The 400 series group of stainless steels has an 11 percent chromium and 1-percent manganese increase, above the 300 series group. The 400 series is susceptible to rust and corrosion under some conditions. Heat-treating will harden the 400 series. The 400 series of stainless steels have higher carbon content, giving it a martensitic crystalline structure. This provides high strength and high wear resistance. Martensitic stainless steels aren’t as corrosion resistant as the austenitic types.
The 400 series includes both ferritic and martensitic steels.
Ferritic steels: non-hardening steels, ideal for conditions in elevated temperatures. Typical applications for ferritic stainless steels include petrochemical, automotive exhaust systems, heat exchanges, furnaces, appliances and food equipment to name a few.
Martensitic steels: able to be hardened, ideal for a wide variety of common uses. Martensitic stainless steels are used extensively in cutlery, sport knives and multi-purpose tools.
The table below shows common types of 400 series steel:
|400 Series Applications|
a ferritic steel, used especially for welding applications
heat-resistant; poor corrosion resistance; 11% chromium, 8% nickel.
cheapest type; used for automobile exhausts; ferritic (iron/chromium only).
martensitic (high-strength iron/chromium). Wear-resistant, but less corrosion-resistant.
easy to machine due to additional sulfur
Cutlery Grade martensitic; Excellent polishability.
decorative steel, used for automotive trim; ferritic. Good formability, but with reduced temperature and corrosion resistance.
a higher grade of cutlery steel, with more carbon in it, which allows for much better edge retention when the steel is heat-treated properly.
For elevated temperature service
Advantages and Characteristics of 400 Series Stainless Steel
Ferritic, or nonhardenable stainless steels, are classified in the 400 series. This series is known for:
superior corrosion resistance
resistance to scaling at elevated temperatures
inherent strength greater than carbon steels
provide an advantage in many applications where thinner materials and reduced weight are necessary
nonhardenable by heat treating
Martensitic, or hardenable stainless steels, are classified in the 400 series. This series is known for:
higher levels of carbon than ferritics
ability to be heat treated to a wide range of hardness and strength levels
excellent corrosion resistance