Heat Treating Problem

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MichiganMike

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Yesterday I heat treated six Horace Kephart five inch knives. They were all made of 1084. I use a temp controlled electric furnace. The temperature was 1075 degrees F. After coming up to temperature I quenched them in Parks AAA, which has given me excellent results in the past.

After cleaning them up, the went into our kitchen oven at 400 degrees for two hours. I removed them and cooled them to room temperature and back in the oven again. Here is where the problem lies. Either I left them in the oven too long, or left them in the oven and turned off the oven. The end result is that I have six blades that are too soft. They barely rate 50 Rockwell using the Tsubonsan hardness testing files.

My question: Is it possible to run these blades through the heat treatment process again and get a good result? Thank you for any help you can provide.

MichiganMike
 
MichiganMike said:
Yesterday I heat treated six Horace Kephart five inch knives. They were all made of 1084. I use a temp controlled electric furnace. The temperature was 1075 degrees F. After coming up to temperature I quenched them in Parks AAA, which has given me excellent results in the past.

After cleaning them up, the went into our kitchen oven at 400 degrees for two hours. I removed them and cooled them to room temperature and back in the oven again. Here is where the problem lies. Either I left them in the oven too long, or left them in the oven and turned off the oven. The end result is that I have six blades that are too soft. They barely rate 50 Rockwell using the Tsubonsan hardness testing files.

My question: Is it possible to run these blades through the heat treatment process again and get a good result? Thank you for any help you can provide.

MichiganMike
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You’ll want to try the “shop-talk” subforum for more responses on making knives.

Did you mean to type 1475°F? 1075°F is not going to work out for you and would explain them being too soft.
 
Agreed. Moving to Shop Talk
 
If you quenched at 1075 that's about 400 short. 1475 to austenize then temper about 400. Yes, you can heat treat again. Just gonna have more decarb; thus further grinding, and smaller shivs.

-edit if you had something weird happen during temper it's not going to make them softer, they would be too hard and brittle, also 1084 is generally quenched in parks 50.
 
Agree with above.

To be on the safe side I actually use 1485F for my 1084. It's my understanding that the extra 10 degrees doesn't matter for all practical purposes. (And I've never had an issue nor complaint from any of my kitchen knives.)
 
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