bolt head markings ? 1

[Gerry45]

The flanges on the tower sections in a large horizontal axis wind turbine are joined by a hundred or so large bolts.
The bolt heads are all marked with three things:-

a)makers names (Nedloy and Friedberg)
b) the nos. 10.9
c) and the letters HV

I believe '10.9' is basically the strength but can anyone explain this more acccurately please...

Also, what does the 'HV' mean ?

Any comments would be appreciated.

 

[boo1]

ISO R898 Class 10.9 (metric)
Alloy Steel Martensite,Quenched & Tempered
Bolts, Screws, Studs
Proof 120,000 psi 830 MPa
Yield 130,000 psi
Tenisle 150,000 psi 1040 MPa

HV
hexagon high-strength structural bolts, with thread sizes from M12 to M36

 

[ksnar]

The first digit of 10.9 gives the tensile value and the second digit the yield value as a % of the tensile: tensile 1000 N/mm2 and yield is 90% of tensile thus 900 N/mm2.

 

[CoryPad]

ksnar,

You describe the how the code is used to determine the "nominal" stress values, but the specification minimum values can be different. boo1 shows the correct values (according to ISO 898-1): 940 MPa minimum yield, 1040 MPa minimum tensile.

 

[ksnar]

Thanks for the correction CoryPad, I took an old DIN description based on stress in kp/mm2.
ksnar.