Jimeng's Research on the Forming Process of Automobile Suspension Springs
I. Introduction
The suspension system is a key component in determining a vehicle's driving performance, safety, and comfort. As the core part of the suspension, the spring plays an important role in buffering, shock absorption, and supporting the vehicle's weight. Among all types, the coil spring is widely used in passenger cars and light commercial vehicles due to its simple structure and linear response characteristics. To ensure that the spring possesses good mechanical properties and a long service life, the forming process of the spring is particularly critical.
This article systematically introduces the material selection, forming methods, heat treatment processes, and key quality control points for automobile suspension springs, aiming to provide a reference for automotive parts manufacturers.
II. Material Selection
Common materials for suspension springs include:
60Si2Mn: High cost performance; suitable for models with medium performance requirements.
55CrSi: High strength and good fatigue resistance; suitable for heavy-duty models.
SUP9/SUP10 (Japanese standards): Good thermal stability; used in high-end models.
New high-strength steels (such as CrV alloy steel): A new direction for weight reduction and improved fatigue life.
The selected material must have a high elastic limit, good fatigue strength, and excellent corrosion resistance.
III. Spring Forming Process
1. Cold Coiling and Hot Coiling
Cold Coiling Process: Suitable for springs with a wire diameter less than 13 mm. This method offers high precision and good surface quality. CNC spring forming machines are used for automated processing.
Hot Coiling Process: Suitable for heavy-duty springs with a wire diameter greater than 13 mm. The steel is heated to 850–950°C before coiling, followed by normalizing.
2. Forming Steps
Feeding: Precisely cut the steel wire according to the designed length.
Winding: Use a CNC spring machine or hot coil forming machine to control diameter, pitch, and number of turns.
Cutting and Shaping: Ensure both ends are parallel or ground to the specified angle.
Heat Treatment (Tempering/Quenching): Improve hardness and toughness by controlling temperature.
Shot Peening: Enhance surface fatigue resistance and extend service life.
Height Sorting and Pre-Pressing: Eliminate residual stress and improve consistency.
Anti-Corrosion Coating: Apply treatments such as phosphating, electrophoresis, or spraying to improve durability.
IV. Key Points of Quality Control
Geometric Dimension Accuracy: Control free height, inner and outer diameters, and number of turns.
Mechanical Properties Testing: Includes load testing, fatigue life testing, and hardness testing.
Metallographic Analysis: Ensure the microstructure meets heat treatment requirements.
Surface Defect Detection: Use non-destructive testing methods such as magnetic particle inspection and eddy current testing to detect cracks.
V. Development Trends
With the ongoing development of lightweight and intelligent vehicles, suspension springs are evolving in the following directions:
Material Lightweighting: Increasing use of high-strength steels and composite materials.
Intelligent Manufacturing: Full CNC control of the forming process to enhance consistency.
Comprehensive Design Optimization: Use of CAE simulation to achieve optimal stress distribution.
Adjustable Suspension Systems: Technologies such as pneumatic springs and magnetorheological dampers are gradually entering the market.
