A kind of thick steel plate for welding with low carbon equivalent and large input energy and its manufacturing method

Abstract

The invention relates to a low-carbon-equivalent large heat input welding thick steel plate and a preparation method thereof. The preparation method comprises the following steps: 1) smelting and casting, wherein the steel plate comprises the following components in percentage by weight: 0.045-0.07% of C, 0.10-0.30% of Si, 1.3-1.6% of Mn, less than or equal to 0.015% of P, 0.001-0.01% of S, 0.2-0.4% of Ni, 0.005-0.035% of Ti, 0.0005-0.01% of Mg, 0.001-0.01% of N, 0.0005-0.005% of B, less than or equal to 0.05% of Al, less than or equal to 0.05% of Ca, less than or equal to 0.02% of REM and the balance of Fe and inevitable impurities and further comprises more than one of less than or equal to 0.03% of Nb or less than or equal to 0.2% of Cr; Ti / N is greater than or equal to 2 but less than or equal to 6, Mg / (Al+Ti) is greater than or equal to 0.024, Ceq is 0.32-0.36% and Bef is 0.0005-0.005%; 2) rolling; 3) cooling. By controlling the (Mg+Ca) / (Al+Ti) ratio and areal density of micron inclusions with the diameter which is greater than or equal to 1 micron as well as the (Mg+Ca) / (Al+Ti) ratio and areal density of submicron inclusions with the diameter which is 0.1-1 micron, for the steel plates with the thickness being 50-70 mm and the base material tensile strength being greater than or equal to 510 MPa, the steel plates are welded with the weld heat input of 200-400kJ / cm, and the average Charpy impact energy of a welding heat affected zone at -40 DEG C reaches 100J above.

Description

technical field [0001] The invention relates to the field of manufacturing thick steel plates for welding, in particular to a thick steel plate for welding with low carbon equivalent and large heat input and a manufacturing method thereof. For a steel plate with a plate thickness of 50-70mm and a base metal tensile strength ≥ 510MPa, under the condition of a welding line energy of 200-400kJ / cm, the welding heat-affected zone of the steel plate has good impact toughness. The Charpy impact energy is above 100J. The thick steel plate can be used as a welded structural material in the fields of ships, buildings, marine structures and the like. Background technique [0002] In recent years, with the enlargement of welded structures such as shipbuilding, construction, pressure vessels, oil and gas pipelines, and offshore platforms, it is increasingly required to improve the large heat input welding performance of thick steel plates, which can improve welding efficiency, shorten m...

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, it is still difficult to improve the toughness of the welding heat-affected zone by titanium oxide alone.

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