A thick steel plate with excellent toughness in low-carbon equivalent welding heat-affected zone and manufacturing method thereof

Abstract

The invention discloses a thick steel plate with a low carbon equivalent and excellent welding heat affected zone toughness and a manufacturing method of the same. The manufacturing method comprises the following steps: 1) smelting, refining and continuously casting the ingredients in the following percentage by mass: 0.045-0.075% of C, 0.10-0.30% of Si, 1.3-1.6% of Mn, not greater than 0.015% of P, 0.001-0.01% of S, 0.20-0.40% of Ni, 0.005-0.03% of Ti, 0.003-0.08% of Al, 0.0005-0.005% of Ca, not greater than 0.02% of REM, not greater than 0.02% of Zr, 0.0005-0.005% of B, 0.001-0.006% of N, 0.32-0.36% of Ceq, 0.0005-0.005% of Bef, and the balance of Fe and inevitable impurities; 2) rolling; and 3) cooling. According to the manufacturing method disclosed by the invention, inclusions with fine dispersed distribution can be formed, and by controlling the surface density of the micron inclusions with diameters of not less than 1 micron, Ca / Al ratio, the length-width ratio of the inclusions and the surface density of the submicron inclusions with diameters of less than 1 micron, the tensile strength of the base material is not less than 510 MPa, the weld heat input is 200-400 kJ / cm, and the average Charpy impact energy of a welding heat affected zone at minus 40 DEG C is greater than 100 J, therefore, excellent impact toughness is achieved.

Description

technical field [0001] The invention belongs to the field of iron and steel metallurgy and iron and steel materials, and particularly relates to a thick steel plate with excellent toughness in the heat-affected zone of low-carbon equivalent welding and a manufacturing method thereof. The energy is 200-400kJ / cm, and the average Charpy impact energy in the welding heat-affected zone at -40°C is above 100J. It has excellent impact toughness in the welding heat-affected zone (HAZ). The steel can be used in shipbuilding, construction, offshore platforms, Welded structures in fields such as bridges, pressure vessels, 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 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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