... , 28SiMnB 2. Process: Forged 3. Heat treatment: Normalised-hardened & tempered We provide wide range of Harrow Disc, accurate in dimensions. These quality ... . Material: 65Mn or 60Si2Mn (Sup6), SUP9, 28SiMnB 2. Process: Forged 3. Heat treatment: Normalised-hardened & tempered 4. Hardness: 40-50HRC 5 ...