The Battle of Stainless: 303/304 vs. 316

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

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5 Comments


  1. Joel Titcomb

    June 6, 2019 at 11:09 am

    Austenitic stainless steel can not be hardened by heat treating. It doesn’t have enough carbon. However it can be hardened by cold working.

    Reply

    • Carlicia Layosa

      June 6, 2019 at 1:42 pm

      Hi Joel,
      You are correct. Thanks for catching that! I will correct it.

      Reply

  2. Curtis Edwards

    June 6, 2019 at 12:31 pm

    Carlicia – this is an excellent article! And, I would offer the suggestion of taking the discussion to the next step – that of appropriate finishes for Stainless Steel. So many times at my previous employer(s) people would specify Stainless Steel for a particular job, would be “shocked” that the part has corroded in the environment (wet or not). Whereas a simple passivation treatment is generally all that is needed to keep the parts bright over the span of their usable life, sometimes it would not be specified “on-the-print”.

    Maybe my experiences are unique, but I think not, since I have seen (and heard) many others complaining about post manufacturing corrosion…

    Lastly, when it comes to painting Stainless Steel (liquid or powder coating paint systems) appropriate pre-finish surface cleaning (SSPC-SP1, -SP3, -SP4, etc.) seems to be areas that are either glossed over, or neglected entirely, by a percentage of the Engineers and Designers…

    Anyway, those are my two cents! Take care!

    Reply

    • Carlicia Layosa

      June 6, 2019 at 1:54 pm

      Your insights from your experience with working on stainless steel are very valuable. I’m sure many manufacturers experience similar pain points, one of the many reasons our blog exists.

      Thank you for reading and ideas for future blog posts, Curtis!

      Reply

  3. Harsha

    June 8, 2019 at 3:25 am

    Hi,
    Its really a valuable piece of information. Keep writing….

    Reply

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