Tin cans cut costs at Waupaca.

Supplies of good scrap are tightening, but adding recycled steel cans can stretch scrap inventories and create quality castings at less cost.

Back in the fall of 1989, Bill Powell, metallurgical and melt manager for Waupaca Foundry, was riding a winner in an industry that had been faltering for nearly a decade. His company was producing gray and ductile iron castings for some of America's leading manufacturers, sales were moving up, and production was meeting the technical and economic demands of a new, harshly competitive global market.

But Powell sensed a potential problem down the road posed by the then small but persistent demand for good scrap by the new mini steel mills that were springing up across the country. The mini mills were queuing up for the same high-grade scrap that fed foundries like his.

Iron and steel scrap, the lifeblood of an iron foundry, is used to make the infinite varieties of cast metal shapes that are the standard building blocks of consumer, commercial and industrial products worldwide. Increased competition for the best grades of scrap could cause production difficulties for big scrap users like Waupaca.

A master of adaptation, Powell spent the next year investigating the long-term demand for scrap and looking for alternative supplies in the event a scrap crunch turned serious.

The Problem's Genesis

The 1980s gave birth to the mini steel mill, a downsized version of the nation's massive and often inefficient integrated steel mills. Mini mill production was based on low cost and continuous casting of long products such as rebar, wire rod, I-beams and small sections - products that don't need high-quality steel or precise dimensions. The minis were an outgrowth of the opportunities to make these products at low cost in limited-capacity, low-investment plants. Operating costs were trimmed, and production costs and raw materials were closely controlled to maximize profit.

Mini mill operators were getting around quality problems with scrap-based electric arc furnace steels containing residual elements such as Cu, Sn, Ni, Cr, Mo and As. These elements, unable to be removed by the virtual nonexistence of refining in mini mill operations, affected the chemistry of the steel and, ultimately, degraded the mechanical and physical properties of the finished mill products.

Because quality steels cannot be made from 100% scrap, mini mills found it necessary to dilute low-quality scrap with virgin iron to meet demands for better grade steels. That worked but it boosted production costs and was a reluctant option

The mini mill's answer? Buy only scrap with low levels of residual elements - the same scrap grade most iron foundries depend upon. That was the itch that got Powell's early attention. And, indeed, increased competition for dwindling scrap supplies has resulted in bidding contests between the iron foundries and mini mills for a larger share of the finite U.S. supply of high-quality, low-residual scrap.

In his investigation of alternatives to merely slugging it out with mini mills, Powell was intrigued by the possibilities presented by recycled steel cans, long a staple for steel foundries. He reasoned that there were lots of cans, which led him to finding a way to tap into that resource for a consistent supply and at the right price.

Laying the Groundwork

Acting on his hunch, Powell sought information from and was encouraged by Waupaca County's solid waste disposal department, which encouraged the company's melt team to pursue the use of cans. It was this organization that provided the foundry its first supplies of steel cans collected from the county's drop-off centers. The county sustained its logistical support throughout the test period.

Shortly after, Waupaca became the first principal U.S. foundry to seriously investigate the possibilities of using recycled steel cans as a standard part of its charge material mix.

Powell's group swung into action in 1990 and began a series of tests using recycled steel cans as a charge supplement to make class 20, 30 and 35 ductile irons. Those first efforts were successful enough to expand the use of the material, even though the supply of steel cans then available in Wisconsin was limited. Eventually, sufficient suppliers of recycled cans allowed Powell to add gray iron test heats, beginning with class 20 and later adding class 35.

The yearlong Waupaca research proved, among other things, that residual tin in the can scrap improved the tensile strength of ductile irons. The tin content of the material was initially considered a disadvantage, but Waupaca's melt staff found the tin was actually an ally.

Through a succession of melt tests, they established that for low-strength cast iron, tin was effective in eliminating ferrite while increasing hardness and strength. For engineering grades of gray cast iron, tin showed no detrimental effects. Increasing tin in ductile cast iron boosted the pearlite content, and added strength and hardness. Moreover, ductile iron with tin below 0.05% could be fully annealed. For low-alloy (86-55-06) ductile iron, a 0.09% tin content yielded a good pearlitic structure and gray iron containing 0.08-0.09% tin had a completely pearlitic matrix and improved wear resistance.

