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www.ferrometal.fiBreaking elongation A5 (%)
Breaking elongation indicates machined test rod’s elongation in percents:
A5 = (LU-LO) / LO X 100%, where
d0 = test rod’s / screw’s diameter before the test
LO = defined length LO = 5 X d0
LU = length after breaking
d
0
L
0
= 5 X d
0
Hardness and it’s testing
In general, hardness is defined as the material’s ability to resist testing equipment’s penetration under surface. Three widely used systems for hardness testing are Brinell HB
(ISO 6506), Vickers HV (ISO 6507) and Rockwell A, B, C (ISO 6508).
Mechanical properties for screws in class 5.6…12.9:
Mechanical property
Property class
5.6
8.8
10.9
12.9
≤ M16* > M16*
Tensile strength Rm (N/mm2)**
Nominal
500
800
1000
1200
min.
500
800
830
1040
1220
Yield strength Re (N/mm2)**
Nominal
300
-
-
-
-
min.
300
-
-
-
-
0,2% -limit Rp0,2 (N/mm2)**
Nominal
-
640
640
900
1080
min.
-
640
660
940
1100
Yield strength Re or
0,2%- limit Rp0,2
in high temperatures (N/mm2)
+ 100°C 270
590
875
1020
+ 200°C 230
540
790
925
+ 250°C 215
510
745
875
+ 300°C 195
480
705
825
Breaking elongation A5 (%)**
min.
20
12
9
8
Vickers-hardness F≤ 98N (HV)**
min...max 155...220 250...320 255...335 320...380 385...435
*** 250
-
-
-
-
Brinell-hardness F = 30D2 (HB)**
min...max 147...209 238...304 242...318 304...361 366...414
*** 238
-
-
-
-
Rockwell-hardness HR**
HRB min...max 79…95
-
-
-
-
*** 99,5
-
-
-
-
HRC min...max
-
22…32 23…34 32…39 39…44
Impact strength KV (J)**
min.
25
30
30
20
15
* For structural bolts the limit is M12
** Properties in temperature + 20°C
*** Hardness value at the end of the bolt