need help in shear blade material selection & hardness process

dear all, i am working on design & mfg. of TMT bar Cutting machine. I have problem in the material selection of shearing blade and its
appropriate hardness. i have used S1 ( K455 ) material and hardness is 56 to 58 HRC. But i found failure like blade breaking and edge damages while cutting.The TMT bar Is of 60 to 80 Kg/mm2. Can anybody will help me regarding the balde material selection and the hardness process? Matter is too urgent. Please....
Thanks & regards, Sainath Pohnerkar
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