灰铸铁的凝固结晶过程-外文文献翻译

山东建筑大学毕业论文外文文献及译文 外文文献外文文献 Solidification of gray cast ironSolidification of gray cast iron Abstract This article investigates the solidification of hypo, eutectic and hypereutectic gray cast irons, using novel techniques developed bythe authors. The nature of the revealed macro and microstructure suggests that the solidification mechanism is different from that usually accepted. Keywords Solidification; Gray iron 1. Introduction Several authors have studied the solidification of eutectic gray cast iron of flake graphite morphology GI[1–7]. Commonly, the eutectic solidification unit is represented by a nearly spherical shape of austenite and graphite, as shown in Fig. 1. There is general agreement to consider that austenite and graphite grow cooperatively, being both in contact with the liquid phase. This picture of the solidification of GI is supported by the morphology of the graphite flakes, that resemble a rosette, as shown in Fig. 2, and by the fact that the inclusions, generally associated to the microsegregation at the last to freeze melt, are located between such units. Stead’s reagent reveals the microsegregation of phosphorus in GI, and it can delineate the units schematically represented in Fig. 1 in high P irons, usually referred to as ‘‘eutectic cells’’ [8]. Since austenite dendrites are not readily discernible, except in gray irons containing types ‘‘D’’ and ‘‘E’’ graphite, their ation and growth characteristics in GI have received limited attention. Some researchers have considered the role of austenite dendrites in the solidification of GI [2,6,7]. There is no doubt that austenite of hypoeutectic GI grows dendritically. On the other hand, most of the literature work state that austenite can grow with other morphologies when the carbon content reaches or exceeds the eutectic [3,7]. During the last years the authors of the present article carried out investigations that challenged the validity of the more firmly established models of the solidification of ductile iron DI [9 –11]. The use of a specially developed technique, that allows to 1 山东建筑大学毕业论文外文文献及译文 reveal the solidification macrostructure of DI, combined with the use of color metallography techniques that reveal the microsegregation pattern, showed that the macrostructure of DI is ed by relatively large austenite grains, that contain a very large numbers of graphite nodules. This was the case for hypoeutectic, eutectic, and also hypereutectic DI. The objective of this study is to investigate the solidification mechanism of GI by using the micro and macroscopic techniques, successfully applied for DI in earlier studies. Experimental s 2.1. Materials The melts utilized in the present study were produced by using a 50 kg medium frequencyinduction melting furnace. Low manganese pig iron, steel scrap and ferroalloys were used as raw materials. Melts were cast in resin bonded sand moulds to produce round bars of 20, 30 and 46 mm diameter. Table 1 lists the ch