One after the other, Chinese importers reneged on copper scrap contracts last fall, driving swarms of US exporters to swear off future deals with the Asian giant. Now that buyers there have reopened their wallets, are once-burned Yankees ready to let bygones be bygones?

It started like any other deal. An international ingot maker signed a contract with a U.S. scrapyard for a shipment of copper scrap. Weighed, packaged and priced, the order was loaded onto a ship, transported across the world and unloaded on a Chinese dock to await pickup.

But instead of taking delivery of material and paying the agreed-upon prices, droves of Chinese buyers left shipments untouched as they demanded lower prices—prices so low that exporters accepting the deals would be selling at a significant loss, though not enough to warrant bringing the product back to the United States. With the material on the far side of the ocean, the Chinese buyers held the power, and a slew of domestic scrap traders were left hemorrhaging money into the East China Sea.

Such was the plight of hundreds of U.S. and European scrap traders last fall, forced to renegotiate prices...