In addition to the core components mentioned above, such as drive shafts, brake lines, and battery pack frames, cold-rolled round tubes are used in a variety of other applications within the automotive industry, covering modules such as the powertrain, chassis, body, and auxiliary systems. The key reasons for this use are their high precision, high strength, and excellent adaptability.
1. Powertrain: Adaptable to High-Temperature, High-Pressure Operating Conditions
The powertrain requires extremely high sealing and temperature resistance from pipes. Cold-rolled round tubes, with their uniform wall thickness and dense material, can reliably withstand the harsh environments surrounding engines and motors.
Engine Cooling System Pipes
Purpose: Transport coolant to cool the engine block and cylinder head, preventing overheating.
Specifications: Commonly used cold-rolled round tubes have an outer diameter of 8-12mm and a wall thickness of 1.0-1.5mm (mostly made of Q235 or galvanized steel). The inner wall roughness should be Ra ≤ 1.6μm, ensuring smooth coolant flow without impurities clogging the waterways. Advantages: Compared to conventional welded pipes, cold-rolled pipes' seamless construction prevents coolant leakage (engine cooling system pressure is typically 0.15-0.25 MPa) and offer improved temperature resistance (withstanding coolant temperatures of 120-150°C).
Turbocharger System Piping
Purpose: Transports high-temperature, high-pressure air (intake) or exhaust gases (partial oil return pipes) from the turbocharger, requiring them to withstand high temperatures and vibration.
Specifications: Cold-rolled stainless steel pipes (such as 304) with an outer diameter of 15-25 mm and a wall thickness of 1.5-2.0 mm are commonly used for the intake side, capable of withstanding temperatures of 300-400°C. Cold-rolled low-carbon steel pipes (such as 1020) with an outer diameter of 10-15 mm and a wall thickness of 1.2-1.5 mm are used for the oil return side to ensure smooth oil return. Advantages: Cold-rolled tubes offer high dimensional accuracy, enabling precise connection to turbocharger interfaces, reducing the risk of air leaks. They also offer strong resistance to vibration fatigue (can pass vibration tests exceeding 100,000 cycles).
New Energy Vehicle Motor Water Pipes
Purpose: Located around the motor stator, they deliver coolant to cool the motor (new energy vehicle motors can operate at temperatures of 150-200°C).
Specifications: Thin-walled cold-rolled round tubes (mostly made of aluminum alloy or galvanized steel) with an outer diameter of 6-10mm and a wall thickness of 0.8-1.2mm are commonly used. They are lightweight and offer high heat dissipation efficiency, while the smooth, burr-free interior prevents scratches on seals.
Advantages: The thin-wall design allows for a close fit within the motor housing, saving space. The uniform wall thickness of the cold-rolled tubes (with a deviation of ≤5%) ensures consistent cooling across all sections, preventing localized overheating of the motor.
II. Chassis System: Extended Applications of Support, Steering, and Braking
In addition to suspension links and brake lines, the chassis system also features numerous auxiliary components that rely on the load-bearing capacity and impact resistance of cold-rolled round tubes to ensure driving stability. Steering System Power Assist Oil Hose
Purpose: Transports hydraulic oil or electronic hydraulic fluid to provide power assistance to the steering system, reducing steering wheel operation effort.
Specifications: Hydraulic power assistance systems typically use cold-rolled round tubes (made of 20# steel) with an outer diameter of 10-14mm and a wall thickness of 1.5-2.0mm, capable of withstanding pressures of up to 8-12MPa. Electronic power assistance systems use thin-walled tubes with an outer diameter of 8-12mm and a wall thickness of 1.2-1.5mm, resulting in lighter weight and faster response.
Advantages: The smooth inner wall of the cold-rolled tube (Ra ≤ 1.6μm) reduces hydraulic oil flow resistance and prevents power assistance lag. The weld-free construction prevents high-pressure oil leakage, enhancing steering system safety.
Chassis Stabilizer Bar Sleeve
Purpose: Sleeves fit over the outside of the stabilizer bar to reduce friction between the stabilizer bar and the vehicle frame, while also protecting the stabilizer bar from mud and sand erosion. (The stabilizer bar is responsible for suppressing vehicle roll and is a key component in chassis rollover resistance.) Specifications: Cold-rolled round tubes (Q235 steel) with an outer diameter of 25-35mm and a wall thickness of 2.0-3.0mm are commonly used. The inner diameter must precisely match the outer diameter of the stabilizer bar (clearance ≤0.5mm) to prevent unusual noise during driving.
Advantages: Cold-rolled tubes offer high straightness (deviation ≤1mm per meter), ensuring precise alignment with the chassis frame and eliminating any additional stress after installation. Their smooth surface reduces friction and wear on the stabilizer bar.
Trailer Hook Sleeve
Purpose: Serves as the mounting base for the trailer hook, withstanding the tensile or impact forces of towing (the rated pulling force for a family car trailer hook is typically 1.5-2.5 tons).
Specifications: Thick-walled cold-rolled round tubes (Q275 high-strength steel) with an outer diameter of 30-40mm and a wall thickness of 3.0-4.0mm are commonly used. Yield strength ≥345MPa ensures no deformation or breakage during towing. Advantages: Thick-wall design improves bearing capacity, and the cold rolling process ensures uniform overall strength of the pipe without local weak points, thus avoiding cracking of the casing due to stress concentration during towing.