ISO 898-1 Grade 8.8
Mechanical properties of fasteners made of carbon steel and alloy steel Grade 8.8
The Grade 8.8 Bolts, screws, and studs with specified property classes — coarse thread and fine pitch thread
The ISO 898-1:2013 Grade 8.8 specification covers carbon steel bolts and studs ranging from M-6 to M-64 diameter. We use high carbon steel material and high alloy steel raw materials to achieve the required properties in grade 8.8 standard. There are three popular grades in this standard, 8.8, 10.9 and 12.9 which denote material hardness strength and their respective mechanical properties.
ISO 898-1:2013 Grade 8.8
| 8.8 |  | Hex bolts, screws, stud bolts, double ended studs, full thread rods, full threaded studs |
ISO 898-1:2013 grade 8.8 Chemical properties
Property class | Material and heat treatment | Chemical composition limit (cast analysis, %)a | Tempering temperature ⁰C Min. | ||||
C | P | S | Bb | ||||
min. | max. | max. | max. | max. | |||
8.8f | Carbon steel with additives (e.g. Boron or Mn or Cr) quenched and tempered | 0,15e | 0,40 | 0,025 | 0,025 | 0,003 | 425 |
Carbon steel quenched and tempered | 0,25 | 0,55 | 0,025 | 0,025 | |||
Alloy steel quenched and temperedg | 0,20 | 0,55 | 0,025 | 0,025 | |||
ISO 898-1:2013 grade 8.8 Mechanical properties
Mechanical or physical property | Tensile strength, Rm, MPa | Stress at 0,2 % non-proportional elongation, Rp0,2, MPa | Stress under proof load, Spf, MPa | Proof strength ratioSp,nom/ReL,min | Percentage elongation after fracture for machined test pieces, A, % | Percentage reduction of area after fracture for machined test pieces, Z, % | Height of non-decarburized thread zone, E, mm | Depth of complete decarburization in the thread, G, mm | Reduction of hardness after retempering, HV | Impact strength, KVij, J | |||
nom.c | min. | nom.c | min. | nom. | min. | min. | min. | max. | max. | min. | |||
8.8 | d≤ 16 mma | 800 | 800 | 640 | 640 | 580 | 0,91 | 12 | 52 | 1/2 H1 | 0,015 | 20 | 27 |
d> 16 mmb | 830 | 640 | 660 | 600 | 0,91 | 0,016 | 21 | 27 | |||||
ISO 898-1:2013 grade 8.8 Recommended hardness
Mechanical or physical property | Vickers hardness, HV F ≥98 N | Brinell hardness, HBW F = 30 D2 | Rockwell hardness, HRC | Surface hardness, HV 0,3 | ||||
min. | max. | min. | max. | min. | max. | max. | ||
8.8 | D ≤ 16 mma | 250 | 320 | 245 | 316 | 22 | 32 | - |
D > 16 mmb | 255 | 335 | 250 | 331 | 23 | 34 | - | |
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