Steel elongation 2

[Mohamed Maher]

Dear all

We have some steel pipes and tubes we bought it from supplier to be s355 grade we make test after receiving the materials and we found some steel sections not achieved the elongation limit..is this can be used? knowing that we design on wind only not seismic as it's not govern
That was the first case
The second case some of items not achieve yield or tensile strength some of them achieve 300 mpa only instead of 355 in the yield and less in the tensile strength as well.
The second case can be checked based on the less limits or should be rejected whatever it's safe or not?

Thanks
Maher

 

[JLNJ]

If you are contractually obligated to meet a material specification, then sub-standard materials cannot be substituted.
If you are building a doghouse on your own property then you get to decide what risks you want to take with your dog's life and wellbeing.

If you are in a part of the world where this type of material is all that is available, then someone with good engineering judgment will need to look at the materials, think about how how their proposed use, determine the magnitude and nature of the allowable and actual stresses, make some guesses as to what ELSE might be wrong with the material, hope that liability is limited, and make some tough decisions as to what can be done with this steel.

 

[kingnero]

Is the cost of the raw materials worth the risk?

 

[JStephen]

The specification(s) for the material should show details of the testing, make sure you are using the same details. (For example, size and orientation of samples, gauge length, averaging of results if appropriate, etc.).
The supplier should have mill test reports available, check if those match up to the material furnished.

 

[EdStainless]

What? How did these even get off of the truck?
If they don't meet the spec then they are not taht material, period.
There are no exceptions or deviation allowed.
Now if it is all that you can get you need to go back and re-check the engineering.
Maybe you will need heavier sections.

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P.E. Metallurgy, consulting work welcomed

 

[JoshPlumSE]

What? How did these even get off of the truck?

In the US, the steel producers are pretty good about knowing these ASTMs and making sure what they produce matches the requirements.

However, there are plenty of cases where material comes from a less reliable foreign producer that might be taking material made to a totally different spec and hoping that it meets this spec. Ideally, you'd have an idea of what material spec they were using. But, sometimes, when working on a job like this, we'd just spec it normally and put in some testing requirements.

I take it this might be "off shore" work like an oil rig or something. Is that correct?

I'd say that this is up to the engineer and the owner. As the engineer you would have to determine if the strength, ductility, and corrosion resistance of the material is sufficient. If so, you could leave it up to the owner. If using that material saves them some money on the project, then they might want to do it.

 

[Mohamed Maher]

Thank you all..for your valuable feed back.

What I'm afraid about that the test was done for each cross section ..only one test ..how can I be sure that there is another with lower value ..
So that give question that how many sample for each section should be taken to make sure from the lowest value of yield

Thanks again

 

[human909]

What? How did these even get off of the truck?

It sounds like in the USA you either have excellent quality control of local mills and have limited imports OR you aren't are standing too far above what is happening on the ground to be aware of the substandard material out there.

I'm in Australia and substandard steel is certainly out there. Australia might be the largest iron ore exporter but we still import some foreign steel! I have heard of enough substandard steel being rejected on delivery and rejected after galvanisation to have little doubt that plenty of stuff slips through.

 

[HTURKAK]

Dear Mohamed Maher ;

Below find my points ;

-When you say Grade S 355 , by definition S stands for structural steel and 355 is Min. yield strength in MPa ( specified for 16 mm thickness ) . It is not reasonable if yield strength 300 mPa only instead of 355 mPa. ( I do not have any idea about your position if you can accept or reject the material , but for simple construction could be acceptable with revising the calculation with available strength )

- Minimum specified elongation limit is one of the requirements for ductility .( EC 3 specify the elongation at failure on a gauge length of 5,65 √ Ao (where A0 is the original cross-sectional area)..

- The supplier SHALL provide the mill certificates ( chemical comp.) and mechanical test certificates for every separate BATCH.
If you want mechanical test , the number of specimens should represent every different batches and sections .

- If you provide more info . regarding the project , applicable codes you may get better responds..

