H2 Max 4 PPM

For purpose steel plate will be specified usually by the intended use....Hydrogen content and other components will determine the suitability of the steel you are using.... High hydrogen contents are generally considered as detrimental due to the risk of flakes, bubbles and breakouts during casting as well as hydrogen embrittlement.... Hydrogen can nonetheless be removed by degassing of the steel.....

http://www.astm.org/Standards/steel-standards.html

http://www.saimm.co.za/Conferences/Slags2004/105_Dekkers.pdf

For your purpose there is no difference.

H2 max 4, ppm means it is virtually hydrogen free.

It's a language thing, you can use it.

Well I think there are uses that require less than 4 ppm(parts per million).... What is the intended use of this steel..? ...and what are the specifications?....4 ppm is the stated hydrogen content and vacuum degassing is a process for removing hydrogen(or other gasses), usually from molten steel....Vacuum degassing is used to set the ppm at the specified level....

I understand degassing. I used to specify materials for satellites.

The OP is clueless, so providing detailed technical information is a waste of our time.

The information will not add any value to the final product. It will be up to the supplier to decode OP's requirement, not the forum.

Yeah that second part wasn't really aimed at you but more of an exploratory explanation to the op...I am quite sure you know all about material specifications....cheers

And I am sure that you are only trying to help the OP.