[ATM] "Do it Yourself" 'fine' annealing

[artbianconi@blast.net]

I am going to draw on my limited experience annealing other materials. I 
shouldn't make unwarranted comparisons but I will anyway.

The one I have the most experience with is stress relieving aircraft engine 
mounts, welded up from chromemoly tubing, using various methods (TIG, 
MIG, Stick. Gas)

The chamber is flooded with an inert gas, Nitrogen as I recall, so as to shield 
the steel from any oxygen. Then the temperature is raised to a certain point; 
maintained for a specified period, and then the part is allowed a pre-
determined cool down rate. 

Another method is to bury the part in a pit of granular salt and then "cook" it. 
Same result, stresswise, but the exterior finish is said to suffer.

Specialists who do this on a regular bases have suggested that a longer 
period of time "cooking" at a lower temperature, will produce close to the 
same result as a shorter period at a more elevated temperature, provided 
that the cool down period is maintained.

If this assertion can be applied across the board, then it suggests that 
perhaps we lesser mortals can employ less sophisticated, lower temperature  
ovens than the big guys like Newport use (pizza anyone?) to insure a stress 
free blank. Have any of you considered this?

As for using polarized light to quantify stress: shouldn't both sides of the 
blank be polished to do this?

And, if you are going to invest that much time and effort BEFORE you stress 
test it, are you really going to send it back? If so, please. . . . . send it to me, 
stress and all!

Art Bianconi

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