The recycled steel cans are included now in all production heats and to date, Powell said, the company has used more than 20,000 tons of the material - fully 40% of all recycled cans currently available in Wisconsin. Each cupola charge includes 15% steel cans, determined by tests to be optimal for Waupaca's requirements. The cans are received from dealers either loose or in 50 x 40 x 30 in. maxibales. Two of these bales (1 - 1-1/2 tons) are included in each cupola charge.

Scrap Sourcing

Waupaca gets the bulk of its steel can scrap from recyclers. One stubborn and persistent problem for foundry metallurgists is scrap quality. Incoming steel can shipments require extensive inspection to intercept contaminants such as paper, plastic, glass and scrap iron.

Aluminum also can sneak in from miscellaneous sources in the scrap (license plates, pots and pans, pull tabs and the like) but pinholing from aluminum has not been a problem for the foundry.

Some scrap is purchased directly from can producers who formerly sold all their scrap exclusively to detinners. Scrap from this source is usually cleaner and has a lower aluminum content.

To buy steel can scrap, the foundry is not dealing with its normal scrap dealer network. Instead, it is being serviced mainly by brokers and also supplied directly by municipal recyclers.

Recyclers get their stocks from community collection centers, magnetically separate the steel cans and sell the material as loose, shredded or baled scrap. Buyers at Waupaca found that most recyclers are not used to dealing with iron foundries and need to be educated to the high quality standards essential to supplying the foundry market.

The relentless efforts of Powell and his staff have been working to change the quality of the scrap materials supplied to foundries by steel can recyclers. The Waupaca team tells this quality message to audiences all over the U.S., and encourages a more aggressive stance by foundry buyers to educate and qualify scrap vendors.

Getting the Word Out

Everyone in Powell's test melt team has become an advocate of the potential manufacturing benefits for foundries throughout the country in the use of steel cans as a charge supplement. Powell was a participant in a study underwritten by the Steel Can Recycling Institute (SCRI), the state of Wisconsin, the American Foundrymen's Society, the American Iron & Steel Institute, Waupaca Foundry, J.I. Case Corp., Grede Foundries, Inc. and Miller Compressing Co.

The study, directed by Carl Loper, Jr., material science and engineering professor at the University of Wisconsin-Madison, proved the efficacy of statewide steel can recycling efforts as an environmental measure and as a means of capturing and reusing a valuable raw material resource for foundries.

Study group participant Charlie Shirvani, a metallurgist for J.I. Case, said his foundry's experience in pouring 20-40 grade gray iron using recycled steel cans as a charge supplement paralleled that of Powell.

"J.I. Case began using baled steel cans as a part of our cupola charge makeup two years ago and the economic benefits have been significant," Shirvani said. "For starters, we reduced our tin alloying agent purchases, which cost us $3-4 a lb, by 70%. The overall quality of our castings has been exceptional and our per-casting costs are lower."

Powell was part of the lobby that worked to encourage the state and local communities to begin steel can recovery efforts.

"We have worked with the Wisconsin Department of Natural Resources (DNR), scrap dealers and recyclers on the need to conserve a wasted (steel) resource and pushed for better scrap separation processes to encourage wider reuse," Powell said. "Most of the businesses involved in steel can recycling are not familiar with the needs of iron foundries, and we felt it necessary to explain our potential as a ready-made market able and eager to use this new source of high-grade scrap.

"In 1992, iron and steel foundries spent $1 billion to purchase over 11 million tons of ferrous scrap. There are more than 2 million tons of steel cans available annually, but about 60% are still awaiting reclamation. A national program to recover this valuable resource could relieve substantially the relentless pressures building for a share of prime steel scrap."

Powell noted that, under the 1990 Wisconsin Landfill Act, no cans will be accepted at any landfill after 1995. This progressive legislation not only saves landfill costs, but actually generates capital in the total steel can recovery scheme. He said that, according to the SCRI, Americans use 100 million steel cans a day. These cans, all made from high-grade steel, are an ideal material for reuse.

Powell urged similar recycling action by other states as an environmentally and economically sound course worthy of local, state and national interest.