ASTM A500 (Also known as A-500) carbon steel tubing is a standard specification for cold-formed, welded and seamless carbon steel structural tubing in round, square and rectangular shapes. ASTM A500 is the most common specification in North America Hollow Structural Sections (HSS).
The ASTM A500 specification covers cold-formed welded and seamless carbon steel tubing in round, square, rectangular, and “special” shapes for welded, riveted, or bolted construction applications, as well as for general structural purposes.
Round and shaped steel cold formed welded and seamless carbon steel structural pipe.
Standard: ASTM A500 for Cold-Formed Welded and Seamless Carbon Steel Structural Tubing in Rounds and Shapes.
ASTM A500 is a standard specification for cold-formed welded structural tubing produced to round nominal pipe sizes.
Main purpose:
- electricity
- petroleum
- chemical companies
- high temperature
- low temperature resistance
- corrosion-resistant piping systems.
ASTM A500 structural pipe is welded pipe sized tubing made from flat-rolled steel, formed through a roller system and welded 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.
Specifications:
- OD :10.3-820 mm
- wall thickness: 0.8 to 75 mm
- Length: 6m
In addition, based on customer requirements, which can supply other grades and specifications of steel pipe.
Processing: steel shall be in accordance with one or more of the processing: open-hearth, blowing oxygen, or electric furnace steelmaking, casting of different grades of steel in order, steel producers should determine the intermediate material using conventional procedures removed, a clear separation of a Level.
Manufacturing: produced by seamless or welded steel pipe, welded pipe by rolling made by resistance welding.
The structural design strength of the longitudinal direction of the pipe, the docking application tube is a method of determining the through its thickness to weld.
ASTM A500 steel pipe chemical component(%)
| Grade | C | M | P | S | Cu |
|---|---|---|---|---|---|
| Gr.A | 0.26 | 1.35 | 0.035 | 0.035 | 0.20 |
| Gr.B | 0.30 | 1.40 | 0.045 | 0.045 | 0.18 |
| Gr.C | 0.23 | 1.35 | 0.035 | 0.035 | 0.20 |
| Gr.D | 0.27 | 1.40 | 0.045 | 0.045 | 0.18 |
ASTM A500 steel pipe mechanical properties Min (MPa)
| Grade | Tensile Strength | Yield Strength | Elongation |
|---|---|---|---|
| Gr.A | 310 | 230 | 25 |
| Gr.B | 400 | 290 | 23 |
| Gr.C | 425 | 315 | 21 |
| Gr.D | 400 | 250 | 23 |
Impact test requirements for ASTM A500 Gr.C
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.
Manufacture
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.
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.
Outside dimensions
Outside diameter measurements must be made at positions at least 2” (50.8mm) from either end of the tubing. For round structural tubing with nominal OD of 1.900” (48.26mm) and smaller, the outside diameter may not vary more than ±0.5%, rounded to the nearest 0.005” (0.13mm), of the specified size. For nominal ODs of 2” (50.8mm) and larger, outside diameter may not vary more than ±0.75%, rounded to the nearest 0.005”. Square structural tubing and rectangular structural tubing must be measured across the flats and include an allowance for convexity or concavity. Specified dimensions shall not exceed the plus/minus allowances shown in the table below.
Outside Dimension Tolerances For Square and Rectangular Structural Tubing
| Outside Large Flat Dimension, in. (mm) | Large Flat Dimension Tolerance, A plus and minus, in. (mm) |
|---|---|
| 2½ (63.5) or under | 0.020 (0.51) |
| Over 2½ to 3½ (63.5 to 88.9), incl | 0.025 (0.64) |
| Over 3½ to 5½, inc | 0.030 (0.76) |
| Over 5½ (139.7) | 0.01 times large flat dimension |
Wall thickness
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 centr of the flat.
A500 Grade A, B & C Tubing
Sunny Steel supply square, rectangle, round and special shaped electric resistance welded (ERW) carbon steel tubing to meet ASTM specifications A500 Grade A, Grade B and Grade C that is often used in structural applications. The purpose and strength levels required will determine which grade is required.
