When I started deadlifting again i bought a belt too. Then i learned more about physiology and strengthened my core and stopped using the belt.
I haven't tried anything over 450 .
My work out weight varies from 325 to 405. Depending on purpose sets reps.
I still have the belt but i havent used it in 2 years. I tweaked something a year ago insanely repping 325 then yard work. I grabb3d 5h3 b3l5 for ny n3xt woekout..but omstead decided to skip it. Then the next one dropped the weight and slowly did some lpw reps then bped ip the next week and was back on track.
In my opinion your core should be your belt.