Hardening Mild Steel

[Steve Sells]

why cant people use a hardenable steel in the first place, its like using chicken breasts and wanting to make it taste like steak

[Judson Yaggy]

It's just another arrow in the quiver.   I use it especially on one off or limited run tooling.  That saves me both material cost and time needed to produce the tool.  As an architectural smith I often make a tool for one job and then never use it again, and making that tool involves welding and machining more often than not.  Doing it in an easy to work steel saves a tremendous amount of time, and then superquench gives it a shot in the arm.  Taking a mild steel tool from being able to survive a few heats to a few dozen is very valuable to me.  

[jlpservicesinc]

Well said Judson..    

I have used it for years and years now on swages and they still hold up just like the day I made them..  

I too have found that working with mild steels saves so much time and cost.. 

From a working stand point.  The only time I use any other steel for my hot tools is when they will have to work in a hot state.   Swages barely get warm.  and once they are hardened with the carbon uptake method they stay pretty hard..   

I really should do a video on it, but then nay say'ers feed the trough and dismiss it as useless.   

In the Swage video I use the method and for just over 3minutes in the fire I end up with just over 32HRc averaged.    A longer time or adding more green coal to the hot fire would have raised it another few points..  On thin stock.. I've gotten to over 50HRc..     It's not a method I would use for knife or such unless it was the only thing I had in a survival situation and knew it was going to be throw away.. 

It does work.. 

[DennisCA]

I personally find this a very interesting topic. Clickspring demonstrated this process and I always wanted to try it but didn't have a forge or heat treatment oven. I thought it would have several applications when machining certain parts to be able to carburize and harden them, and I can see the use for blacksmithing too. Isn't it quite ideal for many tools to have a soft body and hard striking face for instance? 

 

 

[ThomasPowers]

Quite clear instructions on doing this are in "Divers Arts" written by the German Monk Theophilus around 1120 CE.  A good translation from the latin into english by Cyril Stanley Smith, (Noted figure in historical metallurgy studies), is available from Dover Books at a very reasonable price.

Not providing any sources how are we to know if the materials used and amounts are anything but modern guesses?  Use of hardened steel at that period should be documented rather than "guessed" as well.  As the bloomery process produces pretty much the range of carbon in wrought iron from zilch to cast iron use of case hardening instead of selection of higher C material should be proven as well.

 

[Mark Clifford]

I am making musical steel 'tongue' drums and am using mild, low carbon steel [CR4] and I need to harden the steel to get it to ring or 'sing'. Some say you cannot harden mild steel, some say you can case harden mild steel. If I heat to dull red and quench in water will this harden the mild steel? Is it better to quench in oil as this adds carbon in the process? When using homemade case-hardening compounds - flour/salt/carbon do you put the paste onto cool metal? One site said apply to hot metal but I couldn't get it to stick and if I do manage to cover the area to be hardened I can't see if the metal is heated to dull red! I just need to harden the steel then temper it to 'straw' colour [for visual effect and to counteract brittleness] so it doesn't have to be to 'tool work' standard. The discs I am working on are about the size of a small car wheel using 2mm mild steel. I aim to experiment with small  strips to test for filing and brittleness [presuming that means it has hardened]. Glad to hear any views/ideas.

[Latticino]

Case hardening isn't really what you want to do for steel tongue drums.  The extremely thin surface hardness layer doesn't have a significant effect on whether the tongue takes a set or not when it flexes.  In this case I think you would be better served work hardening the mild steel by cold hammering it to shape.  I think this is the typical technique.

I assume you mean this type of steel tongue drum:

Not a kalimba:

[George N. M.]

Mark, you will have to experiment with various techniques and sizes to get the correct tones.  For example, a certain size "tongue" when treated with process A may give you a D note and the same size treated with process B will give you a D flat note.

For hardening mild steel try "super quench" (google it).  It will harden mild steel as hard as it may be hardened.  While I know that it will harden mild steel I do not know how it will affect the "springiness" of it which will be the controlling factor for a tone when struck.

"By hammer and hand all arts do stand."

[dian]

so apparently 1020 steel after some intercritical treatment and quench in ice water will have:  uts 1280 mpa, 41 hrc, charpy 78 j. or: uts 935 mpa, 24 hrc, charpy 135 j. the structure will be ferrite + martensite and the secret is to find the right ratio.

now, the steel used in that experiment had a little more si than standart 1020 (0.46%) and was unusually purified as to s + p. no idea if that is some "dual phase" alloy or what. but even ordinary 1020/1018 should respond to such a treatment. if i had an electric oven i would run and try it. so no need for tool steel anymore?

something to contemplate for the interested: the steel got softer if the martensite fraction was large.

[jlpservicesinc]

Dian, that is interesting that the steel got softer with more martensite.  

[dian]

do you know the answer? its "simple".

[jlpservicesinc]

Not sure it's the exact answer your looking for and to give an educated answer would mean having to get out my metallurgy book, 

 

No time for that right now as I gotta get out to work.

 

So as an off the top of the head would be (plate vs lath) martensite.  

[ThomasPowers]

How are the wear properties compared to "tool" steels?  And  46 point steel is nowhere near 1020!

As to softer: is it like wootz where the hard carbides are in a soft matrix?

