Property classes of steel bolts
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.
Notes
- Tensile strength and yield strength are each given twice: as a nominal value and as a minimum. The property class follows from the nominal value, so read across from the nominal value rather than the minimum.
- For property classes 4.8, 5.8 and 6.8 the yield strength is specified as the stress at 0.0048d extension, and the minimum comes out above the nominal value. Class 9.8 is specified only up to 16 mm.
- Heat treatment becomes mandatory at 8.8, which is the same boundary as the change in how yield strength is specified. 4.6 to 6.8 are supplied without heat treatment; 8.8 and above are quenched and tempered.
- Source: JIS B 1051