I used to get boat prop shafts free from the boatshop next to me....he had rich customers!......Anyway,the stainless in the shafts was all 300 grade (austenitic) I assume,but some was wonderful free machining,and some was so tough it was just scrap.....possible it was a monel.......He used to buy new prop shafts from the boat makers at high cost,and they new ones were always very soft ,free machining stainless.....lovely to work with.......And they bent very easily,which was good for his business.