Low-cost large-heat-input-weldable high-toughness steel plate and manufacturing method thereof

Abstract

The invention discloses a low-cost large-heat-input-weldable high-toughness steel plate and a manufacturing method thereof. According to the low cost large-heat-input-weldable high-toughness steel plate and the manufacturing method thereof, metallurgical technical means of taking a component system of micro-alloyed steel with low C and high Mn-(Nb+Ti) as a basis, controlling the cold cracking welding sensitive index Pcm to be not higher than 0.22%, appropriately increasing the content of acid-dissolved Als, controlling the ratio of Mn/C to be 25-55, carrying out Ni+high Cr alloying, controlling [(%C)+(%Mn)/6]*(%Si) to be not greater than 0.035, controlling (%Mn equivalent)*(%Cr equivalent) to be not smaller than 2.7, carrying out Ca treatment, controlling Ca/S to be 0.80-3.00, controlling Ti/N to be 1.5-3.0 and the like are adopted, and a TMCP (Thermo-Mechanical Control Process) and a tempering process are optimized, so that the microstructure of a finished steel plate is of fine bainite, the average crystal group size is smaller than 15 microns, the steel plate can bear large-heat-input welding while uniform and excellent mechanical properties are obtained and the toughness and the plasticity are matched, and then, the low-cost large-heat-input-weldable high-toughness steel plate is particularly applicable to engineering machinery, bridge structures, offshore oil production platforms, oil storage tanks and the like.

Description

technical field [0001] The present invention relates to low-carbon low-alloy steel, in particular to low-cost high-strength toughness steel plate welded with large heat input and its manufacturing method. 100J, low cost, high heat input welding, high strength and toughness. Background technique [0002] 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 containers, building structures, automobile industry, railway transportation and machinery manufacturing; The performance of low-carbon (high-strength) low-alloy steel depends on its chemical composition and manufacturing process, among which strength, toughness, plasticity and weldability are the most important properties of low-carbon (high-strength) low-alloy steel, which ultimately depends on the quality of the finished steel. Microstructure state; with the continuous de...

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Problems solved by technology

[0008] Quenched and tempered high-strength and high heat input welding conflict with each other in terms of composition design and process design, and it is difficult to reconcile the problem that while improving the strength of quenched and tempered steel plates, it will inevitably lead to deterioration of HAZ toughness in high heat input welding; on the contrary, reducing carbon While improving the HAZ toughness of large heat input welding, i...

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