ASTM A709 Low Alloy Structural Steel

ASTM A709 is the industry gold standard for bridge construction.

 

At GNEE STEEL, we provide high-performance A709 plates and shapes designed to ensure the safety and longevity of your structural projects. Build with confidence-build with GNEE.

 

 

ASTM A709 is the standard specification for structural steel used primarily in the construction of bridges. It covers high-strength, low-alloy (HSLA) steel shapes, plates, and bars.

 

Unlike standard structural steel, A709 is specifically engineered to handle the dynamic loads and environmental stresses unique to bridge engineering, including requirements for notch toughness (Charpy V-notch testing).

 

It is available in several grades, including Grade 36, 50, 50W, 70W, 100, and HPS (High-Performance Steel) varieties.

 

The chemical makeup of ASTM A709 varies by grade to optimize weldability and atmospheric corrosion resistance.

Grade	Carbon (max %)	Manganese (%)	Phosphorus (max %)	Sulfur (max %)	Silicon (%)
Grade 36	0.25 - 0.29	---	0.04	0.05	0.40
Grade 50	0.23	1.35	0.04	0.05	0.40
Grade 50W	0.19	0.80 - 1.35	0.04	0.05	0.30 - 0.65
HPS 70W	0.11	1.10 - 1.50	0.02	0.006	0.30 - 0.50

Note: Grade 50W and HPS grades contain additional alloying elements like Copper, Chromium, and Nickel for enhanced corrosion resistance.

 

 

ASTM A709 is categorized by its yield strength (ksi).

Grade	Yield Strength (min ksi)	Tensile Strength (ksi)	Min. Elongation (%)
Grade 36	36	58 - 80	20%
Grade 50 / 50W	50	65 - 70	18%
Grade 70W / HPS 70W	70	85 - 110	19%
Grade 100 / 100W	100	110 - 130	18%

 

 

 

GNEE Steel stocks the following standard sizes, but other sizes may be available for special orders.

GRADE	THICKNESS	WIDTH	LENGTH
36	3/16" – 4"	48" – 120"	Up to 480"
50	3/16" – 4"	48" – 120"	Up to 480"
50W	3/16" – 4"	48" – 120"	Up to 480"
HPS 50W	3/16" – 4"	48" – 120"	Up to 480"
HPS 70W	3/16" – 4"	48" – 120"	Up to 480"

 

 

High Strength-to-Weight Ratio: Reduces the total weight of the structure, allowing for longer spans and reduced foundation costs.

 

Atmospheric Corrosion Resistance: "W" grades (like 50W) develop a protective "patina," eliminating the need for painting and reducing maintenance costs.

 

Fracture Toughness: Mandatory Charpy V-notch testing ensures the steel performs reliably under impact and in cold climates.

 

Excellent Weldability: Optimized chemical composition allows for easy on-site or shop welding without compromising structural integrity.

 

 

ASTM A709 is the "bridge steel" of choice for:

• Highway & Railway Bridges: Girders, trusses, and support beams.
• Pedestrian Bridges: Durable and aesthetically pleasing (weathering steel).
• Overpasses & Interchanges: High-load structural components.
• Marine Structures: Piers and coastal infrastructure (using weathering grades).

 

 

Internal Comparison (Within A709)

Grade 50 vs. 50W: Grade 50 is standard HSLA steel; 50W (Weathering) contains extra alloys to resist rust.

HPS (High Performance Steel): HPS 70W offers higher toughness and better weldability than standard 70W.

 

Equivalent Grade Comparison

ASTM A709 Grade	Equivalent Standard Steel	Key Difference
A709 Grade 36	ASTM A36	A709 has stricter toughness requirements for bridges.
A709 Grade 50	ASTM A572 Grade 50	Very similar, but A709 is bridge-certified.
A709 Grade 50W	ASTM A588	Identical chemistry; A709 specifies bridge-specific testing.

 

 

Can ASTM A709 be used for non-bridge applications?
Yes, it is often used in heavy equipment and buildings where high strength and weathering properties are required.

