60Si2CrVA钢的低温贝氏体组织

Low Temperature Bainitic Microstructure in 60Si2CrVA Steel

用热膨胀法测定了 60Si2CrVA钢的相变点Ac1、Ac3和Ms,并用模拟热处理炉对试样进行了 1000℃保温 30min的奥氏体化、250℃(稍高于Ms点)×72h的低温等温转变处理。采用光学显微镜、透射电镜和X射线衍射仪对处理后 60Si2CrVA钢的组织和相组成进行了研究。结果表明, 60Si2CrVA钢热处理后得到由板条状贝氏体铁素体和薄膜状残留奥氏体组成、硬度为 463HV30的低温贝氏体组织,残留奥氏体的体积分数为 13. 7%,而不是传统的下贝氏体组织。

Phase transformation points, Ac1, Ac3 and Ms, of 60Si2CrVA steel was measured by thermal dilatometry. An isothermal transformation of the steel was carried out for 72 h at 250°C, a little higher than Ms, after being austenized at 1000°C for 30 min by using a simulating heat-treatment furnace. The microstructural morphology and the phase composition were investigated by optical microscopy, transmission electron microscopy and X-ray diffractometer. The results show that the low temperature bainitic microstructure with hardness of 463HV50 instead of the conventional lower bainite has been obtained after the heat treatment of the steel. This low temperature bainitic microstructure is composed of lath-like bainite + ferrite and film-like retained austenite with 13.7% in volume fraction.