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【概要描述】The Role of Mandrel Assist Rolls in Second-Hand Hot Rolling Mill Coilers​ Mandrel assist rolls are critical components in second-hand hot rolling mill coilers, supporting the mandrel during coil formation and ensuring tight, uniform coil winding. Their performance directly impacts coil handling safety, storage efficiency, and downstream uncoiling operations.​ Coil Tightness Control​ In second-hand hot rolling mill coilers, mandrel assist rolls apply adjustable pressure (0.5-2 MPa) to the outer layer of the forming coil, ensuring uniform coil density (typically 7.2-7.6 g/cm³ for carbon steel). Tight, consistent coils prevent layer slippage during storage or transportation—reducing coil deformation by 80-90% compared to loose coils. For thick-gauge strips (≥12mm), the assist rolls’ ability to maintain pressure across the coil width (1000-2200mm) prevents "bell-mouthing" (coil edge deformation), which can cause jams during downstream uncoiling.​ Mandrel Load Reduction​ Assist rolls share 30-40% of the coil’s weight during winding, reducing stress on the mandrel in second-hand hot rolling mills. This extends mandrel life by 25-35% (from 20,000 to 25,000-27,000 coils) and minimizes the risk of mandrel bending—a costly repair that can take 3-5 days. For second-hand mills with worn mandrels (radial runout ≤0.1mm), properly adjusted assist rolls can compensate for minor mandrel defects, maintaining acceptable coil quality until mandrel replacement.​ Winding Speed Synchronization​ Modern mandrel assist rolls in refurbished second-hand hot rolling mill coilers feature variable speed drives that synchronize with the mandrel’s rotational speed (up to 300 rpm). This synchronization prevents strip slippage between the assist rolls and the coil, ensuring smooth winding even at maximum line speeds (180-220m/min for thin strips). Older assist roll systems with fixed speeds often require speed reductions of 15-20% to avoid slippage, lowering overall mill throughput.​ Maintenance Guidelines​ To maintain optimal performance of mandrel assist rolls in second-hand hot rolling mill coilers:​ Inspect roll surface wear weekly; replace rolls if surface roughness exceeds Ra 2μm or if indentations exceed 0.5mm.​ Check roll pressure daily using load cells; adjust if pressure deviates by more than 0.2 MPa from the setpoint.​ Lubricate roll bearings monthly with high-temperature grease (operating temperature up to 200°C) to prevent seizure.​ Align assist rolls quarterly using a laser alignment tool to ensure parallelism with the mandrel (deviation ≤0.05mm).​ For second-hand hot rolling mills processing stainless steel or high-alloy steel strips, upgrading to assist rolls with heat-resistant coatings (e.g., chrome carbide) can improve wear resistance by 50-60%, extending roll life and reducing maintenance frequency.​ For more information, please pay attention to the website of Jinyujie Mechanical and Electrical Used Pipe Mill Supplier：www.usedpipemill.com