 

Is painting necessary for A709 Grade 50W?

Generally, no. Grade 50W is designed to be left unpainted, as the stable rust layer protects the steel.

 

What is the difference between A709 and A572?
While they share chemical properties, A709 requires Charpy V-notch impact testing to ensure it won't crack under the dynamic loads of moving vehicles on a bridge.

 

What is grade A709 steel?

The ASTM A709 is the Standard Specification for Structural Steel for Bridges and encompasses carbon, high-strength low-alloy, and quenched and tempered alloy steels used as structural plates in the construction of bridges. GNEE offers the following five grades of A709; 36, 50, 50W, HPS 50W and HPS 70W.

 

What is the difference between A36 and A709?

ASTM A709 grade 36 is a bridge material wherein carbon adds to the strength and hardenability of the steel. A36 has less than0. 30% carbon and thus, do not possess high hardenability. ASTM A709 grade 36 steel plate has improved corrosion resistance and can be used in outdoor applications.

 

What is the difference between A709 and A572 steel?

Summary: A572 Grade 50 is a general-purpose structural steel, while A709 Grade 50 is specifically engineered for bridge construction with stricter requirements for toughness, weldability, and quality control

 

Is A709 weathering steel?

Weathering steels are a family of ASTM specifications, as well as several trademarked specifications exhibiting similar corrosion resistant properties. The ASTM specifications are A588, A242, A606-4, A847, A871-65 and A709-50W.

 

 

Extensive Inventory: We carry a full range of thicknesses and grades (36 to HPS 100W).

Precision Processing: On-site laser, plasma, and flame cutting to your exact specifications.

Certified Quality: All products come with Mill Test Certificates (MTC) according to EN 10204 3.1.

Global Logistics: Decades of experience exporting to over 70 countries with sea-worthy packaging.

 

 

When it comes to bridge engineering, there is no room for compromise. ASTM A709 provides the specific mechanical and chemical properties needed to ensure public safety and structural endurance.

 

Whether you need standard carbon bridge steel or high-performance weathering steel, GNEE STEEL is your trusted partner.

[CONTACT US TODAY FOR A QUOTE]

 

Looking for the best price on ASTM A709 Steel?

GNEE STEEL offers competitive pricing and expert technical support for projects of all sizes.
📧 Email: alloy@gneesteelgroup.com
📞 WhatsApp/Phone: +86-372-5055135
 

Relying on many first-class equipment, such as CNC Shearing machine, Press Brake machine, Straightening machine, Roll Bending machine, Flat Bar Machine, Deburring machine etc, GNEE STEEL could provide various semi-productsand extensive forming services to customers.

 

GNEE STEEL  PROCESSING

1.CTL & SL SERVICE (141 SETS)

Currently, GNEE STEEL has imported manyadvanced CTL/SL equipment from Italy and Korea and could provide customized CTL/SL services from cold rolled stainless steel and carbon steel to hot rolled stainless steel and carbon steel as well as strips and ultra-wide sheet.

CTL FACILITIES
Max Length:16500mm

Max Width:2200mm

Max Thickness:25.4mm

Max Yield Strength:1500Mpa
SL FACILITIES

Max Width:2200mm

Max Thickness:18mm

Max slit Quantity:31

Max Yield Strength:1200Mpa

 

2.CUTTING SERVICE

GNEE STEEL imported lots of advanced cutting machines from Germany, Sweden, America and Japan, including plasmas cutting machine, water jet cutting machine, laser cutting machine, flame cutting machine and saw machine. In order to meet customers' diversified needs, GNEE STEEL also adopts nest working multi-cutting methods and intensive production to improve production capacity and save costs for the customers.

