On the very first cut that you weren't happy with, was it a virgin piece of steel possibly with some scale on it? Even if it didn't have scale, steel that's been exposed for a long time will get a "skin" on it. Metal is a lot more porous than you might think and chemical reactions take place at the outer layer immediately upon manufacture and continues for years. Anyhow, once you nibble that layer off, you get to the nice juicy center...
Looks nice. Good cut.
Ray