Applications for which certain tubing is most suitable are determined by the strength requirements of the tube. They are often referred to as hollow structural sections or HSS. Welded steel frames with multiple directions of loading commonly use rectangular sections.
Since square and circular HSS have uniform geometry along two or more cross-sectional axes, they have uniform strength characteristics under multiple-axis loading. As a result, they are good choices for columns. Torsion resistance is also excellent.
Architectural aesthetics in exposed structures can sometimes be enhanced by the flat square surfaces of HSS structural tubing. Typically, we produce to ASTM A500 grade B standards, but we can also produce to ASTM A1085. Outside dimensions (OD) and wall thickness (gauge) are specified.
In structural applications, we produce square, rectangle, round, and special shaped electric resistance welded carbon steel tubing to ASTM specifications A500 Grade A, Grade B, and Grade C. The grade required will depend on the purpose and strength level. Valmont does not produce tubing that meets the Grade D specification.
Below are the physical properties required to meet the three grades that we produce ASTM A500 square, rectangle, and special shaped tubing. A flattening test is not a standard requirement for non-round tubing produced to A500.
Below are the physical properties required to meet the three grades that we produce ASTM A500 round tubing. A flattening test is also a standard requirement for round tubing produced to the A500 specification.
ASTM A500 specifies that weld seams should not be located within the corner radius of square, rectangle, and other specially shaped tubing.
According to ASTM A500, the corner radius of square and rectangular tubing shall not exceed three times the diameter of the tube.
Under ASTM A500, electric resistance welded tubing is normally provided without removing inside flash. At the time of quotation or order placement, please specify if flash control is required.
The ASTM A847 specification covers high-strength low alloy atmospheric corrosion-resistant steel tubing.
In structural load bearing applications, A500 Carbon Steel Structural Tubing offers several advantages that make it highly sought after. A500 Carbon Steel Structural Tubing provides the following benefits:
The ASTM A500 specifications state that manufactured carbon steel tubing must meet certain specifications before being sold for any type of project. The A 500 carbon steel spec sheet provides a convenient and simple way to check material standards before beginning your next project.
ASTM A500 spec states that welded tubing shall be made from flat-rolled steel using electric-resistance welding. Longitudinal butt joints of welded tubing shall be welded across its thickness in such a manner as to assure the structural design strength of the tubing section. Welded structural steel tubing is typically furnished without the removal of inside flash.
A500 carbon steel structural tubing is only manufactured from materials that match the criteria for carbon steel. The chemical composition for A500 is mostly iron with added carbon, manganese, phosphorus, sulfur, and copper. Check out the chart below for exact A500 carbon steel chemical specifications.
In material science, tensile strength refers to how much stretching stress a material is able to withstand before breaking or failing. A500 carbon steel’s ultimate tensile strength is calculated by dividing its area by its stress, expressed in pounds or tons per square inch. An important measure of A500’s performance is its tensile strength. The chart below describes the tensile strength of A500 carbon steel.
Outside diameter measurements for A500 carbon steel tube must be made at positions at least 2” (50.8mm) from either end of the tubing.
It is prohibited for round structural tubing with a nominal outside diameter of 1.900″ (48.26mm) or less to vary by more than 0.5%, rounded to the nearest 0.005″ (0.13mm). Nominal ODs of 2″ (50.8mm) and larger cannot vary more than 0.75%, rounded to the nearest 0.005″.
A convexity or concavity allowance must be made when measuring square structural tubing and rectangular structural tubing across flats. The specified dimensions must not exceed the plus/minus allowances shown in the table below.
When determining outside dimensional tolerances for square and rectangular steel tubing, multiple factors must be taken into account. Below is a chart that shows the exact outside dimensional tolerances for A500 carbon steel.
The minimum wall thickness at any point of measurement should not be less than 90% of the specified nominal wall thickness. The maximum wall thickness, excluding weld seams, shall not exceed 110% of the nominal wall thickness. The wall thickness of square and rectangular structural tubing must be measured in the center of the flat.
For structural tubing, the maximum variation in straightness is 1/8″ times the total length in feet (or 10.4mm times the number of meters).
The adjacent sides of square structural tubing and rectangular structural tubing cannot deviate more than 2° from 90°.
The radius of any outside corner of square structural tubing or rectangular structural tubing cannot exceed three times (3x) the specified wall thickness.
For square structural tubing and rectangular structural tubing, the tolerances for twist (variation with respect to axial alignment) are shown in the table below.