ISO 898-1 Grade 8.8

ISO 898-1 Grades

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

-