Low temperature tenacity excellent low yield ratio high intensity steel plate for welding heat influenced part and mother plate, and manufacturing method thereof

Abstract

The invention discloses a high-tension steel plate with a low tensile ratio, which satisfies the specified chemical composition component, and is composed of following mixed organization: in a microscopic constitution at a position of t / 4 (t: thickness of the plate), ferrolity percent in the whole organization is 60-85 surface percent; island shaped martensite percent is 1-5 surface percent; the excess is bainite constitution. Besides, remnant austenite in the island shaped martensite has over 60 surface percent. Based on the composition, low-temperature flexibility of HAZ is still excellent even when welding is carried out through high heat energy input; besides, the low-temperature flexibility of parent metal (steel plate) is also excellent.

Description

technical field [0001] The present invention relates to a low-yield-ratio high-strength steel sheet excellent in low-temperature toughness of the welded heat-affected zone and the base material, and is used in applications exposed to low temperatures, such as a multifunctional container that can carry liquefied ammonia and liquefied propane gas together. Low-yield-ratio high-tensile steel plate with excellent low-temperature toughness of welded heat-affected zone and base material. In addition, the present invention is not limited to the welding method of the above-mentioned high-tensile steel plate, but can be applied to submerged arc welding, gas-electric welding, etc., and the following is only a single-sided submerged submerged welding method that ensures the toughness of the weld-affected part, which is particularly difficult to input high heat energy. The implementation of arc welding will be described as an example. Background technique [0002] In recent years, in o...

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Problems solved by technology

However, the addition of Nb, Mo, etc. does not achieve the same toughness as the HAZ, and the toughness of the base material cannot be achieved at a level that can further ensure safety (-90°C or less in terms of fracture transition temperature vTrs)

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