For weld prep grinding the first thing you need is a strong backing for your abrasive cloth. Then a premium abrasive makes a big difference in terms of speed of cut and belt life:
Both of our recommended materials come with a Y-weight waterproof polyester backing and a high performance grain.
In addition the FX87 comes with high performance a ceramic abrasive grain and grinding aids to increase the cut still further and keep the grinding temperature down.