frizzen hardness

[jerrywh]

 Wow Jim.
   Five hours is a long time to pack harden. At 1600° tha tcarbon is just about going all the way through a frizzen. I have been annealing them, engraving and repack hardening for 1 hour at 1550°
 What kind of steel is the foundry casting the frizzens out of?

[Acer Saccharum]

I have taken to annealing frizzens for working them, after spending countless hours stoning a hardened frizzen. A frizzen in the annealed state is easily filed, engraved, whatever you want to do with it, is so much easier and takes much less time. You can do things to soft steel that you cannot with hardened. Engrave, change the curvature of the face, change the shape of the cover and tail.

Before hardening, anneal again when the work is done, especially if you've gotten the face red hot to change the bend. Annealing makes the crystal structure in the frizzen more uniform, with few internal stresses.

[JCKelly]

jerryw I know you meant Jim Chambers but I'll kick in my $0.02 as a metallurgist.

Whatever steel your foundry uses, they pour that 2600F+ molten steel into pre-heated ceramic molds. As it cools, carbon burns out of the surface layer. I really don't know how thick this "decarburized layer" is on a frizzen. i do know one must replenish this carbon if one expects that frizzen to spark, to have a hard face.

It is also a great idea to anneal or normalize any investment casting to refine the grain size before you use it, or before you harden & temper it.

[jerrywh]

JCKelly
   When the steel cools in the mold why does it not anneal then?
 I know whaty you are saying is true about the surface carbon burning out but it is probably only a thousands or so deep, Right?

[Mark Elliott]

Wow Jim.
   Five hours is a long time to pack harden. At 1600° tha tcarbon is just about going all the way through a frizzen. I have been annealing them, engraving and repack hardening for 1 hour at 1550°
 What kind of steel is the foundry casting the frizzens out of?

I believe I remember Jim Chambers saying that they used 1095 for the frizzens.

[bgf]

Mr. Kelly is correct in stating that the frizzen castings loose carbon while cooling in the mold during casting.  They also harden somewhat during that time making them very hard to drill for the screw.  To solve both problems we pack all of our frizzens in a carbon material as soon as we receive the castings from the foundry.  They go into an oven and are heated to around 1600 degrees for five hours.  Then, the oven turns off and cools slowly for about 24 hours making the frizzens soft enough to drill without any problem.  The five hour heating in the carbon more than restores any carbon lost in the casting process.  We don't see any need to add any more carbon to our frizzens during the hardening process, but we do use a carbonizing flame to heat our frizzens to prevent any carbon loss.
We also do the same treatment to our springs, tumblers, flys, and sears to restore any lost carbon and to anneal them for machining.

This explains a lot about why my late ketland works so well!

[JCKelly]

I learned from expensive (to Black & Decker, not me - my boss'[s fault) experience that steel investment castings, specifically 4140 in this case, come out of the mold with grains the size of your face. However hard or soft they may be, hardness will vary from place to place on the casting. Lousy idea to use steel investment castings just as they come from the foundry, without some manner of heat treatment.

Annealing or normalizing will grow new grains, finer grains. Fine grains are good, coarse grains are very bad.

To digress a bit for Today's Metallurgy Lesson. You have no doubt heard, or said yourself, something like "it crystallized and broke". That was state-of-the art thinking until about our uncivil war. Then someone used a microscope &c, learned that metals are always crystalline. Thing is, the crystals (I would say "grains") are too small to see with naked eyes. If they are large enough that you can see shiney crystal-like things in a fracture, they are way, way too big. Big grains make things brittle. They did not get brittle from how the thing was used, or how old it was. They got brittle from the previous heat treating or, especially, forging operation on the piece. Forgings should also be annealed or normalized (NORMAL-ize = heat it red & set it down on the floor to cool)