摘要
设计了气氛混合装置,控制炉气成分以及H2O(g)含量,利用真空管式加热炉对弹簧钢铸坯试样进行加热保温。采用激光多点共聚焦显微镜研究了混合气氛下H2O(g)对弹簧钢表面脱碳的影响。结果表明,试样总脱碳层厚度随温度升高而增加;混合气氛下,650℃出现轻微铁素体脱碳,700～950℃有明显铁素体脱碳层,850℃为铁素体脱碳峰值温度,与空气条件相比,表面铁素体脱碳更加严重,脱碳开始温度有所降低。低温区表面脱碳的发生与C浓度梯度驱动下珠光体片层中渗碳体的溶解有关,铁素体脱碳层晶粒形态呈现为尺寸细小、无明显取向。H2O(g)破坏防止脱碳的保护机制,对试样脱碳程度的加深有重要作用。
Spring steel is an important steel widely used in the national economic construction. Its application environment is quite harsh, so it strongly demands for a high quality of the surface. However, the decarburization behavior on the surface seriously affects the surface quality and reduces the fatigue performance of materials. Decarburization is caused by chemical reaction between oxidizing atmosphere and steel surface. Hydrosphere, as a component of the oxidizing atmosphere, could lead to a significant influence on decarburization process. Our experimental materials, taken from continuous casting billet, were polished carefully by abrasive paper in order to remove stains, original scale and decarburization layer. Components of furnace gas were controlled by mixing units designed independently. Spring steel samples were heated by a tube vacuum furnace in 600-950 ℃. The mixed atmosphere contains （15%-20%）CO2, （2%-4%）O2, hydrosphere of different contents and N2 in balance. With the condition of the mixed atmosphere, influence of hydrosphere on surface decarburization of spring steel 55SiCr was investigated by 3D measuring laser microscope. The results show that, with the influence of the mixed atmosphere, decarburization is able to happen during low temperature interval, 650 ℃-Ac1 （Ac1： starting temperature of austenitization during slow heating）. The thickness of total decarburized layer increases correspondingly with the temperature. In the mixed atmosphere, slight decarburization occurs at 650 ℃ and obvious ferrite decarburization layer can be detected within a temperature range of 700-950 ℃, which is more serious than that in the air. The peak temperature of ferrite decarburization is 850 ℃ under both mixed atmosphere and air. The surface decarburization in low temperature region is related to the dissolution of cementite in pearlite lamellae driven by carbon concentration gradient. When the decarburization degree deepens as time goes, partial pearlite colony begins to shrink, much line
作者
张凯
陈银莉
孙彦辉
徐志军
Kai ZHANG;Yinli CHEN;Yanhui SUN;Zhijun XU(Collaborative Innovation Center of Steel Technology,University of Science and Technology Beijing,Beijing 100083,China;Institute of Engineering Technology,University of Science and Technology Beijing,Beijing 100083,China)
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2018年第10期1350-1358,共9页
Acta Metallurgica Sinica
关键词
弹簧钢
表面脱碳
H2O(g)
加热温度
氧化层
spring steel
surface decarburization
hydrosphere
heating temperature
oxide scale