Laser Cutting Machine

Max Cutting Length:40,000mm

Max Width:4,600mm
Max Thickness:100mm

 

Flame Cutting Machine

Max Cutting Length:40,000mm

Max Width:8,000mm
Max Thickness:500mm

Plasmas Cutting Machine

Max Cutting Length:30,000mm

Max Width:5,000mm
Max Thickness:100mm

 

Water-jet Cutting

Max Cutting Length:12,000mm

Max Width:4,010mm
Max Thickness:250mm

3.FORMING SERVICE

Steel Plate Roll Bending
Maximum Rolling Thickness: up to 200mm
Maximum Width: 4200mm

   

Automatic Bending Machine-Press Brake
Max Bending Capability:3000Ton
Max Bending Length:15,000mm

Expert in Bending High-Strength & Wear-Resistant Steels

  

  

Punching Machine

Max Width:3,070mm
Max Thickness:8mm

Max Pressure:250t

BEVELING SERVICE

GNEE STEEL beveling platform has edge milling machine, edge planer, flame / plasma groove cutting machine, flame groove cutting robot, desktop chamfering machine, gantry planerand other advanced equipment to provide customers with parts prefabrication services,daily processing of V-type, Y-type, X-type and U-type grooves, and guarantee subsequent processes such as welding and assembly of products.

 

Milling：
Max Cutting Length:18,000mm

Max Width:4500mm
Max Thickness:120mm

 

  

Beveling:
Max Length:16,000mm

Max Thickness:80mm

MACHINING SERVICE

GNEE STEEL owns CNC Portal-type Boring and Milling machine,CNC Floor-type Boring and Milling machine, Vertical Precision 5-axis Milling Machine, Portal-type Planer, Vertical Lathe, Cylindical Grinding machine, Hydraulic Planer and CNC Lathe and could provide fine machining of large spare parts and structural parts for customers.

Gantry Type Boring & Milling Maching Center

Max Length:48000mm

Max Width:12500mm
Max Height:8000mm

Max Diameter:10500mm

Deep-hole Drilling Equipment
Max Driling Depth:1,100mm
Max Bore Diameter:φ80mm
Max Diametar:φ4,500mm

MMulti-hole Drilling Equipment

Max Length:13,000mm
Max Width:10,000mm
Max Bore Diameter:φ105mm
Max Drilling Depth:250mm

Floor Boring And Milling Machine
Max Length:24,000mm
Max Height:8,000mm
Turntable Dimensions:9x5m

Vertical Lathe

Max Height:6,000mm

Max Diametar:φ22,00mm

Automated Edge Milling Machine

The Automated Edge Milling Machine is a leading product in heavy-duty milling equipment. It is primarily used for weld groove preparation (beveling) on large-format plates made of stainless steel, carbon steel, and special steel grades. It can process plates with a maximum thickness of up to 90mm, a length of 16 meters, and a width of 4 meters.

 

It is equipped with dual milling units and a fully automatic milling cutter head changing system, enabling automated 4-edge beveling. Its standout feature is the profiling technology used when milling wavy plates and irregularly shaped products, which ensures absolute consistency of the groove after milling.

 

Utilizing specially designed milling cutter heads, it can execute highly difficult and complex groove profiles in a single pass.

 

Materials: Plain carbon steel, pressure vessel steel, wear-resistant steel, high-strength steel, stainless steel, nickel-based alloys, etc.
Width: 1200 - 4200 mm
Length: 5800 - 16000 mm
Thickness: 5 - 90 mm
Weight: Up to 35 tons

 

This edge milling machine is the world's premier automated bevel milling equipment. With its excellent structural design and advanced data algorithms, it achieves full automation from plate detection to the actual milling process, significantly improving processing efficiency while guaranteeing high precision.

 

• Processing Accuracy

Length accuracy: ±1mm when L < 10m; ±2mm when L > 10m;

Width accuracy: ±1mm;

Diagonal accuracy: ±2mm;

Root face accuracy (blunt edge): ±1mm for Y-grooves; +0.5mm for X-grooves.

• Processing Efficiency

The processing efficiency is more than 10 times that of conventional edge milling or edge planing equipment.

