However, the geographical locations of the world's largest reserves of natural gas are generally far away from major consumption areas, so we need large-scale storage and long-distance transportation. Due to physical reasons, the temperature of liquefied natural gas is usually -162°C. Due to the lower temperature, t...

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Problems solved by technology

[0005] The existing two methods have disadvantages. The heat treatment method of the former is relatively simple, which only includes quenching and tempering, and the obtained strength and low-temperature toughness are low. The material properties obtained by the latter heat treatment method are better, but the research Personnel have been researching on this aspect relatively shallowly, and the change of quenching and tempering temperature has little effect on the properties of the material, and the optimal performance has not been achieved.

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