What Are the Differences
Choosing
the correct material is critical to any application especially those designed
for wash-down, corrosion resistance, heat resistance or strength. There are a
variety of materials to choose from with many different specifications tied to
them. Stainless steel is a popular and affordable choice in the packaging
industry, especially for food grade applications. In this post, we dissect
stainless steel and the different grades of each.
Types of Stainless Steel Alloys
The main types of stainless steel alloys are austenitic, ferritic, martensitic, duplex and precipitation hardening stainless steels. The most widely used and popular is austenitic. Austenitic stainless steel is non-magnetic and its structure allows for the material to be hardened through cold-working. The subgroups of austenitic stainless steel are 300 and 200. We will review the main grades of stainless steel in the 300 subgroups as these are the most widely used grades.
303 vs 304 vs 316 Stainless Steel
303 Stainless Steel
303 is a free-machining grade of 304 stainless steel that contains added sulfur or selenium. The addition of sulfur or selenium increases the machinability. Its composition contains at minimum 17% Chromium, 8% nickel, and 0.15% Sulfur/Selenium. The small addition of sulfur slightly reduces corrosion resistance but increases machineability which is why you will find its use in fasteners, bushings, bearings and other smaller components, these components require more accurate machining specifications due to the required tolerances. While 303 stainless steel still has strong corrosion resistance, for an added boost, 304 stainless steel is recommended.
304 Stainless Steel
304 stainless steel contains a minimum of 18% chromium and 8% nickel which gives its alternate name 18/8 stainless steel. 304 stainless steel contains chromium-nickel content and low carbon. This stainless steel type is oxidation and corrosion resistant. This durability provides ease for fabrication and prevention of product contamination. 304 stainless steel is considered the most versatile and common austenitic stainless steel. 304 stainless steel is more cost effective compared to 316 stainless steel.
316 Stainless Steel
316 Stainless Steel Contains a minimum of 16% chromium, 10% nickel and 2% molybdenum. The main difference between 304 and 316 stainless steel is the fact that 316 stainless contains a significantly increased amount of molybdenum. This increase in molybdenum results in increased corrosion resistance. Molybdenum is a transition metal and has high corrosion resistance. It also gives 316 stainless steel high heat resistance of up to 1600 ⁰F. Similar to 304, 316 stainless steel is a chromium-nickel stainless. If the environment has high amounts of corrosive elements and/or materials that would be placed underwater, 316 stainless is a preferred choice.
| Grade | Chemical Properties | Tensile Strength | Yield Strength | Rockwell Hardness | Corrosion Resistance | Application Use |
| 303 | 17% Chromium, 8% nickel, and 0.15% Sulfur |
620
MPa
90000
psi | 241 MPa 35000 psi | B84 | Good | Bushings, bearings, nuts, and bolts |
| 304 | 18% chromium and 8% nickel | 586 MPa 85000 psi | 241 MPa 35000 psi | B80 | Better | Architecture, food processing (dairy), packaging, piping materials, seawater |
| 316 | 16% chromium, 10% nickel and 2% molybdenum | 586 MPa 85000 psi | 241 MPa 35000 psi | B80 | Best | Hot water systems, food processing (dairy), packaging, piping materials, surgical |
300 Series Stainless Mechanical Components
Whether your application requires 316 or 304 stainless steel, MISUMI carries a variety of configurable 300-grade stainless steel components including plates, tubing, fittings, pipes, fasteners, and rods/bars to fit your requirements. MISUMI is ISO 9001:215 Certified and a proud member of the PMMI. Visit our product spotlight page for MISUMI’s offerings here
