S7 heat treatment

[kenre]

I have been told i need to heat treat S7 tool steel in a stainless bag to avoid de-carburisation. If the bag is sealed, wouldnt it pop from pressure buildup? of is this not an issue. I need to harden, then, temper to 58/60 Rc.

Also, where can i locate bags in Australia?



Ken

 

[kenre]

I have an LPG (Propane) fired oven. Previous heat treating i have done i placed a thermocouple wire directly into the part.

I have plenty of Kaowool on hand.

Have been thinking of how i would cobble up a vacuum chamber for use in the oven. Stainless steel container, with a vacuum pump connected and running continually, Havent worked out a quick and easy way to remove parts for quenching as yet.
Does this sound feasable?

Ken

 

[twistedneck]

kenre, I went the argon feed route. works well. For part transfer i made a special holding brick. I remove the brick + part from the oven with a custom set of tongs.

I made the tongs just for that brick (its like a channel brick), then i get over by the salt pot, transition the brick to vertical still containing the part, and use hand size tongs with my other hand to pull the part out of the brick and dunk in salt ( i have a littel stainless tab on it).. next i set the brick down, grab the hanger and put it in place to let the part soak.

your idea about vacuum sounds great, but how well sealed is your furnace? also, propane firing normally involves oxygen in the chamber right?

 

[kenre]

twistedneck, My idea of the vacuum furnace would be to heat the chamber within the the existing oven.

I did think of using an Argon atmosphere instead of a vacuum, no need to worry about having a perfect seal this way.
I always have Argon close by for TIG welding.

 

[twistedneck]

Kenre, i wondered how that would work.. Those Retorts are great, except how would you remove the part quickly?