hello, gentlemen,
some welding material such as ER70-6,ER70-G,EH14, there are no A-No consistent with such materials, however, i am wondering can I specify the limited content in PQR&WPS, for example,
ER70S-6:
A-No. :1 (Mn:max.1.6,Si:max.1.0)
and while purcahsing welding material, specify the special chemical requirements in purchase specification, does it ok?

Yes specify, instead of the A No. analysis in accordance with ER70-6, EH14, but not ER70-G which, by definition has not a coded chem. analysis: in this case go with the brand name.
mauro

then, if we specify ER70-G in WPS, for A No.,just mark "/" or N/A,is it acceptable?

Suffix "G" means that a specific chem. anal. is not required. Therefore G should be referenced to a Brand name or a verified chem.analisys
MG