Proof Load Stress and Tensile Yield Strength in 10.9 Steel 1

[bulldogwld]

Hello, we are trying to get a steel mill to quote 10.9 grade steel.

From what we found on the internet (attached .PDF), there is a question from our mill about "Proof Load Stress" and "Tensile Yield Strength". The mill is saying: ..."proof load stress is the British nomenclature for yield strength". If they are the same, then the info attached saying Proof Load Stress MPa 830 does not agree with Tensile Yield Strength Min MPa 940.

Can someone help me better understand this?

 

[CoryPad]

Property class 10.9 is a designation according to ISO 898-1 (or SAE J1199 or ASTM F 568M, they are all essentially identical). Yield stress is 0.2 % offset. Proof stress is nominally 90 % of the yield stress, and technically it is a stress applied to the fastener that causes no permanent deformation. Here is an excerpt from ISO 898-1:

To meet the requirements of the proof load test, the length of the bolt, screw or stud after loading shall be the same as before loading within a tolerance of ± 12,5 mm allowed for measurement error.

Your mill source is wrong.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[TVP]

The previous response should have said micrometers not millimeters.

I'm a little confused why a steel mill would be having difficulty quoting a grade of steel for a property class 10.9 fastener. Typical grades are 10B21 for small fasteners, 4037 or 4140 medium sizes, and heavily alloyed grades for really large sizes (greater than M36).

 

[CoryPad]

Thanks for catching that error TVP. I forgot about formatting the [μ].

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.