球墨铸钢指的是碳含量介于普通高碳钢和低碳灰铸铁之间的一种新型工程材料。其基本特点是通过对钢水的球化处理使材料在铸态下得到一定量的球状石墨和碳化物，基体组织为片状珠光体或索氏体。通过合金化和热处理，可以改变球墨铸钢中石墨、碳化物、珠光体的数量和形态。球墨铸钢综合了普通高碳钢和球墨铸铁的特点，具有良好的耐磨性、耐热疲劳、抗热裂等性能。目前国外已经开始应用于生产实际中。 目前国内外在该领域的研究中，对球墨铸钢工艺性能较少涉计，热处钢水取样器理对组织、性能的影响不全面，石墨球化机理探讨不多。本文针对这一研究现状进行了上述几个方面的研究。另外本文在研究过程中，发现在锻造和正火条件下得到了粒状珠光体，这在球墨铸钢领域里是未见报道的。本文就此作了碳化物球化机理的研究，是本文的创新之一。本文研究具体如下： (1)工艺性能：球墨铸钢具有较好的铸造工艺性能。在1500℃左右，流动性螺旋试样达到950mm；体收缩率为4.2%左右；线收缩率2%以下。球墨铸钢具有良好的锻造性能和可切削性。 (2)热处理：通过退火，基体组织为粒状珠光体，强度、硬度下降，韧性大幅度上升；锻造、正火后，基体组织为粒状珠光体。在860～950℃之间正火，可以得到理想的粒状珠光体组织。 (3)石墨球化机理：本文认为球墨铸钢中的球状石墨核心有夹杂物和气泡两种。球化剂在石墨形核和生长阶段起重要作用。 (4)碳化物球化机理：高温下材料中的未溶碳化物是随后粒状碳化物形成的现成核心；由于石墨的存在，高温下奥氏体不均匀程度很高，有利于粒状 四川大学硕士学位论文珠光体的形成。热加工时，位错密度大大增加，使碳出现偏聚，增加了奥氏体不均匀的程度，促进粒状珠光体的形成。Cast steel with spheroidal graphites is a new kind of engineering material. The carbon content of it is between plain carbon steel and grey iron. In use of spheroidizing agency treatment, some spheroidal graphites and carbide on the matrix of lamellar or sorbitic pearlite can be achieved in as-cast state. By means of alloying and heat treatment, the amount and shape of the graphite, carbide and pearlite can be changed objectively. The material is of wide application because of the excellent properties of wear resistant, thermal fatigue and so on. At present, the research on spheroidal梘raphite cast steel at home and abord, many aspects are studied little. For example, technology property and the spheroidal mechanism of graphite. The work of this thesis involved in the content above. During the study, spheroidal pearlite of spheroidal-graphit cast steel has been achieved after hot-forging or normalizing first. And in this thesis, the spheroidal mechanism of carbide was researched in detail.The main work of this thesis is as follows:(1) Technology properties: Cast steel with spheroidal graphites has excellent castability such as fluidity. Also it has good ductility and machineability.(2) Heat treatment: Through annealing, spheroidal pearlite can be achieved ,and toughness rises, and on the other hand strength decreases. In range of 860-950℃ normalizing, ideal spheroidal pearlite can be achieved after normalizing.(3) Spheroidal mechanism of graphite: The point of this thesis is that the nucleution of spheroidal graphites come from the inclusion or bubble in the melt steel.(4) Spheroidal mechanism of carbide: The study of this thesis shows that, the first, the non-dissolution carbide at high temperature is the main nuclei of forming spheroidal carbide钢水取样器; the second, the existing of graphites make the austenite become non-uniformly highly, which is advantageous to the formation of spheroidal pearlite; at last, the density of dislocation of the material increases greatly after hot forging, then segregation of carbon occurs, which also result in non-uniformly austenite and then spheroidal pearlite.