I have repeatedly read that Japan has poor quality iron, but what exactly does that mean? Iron is an element, so all of the reserves were in an unfortunate oxide requiring sophisticated refining? Just low total abundance?
They had to get pretty creative in their use of ironsand to produce high quality steel.
Notably phosphorus is very hard to get rid of when it's in your metal. Before better metallurgy, the best steel worldwide was made out of low-phosphorus ores.