Determining if it's stainless steel and what type

[benmychree]

440C is some nice stuff for heat treating . Way back in the day we built up a Vette motor for one of our machinists . Ran like a bat outta heck until he rolled the car .

Yeah, when I worked at Kaiser Steel, we replaced various hard chromed hydraulic piston pump valve seats and valve plungers with 440C, which I hardened and finish ground. These were reciprocating water pumps that were powered by hydraulic punps with big electric motors, they pumped water with soluable oil, the water was pumped into the hydro expander that expanded the large diameter line pipe being made a certain percentage in diameter, this pipe was up to 1" wall thickness and about 40 ft long, as it expanded in diameter, it shrunk in length, likely several inches. The water carried significant amounts of mill scale that dropped off the surface of the plate as it stretched, this stuff is fairly abrasive and eroded hard chrome, it was a big maintenance issue, they finally installed a wheeelabrator machine early in the forming process, and also replaced the recip. pumps with commercial triplex pumps.

 

[graham-xrf]

Stainless also does weird things to scotch whiskey. I know this because I was given one of those curved flasks. I am not a flask guy, but I did try it out, and then I forgot about it for some weeks. When I opened it, the scotch had turned kind of very dark, so I tipped it down the sink. I won't drink anything that has managed to leach stuff out of a toxic metal!

 

[mmcmdl]

Stainless also does weird things to scotch whiskey.

Beer also . I fill up one of my stainless mugs and sit it down , the damn thing is always emptied out . Can't figure it out . hiccup .

 

[RJSakowski]

The chromium in stainless or any other alloy is in a 0 valence state. Hexavalent chromium is +6 and it takes a powerful oxidizer to get it there. When I worked in a chem lab, we used chromic acid for cleaning glassware. We also made a cleaning solution by dissolving potassium dichromate in concentrated sulfuric acid. The chromium in both of these is hexavalent. Cr+6 in solution is easily reduced by both inorganic and organic reducing agents. Conversely, it is difficult to oxidize chromium to the +6 valence state. Electrolysis is one way though.

 

[vtcnc]

Stainless had the interesting property that you can make it rot at the boundary of water and air. Get a strip of stainless and leave it in a glass of water, with some sticking up above the water, and the rest below. Enjoy the spectacle of of a line of rust at the boundary. This happens with A2. I think A4 is more resistant to this phenomenon. The name of the process is "differential aeration".

I have also reduced "stainless" into rusty mush. It does take temperatures above 700C, and it having seen some calcium chloride salt. That stuff does not wash away completely, even if you use loads of water.

A word about stainless, and getting it wet with any chemicals. It has hexavalent chomium. That stuff is so unbelievably toxic that it's an outright hazard to us! Trying to use a stainless ex-chip fry tub as a vessel for electrolysis de-rusting, to also be one electrode, was a very bad idea!

[The curious can google "hexavalent chromium", and decide the most we should do with stainless is to machine it. If you start, use lube, cut deep enough, and don't stop on the way. If it rubs, the tool is immediately trashed from work hardening! ]

Lol. Working in commercial kitchen equipment manufacturing gift many years, had to remind customers and sales people that it is stainLESS not stainproof.


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[JACK-TR6]

Excuese me, but 304 is definitely magnetic; the 400 series are mostly non magnetic or only slightly so. If I understand your posting correctly.

Read your correction after I posted my response to 300 being magnetic. 440 has carbon in it so it can be heat treated. I deleted most of my response. Sorry

 

[wayback machine]

Another thing with most stainless grades is oxygen deprivation corrosion, for instance, I once saw a centrifuge bowl used in wine production, at the end of the season, it was flushed out with water and closed up, leaving a small amount of water in the bowl, and Alge bloom ensued which depleted the oxygen present in the bowl, the result was an area of several inches that was eaten up to a depth of nearly 3/16" deep in the middle with sloping sides, this was subsequently welded up and re machined flush with the original surface.

A perfect example of this is found on boats that have been used in salt water - It's common to find that stainless hardware will be almost completely eaten away, where it passes though the hull. The stainless hardware looks perfectly fine on the outside, but ...........
Imagine a sailboat, with the standing rigging (shrouds) attached to chain plates, bolted through the hull with stainless bolts - Very bad things can happen if the hardware isn't checked and replaced - I've always heard it referred to as "crevice corrosion"