高碳贝氏体钢的低温转变组织与性能

摘要：采用光学与扫描电子显微镜、X射线衍射等手段研究了不同等温温度（300、250、200℃）对于高碳（质量分数0.79%）贝氏体钢低温转变样品的相含量、组织尺寸和力学性能的变化规律。结果表明，随贝氏体等温温度的降低，贝氏体最终转变量更高，贝氏体铁素体板条和薄膜状残余奥氏体宽度、块状残余奥氏体尺寸减小，抗拉强度升高，塑韧性降低。300℃的贝氏体抗拉强度为1525MPa，贝氏体铁素体宽度是116nm，而200℃的贝氏体铁素体板条尺寸达到62nm，抗拉强度达到1 928MPa。研究发现，在未充分转变的贝氏体样品中，尺寸大于4.7μm的块状残余奥氏体在冷却过程中易发生马氏体相变，而小于该尺寸的残余奥氏体比较稳定，可以保留到最终组织中。

Low temperature transformation microstructure and properties of high carbon bainitic steel

The changes of phase content, microstructure and mechanical properties of high carbon（0.79 mass%）bainite steel obtained at different austempering temperatures (300, 250 and 200℃) were studied by means of optical and scanning electron microscopy, X-ray diffraction and other research methods. The results show that with the decrease of bainite isothermal temperature, the final transformation of bainite is higher, the thickness of bainitic ferrite lath and film like remains austenite, the size of block retained austenite decreases, the tensile strength increases and the plastic toughness decreases. The thickness of bainite-ferrite at 300℃ is 116nm and the tensile strength is 1525MPa, the thickness of bainite-ferrite at 200℃ is 62nm, and the tensile strength is 1928MPa. It is found that in the bainitie samples that are not sufficiently transformed, the block austenite with a size larger than 4.7μm is prone to martensite transformation during cooling, while the block austenite with smaller size is relatively stable and can be retained in the final structure.