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  • Details
  • ASTM A501 is a standard specification for hot-formed welded and seamless carbon steel structural tubing (hollow sections) in square, rectangular, round, or special shapes. It covers three steel grades (A, B, and C) with varying mechanical and chemical properties to suit different structural applications.

    ShapeRound, square, rectangular, or special shapes
    Round tubing DimensionsDiameters 1 – 48 in. [25 – 1220 mm] and wall thickness of 0.095 – 4.00 in. [2.5 – 100 mm]
    Square and rectangular tubingDiameters 1.0 – 16 in [25 – 405 mm] and wall thickness of 0.095 – 1.0 in [2.5 – 25 mm]
    StandardASTM A501/A501M – 2021.pdf


     

     


      
    Chemical Composition 
    The chemical requirements for ASTM A501 hollow sections vary by grade:

    Composition, %Grade AGrade B and Grade C
    Heat AnalysisProduct AnalysisHeat Analysis 
    Carbon, max B0.260.300.22 
    Manganese, max B--1.40 
    Phosphorus, max0.0350.0450.030 
    Sulfur, max0.0350.0450.020 
    Copper, min
    (when copper steel is specified)
    0.200.180.20 

    B For each reduction of 0.01 percentage point below the specified maximum for carbon, an increase of 0.06 percentage point above the specified maximum for manganese is permitted, up to a maximum of 1.60 % by heat analysis and 1.65 % by-product analysis.

     

    Grade A: Basic carbon steel with no specified Mn or Si requirements. 
    Grades B & C: Enhanced strength and toughness due to controlled Mn and Si content. 
    Grade C: Lower P and S for improved weldability and ductility. 
     

    Mechanical Properties 
     

    ListWall Thickness
    in [mm]
    Grade AGrade BGrade C
    Tensile strength, min, psi [MPa]All58,000 [400]65000 [448]70,000 [483]
    Yield strength, min, psi [MPa]≤ 1 [25]39,000 [270]46,000 [315]50,000 [345]
    >1 [25] and ≤ 2 [50]38,000 [260]45,000 [310]49,000 [340]
    >2 [50] and ≤ 3 [76]36,500 [250]42,500 [290]47,500 [330]
    >3 [76] and ≤ 4 [100]35,000 [240]40,000 [280]46,000 [315]
    Elongation, min, %-252423
    Impact Energymin, average, ft/Ibf [J]-20 [27]20 [27]20 [27]
    min, single, ft/Ibf [J]-14 [19]14 [19]14 [19]


     

    Grades B & C offer higher strength, making them suitable for load-bearing structures. 
    Grade C is preferred for applications requiring superior weldability and impact resistance. 
     

    Dimension Tolerance 
     

    ListToleranceShape
    Outer Diameter>2 in [50 mm]±1 %all
    ≤ 2 in [50 mm]±1/48 in [0.50 mm]
    Wall Thickness-10 %all
    Weight-3.5 % – +10%all
    Length (L)≤ 7m [22 ft]-1/4 in – +1/2 in [-6 mm – +13 mm]all
    7-14m [22-44 ft]-1/4 in – +3/4 in [-6 mm – +19 mm]


     


     

     

     

      
    Manufacturing Process 
    Hot-forming: Hollow sections are produced by hot-rolling or hot-finishing (for seamless) at high temperatures (≥1700°F/925°C), enhancing ductility and grain structure.

    Welded tubes: Formed from coiled steel, shaped into hollow sections, and electric-resistance welded (ERW).

    Seamless tubes: Produced via mandrel rolling or extrusion for uniform strength.

    Post-treatment: May include normalizing (optional for Grades B/C) to refine microstructure.

      
    Key Applications 
    ASTM A501 hollow sections are widely used in structural and construction applications, including:

    Building frames (beams, columns, trusses).

    Bridges and highway structures.

    Industrial equipment supports.

    Scaffolding and temporary structures.

    Machinery and transportation components.

     

    Grade Selection Guidance: 
    Grade A: General-purpose applications with moderate strength requirements. 
    Grade B: Higher-load structures (e.g., bridges, heavy-duty frames). 
    Grade C: Critical applications needing enhanced weldability and toughness (e.g., seismic-resistant structures). 
      
    Advantages Of ASTM A501 Hollow Sections 
    Cost-effective compared to cold-formed sections (A500).

    High strength-to-weight ratio for efficient structural design.

    Versatility in shapes (round, square, rectangular).

