Inducting forging of blades

[weo]

Hello all. I hope all is well with everyone.
Earlier this fall I finally purchased an induction forge, and absolutely love it. It has cut my propane use by ~90%, and as a full-time SOB (sole-occupation blacksmith) this is significant. Over the past few months I've also noticed that: my forge time (and thus most of the shop time on a project) has been cut by ~40-50% depending on the type of forging due to much faster time to yellow heat. I'm a lot more tired by mid-afternoon now, instead of the end of the day because there's a lot less rest between heats.

The main thing I've found that the induction forge does not do well (and I would not recommend trying) is forging damascus or forge welded billets. In my experience, there's too much of a temp gradient at the heat transition to avoid stressing/cracking the welds. Anyone else have input?

I'm also wondering if this very short heat transition would be detrimental in mono-steels or would this corrected by proper thermal cycling? I'd think there's still a significant concern about the short heat transition, and wouldn't try an air-hardening steel for sure. Mainly just wondering if I should warn the bladesmiths who use our forge not to use the induction forge.
Thanks

 

[Ken H>]

Glad to hear your experience with induction forging. I've read about and looked at those things and wondered how well they would work. I would expect for forging mono steel proper thermal cycling should take care of the problem, BUT - I'll be watching this thread to see other comments - maybe from Larrin or Hoss.

 

[billf]

I know both Dave Lisch and Mike Quesenberry use them...I'll bet they can steer you right

Bill

 

[tattooedfreak]

UK knives on You tube did a couple videos on induction forging and Black bear forge did one as well I think.

 

[N.W. Gean]

Just out of curiosity, how's your electricity use? I'd imagine it doesn't stack up to propane, but still worth knowing.

 

[weo]

Just out of curiosity, how's your electricity use? I'd imagine it doesn't stack up to propane, but still worth knowing.

Unfortunately, I have no real way to track that. I run a metal shop in a 26000 sf makerspace with one power bill....

 

[Cushing H.]

I’m not a blacksmith … but I wonder if the higher oxygen atmosphere in the induction forge presents a problem with more material loss due to oxidation of the surface?

 

[weo]

I’m not a blacksmith … but I wonder if the higher oxygen atmosphere in the induction forge presents a problem with more material loss due to oxidation of the surface?

I've been kinda paying attention to this, and I'm not sure there's more (oxygen or scale formation). I'm leaning towards there being overall less scale formation, but I think the reason is most likely less overall time at oxidizing/scale producing heats.

 

[Joshua Fisher]

The heat transition can be helped some by passing the blade through the coils so a larger area get some heat then focus the heat in the spot you want. Having used a propane forge, coal forge, and induction forge I’d say the induction forge works very similarly to a coal forge which has been around for quite a while and is very common for people to isolate heat for forging a tang or specific spot so as long as you aren’t hitting and stressing the cold area I don’t think it’s a concern.

 

[Natlek]

The heat transition can be helped some by passing the blade through the coils so a larger area get some heat then focus the heat in the spot you want. Having used a propane forge, coal forge, and induction forge I’d say the induction forge works very similarly to a coal forge which has been around for quite a while and is very common for people to isolate heat for forging a tang or specific spot so as long as you aren’t hitting and stressing the cold area I don’t think it’s a concern.

The induction forge heats the steel from the inside

 

[jviccc]

I currently use a 15kw unit for profiling - I have a 10cm taco shell coil with a ~25mm gap to heat up bar stock I forged down to thickness in the gas forge. Getting to forge-welding heat is possible but tricky without the proper sized coil for the size of material being worked on. It's kind of a hassle for me to swap coils I've found(I have to keep replacing the teflon or it leaks after every swap) plus it gets a bit messy when I throw flux in the mix - I've stuck to forge-welding my damascus billets in the forge. About the heat-gradients - the skin of the material heats up first. If you use the foot pedal, you can heat up the surface for a few seconds, release to allow for heat conduction to the core and repeat. Also I try to avoid the habit of forging cold when it's so quick and easy to reheat the segment. I'm trying to save up for a heat treating furnace but I haven't had too many any issues cycling and austenitizing smaller blades with the coil by eye. As for oxidation, ever since I started forging to shape with induction, I've had less to worry about in regards to scale.

To summarize, it's great for blade profiling, especially when I'm trying to forge as close to shape and not waste propane but I'd stick to the gas forge for welding damascus and ideally a kiln for heat treating.

 

[weo]

The induction forge heats the steel from the inside

Depending on what you're meaning, this isn't exactly true...
Where the maximum heating takes place is all related to the size/shape of the piece and the shape/design of the coil. The closer to the coil, the quicker it heats up.

 

[JoeBusic]

Depending on what you're meaning, this isn't exactly true...

But it is. Literally. Even when the heat layer is thin, that layer is the heating source. When the heat layers overlap in the middle, that overlap heats more, thus creating more heat in the middle. Thru heating with a solenoid coil can melt the inside while the outside is still under thyxo temps. Happened to me. It's a bitch.

