Farberware stainless steel cookware pot cracking

Used as a physical demonstration of deformation-induced ferromagnetism in 304 stainless — not as a failure case in this lecture. The pot itself appears across the corpus as a cracking case; here it's the magnetism teaching prop.

[Tom holds up a 304 stainless steel cookpot.] Which is one of the reasons I brought the Farberware pot. It's 304 stainless steel, sort of like the 302. Down here where it's not deformed, it's magnetic but not very magnetic. Up here it's really magnetic because it got deformed more. The reason I have 302 balls in there is because the more they're deformed, the more ferromagnetic they become. They transform on deformation to become magnetic.

Full case treatment. Farberware 304 stainless steel pots manufactured in Brooklyn, shipped to Japan, arrived cracked. Tom diagnosed strain-induced martensite from forming operation plus hydrogen from plasma-spray surface roughening (argon/5% nitrogen gas) as the delayed-cracking mechanism. MIT Industrial Liaison Program consult. The pot is a recurring physical-object teaching prop.

Another story on stainless steel. [Tom produces a Farberware pot.] This is probably twenty years old. Farberware came to me through the MIT Industrial Liaison Program. They're members and they can get free consulting. They paid back then about an hour of the faculty member's time. In the 1980s I got more ILP consulting than any other faculty member at MIT. I did a lot of failure analysis — I used to have three or four companies a week coming in. They tell me their problem and I shoot them an answer just like that.

ILP consulting case ~20 years prior. Cooking pots formed from 304 stainless steel shipped from Brooklyn factory to Japan, arriving with side cracks. Tom's magnet test revealed deformation-induced martensite at the formed sidewall — the case continues into the next session.

I see this about once a year. Someone comes to me and they say, we found a crack. I have a stainless steel Farberware pot in my office — maybe I'll bring it in on Monday. About 20 years ago, MIT has an Industrial Liaison Program, and Farberware, who was making these pots, came in with this problem. They can consult with the faculty member for one hour and it doesn't cost them anything more than about eighty thousand dollars a year to MIT. The faculty member will get eighty dollars in discretionary funds for spending an hour talking to these people. I used to do this more than anybody else on the faculty in the 1980s.

So there were all these MDs who were worried about the Curie temperature of high-alloy steels. They were fighting over the fact that some steels — even 304 stainless, which is 18-8 chromium-nickel, 18 chrome 8 nickel stainless steel, the first original stainless steel from 1910 or so — if you cold work it, it can transform from the austenitic phase to a martensitic phase. The martensitic phase can be magnetic. I didn't bring my little pot with me, but I have a Faberware cooking pot that was formed and it was 304 stainless steel, and I take a little magnet and just go up that pot and you can see — at the top of the pot, I'll have to remember to bring it Wednesday — go up that little pot and you can see the increased magnetism where you get more plastic deformation in the steel.