AISI – History and Standards

AISI stands for the American Iron and Steel Institute, an industry association that has been at the forefront of North American steel production and is a pivotal industry association for North American steel producers. Established as a means to foster better cooperation in the steel and iron industry, AISI has been instrumental in disseminating information and setting standards for the production and composition of steel and stainless steel. Today, members of AISI account for the lion’s share of steel production in the region.

The Historical Evolution of AISI

Tracing its roots back to the 19th century, AISI has a storied history spanning over 150 years. It began in 1855 with the formation of the American Iron Association, dedicated to advancing the interests of the trade in all its facets. Recognizing the growing importance of steel, the association underwent a name change, evolving into the American Iron and Steel Association, a precursor to the modern-day AISI. By 1908, the burgeoning growth of the iron and steel industry necessitated a more standardized approach to steel production, leading to the birth of the American Iron and Steel Institute. A few years later, in 1913, the two entities merged, solidifying AISI’s position in the industry.

AISI’s Role in Steel Standards

AISI has been pivotal in shaping the standards for steel grades. Collaborating with SAE International, AISI introduced a unique numbering system for steel. Although SAE International took over the system’s maintenance in 1995, steel grades in North America are still commonly referred to as AISI, SAE, or AISI-SAE. Here’s a breakdown of the AISI classification system with examples:

  1. Carbon Steels: 
    • Example: AISI 1020
      • The first digit “1” indicates it’s a carbon steel.
      • The subsequent digits “020” denote the carbon content, which is 0.20% in this case.
  2. Alloy Steels: 
    • Example: AISI 4140
      • The first digit “4” indicates it’s a molybdenum steel.
      • The subsequent digits provide more specific information about the steel’s content.
  3. Stainless Steels: 
    • Example: AISI 304
      • The number “304” is a widely recognized grade for stainless steel, known for its corrosion resistance.
  4. Tool Steels: 
    • Example: AISI O1
      • The letter “O” indicates it’s an oil-hardening tool steel.
  5. Steelmaking Process: 
    • C: If the steel grade contains the letter “C”, it means the material has been processed in an open-hearth furnace or basic oxygen furnace.
      • Example: AISI C1020
    • E: The prefix “E” signifies the material has been processed in an electric arc furnace.
      • Example: AISI E52100

This classification system by AISI ensures a standardized approach to identifying and understanding the properties and applications of different steel types.

Exploring Advanced Steel Treatments

For those in the industry looking to enhance the properties of steel, there are several advanced treatments available. Boronizing with BOROCOAT® offers high hardness and exceptional protection against wear. For stainless steels, the BORINOX® process can significantly increase hardness and wear protection. Additionally, NICKELCOAT® provides excellent corrosion protection, especially in acidic environments, making it a preferred choice for many industrial applications.