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Bearing Heat Treat

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Hello everyone...


I have access to these pump bearings. I tried looking into the type of bearing steel it is and whether its case hardened or not. I had bearing material that wouldn't harden before, not even in water. I came to the conclusion that particular bearing may be case hardened. 

I know there's better steels out there, but I like to understand what I have.

The make of this current bearing is from: SKF 7315 EXPLORER.

I cut the race off, the balls are about 1" in diameter. I then cut a piece off the race, hammered to about 1/8" thick. I quenched in water and it broke in half pretty easy. 

I am curious about the grain structure...its very coarse. To those with experience, does it have significance? 

If I wanted to make a blade with the race, would it be usable?

Thanks for any input!

I think I may have found my answer.

The grain structure very much looks like the one pictured in this link:



I'll continue to experiment and have fun!

If there's additional input...feel free.



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  • 2 weeks later...

While I have over the years made many a knife, sword, axe, hammer, and even files in my early days of experimentation.. The only time I have found a grain in metal as distorted or as enlarged as in the pictures from that link was when the metal was over heated or quenched a way to high temperature.. To think this was the grain structure in a knife that was sold is beyond my belief but anything is possible.. 

I've worked with tons of mystery metal and if I need to know the qualities of the metal I do test strips.. ( I will be producing a video on how to identify mystery metals and then use signs to get to a proper or close heat treatment with proper temper).. 

I don't want to do a whole dissertation right now, but ideally forge it to about 1/8 thick and about 3/4" wide x 6 or even 7" long..    Next notch it while hot, say orange heat at 5/8 or 3/4" spacing.

Now take a hardening heat slightly above transition temperature on the end with the temperature going from slightly above transition to slightly below it over the length of the test strip.  Make note of where each temperature was before you put into quench.. 

Throw the whole heated area (orange to no color) thing into what ever media you want to use as your quench of course moving it around..  (there is more to this to figure out if it's air hardening, or oil or water hardening steel)..    Leave in media till it is completely cold to the touch.. 

If done correctly there will be clean spots of metal free of scale where the steel contracted and the scale fell off..  Check the piece from the end that had no color to the orange end for hardness.. Take note of where the hardness start's..  Now over the anvil with the once (pre quench) orange side over the far side,  knock off the first segment..   This will have a huge grain formation.. Continue doing this for each segment till you get to where the snapped off section end grain if very fine (do you remember what color it was before quench)..  Go look at the "Skinner knife video" it has a perfect grain structure where the bar is cut off..   This same grain structure is what you are looking for in the snapped off section.. 

So, you will snap off each section till you get to a point where the last few sections will not snap off but will still be hard.. To hard to file..  This is just about the right temperature for hardening..   If you made note of where the temperature was during quench it will be easy to replicate with that material time and time again for the quench media used..  

The next test is the temper test and this involves a similar process which I won't go into here nor will I cover  A, O or W and helping to figure them out..  Just have to wait for the video. 

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steps.. each segment snapped off.. The really large course grain stuff just usually snaps off first hit..  Snap shot 6 has the correct grain size like pic 8 and is shiny like the picture that shows the cut bar..  picture 7  this segment would not snap off despite 3 hard hits.. it actually dented the face of the hammer.. :) So either 6 or 7 would be about right depending on what the steel was going to be used for..  By the way this is Air hardening steel.. 

Snapshot 3 (4-23-2017 1-10 PM).png

Snapshot 1 (4-23-2017 1-09 PM).png

Snapshot 2 (4-23-2017 1-10 PM).png

Snapshot 4 (4-23-2017 1-10 PM).png

Snapshot 5 (4-23-2017 1-11 PM).png

Snapshot 6 (4-23-2017 1-11 PM).png

Snapshot 7 (4-23-2017 1-13 PM).png

Snapshot 1 (4-23-2017 1-19 PM).png

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