THE HARDENING-TOUGHENING HEAT TREATMENT PROCESS OF HIGH CHROME CAST IRON GRINDING BALLS (2)
3.The graded austenitizing isothermal quenching process 3.1 Effect of grade austenitizing austempering on mechanical properties of Grinding Ball After the ball was austenitized at 980 °C for 150 min + 920 °C for 30 Min, and then put into a salt bath furnace at 260 °C for 30 min and 50 Min, the hardness and impact toughness of the ball were tested as shown in Table 3. The hardness and impact toughness of the grinding ball after 30 Min and 50 min austenitizing austempering are equivalent. The surface hardness is about 59HRC, the center hardness is about 54.5 HRC, and the impact toughness is 7.1ー7.4 J / cm2. The surface hardness of the grinding ball is similar to that of the quenched and tempered state, the impact toughness is greatly improved, and the comprehensive properties are slightly improved. 3.2 Effect of graded austenitizing austempering on microstructure The microstructure of the grinding ball after 50 Min austenitizing isothermal quenching is shown in Fig. 6. There ...