Heat Treat quenching

[Phil705]

I have finally purchased an Evenheat oven to do my own heat treating. I've been sending my knives out for two years, and finally got tired of the wait, although the quality has been good. And, I just want to learn how to do it. I have the oven, foil, tongs, internal bricks, etc, but am thinking ahead for quenching. I only do stock removal, and work with CPM 154, 440C, and A2, for the most part.

What would you advise I get in the way of quenching apparatus and materials?

 

[mete]

Two 3/4" thick plates of aluminum and plate quench ! No messy oil etc. All of your steels are suitable for plate quenching.Do a search on "plate quenching", lots of info.

 

[silver_pilate]

Mete's absolutely right. You wrap the blade in foil, follow the recommended pre-soaks and austentizing soaks, and then place the blade, foil and all, between two thick aluminum plates. Maybe put a piece of brown paper in the foil with the knife to burn off any oxygen, but a tight packet will take care of most of that.

Check ebay as they usually have plates for sale at a decent price. I got a 12"x12", 3/4" thick aluminum plate and cut it in half to have two 12"x6" plates. Careful if you're treating more than one blade in succession that the aluminum cools enough (to near room temp) between plate quenches. I tapped and mounted my plates into a wood working vise and attached it to the work bench so I could clamp them down for cooling. Some people just place some weight on the plates or stand on them.

--nathan

 

[fitzo]

Nathan, re-post the pic of your vise, if you would, please....
I use the same setup, and used a wood vise that has one of the "quick release" triggers.
Plate quenching kicks a$$ for air-quench steel. Helps reduce potential for warpage, too.

 

[silver_pilate]

Here's my plate setup. I wanted a vise with a quick release, but was going on the cheap and couldn't find a good quick release I wanted. I should be able to close the plates in just a second or two anyway.

The wood vise is mounted to the table work surface, and the bottom plate is suspended off the table and supported by a piece of opened up angle aluminum to take the stress off the plate's mounting screws. I can open the plates slightly, slip the packet between the plates, and clamp down very quickly. The heat treating oven is on the same work bench just a couple of feet away, so transfer from the oven is quick as well.

BTW, Mike, I do believe I need to credit you for inspiration for this setup. I couldn't remember who had posted this type of setup before, but I got the idea from a picture in a post a while back. And as it was a quick release setup, it was most likely yours. So thanks!

--nathan

 

[jdm61]

If you ever patronize Starbucks, steal a handfull of those little bamboo stirring sticks. Not only are the great for mixing epoxy, JB Weld, etc, but I break off a couple of small pieces and stick them in the foil pack when I am sphereoidize anealing ground blades. A great cheap tool!:thumbup:

 

[azdave35]

i'm a little confused about plate quenching...is this used to anneal the blade before you grind it or heat treat it after it has been ground and shaped

 

[Rob!]

i'm a little confused about plate quenching...is this used to anneal the blade before you grind it or heat treat it after it has been ground and shaped

Plate quenching is part of the hardening process - usually after the blade is mostly ground. It may or may not be followed by cryogenics to 'finish' the quench. They are not used during tempering.

The plates would also not be used for annealing because annealing requires a very slow cooling - and plates do just the opposite.

Rob!

 

[azdave35]

thanks for the reply...what is the difference between hardening and tempering?

 

[hardheart]

hardening-heating the steel until it becomes austenite, than cooling it quickly enough to turn the austenite into martensite. tempering-relieving stress in the martensite to make it less brittle.

 

[silver_pilate]

To further clear up any confusion, the aluminum plates act as large heat sinks to quickly draw heat away from the hardened blade, kind of like a heat sink on a computer chip. This allows a more rapid cooling for air hardening steels than just cooling at room temperature, resulting in a small increase in hardness. An added benefit is that it reduces warps.

--nathan

 

[Rob!]

thanks for the reply...what is the difference between hardening and tempering?

Hardening makes the blade hard so it will hold an edge. Trouble is that it gets so hard it would shatter like glass if you dropped it. Tempering softens it back a bit so it also has adequate toughness.

You asked earlier about annealing. We generally anneal steel that is too hard to shape or work as it is. Annealing would soften it back so that (for instance) a file will bite into it. When done, the steel would need to be re-hardened and tempered

Rob!

 

[Phil705]

OK, I like the aluminum plate system. Thanks. What steel would not work with the aluminum plates? And what do I need for the tempering stage? I am not clear how or if the aluminum plates would work for that.

Phil Millam
Winthrop WA

 

[mete]

The plates are only used for quenching.Tempering is done in your oven [kitchen or HT oven] Plate quenching is suitable for all air hardening steels - all the stainless blade steels and alloys like A-2. It's not quite fast enough for the oil hardening steels .

 

[azdave35]

does it work good on 1095?

 

[silver_pilate]

No, 1095 needs a faster cooling rate than plates can provide. In fact, many people still water quench 1095, but a fast oil will work as well with less chance of cracking the blade.

--nathan