Not that hard to figure. Chinese mills have been caught substituting 200 series stainless in place of 300. Their square tubing is atrocious, out of square, welding defects, etc. Our Purchasing department bought 1600 lf of 6x6 tube about 2 years ago, and it was a pain to fabricate with, plus the weld seams had apparently been either miswelded or repaired and ground off with a rock, leaving unsightly grinding marks, especially after painting. It took us just that one lot to decide no more Chinese. Additionally, given the level of integrity demonstrated by Chinese concerns over the last few years, I'm not sure I could sleep easily if Chinese steel was incorporated in critically loaded designs.