material specification substitution of S355 for A572 grade 50 question

[stillfan]

My international supplier is substituting S355 for A572 grade 50 that was originally specified. I am running through the properties and noticed that the S355 has higher Mn, Si, Cu and N values at 1.6%, .55max,.55max,.012max (respectively) compared to 1.35%, .40,0,0.


I believe this is a standard substitution but I wanted to double check.

If this is ok, at what point should a structural engineer actually start to question if a material substitute is acceptable?

 

[metengr]

stillfan;
There is no such concept as a "standard substitution", when it comes to metals or other materials. You should be evaluating the original material specification, which lists the applicable Grade or Type of steel and compare with the substitute material specification, Grade or Type. As part of this engineering review you need to evaluate specified mechanical properties and use at design service temperature.

 

[SJones]

S355 is the yield strength. What are the grade designators that come after it?

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[stillfan]

I did compare the two and found the differences as noted above. My question as to rather the chemical composition of the S355 having a Mn content of nearly .25% more than the A572 is still in question. Also the Si,Cu and N values of the S355 are higher than the A572.

I am not sure what the Cu,Si,Mn and N composition does to the steel. As a structural engineer the Carbon content and CVN results are always the main concern but that is within an acceptable margins.

 

[TVP]

stillfan,

Steve Jones is correct, there should be some additional characters after the S355, e.g. S355MC according to BS EN 10149-2. The chemical composition differences are relatively minor between the two standards within the context of conventional structural engineering.

 

[stillfan]

Yeah, there are additional characters but they all have relatively the same chemical composition and they didn't give me these characters so I was just assuming worst case scenario where there are larger discrepancies btwn the two materials.

Thank you all.

 

[EuroWeld]

Additional characters could be JR, J0 u/i J6 meaning charpy impact tested with minimum value as specified. Normally you can expect character G following with an number telling the material if (fully) killed. Also the S355 material can be produced by different fabrication (rolling) proceses (M-TM-N) that all have other properties.

 

[rmw]

So to me the question boils down to why did you specify SA572 Gr 50 in the first place, and does this substitute material meet those requirements?

rmw

 

[rmw]

Sorry, I guess I should have finished my thought before hitting the 'submit' button.

I regularly specify A572-50 (ignore the "S" above - just habit) for a very specific reason and the requirement that drives me to A572-50 would be the very first one I would check on any material submitted for substitution. If it met that, then I'd look at the rest.

I'm finished now.

rmw

 

[Mr168]

Just something to consider outside of the design criteria - arbitrarily substituting materials can often create nightmares for the fabricator who has procedures and specifications to follow that are based on the more common ASTM or SA spec materials.