Metal Properties that allow workhardening?

Hello all.I just cannot find a definitive answer to a couple of questions I'll bet someone on here knows the answer to. Thanks.

304 & 316 Stainless can work harden easily, But 303 has chemical properties close but doesn't work harden as easily. I know 303 has sulfur that helps machining and is that what also prevents against work hardening? I noticed cold drawn bar (1X6) is available in 303 but not 304 guessing for the same reason.
Guessing not carbon as I never have had a problem with 4150 like I have with a 304/316 stainless

1.What makes 303 less easily workhardenable when machining? (just the sulfur?)

2.What are the chemical properties that make metal prone to workhardening? (guessing not carbon as 316 Is lower but workhardens like a B.)

I will let someone else answer the theory part as to why, I do not know. If you want a 300 series stainless that is very slow to work harden use 303Se. We used it for wire rope fittings and as advertised it was slow to harden and crack in that use.

Thanks. I wasn't looking for a material to use just wondering what makes it do what it does. Aluminum bronze work hardens easily too. They all must have something in common.

Work hardening, also known as strain hardening, is the strengthening of a metal or polymer by plastic deformation. This strengthening occurs because of dislocation movements and dislocation generation within the crystal structure of the material. Many non-brittle metals with a reasonably high melting point as well as several polymers can be strengthened in this fashion. Alloys not amenable to heat treatment, including low-carbon steel, are often work-hardened. Some materials cannot be work-hardened at low temperatures, such as indium, however others can only be strengthened via work hardening, such as pure copper and aluminum.

This does not address your question, but is the internet answer to" what is work hardening?" Use your search engine to find these terms: Stress-strain diagram, interstitial structure, substitution structure, crystal structure of metals, the states of matter, etc.

I don't think there is a simple bullet list that summarizes why certain alloys work harden and others don't. In other words, don't expect ever to read a cheat sheet containing statements like "Alloys with more than 0.5% phosphorus will (not) work harden." It's best to just go with the empirical results: "We found that MegaMetals alloy 425X (which I just made up) work hardens very quickly and requires aggressive depth of cut to cut cleanly."

Tin Man said:

Thanks. I wasn't looking for a material to use just wondering what makes it do what it does. Aluminum bronze work hardens easily too. They all must have something in common.

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Without getting into atoms and other tiny s**t, to our utility, all that the metals (not all materials we work even BEING "metal") that we class as "work hardening" have in common is that they "harden" far enough before they actually FAIL that we either have a problem working them, or a useful characteristic we can put to advantage.

"Work hardening" otherwise is part of why a chip peels-off. The material at the flute of a milling cutter or tip of a drill or lathe tool has been forced past its local yield-point, "hardening" - or the ATTEMPT to do - a part of that "curve".

An armorer of the Bronze age sharpened a sword, axe head, or spear point by first hammering its edges. Overdo it, they cracked.

Iron weapons, then steel, one had to file or grind.

Mangalloys have wide useful ranges of work hardening before ultimate failure. Some alloys are even classed as "unmachinable", though that isn't strictly so. Just so DIFFICULT we look to other means of shaping them.

It is a useful characteristic as well as an annoying one. Depends on what you want.

Look up Hadfield Alloy, Mangalloy, and the effect of Manganese - then what it is Industry MAKES with these, just for one of the older and most useful examples - Bronze muscle-powered armaments having gone out of favour as high-tech military weapons a while back, already.

WHICH elements play a part in work-hardening? Very nearly ALL of them, actually. Not many metals get softer from being beaten-on (some do, and that is useful as well. See "goldbeater's skin" and how gold leaf can actually be made so thin as to be partially transparent )

Different primary metals and their alloys just work-harden in different ways under certain conditions, and not to the same degree nor end-result.

Work hardening is the piling up of dislocations within the crystal structure, generally a dislocation is the result of the solidification process where a half plane of atoms is wedged between two full planes, the more nucliation sites a metal has by way of additions of things like sulphur, boron etc etc the smaller will be the grains and higher the number of dislocations
Annealing a metal requires that these dislocations be “piled up” to get sufficient energy for recrystallisation, eg you can’t anneal somthing that hasn’t been cold worked.(you can grow crystals so big the metal is weak)
Generally the above is correct but it is out of my head without the aid of
Wickedpedia
Mark

boslab said:

out of my head without the aid of
Wickedpedia

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I think they just put another church official under house arrest for that, so we'd best give it a miss. yah?

In my defence I think my iPad is exhibiting symptoms of demonic possession
Interestingly gold and lead recrystallise at room temp, we had a high temp recrystallisation microscope (heated stage) in the lab, it was fascinating watching it happening, like ice forming on a windshield, actually quite beautiful, to make useful steel you need to work harden it, they call it “temper rolling” giving it some cold work, they do it with brass and copper too, T1 thru 5 in steel, 1/4,1/2 etc for non ferrous, even the stainless got temper rolled, though less was needed, just skin pass normally though we didn’t do a great lot of stainless sheet, mostly plate
Mark

AFAIK lead and gold are the only metals that do not work harden. No idea how this varies as alloying metals ,are added to the mix. Maybe a jeweler can chime in on this. pure, 24karat, gold is seldom used because it is too soft. It normally has some silver added to make it a bit stronger. I do not know how that affects work hardening.
Bill D.

PS: Lead balloon...Myth Busters made a balloon of thin lead sheet, filled with helium, and it floated in the air.

Bill D said:

AFAIK lead and gold are the only metals that do not work harden.

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Not 100% so. There is a swing-open ring body made for folk with enlarged finger joints. In order to keep the overall Gold content at the stated purity, it uses a gold spring for the latch. Gold springs were also used in early Marine Chronometers to side-step degradation from the corrosive effects of salt air.

Making a spring of high-percentage Gold alloy takes advantage of work-hardening, not heat-treating. Great care IS needed when welding to the rest of the ring to not to damage the "spring".

Nooo, I do not recall the alloying, if ever I even knew or cared.

We just purchased the few we needed in any given year from a specialist, welded the "normal" ring tops to them.

Bill D said:

AFAIK lead and gold are the only metals that do not work harden.

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Which begs a related question: What's the practical threshold for "work hardens enough to be a problem"? This would obviously vary by process, but I'm not even sure what units the answer would be expressed in.

FYI
Strain hardening exponent - Wikipedia

Excellent, Triaged. Thanks!

Thanks for the answers! Some great replies here I'm going to spend some time absorbing it !

sfriedberg said:

Which begs a related question: What's the practical threshold for "work hardens enough to be a problem"? This would obviously vary by process, but I'm not even sure what units the answer would be expressed in.

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The standard unit for workhardenability is the megaPITA

Oldwrench said:

The standard unit for workhardenability is the megaPITA

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Usually accompanied by 11% - 13% or so of Manganese, where some of us learnt the pain.

Hadfield, or Mangalloy, is categorically one of best known, longest-serving and most useful of work-hardening alloys of (reasonably) modern times as well. In fact - it is credited as "THE" landmark that defines the very birth OF "alloy steels" as a class:

The "units" are actually the standard ones applied to metals in general.

Mangalloy simply knocks yer socks off at how far past "normal steel" it can go. See tensile strength, for example.

Mangalloy - Wikipedia

Manganese Steel - an overview | ScienceDirect Topics