Description: BBN steel is a well-known steel manufacturer and service provider in China, ASTM A131 Grade A steel plate is our superior product, we are favored by customers with high quality, competitive price and excellent service
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ASTM A131 Grade A is an ordinary-strength (general strength) hull structural steel plate with a minimum yield point of 235 MPa and a tensile strength within 400–520 MPa. It is the base level of the ASTM A131 / A131M shipbuilding family — a plain carbon–manganese plate specified where the hull section is designed around 235 MPa rather than around the 315 / 355 / 390 MPa higher-strength levels.
Under the steel specification ASTM A131 / A131M, marine steel plate and sheet of grade A is mainly used for built hull of vessels, ship body construction. Because no "H" appears in the name, grade A is not a high-strength grade: it carries the same 235 MPa minimum yield as grades B, D and E of the ordinary-strength group, and those four levels are separated from each other by the impact test temperature rather than by strength. If your section needs more strength per millimetre, the A131 higher-strength grades (AH32 / AH36 / DH36 / EH36 and up) are the correct call-up instead of a thicker grade A plate.
235 MPaYield Strength (Min)ASTM A131 Grade A
400–520 MPaTensile StrengthASTM A131 Grade A
21 %Elongation (Min)All three thickness brackets
Degree 20Impact Test TemperatureSource data sheet, Degree column
02Technical Specifications
ASTM A131 Grade A plate supplied to your drawing, with cutting, forming, blast cleaning and marine certification handled on the same order.
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
Up to and including 40 mm: as rolled or control rolled. Above 40 mm: normalized or TMCP As RolledControl RolledNormalizedTMCP
Heat Treatment Note
For thickness above 40 mm the plate is normalized or thermo-mechanically rolled — both raise the yield and tensile values of the plate
Custom Production
Available — custom sizes, cutting and shaping to your drawings
MOQ
1 Ton / Negotiable
Lead Time
1 – 10 t: 5 days · 10 – 50 t: 10 days · > 50 t: negotiable (stock and rolling schedule confirmed on enquiry)
Certification
MTC / EN 10204 3.1 / Classification society certificate (ABS, CCS, DNV, LR)
Payment Terms
L/C, T/T, D/P, Western Union, Paypal, Money Gram
Note: The source data sheet for this product gives the delivery condition rule and the 40 mm thickness boundary, but it does not publish a width or length range — so no size range is printed here. Send us your required thickness, width, length, quantity and classification society and we will confirm stock status, the applicable delivery condition and the rolling slot against the item before you order. The quantity brackets above are the published schedule; they are estimates, not a contractual lead time.
03Grade Designation
Grade A is named differently from the AH / DH / EH / FH grades you may be comparing it with — the letter is a strength category, not a temperature code plus a kgf/mm² number.
Designation Segment
Meaning in ASTM A131 / A131M
A131
The ASTM specification for structural steel for ships — hull plate, sheet and sections surveyed under classification society rules
Grade A
The ordinary-strength category. There is no "H" in the name, so this is not a higher-strength grade, and there is no kgf/mm² number in the name — the strength level is read from the standard's mechanical table, not from the designation
235 MPa
The minimum yield point the grade must meet, taken from the mechanical property table rather than from the grade name
A131/A
The short mill / trading notation for the same grade — you will see both "Grade A" and "A131/A" on certificates and inquiries
Note: The quickest way to read an A131 grade is to look for the H. Grade A / B / D / E (no H) are the ordinary-strength levels at 235 MPa, separated by impact test temperature; AH32 / AH36 / AH40 / DH36 / EH36 / EH40 and the rest are the higher-strength levels, where the number is the minimum yield in kgf/mm² (32 ≈ 315, 36 ≈ 355, 40 ≈ 390 MPa). That is why "Grade A" and "AH40" must never be read as two versions of the same thing — the first is a 235 MPa plate, the second a 390 MPa plate. The designation explanation above is standard background for this grade family.
