Low-temperature steel bar and its production method

Abstract

The invention discloses a low-temperature steel bar and a production method thereof, the chemical composition of which is calculated by mass percentage: Ni 0.8-0.9%, Mn 1.6-1.7%, Si 0.3-0.4%, C 0.04-0.08%, Al 0.01-0.02 %, P≤0.007%, S≤0.004%, O≤0.002%, N≤0.003%, As≤0.005%, H≤0.0002%, and the rest are Fe and unavoidable impurities. The production methods include KR molten iron pretreatment, Converter smelting, LF furnace refining, RH furnace refining, continuous casting and rolling. The invention completes the composition design and mass production of the low-temperature steel bar at a relatively low cost, and achieves the effects of strictly controlling impurity elements, inclusions and surface quality, and reducing low-temperature brittleness.

Description

technical field [0001] The invention relates to the technical field of iron and steel materials, in particular to a low-temperature steel bar and a production method thereof. Background technique [0002] Liquefied Natural Gas (LNG) storage tanks are small in size and generally consist of two tanks inside and outside. The inner tank is generally welded by low-temperature steel plates containing 9% nickel alloy steel, and the outer tank is a composite multi-layer The concrete structure, the outer tank wall and the lower ring beam concrete structure of the inner tank must use low-temperature steel bars that can withstand -165 ° C. The existing technology improves the low-temperature performance of the steel bars by adding alloy elements nickel, vanadium or titanium, although it can reduce the temperature of the steel bars. The low-temperature embrittlement transition temperature can be improved to improve the low-temperature impact toughness, but due to the addition of a large...

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Problems solved by technology

The existing technology improves the low-temperature performance of steel bars by adding alloy elements nickel, vanadium or titanium. Although it can reduce the low-temperature embrittlement transition temperature of steel and improve low-temperature impact toughness, due to the addition of a large number of alloy elements, the production of this type of low-temperature steel bars The cost has been greatly increased, which is not conducive to market promotion, and the steel smelting and rolling process methods used are also lacking in certain rationality

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