What's your prefered method of hardening mild steel?

[Muddy Creek Sam]

Just learning to work with my lathe and mill.

Thanks,

Sam

[elk hunter]

Generally speaking true mild steel has such a low carbon content that the only way to harden it is to case harden it by either pack hardening or in a controlled atmosphere furnace with carbon in some form in with the steel. If I do have to harden mild steel I use some type of pack hardening compound. Case/pack hardening compounds are available at your local welding supply. Normally if I need to make a hardened and tempered part, I use a steel that can be heat treated and is appropriate for the part.

[JMtoolman]

Sam, get a can of Casinite, it's a powder that you roll a red hot piece of mild steel in, then keep it hot for a minute. Quench in water and it is casehardened. The longer you hold the steel red hot, the deeper it penetrates. I've been using the same one pound can for over forty years, and still have about half left. The toolman.

[Mooseman]

Thats Kasenit...http://www.dixiegunworks.com/product...oducts_id=6465

[Reload3006]

Elk Hunter is right on. You can not harden mild steel per se but you can case harden it. The old blacksmiths used to heat it up in the forge until it was white hot and stick it in a bucket of bone meal. The way we do it here at work is put it in a basket of carbon chunks put it in a furnace heat it to critical allow it to soak for the prescribed time take it out and quench it in oil. then temper accordingly. it will only harden to a depth of no more than 1/16 inch

[John Taylor]

Many years ago the Dixie catalog had a story about wrapping a frizzen in leather and "cooking" it in the coals then quenching. I tried it and it works. Bone meal, leather and charcoal is what the old boys used for color case hardening. Kasenit works good also, no color. If I need something tough I usually by a piece of 4140 heat treated and machine what I need. Small parts get machined from barrel ends which I have plenty of. I have made cutting tools from parts of barrels, that can be made harder than a file.

[Beekeeper]

Not to hyjack Sams thread but what kind of furnace do you need to do case hardening?
What are the pitfalls?
Would like to try it but in truth don't know where to start!
Point me in the right direction and boot me one to get me started!!

beekeeper

[Reload3006]

all you need is a furnace that is capable of the temp your looking for you dont need atmospheric control to case harden. a box to put the part in and Carbon chunks bury the part in carbon chunks and depending on the size of the material is the soak time. Most Steel sellers will have heat treat charts and they will have case hardening times too. Soak for prescribed time pull out of furnace and quench in Oil.
http://www.2nd-hardener.com/casehardening.htm
this site kind of explains it a little but doesn't list soak times.

[W.R.Buchanan]

The only problem with the carbon transfusion methods like Kasenit is the clean up afterwards. There is a lot of scale left on the part that almost has to be removed by media blasting. Also it will alter dimensions,,, so if it is a closely fit part you have to allow for that. It takes alot of reheats and dips into the kasenit to achieve even .010 of penetration,,, Thats all Mauser actions had anyway.

Best to make the part out of some kind of good material in the first place, that way these problems don't rear their ugly heads.

O1,,, Oil Hardening tool steel is readily available from any tool supply house or McMaster Carr in a variety of shapes and sizes. You heat that material with a torch until it is red , not orange, and then quench it in a bucket of oil. If you are lucky the scale will pop right off and your part will be ready to put in your wifes oven to draw it back.

The hardening process makes the material fully hard, (with O1, that is 63 Rc) then you must draw if back , or" temper it" by reheating it to a lower temp and holding it there for a specified amount of time depending on the level of hardness you want. This step removes the brittleness from the material.

All of the information on heat treating different metals is readily available on the web. You need to figure out if you can do what is needed before you make the parts, as all metals are somewhat different.

Any of the tool steels above O1 require hardening in a vacuum or inert gas furnace to come out right due to the high hardening temps which are well above the point that the carbon will precipitate out of the material if exposed to oxygen.

Any of the Cro-Moly steels harden just like O1 IE heat to red and quench in oil.

The typical soak time at or slightly above hardening temp for all steels is 2 hours for every 1" of thickness. IE: a 1" cube of o-1 would need to be held at about 1500F for 2 hours, then quenched in oil. The actual hardening temp of O1 is 1450F, however you must get it a little hotter so that the "entire piece" "sees" the hardening temp inside and out. A 1/8" thick knife blade would only need to be soaked for 15 minutes not counting the time it takes to get to temp, so figure 30 minutes in the oven total or about 18 minutes under the torch.

