Isn't it amazing what a stock can do when Wall Street gets religion about an entire sector? In less than six months, the stock of leading steelmaker Nucor (NYSE:NUE) has nearly doubled, as investors have mustered renewed enthusiasm for the entire steel sector.

Last week, we got some confirmation that the enthusiasm is grounded in some real performance. Nucor saw revenues climb 7% from the year-ago period, as a double-digit increase in shipments offset a decline in pricing. Though the company did see higher per-ton energy costs year over year, a meaningful decline in scrap costs helped mitigate that impact. By my math, operating income was up 8% from last year's first quarter.

Though Nucor management generally seems conservative about future expectations, its latest justification for that caution got my attention: concerns about potential scrap costs and the possible impact of imports. The folks at Steel Dynamics (NASDAQ:STLD) didn't seem so bothered by either of those factors -- though they did admit that scrap costs are difficult at best to predict.

Imports will be interesting to watch, particularly in the second half of the year. Right now, American steel goes for a higher price than international benchmarks, and I can see how that premium would be enticing. The big question, though, is actually a multi-parter: How much steel will the Chinese produce, how much will they consume, and how willing are they to risk antagonizing the U.S. in an election year with cheaper Chinese steel imports?

I don't presume to know the answers, but I know a few other things that make me feel better. First, inventory levels at steel service centers were low earlier this year and probably haven't refilled yet. Second, Nucor believes in investing in technology, and some of that technology (like Castrip) could be "disruptive" to the industry as a whole -- and good for Nucor's business.

Nucor stock isn't cheap enough for me to make it my No. 1 pick in steel -- that's a three-horse race for me between Steel Dynamics, Chaparral (NASDAQ:CHAP), and MittalSteel (NYSE:MT) -- but that doesn't mean I'd sell it. It's a great steelmaker, and it's more than met the test of time.

For more Foolish thoughts on the metals:

Mittal Steel is a Motley Fool Inside Value recommendation.

Fool contributor Stephen Simpson owns shares of Mittal Steel, but has no financial interest in any other stocks mentioned (that means he's neither long nor short the shares). The Fool's disclosure policy is into heavy metal.