Blueing and case hardening

[Dobson]

Hi everyone, anyone know about case hardening? I have a knife makers furnace (its a vertical 4inch tube that you hang blades in to heat them in the hardening process) that is temperature controlable could i use this? What is the process? What is the chemical/stuff i use to case harden. Trade names are ok but i live in south africa so chemical names could be better.
Also:- I read this month in Muzzleloader that Mike Nesbitt blued a barrel using Laurel mountain forges barrel brown (now i have some of this) and boils the barrel between coatings of browning and degreaser. I have no degreaser. Has anyone tried this does it work? Any info would be helpfull. I have shyied away from charcoal blueing (which was my original plan) due to warnings about warping the barrel under high temperature. Just plain got cold feet, and didnt fancy a bent barrel to straighten even if it can be done.
Regards to all.
Dobson.

 

[benvenuto]

http://en.wikipedia.org/wiki/Case_hardening

You can either pack your metal box with ground charcoal or a commercial case hardening compound. The one I use has boron in it and is quite toxic so be careful! You need to get to a bright red heat and keep it there...about 800°C... for at least several hours. I forget the exact rate of the formation of the hardened skin, somthing like 1.6 mm per 12 hours?

If the barrel you are using has been stress relieved after machining, there should be no danger of warping when charcoal bluing :thumbsup:

 

[J.D.]

The Wikipedia site is mostly right, but there is a LOT of misinformation there too.

I assume that you are talking about case hardening parts for durability, as opposed to color case hardening. The process is essentially the same, but color case hardening presents a whole new series of problems.

Clean, well charred charcoal is all that is necessary for case hardening with the type of furnace that Dobson describes. The furnace might ba a little small, but it should work for really small parts.

The leather,hooves, and bone mentioned in the Wikipedia article can be used, but they need to be charred first, and added to the wood charcoal.

The container doesn't need to be all that well sealed either. The container needs to be full of small bits of charcoal surrounding the part to be hardened. Ideally, there should be no air spaces in the container. The lid needs to be a loose fit that will fall off of the container as the contents are dumped into a vat of warm water.

A search on case hardening should bring up a few articles that would be of help.
J.D.

 

[LRB]

I use an anti-scale/decarb powder that is almost all boron. Before I used it I researched it. Everything I found on it said boron had no known health risk, other than some people can have
respiratory problems when it's inhaled, but quickly recover when removed from the source of exposure. I use it with a cross ventilation condition, and have never had any reaction at all.

 

Also:- I read this month in Muzzleloader that Mike Nesbitt blued a barrel using Laurel mountain forges barrel brown (now i have some of this) and boils the barrel between coatings of browning and degreaser. I have no degreaser. Has anyone tried this does it work? Any info would be helpfull. I have shyied away from charcoal blueing (which was my original plan) due to warnings about warping the barrel under high temperature. Just plain got cold feet, and didnt fancy a bent barrel to straighten even if it can be done.

This is what is known as cold or rust bluing - it is documentable to at least the 1780's if that matters. The "easiest/best" way to achieve this is to get the Pilkington kit from Brownell's - it comes with full instructions on how-to. The LMF will also work (it is both a "browner" and degreaser. When the browned metal is boiled it changes the nature of the browning from the red/brown stage to the blue/black stage.
This method is still used on high end guns such as H & H. It is VERY durable - something that can't be said about charcoal/heat bluing.

 

[44-henry]

Your furnace should work fine for small parts, but it isn't ideal. I currently use a Neycraft furnace with about a 9" square chamber and that is still too small for a lot of parts. I solved that problem by ordering the larger furnace that Brownells sells which will be very nice when it arrives.

If you are talking about bone and charcoal color case hardening than you will need a few items. For starters you will need some kind of crucibal which can be iron, steel, graphite, or even clay, but this is a must. Next you will need a supply of bone and wood charcoal. You can make these easy enough, but your results will probably be less than consistant. To get really good results use a proven pure quality charcoal like that sold by Brownells. If you check back in the archives there have been several threads concerning this subject and I have provided some picture tutorials of the process which should help. Lots of luck, it is a fun, challenging, but doable project.