"That's going to be difficult to explain," Eleanora said with a frown. "It involves molecular chemistry."
"I'll give it a shot," Roger said. "Targ, you know how when you first smelt the ore, you get 'black iron.' The brittle stuff, right?"
"Yes," T'Kal Vlan agreed. "It's what was given to Cord's tribe, that broke so easily."
"You have to remelt it," Cord put in. The wounded Mardukan was seated behind Roger, as was proper, but stretched out on cushions to save his ravaged legs. "Very hot. It's hard and expensive, which is why black iron is cheaper."
"Okay," Roger went on. "Then when you heat it in a crucible, 'very hot,' as Cord said, you get a material that's gray and very easy to work."
"Iron," Targ said. "So?"
"That's what we call 'wrought iron,' and it actually is almost pure iron. Iron is a molecule. Black iron is iron with carbon, which is what's in charcoal, mixed into it."
"What about steel?" T'Kal Vlan asked. "And why do I think we need an ironmaster here?"
"Somebody else can explain it later," Roger said with a laugh. "The point is that iron is a pure element, a kind of molecule. Is that sort of clear?"
"I hear the words," Targ replied, "but I don't know their meaning."
"That would be hard to really explain without teaching you basic chemistry first," Dobrescu said. "You're just going to have to take our word for most of this and I'm not sure how much you can do with it."
"The point is that steel is also iron with carbon in it," Roger said. "But less carbon, and heated to a much higher temperature."
"That much is well known to our master smiths," Targ said, with a human-style shrug. "Yet mere heat and tempering does not produce the water steel. Even in exile, our smiths have forged weapons far superior to those of other city-states, but never the water steel of Voitan."
"No, steel is complicated," Roger agreed. "Especially 'water steel'—what we call 'Damascene.' We—well, I—was really surprised you had it and of such quality. It's unusual at your technology level."
"I think it's driven by their pumping industry," O'Casey interjected. "They have quite a bit of refined technology dedicated to pumps. Once that starts to spread out a bit, look for an industrial revolution. I wish they were just a bit further along. If they were, I'd introduce the steam engine."
"Let's stick to the subject, if we can," Pahner suggested with a slight grin, "and reengineer their society when we can do it with a regiment at our back. Okay?"
"His Highness is right," Dobrescu went on to Targ, ignoring the captain's amusement. "Normal steel is specially formed iron with a bit of carbon and high temperature, but you need some other impurities, if you want good steel, which explains Voitan blades. The first thing to realize is that the local ore is what we call 'banded iron.' "
"I know," Roger said. "Geology, remember? It's formed by early oxygen-generating organisms. Prior to their evolution, atmospheres are mostly reducing, and iron can remain on the surface in a mostly pure state. But once the first green or blue-green organism occurs and starts producing oxygen, the iron rusts. Then the oxygen gets used up over millions of years, and there's a band of non-rusted ore, then another band of rusted ore. Right?"
"Right," the warrant officer agreed. "Which makes it some of the best possible taconite, so it's comparatively easy to work. But, even better, it's contaminated with vanadium, which is one of several possible hardening agents for steel. Molybdenum and chrome are a couple of others."
"Molybe—molby—?" Cord grimaced. "I can't pronounce that."
"Don't worry about it," Dobrescu said. "The point is, Targ, that it really is the local ore, and your know-how, that's special. And I ran a tap in on one of your main mines, and it's all laced with impurities: vanadium and molybdenum. In fact, I'd give odds that by the time you get back into full swing, you'll hit a vein that makes the best steel you've ever seen."
"Ah, good," Targ said. "We have long wondered what it was that made our water steel. That's part of it, surely."
"Hold on a minute," Roger said, frowning at Dobrescu. "Vanadium and molybdenum are important, yeah, but not really critical for sword steel, Doc." The warrant officer blinked at him in surprise, and the prince chuckled with a humor that was more than slightly sour. "I won't claim to be an expert on the topic," he said, "but no MacClintock can avoid learning at least a little about ancient weapons... no matter how hard he tries."
"Oh?" Dobrescu cocked an eyebrow, and Roger shrugged.
"Oh," he replied. "Vanadium helps produce a finer grain structure in heat-treated steel, which helps with the tempering process and eliminates some of the problems in overheating steel. And it helps prevent loss of temper in reheated metal, so steel with vanadium in it can withstand higher temperatures before losing its temper.
"Molybdenum does some of the same thing by helping to transmit the temperature deeper into the steel, and it also increases hardness some and helps reduce the fatigue factor. But carbon is the most critical element in hardening steel."
Both of Dobrescu's eyebrows had risen during the prince's explanation, and the warrant officer's surprise was not an isolated phenomenon. Even O'Casey was staring at her one-time student, and Roger shrugged.
"Hey, like I said, I'm a MacClintock," he told them.
"According to something I read years ago, though," Dobrescu said, "vanadium and molybdenum were what produced Damascene steel."
"Almost right," Roger told him. "The 'water pattern'—those white lines on the black background—are a crystalline damask that's largely the result of those sorts of impurities. But you can have that kind of pattern on a blade that really sucks. Good Damascene steel hits a carbon content of something like one and a half percent, if I remember correctly, but even then, the trick is in the tempering. There are some beautifully patterned blades in the Roger III Collection that were never properly heat treated. I think their Rockwell number was only thirty or so, which would make them pretty useless as real weapons. You need to hit a Rockwell of around fifty if you want something to cut through mail and bone like this baby." He touched the katana lying beside him even in T'Kal Vlan's tent
"Really?" O'Casey asked, trying to hide her delight at hearing Roger—her Roger!—in professorial mode. Sort of.
"Yeah. There were different techniques for making the good stuff back on Old Earth," Roger told her. "Europeans did it with pattern welding, the Japanese used mechanical construction, but the Indians probably did it closest to the way Voitan smiths did it, judging from this." He touched the katana again. "They heated the steel in sealed clay crucibles that allowed the iron to soak up lots of carbon."
"That is, indeed, how our craftsmen work," Targ said, regarding Roger narrowly. "It is part of our closely held craft secrets," he added, and Roger grinned.
"Don't worry, Targ—I don't plan on telling anyone else. But the humans who used that technique produced something called 'wootz' steel that happened to have the very impurities the Doc here was talking about thanks to the local ores. And he's probably right that their presence helps account for at least some of your weapons' superiority, but don't let that distract you. The real secret's in the tempering and how well you judge temperatures and what quenching techniques you use. You might not get as pronounced a 'water' pattern using steels without the impurities, but your people would still be turning out some of the best weapon-grade steel in the world!"
"But it is the water steel which warriors associate with the superiority of our blades," Targ pointed out. "It shows the soul of the steel."
"And it's flat out beautiful, too," Roger agreed. "I'm not saying the nature of your ore isn't important, just that you shouldn't sell yourselves or your smiths short. The hardest thing of all in making a true master blade is the tempering, and you guys obviously have that down. For the rest—" He shrugged. "Now that you've got access to the right ores again, everyone else will see that the true 'water steel' is back. I imagine that's going to do good things for your income while you rebuild the city."