 

[kingnero]

When you say Grade S 355 , by definition S stands for structural steel and 355 is Min. yield strength in MPa ( specified for 16 mm thickness ) . It is not reasonable if yield strength 300 mPa only instead of 355 mPa.

Thanks HTURKAK for bringing this up.
What is the thickness of the part?
It could well be acceptable (fully complying to the standards) if the thickness is > 100 mm. Also Elongation is less for thicker parts. I doubt your pipes are 100 mm thick, but we don't know for sure. I'm just throwing this out here...

 

[Mohamed Maher]

Dear HTURKAK,

Thank you very much for your detaild reply

The design code is the British code what I provide is just example for the yield but really I have one case pipe thickness less than 16 and the yield is 259 it should be s355.

The problem that I'm the structure their and the company already bought the material and fabricate most of it. I check it and its pass.

The problem is for elongation ..elongation not a value which can be checked as yield. It's fail of course in elongation but is it possible to accept if the yield is accepted

Thanks again

 

[kingnero]

259 MPa? That would be low for even a S235.
How the hell did that ever get so far in the supply chain?

 

[Mohamed Maher]

Yes 259 is the yield you may mean s275.. I don't know how the test get this strange value..this os the most strange but there are other better as 304 for thickness 35 mm which should be 345 mpa

 

[EdStainless]

I know the reality is that this happens, and in some parts of the world more than others.
There are two realities that are rarely talked about.
The first is that when you buy material you are really buying the traceability and documentation. The metal itself is only worth the raw material value (or scrap value) unless the documentation is correct.
The other is that every material characteristic (chemistry, mechanical properties, NDT, dimensions, and so on) is part of a statistical distribution. There is range for these and even in good material there is the finite chance that some places in some parts are outside the specification. This is reality and why we have design rules and limits that we follow.

Even when we were dealing with long-time reliable suppliers, we required the paperwork in had prior to delivery. Our system cross checked both heat numbers (and or coil numbers) as well as mechanical properties and chemistries against our records. We were always suspicious when we received a lot of material with a new HT No that had chemistry and properties identical to another. So double checking was involved.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[dhengr]

Mohamed Maher:
Seems to me that you got a bunch of crappy steel from a less than trustworthy/reliable supplier. There are all kinds of steel floating around on the market which does not meet the std. which it was intended to meet. Then it is usually downgraded to a std. which it does meet and sold at that level. There might well be an oversupply of tube and pipe purchased for a job which fell through, and so it is back on the market, maybe without a very good record of its ownership and pedigree. If you cared, your contract should have properly spelled out the stds. you wanted your steel to meet, and the mill testing and the mill certs. and paperwork you expected, and you seem kinda in the dark on this aspect of the whole mess. Then, you should get copies of the codes and materials stds. you are dealing with, so you can really get up to speed on them too.

While it may help you lay out a plan of attack on this problem by coming to E-Tips, for our thoughts and ideas, and there are some good ones above; you really should be talking with your own purchasing people and your suppliers to straighten this out. We can’t do that for you. Be sure to ask them for the proper paperwork on the material they supplied. They likely can’t do that and that may color your trust in them in the future, or force you to clean up your own contract paperwork. Also ask, who is going to pay for testing, how many tests to regain some level of confidence, lost time, extra engineering and project management work that will be required to make this right and make this work. Many things can be redesigned, checked, modified slightly, etc. to make a slightly lesser grade of material work, and it looks like you might be doing a redesign to prove this.

 

[HTURKAK]

Dear Mohamed MAHER ,

I saw you querry addressed to my nick name today. If the only option is the use of existing material , you have still some alternatives for the validation . Below find my opinions ;

- Ductility of the material is very important for seismic, blast and impact loading and i do not have any idea for the subject structures. Elongation at failure can be tested with taking coupon samples ..

- If you are not sure for the threshold value of yield stress , you have test option. You may static test the frames , elements, or structure which BS allows . You may look EN 1993-1-3 Annex A.

My opinion only .. good luck..