      
    Fabrication & Welding 
    Weldability: Excellent (Grades B & C are preferable for welding due to lower P/S). 
    Machinability: Good (responds well to cutting, drilling, and bending). 
    Surface Treatment: Often galvanized or painted for corrosion resistance. 
     

    ASTM A501 Vs. ASTM A500 
     

    ParameterASTM A501 (Hot-Formed)ASTM A500 (Cold-Formed)
    Production MethodHot-rolled or hot-finished (welded/seamless) at high temperatures.Cold-formed (welded) at room temperature, then stress-relieved.
    Grades AvailableA, B, C (increasing strength)A, B, C, D (D is high-strength, unique to A500)
    Chemical CompositionHigher carbon in Grades A/B (≤0.30%); Grade C optimized for weldability (≤0.23% C).Tighter control on residuals (e.g., phosphorus, sulfur) for cold-forming.
    Dimensional ToleranceSlightly looser due to hot-forming process.Tighter tolerances (cold-forming allows precise control).
    Residual StressesLower (hot-forming reduces internal stresses).Higher (cold-forming induces stresses; may require annealing).
    WeldabilityGood (Grade C best due to lower carbon).Excellent (lower carbon in Grades B/C/D).
    Corrosion ResistanceSimilar (both require coatings for outdoor use).Similar (but cold-formed may have better surface finish).
    CostGenerally lower (hot-forming is less energy-intensive).Slightly higher (due to cold-working and finishing).
    Primary ApplicationsHeavy construction (bridges, cranes), infrastructure.Architectural (exposed structures), precision frameworks.
    Advantages- Better for heavy loads due to ductility.
    - Lower cost.
    - Less residual stress.
    - Sharper corners (better for aesthetics).
    - Higher strength options (Grade D).
    - Tighter tolerances.

     

    Conclusion 
    ASTM A501 hollow sections (Grades A, B, C) provide a robust solution for structural applications, balancing strength, weldability, and economy. Grade selection depends on mechanical demands and environmental conditions, with Grade C being optimal for high-performance scenarios. 
     

ASTM A501 Hot-formed Carbon Steel Hollow Sections

ASTM A501 is hot-formed seamless and welded carbon structural steel tubing for welded, riveted, or bolted structures used in bridges and buildings, and for general structural purposes. It can be square, round, rectangular, or other specialized shapes. The grade of the tubing is Grade A, Grade B, and Grade C.

Keyword

  • Details
  • ASTM A501 is a standard specification for hot-formed welded and seamless carbon steel structural tubing (hollow sections) in square, rectangular, round, or special shapes. It covers three steel grades (A, B, and C) with varying mechanical and chemical properties to suit different structural applications.

    ShapeRound, square, rectangular, or special shapes
    Round tubing DimensionsDiameters 1 – 48 in. [25 – 1220 mm] and wall thickness of 0.095 – 4.00 in. [2.5 – 100 mm]
    Square and rectangular tubingDiameters 1.0 – 16 in [25 – 405 mm] and wall thickness of 0.095 – 1.0 in [2.5 – 25 mm]
    StandardASTM A501/A501M – 2021.pdf


     

     


      
    Chemical Composition 
    The chemical requirements for ASTM A501 hollow sections vary by grade:

    Composition, %Grade AGrade B and Grade C
    Heat AnalysisProduct AnalysisHeat Analysis 
    Carbon, max B0.260.300.22 
    Manganese, max B--1.40 
    Phosphorus, max0.0350.0450.030 
    Sulfur, max0.0350.0450.020 
    Copper, min
    (when copper steel is specified)
    0.200.180.20 

    B For each reduction of 0.01 percentage point below the specified maximum for carbon, an increase of 0.06 percentage point above the specified maximum for manganese is permitted, up to a maximum of 1.60 % by heat analysis and 1.65 % by-product analysis.

     

    Grade A: Basic carbon steel with no specified Mn or Si requirements. 
    Grades B & C: Enhanced strength and toughness due to controlled Mn and Si content. 
    Grade C: Lower P and S for improved weldability and ductility. 
     

