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ASTM A131 FH40 Shipbuilding Steel Plate | Grade F High-Strength Hull Steel for Ships & Offshore Engineering
ASTM A131 / A131M | Grade F — Charpy V-Notch Tested at −60 °C | Yield 390 MPa Min, Tensile 510–650 MPa, Elongation 19% (200 mm) / 22% (50 mm) | For Hulls, Offshore Drilling Platforms & Platform Pipe Joints
Top of the A131 Strength RangeFH40 is the highest strength level of the ASTM A131 higher-strength hull steel family — minimum yield point 390 MPa, tensile strength within 510–650 MPa.
Grade F — −60 °C ToughnessThe F designation requires the Charpy V-notch impact test at −60 °C, for hull and offshore structures working in the most demanding low-temperature service.
Specified Where Substitutes FailChosen where a lower-priced grade cannot satisfy the rules — offshore oil drilling platforms, ship hulls and platform pipe joints.
01Product Overview
ASTM A131 Grade FH40 is the highest strength grade of the A131/A131M higher-strength hull structural steel family. Its minimum yield point is 390 MPa and its tensile strength falls within 510–650 MPa. Because of its higher cost and the ready availability of cheaper substitute grades, FH40 is used less often than the AH and DH grades in ordinary hull work — it is specified where a project genuinely needs the top strength level combined with the grade F toughness class.
That combination is the whole point of the grade. Wherever a structure must carry high load and stay tough at −60 °C — offshore drilling platform components, hull structures of newbuild and repair vessels, and platform pipe joints — FH40 satisfies both requirements at once, and a lower grade cannot be substituted without re-qualifying the design.
390 MPaYield Strength (Min)ASTM A131 FH40
510–650 MPaTensile StrengthASTM A131 FH40
−60 °CImpact Test TemperatureGrade F designation
19 / 22 %Elongation (Min)200 mm / 50 mm gauge
02Technical Specifications
ASTM A131 Grade FH40 plate supplied to your drawing, with cutting, shaping and full marine certification handled on the same order.
Item
Specification Details
Steel Grade
ASTM A131 FH40 (A131 Grade FH40)
Executive Standard
ASTM A131 / A131M International Standard
Product Type
Grade F High-Strength Hull Structural Steel Plate
Dimensions
Produced to order — thickness, width and length confirmed against your drawing and the rolling schedule
Surface Condition
Smooth surface, uniform texture, no cracks, no rust spots
Delivery Condition
Confirmed per order and stated on the MTC As RolledNormalizedTMCPOther as agreed
Custom Production
Available — custom sizes, cutting and shaping to your drawings
MOQ
1 Ton / Negotiable
Delivery Time
Stock availability and rolling schedule confirmed on enquiry
Certification
MTC / EN 10204 3.1 / Classification society certificate (ABS, CCS, DNV, LR)
Payment Terms
T/T, L/C, Western Union, Trade Assurance
Note: ASTM A131 / A131M does not fix a single size range or delivery condition for FH40 — the applicable thickness, rolling schedule and heat treatment are agreed between buyer and mill for each order. Send us your required thickness, width, length and classification society and we will confirm stock status and the exact delivery condition against the item before you order.
03Grade Designation
Each segment of the grade name carries a defined meaning in ASTM A131 / A131M — and grade F is what separates FH40 from the AH, DH and EH grades.
Designation Segment
Meaning in ASTM A131 / A131M
F
Grade F — the lowest impact test temperature of the four quality levels (A = 0 °C, D = −20 °C, E = −40 °C, F = −60 °C)
Specified minimum yield point in kgf/mm² — 40 kgf/mm² ≈ 390 MPa
Note: The F tells you the Charpy V-notch test temperature (−60 °C) and the 40 is the yield point expressed in kgf/mm² (40 kgf/mm² ≈ 390 MPa), which is exactly the minimum yield value given in the mechanical table — a useful cross-check when you read a mill certificate. The designation breakdown above is standard background for this grade family.
04Equivalent & Classification Society Grades
For global shipbuilding and offshore project bidding, ASTM A131 FH40 has matching grade-F equivalents under the major classification societies, so one grade level can be procured across standards.
Standard System
Equivalent Grade
Note
ABS Standard
ABS FH40
American Bureau of Shipping approval for hull structures
CCS Standard
CCS FH40
China Classification Society approval
DNV Standard
DNV FH40
Det Norske Veritas approval
LR Standard
LR FH40
Lloyd’s Register approval
Other IACS societies
BVKRNKRINA
FH40 approvals of the remaining IACS members are available on request
Note: Equivalent grade-F grades differ slightly in chemical composition and production process. Verify welding parameters and inspection standards against your actual ship classification requirements before substituting one for another.
05Chemical Composition
Chemical composition for A131 FH40 ship steel — heat analysis, % max unless a range is given.
Grade
C
Si
Mn
P
S
Al (acid) min
Nb
V
Ti
Cu
Cr
Ni
Mo
N
A131 FH40
0.16
0.50
0.90–1.60
0.025
0.025
0.015
0.02–0.05
0.03–0.10
0.02
0.35
0.20
0.80
0.08
0.009
Note: FH40 tightens phosphorus and sulphur to 0.025% each and raises nickel to 0.80% — the nickel addition is what supports the −60 °C impact requirement, while the low P and S keep the weld heat-affected zone tough. Aluminium is given as a minimum (0.015%) because it acts as the grain refiner, and niobium and vanadium are the micro-alloying elements that develop strength without sacrificing weldability. Contents of any other intentionally added element are determined and reported.
06Welding Performance Parameters
Two indices are used to evaluate welding crack sensitivity and carbon equivalent for production and welding process guidance.
