How do temperature extremes affect the performance of steel fasteners?

Product overview：

Brittle Fracture Risk: At temperatures below the ductile-to-brittle transition temperature (DBTT), steel fasteners become highly susceptible to brittle fracture. This is a catastrophic failure mode characterized by little or no plastic deformation prior to failure. To mitigate this risk, fasteners intended for low-temperature applications should be selected based on their low-temperature toughness properties, such as Charpy impact energy values.

Reduced Ductility: The ductility of steel decreases significantly at low temperatures, making the material less able to absorb energy and deform plastically before failing. This can lead to premature failure under cyclic loading or impact conditions. To address this, fasteners can be designed with increased cross-sectional area or selected from materials with inherently higher low-temperature ductility.

Thermal Stress: Rapid temperature changes can induce thermal stresses within the fastener, which can exacerbate the effects of low temperature on material properties. Proper insulation and temperature control measures should be implemented to minimize thermal gradients and stresses.

Strength Degradation: As temperature increases, the yield strength and ultimate tensile strength of steel fasteners typically decrease. This reduction in strength can compromise the fastener's ability to withstand loads and maintain structural integrity. To compensate, fasteners for high-temperature applications should be selected based on their elevated temperature strength properties.

Creep and Relaxation: At high temperatures, steel fasteners can experience creep and relaxation, leading to gradual deformation and loss of preload. This can significantly reduce the effectiveness of the fastener in maintaining joint integrity. To mitigate creep and relaxation, fasteners can be designed with larger cross-sections or selected from materials with improved creep resistance.

Oxidation and Corrosion: Elevated temperatures accelerate the oxidation and corrosion of steel, leading to material degradation and potential failure. Proper surface treatments, such as galvanizing or applying corrosion-resistant coatings, can help extend the service life of fasteners in high-temperature environments.

Thermal Expansion: High temperatures cause steel to expand, which can lead to dimensional changes and potential issues with fit and function. Designers must account for thermal expansion when selecting fasteners and specifying installation procedures.

Material Selection: Carefully select fasteners based on the specific temperature range and environmental conditions they will encounter. Consider factors such as low-temperature toughness, elevated temperature strength, creep resistance, and corrosion resistance.

Design Considerations: Design fasteners with appropriate cross-sectional areas and geometries to accommodate the effects of temperature extremes. Consider using preload indicators or locking mechanisms to maintain preload in high-temperature applications.

Automotive Steel

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