Chemical element composition of Chinese grade ultra-high strength marine steel plate FH550
FH550 Approaching Steel Plate Grade Lookup Table

FH550  Chemical composition

Grade Delivery status Chemical composition (mass fraction)/%
C Si Mn P" S" Cu Cr Ni Nb Vb Ti Mo N Alt
FH550 QT ≤0.18 ≤0.80 ≤1.70 ≤0.020 ≤0.010 ≤0.50 ≤1.50 ≤2.00 ≤0.06 ≤0.12 ≤0.05 ≤0.70 ≤0.015 ≥0.018
“The P and S content of the structural steel is allowed to be 0.005% higher than the values ​​specified in the table.

Except for quenched and tempered steel, Nb+V+Ti ≤ 0.26% and Mo+Cr ≤ 0.65%.

With the consent of both the supplier and the buyer, the Ni content may be appropriately increased.

The minimum ratio of total aluminum to nitrogen should be 2:1. When other nitrogen-fixing elements are used, the minimum aluminum content and aluminum-nitrogen ratio are not required.

Oxygen content [O] ≤50×10⁶.

‘Oxygen content [O] ≤ 30 × 10⁶.

When boron is intentionally added to enhance the hardenability of steel, the boron content should not exceed 0.005%.

FH550  Mechanical properties

Steel grade Delivery status Tensile test，b,e Charpy (V-notch) impact test
Upper yield strength(RH)/

MPa		 Tensile strength(Rm)/

MPa		 Elongation after fracture(A)/% Test temperature/℃ Impact absorption energy(KV₂)/J
Thickness / m m
3～50 >50~100 >100~250 3～100 >100~250 Horizontal Vertical Vertical Horizontal
FH550 TM、QT ≥550 ≥530 ≥490 640~820 590~770 ≥16 ≥18 -60  ≥55 ≥37
For sheet metal tensile and impact tests, transverse specimens are used; for profiles and bars, longitudinal specimens are used.

When the yield strength is not obvious, the specified plastic elongation strength Rp0.2 can be measured instead of the upper yield strength.

°If required by the buyer, the yield strength ratio may be no greater than 0.94, subject to negotiation between the supplier and the buyer and specified in the contract.