بررسي تاثير ميزان خلاء ريخته گري بر خواص مكانيكي فولاد فوق مستحكم T300

A Study of Casting Vacuum Pressure Influences on Mechanical Properties of T300 Ultra-Strength Steel.

In this research influence of casting vacuum pressure on microstructure & mechanical properties of T300 Ultra-Strength steel has been investigated. For this purpose, Five bars were casted On the VIM Furnace under the same solidification conditions but different amounts of Vacuum Pressure. All the bars were homoginized at 1200°C for a period of 2 hours. Then, They were immediately hot rolled after homogenization, So that the out rolled temperature was kept in the range of 1000-1200°C. The specimens were then solution annealed at 820°C for 30 minutes & finally they were aged for a period of 3 hours at 500°C. The microstructure of each bar was subjected to chemical analysis and studied by scanning electron microscope in order to see the variation in elements such as O, N, C and S due to application of different amount casting vacuum pressure and its effects on tensile and toughness properties. The results show that by decreasing the amount of casting pressure, the amount and size of inclusions decrease which result to improvement of microstructure and consequently to improvement of tensile and toughness properties. In addition, the results indicate that the amount of improvement of these properties, when the vacuum pressure exceed 102 Torr is negligible and non-economical, so it is recommended that a pressure of 10-2 Torr is good enough for casting this type of steel.