How to Identify Stainless Steel Alloys with XRF
303 and 304 stainless steel look identical.
They have the same silver finish, the same general appearance, the same non-magnetic behavior, and nearly the same density. On a rack with no tags, they are visually indistinguishable by any method short of elemental analysis.
In a machine shop, that matters more than most operators realize until they've had the wrong one in a part.
303 is a free-machining stainless steel. Sulfur is added to the alloy specifically to improve machinability. It breaks the chip, reduces tool wear, and makes 303 significantly easier and faster to machine than 304. For high-volume turned parts where machining speed drives cost, 303 is often the right choice.
304, however, is a general-purpose austenitic stainless with better corrosion resistance than 303. The sulfur that makes 303 machine well also creates sulfide inclusions that act as initiation sites for pitting corrosion in aggressive environments. For parts exposed to corrosive media, saltwater, or chemical service, 304 is the specification, and 303 is a liability.
Weldability is another distinction. 303 is not recommended for welding. The sulfur content causes porosity and hot cracking in welds, while 304 welds cleanly with standard practices.
A 303 part specified as 304 that ends up in a welded assembly is a quality failure that may not show up until the joint is under stress.
Handheld XRF analyzers distinguish 303 from 304 immediately. Sulfur content is measurable and definitive. The alloy match on screen tells you exactly what you're holding before it goes on the lathe or into the fixture.
In a shop that runs both alloys, that distinction is the difference between a part that performs and a part that fails in service.
Know exactly what's on your rack before it goes in the machine.
Shop handheld PMI XRF analyzers at Alloy Geek
More XRF Resources for PMI
There are a lot of ways to save money and time with XRF analysis, especially in industries that deal in PMI. Learn more about the uses and benefits of XRF analysis for your business from an XRF professional.
- Verifying Incoming and Outgoing Materials with XRF
- Handheld XRF for Quality Assurance and Quality Control
- Manufacturers Prevent Costly Internal Material Mix-Ups With XRF
- How Machine Shops Prevent Material Mix-Ups with XRF
- XRF is The Best Way to Identify Unknown Material
- How to Verify Outgoing Materials with XRF
- Verifying Raw Materials as They Come In with XRF
- Uses of XRF for Industrial Metal Identification
- Uses of XRF for PMI, or Positive Material Identification