Cases

New Bee Transmission: Energy-saving and Production-increasing Case of Bearing Improvement in a Steel Plant's Four-roll Strip Mill

Background

The main cause of bearing damage in a hot-rolled strip four-roll mill at a steel plant in Shandong was excessive radial and axial loads during operation. Misalignment between the work roll and backup roll axes led to axial sliding friction, uneven radial load distribution, and frequent overloads, resulting in bearing failures. To address this, improvements were made in bearing design and mill frame stability to enhance precision and extend bearing life.

Solutions

Mill Frame Stability: Regular inspections and maintenance of the mill frame windows, with deviations over 0.8mm corrected by replacing liners. Annual overhauls improved frame accuracy.

Bearing Housing and Roll Assembly: Semi-annual checks of bearing housing dimensions and symmetry, with non-compliant housings repaired or replaced. Standardized roll assembly procedures were implemented.

Roll Grinding Precision: Roll roundness and ovality were controlled within 0.03mm.

Operational Improvements: Adjusted incoming material dimensions, optimized rolling centerline alignment, and balanced rolling forces across stands.

Bearing Upgrades: The work roll bearings (2097938) were modified to better handle axial loads, and the backup roll bearings (6890250) were upgraded to 6890260 with carburized steel material.

Key Figures:

Bearing Failure Rate Reduction: 38% (5.7 → 3.5 units/10,000 tons)

Critical Tolerances: Frame window deviation ≤0.8mm, roll ovality ≤0.03mm

Bearing Upgrades: 2097938 (axial load optimization), 6890250 → 6890260 (material upgrade)

Feedback

After implementing these measures, the online bearing failure rate dropped from 5.7 to 3.5 units per 10,000 tons, a 38% reduction, significantly improving efficiency and reducing downtime.