ASTM A500 Tube, ASTM A500 Structural Tubing

ASTM A500 - Standard Specification for Cold-Formed Welded and Seamless Carbon Steel Structural Tubing in Round Tube, Square Tube and Rectangular Tube Shapes.

ASTM A500 is a standard developed by the American Society for Testing and Materials (ASTM) specifically for Cold-Formed Welded and Seamless Carbon Steel Structural Tubing. This type of steel tube is widely used in building structures, bridges, mechanical supports, vehicle frames, etc., and is favored for its high strength and good machinability.

Features of ASTM A500 Tube:
Cold Forming Process: Improve surface finish and dimensional accuracy through cold rolling or cold drawing.
Welded or Seamless: Can be Electric Resistance Welded (ERW) or Seamless steel tube, depending on the manufacturing process.

Structural Use: Suitable for structures subjected to static and dynamic loads, such as building frames, towers, conveyor systems, etc.

ASTM A500 Pipe & Tube Size range:

Round tube: OD:6.35~660mm WT:1.27~25.4mm
Square tube: Side length:25×25~500×500mm WT:2 mm ~ 16 mm
Rectangular tube: Side length:50×25~500×300mm WT:1.2 mm ~ 18 mm
Standard length: 6m,12m (customizable 5.8m,4m,etc.)

Classification of ASTM A500:

The standard is divided into the following grades and types according to the shape of steel pipes:

A500 Gr.A: round, square and rectangular pipes.
A500 Gr.B: round, square and rectangular pipes (higher strength than Gr.A).
A500 Gr.C: round, square and rectangular pipes (higher strength, suitable for heavy structures).

A500 Gr.D: only for round and square pipes (with higher yield strength).

Manufacturing process:
ASTM A500 steel pipes can be manufactured by welding or seamless process, but most commercial structural pipes are cold formed by welding process.

ASTM A500 Chemical Composition and Mechanical Properties:

ASTM A500 specifies the chemical composition and mechanical property requirements for cold formed welded and seamless carbon steel structural pipes. The standard is classified according to strength grade (Gr.A, B, C, D) and shape (round, square, rectangular).

1. Chemical composition
ASTM A500 has relatively loose requirements on chemical composition, focusing mainly on mechanical properties, but the composition of different grades of carbon steel varies slightly.

Elements	Gr.A (%)	Gr.B (%)	Gr.C (%)	Gr.D (%)
C	≤0.26	≤0.30	≤0.23	≤0.27
Mn	≤1.35	≤1.35	≤1.35	≤1.35
P	≤0.035	≤0.035	≤0.035	≤0.030
S	≤0.035	≤0.035	≤0.035	≤0.030
Cu	≥0.20	≥0.20	≥0.20	≥0.20

Note:
Chemical composition applies to all shapes (round, square, rectangular).

If used for welded structures, carbon equivalent (CE) may need additional control (usually ≤0.50).

- Grade A: Low carbon content, with certain strength requirements, suitable for some general structural uses that do not require particularly high strength.
- Grade B: Compared with Grade A, the strength is improved, and it can be used for structural parts with higher strength requirements.
- Grade C: High carbon content, high strength, durability and good toughness, suitable for structures with large loads.
- Grade D: Higher carbon content, heat treatment is required to meet higher strength and toughness requirements, usually used in structural parts with strict material performance requirements. For square and rectangular tubes, the yield strength requirements of each grade are higher than those of round tubes.

2. Mechanical properties

ASTM A500 mainly divides grades based on yield strength and tensile strength.

Round, square and rectangular tubes (Gr.A, B, C, D)

Grade	Yield strength (MPa)	Tensile strength (MPa)	Elongation (%) (gauge length 50mm)
Gr.A	≥230 (33 ksi)	310-427 (45-62 ksi)	≥25 (round tube)  ≥23 (square/rectangular tube)
Gr.B	≥317 (46 ksi)	400-550 (58-80 ksi)	≥23 (round tube)  ≥21 (square/rectangular tube)
Gr.C	≥345 (50 ksi)	427-550 (62-80 ksi)	≥21 (round tube)  ≥19 (square/rectangular tube)
Gr.D	≥386 (56 ksi)	483-621 (70-90 ksi)	≥15 (round tube)  ≥15 (square tube)

Note:
Gr.B and Gr.C are most commonly used, providing a good balance of strength and weldability.
Gr.D is only suitable for round and square tubes, not for rectangular tubes; Gr.D is suitable for ultra-high strength requirements, but the elongation is low, and it should be used with caution in dynamic load situations.

The elongation requirement varies with the wall thickness, and thicker tubes may require lower requirements.

Inspection and testing:
Various inspection and testing methods for pipes are specified, such as appearance inspection, dimensional measurement, mechanical property testing, chemical composition analysis, etc. Sampling methods and inspection frequencies are also included to ensure that each batch of pipes meets the standard requirements.

Marking and packaging:
The production, steel grade, specification, batch number and other information should be marked on the pipe for easy traceability and management. The packaging should be able to protect the pipe from damage and corrosion during transportation and storage.

Comparison with other structural steel standards:

ASTM A500: cold forming, high-precision dimensions, suitable for high-strength structural applications such as building frames, mechanical supports, etc.
ASTM A53 (Gr.B): more versatile, suitable for piping systems, but the strength is generally lower than A500.

ASTM A1085: a newer standard with optimized chemical composition and mechanical properties, replacing some A500 applications.

A500 Grade selection suggestions:
Grade B: It is the most commonly used grade, suitable for most buildings and mechanical structures.
Grade C: Suitable for high-load structures such as bridges and heavy equipment supports.
Grade D: Mainly used for round tubes that require heat treatment to improve strength and toughness.

Application of ASTM A500 Square and Rectangular Tube:

Architectural structure:
High-rise building frame, steel structure factory, wall and floor and other heavy-duty structures
Glass curtain wall, door and window decoration, guardrail and other decorative structures

Machinery manufacturing:
Engineering machinery frame, conveying equipment bracket
Automobile chassis, motorcycle rack, shelf and fitness equipment

Infrastructure construction:
Bridge support structure, tunnel reinforcement
Power facilities, agricultural greenhouse and water conservancy projects

Transportation:
Railway vehicle structure, container manufacturing
Ship parts and aviation auxiliary equipment

Other fields:
Fluid transportation pipeline (water/gas/fire protection)
Furniture manufacturing, leisure equipment and oil casing

Read more: Types of Seamless Carbon Steel Pipes