Square & Rectangle Tubing
Below are physical properties required to meet the three grades that we produce ASTM A500 square, rectangle and special shaped tubing to. A flattening test is not a standard requirement for non-round tubing produced to A500.
| Grade | Yield (min) | Tensile (min) |
|---|---|---|
| Grade A | 39,000 psi | 45,000 psi |
| Grade B | 46,000 psi | 58,000 psi |
| Grade C | 50,000 psi | 62,000 psi |
Round Tubing
Below are physical properties required to meet the three grades that we produce ASTM A500 round tubing to. A flattening test is also a standard requirement for round tubing produced to the A500 specification.
| Grade | Yield (min) | Tensile (min) |
|---|---|---|
| Grade A | 33,000 psi | 45,000 psi |
| Grade B | 42,000 psi | 58,000 psi |
| Grade C | 46,000 psi | 62,000 psi |
Specification Notes
- According to ASTM A500, the weld seam location for square, rectangle and other special shaped tubing shall not be located within the corner radius unless specified by the customer or manufacturer.
- Under ASTM A500, the corner radius for square and rectangular tubing shall not exceed three times the corner radius.
- As a standard under ASTM A500, electric resistance welded tubing is normally provided without removal of inside flash. If flash control is required, please specify at time of quotation or order placement.
- ASTM A847 is a related structural specification that covers high strength low alloy atmospheric corrosion resistant steel tubing. Please refer to the ASTM A847 page for more information.
ASTM A53 Pipe vs. ASTM A500 Pipe
If you have ever referred to the ASTM (American Society for Testing and Materials) standard documents used for steel design and construction, you’ll notice that ASTM A53 steel pipe designations are different than ASTM A500 round hollow structural sections and they are manufactured to meet different standards. While ASTM A500 is available in cross-sections matching each of the cross-sections for ASTM A53 steel pipe, there are many more cross-sections available in A500.
In this article, I will outline the differences between A500 structural hollow sections and A53 pipe and discuss why ASTM A500 is the better choice.
ASTM A53 Pipe
ASTM A53 pipe, a standard specification for black and hot-dipped, zinc-coated, welded and seamless steel pipe, is used for mechanical and pressure applications as well as ordinary uses in steam, water, gas and air lines. ASTM A53 can be formed and welded. Pipe sizes are properly designated using the Nominal Pipe Size (NPS). This is the nominal pipe diameter with a scheduled wall thickness (i.e., 4 inch Schedule 40 pipe).
ASTM A500 Pipe
ASTM A500 is a standard specification for cold-formed, welded and seamless carbon steel structural tubing in round, square and rectangular shapes. ASTM A500 is the most common specification in North America for Hollow Structural Sections. Round HSS sections are properly designated by indicating the outside diameter in decimal inches by the nominal wall thickness to three decimal places (i.e., 5.563 x 0.250).
Why A500
Since ASTM A500 is a structural specification, round HSS produced to this specification are fit for purpose when used for structural applications and general construction use. ASTM A53 is a pipe specification and is intended to be used in mechanical and pressure applications.
The specified yield strength of A500 Grade C (the most commonly available grade) is 46 ksi. The specified yield strength of A53 Grade B is 35 ksi. That’s over a 30% increase in yield strength. Therefore, A500 round HSS have greater strength-to-weight ratios than A53 pipes. So, with round HSS you need less steel, by weight, to do the job—less weight equals less cost.
The tolerances of A500 are tighter than those of A53, therefore the A500 round HSS have a higher degree of quality and less variability.
Round HSS have a superior surface finish and do not come with the lacquer coating that typically comes on A53 pipe. This saves money and time as this lacquer coating needs to be removed from the A53 pipe to accommodate welding and painting.
A53 pipe are only available in standard pipe sizes. Round HSS come in a variety of sizes and wall thicknesses.
Lastly, the ASTM A53 Specification requires testing (i.e., pressure testing) that is not needed for structural applications. This additional testing can add unnecessary additional cost.
ASTM A500 applications include structural supports, building columns, highway signs, oil field services and communication towers, to name a few. All steel structures have their pros and cons, but ultimately ASTM A500 is the better choice when you need a round profile.
