What's the of Armoured Steel

[komatias]

Koromatias may you please tell me the difference between composition of the material and grade of the material, i know the composition indicates all the percenteges of carbon, airon, and any other component, but what do you indicate with a grade?

OK so composition just is the mix of materials as you already know. Once you mix them all you can then do lots of different processes to achieve the "Grade". Grade is a very broad term actually. It can encompass many meanings. Post metal processes, material properties, quality, inspection requirements, etc etc.

For example you can heat treat certain metals,(quench, temper) to make them harder. You can cold forge some to to make them stronger.
Quality wise. For example for the same material and heat treat you can accept differing percentage of defects or flaws. There's are usually set out in standards like ISO/Aisi etc. Of course a customer can also set out specifications and requirements and make their own grading system. The supplier would then need to cherry pick the raw material.

So when sellers of various trinkets say aerospace grade titanium it could mean anything. To me it just shows the seller is clueless and probably used the most common grade or whatever was handy. Surgical grade stainless is another one that makes me laugh.

My advice to you if you want to know more about the materials you are working with is to find the suppliers or mills documentation. The datasheets will explain many aspects of the material and grading. If the material is generic and not proprietary you can even look up the corresponding iso or national standard