A kind of high-homogeneous large-size ultra-high-strength steel ingot and its manufacturing method

Abstract

The invention relates to a highly-homogeneous large-scale ultrahigh-strength steel ingot and a manufacturing method thereof. The highly-homogeneous large-scale ultrahigh-strength steel ingot comprises the following chemical components in percent by weight: 0.29-0.36 percent of C, 0.50-1.50 percent of Mn, 1.20-2.50 percent of Si, 0.9-1.20 percent of Cr, 5.00-6.00 percent of Ni, 0.50-1.00 percent of Mo, not more than 0.35 percent of V, not more than 0.04 percent of Nb, not more than 0.005 percent of S, not more than 0.01 percent of P, not more than 20ppm of O, not more than 25ppm of N and the balance of Fe and inevitable impurities. The steel ingot can be forged into a steel bar with the diameter of 400mm-500mm, and the longitudinal mechanical properties of the steel bar are as follows: Rm is more than or equal to 1800MPa, Rp0.2 is more than or equal to 1470MPa, A is more than or equal to 10 percent, Z is more than or equal to 44 percent, and Aku is more than or equal to 60J at a temperature of 20 DEG C; and the ratio of the transverse mechanical properties to the longitudinal mechanical properties is more than 92 percent and reaches a highly-homogeneous requirement; white spot, dark spot, radial segregation and annular ring segregation of a macrostructure of the steel ingot respectively reach AAAB levels and are superior to the qualified level of a macrostructure inspected by ASTMA604-93; and the diameter phi of the steel ingot ranges from 760mm to 920mm.

Description

technical field [0001] The invention relates to the field of ultra-high-strength steel metallurgy, in particular to a high-homogeneity large-size ultra-high-strength steel ingot and a manufacturing method thereof. The longitudinal mechanical properties of the steel ingot forged into a steel rod with a diameter of ∮400mm-500mm: R m ≥1800MPa, R p0.2 ≥1470MPa, A≥10%, Z≥44%, A at 20°C ku ≥60J, the ratio of transverse mechanical properties to longitudinal mechanical properties reaches over 92%, meeting the requirement of high homogeneity, and the white spot, dark spot, radial segregation and annual ring segregation in the low-magnification tissue respectively reach AAAB level, excellent It is based on the low-power tissue qualification level tested according to ASTMA604-93. Background technique [0002] Ultra-high-strength steel is divided into low-alloy ultra-high-strength steel, maraging steel, and secondary hardening steel. The general strength is greater than 1400MPa, and t...

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Problems solved by technology

[0009] Existing related patents, such as the new cobalt-free high-strength and high-toughness steel G50 of Chinese patent CN102212760A, the chemical composition (wt.%) of this steel is: C: 0.26-0.30, Mn: 0.40-0.75, Si: 1.70-2.10 , Cr: 0.90-1.20, Ni: 4.3-4.86, Mo: 0.50-0.70, Nb: 0.02-0.04, tensile strength ≥ 1680MPa, impact toughness ≥ 60J, but it only trial-produced steel bars smaller than ∮ 320mm, which does not belong to Heavy gauge steel bar grade, the homogeneity of heavy gauge steel bars produced with this composition cannot be predicted

The hardenability of 30CrMnSiNi2A steel cannot meet the requirements of ≥∮400mm steel bars, and the strength cannot meet the requirements

There is no relevant information and report on high homogeneous steel in foreign countries

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