ASTM A618 Hot-Formed High-Strength Low-Alloy Structural Tubing

ASTM A618 Hot-Formed High-Strength Low-Alloy Structural Tubing

ASTM A618 is the industry standard for hot-formed, high-strength, low-alloy structural tubing. This material is widely used in various construction and industrial applications where superior strength, durability, and corrosion resistance are required. Manufactured using a specialized hot-forming process, ASTM A618 tubing exhibits enhanced mechanical properties compared to standard carbon steel, making it an excellent choice for load-bearing structural components, machinery frames, heavy equipment, and other demanding applications. Offering a range of strength grades and dimensional options, ASTM A618 tubing provides engineers and fabricators with a versatile, high-performance material that can be tailored to meet the unique requirements of each project. Whether specifying for new construction or retrofitting existing structures, ASTM A618 delivers the strength, reliability, and cost-effectiveness that modern industry demands.

Chemical Composition of ASTM A618 Hot-Formed High-Strength Low-Alloy Structural Tubing

Element	Grade Ia (Heat)	Grade Ia (Product)	Grade Ib (Heat)	Grade Ib (Product)	Grade II (Heat)	Grade II (Product)	Grade III (Heat)	Grade III (Product)
Carbon, max (%)	0.15	0.18	0.2	—	0.22	0.26	0.23ᵃ	0.27ᵃ
Manganese, max (%)	1	1.04	1.35	—	0.85–1.25	1.3	1.35ᵃ	1.40ᵃ
Phosphorus, max (%)	0.15	0.16	0.025	0.035	0.025	0.035	0.025	0.035
Sulfur, max (%)	0.025	0.045	0.025	0.035	0.025	0.035	0.025	0.035
Silicon, max (%)	—	—	—	—	0.3	—	0.3	0.35
Copper, min (%)	0.2	0.18ⁿ	0.2	0.18ⁿ	—	—	—	—
Vanadium, min (%)	—	—	—	—	0.02	0.01	0.02ᶜ	0.01
Notes:
ᵃ: For each reduction of 0.01% carbon below the specified carbon maximum, an increase of 0.05% manganese above the specified maximum will be permitted, up to 1.45% for heat analysis and 1.50% for product analysis.
ⁿ: If chromium and silicon contents are each 0.50% minimum, then the copper minimums do not apply.
ᶜ: For Grade III, columbium may be used in conformance with limits: 0.005% min (heat), 0.004% min (product).

Mechanical Properties of ASTM A618 Hot-Formed High-Strength Low-Alloy Structural Tubing

Property	Grades Ia, Ib, and II (Walls 3/4 in. (19.05 mm) and Under)	Grades over 3/4 to 1 1/2 in. (19.05 to 38.1 mm), incl.	Grade III
Tensile strength, min, ksi (MPa)^A	70 (485)	67 (460)	65 (650)
Yield strength, min, ksi (MPa)^A	50 (345)	46 (315)	50 (345)
Elongation in 2 in. or 50 mm, min, %	22	22	20
Elongation in 8 in. or 200 mm, min, %	19	18	18

Specifications

Standard	ASTM A618 Hot-Formed High-Strength Low-Alloy Structural Tubing
Steel Grade/Material	Gr.Ia, Gr.Ib, Gr.II. Gr.III
Round Tubing	DN15-DN600, NPS 1/2″ – 24″ (21.3-609.6mm) x WT: 0.109″ – 1.000″ (2.8 – 25.4mm)
Square Tubing	25 x 25 – 800 x 800mm x WT: 2.8 – 75mm
Rectangular Tubing	25 x 30 – 800 x 750mm x WT: 2.8 – 75mm
Length	1 – 12m
Packing	Plain/Beveled Ends, Loosely Packed
Surface Treatment	Bare, Black and Hot-dipped Galvanized
Section Shape	Round, Square, Rectangular
Technique	Seamless or Welded
Place of Origin	Made in China
MOQ	25 Tons
Transportation	Railway, By Sea

Applications

Construction and Infrastructure

Bridges: ASTM A618 tubing is commonly used to fabricate bridge components, especially in areas where high-strength structural tubing is required to support heavy loads and resist environmental degradation.

Buildings: It is utilized to construct steel frames, columns, beams, and other structural supports where high strength-to-weight ratios are essential. This is especially beneficial in high-rise buildings and industrial structures.

Transmission Towers: Due to its strength and resistance to fatigue, ASTM A618 is used in constructing electrical transmission towers and other large infrastructure projects requiring durable structural components.

Automotive Industry

Chassis and Frames: In automotive manufacturing, ASTM A618 is used for chassis components and frame rails that require high strength and impact resistance. It is often used to produce light trucks, buses, and off-road vehicles.

Safety Structures: The tubing is also used in safety-critical automotive components such as roll cages and impact beams, where high-strength materials are necessary to protect occupants in the event of an accident.

Agricultural Equipment

Tractors and Machinery: The tubing’s high tensile strength makes it ideal for use in agricultural equipment such as tractors, plows, and other heavy-duty machinery that endure substantial mechanical stress and require durability.

Harvesters and Loaders: Similar to tractors, harvesters and loaders benefit from ASTM A618 tubing because it can withstand vibration, shock loads, and wear during operation in challenging environments.

Heavy Equipment Manufacturing

Construction Equipment: Excavators, bulldozers, and cranes are manufactured using ASTM A618 because it can support large loads and resist fatigue and wear, which is crucial for heavy equipment working in demanding environments.

Forklifts and Material Handling: The tubing is also used to manufacture forklift frames, lift masts, and other material handling machinery, where strength and resilience are critical for safe operation.

Energy and Oil & Gas Industry

Pipeline Supports and Brackets: In the oil and gas industry, ASTM A618 is used to construct supports, brackets, and other structural components for pipelines. Its strength and resistance to corrosion and fatigue make it ideal for harsh operating environments.

Wind Turbine Structures: This material is used to construct the framework of wind turbines, where structural integrity under stress and resistance to wind and weather conditions are essential.

Railroad Industry

Railcar Components: ASTM A618 is used to manufacture structural components for railcars, such as underframes and other critical structural elements. These components must withstand high loads, vibrations, and significant mechanical stresses.

Railroad Bridges: The tubing is also used in railroad bridges, where its high strength and low-alloy composition offer resistance to wear and fatigue, especially in regions with varying weather and environmental conditions.

Marine and Offshore Applications

Shipbuilding: ASTM A618 is used to construct structural tubing for ships and offshore platforms. Its ability to resist corrosion, fatigue, and impact from harsh marine environments makes it suitable for various marine applications.

Oil Rigs: The tubing is also used for structural elements in oil rigs and offshore drilling platforms, where high strength is necessary to support large, heavy equipment in challenging offshore environments.

Structural Components for Industrial Machinery

Cranes and Hoists: The material is used to construct industrial cranes and hoisting equipment, where strength and fatigue resistance are essential for handling heavy loads over long periods.

Conveyor Systems: In the manufacturing and mining industries, ASTM A618 tubing is used for conveyor frames, rollers, and other structural elements that need to support heavy, moving loads.

Sports Equipment

Bicycle Frames: Some high-end bicycle frames, especially for competitive sports, use ASTM A618 tubing because of its strength-to-weight ratio. The material helps achieve the desired performance while maintaining durability and safety.

Outdoor and Adventure Equipment: Other sports and adventure equipment, such as trekking poles, camping gear frames, and lightweight structural components, can also benefit from ASTM A618’s combination of strength and lightweight properties.