How to solve the influence of high temperature on stainless steel torsion springs

High temperature conditions are widely used in industrial manufacturing, automobile engines, metallurgical equipment, thermal energy systems and other applications. In these environments, stainless steel torsion springs face many challenges such as mechanical performance degradation, reduced fatigue life, and increased risk of structural failure. To ensure the reliability of springs in high temperature environments, systematic solutions must be adopted from the aspects of design, material selection, process and protection.

Material selection optimization
Use heat-resistant stainless steel
Traditional SUS304 stainless steel has significant performance degradation above 300°C and is not suitable for long-term high temperature conditions. The following materials with better high temperature performance can be selected:
SUS316: Contains molybdenum, has stronger oxidation resistance and corrosion resistance, suitable for environments below 400°C.
SUS631 (17-7PH): Precipitation hardening stainless steel with excellent high temperature strength and stability.
Inconel X-750: Nickel-based alloy, suitable for extreme high temperatures above 600°C, with anti-creep and anti-stress relaxation properties.
Material state control
Use pre-hardened or semi-hard materials after heat treatment to improve the yield strength under high temperature conditions and reduce the risk of plastic deformation.

Improved structural design
Limited working strain range
Under high temperature environment, control the working angle of the spring within the elastic limit of the material to avoid exceeding the yield point and causing permanent deformation. Reasonably set the safety factor, usually recommended to control it below 50%~60%.
Increase the number of effective turns
By increasing the number of effective turns of the spring, the force per unit turn is shared, the stress concentration per unit angle is reduced, the fatigue life is extended, and the deformation stability under high temperature is enhanced.
Consider thermal expansion compensation
Under the influence of high temperature expansion, the middle diameter, pitch and fit clearance need to be properly reserved during design to avoid interference or mismatch caused by thermal expansion and improve the adaptability of assembly tolerance.

Heat treatment and stress relief process
Prestress relief annealing
Low-temperature aging treatment (such as 300°C × 1~2 hours) after spring forming can significantly reduce residual stress and improve dimensional stability under high temperature.
Precipitation hardening treatment
For 17-7PH materials, higher strength and temperature resistance can be achieved through solution treatment + aging hardening, and torsional elasticity can be kept from rapidly decaying due to high temperature.
Multi-stage heat treatment process control
Develop a phased heat treatment plan based on the use temperature, taking into account strength and plastic toughness, and ensuring that the material structure uniformity and mechanical properties are maintained throughout the temperature range.

Surface treatment and protection measures
Electropolishing treatment
Electropolishing can eliminate surface micro-defects, reduce stress concentration points, improve fatigue resistance, enhance oxidation resistance, and slow down the formation rate of high-temperature oxide layer.
Inorganic coating or ceramic coating
Spray a layer of high-temperature resistant inorganic protective layer or ceramic film on the surface of the spring to form a physical barrier, reduce metal surface reactions at high temperatures, and improve durability.
Passivation treatment
After pickling and passivation, the density and stability of the surface passivation film of the stainless steel spring can be improved, and the oxidation resistance can be maintained for a long time in medium and high temperature corrosion environments.