Stainless steel and magnets

[Cynic2701]

316 and 314 stainless have almost no magnetic attraction. All 400 series has a very high magnetic attraction due to it's higher iron content. 300 series can not be heat treated well due to it's low iron content. Looking at scrap yard/recyclers designations 300 series and other stainless that is almost non-magnetic is listed as non-ferrous. It really isn't as it does contain small amounts of iron. 300 series just has a very low iron content.

You are correct, clearly I didn't retain as much from my mechanical engineering classes as I thought.

 

[Chrome Horn]

You may want to check out this forum for slingshots if you haven't already looked at it. I've made a couple of board cut sling shots just for fun.

Yep, thanks, I frequent the slingshot forums. I figured (correctly) the best place to start my quest for info was here.

 

[mete]

What screwed up responses !!! The only difference between 304 and 316 is the addition of Mo in the 316 for corrosion resitance . Both , and all the 300 series are normally austenitic. However if you cold work a 300 steel you can get partial transformation to martensite thus partially magnetic. Md - the start of martensite transformation due to deformation ! This temperature is above the Ms !

 

[tiguy7]

400 series stainless steels were developed for their hardenability. They usually contain about .8% Carbon and 14% Chrome. 300 series stainless steels were developed for their corrosion resistance. They have extra Chrome plus Nickel (usually 18% and 8% respectively). The 400 stuff is more susceptable to corrosion, and the 300 stuff is more susceptable to wear. 300 is more expensive because of the pricey ingredients. 400 can be heat treated. Pots, pans, and surgical instruments lean toward 300, and knives and tools lean toward 400. Usually the higher the number designation, the more alloying elements are added. 320 stainless is used to make chambers in which sulfuric is produced. 440 is a highly alloyed blade steel.

 

[Twindog]

This thread and another make me wonder if it's possible to identify individual steels or steel groups by the calibrated pull of a magnet?

 

[Noctis3880]

I thought it was primarily due to the amount of carbon in the mix.

Nope, H1 and other nitrogen steels are plenty magnetic as well.

 

[me2]

316 and 314 stainless have almost no magnetic attraction. All 400 series has a very high magnetic attraction due to it's higher iron content. 300 series can not be heat treated well due to it's low iron content. Looking at scrap yard/recyclers designations 300 series and other stainless that is almost non-magnetic is listed as non-ferrous. It really isn't as it does contain small amounts of iron. 300 series just has a very low iron content.

If by low, you mean 65% to 72% iron, then yes, its low. For anyone still curious, see mete's and cynic's responses. Then start welding 400 series and 300 series stainless together and enjoy some real confusion. Bring a ferrite gauge. It won't lessen the confusion, but at least I wasn't empty handed.

 

[Fred S2]

Lots of interesting posts. One thing for sure, 300 series is mostly iron. 50-70% as a general rule, as stated above. The thing about 300 series is the microstructure is virtually 100% austenite, which is non magnetic. Ferrite and martensite are the other 2 main microstructures, (there are a bunch) and they are magnetic. Lots of metallurgy goes into what makes the different structures, alloying elements, heat treatments, etc.