ASTM A500 is a standard specification published by the American Society for Testing and Materials (ASTM) that covers cold-formed welded and seamless carbon steel structural tubing in round, square, rectangular, and “special” shapes. It is frequently used in construction projects, such as bridges and buildings, due to its high strength and low weight. 

The standard includes four grades of steel based on their strength. The most common grade of steel used in construction is ASTM A500 Grade B, which has a minimum yield strength of 42000 psi. ASTM A500 Grade C is also commonly used, ASTM A500 Grade C minimum yield strength of 46000 psi. Also, heat treatment is required for Grade D. By meeting the requirements of the ASTM A500 standardS, construction projects can ensure that they are using high-quality materials that will meet their needs

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ASTM A500 Material Component Propertie

ASTM A500  structural tube is only made from materials that meet the carbon steel requirements.ASTM  A500 tube is mostly composed of iron, with additional carbon, manganese, phosphorus, sulfur, and copper. For accurate ASTM A500 carbon steel chemical characteristics, see the chart below

Element Composition, %
Heat analysis Product analysis
Carbon 0.26 0.3
Manganese 1.35 1.4
Phosphorus 0.035 0.035
Sulfur 0.035 0.045
Copper 0.2 0.18

ASTM A500 tube Mechanical Properties

The amount of stretching tension that a material can endure before breaking or failing is referred to as its tensile strength. The ultimate tensile strength of A500 carbon steel is computed by dividing its area by the stress applied to it, which is represented in pounds or tons per square inch of material. Tensile strength is a critical indicator of ASTM A500’s capacity to perform in a given application. The tensile strength of A500 carbon steel is shown in the chart below.

Mechanical Properties of ASTM A500 Round Structural Tubing

Steel Grade Tensile Strength Yield Strength Elongation in 50.8mm
psi Mpa psi Mpa Min
Gr. A 45,000 310 33,000 228 25%
Gr. B 58,000 400 42,000 290 23%
Gr. C 62,000 427 46,000 317 21%
Gr. D 58,000 400 36,000 250 23%

Mechanical Properties of ASTM A500 Shaped Structural Tubing

Steel Grade Tensile Strength Yield Strength Elongation in 50.8mm
psi Mpa psi Mpa Min
Gr. A 45,000 310 39,000 269 25%
Gr. B 58,000 400 46,000 317 23%
Gr. C 62,000 427 50,000 345 21%
Gr. D 58,000 400 36,000 250 23%

ASTM A500 Carbon Steel Permissible Dimensional Variations for Outside Dimensions

Outside diameter measurements for the ASTM A500 carbon steel tube must be taken at least 2″ (50.8mm) from each end.

The outer diameter of round structural tubing having a nominal OD of 1.900″ (48.26mm) or less may vary no more than 0.5 percent of the specified size, rounded to the closest 0.005″ (0.13mm). Outside diameter may not vary more than 0.75 percent, rounded to the closest 0.005″, for nominal ODs of 2″ (50.8mm) and greater.

Square and rectangular structural tubes must be measured across the flats with an allowance for convexity or concavity. The dimensions specified must not exceed the plus/minus tolerances stated in the table below.

Outside Dimensional Tolerances for ASTM A500 Square & Rectangular Steel Tubing

There are multiple considerations that must be accounted for when determining the outside dimensional tolerances for square and rectangular steel tubing. The chart below and the following attributes describe the exact outside dimensional tolerances for A500 carbon steel pipe.

Outside Large Flat Dimension2½ in or underOver 2½ to 3½ inOver 3½ to 5½ inOver 5½ in
63.5mm or underOver 63.5mm – 88.9mmOver 88.9mm – 139.7mmOver 139.7mm
Large Flat Dimension Tolerance± 0.020 in± 0.025 in± 0.030 in0.01 times large flat dimension
± 0.51mm± 0.64mm± 0.76mm

Wall Thickness Requirement OF ASTM A500

Minimum wall thickness at any point of measurement shall not be less than 90% of specified nominal wall thickness. Maximum wall thickness, excluding weld seams, shall not be more than 110% of specified nominal wall thickness. Wall thickness of square structural tubing and rectangular structural tubing must be measured at the center of the flat.

Straightness Requirement OF ASTM A500

For a structural tube, the allowable variation in straightness is 1/8″ times the entire length in feet (or 10.4mm times the number of meters) divided by five.

Side Squareness Requirement

For square structural tubing and rectangular structural tubing, adjacent sides may deviate from 90° by no more than ±2°.

Specified Dimension of Longest Side Maximum Twist in the First 3 ft (1 m ) and in each additional 3 ft
in .( mm ) in. mm
11/%(38.1) and under 0.05 1.39
Over 1/2 to 2/2(38.1 to 63.5), incl 0.062 1.72
Over 2/% to 4(63.5 to 101.6), incl 0.075 2.09
Over 4 to 6(101.6 to 152.4), incl 0.087 2.42
Over 6 to 8(152.4 to 203.2), incl 0.1 2.78
Over 8(203) 0.112 3.11

Applications of ASTM A500 Steel Structural Pipe

Depending on its size, A500 structural pipe is used in construction, heavy equipment, agricultural, machinery, fabrication, and general structural purposes. In construction, they are often used as support beams or columns. In heavy equipment manufacturing, they are used in the construction of machineries such as tractors and excavators. In agriculture, they are often used in the construction of irrigation systems. In fabrication, they are commonly used to create sections for steel beams and pillars. As a result, ASTM A500 structural pipes have a wide range of applications in many industries.

ASTM A500 Carbon Steel Structural Tubing Benefits

ASTM A500 Carbon Steel Structural Tubing has various advantages that make it a popular building material for structural load-bearing applications. Some of the most noticeable advantages that A500 Carbon Steel Structural Tubing offers are:

  • Excellent weldability
  • Good machinability
  • Can be cold worked
  • Aesthetically pleasing
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