Tuesday, April 26, 2005

Steel, back when

I mentioned before how much easier it is to get steel today. Click the mouse a few times or pick up the phone and place an order, or drive to a supply house or salvage yard and pick it up. But not that long ago...

Iron, after it was discovered how to refine it from ore, wasn't always rare but it was not something you wasted. Bits trimmed off a piece were saved, worn-out horseshoes went into the scrap pile for use later, any piece of iron was saved and re-used. Steel, on the other hand, was a whole 'nother matter.

In its' most basic form, steel is pure iron with a little carbon added. As little as 1/10 of one percent carbon changes the iron, makes it stronger. 1/2 of one percent makes a steel that can be hardened by quenching and is much more wear-resistant. More carbon adds more resistance to wear, and- generally- more use as a cutting tool. Back when, this was the steel available, when it was available, which in some areas wasn't often.

This, by the way, was one of the reasons the sword became the tool of a gentleman and other people higher up on the social scale. An axe can be made of iron with a small piece of steel for the cutting edge, a usable spear point can be made of iron; but a sword requires steel in large amounts and the knowledge, materials and time to work it.

For the smith in a village or many small cities, they might well have to make their own steel. They did this by a process called case-hardening. Basically, take a bar of iron, coat it with a paste made of charcoal and maybe bone meal and other stuff, coat it with clay to seal it and put it in the fire. They didn't know how it worked, but they knew it changed the iron to steel. What happens is that when you hit the magic temperature/critical temperature/ the structure of the metal opens up; when the piece is sealed in with carbon-bearing materials, the carbon can migrate into the metal, changing it from iron to steel. The longer you keep it at heat, the further it can migrate into the piece. If you had the resources you could make a clay chest, fill it with iron rods and the carbon source material, seal it and make a bunch of steel rods at once.

Now, this is a very uneven process. A bar can come out mostly steel on one end, far more iron core with a skin of steel on the other. So someone figured out that if you fold the bar over and weld it a few times, it evens out the quality and makes a superior product. And so it went for a long time in much of the world. You could also take a steel bar, laminate it with an iron bar, and weld & fold them for the same effect.

Done right, this can produce marvelous steel and tools, but it is time & resource intensive, so- of course- shortcuts were taken. An axe or spearpoint could be made of iron & case-hardened, producing a steel skin that could be hardened & tempered, for instance. Of course, if you sharpened the edge from both sides, you quickly wore through the skin and had a soft iron edge. Often the two materials were combined in truly wonderful ways(the Sutton Hoo sword, for instance). Japanese swords were made by a laminating process, and built up of separate pieces with different numbers of folds and welds. The number of folds influenced both the carbon content of the piece, and the hammerwork involved adds something to the pieces itself.

Note: some years back I read where some people sacrificed an old Japanese blade by cutting it up so the different sections could be analyzed as to content. Everyone had thought the edge would be a super-high carbon content, but it wasn't; it was only about .5 percent. It's cutting ability came from the refining hammerwork and very careful temperature control in the hardening process, the great strength from the softer pieces reinforcing it. Also noted was that this would explain the fact that there were definate no-no's involved in using one, as a powerful strike with the blade hitting at a bad angle could bend the blade; there wasn't enough carbon involved in the entire blade to make it more springy.

The laminating and welding process(pattern-welded steel) was often known in the west as Damascus. Not because any came from there, but because of a truly incredible steel that came through there on the trade routes from India(primarily) and a couple of other places. Pattern-welded blades, if washed with acid after polishing, show a pattern from the different layers; this stuff from the east had a pattern but it was in the steel itself, which was a single homogenous piece. More properly known as Wootz, it had(and has) an incredibly high carbon content for a steel, and would cut and hold an edge like nothing else on earth. Sometime in the 80's a smith named Al Pendray got together with a metallurgist and decided to make some. Lots of experimenting later, using only materials available back when, they succeeded. Pendray reported that it was a cast-iron bitch to forge(my words, he was quite a bit more polite); it was very hard to move under the hammer, and if a wind blew across it as you were working and cooled it just a bit too much, the next blow might crack it. But the end result was worth it: blades with a watered patterning on the surface, that would take an extremely fine edge and hold it in use.

Centuries later, an English clockmaker had a problem. He needed very precise springs for his work, but the best steel available wasn't quite good enough; some if it was a LOT not good enough. And he had an idea. He case-hardened some rods to make them into steel, broke them into pieces, sealed them in a crucible and melted them in a furnace. When cooled, he worked the steel out and wonderful! Steel of even quality throughout, that could be made into the springs he needed. This stayed his trade secret for years, and then it got out. I've heard that in years to come one of the ways this would be worked was to case-harden large bars, quench them, break off the steel skin and melt it to produce the superior product.

Starting in the late 1800's, they figured out how to use a blast furnace to purify iron and then add the alloying elements in to make steel, and now you can get all kinds. Water, oil and air hardening, shock-resistant, stainless, etc. For literally pennies a pound for stuff people a few centuries ago might have killed for.


Kevin said...

One of these days I'm going to plop down the cash necessary for a really nice pattern-welded fixed-blade knife.

I read up on the recreation of the Sutton-Hoo sword. Damn! That was beautiful!

Firehand said...

Oh God yes! An absolutely masterful piece of work.