Thick steel plate with excellent toughness in welding heat-affected zone and manufacturing method thereof

Abstract

The invention discloses a thick steel plate with excellent tenacity for an excellent-tenacity welding heat affected zone and a manufacturing method thereof. The method comprises the following steps: 1) smelting, refining and continuously casting, wherein the thick steel plate comprises the following components by mass percent: 0.05-0.09% of C, 0.10-0.30% of Si, 1.2-1.6% of Mn, no more than 0.02% of P, 0.001-0.006% of S, 0.20-0.40% of Ni, 0.15-0.3% of Cu, 0.005-0.03% of Ti, 0.003-0.1% of Al, 0.0005-0.005% of Ca, no more than 0.02% of REM, no more than 0.02% of Zr, 0.0002-0.005% of B, 0.001-0.006% of N and the balance of Fe and inevitable impurities, wherein Ti / N is smaller than or equal to 6 and greater than or equal to 1; 2) rolling; 3) cooling. By adopting the manufacturing method, occluded foreign inclusions in fine dispersed distribution can be formed. By controlling the surface density of a micron occluded foreign substance of which the diameter is greater than or equal to 1 micron, the Ca / Al ratio and the length-width ratio of the occluded foreign inclusions, the surface density, the Ca / Al ratio and the length-width ratio of micron inclusions of which the diameter is greater than or equal to 1 micron, the surface density of a submicron occluded foreign substance of which the diameter is smaller than 1 micron, the tensile strength of base metal is greater than or equal to 510MPa, the welding line energy is 200-400 kJ / cm, and the welding heat affected zone has good impact toughness.

Description

technical field [0001] The invention belongs to the field of iron and steel metallurgy and iron and steel materials, and in particular relates to a thick steel plate with excellent toughness in the heat-affected zone of welding and a manufacturing method thereof. / cm, the average Charpy impact energy of the welding heat-affected zone of the steel plate at -40°C is above 50J, the welding heat-affected zone (HAZ) has good impact toughness, and the steel can be used in shipbuilding, construction, offshore platforms, bridges, pressure Welded structures in fields such as containers and oil and gas pipelines. Background technique [0002] For shipbuilding, construction, offshore platforms, bridges, pressure vessels, and oil and gas pipelines, in recent years, steel with a plate thickness of more than 50mm and a parent material with a tensile strength ≥ 510MPa has been widely used. In order to improve the welding efficiency of these thick steel plates, large input energy, single-p...

AI Technical Summary

Problems solved by technology

However, titanium oxide has two major problems: the small amount and the difficulty of dispersing in steel.

If it is desired to increase the amount of titanium oxide by increasing the titanium content in the steel, it will inevitably lead to the formation of large titanium oxide inclusions

When the size of titanium oxide particles is greater than 5 μm, it will reduce the impact toughness of the base metal and welding heat-affected zone

Therefore, in the process of large input energy welding with welding input energy greater than 200kJ / cm, titanium oxide alone is still not enough to improve the toughness of the welding heat-affected zone

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