Hardening Mild Steel

[RegionalChaos]

OK.. So I've heard that people make disposable (or limited use) tools out of mild steel, maybe a drift or something I guess. And I've heard people talk about hardening mild steel with things like SuperQuench. But my understanding was that in order to really harden metal, it takes carbon. And mild steel just doesn't have much carbon. I always wrote it off. Earlier I made a few tools from what I assume was mild hex bar. They bent or deformed when used on the one project I used them form. I may have let them get too hot without quenching (I honestly don't recall how much I quenched them while using) but to me, I wrote it off to them being made out of mild steel. Now I make my tools out of coil spring mainly.

Then, the other day I burnt the end of a bar I had just started working on. When I pulled it out it was sparkling and spitting, so just for fun, I submerged it straight into the quench tub. I thought maybe it would crack, and I hadn't seen that before. When it was cool, I figured I would cut off the end and start over. So I threw the end in my band saw. The saw barely scratched it. It removed the surface layer, then wasn't cutting beyond that. So it seems like the quench hardened the mild steel. So now I'm confused..

Can mild steel harden? Is it just that mild steel does not stay hard once it is hardened?

Thanks for any enlightenment!

[Hillbillysmith]

First off, to my knowledge (and I could be wrong), hex bar is tool steel, not mild. But to your primary question, yes mild steel can be hardened. Anything with carbon in it can be hardened. It's just the question of how hard. And the properties of the metal also depends solely on the rest of the chemical composition. Does it have nickel? Lithium? Vanadium? Columbium? Any other elements make a big difference. But just plain old mild steel, that I know of, will not get hard enough where a band saw won't cut through it.

[Jmercier]

Also keep in mind that modern mild steel is recylced many times over and usualy has much more alloying elements in it than older mild steel did. This can cause new mild steel to be harder (and harder to work) than much of the older stuff which was closer to a pure iron with limited carbon.

Mild steel (and even wrought iron) will work harden as well

[primtechsmith]

You can harden mild steel. By quenching it at high temperature you are making all the molecules that are racing around freeze up all of a sudden and almost crystalize....funny story. Early in my smithing life I made up a triangle dinner bell for a friend as a wedding gift. When she picked it up and rang it for everyone to see it fell into 2 pieces....looking back after I got over the embarrasment I quenched that corner of the triangle for one reason or another making it really brittle instead of throwing it down and letting it air dry.

I have also case hardened mild steel using Casenit(I think I spelled it wrong). With this stuff you just heat it up and rub this junk all over it and heat it again and then quench it. I think all this stuff is made up of is mostly ground up bone...not sure. I do know that thing is extremely hard. I have made several nails with that header and it is holding up just fine.

A neat disposable tool I have been told about is forging out your punch or drift, etc....and heating up some cast iron and rubbing it ff on the mild steel while they are both hot(in the fire)...then quench it. I have been told by a guy that has done this it will last up to 6 uses depending on what you are doing with it.

well.....I know there are several out there with better answers than this one. So I will let them get to it!

Peyton

[Mende]

Mild steel can be either case hardened ( a thin layer of carbon will be absorbed by the steel and it will make for a hard case with mild steel inside - hence the term) and WORK hardening. . .which is done by beating the steel until you compress the molecules together and it;s a bit harder than before. . .quenching undoes this. . .
Hex bars are often tool steel. And Vanadium, chromium and manganese CAN affect the hardenability of steel.

[RegionalChaos]

The hex bar I used was from the inside of rollers. It didn't really spark that hard. I made two eye punches. Both bent pretty quickly at first use, though I didn't harden them.

Thanks for the feed back all.

[Glenn]

Respectfully, I refer you to another thread on packing.

The whole thread on reducing grain growth is interesting.

[hdwarner]

you can buy hex stock in ledloy 12L14 OR 1018 so all hex is not tool steel
here is a link for heat treating Special menu bar
look under rob gunters super quench , there are many testimonials about his super quench that he can harden 1018 steel to cut itself
i heard he forged parts for nasa .
chuck
but as far as what i do i use the product casenite very succesfully

[evfreek]

Hi. I have "hardened" mild steel. It was a failed forge weld that got burnt. It completely defeated a file (Rc 60+). I later learned from a more experienced smith that burning metal causes it to leaf or string out, with very hard scale between the layers. This composite is very wear resistant but weak. It is useless as a tool. A grinder made quick work of the burnt end. A hot rasp will also work

If you want to make emergency tools, I would highly recommend "qualified" rebar. One of my students brought in a piece of new store bought rebar (it was cheaper than the steel from the big box rack). I spark tested it for him right next to a sample of A-36. The difference was striking. It was burstier than truck axle; looked like 1050 or better. It was also red hard, and made that characteristic "clank" noise below a high orange. We made a chisel, tempered one step to bronze, and it was hard. You could tell just by tapping the end. This stuff is cheap! And if it is no good, use it for bottle openers, or hooks or something. Another student made a really nice spring fuller out of rebar. He forgot to qualify it, then he forgot to temper it. It shattered on him. I made one out of "qualified" rebar, and it has fullered a lot of candleholders, letter openers, S-7 tools (careful, keep it hot), etc. Looks just fine.

[petersenj20]

I have been working on a machete made of mild steel and plan on trying the Super Quench. I will report my results when done.

I've seen the standard response to this, "why not use carbon steel?"
2 reasons. I haven't located a carbon steel supplier yet and since this is my first "knife" I don't want to ruin an expensive piece of steel.