NELA's Aluminum Hot Reversing Twin-Coiler Finishing Rolling Mill in Heilongjiang, China

North East Light Alloy's (NELA) wanted to produce over 200,000 tonnes per year of hot-rolled coil, to the highest quality standards specified in the aerospace and automotive industries.
Commissioning a new dedicated mill line, the finishing mill was required to take a transfer bar between 10 and 36 mm thick, up to 1850 mm wide, and roll it in one to three passes to a finished strip thickness between 2.0 and 18 mm, where the incoming temperature could be as low as 300 °C.
All major alloys, including aerospace and automotive grades and clad strip, fall within the scope of this mill, and our customer wanted high-quality stock without compromising production levels.

Harbin’s long and icy winters required robustness in the design. At Primetals Technologies, we know that process know-how underpins plant design, because this is what assures both metallurgical quality and operational efficiency. Once the design concept was known and agreed, the collaborative process of realizing it began.

With a single common plan of reaching the quickest and most secure return, Primetals Technologies supplied all basic design, all Level 2 automation, and all aspects of the reversing twin-coiler finishing mill, while the customer supplied the slab reheat furnaces, roughing mill, and heavy shear (including Level 1 automation) and the transfer tables.

The new mill includes a state-of-the-art, fully automated hot rolling line, consisting of slab reheat furnaces, a reversing roughing mill with edger and heavy shear, transfer tables, light shear, a twin-coiler reversing finishing mill with work roll scratch brushes and ISV roll cooling, an edge trimmer, and coil handling systems. Added features such as media systems to support both mills, high-pressure and auxiliary hydraulics, oil and oil-air lubrication, an emulsion roll cooling system, cooling water and compressed air, fume extraction, plus measuring devices and instrumentation, ensured a comprehensive solution for our customer.

The mill fully achieved its tough targets: rolling aerospace sheet at 4 mm thick, rolling industrial coils down to 2 mm, and producing achievable automated schedules for every aluminum alloy group from 1xxx to 8xxx. The mill can maintain coiling temperature within a range of ±10% and thickness within ±0.7%, and will trim the edges of the strip to produce a neat coil with a cold width tolerance of -0/+3 mm.

Plant Data

• Feedstock: Cast and scalped slabs, aluminum AA 1000, 2000, 3000, 4000, 5000, 6000, 7000, and 8000 series alloys
• Slab width: 900–1850 mm
• Slab thickness: 400–620 mm
• Slab length: 3500–7200 mm
• Finished coil thickness: 2.0–18.0 mm
• Maximum coil weight: 21,300 kg
• Maximum coil density: 11.51 kg/mm

Equipment (Mill) Data

• Mill type: 4-high reversing twin-coiler mill
• Work roll dimensions: 750/700 mm dia × 2100 mm barrel width
• Back-up roll dimensions: 1500/1400 mm dia × 2000 mm barrel width
• Nominal production capacity: 210,000 tonnes per year
• Max. rolling load: 3500 tonnes
• Maximum mill speed: 360 m/min in high gear
• Main drive power: 6000 kW synchronous motor with SINAMICS SM150 voltage source converter