Not normal heat treating, no, that would be too easy 
I had to find a steel that doesn’t like to cooperate. 0-1 tool steel cooperates, but after sawing dies made from it for 35 years, I went in search of a steel that’s a little easier to saw, and found 4130 alloy steel. It’s the only through-hardening steel that comes in the right thicknesses for RT/Pancake dies, with the right properties (softer than 0-1, primarily, that I found. It’s not much softer, but it is enough softer to make a difference.
Fine, great so far, until we get to heat treating. See, it’s a water-quench steel, but quenching pancake dies in water cools them too fast. The thermal shock can cause warping and misalignment, both very bad things for pancakes. Quenching 4130 in regular quenching oil doesn’t cool it fast enough to harden it properly. So, that led me to find fast-quench oils- first, an affordable one, then an expensive one that worked better. One big problem is that 4130 can’t be left at heat very long or awful scale forms, that’s hard to get off.
I’m omitting a lot of the experimentation I did over the last two years. Things like using stainless foil tool wrap to cut down on the oxidation and carbon scale, quenching between plates drilled full of holes, to name a couple. The 4130 needs to be heated fast and hot, then cooled fast but not too fast.
One thing I thought of first was a way to mix oil and water, like with a soapy agent. I’m not going to explain why al the things I tried didn’t quite work. I’m sparing us all most of those details. I’m showing a fun video clip of what I did eventually end up with as “the best” way to quench 4130 pancake dies, not that anyone would or should want to go this route. Using 0-1 is much more reliable and consistent as far as heat treating, unless you’re me , and trust me, you don’t want to be me So, what I’m doing in the video is dunking a die into the pricey quenching fluid for about 1.5 seconds, then into water immediately. This cools the die down fast enough to get hard, but slow enough at the start so that flatness and alignment are preserved.
I made this one blast into flames a little extra just for show. Most of them don’t do that, and if they do burst, it’s less severe. The residual oil on the die and in the water get pulled up into the vaporized water cloud and combine with heat and air to create the perfect mix that makes fire.
Quenching RT/Pancake die made of 4130 alloy steel. - YouTube
0-1 is much easier to deal with, heat treating. What I did, though, was saw 0-1 pancake dies for 35 years, and it got to me, mentally and physically. I looked for an easier way (softer steel, even a LITTLE softer, was important) and 4130 is the only through-hardenable steel that comes in the right thicknesses, that IS a little softer (about 20-35% easier to saw…there is a range in both steels). PLUS, it’s a lot less expensive. MINUS It’s messy as an oil spill and tricky to heat treat in the form of pancake dies.