论文部分内容阅读
应用马弗炉对灰口铸铁试样进行热循环处理,并通过Gleeble-1500、光学显微镜、电子显微镜和能谱仪等手段重点分析了灰口铸铁拉伸性能、基体组织、化学成分与热历程的相关性。发现铸态试样珠光体片层间距较大,石墨片较厚,且其周围存在铁素体,这是其拉伸性能较差的根本原因。经800℃保温3h控温冷却后,试样组织均匀性显著改善,低温抗拉强度提高约30%。多次热循环处理后,试样各温度下的拉伸性能均有所下降,这与高温氧化、脱碳有关。试样经30次热处理后,碳的质量分数降至1.55%,致使珠光体转变难以完成。同时,在石墨片周围形成硅、锰、铁等氧化物的疏松带,二次渗碳体和晶粒粗化也均是试样抗拉强度下降的重要原因。
The gray cast iron samples were subjected to thermal cycling with a muffle furnace. The tensile properties, matrix structure, chemical composition and thermal history of the gray cast iron were analyzed by means of Gleeble-1500, optical microscope, electron microscope and energy dispersive spectrometer Relevance. Found that the as-cast sample pearlite lamellar spacing larger, thick graphite sheet, and the presence of ferrite around it, which is the root causes of poor tensile properties. After heated at 800 ℃ for 3h, the homogeneity of the microstructure was significantly improved and the tensile strength at low temperature increased by about 30%. After several thermal cycles, the tensile properties of the samples at all temperatures have decreased, which is related to high temperature oxidation and decarbonization. After 30 times heat treatment, the mass fraction of carbon dropped to 1.55%, resulting in the pearlite transformation difficult to complete. At the same time, the loose bands of silicon, manganese, iron and other oxides are formed around the graphite sheets, and secondary cementite and grain coarsening are also important reasons for the decrease of tensile strength of the samples.