High toughness and high tensile strength thick steel plate with excellent material homogeneity and production method for same

Abstract

A high tensile strength thick steel plate of excellent strength, elongation and toughness of the mid-thickness part and excellent material homogeneity is provided by: heating a continuously cast slab, the components of which have been adjusted to a prescribed composition, to 1200-1350 DEG C and then hot casting under conditions of temperature: at least 1000 DEG C, strain rate: not more than 3 / s, and cumulative rolling reduction: at least 15% using a mold in which the opposing short sides of the mold differ and, when the length of the shorter short side is 1, the length of the longer short side is 1.1-3.0; then allowing the slab to cool to obtain a steel raw material; after heating said steel raw material again to the Ac3 point-1250 DEG C and then performing at least two passes of hot-rolling in which rolling reduction per single pass is at least 4%, allowing the steel to cool to obtain a thick steel plate; and after heating again to the Ac3 point-1050 DEG C and then cooling rapidly to 350 DEG C or less, tempering said thick steel plate at 550-700 DEG C.

Description

technical field [0001] The present invention relates to a thick steel plate suitable for steel structures such as buildings, bridges, shipbuilding, marine structures, construction machinery, tanks, and pressure water pipes, which is excellent in strength, elongation, toughness, and material uniformity in the thickness direction and its manufacturing method. [0002] In particular, the present invention relates to a thick-walled, high-toughness, high-tensile steel sheet having a thickness of 100 mm or more, having a yield strength of 500 MPa or more in the central portion of the thickness, and a reduction in area caused by tension in the thickness direction of the central portion of the thickness being 40% or more, and the low-temperature toughness at -60°C at the central part of the plate thickness is 70J or more. [0003] In the present invention, excellent material uniformity means that the hardness difference in the plate thickness direction is small. Background techniqu...

AI Technical Summary

Problems solved by technology

However, in this ingot-slab casting process, the concentrated segregation part at the riser and the negative segregation part at the bottom of the ingot must be cut off, so there is a problem that the yield is not improved, but the manufacturing cost is increased and the construction period is lengthened.

[0006] On the other hand, when a thick-walled steel plate having a thickness of 100 mm or more is produced by a process using a continuous casting slab as a raw material, there is no concern as described above, but since the thickness ratio of the continuous casting slab is used The thickness of the slab produced by the ingot method is small, so there is a problem that the amount of reduction to the product thickness is small

In addition, in recent years, there is a general tendency to demand higher strength and thicker steel materials, and the amount of alloying elements added to ensure the required properties has increased. As a result, center porosity due to center segregation has occurred. Deterioration of internal quality due to upsizing is a new issue

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