Eiffel 101: Guide to Pipe Grades

There are several organizations that grade steel pipes to help purchasers determine their suitability for projects. The American Society of Testing and Methods (ASTM), American Society of Mechanical Engineers (ASME), American Petroleum Institute (API), American Iron and Steel Institute (AISI), and the Society of Automotive Engineers (SAE) are all highly trusted organizations with unique grading standards. Keeping track of how these organizations grade steel pipes can be challenging. Below is some information to help buyers understand some simple and key components of how grading works at each of these institutes.


The grading designation system for ASTM includes the letter “A,” which indicates ferrous materials and then a number that is assigned sequentially based on the type of product. A grade may also include abbreviated information regarding the specific type of steel, the product’s year of adoption, and the product’s year of most recent re-approval. If the letter “M” is included in a steel pipe’s grade, it is an indication that metric standards of measurement apply. A simple example of an ASTM grading specification is A106 C. “A” stands for “ferrous materials.” 106 is the sequential assignment for seamless carbon steel pipe. And “C” indicates specific qualities of the chemical composition of the steel.

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The grading designation system for ASME is quite similar to ASTM. The major difference between the two is that each specification starts with “SA” to indicate ferrous materials, rather than “A.” If something has an A106 C specification from ASME, it will have an SA106 C specification from ASME. Note that pipe sizes are listed by both ASME and ASTM according to both wall thickness and outside diameter. The only significant difference between ASTM and ASME standards is that ASME requires steel pipe that is graded for high pressure applications receive additional testing to be approved for such use.


API oversees classifying steel pipe specifically for the oil and gas industry. The most common, general API classification for line pipe that is suitable for uses in the oil and gas sector is API 5L. Based on specific mechanical and chemical properties, API pipe receives either a PSL1 or PSL2 designation. It also receives a specific grade designation based on the type of pipe and its ideal applications. Examples of possible grades include: X52, X60, and X70. Each of these grades has a different yield strength, tensile strength, and elongation percentage. Taking all the API possible specifications into account, a pipe might receive the following API designation, for example: API 5L PSL1 X52.

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AISI and SAE use the exact same system of numbers to grade types of steel. The first digit in their system indicates the basic type of steel. The second digit indicates factors regarding chemical composition such as added alloys. The two final digits signal the percentage of carbon content in the steel. For example, 1020 is a possible AISI/SAE grade. Keep in mind that AISI and SAE’s grades do not provide information that is as specific as ASTM, ASME, and API’s information regarding capabilities, applications, and testing results.

Procuring the right steel pipe for a project is essential, and knowing how the specific grading systems of major organizations work can help you ensure that you purchase the correct product. Our guide should help you understand the basics and give you a head start in finding the proper pipe for the job.

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