    Mechanical Properties 
     

    ListWall Thickness
    in [mm]
    Grade AGrade BGrade C
    Tensile strength, min, psi [MPa]All58,000 [400]65000 [448]70,000 [483]
    Yield strength, min, psi [MPa]≤ 1 [25]39,000 [270]46,000 [315]50,000 [345]
    >1 [25] and ≤ 2 [50]38,000 [260]45,000 [310]49,000 [340]
    >2 [50] and ≤ 3 [76]36,500 [250]42,500 [290]47,500 [330]
    >3 [76] and ≤ 4 [100]35,000 [240]40,000 [280]46,000 [315]
    Elongation, min, %-252423
    Impact Energymin, average, ft/Ibf [J]-20 [27]20 [27]20 [27]
    min, single, ft/Ibf [J]-14 [19]14 [19]14 [19]


     

    Grades B & C offer higher strength, making them suitable for load-bearing structures. 
    Grade C is preferred for applications requiring superior weldability and impact resistance. 
     

    Dimension Tolerance 
     

    ListToleranceShape
    Outer Diameter>2 in [50 mm]±1 %all
    ≤ 2 in [50 mm]±1/48 in [0.50 mm]
    Wall Thickness-10 %all
    Weight-3.5 % – +10%all
    Length (L)≤ 7m [22 ft]-1/4 in – +1/2 in [-6 mm – +13 mm]all
    7-14m [22-44 ft]-1/4 in – +3/4 in [-6 mm – +19 mm]


     


     

     

     

      
    Manufacturing Process 
    Hot-forming: Hollow sections are produced by hot-rolling or hot-finishing (for seamless) at high temperatures (≥1700°F/925°C), enhancing ductility and grain structure.

    Welded tubes: Formed from coiled steel, shaped into hollow sections, and electric-resistance welded (ERW).

    Seamless tubes: Produced via mandrel rolling or extrusion for uniform strength.

    Post-treatment: May include normalizing (optional for Grades B/C) to refine microstructure.

      
    Key Applications 
    ASTM A501 hollow sections are widely used in structural and construction applications, including:

    Building frames (beams, columns, trusses).

    Bridges and highway structures.

    Industrial equipment supports.

    Scaffolding and temporary structures.

    Machinery and transportation components.

     

    Grade Selection Guidance: 
    Grade A: General-purpose applications with moderate strength requirements. 
    Grade B: Higher-load structures (e.g., bridges, heavy-duty frames). 
    Grade C: Critical applications needing enhanced weldability and toughness (e.g., seismic-resistant structures). 
      
    Advantages Of ASTM A501 Hollow Sections 
    Cost-effective compared to cold-formed sections (A500).

    High strength-to-weight ratio for efficient structural design.

    Versatility in shapes (round, square, rectangular).

      
    Fabrication & Welding 
    Weldability: Excellent (Grades B & C are preferable for welding due to lower P/S). 
    Machinability: Good (responds well to cutting, drilling, and bending). 
    Surface Treatment: Often galvanized or painted for corrosion resistance. 
     

    ASTM A501 Vs. ASTM A500 
     

    ParameterASTM A501 (Hot-Formed)ASTM A500 (Cold-Formed)
    Production MethodHot-rolled or hot-finished (welded/seamless) at high temperatures.Cold-formed (welded) at room temperature, then stress-relieved.
    Grades AvailableA, B, C (increasing strength)A, B, C, D (D is high-strength, unique to A500)
    Chemical CompositionHigher carbon in Grades A/B (≤0.30%); Grade C optimized for weldability (≤0.23% C).Tighter control on residuals (e.g., phosphorus, sulfur) for cold-forming.
    Dimensional ToleranceSlightly looser due to hot-forming process.Tighter tolerances (cold-forming allows precise control).
    Residual StressesLower (hot-forming reduces internal stresses).Higher (cold-forming induces stresses; may require annealing).
    WeldabilityGood (Grade C best due to lower carbon).Excellent (lower carbon in Grades B/C/D).
    Corrosion ResistanceSimilar (both require coatings for outdoor use).Similar (but cold-formed may have better surface finish).
    CostGenerally lower (hot-forming is less energy-intensive).Slightly higher (due to cold-working and finishing).
    Primary ApplicationsHeavy construction (bridges, cranes), infrastructure.Architectural (exposed structures), precision frameworks.
    Advantages- Better for heavy loads due to ductility.
    - Lower cost.
    - Less residual stress.
    - Sharper corners (better for aesthetics).
    - Higher strength options (Grade D).
    - Tighter tolerances.

     

    Conclusion 
    ASTM A501 hollow sections (Grades A, B, C) provide a robust solution for structural applications, balancing strength, weldability, and economy. Grade selection depends on mechanical demands and environmental conditions, with Grade C being optimal for high-performance scenarios. 
     

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