The reason I spoke of O1 is because 1450-1550F is about all the higher you can heat something in the open atmosphere before you start getting "Carbon Precipitation" which is when the carbon starts coming out of the alloy. You don't want this, as the carbon is what is making the material hard in the first place.

Hope this helps your understanding of the process, It is not hard to do if you have the right stuff to do it with, and like said above the Kase-nit method is the simplest way to get a result, it's just not the best way.

Randy

[Reload3006]

O1 is the easiest tool steel by far for the home gunsmith hobbyist etc. maybe an easier steel if you have an oven is A4 or A6 because they are air hardening. you dont need to quench them .. But they don't draw back as well. so you could still be very hard then all of a sudden your annealed and too soft again.

[Muddy Creek Sam]

I am assuming what I have is mild steel, It was given to me by a friend that was working at a plant that made hammers. It is 4' long and 1" diameter steel rods. No way of checking as he no longer works there.

Sam

[Norbrat]

I am assuming what I have is mild steel, It was given to me by a friend that was working at a plant that made hammers. It is 4' long and 1" diameter steel rods. No way of checking as he no longer works there.

Sam

Hammer heads wouldn't be made from mild steel.

You can get an idea of what type of steel it is by observing what sparks you get from it when you grind it on a bench grinder. http://en.wikipedia.org/wiki/Spark_testing

[Muddy Creek Sam]

Hammer heads wouldn't be made from mild steel.

You can get an idea of what type of steel it is by observing what sparks you get from it when you grind it on a bench grinder. http://en.wikipedia.org/wiki/Spark_testing

Thanks, Norbrat,

Will have to give that a try, I got 8 or 10 pieces of that.

Sam

[Reload3006]

Thanks, Norbrat,

Will have to give that a try, I got 8 or 10 pieces of that.

Sam

are there any markings on it? you can kind of find out what it is by acid testing etc. you can also get a vague idea by spark testing too.

[Muddy Creek Sam]

are there any markings on it? you can kind of find out what it is by acid testing etc. you can also get a vague idea by spark testing too.

No markings at all, Painted Black.

Sam

[Reload3006]

well one thing you can do and if its medium to high carbon steel it will tell you right off. Saw about a 1/4 inch or less off the end. Heat it with a torch to cherry red maybe a little hotter close to white the quench it in oil or for that matter water. if it comes out harder than a file can cut it you know it can be heat treated and go from there. If it stays soft then you know you have to case harden it.

[John Taylor]

well one thing you can do and if its medium to high carbon steel it will tell you right off. Saw about a 1/4 inch or less off the end. Heat it with a torch to cherry red maybe a little hotter close to white the quench it in oil or for that matter water. if it comes out harder than a file can cut it you know it can be heat treated and go from there. If it stays soft then you know you have to case harden it.

I do this quite often, just slice off 1/8", heat it till red and quench. You only need to heat up one edge so it can be held with pliers. Use an old file, don't want to cut a groove in a good file, don't ask.

[mstarling]

Searches on Google and Yahoo indicate that hammer heads are indeed heat treated. The only reference I can find to an actual number is abt Rc 50 ... is pretty hard but won't be too brittle. Certainly not possible for a truly mild steel.

I would ask the nice fella that provided the steel to what hardness they are heat treating their hammers.

If you do a simple check for the ability to harden, be sure to get the material hot enough that it becomes non-magnetic. If you do not, it will not harden.

Half ATF and half 30 wt motor oil makes a good quenching medium for such a test. Be warned ... you will have a bit of smoke and potentially a little fire as you dunk the material.

Am a knife maker and use computer controlled molten salt pots to do reproducable heat treating as tested with a bench top Wilson hardness tester.

[andremajic]

Yep, the good ol' spark test can give you a pretty good indicator of the carbon content, but it's not exact. They used to use it at scrap yards as a quick way to tell what they got.

It's pretty quick since all you have to do is start the grinding wheel and touch the steel to the wheel for a second.

Andy.

[DCM]

Sam heat treating can be very simple to very complex depending on what the intended end use is.
It can be as simple as heating with a torch to cherry red and quenching in water, brine, oil etc. to heating a certain type of metal in a furnace with a specific atmosphere maintained in that furnace for many hours.

For most home/ hobby projects a heat and quench will do ya, but some things are best left to the pros.

I would highly recommend getting a good book on this subject. Water quenching can make an extremely hard but brittle surface. Again the intended application is very key here.

My personal ready reference on this is a metallurgist friend I have a good book berried here somewhere, but it is too easy to pick up the phone.