Rockwell stuff

[Jack Davenport]

Will parts that have been just removed from the oven Rockwell test softer at that time and harder 40 mins later?

 

[GibsonFan]

Do you mean before and after quench? What kind of steel?

 

[scottickes]

I think he means just after temper and then 40 minutes after temper.

 

[Bruce Bump]

Thats a good question. I do know that right out of the quench the steel is still soft enough to bend but if you try to bend it 5-10 min. later it will snap like a twig. Thats why the dreaded "ping" happens later sometimes.

 

[Nathan the Machinist]

Will parts that have been just removed from the oven Rockwell test softer at that time and harder 40 mins later?

Yes.
Some steels take time to fully harden after quench, though I have no idea what those times are for different steels.

Austenite converts to martensite while at room temperature over time. Some complex steels would take years to fully convert without cryogenic treatment. Those steels do convert at high tempers, but the lower tempers we use doesn't always do it.

When it does convert during temper, you need another temper for the freshly formed martensite. Hence the need for multiple tempers.


And aluminum and titanium are really weird.

 

[Jack Davenport]

Thanks Nathan: Since I posted that thread I went to Fillmons Bayou and netted three big gulf mullett and admitted that the thermocouple in my heat treater is most likely off enough that my parts in this batch arent right, after all they will hardly cling to the fine pole chuck in my surface grinder, this tells me that they probably were to hot when I quenched them. Jack Davenport.

 

[Arthur Washburn]

after all they will hardly cling to the fine pole chuck in my surface grinder, this tells me that they probably were to hot when I quenched them. Jack Davenport.

This is only true for carbon steel.

Most hardenable stainless becomes less magnetic the harder it becomes.

 

[rlinger]

Unless you're doing sample testings I would suggest not taking the time to Rockwell a blade before temper. Also, it is very dangerous to put such pressure on hardened untempered high carbon steel. A high alloy might be more forgiving but high carbon steel in such a state and under such pressure can shatter in your face and with great force. Moving on; your blade is best placed in temper before falling below 'hand warm'. Good question though and my guess would be softer before than later.

rlinger
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