Note: Lower Pcm and Ceq mean better weldability and lower preheat demand. Both are calculated from the actual heat analysis of each plate, so we quote the values together with the MTC rather than as fixed numbers. Because FH40 carries the highest strength level of the A131 family, its carbon equivalent normally sits above the AH and DH grades — confirm preheat and interpass requirements against your welding procedure specification before fabrication.
07Mechanical Properties
Mechanical property for A131 FH40 shipbuilding structural steel, including tensile properties and the elongation requirement for both gauge lengths.
Grade
Yield Strength Min
Tensile Strength
Elongation Min (200 mm)
Elongation Min (50 mm)
Impact Test Temperature
Energy 1
Energy 2
A131 FH40
390 MPa
510–650 MPa
19 %
22 %
−60 °C
—
—
Note:Energy 1 is the transverse impact test, Energy 2 is the longitudinal. The data sheet for this grade specifies the tensile properties and both elongation values but no single Charpy energy figure — the applicable requirement changes with the plate thickness bracket and the classification society rule applied, so we confirm it from the mill certificate for your specific plate instead of printing one number that would not hold for every size. Tell us the thickness and the society and we will supply the exact value.
08Applications & Typical Components
ASTM A131 FH40 shipbuilding steel plates are mainly used for making the offshore oil drilling platform, the hull of ship building and ship repairing, the platform pipe joints and other components.
1
Offshore Drilling Platforms
Offshore oil drilling platform structures and the welded platform components that must hold strength together with grade F toughness.
2
Ship Hull Construction & Repair
Hull structures for ship building and ship repairing where the highest A131 strength level is called up by the design.
3
Platform Pipe Joints
Platform pipe joints and other components subject to combined high load and low-temperature service conditions.
Components designed to operate with a −60 °C impact requirement
Note: FH40 is specified where a project needs both the top yield level of the A131 family (390 MPa min) and grade F toughness (−60 °C). Where only one of the two is required, the lower AH, DH or EH grades usually give the more economical solution — send us the design temperature and the required strength and we will confirm which grade your project actually needs.
09Processing & Fabrication Services
Every order can be cut, formed and finished to your drawings, so material arrives at the yard ready to fit.
1
Cutting
Custom sizes and shapes cut to your drawings, plate and profile.
2
Bending & Forming
Plate bending and shaping for hull curvature and structural components.
3
Precision Finishing
Precision finishing so parts arrive ready to fit on the slipway.
4
Certified Delivery
MTC, EN 10204 3.1 and third-party marine inspection included with every shipment.
We supply high-quality ASTM A131 FH40 shipbuilding steel plates with strict marine standard inspection and full traceability. We provide one-stop customized processing services including cutting, bending and precision finishing. All products are equipped with official MTC test reports and marine certification documents. Welcome to contact us for professional quotations and technical support!
10Frequently Asked Questions
Short answers to the questions we are asked most often about ASTM A131 FH40. For anything not covered here, send us your drawings and specification.
Q1What does FH40 mean in ASTM A131?
F is the quality / toughness level — grade F requires the Charpy V-notch impact test at −60 °C. H means higher-strength hull structural steel. 40 is the specified minimum yield point in kgf/mm² (40 kgf/mm² ≈ 390 MPa). FH40 therefore combines the highest strength level of the A131 higher-strength family with the lowest impact test temperature.
Q2Why is FH40 used less often than the AH, DH and EH grades?
Because of its higher cost and the availability of cheaper substitutes. The AH, DH and EH grades cover 0 °C, −20 °C and −40 °C service respectively at lower strength and lower cost, so most ordinary hull work uses them. FH40 is specified where the design genuinely needs 390 MPa minimum yield and −60 °C toughness together — and there the lower grades are not an acceptable substitute.
Q3Can A131 FH40 be replaced by ABS FH40 / CCS FH40 / DNV FH40 / LR FH40?
These are the grade-F equivalents of the same strength and toughness level and are commonly accepted for cross-standard procurement and bidding. There are slight differences in chemical composition and production process, so verify welding parameters and inspection standards against your actual ship classification requirements before material replacement.
Q4What impact toughness does FH40 guarantee?
Grade F fixes the test temperature at −60 °C, tested as a Charpy V-notch specimen. Energy 1 is the transverse test and Energy 2 is the longitudinal test. The energy figure that applies depends on the plate thickness bracket and the classification society rule involved, so we confirm it from the mill certificate for your specific plate rather than quoting one number for every size.
Q5How is the chemical composition controlled, and how good is the weldability?
Heat analysis is capped at C 0.16, Si 0.50, Mn 0.90–1.60, P 0.025, S 0.025, Ni 0.80, Cu 0.35, Cr 0.20, Mo 0.08, N 0.009, with Nb 0.02–0.05 and V 0.03–0.10 as micro-alloying ranges and Al 0.015 min as grain refiner. Weldability is assessed with Pcm = (C + Si/30 + Mn/20 + Cu/20 + Ni/60 + Cr/20 + Mo/15 + V/10 + 5B)% and Ceq = [C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15]%; both depend on the actual heat, so we quote them from the MTC for your plate.
Q6What sizes, delivery conditions, payment terms and lead times do you offer?
FH40 plate is produced to order — thickness, width and length are confirmed against your drawing and the rolling schedule, and the delivery condition (as rolled, normalized, TMCP or as agreed) is stated on the MTC. Payment by T/T, L/C, Western Union or Trade Assurance, with MOQ 1 ton. Send your dimensions, quantity and classification society requirement and we will confirm stock availability and lead time for that exact item.
Get Your ASTM A131 FH40 Shipbuilding Steel Plate Quotation
Send us your plate dimensions (thickness / width / length), quantity, delivery condition and classification society requirement. We will reply with the latest stock status, competitive wholesale price and complete marine certification documents within 24 hours.
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