Thick-walled high-toughness high-tensile steel plate and manufacturing method thereof

Abstract

The present invention provides a thick-walled, high-toughness, high-tensile steel sheet excellent in strength and toughness at the central portion of the sheet thickness, and a method for producing the same. A thick-walled steel plate having a specific composition, the average prior-austenite particle size of the microstructure throughout the entire thickness direction of the plate is 50 μm or less, and the area fraction of the martensite and / or bainite structure is 80 %above. After heating the continuously cast slab with the above-mentioned specific composition to 1200°C to 1350°C, hot working is performed with a strain rate of 3 / sec or less and a cumulative reduction ratio of 15% or more, followed by hot rolling and heat treatment.

Description

technical field [0001] The present invention relates to a thick-walled, high-toughness, high-tensile steel plate with excellent strength, toughness, and weldability that can be used in steel structures such as buildings, bridges, shipbuilding, marine structures, construction and industrial machinery, tanks, and gates, and a manufacturing method thereof. Preferably, it is a steel plate having a plate thickness of 100 mm or more and a yield strength of 620 MPa or more. Background technique [0002] In recent years, the increase in size of steel structures has been remarkably advanced, and the high-strength and thick-walled steel materials used have also been remarkably advanced. Generally, a large steel ingot produced by an ingot casting method is rough-rolled, and the obtained bloom slab is then hot-rolled to manufacture a thick steel plate having a plate thickness of 100 mm or more. However, the thick segregation portion at the hot top and the negative segregation portion a...

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Problems solved by technology

However, the thick segregation part at the hot top and the negative segregation part at the bottom of the ingot must be cut off and discarded in this ingot-blooming process, so the yield is reduced, the manufacturing cost is increased, and the construction period is extended.

[0003] On the other hand, in the process of using continuous casting slabs as raw materials, although there is no such concern, since the thickness of continuous casting slabs is smaller than that of ingot casting slabs, the reduction rate until the thickness of the product is small, and it is necessary to increase the strength and thickness of steel materials. In the case of walling, the amount of alloying elements added to ensure the necessary properties increases, causing problems such as center porosity due to center segregation, and internal quality deterioration due to enlargement.

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