 

[weo]

But it is. Literally. Even when the heat layer is thin, that layer is the heating source. When the heat layers overlap in the middle, that overlap heats more, thus creating more heat in the middle. Thru heating with a solenoid coil can melt the inside while the outside is still under thyxo temps. Happened to me. It's a bitch.

But when you put a square rod in a round coil, the corners heat up first.
Where the steel heats depends entirely on the shapes of the coil and the stock.
The shape/size of the coil determines the shape and size of the magnetic field which determines where the electrons get 'excited' which is where the heating will take place. Not necessarily the center of the piece.

 

[JoeBusic]

But when you put a square rod in a round coil, the corners heat up first.
Where the steel heats depends entirely on the shapes of the coil and the stock.
The shape/size of the coil determines the shape and size of the magnetic field which determines where the electrons get 'excited' which is where the heating will take place. Not necessarily the center of the piece.

"Even when the heat layer is thin, that layer is the heating source." As said. And when that layer heats to red, next layer heats up until it gets to the center. So, literally it heats from within. Problem with induction is one can't rely on the color when heating. Practice is needed to understand the heating pattern.

 

[JoeBusic]

I have to keep replacing the teflon or it leaks after every swap

Anneal the flares and when tightened it will form easily without leaking. No teflon needed.

 

[weo]

But it is. Literally.

I understand what you are saying, Joe. I was merely clarifying Natlek's post for folks reading this thread in the future who have no knowledge of these machines:

The induction forge heats the steel from the inside

and in my experience, when explaining this to people, they tend to assume the above statement means it heats from the center outwards, and this isn't necessarily true. If the center of the piece isn't in the induction field due to poorly matched coil and work, the center of the piece doesn't heat up first.
But yes, the heat does not travel from the surface to the interior like in traditional forges.

 

[Palmetto1155]

Hello all. I hope all is well with everyone.
Earlier this fall I finally purchased an induction forge, and absolutely love it. It has cut my propane use by ~90%, and as a full-time SOB (sole-occupation blacksmith) this is significant. Over the past few months I've also noticed that: my forge time (and thus most of the shop time on a project) has been cut by ~40-50% depending on the type of forging due to much faster time to yellow heat. I'm a lot more tired by mid-afternoon now, instead of the end of the day because there's a lot less rest between heats.

The main thing I've found that the induction forge does not do well (and I would not recommend trying) is forging damascus or forge welded billets. In my experience, there's too much of a temp gradient at the heat transition to avoid stressing/cracking the welds. Anyone else have input?

I'm also wondering if this very short heat transition would be detrimental in mono-steels or would this corrected by proper thermal cycling? I'd think there's still a significant concern about the short heat transition, and wouldn't try an air-hardening steel for sure. Mainly just wondering if I should warn the bladesmiths who use our forge not to use the induction forge.
Thanks

Just curious,

Hello all. I hope all is well with everyone.
Earlier this fall I finally purchased an induction forge, and absolutely love it. It has cut my propane use by ~90%, and as a full-time SOB (sole-occupation blacksmith) this is significant. Over the past few months I've also noticed that: my forge time (and thus most of the shop time on a project) has been cut by ~40-50% depending on the type of forging due to much faster time to yellow heat. I'm a lot more tired by mid-afternoon now, instead of the end of the day because there's a lot less rest between heats.

The main thing I've found that the induction forge does not do well (and I would not recommend trying) is forging damascus or forge welded billets. In my experience, there's too much of a temp gradient at the heat transition to avoid stressing/cracking the welds. Anyone else have input?

I'm also wondering if this very short heat transition would be detrimental in mono-steels or would this corrected by proper thermal cycling? I'd think there's still a significant concern about the short heat transition, and wouldn't try an air-hardening steel for sure. Mainly just wondering if I should warn the bladesmiths who use our forge not to use the induction forge.
Thanks

Wonder if the induction forge would work better at altitude than LPG. I just moved to 8500+ elevation and haven't set my forge up yet. From what I've read so far, there's a significant loss of heat at this altitude with propane.

 

[JoeBusic]

Just curious,

Wonder if the induction forge would work better at altitude than LPG. I just moved to 8500+ elevation and haven't set my forge up yet. From what I've read so far, there's a significant loss of heat at this altitude with propane.

Electricity will work the same. The issue is the machine. Is it rated for that elevation. Air is thinner, thus more conductive and current can jump across the board and burn things. Always check with the manufacturer about the elevation limits. Sometimes pouring resin over the boards help..

 

[Palmetto1155]

Electricity will work the same. The issue is the machine. Is it rated for that elevation. Air is thinner, thus more conductive and current can jump across the board and burn things. Always check with the manufacturer about the elevation limits. Sometimes pouring resin over the boards help..

Great considerations, thanks