ASTM A500 is a standard specification published by the ASTM for cold-formed welded and seamless carbon steel structural tubing in round, square, and rectangular shapes. It is commonly specified in the USA for hollow structural sections, but the more stringent CSA G40.21 is preferred in Canada. Another related standard is ASTM A501, which is a hot-formed version of this A500.
The black steel pipe is also used for fire sprinkler systems because it is more fire-resistant than galvanized pipe. Another related standard is ASTM A501, which is a hot-formed version of this A500. ASTM A500 defines four grades of carbon steel based primarily on material strength.
This is a standard set by the standards organization ASTM International, voluntary standards development organizations that sets technical standards for materials, products, systems, and services.
Applications
Applications are for structural use as in bridges, buildings or general structural use. The alloy may be welded, bolted or riveted for construction purposes.
Machinability
This is a simple carbon steel alloy and is readily machined by conventional means. It is similar to 1027 steel in machining characteristics.
Forming
Forming is readily accomplished by conventional methods.
Welding
The alloy is weldable by all of the standard methods.
Heat Treatment
Not applicable. The product is used in the “as supplied” condition and may be annealed or stress relieved by the supplier as supplied.
Forging
Product is supplied in piping form and is not subsequently forged.
Hot Working
No data. Generally hot forming would not be done. Contact the steel supplier for additional information.
Cold Working
Cold works readily by conventional methods.
A500 cold-formed tubing comes in four grades based on chemical composition, tensile strength, and heat treatment. The yield strength requirements are higher for square and rectangular than for round tubing. The minimum copper content is optional. Grade D must be heat treated.
Mechanical Properties
Properties
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Grade A
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Grade B
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Grade C
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Tensile Strength, min. psi
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45,000 (310Mpa)
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58,000 (400Mpa)
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62,000 (427Mpa)
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Yield Strength, min. psi
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39,000 (269Mpa)
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46,000 (317Mpa)
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50,000 (345Mpa)
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Elongation in 2” min.
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25%
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23%
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21%
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3/16” wall & heavier 1/8” wall
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25%
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19.50%
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21%
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Chemical Composition(%)
Chemical elements
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Grades A&B
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Grade C
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Twist
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Largest Side
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Max. Twist in 3 feet
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Carbon, max. %
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0.26
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0.23
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Over 1-1/2” to 2-1/2” inclusive
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.062”
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Manganese, max. %
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—
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1.35
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Over 2-1/2” to 4” inclusive
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.075”
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Phosphorus, max. %
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4%
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0.04
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Over 4” to 6” inclusive
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.087”
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Sulphur, max. %
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5%
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0.05
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Over 6” to 8” inclusive
|
.100”
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Cooper, when cooper steel is specified min. %
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20%
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0.2
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Over 8”
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.112”
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Note:
Straightness: .025” times the number of feet of total length
Squareness of Sides: Deviation from 90ce by +/-2ce max.
Radius of Corners: The radius of any outside corner shall not exceed three times the specified wall thickness.
Wall thickness: +/-10% of nominal wall thickness, as measured at the center of the flat.
Remarks: a).1’ = 0.3048m, 1” = 25.4mm
b).1PSI = 0.00689Mpa
Straightness: .025” times the number of feet of total length
Squareness of Sides: Deviation from 90ce by +/-2ce max.
Radius of Corners: The radius of any outside corner shall not exceed three times the specified wall thickness.
Wall thickness: +/-10% of nominal wall thickness, as measured at the center of the flat.
Remarks: a).1’ = 0.3048m, 1” = 25.4mm
b).1PSI = 0.00689Mpa
Outside Dimensions
Largest Outside Dimension
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Tolerance*
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2-1/2” and under
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±0.020”
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Over 2-1/2” to 3-1/2” inclusive
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±0.025”
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Over 3-1/2” to 5-1/2” inclusive
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±0.030”
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Over 5-1/2”
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±1%
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Note:
Tolerances include allowance for convexity or concavity. For rectangular tubing having a ratio of outside large to small flat dimension less than 1.5, and for square tubing, the tolerance on small flat dimension shall be identical to the large flat dimension tolerance.
Tolerances include allowance for convexity or concavity. For rectangular tubing having a ratio of outside large to small flat dimension less than 1.5, and for square tubing, the tolerance on small flat dimension shall be identical to the large flat dimension tolerance.
For rectangular tubing having a ratio of outside large to small flat dimension in the range of 1.5 to 3.0 inclusive, the tolerance on small flat dimension shall be 1.5 times the large flat dimension tolerance.
For rectangular tubing having a ratio of outside large to small flat dimension greater than 3.0, the tolerance on small flat dimension shall be 2.0 times the large flat dimension tolerance.
ASTM A500 is a classification that covers material used for welding and seamless carbon steel structural tubing. The classification has three grades, with Grade C being a newer mixture that is primarily used for roll cages and cold temperatures. ASTM A500 Grade C must meet certain requirements in order to pass impact tests administered by ASTM. Originally known as the American Society for Testing and Materials, ASTM is an international standards developing organization that establishes standards when dealing with metals and other materials used in industrial areas.
Mixture Requirements
According to ASTM rules, all tubing must have the chemical mixtures of carbon, manganese, phosphorus, sulfur and copper present. In addition, the steel produced must be done by open-hearth, basic-oxygen or electric-furnace melting methods. It is not enough to have the correct chemicals mixed in the tubing; materials must also undergo specific welding methods in order to be approved by ASTM A500.
Welding Procedures
In addition to the three aforementioned steel-producing methods, tubing must also be welded using flat-rolled steel. The flat-rolled steel should be formed into a tube using the electric-resistance welding process. Using the electric-resistance welding process will assist the material in passing the tension and flattening test that evaluates the sturdiness of the piece.
Shape
ASTM rules require that the longitudinal butt joint of the tubing be thickly welded in order to assure the secure structural design of the piece. ASTM will not approve tubing that has a weak joint because such weakness may pose a problem to the entire structure. Thousands of structures built with poor still joints would be in danger of collapsing if the ASTM did not uphold this regulation.
Inspection
Before the manufacturer is given permission to market products, all tubing must be inspected by an ASTM representative. The purpose of the inspection is to assure conformance to structure requirements; tubing that fails to pass inspection must either be corrected or discarded. In addition, the appearance of tubing must be professional and free from defects; it should not, for example. be severely burned or have bumps or blotches of steel in any one place.