HEAT TREATMENT

Heat Treatment Furnace
Max Furnace Size:36x12x13.5m
Max Rated Temperature:1100℃
Max Loading Capacity:800t

Heat Treatment of Pressure Vessels
Heat Treatment of Mining Equipment
Heat Treatment of Tube Sheet
Heat Treatment of Pressure Vessel Head

 

 

GNEE STEEL is currently participating in the procurement phase of a 100,000m³ full containment ammonia storage tank project, supplying high-quality steel plates for critical tank components. Due to the corrosive nature of ammonia and the risk of Ammonia Stress Corrosion Cracking (SCC), the project requires strict metallurgical control of materials according to EN 10028-3 standards.

 

One of the most important technical requirements of this project is the strict limitation of the actual Yield Strength (Re) for all NL2 grade materials. To prevent SCC risks in ammonia storage environments, the actual yield strength must not exceed 390 MPa, regardless of the nominal values specified in the standard or plate thickness ranges. This requirement places higher demands on steelmaking process control, heat treatment stability, and material testing.

 

Raw high-strength steel plates ready for the 100,000 m³ full containment ammonia storage tank production

 

Project Materials and Technical Requirements

 

The project mainly uses P355NL2 and P275NL2 normalized pressure vessel steel plates, which are widely applied in low-temperature storage tanks due to their excellent toughness and weldability.

 

Key technical specifications include:

• Material grades: P355NL2 and P275NL2 (Normalized)
• Yield strength: Standard minimum / Maximum limited to 390 MPa
• Hardness: ≤ 225 HBW in base material
• Impact testing: Charpy-V notch test at -50°C, minimum 27J
• Certification: EN 10204 3.1 certificate, with optional 3.2 certification

 

These strict requirements ensure that the steel plates maintain stable mechanical properties and high resistance to ammonia-induced stress corrosion during long-term operation.

 

Precision rolling and forming of steel plates into curved sections for the 100,000 m³ ammonia storage tank.

 

Project Plate Quantities and Thickness Distribution

 

The total steel demand for this ammonia storage tank project is several thousand tons, mainly distributed across different tank sections:

 

P355NL2 – Inner & Outer Tank Shell Plates

• Lower shell courses: 50 mm thickness – approx. 2,000 tons
• Middle shell courses: 25 mm thickness – approx. 1,400 tons
• Upper shell courses: 10 mm thickness – approx. 500 tons

 

P275NL2 – Tank Bottom Plates

• Thickness: 10–15 mm – approx. 750 tons

 

P275NL2 – Suspended Roof Structure

• Thickness: 5–8 mm – approx. 180 tons

 

S275JR – Outer Roof (Ambient Structure)

• Thickness: 10 mm – approx. 450 tons

 

To improve tank fabrication efficiency and reduce circumferential welds, the project also requires wide steel plates to minimize welding joints, which helps reduce the potential risk of SCC in ammonia service conditions.

 

Formed steel segments wrapped and racked for protection, ready for 100,000 m³ ammonia storage tank assembly.

 

GNEE STEEL provides high-precision steel plate rolling and cylinder fabrication solutions for tank manufacturers worldwide. Send us your plate specifications or fabrication drawings for a fast quotation.

Request A Quote

 

