SCRAP 101 SEMINAR: Chemistry Class

“Keep nonferrous scrap out of the ferrous loads” is probably the most important rule for shippers of ferrous scrap who want to avoid downgrades and rejections based on scrap chemistry.

While there are some general rules that apply to all mills and shipments, there are also a number of variables, Dick Jaffre, a vice president with TXI Chaparral Steel, Midlothian, Texas, told attendees of the Steel Scrap 101 Seminar in St. Louis.

Jaffre’s presentation to the assembled mill buyers and scrap suppliers, entitled “Effects of the Elements on Scrap Properties,” provided a summary of how different alloyed and attached materials found within scrap shipments can affect steelmaking quality.

Even with an 18-page handout to accompany his presentation, Jaffre said he could only address the “tip of the iceberg . . . from 50,000 feet,” when trying to cover the broad array of scrap-melting scenarios.

Jaffre noted that some residual elements may not be bad, and in some cases are desired by steelmakers. In other cases, though, steelmakers set very low acceptable levels for the presence of residual metals such as copper, nickel, molybdenum, aluminum and vanadium. “It’s a very consumer-specific issue,” he remarked.

For some grades of steel with the strictest specifications, Jaffre said that iron alternatives such as HBI and DRI—often referred to as scrap substitutes—are preferred by melt shop managers. “Really, scrap is the substitute,” said Jaffre. “You have to have a certain amount of virgin materials to ensure [proper chemistry]. It’s like saying teeth are denture substitutes,” he quipped.

While mills have varying tolerances for these residual elements, the set of “bad guys” known as tramp elements are almost universally unwanted. The tramp elements are sulfur, phosphorous, tin, lead, zinc, antimony, cadmium and mercury. “They serve no purpose in the furnace charge,” Jaffre said of the unwelcome elements.

He noted that sulfur and phosphorous can be found in pollution control equipment that enters the demolition scrap stream, while lead solder joints, lead pipe, lead-filled counterweights and lead acid batteries that make it into auto shredders are all sources of unwanted lead.

Mercury entering the shredder stream in the form of automotive light switches is well known, while zinc and tin can enter furnaces as coatings on steel scrap or as random items that make it into a ferrous scrap shipment.

Jaffre’s bottom line to scrap processors was, “Keep the nonferrous metal out of ferrous scrap. You’ll make more money, and we will too.”

Jaffre called the issue his “pet peeve,” adding that separating the materials is a primary function of scrap processors. “It is ridiculous how much nonferrous scrap shows up [at Chaparral’s mills],” he remarked. “We pull tin, lead, copper and zinc that you guys should recover and make money from; instead, we do, thank you very much.”