Cr含量降低对H13钢组织与力学性能的影响

对比了Cr含量降低为3%的3Cr-H13钢与Cr含量为5%的传统H13钢性能的差异,利用SEM、TEM、XRD进行微观组织与相组成分析,研究了Cr对H13钢组织性能的影响。结果表明,Cr含量的降低明显提高了H13钢的回火稳定性与高温强度,其原因主要与回火组织中马氏体的回复程度及二次析出碳化物的种类有关。传统H13钢在650℃回火时,马氏体基本回复完全,基体强度明显下降,并在原马氏体板条界和晶界上析出了较多的尺寸为120nm左右的近球形Cr7C3和M6C型碳化物,第二相强化效果降低;而Cr含量降低为3%的3Cr-H13钢在650℃回火后,基体依然为板条马氏体,板条内保持较高的位错密度,同时板条内析出的大量细小弥散的短棒状VC,在起到弥散强化作用的同时还钉扎位错,推迟了马氏体的回复,从而提高了高温性能。

Study on Microstructure and Mechanical Properties of H13 Tool Steel After Chromium Content Reduction

Properties of traditional H13 steel with 5% Cr and modified H13 steel with 3% Cr were compared,relevant micro-structures and phase composition were also investigated using scanning electron microscopy,transmission electron microscopy and X-ray diffraction,and the effect of Cr on the microstructures and properties of H13 steel were studied.The results demonstrated that the tem-pering resistance and high temperature strength of H13 steel were remarkably enhanced by reducing the Cr content,mainly related to the level of recovery of martensite and the types of precipitates during tempering.When the traditional H13 steel was tempered at 650℃,the martensite was almost completely recovered and a large amount of near spherical Cr7C3 and M6C type carbides with a size of about 120 nm were precipitated along the original martensite lath boundaries and grain boundaries,reducing the second phase reinforce-ment effect.But for the modified H13 steel with 3% Cr,the lath martensite with high dislocation density was still observed after 650 ℃tempering,and intensive plate-like VC type carbides with a length of about 25 nm and thickness about 2.5 nm were found within the martensite lath.The dispersed VC carbide precipitated during tempering significantly inhibited the recovery of martensite,thus enhan-cing the high temperature properties.