不同截面尺寸贝氏体非调质钢的组织和性能

研究了经920 ℃空冷,300 ℃回火后不同直径贝氏体非调质钢棒料的组织和力学性能。结果表明,不同直径贝氏体钢试棒,经空冷+回火后的组织均为贝氏体铁素体和残留奥氏体,属于无碳化物贝氏体组织,ϕ30 mm以下棒料热处理后组织变化较小,直径大于ϕ50 mm棒料,心部组织有所粗化,并伴随粒状贝氏体量的增加。热处理后,随棒料直径的增加,其强度、硬度有降低的趋势。直径大于ϕ50 mm棒料的冲击吸收能量随直径的增加有降低的趋势。ϕ70 mm棒料R/2处抗拉强度为1226 MPa,心部冲击吸收能量(KV₂)为61.3 J。较大直径的贝氏体非调质钢具有良好的强韧性。

Microstructure and properties of bainitic non-quenched and tempered steel with different section size

Microstructure and mechanical properties of the bainitic non-quenched and tempered steel bar with different diameters air-cooled at 920 ℃ and tempered at 300 ℃ were studied. The results show that the microstructure of the bainitic steel bar with different diameters after air cooling and tempering is the bainite ferrite and retained austenite, which belongs to non-carbide bainitic structure. The microstructure of the bars with diameter smaller than ϕ30 mm changes a little after heat treatment, but the core microstructure of the bars with diameter larger than ϕ50 mm becomes coarser and the amount of granular bainite increases. After heat treatment, with the increase of diameter, the strength and hardness of the bars tend to decrease. The impact absorbed energy of the bars with diameter larger than ϕ50 mm decreases with the increase of diameter. The tensile strength of the ϕ70 mm bar at R/2 is 1226 MPa, and the core impact absorbed energy is 61.3 J. Bainitic non-quenched and tempered steel with larger diameter has good combination of strength and toughness.