Austenitic (Non magnetic; Non heat treatable); Benchmark from which all other 300 series stainless steels are derived. Slight additions/deletions of such elements as Carbon, Nitrogen, Molybdenum and Sulphur determine machinability and end attributes
Good formability
Increased strength comes from cold working, not from heat treating
Corrosion resistant; high temperature strengths scaling resistance
303 Stainless Steel
18-8
Austenitic; Free machining alloy with Sulphur content that enhances its machinability
Optimum machinability among the Austenitic stainless steels
Good corrosion resistance in mild environments
Not suitable for use in marine environments
Typical applications include nuts, bolts, screws, bushings, shafts and automatic screw machined parts
304 Stainless Steel
18-8
Most widely used austenitic stainless steel
Great choice when corrosion is a concern with atmosphere, chemical exposure
Provides great overall corrosion resistance
Low carbon alloy
Nicknamed the “General Purpose” 300 series stainless steel
Applications include springs, nuts, bolts and screws
316 Stainless Steel
18-8
Austenitic; Standard Molybdenum bearing grade
For severe environments
Excellent corrosion resistance even in chloride environments
Not easily machined
Type 316 is the main stainless used in the marine environment, with the exception of fasteners and other items where strength and wear resistance are needed, then 304 is typically used
Martinsitic stainless steels are optimized for high hardness but provide less corrosion resistance than austenitic grades (300 series)
Hardened by heat treat (quench and temper method)
Contains minimum of 11.5% chromium, just enough to provide corrosion resistance properties
“General Purpose” of 400 series stainless steel
Use in applications where high strength and moderate heat and corrosion resistance are required
Applications include bolts, nuts, screws and bushings
416 Stainless Steel
Martinsitic
Highest machinability of any stainless steel due to Sulphur content but this reduces corrosion resistance
Useful in dry atmospheres as well as fresh water but unsuitable for marine and other chloride atmospheres
Strenge-Martinsitic stainless steels are optimized for high hardness but provide less corrosion resistance than austenitic grades (300 series)
Strengthened by heat treatment
Applications include nuts & bolts, studs and automatic screw machined parts
430 Stainless Steel
Ferritic (Magnetic; Non heat treatable containing chromium but not nickel)
Combines good corrosion resistance, machinabiltity and ductility
Well suited for use in chemical applications
Hardened by annealing, not heat treatment
Applications include fasteners
Carbon Steel
Designated by distinct AISI (American Iron and Steel Institute) four digit numbers
First two digits indicate grade of steel and last 2 digits indicate carbon content in hundredths of a percent
Types:
10xx = Non Resulfurized grades (xx is carbon content in hundredths of a percent)
11xx = Resulfurized grades
12xx = Resulfurized and Rephosphorized grades
15xx = Nonsulfurized grades
If L or B is present between the first 2 and last 2 digits; means that particular grade is a Leaded steel or Boron Steel (Ex. 12L14 = Resulfurized and Rephosphorized leaded steel)
Aluminum
Good conductor of electricity
Possesses good formability and corrosion resistance