- #1
Juanda
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- TL;DR Summary
- Screws classified by ISO 3506-1 seem to show better mechanical properties than the parent material. I don't understand it.
To mods: I didn't know whether to post it here in Mech Engineering or in Materials Engineering. Feel free to move the thread if necessary. Also, let me know if posting pictures from the ISO may be a problem.
Stainless steel screws are denoted by their grade and property class (mechanical strength) in ISO 3506-1.
So the material itself is not typically defined. The chemical composition is defined which is technically enough but information about the alloy is harder to find.
For example, you may know you're buying an A4-80 screw but you don't initially know the alloy.
From other sources (or by matching the chemical composition), you may find that an A4 screw corresponds to an AISI 316 or stainless steel 18/10.
Link for A2 (AISI 304) vs A4 (AISI 316) stainless steel
And here lies my question about the material. An A4-80 seems to have greater mechanical properties than what an AISI 316 has to offer.
Here are the mechanical properties defined by ISO 3506-1.
So those properties of an A4-80 are considerably above what's available in an AISI 316.
How is that possible? It can't be that it's simply work hardened because that moves the yield point to the right but it shouldn't increase the ultimate tensile strength.
What am I missing?
This is the only instance I could find where the ultimate tensile strength comes near what is defined for the screws.
Still, I don't know how it's possible.
Stainless steel screws are denoted by their grade and property class (mechanical strength) in ISO 3506-1.
So the material itself is not typically defined. The chemical composition is defined which is technically enough but information about the alloy is harder to find.
For example, you may know you're buying an A4-80 screw but you don't initially know the alloy.
From other sources (or by matching the chemical composition), you may find that an A4 screw corresponds to an AISI 316 or stainless steel 18/10.
Link for A2 (AISI 304) vs A4 (AISI 316) stainless steel
A4 Stainless is often referred to as 316 or 18/10 stainless. As in A2 above, the numbers 18/10 refer to the chromium and nickel content- 18% chromium and 10% nickel.
A4 grade then is also austenitic, non-magnetic and suitable for all the situations as A2 BUT has the added advantage of being suitable for marine solutions. Often called Marine Grade stainless steel. The molybdenum increases the corrosion resistance to withstand attack from many industrial chemicals and solvents and of course, chlorides. Used in the production of inks, photographic chemicals, surgical implants, and the marine environment.
And here lies my question about the material. An A4-80 seems to have greater mechanical properties than what an AISI 316 has to offer.
Here are the mechanical properties defined by ISO 3506-1.
So those properties of an A4-80 are considerably above what's available in an AISI 316.
How is that possible? It can't be that it's simply work hardened because that moves the yield point to the right but it shouldn't increase the ultimate tensile strength.
What am I missing?
This is the only instance I could find where the ultimate tensile strength comes near what is defined for the screws.
Still, I don't know how it's possible.