There is one point that puzzles me about the information you have received, I do not understand the concept of induction heating not exceeding "critical". Induction heat is incredibly fast and intense and is only limited by the rate of steel feed into the field and the amount of the cycled energy going in, there should be no limit to the heat, and I personally have burned 1/2" stock in half by holding it stationary in the field. With that being said there is one advantage and one huge disadvantage in using induction for refining heats, first it heats incredibly fast which is good for grain refinement, but secondly it offers Little in the way of determining what heat you have heated to and holding in a controlled manner at that heat. If one could devise a way to determine the exact temperature reached and arrange a cooling tank directly below the coils then a feed rate could be devised to quickly cycle up before cooling, this could then be stepped down for what you are looking for. This would all be good for austenite grain, but carbide refinement is equally, if not more, important and it needs time at temp which is a different approach. Induction is really cool stuff but some folks get the idea that its heat is different or that its heat produces different results, when in fact heat is heat and the steel doesn't know or care what makes the heat it only responds to the amount and rate of heating.

As usual, a great reply Kevin. After continually reading I found out as you said, it will definitely heat over non magnetic and will even melt the metal. So is there a place for induction heating in bladesmithing? Other than something fun to play with, I can only see possible applications in differential heat treating. Am I right or am I missing something?

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As usual, a great reply Kevin. After continually reading I found out as you said, it will definitely heat over non magnetic and will even melt the metal. So is there a place for induction heating in bladesmithing? Other than something fun to play with, I can only see possible applications in differential heat treating. Am I right or am I missing something?

I think it would be cool for forging and for making custom steel melts (if one invested the money for the unit big enough). For heat treating, I am sure it would be acceptable for many who like doing it by eye, many folks also use torches and coal forges. For me personally it would never satisfy my control freak side not knowing the exact temperature for a specific hold time.

I think Kevin wrapped this question up very well but I feel obligated to throw in a little more info. I'm a young metallurgist in the Induction heat-treating field so this topic is right up my alley.

Advantages: As stated, quick heating and quenching will usually create a very fine grain Martensite which is generally beneficial. Differential heating would be fairly easy too. You could even create a hamon with the right set-up. Repeatability with these machines are excellent. If you need to heat treat 1000 of the same blade, induction would be a good option. You can also temper using induction (although I would probably never recommend it for a knife blade).

Disadvantages: Cost. One of our cheapest machines runs in the neighborhood of $200,000 new and they can quickly get up into the millions of dollars. Smaller scale shop set-ups are out there but without the machine controls an even heat-treat would be difficult. Another problem to consider is warping. Small pieces like a pocket knife would be safe, but larger pieces like a bowie or a sword blade could really run into problems. I've seen a 2' piece of 1/4" flat stock get a 2" bow in it from uneven heating.

Overall, I would not suggest induction for small-scale heat-treating operations. A propane forge should suffice for 99% of smiths and if decarb becomes a problem possibly moving onto a small salt-bath.

Great info guys and thanks. I would like to play with one but I'm gonna stick to my forge and heat treat oven.