Mechanism of Microscopic Fracture of Typical Shell Steel under Impact Loading

Table 1

Four material states.

Material	Heat treatment process		Metallographic structure	Number
	Quenching	Tempering
50SiMnVB	Keep at 880°C for 60 min, oil cooled	Holding temperature at 550°C for 90 min, water cooling	Tempered sorbite	I
		Holding temperature at 450°C for 90 min, water cooling	Tempered troostite	II
60Si2Mn		Holding temperature at 550°C for 90 min, water cooling	Tempered sorbite	III
		Holding temperature at 450°C for 90 min, water cooling	Tempered troostite	IV