Date: 2025/6/12
Category: Metallurgical encyclopedia terms
Views: 501
Production flexibility: Intermediate stacking buffers are used to decouple hot and cold processes, allowing independent production scheduling for both stages.
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(1)Products:
Rails: 50 kg/m, 60 kg/m, 75 kg/m (standard lengths: 25 m).
I-beams: No. 28–63 (standard lengths: 6–12 m).
Channel steels: No. 28–40 (standard lengths: 6–12 m).
Round/square bars: 120–350 mm diameter/side length.
(2)Production Scale:
Annual capacity: 900,000 tons/year.
(3) Raw Materials:
Rectangular continuous casting (CC) billets:Dimensions: 280×325 mm, 280×380 mm, 380×400 mm.Billet length: 6,000 mm.
Profiled billets:Dimensions: 365×316×110 mm, 365×346×140 mm.Billet length: 5,500 mm.
(4) Roll Pass Design: The roll pass system for rail rolling is illustrated in Figure 2 (e.g., box passes, trapezoidal passes, cap passes).
(5)Rail Rolling Process (60 kg/m Rail Example):
Workpiece: Initial billet: 280×380×6,000 mm. Final length: ~78 m. Weight: 4,850 kg. Temperature Control: Rolling start: 1,200–1,250°C. Final rolling temperature: >950°C.
Pass Sequence:
Blooming Mill (950mm two-high reversible): Box pass I: 2 passes. Box pass II: 2 passes.Trapezoidal pass: 1 pass.Cap passes (two types): 1 pass each.Total: 7 passes.
Intermediate Mills (800mm three-high): Mill I: 3 passes. Mill II: 3 passes.
Finishing Mill (850mm two-high): 1 pass.
Total passes: 14 passes.
Cycle Time: ~110 seconds.
Hourly Production Capacity: ~150 tons/hour.
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(2) Asymmetric Cross-Section:
Asymmetric rolling conditions (top/bottom, left/right) from the first rail pass to the final pass cause shape deviations.
(3) Height and Base Dimension Fluctuations:
Rail height depends on localized natural spread (affected by temperature, reduction, roll surface).
Rail base is influenced by reductions in the final pass and thickness variations from pre-finishing passes.
(4)Inferior Railhead and Base Quality:
Low deformation rates in railhead and base regions result in reduced structural integrity.
(5)Height Variation and Tread Flatness Issues:
Free spread along the rail length creates height inconsistencies, degrading tread flatness.
(6)Limited Workpiece Length:
Cross-arranged mills with low-speed multi-pass rolling cause significant temperature drop, capping maximum rail length at 78m.
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