SF-I、SF-II metro brake block

1. Applicable Standard & Product Positioning Scope

This series of brake blocks are customized matching parts for Siemens SF bogies, designed and tested per group standard T/CAMET 04004.10 Urban Rail Transit Vehicle Brake System Part 10: Composite Brake Blocks, conforming to original Siemens drawing and braking performance requirements, divided into two sub-grades: SF-I light-load and SF-II heavy-duty.

1. SF-I (Basic Light-Load Grade) For early Siemens SF30 low-floor light rail and original 6-car Type B metro; maximum axle load 14t, maximum operating speed 70km/h; suitable for short-distance gentle routes without long continuous downhill heavy-load braking.

2. SF-II (Upgraded Standard Heavy-Duty Grade) For SF40 / SF100 standard metro bogies and mainstream 6-car Type B metro; maximum axle load 16t, maximum operating speed 80km/h; adaptable to full operating scenarios including viaducts, underground tunnels and regular slopes within 40‰ gradient. Unified basic application limits:

· Brake mounting structure: Special double-buckle brake shoe holder for Siemens SF bogies, single-side tread brake unit;

· Matching Wheel: φ840mm steel tread wheel with R420 tread radian;

· Ambient temperature tolerance: -25℃ ~ +45℃, stable service in high-humidity tunnels and open-air rain & snow lines;

· Interchange logic: Fully consistent with original Siemens brake block installation dimensions, no modification to brake unit required for replacement.

2. Structural & Friction Material Composition

(1) Asbestos-Free Semi-Metallic Friction Body

Both SF-I and SF-II adopt modified phenolic resin semi-metallic composite matrix, reinforced with aramid fiber and ultra-fine steel fiber, mixed with flake graphite long-acting solid lubricant and antimony sulfide friction modifiers. Free of asbestos and excessive heavy metals, no toxic irritating flue gas under long-term high-temperature braking.

· SF-I Friction Body: Lightweight basic formula with lower filler density for light load & low-frequency start-stop service. Solid curved integrated structure with passivated edges to absorb braking impact and eliminate squeal noise during low-speed station arrival.

· SF-II Friction Body: Reinforced heavy-duty wear-resistant formula with increased steel fiber content, comprehensively upgraded high temperature resistance, impact resistance and anti-fading performance, resisting chipping and cracking under frequent heavy braking of high-passenger-flow lines. Higher precision curved contact surface achieves uniform wheel contact under heavy high-pressure braking, drastically reducing wheel tread thermal scuffing risks. Both grades feature stable dynamic friction coefficient 0.25~0.35 with overall fluctuation ≤±16% and no obvious cold fading at low temperature. Max continuous working temperature reaches 315℃ for SF-I and 330℃ for SF-II.

(2) Thickened Special Steel Back Base

· SF-I: Integrally stamped from 4.5mm Q235 cold-rolled low-carbon steel plate with internal trapezoidal anchor grooves, basic bonding strength meeting light-load requirements, surface treated with phosphating anti-rust coating.

· SF-II: Upgraded 5.5mm thickened Q235 cold-rolled steel plate with deepened & widened anchor grooves for deeper embedding of friction compound, delivering higher bonding shear strength to bear heavy braking pressure and superior anti-bending fatigue performance. Both models adopt unified symmetrical double-buckle positioning structure exclusive to Siemens at the bottom, perfectly clamping into SF-series brake shoe holders for convenient maintenance replacement. The steel back is equipped with integrated wear warning boss: continuous abnormal metal friction noise occurs when residual friction thickness reaches safety limit of 10mm to remind mandatory full block replacement and avoid wheel tread scratch damage.

3. Core Product Advantages

1. Perfect Compatibility with Original Factory Dimensions: Double-buckle structure fully matches Siemens SF30/SF40/SF100 bogies, zero modification during replacement, compatible with multiple domestic metro lines adopting Siemens technology platforms;

2. Graded Matching for Light & Heavy Load Scenarios: SF-I lightweight low-cost solution for old light rail vehicles; SF-II reinforced wear & heat resistant grade for mainstream 80km/h high-capacity Type B metro;

3. Silent Wheel-Friendly Performance: Semi-metallic fiber buffer structure absorbs braking resonance, cutting braking noise by 10~17dB(A) versus cast iron blocks and reducing wheel tread wear by over 52%, extending wheel reprofiling intervals;

4. Wide-Temperature Stability & Moisture Resistance: Minimal friction performance fluctuation from -25℃ extreme cold to 330℃ high temperature; phosphated steel back resists high humidity and salt spray corrosion in tunnels, resisting delamination and degumming under long-term service;

5. Eco-Friendly Safety Compliance: Asbestos-free formula with biodegradable braking dust complying with underground tunnel environmental control standards; passed full UIC-compatible track circuit compatibility test without signal interference.

4. Application Scope, Maintenance & Storage Rules

1. Mandatory Replacement Standard: Full brake block replacement required when residual friction thickness ≤10mm; grinding, splicing and secondary reuse are strictly prohibited;

2. Running-In Rule: Avoid frequent emergency braking within the first 300km after installation for uniform friction surface fitting; full-load long downhill braking forbidden during running-in period for heavy-duty SF-II grade;

3. Storage Condition: Store in dry & ventilated warehouse, stacking height ≤10 layers, avoid sunlight exposure and rain soaking, shelf life 18 months;

4. Inspection Cycle: Check friction layer cracking, partial uneven wear and chipping defects every 25,000 km, simultaneously inspect wheel tread condition.