DME University

Steel Classifications

Steel Classifications

There are two material classifications. The S.A.E. (Society of Automotive Engineers) classification is mainly used in the automotive field. This uses a four or five digit numbering system based on chemical composition. Another classification adopted by industry is the AISI (American Iron and Steel Institute) classification. The main difference between S.A.E. and AISI is that the AISI may use a prefix as a letter which indicates a type of steel making for pretrial sell.

The first digit denotes predominate alloying element in the steel.

  • 1 – Carbon Steel
  • 2 – Nickel Steel
  • 3 – Nickel Chromium Steel
  • 4 – Molybdenum
  • 5 – Chromium
  • 6 – Chrome-Vanadium
  • 8 – Triple Alloy
  • 9 – Silicon-Manganese

The second digit indicates the approximate percent of the element denoted by the first digit. Or the second digit may indicate a second major alloying element. The last two (or three digits in certain corrosion- or heat-resistant alloys) indicate average carbon content in hundredths of one percent.



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