What’s up guys?!?!?! Michael with Michael Talks Metal back for the 139 th time continuing our series on stainless steels. This video is focused on the most commercially popular of the austenitic types or grades…… the 300 series of alloys.
What are the 300 series alloys? Well in this case we’ll talk about 303, 304, 316, and 317. Plus all their variants. There are more grades but for today, that’s what’s on the docket.
From our introduction to stainless steels video last week, you know that Chromium is primarily what makes these “stainless” steels corrosion resistant. Other elements also affect the properties of the commercial standard alloys.
In addition to the three digits in the alloy designation, there may be a suffix that indicates a modification of the basic alloy….. a suffix of “L” indicates a low carbon version of the grade.
A suffix of “F” indicates a free machining modification.
“S” indicates Sulfur added
“Se” for Selenium added.
Whenever we mention a % in the chemistry of an alloy, we mean percent by weight. So in an 18% Cr alloy, there would be 18 pounds of Cr in 100 pounds of the alloy.
When Chromium is added to Iron it tends to stabilize a ferritic structure. Molybdenum is also a ferrite stabilizing element. Nickel and Manganese act to stabilize an austenitic structure and are present in various proportions in all the common austenitic types. Other elements present promote either austenite or ferrite in the metallurgical structure.
In this family of standard grades, type 304 is the most popular of the “18-8” grades. Now, do you remember what 18-8 stands for? In this case, I’ll tell you 🙂 18% nominal Chromium content and 8% nominal nickel content. General corrosion performance is very good. The low carbon 304 “L” grade is recommended for applications involving welding or heat cycles above 900 deg. F.
Type 303 (or sometimes shown as 303S) has .15 % minimum Sulfur added which aids in the machining characteristics but with some loss of corrosion performance. 303 Se substitutes Selenium for S to achieve the improved machining with less impact on some other properties but is much less commonly used and much more costly. In case you ever need to BUY any 303Se (I know a guy) 😉 It’s a secret (this guy) 🙂
Type 316 has 2-3% Molybdenum which raises the corrosion performance, particularly in chloride environments. Nickel content is increased to keep the austenitic structure.
317 has yet higher Cr, Ni and 3-4% Molybdenum for another step higher in corrosion performance. 317 “L” for welding applications.
Specifications and part requirements can alter what we have shown you today, so for the 139th time we remind you to CHECK THE SPECS !!! TWICE
So this is Michael with Michael Talks Metal. Thank you so much for tuning in! Michlin Metals is a full service, value added distributor and supplier of all things related to and contained in the austenititic 300 series stainless steels. Check the website for more info www.michlinmetals.com. Still here and haven’t subscribed? Click here. Missed last weeks’ video? Click here. Thanks for watching, this is Michael with Michael Talks Metal. I will see you next week, same time, same place, 10am YT! I’m out!