steel grade and the carbon rate limit

[khaledsoltane]

hi,
We use the A283GRC steel grade for our floatting roof construction, and the carbon rate maximum limit is 0.24%, now how determinate the minimum limit, and the standard that explains it, the article that defines.

thankx

 

[bobjustbob]

I don't have a copy of 1.04 to look up the standard but, in general terms. The carbon content is set by the standard, in this case ASTM A283. That will list the chemical and mechanical properties. It will also reference the relevant inspection standards. If the standard just lists a maximum carbon content, the minimum is left up to the manufacturer unless there is an intervening customer specification.

Bob

 

[khaledsoltane]

hi bob,

the minimum content you talk about and left to the customer how in your opinion the customer can act on it, or if I use the A283 GRC sheet for my floating roof for crude oil, how can I set the limits of the maximum carbon 0.24% which is limited by the but the mini standard? on what basis I accept 0.15% and I refuse 0.14%, there is surely a standard to follow.
thank you.

 

[bobjustbob]

Are you asking how to decide what your internal lower limit should be? If so, that is not something anyone here can help you out with. You would set that lower limit depending on some variable in your usage of the product or experience. If you have empirical data that shows that when this product meets the ASTM standard but has a carbon content of 0.14% is put in your service it fails prematurely, you would create an internal standard that lists a minimum carbon content. In your purchase order to your supplier, you would include the ASTM standard and your internal standard. It is then up to the supplier to meet the requirements of the purchase order.

If there is no reason to restrict the carbon content, then don't. All it will do is raise the cost of your material.

Bob

 

[weldstan]

You accept 0.15% because the material meets all mechanical properties. The normal average range of A383C is about 0.12 to 0.15%. This material spec was written long ago when low carbon ferro-alloys were not normally used and the carbon contents tended to be higher.

 

[khaledsoltane]

Thankx bob it's very logical what you say, so we will think about user experience, we will see with the history and search in old technical files and see the repercussions of this carbon content to another, so we will move on to study the evolution of the degradation of the said grade with respect to carbon.
please what's or give me a idea about the 1.04 stadandard, i looked on internet but i couldn't inderstand.

weldstan,

I neglected the mechanical properties of the nuance I will try to associate the mechanical data, and see where I can arrive, your logic is very real in addition to that of bob. thanks again

I am going to get started on this subject and I'll hear from you about the results.

 

[bobjustbob]

Why are you questioning the carbon content when you are not concerned about the mechanical properties. Carbon content can give you an idea of what a steel can do but its the combination of the chemistry and how it is processed that sets the mechanical properties. It is the mechanical properties that indicate how it will perform in service.

ASTM standards are compiled into volumes. ASTM A283 is in the volume 1.04. The volume tends to contain standards for similar materials and the testing methods for those materials. You can also purchase the standard on its own. If you are going to be purchasing material to any standard, you need to have that standard and keep updated on the changes to that standard. ASTM publishes a new set each year, you don't always need the new set but if the standards that you are ordering to change you need to know.

Bob

 

[khaledsoltane]

the carbon content concerns me as much as the mechanical characteristics, except in these grades A283C (max 0.24%) - A283B (max 17%) -A238D (max 0.27%) the 3 grades have identical chemical properties in Mn, P, S and different in Carbon with simple difference.

You are right about the mechanical characteristics, I said neglect in a sense or I wanted to know the minimum limit following the data cited above which are very close, the result became clear to me, because in such cases we touch directly to mechanical specifications and it will all depend on what we build.

 

[bobjustbob]

I am sure that the manufacturer has a lower limit because he knows his process and how to achieve the mechanical properties. Unless you will be performing an operation such as welding or heat treating where the carbon content, as well as the rest of the chemistry can have an effect the mechanical properties should be your prime concern. It seems as if you are trying to solve a problem that does not exist.

Bob

 

[weldstan]

The higher C limits are there to provide the steelmaker the ability to add carbon to meet the mechanical requirements as product thickness increases. For thin plate like your tank roof, low carbon contents are the norm. For thicker plate (> 1'') the carbon content can be increased and this was the cheapest way to meet the mechanicals.

 

[Dhurjati Sen]

As the C content decreases, the price of ASTM A 283 increases e.g. price of Grade A > Grade B and so on.

If there is a requirement for lower C content, go for Grade B or A, in that order.

No manufacturer would give you a Grade A plate at the cost of Grade C.

DHURJATI SEN

 

[khaledsoltane]

THANKS FOR ALL