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The open-die forge press effortlessly shapes ingots up to four meters thick.
Photo: Taiyuan Heavy Machinery Group

Speed, power and precision

70 strokes per minute. 80 meganewtons of power. Exact to the millimeter. This is how a gigantic forge shapes hot steel in China.


China is far and away the world’s largest steel maker. The Middle Kingdom turned out about 683 million tons – and thus 45 percent – of all the steel produced in 2011. These quantities have to be worked, of course, and one way to do so is with a forge press. A massive gripper arm – the manipulator – guides the incandescent steel while the forge transforms it into the desired form. The Taiyuan Heavy Machinery Group has engineered and built a press like this. Applying 80 meganewtons of power, it can shape steel in ingots up to four meters thick.

Bold decision

The hydraulics for this modern forging press have to be powerful and fast – and control must be precise. The specifications: 70 strokes per minute at a tolerance of just one millimeter. In addition, Taiyuan has demanding expectations in regard to automation, energy efficiency and noise output. “The challenge was tremendous,” recalls Xiangdong Kang, project manager at Bosch Rexroth in China. “We first have to accelerate the ram downward and then instantly reverse its motion, raising it again.” It was with this project that Rexroth’s engineers in China made their debut in the field of mega-size forge presses. They worked closely with the Technical Laboratory for Presses in Lohr, Germany.

Planning, engineering and simulation – using the MOSIHS software, a program developed by Rexroth for modular simulation of hydraulic systems – are of tremendous importance for projects like this. They ensure that assembly and commissioning will go off without a hitch. But even the most careful planning cannot guarantee that there will be no surprises. “We found on site that the system produced noise and vibrations. That called for a bold decision. We redesigned all the piping and ran simulations once again,” Kang reports. Lingling Wang, the woman who heads up the technical department for forge presses at Taiyuan, adds: “The time pressures throughout the project were tremendous. But when I look back at the work, I am very grateful for the meticulous collaboration.” The redesign made it possible to optimize the configuration of the piping and the valve blocks and to put together a tailor-made system.

Graceful punch

Now several type A4 pumps move ten thousand liters of high-pressure hydraulic fluid into the system – each minute. Adjustable-displacement, axial-piston pumps with pressure regulation and proportional volume adjustment make for high energy efficiency. The entire system is under the command of an HNC Motion Control System. Kang notes: “The machinery control directs the filler and regulator valves. That results in smooth interaction between the press and the manipulator. It’s all very harmonious, but it sure packs a punch.”