Effect of temperature on fastener strength
Steel boltsISO 898-1 (JIS B 1051)In property class X.Y, X times 100 is the tensile strength, and that multiplied by Y/10 is the yield strength.Stainless steel fastenersISO 3506-1 (JIS B 1054-1)The rule differs from steel: the class number multiplied by 10 is the minimum tensile strength.Non-ferrous fastenersISO 8839 (JIS B 1057)Copper alloys and aluminium alloys. These are set by material group and alloy number, not by property class.Effect of temperatureJIS B 1054-1 Annex FMechanical properties away from room temperature. Only stainless steel has figures per temperature in the standard.
Stainless steel (elevated temperature)
Stainless steel (low temperature)
Notes
- The elevated-temperature figures are ratios to the room-temperature yield strength, and apply only to property classes 70 and 80. The standard does not say how far the tensile strength falls.
- The low-temperature figures cover austenitic grades only. Martensitic and ferritic grades are not covered by the standard.
- No temperature-by-temperature figures are given for steel bolts. Annex B of JIS B 1051 says only three things: that no harmful effect is known up to 150 °C; that above 150 °C and up to 300 °C the functional properties should be confirmed by test; and that below −50 °C and above 300 °C expert advice should be sought.
- What falls at elevated temperature is lower yield point, 0.2 % proof strength, stress at 0.0048d extension, and tensile strength. Property classes 4.8, 5.8 and 6.8, which are finished by work hardening, are held to be more susceptible to relaxation than quenched and tempered products.
- JIS has no table of values by property class. If you come across such a table, check whether it really comes from the standard.
- JIS B 1057 specifies the mechanical properties of non-ferrous fasteners at room temperature and says nothing about other temperatures.
- Sources: JIS B 1051 Annex B, JIS B 1054-1 Annex F, JIS B 1057