TYPE	GRADE	SPECIFICATIONS
Carbon Steel / Low Alloy Coil	Q235A/B/C/D/Q355B(Q345B)/C/D/E/SS400/SAPH400-C/ASTMA283Grade C	0.7~2.0*1250/1500mm*C 2.3~19.5*1250/1500/1800/2000mm*C
Medium Heavy Plate	Q235B/Q355B(Q345B)/C/D/E	6.0-200x150mm-4000mmxL
Vessel Plate	Q245R/Q345R/HP295/SA516MGR485/SA516GR70/P355NL2/P275NL2/ S275JR//SPV490/ASTM A537 Class 1/Class 2	2.5-120x1500mm-3000mmxL
High Strength Steel	510L/610L/700L/750L/BS600MCK4/BS700MCK2/BS700MCK4/ BS960E/BWELDY700QL2/L4/BWELDY960QL4/HG60D/70D/785D/ Q460D/Q550D/690D/690E/TQ600MCD/TQ700MCD/S700MCD/ WYS600/700/STRENX700MCE/Q490E/Q490D	1.2-60x 1500mm-2500mmxL
Patterned Steel	HQ235A|B	1.2-60x 1500mm-2500mmxL
Wear-resistance Steel	NM360/400/450/500/NM300TP/400TP/450TP/ ABREX400/450/500/B-HARD450XKY/ CREUSABRO4800/8000/EH C400LE/450LE/500LE/ HADOX450/500	3.0-50x1250mm-3300mmxL
Cold Rolled Coil	DC01/RECC/REDT/SPCC/ST12	0.5-3.0x1250mm-1500mmxC
Galvanized Plate	DC51D+AZ/DC51D+Z/DX51D+Z/SGH340+Z275/Z275/Z120/S350GD+ZM275	0.45-3.0x1250mm-1500mmxC
Pickled Coil	DD11/SPHC	2.0-6.0x1500xC

Stainless Steel Material and Surface Specifications

TYPE	GRADE	THICKNESS	SURFACE
Austenitic	304/304H/304L/304J1	0.25-150mm	2B/BA/NO.4/8K/SB/HL/NO.1
Austenitic	321	0.4-80mm	2B/BA/NO.4/8K/SB/HL/NO.1
Austenitic	316/316L/317L/316Ti	0.3-80mm	2B/BA/NO.4/8K/SB/HL/NO.1
Austenitic	201(J1/J2/J5)	0.35-12mm	2B/NO.1/1D
Ferrite	430	0.4-3.0mm	2B/BA/NO.4/8K/SB/HL
Ultra Pure Ferrite	443	0.4-2.0mm	2B
Ultra Pure Ferrite	436L/439/444/441	0.5-3.0mm	2B/2D

Special Steel / Nickel Base Alloy

TYPE	GRADE	GRADE (ASTM)	GRADE (EN)	THICKNESS
Heat-resistant Steel	309S	S30908	1.4833	0.5-40mm
Heat-resistant Steel	310S	S31008	1.4845	0.5-40mm
Duplex Stainless Steel	2101	S32101	1.4162	1.5-50mm
Duplex Stainless Steel	2304	S32304	1.4362	3.0-50mm
Duplex Stainless Steel	2205	S32205/S31803	1.4462	0.5-60mm
Duplex Stainless Steel	2507	S32750	1.4410	1.0-60mm
Super Austenitic-Steel	904L	N08904	1.4539	0.6-50mm
Super Austenitic-Steel	254SMO	S31254	1.4547	0.5-50mm
Super Austenitic-Steel	1.4529	N08926	1.4529	0.5-50mm
Super Austenitic-Steel	AL-6XN	N08367	1.4478	0.5-50mm
Nickel Base Alloy	Alloy 31	N08031	1.4562	1.0-50mm
Nickel Base Alloy	800	N08800	1.4876	0.8-50mm
Nickel Base Alloy	800H	N08810	1.4958	0.8-50mm
Nickel Base Alloy	800HT	N08811	1.4959	0.8-50mm
Nickel Base Alloy	Alloy 28	N08028	1.4563	1.0-20mm
Nickel Base Alloy	Alloy 20	N08020	2.4660	1.0-20mm
Nickel Base Alloy	825	N08825	2.4858	0.8-40mm
Nickel Base Alloy	C276	N10276	2.4819	0.5-50mm
Nickel Base Alloy	C22	N06022	2.4602	1.0-50mm
Nickel Base Alloy	625	N06625	2.4856	0.8-20mm
Nickel Base Alloy	400	N04400	2.4360	1.0-20mm
Nickel Base Alloy	600	N06600	2.4816	1.0-50mm
Nickel Base Alloy	Pure Ni 201	N02201	2.4061	0.5-20mm
Titanium	TA1	Gr.1	Class 1	0.5-50mm
Titanium	TA2	Gr.2	Class 2	0.5-50mm

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