Heat Treating

[PS_Bond]

Here, finally, is the scan of the articles Mike Lamprey wrote back in '96 for the UKBA.

Copyright remains Mike's, however he has kindly allowed me to reproduce it here for general consumption.

Thanks also to Nigel for putting the thing somewhere accessible!

Mike Lamprey HT pdf (http://www.lingings.net/mike_lamprey_HT.pdf)

[bagman]

Peter - you have some page duplication in your pfd :eek:

[PS_Bond]

One of us is going doolally.

Me!

It looks as though I double-pasted the first half in. Oh well. And that's after the author proofread it too!

As soon as it is convenient to Nigel, we should hopefully have the right version up...

[PS_Bond]

And now... The new, improved, not-cut-and-pasted-multiple-times version. Same link.

Oi, Mushi - you reading this?

[MushiSushi]

Oi, Mushi - you reading this?
YES SIR!;) :p

I notice that Mike's diagram has the burner outside the outer hole? ..... I think I would put it inside and have a dual feed of propane (inner) and air (outer)..... it's also a bit faint and blurred even when i magnify ... I saw a burner design that was quite simple it was basically a tube with in a tube with the outer tube having strategically placed tubes welded perpendicular and the inner tube having small holes in line with the perpendicular outer tubes ... i'll see if I can find the diagram somewhere.

I think a lot of small exhaust ports might be a better idea than just one. mike's drawing (just an initial reaction) looks like it would have a heat difference from right to left. seems somewhat out of balance, or maybe that's just me and my discerning sculptor's eye and a penchant for balance and symetry.:confused:

[Pete E]

Thanks for posting the info.

I am new to all this, but I have been looking on the Net at various DIY small gas forges with a view to heat treatinging rather than welding.

I have never noticed the use of a "muffler" before and on the other designs, the burning propane seems to be in the main forge compartment even if it is not directly playing on the blade.

Also what about the guys who directly heat a blade with a propane torch when drawing back for instance??

Mike warns against using a direct propane flame noting it can weaken the steel..

So is this a big deal? Just a problem on certain steels?

Also, I notice he advocates wrapping the blade in stainless steel foil I assume to reduce scaling? Where can you get this and is it expensive?

Regards,

Pete

[PS_Bond]

Mike can probably answer this somewhat better than I can... I dunno, I haven't built one. Yet.

The burners are, AIUI, standard propane burners. Nothing fancier, like venturi assisted monstrosities. Given they tend to be brass, keeping them out of the kiln is probably a good idea...

The image is probably a bit blurry due to it being scanned at 300dpi and downsampled by the pdf printer to 96 dpi - which wan't very well written, from the looks of things. Blasted thing. I can email out the 300dpi version if needed, but I think you got the jist.

I would imagine that the heat is fairly even within the muffle, but you could always add burners on.

Stainless foil is far from cheap; I picked some up from TKS in my last order. It will keep oxygen from getting to your blades at elevated temperatures, so should prevent the worst of the scale.

[MushiSushi]

you still looking for an anvil Mr Bond? ... I noticed one in the london loot for £20

Blacksmiths anvil,
small,


Contact details: 020-8422 8749

Price: £20 .

Ad age: 7 days old

[Martyn]

made a duplicate of this and uploaded to the britishblades site, notw it's in two locations so we shouldn't loose it.

duplicate of Lamprey_Ht_pdf (http://www.britishblades.com/mike_lamprey_HT.pdf)

[CAL G]

After receiving many blades back with pits and especially my damascus I decided to build my own salt heat treater. Here is the basic procedure and some of my equipment.
About four years ago I was persuaded to build a salt heat treating furnace .I was a little leery at first because of the fact that it can be extremely dangerous. Anyway I proceeded to gather the parts and construct a salt pot. I have most likely heat treated over 150 blades in it and am convinced it is the only way to heat treat knives.

