PERFORMANCE OP THE LIQUID-FRICTION BEARINGS OF SUPPORTING ROLLERS IN COLD-ROLLING MILLS

摘要

The rate of cold rolling on broad-strip mills is basically 50-80 percent of the maximum design value, in part on account of the performance of the liquid-friction bearings (LFB) of the supporting rollers. Modern Russian mills employ hydrostatic/hydrodynamic bearings (Fig. 1). Liquid friction in these bearings is such that the working slip surfaces of the bush 1, supported on the conical pin of supporting roller 2 by means of key 3, and motionless lining 4 attached to block 5 are reliably separated by lubricant layer 6, which eliminates the contact of the working surfaces in the most demanding operating conditions. Two circulatory lubricant-supply systems maintain stable lubricant thickness 8 with variable rolling rate: high-pressure hydrostatic system 7 (p_H = 50 MPa) supplying up to 10 m~3/hr; and low-pressure hydrodynamic system 8 (p_L = 0.3 MPa) supplying up to 180 m~3/hr, System 7 supplies high-pressure lubricant to the working gap through channel 9 in lining 4 and lifts the roller in the absence of rotation and in transient mill operation at speeds up to 5 m/sec. System 8 supplies low-pressure lubricant to the working gap through channel 10. It is intended for dynamic LFB lubrication, when the mill operates at speeds above 5 m/sec. Heat liberation through system 8 maintains stable thermal conditions, which facilitates constant lubricant thickness.