Visual Difference SS 316 and SS 904

Spark test won't do?

oilcan13

Never tried it. My initial response is no.

Actually using an Xray fluorescence analyzer for copper ought to do it quite easily. Here's a pdf that explains how to sort similar grades by properly setting elemental maxima minima: http://instruct.uwo.ca/earth-sci/xrfcourse/20th%20Anniversary%20Symposium/Talk%2005%20-%20Jim%20Stachowiak%20-%20New%20Advances%20and%20Applications%20using%20X-ray%20Fluorescence%20Analyzer%20for%20Metals%20Testing%20in%20the%20S.pdf Milo

No doubt there are ways to analyze the two steels. I'm not sure anybody a layman like me can look at them and tell the difference.

Cheers.

Thank you , Lyn.

I have come to learn

Look into portable alloy analyzers. These are hand-held devices that register the response signature from all of the elements in the metal and report a % composition for all the elements. There are two types. One is XRF (X-Ray Fluorescence), which involves a radioactive source and can't report Carbon or small elements; however, it is the most common and comes in a pistol-like form. The other is a kind of spark / spectrometer that comes in a small suitcase and probe form. Either will be able to tell the difference between 316 and 904.

They're a bit expensive, but are probably cheaper than confusing the alloys. They are also non-destructive.

The other alternative is to cut a sample and have it tested.

Here is a possible method:

"Austenitic Grades

All austenitic grades have very low magnetic permeabilities and hence show almost no response to a magnet when in the annealed condition; the situation is, however, far less clear when these steels have been cold worked by wire drawing, rolling or even centreless grinding, shot blasting or heavy polishing. After substantial cold working Grade 304 may exhibit quite strong response to a magnet, whereas Grades 310 and 316 will in most instances still be almost totally non-responsive.

The change in magnetic response is due to atomic lattice straining and formation of martensite. In general, the higher the nickel to chromium ratio the more stable is the austenitic structure and the less magnetic response that will be induced by cold work. Magnetic response can therefore be used as a method for sorting grades of stainless steel, but considerable caution needs to be exercised."

You might want to buy a Gaussmeter and experiment with know pieces to see if you can establish a difference between the 2 alloys.

XRF PMI

SS 316 harder then SS 904

SS 316 - 95 HRB

SS 904 -70...90 HRB