ASTM A312 vs ASTM A358: What’s he Difference?

When finding the right metal piping for your project, it’s important to understand your options. Two common types of piping that you may come across are ASTM A312 and ASTM A358. But what exactly is the difference between these two standards? In this blog post, we’ll explore the key distinctions between ASTM A312 and ASTM A358 and help you decide which might be right for your project.

What Is ASTM A312 And ASTM A358?

ASTM A312 and ASTM A358 are the most common standards for fabricating stainless steel pipe. ASTM A312 is a specification for seamless austenitic, stainless steel pipes, while ASTM A358 covers both electric-fusion-welded and seamless austenitic chromium-nickel alloy steel pipes. Both standards cover all grades of austenitic (including duplex) stainless steels typically used in commercial piping systems. In terms of grade specifics, A312 covers 304/304L/316/316L Stainless Steel Pipes, whereasA358 has Grade 304H, 321H(pipe with an elevated temperature service), 347H(extreme corrosion resistance). To ensure maximum strength and durability, both standards provide extensive testing requirements to certify conformance to strict criteria – including physical tests such as dimensions & tolerances checks and hydrostatic pressure tests for leakage detection.

Difference Between ASTM A312 And  ASTM A358

ASTM A312 and ASTM A358 are specifications for seamless and welded steel pipes. The difference is in the pipe wall thickness, length range, manufacturing process, pressure rating and certification requirements.

ASTM A312 covers seamless and welded steel pipes with nominal outside diameters ranging from ½ to 4 inches. It generally comes in two grades: TP304/L or TP316/L grade, which have different chemical compositions and mechanical properties. It offers high-temperature strength, good formability, excellent corrosion resistance, and good creep resistance at elevated temperatures. The metal wall thickness of the pipe ranges from 16 gauge (0.0625 inches) up to 22 gauge (0.0312 inches).

ASTM A358 covers electric fusion welded steel pipes with a nominal outside diameter ranging from 1 inch to 5 feet 11-1/2 inches long, with either square cut or bevel ends depending on the size specified by the user. This is a lower specification than ASTM A312 compared to its counterparts because there’s no need for such rigorous testing due to its low working pressure ratings (up to 350 psig). This specification’s minimum metal wall thickness also starts larger at 14 gauge(0 .083 inch), going up to 6 mm thick (.236 inch).

Both specifications have different requirements when it comes to testing, including tensile strength tests, nondestructive testings such as eddy current inspection for seamless tubes; hydrostatic tests; flaring tests; radius bend tests; flattening tests; hardness tests; impact tests etc .. Lastly, both grasses offer varying levels of certification depending on application needs like API 5lf certificate of production etc.

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ASTM A312 is a specification for seamless, welded, and heavily cold-worked austenitic stainless steel pipe. The ASTM A312 specification covers pipes that have been heat treated to be strong and corrosion-resistant.


ASTM A358 is a specification for electric-fusion-welded austenitic chromium-nickel stainless steel pipe. The ASTM A358 specification covers pipes welded with an electric arc process.

Difference in Composition

The main difference between ASTM A312 and ASTM A358 is the composition of the materials used to make the pipes. ASTM A312 pipes are made from austenitic stainless steel, while ASTM A358 pipes are made from austenitic chromium-nickel stainless steel.

Difference in Manufacturing Process

Another difference between ASTM A312 and ASTM A358 is the manufacturing process. ASTM A312 pipes are made through a seamless or welded process, while ASTM A358 pipes are made through an electric arc welding process.

Difference in Applications

The final difference between ASTM A312 and ASTM A358 is the applications for which each type of pipe is best suited. ASTM A312 pipes are best suited for high-temperature and high-pressure applications, while ASTM A358 pipes are best suited for low-temperature applications.


So there you have it, the key differences between ASTM A312 and ASTM A358. While both standards define austenitic stainless steel pipes, there are differences in the method of manufacture, specifications for chemical composition, and recommended applications. Understanding these differences can help you decide when to choose the right piping for your project. Regardless of your chosen standard, it’s important to work with a reliable supplier that can provide high-quality pipes that meet your requirements.

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