If you are wishing to grind back tig welds on a steel fabrication then you are almost certainly after a high quality finish and are quite likely to be putting a good quality wet paint finish onto the metal. So there is no point grinding away the metal with a P36 grit disc as you might as well have stick welded it!!
Cibo K3K P80 grit fibre discs will give you great cut rate, good control of the grinding action, a cool cut and an excellent finish.