1.Why are cold-rolled coils not applicable?
Railway turnouts are among the most critical, complex, and impact-bearing components of a track system, including switch rails, frogs, the head section of the stock rails, and turnouts. They place extremely high demands on materials:
Extremely high strength and toughness: They need to withstand the enormous concentrated loads, impacts, and fatigue stresses from train wheels. This typically requires medium- to high-carbon steel or alloy steel, and the necessary microstructure (e.g., sorbite) and mechanical properties are achieved through forging, rolling (usually hot rolling), and heat treatment (e.g., quenching and tempering).
Excellent wear resistance: The switch rails and frogs experience extremely severe wear, requiring materials that are highly wear-resistant.
Sufficient thickness and cross-sectional dimensions: Many turnout components are thick and large to ensure rigidity and load-bearing capacity.
2.What are the limitations of cold-rolled coils?
The material is typically low-carbon steel: Cold-rolled coils are mainly used for deep drawing and forming. Their raw materials (such as SPCC and SPCE) have low carbon content, and their strength and hardness are far below the requirements for turnout components.
The process leads to different performance orientations: The cold rolling process mainly improves surface finish, dimensional accuracy, and hardness (work hardening), but sacrifices the material's plasticity and toughness. For turnouts subjected to huge impacts, insufficient toughness is fatal.
Thickness limitations: Cold-rolled coils are relatively thin (commonly within a few millimeters), which cannot meet the thickness requirements of turnout components.
3.What are the correct materials and processes for manufacturing turnout components?
Core load-bearing components: These are made of specialized turnout steel (such as high-manganese steel or bainitic steel), formed by forging or hot rolling, followed by precision machining and heat treatment. For example, high-manganese steel frogs possess extremely high wear resistance and impact resistance.
Structural connecting parts: Such as pads, slide plates, and rail braces, are typically made from hot-rolled steel plates (medium-thick plates) through cutting, drilling, and welding. The strength and toughness of hot-rolled plates are more suitable for this application.
4.What are the possible application scenarios for cold-rolled coils in the railway industry?
Locomotive and rolling stock manufacturing: Used for the body, skin, internal structural components (such as corrugated flooring), and decorative parts of passenger and freight cars. This is due to its good surface quality, ease of painting, and aesthetic appeal.
Electrical cabinets and control boxes: Housings for railway signaling and power supply systems.
Non-load-bearing interior components: Luggage racks, panels, etc., inside the carriages.
Possible "indirect" or "auxiliary" uses of cold-rolled coils in the turnout area:
Protective covers or decorative panels: Used to cover the housing of turnout drive units (switches), and are non-structural components.
Packaging or gaskets: May be used as temporary protective or adjusting shims during transportation or installation, and do not contribute to the final structure.
5.What are the things that are absolutely prohibited?
Do not use ordinary cold-rolled low-carbon steel coils to directly manufacture the core load-bearing components of railway turnouts (switches, frogs, etc.), as this will cause serious safety accidents.