The great debate? Is stainless steel best classified as a ferrous or a nonferrous metal? The answer isn't so simple.

Some things can't be neatly classified, such as that jock from your English lit class who wore sweater vests, listened to Devo and Loretta Lynn and knew everything there was to know about Fellini. He moved from clique to clique; and while he wasn't rejected, he wasn't completely accepted either because no one could quite figure him out. In high school, where stereotypes reign, someone who doesn't fall neatly into a clique tends to puzzle his classmates.

Stainless steel can elicit the same sort of befuddlement. Until asked the question, "Is stainless steel a ferrous or a nonferrous metal," you probably never gave it much thought. But once confronted with the question, you may begin to realize a lot of factors have to be considered before answering. And some may ask: Is the question ultimately even important?

DEFINING CHARACTERISTICS

According to the Specialty Steel Institute of North America (SSINA), [Web site www.ssina.com], stainless steel is a low carbon steel containing chromium levels of 10 percent or more by weight, while the carbon content is less than one percent.

Stainless steel is available in more than 60 grades, which are divided among five classes defined by the alloying elements.

Basic stainless steel, or maretensitic, contains 12 percent to 18 percent chromium, according to the SSINA. These stainless steels are magnetic, hardened by heat treatment and have poor welding characteristics and often are used in knife blades and surgical instruments. The grades include 410, 420 and 440C.

Ferritic stainless steels contain less than 0.2 percent carbon, though their chromium content remains in the range of 12 percent to 18 percent. Ferritic grades are magnetic, though they are not heat-hardened, and are used in automotive exhaust lines, architectural trim and cooking utensils, according to the SSINA. Grades include 409 and 430.

Austenitic stainless steels contain nickel as well as a higher chromium level. These grades are not magnetic, are hardened by cold working, are highly corrosion resistant and are easily welded. Austenitic grades, such as 304, 310, 316 and 317, are used in roofs and gutters, kitchen sinks and chemical vessels, according to the SSINA.

Duplex stainless steels have chromium content in the 18 percent to 26 percent range, with nickel ranging from four percent to seven percent. According to the SSINA, most grades also contain two percent to three percent molybdenum. These grades are weldable. They are highly resistant to stress corrosion cracking and higher tensile and yield strengths than ferritic and austenitic grades and are used in heat exchangers and food pickling plants. A popular grade is 2205.

How would you define stainless steel? Are you not so sure after the introductory science lesson? Keep reading, but I can't promise you things will get any clearer.

ONE OR THE OTHER

Gerry Stewart, executive vice president of ELG Metals, McKeesport, Pa., says without hesitation, "I consider it a ferrous grade. The benchmark grade, 304, is 75 percent ferrous. In the ferritic grades, the ferrous content can be as high as 85 percent to almost 90 percent."

Bill Heenan of the Steel Recycling Institute, Pittsburgh, agrees. "Anywhere from 70 percent of stainless steel typically is iron. If it's iron, how can it be anything but ferrous?

Chalk up another vote on the ferrous side from Michael Marley, secondary metals editor for American Metal Market, Philadelphia, who also says iron's predominance in the metallurgy qualifies stainless steel as a ferrous metal.

"Most of the guys who are the consumers from my perspective tend to be members or the steel industry or are to be found on the steel industry side," Marley says. He adds that the stainless steel production process is similar to electric arc furnace steel production. "They may require some additional secondary treatment depending on whether it's a argon-oxygen decarburisation process that they are using or just some form of ladle metallurgy which most steel companies use now whether producing stainless or carbon steels."

Heenan says the biggest factor in classifying stainless steel as a ferrous metal is its consumption of about two million tons of steel scrap every year. "Now, that's not much considering the 60-plus million tons ... that the carbon steel industry [consumes]."

Randy Castriota of Castriota Metals & Recycling, Pittsburgh, says he considers stainless steel to be nonferrous, though the question caught him off guard. "Most of the nonferrous metals are nonmagnetic, such as copper, brass, aluminum, and most of--I'm not sure on a percentage basis--of stainless is nonmagnetic." In scrap yards, stainless steel is almost never placed in the same pile as scrap iron and carbon steel.

Stewart says, "The national association ISRI (Institute for Scrap Recycling Industries Inc., Washington) has two categories: nonferrous and ferrous. It's always very confusing where we fit as stainless processors."

Marley has found little consensus on the topic among members of the industry. "I've talked to guys who consider it a nonferrous metal in part because of the nickel being such a significant driver or the price--primary nickel price, anyway--which is their focus and their interest they way they see it."

Castriota says that the higher price of stainless steel is a point in favor of the nonferrous definition.

Patrick Ryan of Ryan's Notes, Pelham, N.Y., responds quickly to the question, saying stainless steel is a nonferrous metal--at first. Then he reconsiders. "Let me think about this. It's a ferrous metal." Before the interview is over, he changes his mind yet again.

The type of confusion caused by the stainless steel ferrous vs. nonferrous debate is reminiscent of a restaurant customer unable to make up his mind: "I'll have the steak. No, the fish. No, the pasta!"

SOMETHING SPECIAL

"Stainless steel grades are actually ferro-alloys; they're not steel. I think there's a misnomer," Ryan says. Ryan would rather stainless steel was more closely identified with the underlying alloying element, whether nickel, chromium or other metals. "It would be much more descriptive than just stainless steel," he says.

"The value of the steel is so insignificant due to the value of the ferro-alloy content of it, that I consider it to be a ferro-alloy rather than a steel product. All you've got to do is look at the price of nickel," he says.

"Carbon steel is the basis, but when you get to the stainless steel, whether it has tungsten or nickel or chrome ... hI mean the real value is in the alloy content rather than the base product, which is the steel. To me, whether it's ferrous or nonferrous ... really isn't the relevant part," Ryan comments.

The question as far as Ryan is concerned is: Is stainless steel a ferro-alloy, or is it a type of steel?

ISRI's director of commodities Bob Garino says, "Yes, stainless steel is just `special'--in a class all by itself. Maybe because when compared to such all encompassing terms such as `nonferrous' and `ferrous,' the more narrowly defined stainless steel industry can (and should) stand alone.

"Just look at the handful of mills that produce the stuff and the even fewer scrap processors and brokers who move the bulk of the scrap," Garino continues. "And for scrap people, there's the overlap of having to know not only what the value of the intrinsics are for nickel, chrome and moly--all nonferrous--but one also has to know the value of iron in order to figure the scrap value. Ferrous types could care less about the LME (London Metals Exchange). Not so the stainless boys and gifts who look at the LME settlement price for nickel and the percent of the settlement price mills use in the scrap calculation."

Garino concludes, "Sure it's mostly a steel product by chemistry, but for most commercial purposes, the emphasis is on nonferrous. But, as I noted above, it's `special,' so let's leave it at that."

The author is assistant editor of Recycling Today and can be contacted vid e-mail at [e-mail].