Hydraulic drives for converter refining

Hydraulic drives for converter refining
Marginal Column
Content

March 2017

 

Equipment and process control for converter refining from Uvån Hagfors Teknologi AB (UHT) takes advantage of Hägglunds direct drive systems from Rexroth.

The Swedish company UHT is a global supplier of metallurgical processes for steel and ferroalloys, combining groundbreaking know-how and sophisticated process control systems for metal granulation and converter refining. UHT sells two different converter refining processes: a traditional one using argon and a proprietary one which replaces much of the costly argon with steam. Both are supplied with Hägglunds direct drive systems from Rexroth.

No vibration and less wear

“We discovered Hägglunds drives in the late 1990s, and after developing the concept for the specific requirements of converter refining operations we soon decided to make it an integral part of our deliveries,” says Joakim Lundström, project manager at UHT. Up to then the company had only specified electromechanical drives. However, blowing gas into molten materials creates a lot of vibration and high torque. Due to the gaps between the large gear teeth, that vibration puts a lot of stress on electromechanical drives. In a hydraulic system the oil acts as a damper minimizing the vibrations. “Because a Hägglunds drive absorbs the vibrations, it reduces strain on both the converter and the concrete foundation that supports it,” says Lundström.

Moreover, the gearwheel wears at specific areas as the converter is turned to the same positions during refining. “It creates extensive, difficult maintenance work where you have to remove the gears and reposition them to even things out. This work is eliminated with a hydraulic system.”

Shorter process times

Hägglunds drives give UHT converters yet another competitive edge, as Lundström states: “The drives provide full torque from zero, which is very important.” This way the converters can tilt more quickly and accurately. Customers can therefore shorten their process times and minimize metal carry-over during refining.

In addition, the hydraulic drive technology brings out the best in UHT’s main selling point: the Level 2 process control UTCAS. “It makes all the calculations, is always one step ahead and controls exactly when to change the gas mix and add material,” explains Lundström.

Combined with excellent equipment, UTCAS shortens the customer’s process – and that’s where hydraulic drive systems come in. “Hägglunds motors run smoothly and evenly, and they react immediately to whatever commands they’re given. With a Hägglunds drive, the converter always turns to the right position and it’s unbelievably exact. Conventional drives can’t offer the same accuracy.”

No wonder Lundström is very positive about working with Bosch Rexroth. “We’ve had a close relationship with the Hägglunds team in Mellansel, Sweden, for many years and the great thing is that the relationship is still going strong. They always support us, they’re easy to get in contact with and they’re extremely flexible.”