Mechanical Strength Properties

"What is the difference between ST and tensile strength"

Based on the evidence presented, there is no difference.

Thank you for your response.

Then why is terminology of ST and tensile strength differently experessd?

Mechnical strength values are decreasing when temperature are increasing.

Thanks,

I think I don't understand what you are asking.

Metals get softer as the temperature rises. At the melting point, they cease to have any tensile strength at all.

"ST(Specified Minimum Tensile Strength)" is a property, specified in the material standard (established at the mill).

"tensile strength at temperature" is an additional property not specified in the material standard, probably part of a fabrication standard.

Same difference for the specified yield strengths.

P.S. That's the first time that I've used "same difference" where it actually makes sense.

Thank you for your explanation , passingtongreen. Then what do you mean by "same difference"? In tensile strength at temperature this" temperature" means design temperature or room temperature or the same temperture? Thanks

Minimum Yield Strength is part of the material standard specification, yield strength at temperature is not, it is probably part of the fabrication specification.

In short, the properties "at temperature" are not part of the material standard but are additional tests for that particular equipment manufacture standard.

OK. this is final question for you.

What is the difference between one-third of ST and one- third of tensile strength at temperature and what does temperature here mean specifically?

This is excerpt from ASME B31.3 to find basic allowable stress value.

Thanks,

The difference is the temperature.

When I was designing a big furnace where the steel was going to reach a temperature well above ambient, I used a reduced design strength in order to maintain the same factor of safety, in your case, the SF is 3.0.

Check this link for the effect of heat on steel.

From the link, see how quickly the strength dissipates with temperature:

Did you mean to ask for the difference of Yield Stength and Tensile Strength?

This was covered before in CR4. just use the search engine and plenty of hits.

Mind there will be lots of links to Wikipedia and other infromation sources!

ST = tensile strength at some standard temperature such as 70°F or 20°C.
"tensile strength at temperature" = strength at some other given temperature.

If the other given temperature is higher than standard, the tensile strength is less;
if the other given temperature lower, the tensile strength is more, but the notch toughness is less and may need to be considered additionally.

The criterion requires you to assume the "worst case."

Thank you, Tornado.

That was my point to make it sure.

We are using CSA piping material not listed in ASME B31.3 or ASME SEC. II Part D.

So in order to calculate the wall thickeness we need to know basic allowable stress value at temperaure as per ASME B31.3 Para 302.3.2 (d) (1), (2).

Clients usually provide YS and TS in their specifications at room tempetaure and design temperature but certain client does not.

In that case we don't know YS and TS at temperature without testing report.

Other than this do you know how to find values of YS and TS at temperature?

Thank you.

Since you work with ASME how about getting the notch by looking at what else is there?

I know its tedious, but its the only way to know for sure!

http://www.astm.org/Standards/E21.htm

http://www.ssina.com/composition/temperature.html

more hits here.

Ofcourse you mentioned the important properties of Fracture / Notch / Charpy

-these values are going down when temperature is below 0 Celsius

(worse when 0 Fahrenheit...)

-Also Minimum Ultimate Tensile Stress or Yield Point - are meaningless (0 for both..)

So PO Design needs to cover also low temperatures too !!