淬火工艺对铜沉淀强化UHS钢组织性能的影响

超高强度钢不仅可以降低海洋装备本身质量,而且节约能源,但这类钢应用过程中要求具有良好的强韧性匹配,而淬火工艺显著影响其后续的相变和性能。采用Thermo-Calc软件、光学显微镜、扫描电镜以及透射电镜等研究了淬火工艺对低碳(w(C)<0.05%)铜沉淀硬化超高强海工钢组织性能的影响。结果表明,910℃淬火、450℃时效处理后峰值硬度达到386HV,700℃时效后空冷可得到部分二次马氏体组织,峰值硬度为357HV。525℃以下时效,富铜相析出的平均半径约为5nm,产生较高的强化增量。820~910℃淬火,随着淬火温度降低,细小的(Nb,Ti)C粒子能够有效抑制奥氏体晶粒的长大,细化晶粒和马氏体板条块,同时基体中小角度界面密度增加,强韧性提高。其中820℃淬火强度最高达到1 109MPa,-80℃V型冲击功为91J。

Effect of quenching process on microstructure and mechanical properties of Cu precipitated hardened ultra high strength steel

High toughness and ultra high strength marine engineering steel can reduce the weight of marine equipment itself and save energy，but it requires good strength toughness matching for this kind of steel application，and quenching process significantly affects its subsequent phase transformation and mechanical property. Effects of quenching process on the microstructure and mechanical properties of Cu bearing ultra high strength marine engineering steel were investigated depending on low carbon (w(C)<0.05%) design by optical microscopy，scanning electron microscopy and transmission electron microscopy. The results showed that the highest peak hardness was 386HV at 450 ℃ aging after 910 ℃ quenching，and the partial secondary martensite microstructure was attained at 700 ℃ aging by air cooling，and the peak hardness was 357HV. The average precipitation radius of the copper rich phase was around 5 nm under 525 ℃ aging，which gave rise to a higher strengthening increment. When quenched at 820-910 ℃，grains and martensite lath blocks of Cu bearing steel were refined with decreasing quenching temperature，which improved grain boundary density of low angle in the matrix，resulting in the increment of strength and toughness. The highest strength reached 1 109 MPa at 820 ℃ quenching，and -80 ℃ impact toughness was 91 J.