John Correnti, the former Nucor steel chief executive officer, set up a new company, SteelCorr, to develop a new $700m steel mini-mill in rural Lowndes County, Mississippi. The mill is targeting the automotive industry, particularly for supplying external body panels. It will be the first US mini-mill to produce exposed automotive-grade steel, and the first to produce 72 inch (1,830 mm) wide strip suitable for use on SUVs.

Correnti’s business SteelCorr has a 20% stake in the mill, and the rest is owned by Russian steel firm OAO Severstal, which has the remaining 80%. Severstal’s first foray into North America was in 2003, when it took over the bankrupt Rouge Steel integrated steel mill in Dearborn, Michigan.

Ground was broken on the 1.2m sq ft (110,000 sq m) mini-mill in October 2005, and it is expected to start production late next year. The plant will create 450 jobs, plus an estimated 2,000 jobs by demand from suppliers. Its planned volume is 1.5m tons of hot-rolled, cold-rolled and coated steel per year.

The Severcorr plant has a melt shop, hot mill and cold mill. A different crane contract covers each. P&Hlicensees Morris Material Handling has won the order for cranes for the melt shop, and Konecranes America the $10m (Euro 8.4m) order for 19 cranes for the hot and cold rolling mills.

In the melt shop, one 450 US ton (408t) capacity hoist lifts up a charging bucket that has been filled with scrap metal. Once in place, a second 125 US ton (113t) capacity hook opens the bottom-discharging bucket into the DC electric arc furnace. (Only integrated steel mills have a blast furnace to process iron ores). The crane has a 98ft (30m) lift height.

Depending on its quality, the scrap metal will form the majority, or perhaps slightly less, of the mixture. Conveyors will feed other virgin iron into the furnace continually, says Malla Reddy, project coordinator of the melt shop, hot mill, and power and water supply with Pittsburgh, Pennsylvania-based subcontractor CV Engineering.

Once the metal has melted, it is poured into a ladle, where alloying elements are added, and then picked up by the second Morris 450/125/35 US ton hot-metal crane. About 30% of the ladles are expected to be lifted to a vacuum degasser to remove impurities, Reddy says. In case of a production hold-up, the crane can tip the molten steel back into the furnace before it solidifies in a specialfall-back area.

These cranes are expected to be working in double the normal steel mill temperature, according to Reddy – 120ºF (49ºC) instead of the 60-70°F common in most mills. This temperature difference comes because they are so close to the 2,500ºF (1370ºC) molten metal, he says. “There will be some heat radiation”.

The crane operator can drive the crane inside an insulated, air-conditioned cab, or by remote control.

Although the cranes were originally specified to be CMAA class F cranes, the highest duty classification in the Crane Manufacturers’ Association of America trade association’s system. Instead of supplying four CMAA class F cranes, Morris Material Handling shipped two cranes that meet the more stringent Specification for EOT Cranes For Steel Mill Service from the Association of Iron and Steel Technology (Technical Report no. 6).

“The two heavier P&H designed cranes are able to handle the work of four regular cranes,” says Jeff Breitrick, Morris vice president. “There are more stringent structural and mechanical requirements in the AISE spec 6 including areas such as shaft and bearing sizes,” Breitrick says. The latest version of the AIST’s specification was published in November 2005.

At shipment – scheduled for 2007 – the cranes will weigh 500 US tons each.

Morris is also supplying two 100/20 US ton (90t/18t)capacity maintenance cranes rolling on the same girders. These cranes are designed to CMAA class E, so they have 20 or more rated lifts per hour at the rated load capacity.

After vacuum degassing, the Morris ladle crane travels to the caster and tips the ladle contents into molten metal into a tundish, which feeds into the continuous caster. The caster forms the molten steel into sheet 2-3in thick (55mm) and a width of 36in (914mm) to 74in (1880mm) wide. Then the crane returns the empty ladles.

The hot and cold mills

Once fed through the caster, the steel sheet runs through a single line of five continuous mill stands to press the metal down to a thickness of 3/16 in (5 mm). Another machine coils up the hot steel, still 670ºF (354ºC). At full production rate, the 45 US ton (41t) hot coils will come off the machine at a rate of about five an hour.

They will be lifted on to a transfer conveyor system by one of two 55 US ton-capacity Konecranes Spacemaker cranes. The 99ft (30m) span, 50 ft (15m) lift-height crane is fitted with C-hooks to lift the coils. Most of the Konecranes-supplied Spacemaker cranes have 55 US ton capacity in process duty for lifting coils and 100 US ton capacity for maintenance work.

In the hot mill, a further six Spacemaker cranes will also help maintain the six rolling mills, each of which has two work rolls and two backup rolls. They will also lift tundishes, mill motors and other equipment.

From the hot mill, the coils are taken to a warehouse area for storage, or on to the cold mill, where further surface treatment work takes place. Two process cranes will support the processing of each of the cold rolling mill, pickling line, annealing mill and galvanizing line and cold mill shipping area.

Coil-handling cranes will feature motorised, rotating coil grabs, C-hooks and magnets, according to Konecranes. Several cranes will have magnets on the auxiliary hoists for scrap clean-up. The coil grab supplier had not been announced by press date.

“The finishing stream also requires a tandem cold mill, which is something most mini-mills don’t have and the overhead cranes are a key component,” said LeRoy Prichard, vice president, steel technology and engineering, SeverCorr LLC. Prichard added: “Konecranes employs the most current technology for building and operating cranes, and in the final analysis, they provided us with the most cost-effective package and shortest delivery time.” The total Konecranes order will be delivered between May and July 2006.