Round steel link chain making for 30+ years

SHANGHAI CHIGONG INDUSTRIAL CO., LTD

(round steel link chain manufacturer)

What is the Key Considerations of the Flight Bars in Longwall Coal Mining?

1. Material Considerations

1. High-Strength Alloy steel: Typically use high-carbon steel (e.g., 4140, 42CrMo4) or alloy steels (e.g., 30Mn5) for flight bars durability and wear resistance. 

2. Hardness & Toughness: Case hardening (e.g., carburizing) for surface hardness especially flight bar tips (55-60 HRC) with a tough core. Quenching and tempering to balance strength and flexibility. 

3. Abrasion Resistance: Additives like chromium or boron enhance wear resistance against coal/rock abrasion. 

4. Corrosion Resistance: Coatings (e.g., zinc plating) or stainless steel variants in corrosive environments. 

5. Weldability: Low-carbon variants or pre/post-weld heat treatments to prevent brittleness. 

2. Forging Process

1. Method: Closed-die drop forging for grain flow alignment, enhancing structural integrity. Press forging for precision in complex shapes. 

2. Heating: Billets heated to 1100–1200°C (for steel) to ensure malleability. 

3. Post-Forging Treatment: 

4. Normalizing to relieve stress. 

5. Quenching (oil/water) and tempering (300–600°C) for desired hardness. 

6. Machining: CNC machining for precise tolerances (±0.1 mm). 

7. Surface Enhancement: Shot blasting to induce compressive stress and reduce fatigue. 

3. Inspection & Testing

1. Visual & Dimensional Checks: Inspect for cracks/defects; use calipers/CMM for critical dimensions (thickness, hole alignment). 

2. Hardness Testing: Rockwell C scale for surface, Brinell for core. 

3. NDT: Magnetic Particle Inspection (MPI) for surface flaws; Ultrasonic Testing (UT) for internal defects. 

4. Load Testing (if applicable): Apply 1.5x operational load to validate integrity. 

5. Tensile testing: with coupon from same material and forging process and heat-treatment with flight bars, subject to specimen tensile test and/or impact test.

6. Metallurgical Analysis: Microscopy to check grain structure and phase composition. 

7. Certification: Compliance with ISO 9001/14001 or ASTM standards. 

4. Crucial Assembly Points with Mining Chains & Sprockets

1. Alignment: Use laser alignment tools to ensure <0.5 mm/m deviation; misalignment causes uneven sprocket wear. 

2. Tensioning: Optimal round link chain tension (e.g., 1–2% elongation) to prevent slippage or excessive stress. 

3. Lubrication: Apply high-pressure grease to reduce friction and prevent galling. 

4. Sprocket Engagement: Match sprocket tooth profile (e.g., DIN 8187/8188) to mining chain pitch; inspect for wear (>10% tooth thinning requires replacement). 

5. Fastening: Torque bolts to manufacturer specs (e.g., 250–300 Nm for M20 bolts) with thread-locking compounds. 

6. Pre-Assembly Checks: Replace worn sprockets/mining chain links; ensure flight bar spacing matches conveyor design. 

7. Post-Assembly Testing: Run under load (2–4 hours) to check for abnormal vibrations/noise. 

8. Environmental Factors: Seal joints against coal dust/moisture ingress. 

9. Monitoring: Install IoT sensors for real-time tracking of tension, temperature, and wear. 

5. Maintenance & Training

1. Staff Training: Emphasize proper handling, torque procedures, and alignment techniques. 

2. Predictive Maintenance: Regular thermographic scans and vibration analysis to preempt failures. 


Post time: Mar-04-2025

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