What are Ferritic stainless steels and what industries are they used?
The 400 series of plain chromium stainless steel materials includes ferritic, martensitic and some precipitation hardening stainless alloys. They are iron alloys that contain more than 10wt% of chromium. The chromium forms a self-healing transparent continuous protective nano-film.
Usually if the carbon content is kept below 0.10 wt% the alloys are single phase ferritic alloys, whereas beyond this level of carbon , the materials are martensitic. A popular ferritic and lower cost grade is the 10wt% chromium very low carbon content type 409, which is widely used for corrosion resistant car exhaust systems. 409Ti is further stabilised with up to 0.5wt% Ti addition. Alloys 409 and 409Ti possess excellent weld ability and are generally welded with matching chemistry filler metal.
The other popular ferritic stainless steel is type 430 with 16-18 wt% CR content. The higher CR level provides extra corrosion and scaling resistance. It is also welded with matching 430 filler metal. A lower welding heat input safeguards against excess grain growth.
There are a number of fine variants of 409 and 430 alloys and the above welding data applies.