STAIN-less steel?

[ZINOM]

Hey all,

I recently made some parts from what I had assumed were two bars of 303 ('cause that's what I'd ordered)....two parts from two bars of different diameter, 3/4" and 7/8".

Now I turned down the parts and thoroughly cleaned each...then I put them in the autoclave (steam sterilizer) for thirty minutes and when I removed them I found that one was spotless, and one was covered in blackish-brownish spots.

Needless to say I wasn't able to use the crappy one.

My question (which sounds really stupid as I write this) is, did they send me one SS and one mild steel, or do some grades of stainless actually rust easier than others....I mean they both seemed to cut with the same degree of difficulty that I usually find with SS.....it didn't seem like I was cutting 1018 or the like.

Thanks for any input.

I feel like an idiot for asking.

John

[lbender]

ZINOM,

First test, is the spotted one magnetic?

[hitnmiss]

At work we use a lot of 303 for cleanroom use. When machining it, small pieces of the cutter get lodged in the 303 and you must passivate (mild acid) the finished part to eat out the rustable pieces of tooling.

[YankeeMetallic]

My guess is that if the one piece that has rust spots is lightly magnetic, it is a 400 series SS.

[topct]

Just passed a magnet over various known pieces of stainless around here.

Have a frying pan, with a matching lid. Bought it new.

The lid is magnetic the pan is not.

Just curious, where did you get your metal?

[ZINOM]

Yes, the spotted one IS magnetic....I checked it after all this happened....I also did a spark test, (not that I know what I'm looking for) and the book I was going by described the differences between low carbon, high carbon and tool steel.....it didn't go into specifics among the different grades of SS.

I have since immersed the part in water just to see what'd happen and it produces a lot of rust......I don't know, I guess I gotta suck it up and order again and hope they send the right thing.....it's not like the visable difference between aluminum and brass.

Thanks guys,

John

[YankeeMetallic]

If you planned on using 303 Su or Se for the ease of machining, you may have gotten 416 stainless instead. If it is in the 'A' state it means it is annealed and easy to machine. Easier to machine (110%) even than the 303 su/se (78%). The 416 is also stronger and more expensive than the 303. You can easily prevent it from rusting when it is at the final product by immersing it in a acid bath for a short duration. The acid will dissolve the ferrite (iron) on the surface without pitting the nickel and other alloys. When you buff the surface after the acid bath you are creating a water tight seal against further rusting under normal atmospheric conditions.
Try machining it to see what you think. If it is a bitch to machine, it is probably in a hardended state, or on the high side of being pump shaft grade. Use only carbide or cobalt to machine it because it will eat up HSS bits even with coolant. I hope this helps.

[ZINOM]

Topct, I got it from Nolan supply (now Abrasive Tool).

I just want to get some bar stock and turn down a couple cylindrical parts...I don't have any acid, I don't even know what "su" or "se" means.

Jeez, I thought this would be slightly simpler hahaha(actually, the other rod required no extra work)....AND, it will need to be sterilized at 15-20 psi at 270 degrees for a half hour each time it is used....which would be often.

Is there a secret handshake or at least a way to let them know that I want regular 303 in a "normal" state....so I can just turn, drill, tap and GO!?

I'm just a guy in his basement with limited knowledge of materials and techniques....so acid baths and annealing are a little beyond my regular practices.

Thanks again for the help thus far.....seriously.

John

[YankeeMetallic]

<font face="Verdana, Arial" size="2">Originally posted by ZINOM:
...I don't have any acid, I don't even know what "su" or "se" means.</font>

I'm sorry about the tech talk. I was where you were not long ago. You will see letter designations with some alloys, steel, aluminum, stainless, brass etc. In this case they add some alloy to help the principle metal machine better. The "se" stands for Selenium and the "su" stands for Sulpher. The addition of either one allows for easier machining but in some cases, the addition of the alloy makes the principle metal less conducive to welding, and may affect its final strength. Using an example for aluminum, 2024 aluminum is great to machine, but it does not weld easily due to an alloy that is mixed in to help it machine better. 6061 aluminum (commonly referred to as 'Aircraft quality aluminum') does not machine as easily as 2024, but 6061 welds easier than 2024.

<font face="Verdana, Arial" size="2">
Is there a secret handshake or at least a way to let them know that I want regular 303 in a "normal" state....so I can just turn, drill, tap and GO!? John</font>

Uh Oh. If you don't know the handshake just forget about everything I just told you.
Actually its all about telling the metal retailer what you want the material for. They should either know it off the top of their head, or they have a book that will tell them the machinabilty, weldability. work hardening, characteristics of the basic type of metal you want.
I just went to a metal supplier today looking for some 416 annealed that I need for a job. Well there is more than one type of 416 annealed. So you learn somthing new everyday. Usually the retailer guys are willing to help and don't mind you asking questions. If I need something I'm not sure of, I start by saying," I'm just a hobbyist and this is what I want to make out of (insert metal), what's the best alloy for my application?
{Edited 'cause o' spellin'}


[This message has been edited by YankeeMetallic (edited 03-07-2006).]

[vmil3]

All you have to take with you is one of those pocket screw drivers with a magnet in the end. When they bring the metal, see if the magnet sticks to it, all 300ss series is non magnetic 303 & 304 has a very little trace of magnetizem. Just noticable, but not enough to hold the little screw driver to the metal.

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Doug