The steel bound for the Freedom Tower at ground zero travels thousands of miles, from a plant in Luxembourg where columns are rolled through casting machines at temperatures approaching 2,340 degrees.

Scrap metal melted into liquid steel in an electric furnace is cast, heated, cooled and heated again at the ArcelorMittal steel mill in Differdange.

The steel makes its way to a plant in Virginia where the huge columns are cut to size. Eventually, it is shipped to New York City, where the columns are lifted by crane and painstakingly set on top of each other at ground zero.

The jumbo steel columns — foot by foot, ton by ton — are forming the skeleton of the 1,776-foot Freedom Tower, designed just after the 2001 attacks to replace the destroyed World Trade Center. Each column makes a 4,700-mile journey, taking weeks and sometimes months to arrive at ground zero.

A steelworker at the Virginia factory, Jim Brown, sees the symbolism in each column.

“It stands for something. It represents something. It represents strength,” Mr. Brown said. “You can tear down a building, but you can’t tear down the spirit of people.”

Steel for the Freedom Tower comes first from Luxembourg, location of one of the world’s only plants that builds columns of that size.

Poured into an H-shaped mold, the steel passes through a continuous casting machine in Differdange, cooled, cut down, and reheated while engineers work at computers in distant control rooms.

The first shipment left Europe in 2006; some 9,400 tons have been ordered so far from ArcelorMittal. Nearly 50,000 tons will be needed to build the 102-story tower.

About two weeks later, the steel arrives at New Jersey or Virginia ports and are trucked to Banker Steel in Lynchburg, Va., where Mr. Brown is waiting.

Fabricated with base plates to connect the pieces and milled so that the ends are completely flat, the steel leaves Virginia, stopping at a New Jersey trucking yard before making the last leg of the trip to the trade center site.

The first Freedom Tower columns to rise at the end of 2006 were painted white, bearing signatures of ironworkers, New Yorkers, and family members of September 11 victims. They are gone from view now, covered with concrete.

The current columns — plain brown, with quality codes scrawled on their ends — are surrounded by hundreds of slender steel rods, trailers, and hundreds of Tishman Construction Corp. workers. Meanwhile, commuter trains snake through the site every few minutes.

Last month, six columns came from New Jersey and were set into place on the building’s west side. An ironworker, Richie Schuler, was there. He returned to the site last October, for the first time since trucks removed over a million tons of rubble from the destroyed towers just after the attacks.

“I was here two hours after the trade center fell,” Mr. Schuler said.

In the beginning, the return to rebuild the site was “a little eerie,” he said, “but it becomes a job.”

By summer, steel will rise above street level for the first time; the Port Authority of New York and Jersey, which owned the trade center and is building the Freedom Tower, says it will take four more years to build: 102 stories, the same height as the twin towers, topped by a spire once likened to the Statue of Liberty’s torch.

Mr. Brown is waiting eagerly.

“We want to bring that completion,” he said. “We won’t be happy until we see the needle put on top of it.”