Alloying Elements: Steel Designation According to EN UNI 10027

The UNI EN 10027 standard establishes a unique system for steel designation, divided into two parts: an alphanumeric designation and a numeric designation. This system allows the main chemical and mechanical characteristics of steels to be expressed, enabling a concise identification of the steels.

The alphanumeric designation is divided into two main groups:

• Group 1: Steels defined based on their use and mechanical or physical characteristics.
  Example: Fe 410 Pb
  • Fe indicates iron as the base metal.
  • 410 represents the guaranteed minimum tensile strength or minimum guaranteed breaking load (in MPa).
  • Pb specifies the presence of lead to improve machinability
• Group 2: Steels defined based on chemical composition.
  Example: 38 Cr Ni Mo 4-2-3
  • 38 represents the average carbon content as a percentage multiplied by 100: 0.38%.
  • Cr, Ni, Mo indicate the main alloying elements in descending order of concentration.
  • 4, 2, 3 are multipliers used to determine the content of each element (see Part 2a).

The numeric designation provides a more standardized representation, using numerical codes that specify the chemical composition and other essential details of the steel.

Multiplication factors of alloy elements:

• The alloy elements are represented with the following multiplication factors:
  • 4x: Chromium (Cr), Cobalt (Co), Manganese (Mn), Nickel (Ni), Silicon (Si), Tungsten (W).
  • 10x: Aluminum (Al), Beryllium (Be), Copper (Cu), Molybdenum (Mo), Niobium (Nb), Lead (Pb), Tantalum (Ta), Titanium (Ti), Vanadium (V), Zirconium (Zr).
  • 1000x: Boron (B).

• Let’s consider the alphanumeric code 38 Cr Ni Mo 4-2-3:
  1. 38: Indicates the average carbon content (0.38%).
  2. Cr: Presence of chromium.
  3. Ni: Presence of nickel.
  4. Mo: Presence of molybdenum.
  5. 4-2-3: Represent the specific multiplication factors for the concentration of alloying elements.
     (Cr = 4/4 = 1%; Ni = 2/4 = 0.5%; Mo = 3/10 = 0.3%)

The steel designation system according to UNI EN 10027 allows for precise classification and identification of steel properties. This standard is essential to ensure quality, traceability, and uniformity among producers and users. At Bonomi Acciai, as representatives of the Swiss Steel Group, we offer special steels with designations compliant with UNI EN 10027, guaranteeing reliable and high-performance materials for the most demanding applications.