The Role of Descaling Brush Rolls in Second-Hand Hot Rolling Mills’ Strip Surface Quality

Descaling brush rolls are underappreciated yet critical components in second-hand hot rolling mills, complementing high-pressure water descaling systems to remove residual oxide scale (scale) from hot-rolled strips. Second-hand hot rolling mills often suffer from inefficient scale removal (e.g., scale residues in strip recesses) due to worn water nozzles or reduced water pressure, leading to scale pits and surface defects. Brush rolls address this gap, removing 95% of residual scale and ensuring hot-rolled strips meet surface quality standards (e.g., API 5L for pipeline steel), while reducing roll wear by 20-25%.

1. Residual Scale Removal for Flawless Strip SurfacesHigh-pressure water descaling (15-30 MPa) in second-hand hot rolling mills effectively removes loose scale but often leaves tightly adherent scale (e.g., Fe₃O₄ layers) in strip edges or embossed areas. The descaling brush rolls—made of high-temperature-resistant nylon (operating up to 800°C) with steel wire bristles (diameter 0.2mm)—scrub the strip surface at 500-800 rpm, dislodging residual scale. For example, when rolling Q355B structural steel (used in bridge construction), brush rolls reduce scale-related surface defects from 12% (water-only descaling) to <2%. This is critical for hot-rolled strips destined for galvanizing, as residual scale causes zinc adhesion failures (rejection rates up to 30% without brush roll descaling).

2. Roll Protection & LongevityResidual scale acts as an abrasive between work rolls and strips in second-hand hot rolling mills, accelerating roll wear (e.g., 0.1mm wear per 1,000 tons of steel processed). By removing scale before the strip enters the rolling stands, brush rolls reduce roll wear to 0.07-0.08mm per 1,000 tons, extending roll life from 1,500 tons to 2,000 tons per set. For a second-hand hot rolling mill with a 5,000kW main drive, this reduces roll change frequency by 25%, cutting downtime by 100-150 hours annually and saving $10,000-$15,000 in roll replacement costs.

3. Adaptability to High-Temperature & High-Speed OperationsSecond-hand hot rolling mills often operate at variable speeds (50-180m/min) and process diverse materials (carbon steel, low-alloy steel). The descaling brush rolls’ variable-speed drive (synchronized with strip speed) ensures consistent scrubbing pressure (0.3-0.5 MPa) across all operating conditions. The brush rolls’ steel wire bristles also resist deformation at high temperatures (up to 800°C), maintaining effectiveness even for thick slabs (20-50mm) with high heat retention. For second-hand mills processing API X70 pipeline steel (rolled at 1100-1200°C), this adaptability ensures scale removal efficiency remains above 90% regardless of production parameters.

Practical Maintenance Strategies

• Inspect brush bristle wear weekly; replace rolls when bristle length reduces by more than 30% (from 50mm to <35mm).
• Clean brush rolls daily to remove accumulated scale; use compressed air (0.6 MPa) to dislodge trapped particles.
• Adjust brush pressure monthly based on strip thickness: 0.3 MPa for thin strips (2-5mm), 0.5 MPa for thick slabs (20-50mm).

For second-hand hot rolling mills aiming to supply high-quality hot-rolled strips to construction, automotive, or energy industries, descaling brush rolls are a low-cost, high-impact upgrade that resolves long-standing surface quality issues and reduces operational costs.

For more information, please pay attention to the website of Jinyujie Mechanical and Electrical Used Pipe Mill Supplier：www.usedpipemill.com