Problem with 52100 or just me!

[tippit]

I have a problem with some 52100 steel that I forged today.  I had forged it by packing the edge plus thinning and stretching the piece, like I always do.  Then I rough ground to it to my desired blade shape.  While grinding to shape I kept noticing fissures across the ground edge.  So the blade kept getting smaller & smaller...thinking I had a bad spot.  Finally I polished out the flat surface to 120 and it looks like a piece of ice crystallizing.  I don't think I worked it too hot...not sure what happened as I've never had this occur with 5160 or 1080.  This is the first time I've used 52100.  If you look at the picture closely you can see the thin cracking on the surface.  Where did I mess up        tippit

 

[vermonster13]

I sent you a PM Doc.

[tippit]

I decided to do a flat grind on the blade to see how deep the alligator fissures were.  They ground out except on the very top edge of the spine.  I also noticed that the steel ground with brighter bursts of sparks, seemly harder steel with everything the same as when I do 5160 & 1080.  For the first time I actually ground all my forge marks out to get a better look at the steel surface.  Anyone else care to enlighten me with your experience with 52100...Doc

 

[sticshooter]

Doc you amaze me.<><

[Lin Rhea]

Tippit,
          I have an email out to a friend who is an expert on 52100. Let's see what he says first. Lin

[tippit]

Lin, Thanks for looking into it for me!

[Lin Rhea]

Tippit,
         52100 is not for the faint of heart. That's why I wanted to holler at Ray Kirk MS. He uses 52100 almost exclusively and is one of the best athorities on it's use for blades. I sent you a copy of his email.
  For those of you who would be interested, he said that 52100 has to be worked hot and within a range of heat. If you work it too cold it will crack like that. Lots of steels will crack when worked too cold, but especially is 52100 prone to. Also, typically edge packing is done as the heat is reducing, which entering the danger zone, temperature wise, so he recommends NOT edge packing this steel.
  If you get it too hot while forging, it could splatter while being hit. White hot is too hot. I figure orange to bright orange is a good color to forge it. Red to bright red is a good forging temp for most steels, but probably too cold for 52100.
     Every steel has it's peculiarities and part of the fun is figuring it out.
                                 Lin

[tippit]

Lin,  That certainly explains it.  Thanks for all your help...tippit

[tippit]

Lin, I read Ray's reply on 52100.  I guess ignorance ain't bliss!  tippit

[4runr]

This is just too cool. Within about 4 hrs, Doc, you got answers to questions you would probably have spent days diggin for.

[tippit]

The sharing seems to flow like a river from the top to the bottom.  Very nice feeling here...Doc

[tippit]

Well the 52100 didn't blow apart when I quenched & tempered it.  I did grind the blade to 240 before quenching and didn't see any cracks.  This stuff is really amazing!  When I normalized it (heating thru non magnetic and air cooling) the forging scale literally popped off the the blade like fleas  :eek:   Scale will usually flake some what as it cools but this stuff was jumping.

So when I quenched it I had my usual gloves and eye protection not knowing what to expect.  That seemed to go pretty smooth.  I edge quenched and pulled it out when the color went dark.  Then let it air cool as apposed to putting it down in the oil.  This was Ray Kirk's & Lin Rhea's recommendation.  It will be interesting to see what this edge is like compared to my usual steel...5160 & 1080.  52100 is ball bearing high carbon steel...very tough stuff.  Many thanks to Lin for getting me thru this    Doc

 

[Lin Rhea]

Tippit,
         Did you try it with a file? Lin

[tippit]

Lin,  I tempered for just a little over an hour at 440 F but my oven is 15-20degrees higher with themacouple...so 455-460F.  The blade came out purple/violet.  The File cuts into edge.  Not sure if too soft.  I'll grind an edge & take pictures in am...Doc

[Lewis Brookshire III]

Man thats a SWEET knife, cant wait to see what it looks like when you are all done!!

[tippit]

Lin,  Are you getting any work done with all the time you're spendin'....looking over my shoulder and helpin' me out?

I would have sworn that the blade would be too soft...purple color & file will cut.  So I couldn't wait til morning...after all my wife is in SC for 3 months, so what's an old man supposed to do on a Friday night  :rolleyes:  Yep back to the shop.  I ground an edge and the tried to sharpen with my never fail Gatco system.  Still too hard    It's going back into the oven @ 455 = 470.  I'll try again.  

In this picture, the blade has a pattern of it's own...circular swirls not my grinding pattern.  This stuff is challenging, frustrating, and lots of fun!  Doc

 

 

[Lin Rhea]

Tippit,
         I'm learning too. After you tried the Gatco, did you try the file again? I'm thinking there was a layer of decarborized steel on the surface. This can be typical and quite normal. This layer is softer due to the loss of carbon. Once you file through it the blade is really hardened. In this case still too hard.
     The picture looks like you have a start on the bevel anyway.
                                      Lin

[tippit]

Lin,
I used the the file before I ground my edge on my KMG.  The bevel is right there but the Gatco couldn't put an edge on it.  If I had color like this on 5160, I could probably put an edge on it with soap stone     I usually temper 5160 at 375 for blades and 400-420 for forged broad head so they are easy to file sharpen.  I'm now getting close to 500 mark on this one.  

I'm sure glad Ray gave some guide lines on tempering 52100.  In my limited experience, this just blows me away!  She's baking now...tippit

[tippit]

The specs on it say to temper up to 500 F.  This is one hard Momma!

52100 Spec Sheet for anyone interested:

AISI 52100
Alloy Steel
   
     Typical Chemistry
Carbon 1.00%
Manganese  0.35%
Silicon  0.25%
Chromium 1.50%
 Typical Applications
 Bearings Gauges
 Draw Dies Mandrels
 Drills (Non-Ferrous) Taps (Hand)
 Forming Tools Threading Dies (Hand)
 
   
--------------------------------------------------------------------------------
 
   Annealed Hardness: BHN 183/212.

Thermal Treatments
Critical Temperature: 1385F (750C)
Annealing: 1440F (780C), hold 2 hours, slow cool 25F(15C)/ hr max. to 1200F(650C), then air or furnace cool. Hardness BHN 183/212 Stress Relieving
Annealed Material: 1100-1300F(595-740C), hold 2 hrs, air cool.
Hardened Material: 50-100’F(30-55’C) below last tempering temperature, hold 2 hrs, air cool.
Straightening: Best done warm 400-600F (205-315C).
Hardening: (Atmosphere or Vacuum Furnace).
Preheat: 1200-1250F (650-675C), equalize.
High Heat: 1500-1550F (815-845C), soak 10 to 30 minutes. For vacuum or oil hardening, use the high side of the high heat range and soak times. Use the low side of the temperature range for water hardening.
Quench: Oil or water quench to hand warm, 150F (65C). Temper immediately.
Temper: Tempering at 300-500F (150-260C) for at least 2 hours at temperature is recommended. Air cool to room temperature after tempering.  
             
    Physical Properties
Modulus of Elasticity ........................................30 psi x 106 (207GPa)
Specific Gravity ................................................................................7.85
Density ...........................................................0.283 lb/in3 (7850kg/m3)

[sticshooter]

head spinning  :eek:  ... losing sight feeling faint.... You lost me. Doc that blade looks way cool with those colors.<><