I would think that a refrigerator with a couple of light bulbs it it would not get hot enough to keep 7018 welding rods hot enough. I had this rod oven set at 200 degrees, when I used 3/32 7018 out of the oven I would see holes in the weld. I increased the oven temperature to 325 and the problem went away.
Here is a link to what a rod oven. com recommends look at storage and exposurer limits. re-drying looks interesting also