the reaction requires the vanadium carbide to be complete surrounded by molten steel, so if you drip in individual pixels of vanadium carbide into the molten steel area that is the best way :)
I tried this today, but it doesn't seem to work either. Vanadium Carbide pixels just stay on top of Molten Steel if I drop them individually.
I also tried making a big pool of Molten Steel in my blender forge, so I could force Vanadium Carbide pixel to dip inside Molten Steel, but it didn't work as well.