Jerrod Miller

As long as things stay civil, all is fair.

C45 is 1045 and C60 is 1060; and that relates to the carbon content (0.45% and 0.60% respectively). Generally speaking, C60 would be the lowest considered to be knife worthy in terms of hardenability. You have to control your temps fairly well, and may want to try a water quench. 1070 definitely bumps you up a significant amount, as far as hardenability goes. Sorry, can't help you on European steel sources, but there are a few Europeans on the forum, so hopefully one of them can chime in.

Your best bet is probably just going to be normalizing. Heat it up past the austenite conversion (watch for decaslescence), then let it cool to black in still air. While you are at it you might as well do it 3 times. Should only take a few minutes per cycle (heating and cooling). Oh, and the forge would be best for that, but may be good to go with the propane torch. You don't need to do the whole thing all at once.

Basically what they said, except that the Ms is when martensite starts forming upon cooling, which is usually around 400 F. Not going to do much good to quench from there. What Joshua meant was the austenitizing temp. But you knew that already. I'd also add that one may want to do a normalization cycle after mechanical stock removal (grinding or machining) if heavy work is done. Meaning really big /aggressive cuts, not just lots of material removed. If you use a file and remove half your starting stock, that is pretty gently and shouldn't need another cycle. But if you were to mill your bevels in one pass, that aggressive machining may have caused stresses in the metal. I would think this need is not very common, but if anyone is experiencing problems this may explain it a little.

You could do that with the forge you have, just build up the walls with brick on that. Also, if you think propane is scary, liquid aluminum probably isn't for you. That stuff sticks to you.

Those actually are lead, so there's that. <insert general lead warnings here> That said, I use that to cast bullets. That is mainly because it is fun, not because it is cost effective.

Can we renumber these so Alan's points come before mine? Also, foundry101.com is a good source of info, if a bad (awkward) website.

First, smelting is converting ore to metal. You're just looking at remelting. Second, I would recommend you try it with your forge fist, since you have it already. From there you can see what you like and don't like about it. Third, make sure you follow the instructions for your crucible pre-heating so you don't crack it.

I did speak to our machinist today. He said 17-4PH isn't too bad if you you get the right feed and speed. Keep the chip load fairly light or you get work hardening effects.

Normalize a couple times, then go for the sub-critical anneal. Heat to 1300 F or so. Do not go through the phase change. It is a very aggressive temper, which leaves a normalized piece pretty soft.

I really shouldn't have used the term "hardened". Solution treated is the right wording. It was still a little early for me after a long weekend. I'll talk to our machinist tomorrow to get his thoughts on machining it, but we have no problems machining it that I am aware of. You're looking at having ferrite stringers in a martensite matrix. Better than having austenite, which gums things up!

That is only if it is already hardened. Hardening 17-4PH is a solution treatment at 1025-1050 C (1875-1920 F) then oil quenched. After that you age at about 480 C (900 F) to get a hardness in the low 40s HRC.

Are you using a muffle pipe?

I just want to really clarify that as long as you aren't cracking the metal, and you are going to HT later, the HAZ isn't something to worry about. Unless you are doing stock removal, then you may run into hard spots that a normalization cycle will fix.

If you are doing things by eye (rather than thermocouple), I'd highly recommend spending whatever time it takes to get good at seeing decalescence and recalescence. A similar chart to that is on the cover of my copy of the ASM Heat Treater's Guide, and I really wish those charts would go away. Your magnets are better off melted than being used for HT control. Control your ambient light in order to HT by eye. 1500 degree steel looks very different at high noon (on a sunny day), dusk, and pitch black night.