Induction forge edge only ht

[Ben Potter]

I'm interested in trying out a new HT method.

Using an induction forge to heat only the edge then water or oil quench.

A clay coating could be used to help avoid vapor jacket and control the "hamon" and avoid over oxidation/decarb.

My question is what steel would be best?

I normally use NJSB 1075, 1084, and 1095(my favorite).

My initial thought was to go with 1084 because it is eutectic and shouldn't need as much of a soak time.

I've also been thinking of trying W2.

Any thoughts?

 

 

[Joël Mercier]

Just how can you heat only the edge with an induction forge? That is a genuine question. 

[dragoncutlery]

58 minutes ago, Joël Mercier said:

Just how can you heat only the edge with an induction forge? That is a genuine question. 

You make a coil that only goes along the cutting edge ive seen it somewhere maybe youtube 

[Joël Mercier]

That would imply forming a new coil for every blade, including some with a very long oval shape. 

 

It is also probably going to be tricky to keep the edge well centered. 

 

I've only worked with portable induction heaters so far, so my experience is limited...

 

Anyways, going for eutectoid steel is a good idea. Just keep in mind some steels will need a normalisation if done by stock removal, to dissolve carbides. A quick heating to critical might not be enough...

Edited April 6, 2022 by Joël Mercier

[Ben Potter]

Here ya go:

Induction forge HT

 

Another one of the whole process(and yes you are not supposed to touch the coil with metal...)

Induction forge quench

 

 

edge hardening UHF induction set up

 

 

Edited April 6, 2022 by Ben Potter
Adding links

[Christopher Price]

No offense, but I don't understand why selective heating is preferred over selective quenching.

[Ben Potter]

If you are using water cooled grinders for stock removal the back of the blade would be annealed (or what ever temper it comes with) and the edge would be hard.

Or in the case of spring tempered saw blank material the edge/teeth could be hardened and the back left at spring temper.

 

No real advantage in most cases just an idea I've had for years and would like to try out.

[Jerrod Miller]

1 hour ago, Christopher Price said:

No offense, but I don't understand why selective heating is preferred over selective quenching.

 

With induction especially it is extremely easy to control the section heating, way easier than controlling the cooling rates.  On top of that since you have a cold spine you end up with a lot more strength in the blade, so you are much less likely to warp during quench.  You will also leave your spine microstructure alone, so you can thermally treat that to whatever you want (larger or smaller grains) then only change the edge.  You also don't need to worry about clays or anything else to help control the slow section in the quench.  On a production level, there is also less energy used (little waste), and the cooling becomes simpler (again, due to needing less).  

[Christopher Price]

I hear what you guys are saying, but there's an inevitable heat-affected zone between your over-AC1 temp and your tempering target... so yes, a pre-tempered spine, and a hard edge, with over-tempered-but-unhardened material in-between.

If you figure it out, I'd love to see the results. I've had an induction forge on my list for a long time. Maybe one of these days I'll get around to actually getting one. I can think of a ton of things I'd love to do with it.

[Jerrod Miller]

2 hours ago, Christopher Price said:

but there's an inevitable heat-affected zone between your over-AC1 temp and your tempering target... so yes, a pre-tempered spine, and a hard edge, with over-tempered-but-unhardened material in-between.

 

I'm not following you here.  You have a completely unhardened spine, so pearlite with either ferrite or carbide patches depending on alloy.  So you then get a hardened edge and an "over-tempered" pearlite/ferrite/carbide spine; which means nothing, really.  So there isn't a heat affected zone worth noting at all.  

[Gary LT]

Induction forges are expensive and although I’d like one as an option, it will probably never happen. But I like this concept.

One question is ………when heating specific steels to recommended temps prior to quenching, how do you know you’ve hit that short range of ideal temperature ? Can the induction tool be programmed for an exact temperature ceiling? Or?

Gary LT

 

[Joël Mercier]

30 minutes ago, Gary LT said:

how do you know you’ve hit that short range of ideal temperature ?

My thought as well. 

 

It's an awful lot of money to be using decalescence. At this rate, an HT oven seems to have only advantages vs the induction forge, for heat treatment that is...

[Ben Potter]

The forges can be programmed for temps and hold times etc.

[Jerrod Miller]

14 hours ago, Ben Potter said:

The forges can be programmed for temps and hold times etc.

I have never seen one that can be programmed for temperature.  They can generally be programmed for energy output, frequency (sometimes), and hold times, but the temperature is going to depend on geometry of the part, frequency of the unit, geometry of the coil, placement of the part in the coil, and a few other things much further down the list.  You will need a separate means of temperature monitoring.  At least, for all the ones I have seen.  

[Ben Potter]

My friend has one with an inferred sensor built in and one (that died) with programmable times/temps. Pretty nice cause you can prevent over heating...IF you take the time to set it