超级贝氏体钢的热处理

Heat Treatment of Superbainitic Steels

研究了分别含有0.0005%(质量分数)和0.0024%(质量分数)硼的两种试验用高硅高碳钢以获得超级贝氏体组织。奥氏体化后,试样分别在3种不同的等温温度(150℃、200℃和300℃)保温不同时间。采用带有显微硬度测定的光学显微镜和透射电镜观察试样的微观组织。结果表明,200℃等温转变10天后,两种钢均获得了高体积分数的含有纳米级贝氏体铁素体亚单元的束状组织,具有高达675 HV1的超高显微硬度。添加0.0024%(质量分数)硼能促进200℃等温处理初期的贝氏体相变,但对缩短相变的完成时间没有明显的影响。在150℃和300℃等温不能得到大量的贝氏体组织。

Two experimental high silicon high carbon steels （with 5× 10^-6 and 24 × 10^-6 of boron separately） have been investigated for the development of superbainite structure. After austenitisation, the specimens were held respectively at three different isothermal transformation temperatures （150,200, and 300 ℃ ） for a variety of time intervals. The microstructures were examined via optical metallography （with microhardness measurement ） and transmission electron microscopy. It was found that after isothermal transformation at 200 ℃ for 10 days, both steels produced a high volume fraction of sheaf structures with nanometre scaled bainitic ferrite subunits, which contributed to an ultrahigh microhardness, up to 675 HV1. It was also found that adding 24 × 10^-6 of boron accelerated the bainitic transformation in the early stage of isothermal transformation at 200 ℃, but did not have a significant effect on reducing the finish transformation time. Both isothermal temperature of 150 and 300 ℃ could not lead to the development of high amount of bainite.