Pressure container steel with high toughness at -140 DEG C and production method thereof

Abstract

The invention relates to pressure container steel with high toughness at -140 DEG C. The pressure container steel comprises the following components by weight: less than or equal to 0.05 of C, less than or equal to 0.05 of Si, 0.50-1.00 of Mn, less than or equal to 0.006 of P, less than or equal to 0.003 of S, 0.015-0.050 of Alt, 4.50-5.30 of Ni, 0.02-0.05 of Nb, 0.008-0.025 of Ti, less than or equal to 0.004 of N and one or more of less than or equal to 0.50 of Cr, less than or equal to 0.50 of Mo, less than or equal to 0.30 of Cu and less than or equal to 0.005 of Ca. A process of the pressure container steel comprises the following steps: smelting and continuously casting to form a blank; heating a casting blank; rough rolling at a first stage; rough rolling at a second stage after cooling for the first time; finish rolling after cooling for the second time; and carrying out heat treatment according to the thickness of a steel plate for later use. When the pressure container steel is at -140 DEG C, KV2 is not less than 100J, a transverse crack thickness rate CTR is less than or equal to 3%, a transverse crack length rate CLR is less than or equal to 10%, a transverse crack sensitivity rate is less than or equal to 1.5%, the content of Ni is low, and the welding performance is excellent.

Description

technical field [0001] The invention relates to an alloy steel for containers and a production method thereof, specifically belongs to a low-temperature pressure vessel steel and a production method thereof, and further relates to a pressure vessel steel suitable for -140°C and a production method thereof. Background technique [0002] Before the present invention was proposed, although there were some research works on Ni-based low-temperature steels, the way of thinking was that the content of Ni added would increase as the temperature decreased, which resulted in high production costs. For example, after searching, the Japanese patent document JP60059032 discloses "a high-nickel steel plate with excellent low-temperature toughness and low yield ratio and its manufacturing method", and its composition mass percentage is C≤0.03, Si: 0.02~0.22, Mn: 0.05~ 0.47, P≤0.005, S≤0.005, Ni: 7.5~12.0, Al: 0.01~0.10, if necessary, one or more elements such as C, Mn or Nb (0.005~0.03) o...

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Problems solved by technology

The content of Ni in this document is 4.70~5.30%, which is relatively low compared with its Japanese patent, but its adaptabl

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