Surface Treatment and Durability Assurance of Track Components
What are the common surface treatments for fish bolts and their applicable scenarios?
Hot-dip galvanizing is the mainstream method, providing uniform zinc coating and strong corrosion resistance for wet, rainy outdoor tracks. Phosphating + painting enhances rust resistance at lower cost than galvanizing, suitable for dry inland ordinary railways. Blackening is simple but only for dry, non-corrosive indoor/warehouse tracks. Stainless steel bolts need no treatment for coastal salt spray areas but cost more. High-speed railway fish bolts often use galvanizing + passivation for better weather resistance.
Why do elastic bars mostly use shot peening + oiling surface treatment?
Shot peening removes surface scale and creates residual compressive stress, improving fatigue resistance critical for repeatedly stressed elastic bars. Subsequent oiling forms a protective film, isolating air and moisture to prevent rust. Shot peening uses 0.8-1.2mm steel shots to achieve Ra 1.6-3.2μm surface roughness. Oil must be mineral-based with -30℃~80℃ stability. This process extends elastic bar service life to over 15 years, surpassing ordinary painting.
How does pressing plate surface treatment balance wear resistance and cost?
Ordinary railways use low-cost blackening for basic protection, despite average wear resistance. Fast railways adopt phosphating, forming phosphate films with better wear resistance and moderate cost. High-speed railways use galvanizing (≥80μm zinc layer) for strong wear resistance but higher cost. Heavy-haul railways use zinc-aluminum alloy coatings, combining zinc's cathodic protection and aluminum's wear resistance, with high cost but long life. Electrophoretic coating is used for municipal projects requiring good appearance.
What is the relationship between rail spike surface treatment and pull-out resistance?
Poor surface treatment causes rust, reducing sleeper engagement and pull-out resistance. Threaded spikes use galvanizing; zinc fills thread gaps to increase friction and pull-out force. Hook spikes use blackening, ensuring tight wooden sleeper fit despite limited rust resistance. High-speed spiral spikes use zinc infiltration, with non-peeling zinc layers for over 100kN pull-out force. Treated spikes undergo 500-hour salt spray tests to ensure no red rust and stable pull-out resistance.
What upgraded surface treatment solutions apply to track components in extreme environments?
Coastal salt spray areas use hot-dip galvanizing + sealing coating to block chloride ions. Desert area components add UV-resistant coatings to prevent aging. Frigid regions use zinc-nickel alloy coatings with good low-temperature toughness to avoid cold brittleness. Chemical-polluted areas use PTFE coatings for excellent chemical resistance. Extreme environment treatments must pass 1000-hour salt spray and 500-hour UV aging tests for durability.