Property variation in metals

[yidux]

Can anyone give an estimate of what the expected property variation would be in metal components of the same type and design. For example, if 1000 steel beams are manufactured using the same process with the same grade steel and the same heat treatment from the same batch of raw material, I would assume the tensile strength to vary by less than 5% between each beam. Is this assumption realistic??

Any web links discussing this would be great.

Thanks for any help.

 

[IFRs]

Look at the ASTM material specification - it lists variations for each property. Sometimes there is a minimum but no maximum, etc. Often these days materials are "dual certified" and meet more than one code.

 

[IFRs]

Also look at the AISC structural code.

 

[EdStainless]

I doubt that they would be that close.
In structurals you might find 5% from one part of the shape to another.
The other part of this issue is what the real properties are. If the spec requires 40ksi yield and 60ksi tensile as minimums, will you get 45/70 or 55/90? For a lot of grades most actual strenghts are way above the minimums.

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[BillPSU]

Most low carbon steels are manufactured to a minimum yield strength such as A36, or A572 class 50. These materials will vary in strength even within the mill run. When converting A656 coil to A572 testing is performed at the head and tail of the coil to verify strengths.

 

[metengr]

Can anyone give an estimate of what the expected property variation would be in metal components of the same type and design. For example, if 1000 steel beams are manufactured using the same process with the same grade steel and the same heat treatment from the same batch of raw material,...

The one variable in your quote above that really influences properties, given all other factors as being equal (especially heat treatment), is the "same batch of raw material". I can tell you that having seen submittals for new material for adoption by ASME Section II Part D, 5% variation in properties is reasonable for material that is heat treated under similar conditions and was supplied from a master heat. This is the reason why Appendix 5 of ASME B&PV Code, Section II requires three different heats of new material to assure a range of mechanical properties for similar heat treatment conditions before endorsing the material for use.

 

[yidux]

Thanks Everyone. The reason I ask is that I am looking at a range of "identical" bolts and they are displaying tensile strengths of between 375 and 525MPa, a variation that seems a bit excessive.

Thanks for your help.

 

[CoryPad]

Identical by specification?

Are these steel bolts? If so, this is on the low side of available properties. It is very possible that a manufacturer might supply higher strength bolts because it was cheaper to use some leftover higer strength bolts than to make a few lower strength ones.

Regards,

Cory

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