Bill of materials for construction:
- Piece of 10 –12 inch diameter pipe xxx long
- Piece of 4 inch diameter STAINLESS pipe xxx long
- Burner for the pot (I use the same burners that I designed for the forge)
- Temperature probe
- A volt meter that has a temperature function
- Propane regulator for the burner
- Some salt to put in the pot

Construction of the salt pot is basically like building a vertical forge. You take a piece of pipe weld a bottom in it, weld in a fitting for the burner and insulate the inside of it.
This design is essentially two tubes, one inside the other. The inner tube (salt pot) is thick, high quality stainless steel (316) with a plate welded to the bottom.
I would recommend a piece with about a 5/16 to 3/8-inch thick wall. Inside the pipe, I welded a short piece, about 8 inches long, of ½ inch stainless tubing for the thermowell to be placed in.
I placed my burner inlet in such a way that if the salt pot ever sprang a leak the molten salt would be contained inside the pot.

My pot has a lid that bolts down to the top of the pot. This really is not necessary but does come in handy if you want to remove the pot from the outer body and I have a stainless rod that hangs down from the center of the lid to the bottom of the salt pot.
This rod acts as a heat sink and during melting of the salt it ensures an even melt and prevents voids in the salt that could cause an explosion of liquid salt. Once the salt is melted the rod and lid are removed from the pot.
Because the pot is heated with propane there must be an exit chimney to vent the gases. I used a 3-inch square pipe for this with an adjustable damper mounted on the end. The chimney serves another function, it is flat and I use it to pre warm the blades before putting them in the hot salt.

http://s420.photobucket.com/albums/pp286/CALFORGE/SALT%20HEAT%20TREAT/

Salt pots are usually classified as either HIGH TEMP or LOW TEMP and this is determined by the type of salt you use or in other words the melting temperature of the salt you use. I only use my salt pot for heat treating and not tempering. The salt I use is Potassium Chloride or Potash, it has a melting temperature of 1418°F and at 2822°F it sublimes, which means it turns from a liquid to a vapor without boiling. Stay away from Barium type salts some of them are poisonous and will kill you.

Heat Treating Salts

Sodium Chloride NaCl 1473.8°F(melts) 2575.4°F(Boils)


Potassium Chloride KCl 1418°F(melts) 2822°F(Sublimates)

Advantages of heat treating with salt:
- Even heating, faster heating by 4-6 times than convection heating
- Upon entering into the salt bath a cocoon of frozen salt forms around the
knife. As a result of this the blade is subjected to an automatic preheat.
- Better temperature control
- Because you are in an inert atmosphere there is no pitting of the blades. I
finish my bladed to 600 grit, heat treat and then just clean off the tarnish
stain
- Blades tend to be straighter because they are hung and heated vertically
and are more buoyant in the salt which helps prevent warping

The only disadvantage is that it can be EXTREMELY DANGEROUS if you don’t follow good safety practices.
- Avoid any type of moisture around molten salt, it will explode. This includes
a drip of sweat.
- Do not heat treat without pre warming the blades to make sure they do not
have any moisture on their surface.
- Do not put steel with rust or scale in the molten salt
- Wear protective clothing such as leather jacket and apron, hard hat with a
good quality facemask, high top leather boots and good quality gloves.
- Salt or any other liquid at 1418°F is not something you want on your skin

If you are interested in salt heat treating there are a few good links on the Internet they can be found at:
http://www.mstarling.com/salt_pot_design.html

[MushiSushi]

wow ... :D that's an old thread you've found, Cal ;)

nice clear bit of information

[CAL G]

I see that now. When I opened up CUTLERS FORGE today it was sitting there so I added my reply.
I am still new at figuring out how this thing works. Maybe I should stick to making blades rather than looking stuff up on BB.
Here is some of my forging equipment and knives I have made.
http://s420.photobucket.com/albums/pp286/CALFORGE/FORGING/
http://s420.photobucket.com/albums/pp286/CALFORGE/

[lilzee]

Maybe I should stick to making blades rather than looking stuff up on BB.


it'll save you money in the long run. ;)

[MushiSushi]

Maybe I should stick to making blades rather than looking stuff up on BB.

