In this study, in addition to forming a steel tube of D6AC by direct flowforming, in order to examine the effects of different parameters of heat treatment process on the a for mentioned part properties, different cycles of heat treatment process are designed and after doing so, mechanical properties and microstructural changes of flowformed tube are investigated. For this purpose, at 850, 900 and 950 ˚C austenitizing temperatures for 15 and 30 minutes and AUS-BAY quenching at 510 ˚C for 10 minutes, and then quenching at 60 ˚C oil are used. Initial tempering for 2 hours at 250 ˚C and final tempering for 2 hours at 250, 300, 350 and 450 ˚C was performed. Investigations show that the optimum heat treatment cycle is austenitizing at 850 ˚C for 30 minutes, and final tempering at 300 ˚C, because of creating high strength and suitability for fracture toughness. Due to small grains of initial austenite, the ductility properties are also adequate.