How do I get a stainless pin out of an aluminum masthead?

[Reefmagnet]

Originally Posted by BBill

Ironic is you questioned exh gas temps being hotter.

Its already been posted...you are likely ruining the temper. Al yield strength reduction in fires...as high as 50% reduction at 150c. What is the yield strength on 6061 after being exposed to your heating method at 500c-550c? How hot did the masthead get? I'll answer that for you...you have no clue.

Actually, as a former student of metallurgy, I do have a clue.


Solid state grain reformation is an annealing process that requires temperature + TIME. That latter point is important, because time is measured in hours when annealing, not minutes. Ever noticed the welding on your mast, btw? There's a reason that the HAZ is confined to a very small region adjacent to the toes of the weld. Can you guess why?


Now you're a little more informed, it should be apparent why I also mentioned the use of Mapp gas or better (as in acetylene). You guessed it; it makes sure the aluminium component doesn't get to soak at elevated temps for too long.

[BBill]

Originally Posted by Reefmagnet

Actually, as a former student of metallurgy, I do have a clue.


Solid state grain reformation is an annealing process that requires temperature + TIME. That latter point is important, because time is measured in hours when annealing, not minutes. Ever noticed the welding on your mast, btw? There's a reason that the HAZ is confined to a very small region adjacent to the toes of the weld. Can you guess why?


Now you're a little more informed, it should be apparent why I also mentioned the use of Mapp gas or better (as in acetylene). You guessed it; it makes sure the aluminium component doesn't get to soak at elevated temps for too long.

It's thermodynamics and you're not teqching me anything other than I should have stopped replying when you erroneously questioned combustion and exhaust temps related to pistons.

Yep, don't let it soak at elevated temps. Unfortunately Al doesn't give much notice before it turns to liquid. That's the point I've been making the whole time. Heating ss to glowing red is a fast way to puddle Al from surrounding overflow heat. Any 1000w heat gun on low will do the job at safer temps through heat/cool cycles. I typically use a small butane torch on bolt heads where a heat gun can't be used and never let it get hot enough to glow. Years ago I puddled an outboard lower unit while heating a ss bolt head...the ss never started to glow but the Al around it flashed into a liquid. A low temp torch will do the same thing.

I'm done.

[skenn_ie]

Originally Posted by Manateeman

Heat...lots of heat on the stainless.
Mark

I would heat/expand the ally and use freezer spray on the stainless. More effective if there is a hole in the pin to spray into.

[Reefmagnet]

Originally Posted by BBill

It's thermodynamics and you're not teqching me anything other than I should have stopped replying when you erroneously questioned combustion and exhaust temps related to pistons.



Yep, don't let it soak at elevated temps. Unfortunately Al doesn't give much notice before it turns to liquid. That's the point I've been making the whole time. Heating ss to glowing red is a fast way to puddle Al from surrounding overflow heat. Any 1000w heat gun on low will do the job at safer temps through heat/cool cycles. I typically use a small butane torch on bolt heads where a heat gun can't be used and never let it get hot enough to glow. Years ago I puddled an outboard lower unit while heating a ss bolt head...the ss never started to glow but the Al around it flashed into a liquid. A low temp torch will do the same thing.



I'm done.

You should be done. I had already noted previously aluminium is hot short. Which is irrelevant because it will not melt using the technique I mentioned if done correctly. Correctly as in heating the pin and not the alloy directly.