04Equivalent & Classification Society Grades
For global shipbuilding and repair bidding, ASTM A131 Grade A has matching grade-A equivalents under the major classification societies, so the same strength level can be procured across standards.
Standard System
Equivalent Grade
Note
ABS Standard
ABS Grade A
American Bureau of Shipping approval for ordinary-strength hull structures
CCS Standard
CCS Grade A
China Classification Society approval
DNV Standard
DNV Grade A
Det Norske Veritas approval
LR Standard
LR Grade A
Lloyd’s Register approval
Other IACS societies
BVKRNKRINA
Grade A approvals of the remaining IACS members are available on request
Note: Equivalent grade-A 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/A ship steel — heat analysis, % max as published in the source data sheet.
Grade
C
Si
Mn
P
S
C+Mn/6
A131/A
0.21
0.50
2.5 × C
0.035
0.035
0.40
Note: Carbon is capped at 0.21% and phosphorus and sulphur at 0.035% each. Manganese is given as 2.5 × C rather than as a fixed number — the permitted manganese follows the actual carbon of the heat, so the two must be read together on the certificate. The C + Mn/6 ≤ 0.40% column is the carbon-equivalent style control that keeps the plate weldable. The source data sheet publishes only these six items; it does not list the micro-alloying or residual elements (Nb, V, Ti, Al, Cu, Cr, Ni, Mo, N), so no value is printed for them here — where a project or a classification society sets a cap on any of them, it is stated on the mill certificate.
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. As an ordinary-strength carbon–manganese grade, A131 Grade A sits at the easy-to-weld end of the shipbuilding range — but the plate above 40 mm is delivered normalized or TMCP to reach its strength, so confirm preheat and interpass control against your welding procedure specification for those thicknesses.
07Mechanical Properties
Mechanical property for A131 Grade A shipbuilding structural steel, given by plate thickness bracket together with the Charpy V-notch impact column of the source table.
Grade
Thickness
Yield Strength Min
Tensile Strength
Elongation Min
Impact Test Temperature (Degree)
Energy 1 (Transverse)
Energy 2 (Longitudinal)
A131/A
t ≤ 50 mm
235 MPa
400–520 MPa
21 %
20
—
—
A131/A
50 < t ≤ 70 mm
235 MPa
400–520 MPa
21 %
20
—
—
A131/A
70 < t ≤ 100 mm
235 MPa
400–520 MPa
21 %
20
—
—
Note:Energy 1 is the transverse impact test and Energy 2 is the longitudinal impact test. Strength and elongation are identical across the three published brackets — 235 MPa minimum yield, 400–520 MPa tensile and 21% minimum elongation. The Degree column of the source table reads 20 with no unit printed on it; on the same column of the mill data sheets for the sibling ordinary-strength grades the values run −20 and −40, so it is read here as degrees Celsius — we print the number as published and leave the unit to your specification. All three energy cells are blank in the source table, so they are left blank here rather than filled with a value the source does not support. Thickness above 100 mm is not covered by the published table and is confirmed on enquiry. Tell us the thickness and the classification society and we will confirm the applicable requirement from the mill certificate for your specific plate.
08Applications & Typical Components
Under ASTM A131 / A131M, marine steel plate and sheet of grade A is mainly used for built hull of vessels, ship body construction.
1
Hull Shell & Bottom Plating
Shell plating, bottom and side shell, bilge strakes — the general-strength envelope of barges, workboats and inland or warm-water vessels.
2
Ship Body Structure
Internal structure of the ship body: bulkheads, frames and stringers, decks of general-strength vessels, tank tops and non-critical hull members.
3
Shipyard Repair & General Fabrication
Normal repair work in shipyards, renewal plate, brackets, foundations and general marine fabrication where a 235 MPa plate is what the drawing calls for.
