Another heat treat question ? 10xx steels quenching at higher temps

[duffy99]

Hi, I've been reading all of Kevin's post's and there are a few simple questions that I hope someone, Stacy maybe, could answer in layman's terms. If you over shoot your target heat what are the effects beyond longer grains? I'm still waiting on my PID and therocoupler and did 2 1084 knives yesterday in Houghton K quench. I roughly normalized 2 times before the quench . I used 8 liters of quenchant in a deep rectangular quench tank . I preheated the quenchant with bar stock prior to quenching the 2 blades . I had flare up's on both which in itself doesn't really mean much to me . The second blade I could really feel the bubbling around the blade for the first 10 -20 seconds while agitating back and forth . I'm pretty sure I quenched over the optimal heat now what does the mean for the steel? I also drew the spine soft by immersing in water and heating the exposed area with a torch to soften it after triple 1 hour tempers . But the real question is about the effect of quenching above the optimal heat in simplest forms . I thought I understood the different phases it goes through , but now my heads spinning after reading all that stuff. I understand that the hotter an object or anything the faster the molecules will be moving and the quench is to freeze them in place rapidly now where does the higher temp come into play.

 

[Karl B. Andersen]

How much above "optimal" heat?
How long was it held at that temp?
You can certainly over-shoot your target temp SOME, with little to no ill effects.
As well, if not held at those temps for long, you are in no danger.
But just don't go WAAAAAAAAAAY hot and/or stay there for long.
Besides just heating to critical temp for that given steel and utilizing sufficient quenchant of proper speed, I've certainly proven - at least to myself and my customers - that the attention you pay to what you do to the steel BEFORE you go to harden, is 50% is the game.
Maybe more than 50%.
Getting a little hot at hardening is nearly even mentionable.

All that said, to read that you heard/felt your steel bubble around the steel for 10-20 seconds does bother me some. That's pretty hot.

 

[duffy99]

How much above "optimal" heat?
How long was it held at that temp?
You can certainly over-shoot your target temp SOME, with little to no ill effects.
As well, if not held at those temps for long, you are in no danger.
But just don't go WAAAAAAAAAAY hot and/or stay there for long.
Besides just heating to critical temp for that given steel and utilizing sufficient quenchant of proper speed, I've certainly proven - at least to myself and my customers - that the attention you pay to what you do to the steel BEFORE you go to harden, is 50% is the game.
Maybe more than 50%.
Getting a little hot at hardening is nearly even mentionable.

All that said, to read that you heard/felt your steel bubble around the steel for 10-20 seconds does bother me some. That's pretty hot.

I'm not sure if it was quite that long but on the initial quench it did flare up and bubble , it was the second blade so I believe the quench oil may way been hotter then the first blade which may have been a factor. I did a rough one , two count then edge 1/2 second then the whole blade. It's tempered know so I'll do the file and brass rod test which is the only ones I know of that I can do at home . I don't want to deflection test it just because of the above. I should use a thermometer in my quench tank ( big roast pan ) and once I have the PID and thermocouple I will know the heat . I have a 2 soft brick forge with a hairdryer blower. I have a good regulator and was only using a trickle of propane , the lowest I could go and keep it burning. I did notice that I can reignite just from forge heat and played around giving little flame bursts no doubt impressing my neighbors after angle grinding a metal tank and some other stuff for an hour .

 

[duffy99]

Will martensite still form if the blade was 1700f instead of 1450f? Or will I have more pearlite formed? Besides brass bar deflection and file test what are other home methods of knowing if the heat treat took? Are there indicators on the blade like deep pockets ? Should a properly hardened blade not have any pockets or texture and just have small pieces of outer scale that easily flakes off?