Case Hardening

[LeMarechal]

Hi to all the blacksmiths out there,

got one or two little questions about case hardening and I hope someone can give me some enlightenment

I´ve heard that there should be a loud cracking sound if you make the final cooling in water. Ok, sometimes I got it, sometimes not. From what does this cracking sound depend on? And is it important for getting good results?

Usual heattreatment needs different tempering, depending on what is the final use of the work. If it comes to case hardening is tempering necessary too, in that case(pardon the pun)?

And finaly:

what is the right way for case hardening?

Polishing the piece/ red heating /applying the case hardening powder.. and then???

Greetings from Germany

Sascha

 

 

[ThomasPowers]

There are many ways to case harden for many uses. I suggest you try to find a copy of "The Cementation of Iron and Steel" Federico Giolitti; it can be found as a free download on the net.

Without knowing more about what you are trying to accomplish, what you are starting with and what the case hardening powder you are using it's hard to give an answer that will make sense.

[LeMarechal]

Hi Thomas,

thanks for the tip. I´ll try to find a copy soon.

I found here an case hardening compound that seems very similar to Kasenit. There is only a very short -how to- on its packaging.

Something like: Apply at red heat, wait a little and then take once more to a heat, then quench.

 

Ok, if it´s just how it is then I´m ok with it :)

But I can´t believe that things are so simple???

 

What I like to do with it is to surfaceharden some easy tools like leaf crimping stakes or hardy swages with simple shapes.

I wonder if I have to keep the piece at redheat for a while after applying the compound. Because After strewing the poder on

there is a crust on the piece and the longer I keep it at red heat temperature the crust disappears gradually. Is that good? If yes, how long should I wait befor quenching?

You see realy basic questions :)

 

Greetings

Sascha

[ThomasPowers]

With case hardening the longer time at temp the deeper the carbon migrates; however also the more the compound is subject to exposure to the atmosphere as well. Also the longer at higher temps the more things like grain growth can occur.

You would need to experiment to see what works best for you using your materials and methods; HOWEVER higher carbon steels are so easily sourced in the scrap stream (car axles, coil and leaf springs, etc) that it might not be worth the effort for items that will see a lot of use and something like using Gunther's super quench may work for items not expecting much use.

[John B]

2 hours ago, LeMarechal said:

I found here an case hardening compound that seems very similar to Kasenit. There is only a very short -how to- on its packaging.

Something like: Apply at red heat, wait a little and then take once more to a heat, then quench.

But I can´t believe that things are so simple??

Yes it is that simple, the "Red Heat" wants to be a top end of the red spectrum, put your powder on, reheat and quench in clean water.

Before case hardening powders were available, one of the methods used was:

Take a spoonful of wholemeal flour, add two spoonfuls of salt, add a little water and make into a smooth paste,

Heat the end of the item to be hardened until the paste will stick to it,

When you have the item coated where you want it, heat the area to a bright red heat, and plunge the item into cold, clean, soft water and agitate while cooling.

The coated area will be appreciably harder.

Case hardening is to add wear resistance, and is not suitable for edge tools, ideal for increasing longevity of tooling made from lower carbon steels

[Irondragon Forge ClayWorks]

I've used Kasenit quite a bit to case harden old flintlock parts like the frizzen and other lock parts and John B is correct, it's really that simple.

[evfreek]

Hi Sascha.  I just saw a demo at the California Blacksmith Association spring conference.  Mark Aspery was giving it.  He said you could purchase "Cherry Heat" hardening powder from Pieh Tool.  I don't know if you can find this in Germany.  Indeed, there was a sharp crack when Mark swung the piece into water for a rapid quench.  Then, he showed how it skated a file.  I think that the crack is an indication of two key factors for successful application of the agent.  First, a smooth and completely fused coverage showing that the surface hit the active temperature and that there was enough to both treat and protect the surface from decarburization.  Second, contraction of the freezing shell combined with expansion of martensite being formed would contribute to the crack noise.  Of course, he showed how a file skated after the piece cooled, but the crack was much more graphic.  Nobody disputed that the surface was hard after the familiar skating noise from the file.

Have fun.  I haven't had much luck with those dumb homemade pastes like sugar, salt and flour.  I think that those are for pack hardening, which requires quite a bit more patience and fuel.

[John B]

1 hour ago, evfreek said:

 

. I haven't had much luck with those dumb homemade pastes like sugar, salt and flour.  I think that those are for pack hardening, which requires quite a bit more patience and fuel.

You may not have had much luck, but the salt and wholemeal flour works, and was the method used before the commercial powders were available or even thought of, and a lot less costly.  It is a method I regularly used, as Kasenit over a period of time, tended to rot out the containers it came in, and no better results were achieved.

Please dont Dumbify it just because you cannot get it right, it's not a matter of luck, it's patience and application.

Pack hardening requires carbon rich materials to be in the container in close proximity with the item to be treated, and a long soak is required for results.

