Question about a second Heat Treat

M

Matt Lucas

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May 11, 2020
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13
Hello everyone, I ran into an issue where I want to re-heat treat a blade. I’m wondering if it’s necessary to normalize before a second heat treat. It’s my understanding that normalizing will remove stresses in the steel resulting from shaping and banging on the steel with a hammer (which I won’t be doing before another HT attempt.) It also will reduce enlarged grain, correct? How will re-heat treating a blade without normalizing first affect the grain growth. Does grain growth even occur at heat treating temps? What would you folks do - normalize first or just go for another HT? Thanks in advance for any advice!
 
It depends on the steel and what your first heat treat was. You’re always safe if you normalize and anneal before reheat treating.

Hoss
 
Thanks Hoss.

It’s 1084. I treated two knives last night. The second knife I heated to a little higher temperature than the first. I’m using a mini forge and judging temp by eye. The second knife skated a file just a little better than the first so I wanted to get the first blade a little hotter before quenching. I suppose it’ll be best to just renormalize to be safe. Thanks!
 
Just re-do the HT again. No need to normalize if you are raising the temperature on the second HT.
 
Before you do try filling a bit deep just incase you have decarb and there is hard steel underneath.
 
Im having the same problem i am in the same situation with some 1084 I have to bend my blades in order to get a specific kind of knife im doing for first nations carvers imagine a flat piece of steel and your looking down on it and and it looks like an arrow kinda like 2 drop point knives put together and from above you can see 2 bevels and on the flip side there are no bevels and i need to curl the tip up on a nice radius to it can be used forwards and backwards and a digging knife.. any ways i did the stock removal from clean 1084 from AKS and then brought it probably a to id guess 1600 or 1800 till i could see it glowing orange in daylight and then brought it out and did my bending put it back in and brought it out again to rebend just right did this a few times each time putting it back in when i could see no color in the blade so it was probably id guess 1200 or 1000 and then and then i brought it up again until it was non magnetic and then put it back in for another 30 sec or so with the forge on low so i wouldnt over heat it i had already warmed my 1 litre of oil to 120 deg and pulled it out and quenched it ... it didnt harden..wondering what i did wrong or what i should be doing differently with my bending and HT . But my first time ever HT with 1095 I did get it to harden i didnt bend those knives but i think i overheated it or something because i measured my forge was at 2200 and i stuck the blade till it was glowing orange in daylight and it wasnt magnetic so i held it abit longer and then quenched in heated oil but i think i overheated it because my friend carved with the blade for a day or so and the tip broke and i looked at the inside of the metal and i could see little sparkling diamond like structures spread in and around basically a grey mass of what must be many very fine structures .. i looked under my 100 x microscope and basically saw the same thing but up more close it looked like some big light reflecting chunks all over spread within the grey mass of metal.. SO DID I GROW GRAIN? .. oh by th way i tempered at 450 twice for 2 hours .. and another time i did a quench in water and it hardened really well i snapped a knife trying to stupidly fix the warp after the quench but looking inside that one the grain was all even like one big even grey mass with none of those larger sparkly things .. so i am assuming thats what its supposed to look like after quench???? I dont get the growing grain thing cause if you had to forge a blade up to 2200 or whatever it was wouldnt you be growing grain and then when you brought it up to 1475 or whatever wouldnt it already be wrecked or does the grain only grow when your in the middle of the quench like if you quench from 1500 down to 50 deg vs quenching from 1800 down to 50 degrees wouldnt it techniquely not matter because your just doing the same thing as forging up to 1800 and then cooling a little and then quenching from 1500 arent you i dont understand do you have to be heating first and rising up to 1500 and then quench? doesnt it matter that you just had the blade up to 2200 or so a few minutes earlier wouldnt have that grown the grain already and ruined the HT or when you cool it down to 50 degrees or so does that somehow reset it and allow you to try again? I also am wondering what do i need to do to re heat treat these knives cause they definitely didnt get hard .. I have an infrared laser thermometer that seems pretty much useless and my thermocouple burned up and the second Rhodium S type rated higher temp doesnt read properly on the PId controller that im using to read out the temps so im very very frustrated now and just crashed my skateboard too and my day was an absolute failure.. nothing worked SO should i be normalizing somehow after bending m blades or should i bend at lower temperatures or do i need to let everything cool before starting heat treat? PLEASE HELP ANYONE THANK YOU
 
Storm W said:
Before you do try filling a bit deep just incase you have decarb and there is hard steel underneath.
Click to expand...

I got it down to the bare steel when testing it. I ended up just heating and quenching again and it came out fine. The file won’t bite into the metal anymore but it does leave small scratches on the edge of the blade. All the knives I’ve made have been like this. I assume those little file scratches aren’t an issue as long as the teeth aren’t biting in and cutting off any steel?
 
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