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Four/Six-Hi Reversing Cold Rolling Mill: Field Notes, Specs, and What Buyers Are Really Asking If you’ve spent any time in a coil yard (and I have, more than I planned), you know the heartbeat of a modern strip line is the reversing rolling mill . To be honest, the category hasn’t stood still—controls got smarter, pass schedules leaner, and the bar for flatness keeps moving. YWLX’s Four/Six-Hi unit we looked at in Beijing feels like that quiet workhorse many customers say they want—less drama, more throughput. What it is (and where it’s built) Product: Four/Six-Hi Reversing Cold Rolling Mill by YWLX. Origin: No.1518, LAR Valley Int’l, Guangwai Avenue, Xicheng District, Beijing, 100055. The Six-Hi variant is the one operators in China keep talking about for silicon steel and stainless—surprisingly forgiving, even on tricky coils. Quick spec snapshot Parameter Typical Four-Hi Typical Six-Hi Strip width ≈900–1150 mm 900/1150/1380 mm Entry thickness 3.0 mm (SPHC) 3.0 mm (SPHC); 0.63 mm (Si steel) Exit thickness ≈0.25–0.20 mm 0.20 mm (SPHC, 6 passes, no inter-anneal); 0.26 mm (Si steel, 2–3 passes) Passes 4–6 2–6 depending on grade Max speed ≈800 m/min (real-world may vary) ≈1000 m/min (grade-dependent) Controls AGC, work roll bend Hydraulic AGC, AFC, work/intermediate roll bending & shifting Process flow (how teams actually run it) Materials: carbon steel (SPHC), oriented/non-oriented silicon steel, stainless strip. Methods: multi-pass reversing rolling mill schedule with tension control, roll-bite lubrication (emulsion), online thickness/flatness feedback. Testing: thickness per ISO 9445; for electrical steel, magnetic properties per IEC 60404 series; surface finish Ra typically ≈0.3–0.5 µm after skin-pass, if applied. Many lines report availability around 95–97% with smart roll campaigns; work-roll life per grind ≈6–20 hours depending on grade and roughness. Service life: stand frames 20+ years with planned overhauls; bearings often 5–10 years; shape meters and coolant systems depend on upkeep—no surprises there. Industries: automotive and appliance sheet, transformer cores (GO), EV motor laminations (NO), kitchenware stainless—quite a mix. Why Six-Hi matters The Six-Hi reversing rolling mill gives you extra shape control for silicon steel and stainless—intermediate roll shifting helps tame edge wave and center buckle. In fact, one Beijing service center shared that flatness improved to single-digit I-units on their acceptance runs (sample data, process-dependent). Thickness tolerance routinely hit ≤±0.004–0.006 mm on 0.25 mm strip under steady conditions—again, your emulsion and roll crown make or break this. Vendor landscape (short version) Vendor Strengths Typical lead time Notes YWLX (China) Cost-performance, China support, Six-Hi for Si/stainless ≈8–12 months Good fit for regional steel service centers SMS group High-end automation, global references ≈12–18 months Premium pricing tier (indicative) Primetals Advanced shape control, digital twins ≈12–18 months Strong SI ecosystem Danieli Integrated plant solutions ≈10–16 months Wide reference base Lead times and pricing are indicative; real-world use may vary with scope and automation. Customization checklist Widths: 900/1150/1380 mm; coil weight 15–30 t. Automation: hydraulic AGC/AFC, roll bending, shape meter, data historian, remote diagnostics. Grade packages: silicon steel (GO/NO), stainless (e.g., 304/430), low-carbon deep-draw. Safety/Compliance: CE options; QMS typically ISO 9001 certified. Case notes from the floor A North China line running the Six-Hi reversing rolling mill reported SPHC reduction 3.0 → 0.20 mm in six passes without in-process annealing; silicon steel 0.63 → 0.26 mm in 2–3 passes. Operators liked the pass predictability; maintenance flagged coolant cleanliness as the make-or-break variable (no shock there). Authoritative standards and references ISO 9445-1: Cold‑rolled narrow steel strip — Tolerances ASTM A109/A109M: Steel, Strip, Carbon, Cold‑Rolled IEC 60404‑8‑7: Grain‑oriented electrical steel — Sheets and strip EN 10130: Cold‑rolled low carbon steel flat products ISO 9001: Quality management systems — Requirements