A Curious Conundrum In Heat Treat

[WBE]

HTed two blades of 01 together. Blade #1 1/8"x 1 1/8"x 6". Blade #2 5/32"x 1 1/2"x 9 1/2". Both with distal taper. Both well coated with PBC for decarb protection. Evenheat oven. Both blades were stock removal. Both were sub critical thermocycled at 1200?, then soaked at 1475? for 20 minutes, then quenched point down in 5 gal. of Parks AAA, warmed to 130?. Blade 2 went in first, came out evenly hard. Blade 1 continued soaking while I checked blade 2. Blade 1 then was quenched, and came out with the last 3/8" at the point soft. It could be cut with a dull file in this area, but the rest was hard as should be. Repeated the entire process on blade 1, less the thermocycle. Same result. Ground point back 1/2", reshaped accordingly and again repeated the HT. Same result. Took a piece of 1/16" 01, made a test blade with bevels and purposely made the point even thinner than blade 1. HTed with same process, came out perfect. I am thinking blade 1 has a longitudinal band of low carbon in line with the point. Kevin, Mete', anybody, what is your opinion??? This was Starret brand PG 01.

[Gary Mulkey]

I can't explain this but I would be tempted to call Sterret and ask customer service if you could talk to one of their engineers (have your invoice handy to tell them as much about the steel as you can). It's possible that they may have had a bad batch that they are aware of or could explain what's going on.

Gary

[mete]

AFAIK, Starrett doesn't make steel. But it's definitely a weird situation !! AAA is a very fast quenchant and should have no trouble hardening any blade of O-1 .A chemical analysis of the good and bad sections would be a start but if there is a difference why would there be ?? It would be nice to talk to a metallurgist in the mill that made it.Does it say 'made in China' ?

[Kostoglotov]

Starrett should have the MTR/CTR's on file.

It might be a good start

[pipecrafter]

I once had the exact same problem on a small knife I made - the tip was as soft as the tang, but the belly of the blade was super hard. When I etched it, just to see what I could see, the tip etched similarly to the tang. Every other knife I made from that bar HTed fine though, so I just chalked it up to improper HT on my part - possibly overheating the tip or something.