What is the main alloying element in the AISI 400 series?

The AISI 400 series of stainless steels are primarily defined by their high chromium content. These alloys typically contain between 11% and 30% chromium, which significantly enhances their resistance to oxidation and corrosion. The presence of chromium allows for the formation of a thin, protective oxide layer on the steel surface, which is key to the stainless property of these alloys. While nickel can be found in some variations of stainless steels, it is not a major component of the AISI 400 series. Instead, these stainless steels often rely solely on chromium for their strength and corrosion resistance. Thus, the identification of chromium as the main alloying element perfectly aligns with what characterizes the AISI 400 series.