Bad edge retention

S

Shipshores

Joined
Apr 2, 2016
Messages
114
I've been working with w2 recently and only get about six cuts through 1/2" manila rope before the edge starts sketching on paper. I don't have a hardness tester but I get good Hamons so I know they are getting hard. I tried tempering from 350,375,400 and 425. My edge thickness is .035" prior to sharpening. What am I missing.
 
I don't have heat treating experience but I'd say your edge is way too thick. Try bringing it down to at least 0.015" and see how it goes.
 
On a slicer, I go to almost sharp before putting on the edge. .005". If you leave the edge at the pre-HT thickness of .035" and then sharpen the knife , it is way, way, way too thick. Yopu have to sand/grind down the bevels to the final edge thickness after HT.
 
I usually thin the bevel more but I wanted to rule out the a thin edge being the cause.I made a batch of test knives and wanted to try to figure out my heat treatment for the w2. I just can't figure out why my edge retention is so bad. The tips easily broke even with that thickness. Could it not be getting fully hard and still have a hamon? Maybe the steel is bad.
 
The hamon has nothing to do with hardness. It is just a boundary between structures.

I would take a good look at your HT specs and look for things that make a poor edge. Too hard is just as much a problem as too soft. Grain growth and overheating the edge in HT is a big problem with hyper-eutectoid steels.
 
I checked the grain and it looks good. So it may not be getting completely hard. Should I try a longer soak or up the temp. I have a fine grain so maybe go up till I see growth and then pull back a little from there? I'm using a evenheat and 1450f for 10min. Quenching in parks 50. This batch of knives is stock removal and I did not normalize.
 
I have a 1450f tempilstick, should I put a piece in the oven a see if it melts at 1450 to verify the oven temp? Not sure if that would be accurate.
 
Are you establishing your initial edge under power...? or entirely by hand..?
 
Under power, it's easy to overheat the apex without knowing it.
 
It might be a good idea to send a blade for hardness test. I had a nice petty done recently, everything seemed ok including the hamon. Turns out it was around 52 RC.
 
Just as more food for thought:

W2 varies greatly. If it comes from Aldo, it is likely 100% spheroidized. That means before final HT it needs a cycling at 1650F , 1500F, and 1350F to break up the carbide balls. Use 15 minute soaks on each cycle. If it is from some other source, it may be spheroidized or not. If it is from a non-supplier source, it may be of varying carbon and alloy content.
 
Once you have your Heat treat regimen for the W2 in place and are getting consistent results with your RC, then move on to doing differential harden. Ive been pulling hairs out and wish I did that from the beginning :)
 
The specs on W2 are .70-1.40 % Carbon !! That's a lot ! You might check with Aldo or other supplier on what they get for their steel.
I haven't brought up this little fact for along time but the facts haven't changed in at least the last 60 years !!
A steel mill may have their own range that is within the .70-1.40 % C for example .90-1.20 % C . This is done for needs of their typical customers.
 
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