Judging by the excellent way you put your post and explanation together, I for 1 would like to see you stick around here. :)

[MushiSushi]

:happy15:

and now having looked through your photobucket albums, I'm even more sure that you should stick around

:love29:

[MushiSushi]

Having said that, I would have liked to have seen you wearing a full face mask while using the salt pot, even if you have been using them without incident for the last 4 years or so :yikes:

[MushiSushi]

I've got a few questions for you, Cal;

do you build your own venturis?

did you build the press yourself? (and do the AutoCAD?)

is that salt pot the same one you built 4 years ago or has it had a number of incarnations?

I've enjoyed looking around your photos, some lovely knives.

especially this one;

http://i420.photobucket.com/albums/pp286/CALFORGE/BOWIE20101024X768.jpg

[jrmy0641]

beautiful knives, Cal

[CAL G]

I've got a few questions for you, Cal;

do you build your own venturis?

did you build the press yourself? (and do the AutoCAD?)

is that salt pot the same one you built 4 years ago or has it had a number of incarnations?

I've enjoyed looking around your photos, some lovely knives.

especially this one;

http://i420.photobucket.com/albums/pp286/CALFORGE/BOWIE20101024X768.jpg

Simon, to answer some of your questions.
I did design and build my own burners.

http://i420.photobucket.com/albums/pp286/CALFORGE/FORGING/1INCHBURNER1024X768.jpg

I did design and build the press. The auto cad drawing was done by my son. When I graduated engineering we still used slide rules and compters were IBM cards with Fortran programming.

The salt pot is exactly the same with no modifications, in fact I just used it last Saturday.

To me, knife making and forging is about making the equipment as well as the knives. I have been lucky enough to have the welders and lathes to do this.


Here is what Raymond Richard from Oregon had to say about my burners.

Hey Cal,

I just got back with a new regulator and gage. Got the burner hooked up and my first impressions are without having it in a forge that it’s better than the XXXX burners and most likely better than all his burners.
I've got it set at 2 pounds pressure or less and I'm thinking it will be just fine for the type forging I do with the small forges I use. I'm going to change cloths and go give it a test run. I'll let you know what I think after I give it a trial run but I'm thinking I may even be more impressed after I use it.

Ray


Cal,

I did some forging yesterday with the new burner. As far as I'm concerned it’s the best venturi design burner I have ever used. Hard for me to tell exactly how much gas pressure I was running it at but I don't think it was more than 1 1/2 pounds. A local bladesmith was over and he thought it was burning a little rich. He thought I should try a smaller orifice. I went to get the number 60-drill bit I had and found out it was a 57 like you used.

Ray


Thanks for the comments Simon here is a photos of my latest knife picture..

http://i420.photobucket.com/albums/pp286/CALFORGE/800%20x%20600/8002TIGERSMOKE2BIGREVERSED.jpg

[aaronblacksmith]

does anyone here heat treat in the forge? charcoal/coke etc

[Everything Mac]

some times yes. - but not for knives any more.

I heat treat blades using gas nowadays as I was having too much trouble getting decent even heat.

atb
Andy

[Dave Budd]

when I'm deomnstrating at shows and using my Iron Age or Roman forges for teaching, then yes I heat treat in teh forge (charcoal, back blast). I used to use my coke forge (bottom blast) with a pipe in it to give me a clear space, but these days I use a temperature controlled gas forge ala Don Fogg

[lemmythesmith]

I always heat treat using a forge-got nothing else!! Never use anything other than water for quenching, done three blades in oil in twenty years. ;)

[jamiemackie]

I dont anymore but have done loads of times.

I found the best method for smallish blades is to get a tube and put that in the forge and HT in that, much more even. Also when you put the fuel in make sure its small chunks no bigger than an inch square, too big chunks and youl get an uneven heat plus if your using clay big bits will pull of the clay which is very very annoying.

Jamie

[Stuggi]

Has anybody tried hardening and quenching of a blade in the same heat? I read in some old book on blacksmithing that hardening and tempering could be done by first heating the steel to non-magnetic, then quenching only the edge in oil/water. After that the quenched edge is quickly polished so the oxide colours can be seen and heat is allowed to creep from the still quite hot spine into the edge. When the proper temper is achieved the whole blade is quenched and swirled in the quenching medium. I've never tried this, but it sounds a bit quick and dirty to be honest.