Crucible Steel

[Doc Ivory]

I'm new to knife making and just heard the term "Crucible steel".
Can't find a reference for that.

What's Crucible steel?

 

[Many Klatch]

It's an early manufacturing process for making steel. Crucible steel is better than what came before but not as good Bessemer Process Steel.

(From Google) Crucible steel is steel made by melting pig iron (cast iron), iron, and sometimes steel, often along with sand, glass, ashes, and other fluxes, in a crucible. In ancient times steel and iron were impossible to melt using charcoal or coal fires, which could not produce temperatures high enough.

As steels go it can have lots of inclusions and soft and hard spots.

 

[Doc Ivory]

It's an early manufacturing process for making steel. Crucible steel is better than what came before but not as good Bessemer Process Steel.

(From Google) Crucible steel is steel made by melting pig iron (cast iron), iron, and sometimes steel, often along with sand, glass, ashes, and other fluxes, in a crucible. In ancient times steel and iron were impossible to melt using charcoal or coal fires, which could not produce temperatures high enough.

As steels go it can have lots of inclusions and soft and hard spots.

Thanks!
I remember some of the Bessemer process but nothing about crucible steel.
-Jim

 

[Doc Ivory]

Wasn't Bessemer's process the usage of hot air to oxidize impurities?

 

[Canute Rex]

Yes, Doc Ivory. Bessemer's process was to blow heated air through molten iron. The issue was that, as originally smelted, cast iron had far too much carbon in it. Maybe 2-3%. Usable tool steel is below 1.25% and mostly below 1%. Blowing the air through oxidized away the carbon. At first they tried calibrating how long they held the blast to hit a carbon percentage target. That was too difficult, so they ended up blasting out all the carbon and then adding a selected amount back in to the pure iron.

Crucible steel got at the same result by dilution. They mixed ultra-high carbon cast iron with lower carbon wrought iron and flux. It was melted in a crucible (hence the name) to keep it from being exposed to carbon monoxide in the furnace and picking up more carbon.

Once I helped a friend with an experiment where we heated mild steel in a charcoal fire in a clay furnace with limited oxygen. It's called an Aristotle furnace. The excess carbon monoxide combined with the low carbon steel and we got a melted lump of tool steel on the end of a mild steel rod.

 

[Rifleman1776]

"early process" is right. Alex Hamilton used it in his factory when the process was first discovered.

 

[Doc Ivory]

Yes, Doc Ivory. Bessemer's process was to blow heated air through molten iron. The issue was that, as originally smelted, cast iron had far too much carbon in it. Maybe 2-3%. Usable tool steel is below 1.25% and mostly below 1%. Blowing the air through oxidized away the carbon. At first they tried calibrating how long they held the blast to hit a carbon percentage target. That was too difficult, so they ended up blasting out all the carbon and then adding a selected amount back in to the pure iron.

Crucible steel got at the same result by dilution. They mixed ultra-high carbon cast iron with lower carbon wrought iron and flux. It was melted in a crucible (hence the name) to keep it from being exposed to carbon monoxide in the furnace and picking up more carbon.

Once I helped a friend with an experiment where we heated mild steel in a charcoal fire in a clay furnace with limited oxygen. It's called an Aristotle furnace. The excess carbon monoxide combined with the low carbon steel and we got a melted lump of tool steel on the end of a mild steel rod.

Thanks...
This is why i sit in on these forums.
An answer even I can understand.

-Jim

 

[Doc Ivory]

Just watched a few videos on youtube about creating crucible steel.
It's certainly an artform.

-Jim

 

[Mulebrain]

Too bad the video quality is poor

 

[Doc Ivory]

Thanks!
I'm going to go out and troll NOVA for this episode.

 

[Mulebrain]

Thanks!
I'm going to go out and troll NOVA for this episode.

It's very interesting

 

[user 48679]

The steel is formed in a crucible - which is an air-tight, high-temperature oven, made in ancient (and not so ancient) times by using a mortar mix to seal a chamber made of rocks after the raw materials are placed within.

Doing so correctly can take a considerable time of blind baking (if you will) - which takes multiple times to gain the experience to judge when the metal's "cooked" enough.


(google " making an Ulfberht Viking sword" )

 

[Chuckster60]

This may shed a bit of light regarding knife making and "Crucible steel". Not to say I disagree with all of the prior post's that have "hit the nail on the head" !
So when I melt lead in in a crucible I have made crucible lead bullit's now that is a REAL bullit!
Jim Beckman Crucible Industries Knife Steel Interview (knifeart.com)

 

[Rudyard]

I believe you must credit Benjamin Huntsman clock maker of Sheffield and the Abbeydale industrial Hamlet Millhouses Sheffield . He suaght reliable steel for clocks springs Mid 18c . The Hamlet now restored occasionally operrates .
Rudyard

 

[Artificer]

I believe you must credit Benjamin Huntsman clock maker of Sheffield and the Abbeydale industrial Hamlet Millhouses Sheffield . He suaght reliable steel for clocks springs Mid 18c . The Hamlet now restored occasionally operrates .
Rudyard

That's correct. Funny thing, though, is the steel made from his process was at first rejected by English Steel Workers in Birmingham and to a lesser degree in London, because it was more difficult to harden/anneal than earlier steels. So Huntsman at first sold most of his steel to the French and to a large degree, those who made scissors and shears. Well, when those scissors and shears proved much better than made in England, the Birmingham makers reluctantly learned to do what was necessary to learn how to harden and anneal it correctly.

Gus

 

[LRB]

Just a FYI. The original true Damascus steel was a crucible steel. What we call Damascus today is a pattern welded product of two or more different types of steel. The process for making true Damascus steel was kept secret for so long, it apparently was lost until just recently, but it was made by a crucible process.

 

[Rudyard]

A bold observation and welcome. Somewhere in the mix is Wootzs from India & the swords of Damascus . The Barrels I believed where a speciality of what we call Kurdistan. Rigby was the noted maker who according to John Nigel George first produced Damascus circa 1818 . (As apposed to Twist) barrels and pickled them to produce the enhanced grain per good Kurdish work . How accurate we both are Ide love to find out,
I see it as pieces in a puzzle we are unlikley to find .But they might turn up in the near East one day if so much is lost in the turmoils of these regions in the last two hundred years . I remain an ardent devotee of good Damascus that the FMEs so unkindly condemn, Probably akin to the new duellers V the originals it has what could be called a 'soul'. Or am I being too poetic ?.
Rudyard