How does high temperature affect the performance of stainless steel torsion springs

As an important energy storage and release element, stainless steel torsion springs are widely used in aerospace, automotive electronics, medical equipment, industrial machinery and other industries. When used under high temperature conditions, their performance is significantly different from that in normal temperature environments. High temperature not only changes the physical properties of the material itself, but also affects the geometric stability and service life of the spring.

Effect of high temperature on the mechanical properties of materials
Decrease in yield strength
High temperature will significantly reduce the yield strength of stainless steel. Taking SUS304 as an example, the yield strength at room temperature (25°C) is about 205 MPa. When the temperature rises to 300°C, its yield strength may drop to below 140 MPa. This means that the spring is more likely to undergo plastic deformation under the same load and cannot effectively store energy and rebound.
Reduced elastic modulus
The elastic modulus represents the rigidity of the material. Under high temperature conditions, the thermal vibration of the metal lattice is enhanced and the elastic modulus is reduced, resulting in a decrease in the torque output of the spring per unit angular displacement. For applications that require high-precision torque control, such as automatic assembly mechanisms or precision sensing systems, this performance degradation will directly affect product functions.
Creep phenomenon is enhanced
In high temperature environment, stainless steel will creep under long-term continuous stress conditions. Creep causes the torsion angle to gradually increase without increasing external force, causing structural positioning errors or even permanent deformation. Especially in working conditions where continuous load and working temperature exist at the same time, such as industrial furnace door springs and turbine components, creep poses a serious threat to system reliability.

Effect of high temperature on structural stability
Thermal expansion effect
Stainless steel has a large thermal expansion coefficient (about 16~17×10⁻⁶/K) at high temperatures. The length, diameter and coil gap of the torsion spring will change at high temperatures, affecting the assembly accuracy and working clearance, and may cause jamming, wear or failure.
Structural relaxation problem
Stainless steel has a significant stress relaxation effect at high temperatures. Even if the initial torque is set reasonably, as the use time increases, the internal stress of the material gradually releases, resulting in a decrease in the output torque of the spring. This relaxation is particularly significant above 250°C, which will cause the torsion spring to lose its expected rotation ability, and is particularly unsuitable for static holding structures.
Surface oxidation and corrosion risk
The surface of stainless steel at high temperature is more susceptible to oxidation. Even austenitic materials, such as SUS316 or SUS304, may form significant oxide scale above 400°C, reducing its corrosion resistance and surface strength, thereby accelerating the formation of microcracks and affecting fatigue performance.

Effect of high temperature on fatigue life
Fatigue limit decreases
High temperature intensifies the microscopic slip behavior of the material, making the lattice structure more susceptible to fatigue fracture. Under the same cyclic load, the fatigue life of stainless steel springs at high temperature is much lower than that at room temperature. For every 50°C increase in temperature, the fatigue life may decrease by more than 20%.
Thermal fatigue phenomenon
In an environment with multiple alternating hot and cold conditions, stainless steel springs are prone to thermal fatigue cracking. Repeated thermal expansion and contraction form stress concentration areas at the root, bend or contact surface of the spring, which eventually triggers the expansion of microcracks and leads to fracture failure.
Increased crack growth rate
High temperature causes microcracks to grow faster, especially in springs with initial defects or irregular processing marks. The crack growth rate at high temperature can increase by 2 to 5 times, greatly shortening the service life.