Names and initials steel AISI
You can purchase various types of stainless steels, mainly known under the notation of AISI (American Iron and Steel Institute, Institute of unification for U.S. iron and steel).
The notation AISI was wrong the meaning of a synonym for "stainless steel", since this institution also encodes different types of steel.
The notation identifies the stainless steel AISI through a code of three digits with a possible addition of a letter.
The first of these figures indicates the class of steel:
2XX series - stainless austenitic chromium-nickel-manganese
3XX series - stainless austenitic chromium-nickel and chromium-nickel-molybdenum
4XX Series - ferritic and martensitic chromium
5XX series - stainless martensitic chromium medium
6XX-series precipitation-hardening stainless chromium
between letters such as:
the letter "L" indicates the percentage of low carbon steel (low carbon) present. This feature makes the steel tie less gas, as carbon tends, in any condition, to bond with hydrogen, falling oil and the presence of hydrogen is often damaging to the steel at high temperatures and especially in state of ionization (ionizing radiation). The atom of hydrogen ion (H +) is very small and high-temperature moves more easily in the lattice of steel, may accumulate and cause harmful discontinuities. The low carbon content also allows good weldability for thickness> 6 mm.
the notation "N" indicates the presence of dissolved nitrogen in the alloy. Thanks to its properties of inert gas (nitrogen-nitrogen is the link three times, the atoms are very close together and therefore difficult to separate), the nitrogen acts as a limiting steel external contamination.
The record you would indicate the presence of titanium which provides full corrosion resistance in welds of thick elements.
