Steel used at lower temperature and method for manufacturing same

Abstract

The invention discloses a steel used at a lower temperature and a method for manufacturing the same. The steel comprises the following chemical components by weight percentage: 0.060 to 0.090 percent of C, less than or equal to 0.20 percent of Si, 1.10 to 1.50 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.003 percent of S, 0.040 to 0.070 percent of Als, 0.05 to 0.45 percent of Cu, 0.05 to 0.35 percent of Ni, 0.05 to 0.30 percent of Cr, 0.007 to 0.011 percent of Ti, 0.007 to 0.020 percent of Nb, less than or equal to 0.0040 percent of N, 0.001 to 0.011 percent of Ca, and the balance of Fe and inevitable impurities. The manufacturing process comprises of the steps: making the steel plate obtain excellent low-temperature toughness and making the steel platebear the big line energy welding. The steel and the method can be widely applied to petroleum natural gas pipelines, low-temperature gas tank bodies LPG, low temperature steel plates of LNG.

Description

technical field [0001] The invention relates to a steel plate for low temperature, in particular to a steel plate capable of withstanding large heat input welding and a manufacturing process thereof, and is mainly used as a manufacturing material for LPG cryogenic storage tanks and offshore platforms in icy sea areas. Background technique [0002] As we all know, low-carbon (high-strength) low-alloy steel is one of the most important engineering structural materials, widely used in oil and gas pipelines, offshore platforms, shipbuilding, bridge structures, boiler pressure vessels, building structures, automobile industry, railway transportation and machinery under manufacture. The properties of low-carbon (high-strength) low-alloy steel depend on its chemical composition and the process system of the manufacturing process, among which strength, toughness and weldability are the most important properties of low-carbon (high-strength) low-alloy steel, which are ultimately dete...

AI Technical Summary

Problems solved by technology

[0003] When manufacturing thick steel plates with low-temperature transverse impact toughness (single value) ≥ 120J at -80°C, it is generally necessary to add a certain amount of precious alloying element Ni to the steel to ensure that the base steel plate has excellent low-temperature toughness; During heat-affected welding, the low-temperature toughness of the welding heat-affected zone (HAZ) is severely deteriorated, and the low-temperature ductile-brittle transition temperature of the heat-affected zone (HAZ) is generally difficult to reach -80°C [EP0288054A2, US Patent 4851052, EP 0839921A1]; A large number of patent documents only explain how to realize the low-temperature toughness of the base steel plate, and explain less about how to obtain excellent low-temperature toughness of the heat-affected zone (HAZ) under welding conditions, especially how to ensure the heat-affected zone (HAZ) when welding with large input energy. HAZ) have very little low temperature toughness [Zhao 63-93845, Zhao 63-79921, Zhao 60-258410, special flat 4-285119, special flat 4-308035, flat 3-264614, flat 2-250917, flat 4-143246, US Patent4855106, US Patent5183198, US Patent4137104]

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