I'm not positive, I understand your post, but I'll try the best I can.
If the prequalified WPS lists E7018 as the electrode classification, then it is generally acceptable practice to use E7018, E7018-H8, E7018-H8R, E7018-H4, or E7018-H4R.
If the prequalified WPS lists E7018-H8 as the electrode classification, then it is generally acceptable practice to use E7018-H8, E7018-H8R, E7018-H4, or E7018-H4R.
If the prequalified WPS lists E7018-H4 as the electrode classification, then it is acceptable practice to use E7018-H4, or E7018-H4R.
In each case, the amount of diffusible hydrogen is less as you move from E7018 toward E7018-H4 provided the electrodes are properly stored once they are removed from hemetically sealed containers and the maximum exposure times are adhered to. The "R" designation indicates increase moisture resistance once removed from heated electrode storage. The "R" designation permits the welder to have the electrode exposed to ambient conditions for a longer period of time than those eloectrodes without the "R" designation. Depending on the code you're working with, the manufacturer or contractor may have to demonstrate the moisture resisting electrode's ability to maintain low hydrogen characteristics for the time listed on the WPS under various conditions of humidity.
Best regards - Al
By MBSims 
Date 01-04-2009 19:36
Edited 01-04-2009 19:41
I think the question is whether E7018-1-H4R can be considered a prequalified filler metal for Group I and II materials per Table 3.1. I believe the answer is yes, since the "-1" indicates impact testing and E7018-1 also meets the AWS A5.1 requirements for E7018.
You are probably being confused by the "1H4R" after E7018. The "1H4R" is considered an optional supplementary designator to the electrode classification and is not considered part of the electrode classification, so E7018 and E7018-1H4R are considered the same electrode classification. The "1H4R" is just providing additional information that does not change the base electrode classification.
I know some of you are shaking your heads about that statement. Find a copy of A5.1:2004 and look on page 24 if you disagree. Copy is below.
