回火温度对30Cr15Mo1N微观组织和力学性能影响

Tempering temperature effect on microstructure and mechanical properties of 30Cr15Mo1N

为探索高氮马氏体钢在回火过程中组织性能演变,对30Cr15Mo1N高氮钢进行了不同温度下的回火处理,利用OM、XRD、拉伸、冲击、SEM和TEM等方法研究了高氮钢在回火过程中微观组织和力学性能的变化规律。结果表明,30Cr15Mo1N钢经淬火和低温处理后在150～700℃回火,随回火温度升高,显微组织中马氏体基体逐渐发生回复与再结晶,组织中马氏体形态逐渐消失,碳氮化物先在马氏体板条边界呈片状或棒状析出,逐渐演变为颗粒状弥散分布,700℃时碳氮化物聚集长大、球化。随着回火温度升高,30Cr15Mo1N钢的基体持续软化,析出强化不断增强,导致其在500℃以下回火时强度变化较小,抗拉强度保持在2 000 MPa以上;当回火温度大于500℃时,强度随回火温度升高而线性下降。随着回火温度升高,30Cr15Mo1N钢的U型缺口冲击吸收功先基本保持不变再持续升高,在700℃回火后冲击韧性达到45 J/cm2。不同回火温度下冲击性能的变化与其强度、塑性变化密切相关,冲击韧性好坏主要由塑性大小决定。

In order to explore the evolution of microstructure and properties of high nitrogen martensitic steel during tempering,the tempering treatment of 30 Cr15 Mo1 N high nitrogen steel at different temperatures was carried out. The changes of microstructure and mechanical properties of high nitrogen steel during tempering were studied by OM,XRD,tensile,impact,SEM and TEM. The results show that after 30 Cr15 Mo1 N steel is quenched after 1 h austenitizing at 1 030 ℃ and tempered twice at 150-700 ℃,with the increase of tempering temperature,the phase a matrix gradually recovers and recrystallizes in the microstructure,the body morphology gradually disappeared,and the carbonitrides first precipitated in the form of flakes or rods at the martensite slab boundary,and gradually evolved into a granular dispersion distribution. At 700 ℃,the carbonitride aggregates grow and spheroidize. As the tempering temperature increases,the matrix of 30 Cr15 Mo1 N steel continues to soften,and the precipitation strengthening is continuously enhanced,resulting in less change in strength when tempered below 500 ℃. Based on the mechanical test,it is found that after tempering at 500 ℃,the strength is linear with increasing tempering temperature decline. With the increase of tempering temperature,the U-notch impact absorption of 30 Cr15 Mo1 N steel is basically maintained at the level and then continues to rise. At last,it is concluded that the change of impact performance under different tempering temperatures is closely related to the change of strength and plasticity. The impact toughness is mainly determined by the plasticity.