Hello:
Ive been woirking on a batch of neck knives that will be heat powder coated.

In the powder coat process, they must bake at 350 - 400 deg for 35 min.
was told they could do 300 deg but a longer hold time (one hour)

Here is my question

I am planning on doing my standard HT which is 3 normalization / 1 anneal / bring whole blade to critical, then edge quenching. But thinking I may not temper before I take them to powder coat. Thinking that once they are done, I can sharpen them and check the edge on the brass rod to see where they are as Im not too sure they are spot on with their temps!

1.) Am I setting my self up for problems taking them blades that are hardened and not tempered? Even if they are careful, should I be worried about breakadge from stress?

2.) If I did a mild temper, say 280 deg or so, would this help to reduce some of the brittleness? I have been tempering at 325 deg by my thermometer and oven and getting just what I want, 340, and the tips bend.

3.) Can you over temper a blade?? If I tempered to 325 in my oven once they have been powder coated, and if they did not go over 300 deg, will I still be at the same point as if I just tempered once at 325??

Dont mean to sound like a mother hen on these, but Im doing them in batches and dont want to ruin 10 at a try!

Thanks in advance!!

God Bless
Mike

Mike..dont take anything I say as an expert advice...cos I am not. But I have done something similar myself.

I sprayed and baked on my own coatings (Brownells)........on 1095, but it was a while ago.

I went thru my usual ht procedure, but when it came to tempering, I usualy temper x 3..but in this case I did x 2, and used the bake as the third (temperature was the same or just under my usual temps).

I dont think I would want to ship fully hardened non tempered 1095 ..they may be brittle and I dont know how it would be handled....... ..I think I would at least give it one temper to relieve any stress in those circumstances.

[QUOTE=Dont mean to sound like a mother hen on these, but Im doing them in batches and dont want to ruin 10 at a try![/QUOTE]

Tough call. :confused:

Your concern on having at least some kind of temper as soon as you can after the quench is valid. Take it to 375F or so for around 45 minutes to an hour and then proceed. I just finished a series of tempering tests that included 1095 if it is any help here are my number (averages from many readings):

1095
as quenched 65
375F. 62
400F. 61
425F. 61

One thing that I have come to not trust in the books is tempering temp versus HRC (Sorry Quenchcrack;)). I am getting close to the spec sheets with the salts but ovens tempering has always been very different. I chalk this up to the amount of time required in open air ovens and termperature variations. Time is still a factor in diffussional processes but with tempering things move so slow that time almost becomes a non issue after the initial effects of temperature do their thing. One hour at a temperature equal to or below my initial tempering temperature wouldn't worry me much at all.

I think your greater concern could be for the powder coat. Could reheating that stuff, if your HRC isn't where you want be a problem? It may be safer to do your temper, nail your desired HRC and then have the coating done.

Do all your normal HT, then powder coat . Long times at tempering temperatures are not a problem [ like when you forget the blade over night! ]

Kevin! I'm Shocked! :eek:

Well, I have to agree on the issue when heating blades. I wonder if the very rapid heating of a thin blade in a hot forge has the same superhardening effect that induction heating does? We can get 2-3Rc points harder out of the induction line than I can get out of an electric furnace with a medium carbon-manganese steel. If superhardening is indeed possible with ANY rapid heating, it would throw the tempering curves off, too. :confused: