关键词: F22钢, 回火温度, 回火时间, 力学性能, 微观组织

Abstract: F22 steel after quenching was subjected to tempering treatment at different temperatures (640, 670 ℃) and holding time (6, 12, 18, 24, 30, 40 h) to investigate the effect of tempering processes on its microstructure and properties. The results show that with the increase of tempering temperature and holding time, the hardness and strength of the F22 steel decrease, while the plasticity indicators increase. When the tempering time is less than 18 h, higher tempering temperatures and longer holding times result in better impact properties. However, when the tempering time exceeds 18 h, higher tempering temperature and longer holding time result in worse impact properties. A higher tempering temperature makes it easier for carbon to precipitate from the α-Fe solid solution. With the prolonging of tempering time, the martensitic lath structure gradually decomposes, and the precipitation and growth of carbides tend to become more uniform. However, when the tempering time exceeds 18 h, the carbides aggregate at grain boundaries, resulting in a decline in impact properties. After tempering at 640 ℃ for 18 h, the F22 steel achieves the optimal comprehensive mechanical properties. The hardness meets the requirement of ≤22 HRC, the yield strength reaches the maximum of 630 MPa, and the elongation, reduction of area and impact absorbed energy at －59 ℃ are relatively high, with values of 25%, 65%, and 268 J, respectively. By comprehensively adjusting the tempering temperature and holding time, the F22 steel can achieve similar microstructures and properties. For higher production efficiency, high-temperature short-time tempering can be adopted, while for better stability of comprehensive properties, lower-temperature long-time tempering is recommended.

Key words: F22 steel, tempering temperature, tempering time, mechanical properties, microstructure