I'm assuming you mean the inner bearing face that slides into the stub-axle..... the one that seems to weld itself to said stub-axle when the bearing collapses (not that I've ever been there, oh no - never had to rebuild the so&&ing thing at midnight, in the pi$$ing rain, at a rally on an island - no siree)
So, I'm assuming the hubs off, and all you have is the stub-axle with the bearing face practically welded in place.
Don't apply lots of heat: you'll melt the oil-seal on the inside of the stub-axle.
As mentioned above, use a cold-chisel to move the thing. The stub-axle has a shoulder on it that's about 5mm wide, so you're not trying to drive the chisel into the very corner!
It's really hard to get the thing to move... and you may need to try coming in from above, then left-side, then right-side, then above, then ....
If you have an appropriate splitting-chisel, you can try splitting the bearing-face, so it'll peel open and you can remove it that way.
You can do the angle-grinder trick.... but try not to score the stub-axle too much.
You can also take the stub-axle off, and do heat & stuff.... but remember you'll need to replace that inner oil-seal.
Once you've removes the bearing, you'll probably need a file to remove the burrs that have been created - if you don't, getting the new stuff on will be next-to impossible!
Tip #2
having got everything cleared off the stub-axle, make sure the replacement bearing will slide on: its a real pain in the proverbial to try and force the hub back on when the bearing carrier gets caught on a rough edge: won't go on, and now won't come off again either!!
A complete new stub-axle & bearings is fairly cheap, and saves LOADS of hassle ;-)