[Steve Sells]

On 2/27/2021 at 5:49 PM, Mark Clifford said:

Some say you cannot harden mild steel, some say you can case harden mild steel. If I heat to dull red and quench in water will this harden the mild steel? Is it better to quench in oil as this adds carbon in the process?

I wrote a few articles on heat treating, rather than make wild guesses,  I suggest you read some, they are pinned to stay at the top of the page.  One can not harden steel if it does not have enough carbon, because the act of hardening is trapping carbon in the iron matrix. which as I said many times can not happen if the carbon isnt there, and oil does NOT add any carbon, another myth, but case hardening does add carbon

46 points of carbon is very hardenable, its called medium carbon steel;  which is no where near 1020.

Mild does not function the same as tool steel, more myths, and from a cost perspective: tool steels would not be made if the mild would perform the same way, the additions of tool steels help in reducing grain growth, defining the grain boundaries, hardenability which is not the same as hardening and carbide formation

[Frosty]

dian: You are not talking to people who don't know the subject on a high level. People who manipulate steel and heat treatment on a professional level, some on industrial commercial levels. You will look better if you read some of the suggested material, maybe buy one of their books and actually learn what you're talking about. 

Your assumptions are based on opinions of people who don't know what they're talking about so your questions often don't make enough sense to be answerable in a meaningful way. It's making you look bad.

I'm not taking shots at you, I prefer to believe you actually want to learn this stuff and am making a suggestion that'll get you farther faster than just asking meaningless questions. Honest, we'd love to see you doing world class work so we can see the pictures.

We LOVE pictures.

Frosty The Lucky.

 

[dian]

no idea what you are saying, frosty. and no idea who came up with 0.46% carbon. i thought we might have a discussion on the hardenability of mild steel.

 

anyways, to answer my own question: as there is obviously not much carbon, a too large fraction of martensite means that its carbon content is low and it gets weaker.  apparently there is an optimal proportion of ferrite/austenite you have to aim for before quenching.

edit: jlp, there was no mention of the martesite type in the paper, but i wondered about this also. do you think there might be plate martensite at this carbon level at all?

 

[Frosty]

9 hours ago, dian said:

now, the steel used in that experiment had a little more si than standart 1020 (0.46%)

YOU came up with .46% and your pseudo intellectual ramblings so confuse the issues the experts are getting lost.  You'll be talking to yourself before long but you'll have an audience.

Frosty The Lucky.

[JHCC]

Steve and Frosty, the 0.46% in dian’s post refers to the silicon (Si) content, not carbon (C).

 On the other hand, this:

3 hours ago, dian said:

as there is obviously not much carbon, a too large fraction of martensite means that its carbon content is low and it gets weaker.  apparently there is an optimal proportion of ferrite/austenite you have to aim for before quenching.

is nonsensical. Martensite is what makes steel hard, so (very broadly speaking) more carbon = more martensite = harder steel, not softer.

Now the whole point of Super Quench (as I understand it, and I’m ready to be corrected as necessary) is that it cools the mild steel so quickly that its small amount of carbon doesn’t have time to form cementite, but instead forces the formation of martensite. In other words, the “nose” on the TTT chart for mild steel is so small that regular water or oil quenches aren’t fast enough to hit it. By reducing the surface tension of the water and thereby reducing or eliminating the leidenfrost effect, Super Quench pulls the heat out of the piece fast enough to hit that nose. 

(But as I say, I’m ready to be corrected if that’s not correct.)

[Steve Sells]

cant make Martensite if there isnt enough carbon available to form it, no matter how fast the temperature change. Super quench helps to form it from what is available,  but that is no substitute for having enough martensite

[Frosty]

1 hour ago, JHCC said:

Steve and Frosty, the 0.46% in dian’s post refers to the silicon (Si) content, not carbon (C).

Did you read the part of dian' post I quoted? 

The nonstop nonsensical nature of his posts is what's causing confusion even in experts. 

In my analysis it's looking like we're being trolled.

Frosty The Lucky.

[JHCC]

Yes, I saw it. I’m just trying to make sure that we criticize what he did say, not what he didn’t say.

[JHCC]

1 hour ago, Steve Sells said:

Super quench helps to form it from what is available,  but that is no substitute for having enough martensite

That’s what I thought; thanks for elaborating. 

[anvil]

Trolls, may they remain on Facebook.

[Buzzkill]

22 hours ago, Frosty said:

On 6/13/2021 at 4:34 AM, dian said:

now, the steel used in that experiment had a little more si than standart 1020 (0.46%)

YOU came up with .46%

He was referring to Si with the .46%.  I added the bold and underline to make it stand out.  That doesn't mean the rest of it holds water.

While it doesn't amount to irrefutable proof to the contrary of the rest of his claims, I'd bet that people in the steel industry would be using hardened mild steel if it was an appropriate substitute for high carbon steel.  The funny thing about businesses is that those which survive tend to be the ones that waste as little material and energy as possible while starting with the least expensive raw materials that will be adequate for their purposes.  With the steel industry being a massive world wide sector, I feel fairly confident that if mild steel could be sufficiently hardened to the point where it could substitute high carbon steel we'd know about it and it would be the industry standard.

Can mild steel be hardened?  Sure, to some degree.  Can it take the place of higher carbon steel for specific applications?  Not likely.

[ThomasPowers]

I believe I was the person who read that wrong as the .46 was not directly associated with the Si and I  assumed that that was the C content as that is what we are usually arguing over.