Surface and Subsurface Cracks, Chips in 31803 Grade

Dear sir ,

we have a EAF root of stainless steel making route from scrap 40Tons per heat. WE have prepared some heats of 31803 grade with standerd chemistry. We prepare 240X280 billets and then roll it to 125Ø dia. We Solution anneal it to 1060°C for 4 Hrs. After that we peel it to 121Ø bright bar in 2 stages. The Bars are showing continous problems of 4 types of defects. 1. Straight cracks of around 10 -20 mm dia at some locations on bars. 2. a networks of cracks which are not much straight which shows oxides after EDAX analysis. 3. Chips 4.Black patches.

We are getting around 60% bars to be full lenght ok.

To take care of black patches we have increased the rolling size upto 127Ø and peeling nw is done in 3 steps.

But we are not sure about reson for the different crack which we are not able to remove even after peeling 4 - 5 mm.

Can anyone help me regarding this ??

Can u please tell me about what are the metallurgical factors responsible for formation of cracks, chips and other surface defects in steels