[ThomasPowers]

Theophilus, in 1120, suggested greasing the piece and then wrapping it in thin leather and encasing it all in well kneaded clay and heating to red and dumping it in water. ("Divers Arts")

[John B]

Hi Thomas, Iam not old enough to remember bumping in to Theo for a discussion, but the iron then was fundamentally different to the metals today.

One of the main problems these days is that some want immediate results without the hassle of working through things.

That is one of the objectives of this site, we pass on our experiences so that others don't have to start from the very beginning each time. Unfortunately it is still expected to give instant results, and that is not always possible, they have to put some effort in.

If you try describing "Cherry Red heat" to a colour blind person, (or anyone else ) then that is not particularly helpful.

However if you show and demonstrate  the heat colour to them, they can better assimilate what you are trying to convey, and thus achieve the result required.

There are no APPS available for blacksmithing that I know of yet, so it's listen look and hands on.

Here in the UK that is one of the reasons for the National Blacksmiths Competitions held at 10 major shows, it gives interested parties the opportunity to see a wide range of forged items, Traditional and modern, sculptural and artistic, and the chance to see a range of 'smiths working live making named items in a specific time range. What some of these competitors achieve is phenomenal and definitely educational for picking up tips on tooling and techniques.

Have fun, get it HOT and hit it.

[JHCC]

5 hours ago, John B said:

Iam not old enough to remember bumping in to Theo for a discussion

Wasn't he at the last QuadState?

[Frosty]

Theo's a member here, he's pretty busy but usually gets back if you ask him something. Maybe Devon John is younger than I thought.

Frosty The Lucky.

[Steve Sells]

I thought they were talking about Theophilus

[Frosty]

[ThomasPowers]

Well some of us were and some were not....evidently.  I've had folks ask me if I attended Tubal-Cain's bris before....

[LeMarechal]

Thank you all for your comments!!!

@JohnB,

ok, then I will try not searching difficulties where things are easy (hope this joke works in english).

You know, in much cases there is something that sounds very simple an easy, and if you try it out you will see a lot of these little things you have to know, in order to be successful. And so I was a little distrustful....

But now I´m a bit smarter.

Because of the low thickness of the hardened surface, tempering is not an issue... right?

Greetings and thanks once more

Sascha

[Steve Sells]

7 minutes ago, LeMarechal said:

Because of the low thickness of the hardened surface, tempering is not an issue... right?

Why would you think that? did you read the pinned posts on heat treating?

[LeMarechal]

33 minutes ago, Steve Sells said:

.... did you read the pinned posts on heat treating?

Hi Steve,

 

yes I searched there for notes on case hardening, may be that I´ve overlooked something.

I am knowing about the general correlations between hardening, tempering(colours) and the danger of inproperly heatreatment - in relation to tool steel.

But this thing with case hardening, especially with case hardening compounds like Kasenit, is realy new to me. I´ve red somwhere that the thickness of the hardened layer is only a fraction of a milimeter, more like a hard coating (case hardening mild steel). And so I asked for tempering because I never heard anything about it in relation to case hardening, using compounds.

 

PS: If I´m using aloyed tool steel I don´t touch it without privious reading the product data sheets of the manufacturer.

[John B]

44 minutes ago, LeMarechal said:

 

Because of the low thickness of the hardened surface, tempering is not an issue... right?

Sascha

Case hardening is as you rightly say a hard coating, it does not lend itself to tempering as Hardening and Tempering back affects all of the item not just the surface.

[Steve Sells]

but he needs to be aware of the parent materials carbon content,  if he is using high enough carbon steels, then after the quench he sill has to temper to relax the martensite

[John B]

Agree entirely Steve,  One of the problems using steel of an unknown specification,  but if he is using hiigh enough carbon steel, then no need for case hardening, surely it would be a straight forward Harden and Temper to required state for tool's usage.

 

[Frosty]

How about making a test coupon and testing BEFORE looking for a workable heat treatment?  

Frosty The Lucky.

[jlpservicesinc]

I've never tempered an item that has been case hardened that was in use for anything other than a knife-like object. Swages, frizzens, screws, punches, etc, etc get no tempering. 

Making a knife with case hardening does get a temper simply because of the thinness of the blade. 

 

Years ago one of my friends came over to make a knife and he grabbed a piece of mild steel.  I told him it would not work and he said he did not care.  In the process, he overheated it several times and I figured it would be weak with no chance of hardening.  Anyhow, it hardened up just fine and that blade was used for driveby bush cutting. the blade lived a full life both never bending or breaking and it even held a decent edge. 

I surmised that the metal when overheated picked up ample carbon to in fact harden and since then have used the process to good merit on swages and the like.  the metal will, in fact, etch out with a layering typical of case hardened steels.  the largest problem is the amount of heat and temperature needed to do the process and the dismissal by most as ineffectual also coming back with the fact that the steel has no known level of carbon in the matrix. (no way of telling how much carbon).  The items will skate a file easily. 

[pnut]

What works in the real world and what's supposed to work are sometimes two very different things.

Pnut (Mike)

[pnut]

14 hours ago, Frosty said:

How about making a test coupon and testing BEFORE looking for a workable heat treatment?  

Frosty The Lucky.

Best advice so far.

Pnut (Mike)