Pressure container steel having high toughness at -120 DEG C, and its production method

Abstract

A pressure container steel having a high toughness at -120DEG C comprises 0.06% or less of C, 0.05% or less of Si, 0.40-0.80% of Mn, 0.008% or less of P, 0.003% or less of S, 0.015-0.050% of Alt, 3.00-3.80% of Ni, 0.10-0.30% of Cu, 0.008-0.025% of Ti, and 0.004% or less of N, and also comprises one or above two of 0.50% or less of Cr, 0.50% or less of Mo, 0.040% or less of Nb, and 0.005% or less of Ca. A method for producing the pressure container steel comprises the following steps: carrying out smelting and continuous casting to form a casting blank; heating the casting blank; carrying out first-stage rough rolling; carrying out primary temperature control, and then carrying out second-stage rough rolling; carrying out secondary temperature control, and then carrying out fine rolling; and carrying out heat treatment according to the thickness of a steel plate for later use. The pressure container steel has a KV2 of 100J or more at -120DEG C, a transverse crack thickness rate (CTR) of 3% or less, a transverse crack length rate (CLR) of 10% or less, a transverse crack sensitivity rate (CSR) of 1.5% or less, a low Ni content and an excellent welding performance.

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 -120°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...

AI Technical Summary

Problems solved by technology

The nickel content in this literature is still high, that is, 7.5~10.0%, and the production cost is high

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