Mill rolls represent one of the most reliable downstream markets for forged products, a steady demand for large, high-value orders, as long as the market for rolled steel and aluminum remains stable. Forgers, like all manufacturers, need to exploit opportunities to introduce new, value-added products to their range of capabilities.
But, finishing mill rolls demands precision and expertise, and for the very highly engineered rolls needed for cold rolling and finishing higher-grade materials (cold-rolled carbon and stainless steels, aluminum), there is a need for specialty grinding machinery.
In June, Heinrich Georg GmbH Maschinenfabrik introduced a new roll-grinding machine — ultragrind 700 R — to an audience of customers and potential customers at its workshops in Kreuztal, Germany. The new machine is designed for center lengths of 5.000 mm, grinding diameters of up to 700 mm, and roll weights up to 10 mt. Importantly, it is a fully automated operation – relieving potential operators of some cost requirements for additional man-power costs and process expertise.
More important is its high-tech grinding capabilities in conventional and cubic boron nitride (CBN) grinding. CBN materials are increasingly in demand for grinding technologies on critical materials, but working with such materials raises the process control standards for the production systems. Georg claims the ultragrind 700 R incorporates such control capabilities, and others. Also, its very solid construction and innovative, and meticulous measuring standards, allow the new machine to achieve high precision, with the shortest possible set-up and machining cycles.
A number of design details contribute to excellent grinding results, short handling and machining cycles, as well as a long service life for the machine. For example: the headstock that can be displaced as a whole, with fixed main axis and displaceable counter part; the hydrostatic bearing of the grinding spindle and the grinding carriage; the very precise U-axis with a resolution of 0.01 µm; the U1-axis for exact horizontal roll alignment; and fully integrated measuring and control platforms.
Dozens of roll grinding experts from the world’s steel and aluminum producers, as well roll manufacturers and engineering firms, watched the machine in "live" operation prior to its delivery to Baosteel, China’s (and the world’s) largest steelmaker.
Georg first demonstrated the grinding of a work roll in the conventional way, and later in the cBN technology mode. It also displayed a HSS work roll of a hot rolling mill with CVC profile and a profile height of 1.85 mm that had been ground before with a CBN disc.
During the demo visitors were able to appreciate the quality of surface conditions on the finished rolls, “neither comma nor feed marks could be detected,” according to the developer. They also noted the absence of vibration or swing motions with the machine, in both the conventional and to the CBN grinding processes.