High-strength steel material having excellent low-temperature strain aging impact properties and method for manufacturing same

Abstract

The present invention relates to a steel material for pressure vessels, offshore structures and the like and, more specifically, to a high-strength steel material having excellent low-temperature strain aging impact properties and a method for manufacturing same, the high-strength steel material comprising 0.04-0.14 wt% of carbon (C), 0.05-0.60 wt% of silicon (Si), 0.6-1.8 wt% of manganese (Mn), 0.005-0.06 wt% of soluble aluminum (sol. Al), 0.005-0.05 wt% of niobium (Nb), 0.01 wt% or less (not including 0 wt%) of vanadium (V), 0.001-0.015 wt% of titanium (Ti), 0.01-0.4 wt% of copper (Cu), 0.01-0.6 wt% of nickel (Ni), 0.01-0.2 wt% of chromium (Cr), 0.001-0.3 wt% of molybdenum (Mo), 0.0002-0.0040 wt% of calcium (Ca), 0.001-0.006 wt% of nitrogen (N), 0.02 wt% or less of phosphorus (P) (not including 0 wt%), and 0.003 wt% or less of sulfur (S) (not including 0 wt%), with a balance of Fe and other inevitable impurities, and comprising a mixed structure of ferrite, pearlite, bainite and a martensite-austenite (MA) composite as a microstructure, wherein the fraction of the MA composite is 3.5% or less (not including 0%).

Description

technical field [0001] The present disclosure relates to steel materials used as materials for pressure vessels, offshore structures, and the like, and more particularly, to high-strength steel materials having excellent low-temperature strain-aging impact properties and methods of manufacturing the same. Background technique [0002] Recently, due to the depletion of energy sources, mining areas have moved to deep sea areas or arctic areas, and thus, mining and storage facilities have become larger and more complex. Steel materials used therein are required to have excellent low-temperature toughness to secure high strength and equipment stability to reduce weight. [0003] Meanwhile, since cold deformation often occurs in the process of manufacturing steel with strength and toughness as described above to form steel pipes or other complex structures, the steel is required to significantly avoid toughness reduction due to strain aging caused by cold deformation. [0004] T...

AI Technical Summary

Problems solved by technology

[0006] However, as structures etc. continue to become larger and more complex, the amount of cold deformation required for steel materials increases, and the temperature of the use environment decreases to that of the Arctic Ocean

Therefore, it is difficult to effectively prevent the decrease in toughness caused by strain aging of steel materials by conventional methods.

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