Heat treat fail

[TexMac]

I heat treated 3 A2 blades today and one blade had a 1/2” long section of the blade that was soft and by soft I mean felt like aluminum the way the file bit. File slid right across the rest of the blade. The blades were wrapped in foil and I basically insert the wrapped blades in a 316 stainless tray to shield from radiant heat. I heat slow to 1100 then ramp to 1450 and equalize. Then ramp to 1775 for 35 min and plate quench. Same process I’ve used many times before and never had this experience. Any thoughts? Thanks for any input.

 

[Tom Lewis]

Are you sure the steel was A2?

 

[TexMac]

I’ll double check but it was an unopened precision ground bar.

 

[HSC ///]

Did u stack the blades 3 high? Or lay them next to each other?
Are the all the same length pattern?
What’s the blade thickness?

what’s the point of the 316 tray?

I see no need to do the 1100 and 1450 equalize. I think that’s for thicker industrial parts. I don’t think that is necessary for thin flat blades

1775 at 45 mins should give you high hardness.

but as you said you’ve done it many times before, so you are checking the steel to make sure it’s A2

 

[TexMac]

The tray has pegs to divide the blades just like a normal ceramic one so the blades stand up. Only difference is the tray has sides to shield the blades due to the close proximity to the coils ( small kiln ). Blades were different patterns but all 3/16” stock similar length. However, the one that failed was for a different bar. I agree probably don’t need to equalize at the difference temps I usually soak at 1775 for 35 min just because the kiln heats so slow.

 

[Tom Lewis]

The reason I asked about the steel is one time I bought some AEB-L steel and it turned out to be something else.
From now on when I buy steel I not only put the name on the steel but I also put where I bought it.

 

[TexMac]

I did double check and it was A2, after you mentioned it I did want to make sure I didn’t grab a package of D2 by mistake.

 

[Stacy E. Apelt - Bladesmith]

I would grind into the soft spot a bit and see if it is a deep layer of decarb caused by a pinhole or bad fold in the foil.

 

[TexMac]

I would grind into the soft spot a bit and see if it is a deep layer of decarb caused by a pinhole or bad fold in the foil.

Thanks. I tempered the blade along with the other 2 as normal then started grinding and hit hard steel after maybe .010” didn’t even really change blade profile. The pin hole leak was more apparent after temper. The area with the decarb turned dark gray. Glad I didn’t toss that one.