I was cutting a sheet of steel with an angle grinder when suddenly the rate at which the blade was cutting slowed way down. I tried a few different things, and turned off the tool and looked at the blade. It didn't look damaged, but it definitely was not cutting as quickly. I thought either I had hit a harder section of steel (is that possible? It looked pretty uniform) or the blade had lost it's abrasive quality or something. Also, before this happened I had accidentally cut into the wooden sawhorse that was holding up the steel sheet, but I've done that before with no problem. After a short while the problem fixed itself and the rate of cutting went back to a fast normal. Anyone know why this happened?
Sounds like the abrasive surface got blinded, coated with something that prevented the abrasive particles from touching the steel. It is possible to have vastly different hardnesses in a single piece of steel. Case hardening, carburizing, induction hardening, heat affected zone from welding, differences in work hardening, and presence of inclusions are some of the things that can create hardness variation within a single piece. But... sounds like you are working with a sheet which is unlikely to have any of these conditions. So... it was probably the grinding disk
Your blade was overheated. Change it into diamond blade shall do.
