时效温度对HSLA高强船体钢组织和性能的影响

Effect of aging temperature on microstructure and properties of HSLA ship-hull steel

采用固溶+时效的热处理方法研究了时效温度对HSLA(High Strength Low Alloy)高强船体钢组织性能的影响。结果表明,试验钢在450℃处出现强度峰值,这是由大量纳米级的Cu析出物(<5 nm)和少量Nb(C,N)粒子的共同强化造成。过时效状态下,基体的软化作用加强,且Cu析出粒子尺寸显著增大(10～30 nm),沉淀强化作用也逐渐减弱,钢的强度下降。时效过程中基体软化和析出相沉淀强化的共同作用决定了HSLA高强船体钢的性能变化规律。试验钢在650～670℃范围内时效不仅获得了670～780 MPa的强度,而且保证-40℃冲击功在80 J以上,体现出良好的强韧性匹配。

A high strength low alloy（HSLA）ship-hull steel was processed with solid solution at 900 ℃ and quenching in water and then aging at 400-700 ℃.Effect of aging temperature on microstructure and properties of the HSLA ship-hull steel was investigated by means of SEM,TEM,tensile test,impact test and hardness measurement.The results indicate that strength of the tested steels aged at 450 ℃ reaches the maximum value,which is attributed to the precipitation of a large amount of fine Cu particles（less than 5 nm） and a small number of Nb（C,N） precipitates.The effect of matrix softening enhances and the size of Cu particles is coarsened（10-30 nm） in the condition of over aging,and its precipitation strengthening is weakened resulting in the decrease of strength.The softening of matrix and the strengthening by precipitated phase are responsible for the variation of properties of copper-bearing high strength ship-hull steel during aging.Strength of the tested steel is 670-780 MPa when it is aged at 650-670 ℃ with the impact values higher than 80 J at-40 ℃,which shows a good combination of strength and toughness.