Application Field
Typical Application & Components
Hull Construction
Hull of vessels — shell plating, bottom plating, side shell, bilge strake
Ship Body Structure
Bulkheads, frames, stringers, decks of general-strength vessels, tank tops
Shipyard Repair & Fabrication
Repair and renewal plate, brackets, seatings and general marine fabrication
Note: Grade A earns its 235 MPa without any low-temperature toughness margin built into the designation. Where the structure has to hold toughness below room temperature, the ordinary-strength siblings are the ones to look at — ASTM A131 Grade B, ASTM A131 Grade D and ASTM A131 Grade E sit at the same 235 MPa level and are separated from grade A by their impact test temperature. Where the section is limited by strength instead, move up to a higher-strength grade such as AH32, AH36, DH36 or EH36. 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, blast cleaned, coated and independently inspected, 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 sections and structural components.
3
Shot Blasting & Painting
Plate pre-treatment — shot blasting and painting with shop primer — applied before shipment.
4
Inspection & Certified Delivery
MTC and EN 10204 3.1 with every shipment; UT, Z-direction test and third-party inspection (SGS) arranged on request.
We supply high-quality ASTM A131 Grade A shipbuilding steel plates with strict marine standard inspection and full traceability. We provide one-stop customized processing services including cutting, bending and forming, plus shot blasting, priming or coating to your surface specification. All products are equipped with official MTC test reports and marine certification documents, and UT, Z-direction and third-party (SGS) testing can be arranged on request. BBN Group is one of the leading manufacturers, suppliers and exporters of ASTM A131 Grade A plates — welcome to contact us for professional quotations and technical support!
Short answers to the questions we are asked most often about ASTM A131 Grade A. For anything not covered here, send us your drawings and specification.
Q1What does Grade A mean in ASTM A131?
It is the ordinary-strength category of the specification. Unlike AH32 / AH36 / AH40, there is no H and no number in the name, so the grade name carries no kgf/mm² figure — the 235 MPa minimum yield comes from the standard's mechanical table, not from the designation. You will also see the same plate written A131/A on mill paperwork.
Q2What is the difference between Grade A, Grade B, Grade D and Grade E?
All four are ordinary-strength A131 grades at the same 235 MPa minimum yield and 400–520 MPa tensile — what separates them is the impact test temperature band they are specified for, with grade A at the warm end of the group. See ASTM A131 Grade B, ASTM A131 Grade D and ASTM A131 Grade E. If your design temperature is below room temperature, specify the level that carries the matching test temperature rather than assuming grade A covers it.
Q3What is ASTM A131 Grade A mainly used for?
Under ASTM A131 / A131M, marine plate and sheet of grade A is mainly used for built hull of vessels, ship body construction — shell and bottom plating, bulkheads, frames, stringers and decks of general-strength vessels, plus normal shipyard repair and general marine fabrication.
Q4What impact toughness does A131 Grade A guarantee?
The source data sheet reports the Degree column as 20 with no unit printed, and leaves Energy 1 (transverse) and Energy 2 (longitudinal) blank for all three thickness brackets. We therefore print the temperature as published and leave the energy cells empty rather than quoting a joule value the source does not give. Tell us the thickness bracket and the classification society and we will confirm the applicable requirement from the mill certificate for your specific plate.
Q5What sizes, delivery conditions and lead times can you supply?
Plate is produced to order — thickness, width and length are confirmed against your drawing and the rolling schedule. Up to and including 40 mm the plate is supplied as rolled or control rolled; above 40 mm it is normalized or TMCP, both of which raise the yield and tensile values. The published quantity schedule is 1 – 10 t: 5 days, 10 – 50 t: 10 days, > 50 t: negotiable. MOQ is 1 ton, payment is by L/C, T/T, D/P, Western Union, Paypal or Money Gram, and every shipment carries an MTC / EN 10204 3.1 certificate.
Q6Can A131 Grade A be substituted by ABS / CCS / DNV / LR Grade A?
These are the ordinary-strength grade-A equivalents of the same strength 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. Tell us which classification society your project is surveyed under and we will supply the plate with the matching certificate.
Get Your ASTM A131 Grade A 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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