Annealed strength?

[Mike Mossington]

I am putting together a carving knife and fork set for a wedding gift - 440C. I have decided I don't like the fork, and don't have time to get another one to heat treat and back. Will a non-hardened fork be strong enough, do you think?

 

[mete]

It will be about 27 HRc so it will be better if you heat treat it [it would be ok for a wedding cake !!].Why don't you give them the one you made ,then replace it with the second when hardened.

 

[Will52100]

The way I understand it is that stainless steel only achieves stainless ability after heat treat.

Being that it's 440C why not heat it with a torch to non magnetic and oil quench, then temper back to around 350-400deg. F.? That would get it hard, and tempered back enough and it would be stainless, you'd just have a little more clean-up than an air quench. It being the fork the oil quench should work well enough. I wouldn't try it on the knife unless I did a good bit of testing and practice.

 

[Matt Shade]

Yeah you can heat treat 440C in a forge, maybe with a torch, and oil quench. I'm real happy with the results I'm getting, customers seem to like them too. Wouldn't recommend you try it on the knife since your limited on time though. The fork doesn't matter as much, so you should be good to try it if you want.
You need to heat it to a little bit brighter red/orange than you would a carbon steel, and hold it at that temp for awhile. Takes longer to austenize due to all the extra elements. I'd guess that a serving fork would be good after 5 minutes at temp since its not all that thick. Quench in warm oil. Tempering at 400, is good for a knife, for the fork you might want to go a little bit higher.

 

[Alpha Knife Supply]

From Crucibles website:

Hardening
Preheat: 1100/1250F, equalize, 1400/1450F, equalize.
High Heat: 1850/1900F, hold 30/45 minutes at temperature.
Quench: Air, positive pressure vacuum, interrupted oil. Cool to 150F.
Temper: 400-800F, hold 1 hour/inch of thickness, 2 hours minimum.
Tempering between 800 and 1100F should be avoided, due to a decrease in both toughness and corrosion resistancce.

Will52100 is correct. 440C is not stainless unless heat treated. I have some very rusty annealed 440C rod if you want to do some testing.

 

[Stacy E. Apelt - Bladesmith]

Will and Matt,440 is not going to harden properly by torch heating it to non magnetic and quenching it.It requires 1900 degrees,a controlled atmosphere,and a 30 minute soak.If Mike had the ability to do that at his shop,he wouldn't have asked.
Mike,if time does not allow you to get it re-done,do what I do at work when a custom job can't be made in time.Saw a fork out of wood (or twist one out of 1/8" wire) and put in the box with the knife.Include a note saying that the fork was not perfect,and you would only give them a "perfect" gift.Tell them that you will deliver the completed fork in a few weeks.About once a month we wrap a plastic ring in a lovely gift box when a husband comes in two days before him anniversary to order a custom ring.
Stacy

 

[Matt Shade]

Will and Matt,440 is not going to harden properly by torch heating it to non magnetic and quenching it.It requires 1900 degrees,a controlled atmosphere,and a 30 minute soak.If Mike had the ability to do that at his shop,he wouldn't have asked.
Stacy

Re-read my post. I specifically said NOT to just heat it to non magnetic and quench. I'm not telling anyone they have to do it this way, but don't tell me it flat out doesn't work until you've tried it yourself. As far as the half hour to 45 minute soak, I think you'll find thats per inch of thickness.

 

[Alpha Knife Supply]

As far as the half hour to 45 minute soak, I think you'll find thats per inch of thickness.

I listened to a heat treat discussion by Crucible a few years ago. I did not know the presenter. He said specifically the times they list are what is required to get everything in solution including knives. The higher the percentage of alloys in the steel, the longer time required to fully get into solution.

Stacy, I'll have to remember the gift box idea.

 

[Will52100]

As I said, I wouldn't do it with the knife with out a lot of practice and testing to find out what works and what doesn't, but don't tell me you have to have a digital oven and cryo and heat it in a controlled atmosphere and 30 minit soak, and dance a mistic dance while standing on your head to make a fork.

Simple test, objective of this test, see if you can harden 440C with a torch. Heat up a piece for a few minits, quench in warm oil. Take said piece and try to break it, if it breaks like glass and has a fairly(for stainless) fine grain your about rite. Take anouther piece and try same thing again, this time don't break it till after a couple hours in the oven at 400deg.F. Then try to break it, if it breaks after a bit of flex/bending your about right and have heat treated 440C with a torch and toaster oven. Now polish the piece you just broke and submerg it and a piece of polished and anealed 440C in a glass of salt water and see which one rust first. If the heat treated piece goes several days longer without rust than the anealed piece, sucsess!

Who cares if it would make a couple more cuts with an oven heat treat?! We are talking about a fork, it has to be A: springy, B: rust resistant, qualities that are not that hard to come by, just make sure the whole fork is evenly heated and quenched for the stainless properties.