导　　师： 于化顺;刘复荣

学科专业： 080503

授予学位： 硕士

作　　者： ;

机构地区： 山东大学

摘　　要： 本文在生产条件下通过实验研究了碳硅元素、铜铬合金化、孕育处理对欧Ⅲ柴油机汽缸体显微组织和力学性能的影响。 实验研究结果表明在碳当量相当情况下,提高硅碳比,降低碳的百分含量,提高硅的百分含量,组织中初析奥氏体数量增多,加固了铸件基体。石墨量的减少,减轻了片状石墨对金属机体的切割作用。硅元素在基体中的固溶量增加,强化了珠光体中的铁素体,因此可以提高铸件抗拉强度。当碳硅比达到0.68时,抗拉强度可提高至336MPa。 铜元素能降低奥氏体转变的临界温度,细化并增加铸件珠光体含量。由于生产中铁水中有一定含量的铬、锡元素的存在,铜元素加入量的改变对铸件珠光体含量未产生明显影响。铜含量由0.2/%增加至0.4/%,基体组织中珠光体片间距得到明显细化,单铸试棒的抗拉强度由285MPa提高至310MPa。但是铜对细化珠光体的作用是有限的,当铜含量增加至0.5/%时,珠光体片间距不在发生明显变化,抗拉强度略有降低,这可能是铜元素偏析于共晶团晶界,增加了晶界脆性,削弱强度的缘故。 生产实践表明,孕育剂的加入方式和加入时间直接影响到孕育剂的吸收状况,而孕育剂的吸收状态对铸件性能有决定性的影响。实验证明,孕育剂直接加入包底,不利于孕育剂的吸收,铸件石墨形态分布差,抗拉强度低；采用出铁时随流孕育能够提高材料吸收,改善铸件石墨形态的分布,提高抗拉强度；当出铁量为1//3后开始加入孕育剂,加入时间为25s时,铸件的孕育效果最佳；当继续延长加入时间至35s时,后期加入孕育剂漂浮在铁水表面氧化烧损,不利于吸收,降低了铸件的力学性能。 作为生产线大批量生产,操作质量的稳定性对产品质量有着重要的影响。本文通过实施熔炼预控制、炉前处理材料的准确秤量、机械控制炉前处理材料加入时间等措施, The effects of Si//C, Cu Cr element, inoculation on the microstructure and mechanical properties were investigated to improve and stabilize materials properties of Euro diesel and the experiments had been done as producing in the workshop. The results show that the austenite amount is increased and the matrix is strengthened, while improving the Si//C ratio, because the cutting effect of flake graphite on the matrix is minished via graphite amount decreasing and Si strengthens the matrix via solid solution hardening. So the mechanical properties of castings are improved by this way, and ultimate tensile strength reached 336MPa when Si//C ratio was 0.68. Cu element can depress the critical temperature of austenite transformation, refine and increase the pearlite amount of matrix. Because of some amounts of Cr and Sn elements existing in molten iron, the pearlite content of casting matrix was not changed clearly by the addition of Cu. But the pearlite flake spacing was refined obviously, adding up to 0.4/% of Cu from 0.2/% wt pct. Because the effect of Cu on refining pearlite is finite, Cu content was increased to 0.5/%,the pearlite and tensile strength of separated specimen was changed little. The mechanical properties of casting were influenced significantly by the absorption of inoculant alloy which was affected directly by adding method and time. The experiment results indicated it was not beneficial to the absorption that the inoculant alloy was placed in the ladle, the graphite morphology and tensile strength of casting was bad and low produced by this method. The absorption could be improved by adding in the tapping stream, so the graphite morphology and tensile strength were improved. The inoculation effect was best when the adding time was 25 seconds after 1//3 tapping amount. If the adding time increased to 35s, the last inoculant alloy didn't be absorbed because of floating on the surface of molten iron. Operation stability is very important to the product quality in the mass product line

关 键 词： 灰铸铁 柴油机 气缸体 硅碳比 铜合金化 孕育处理 过程能力控制

领　　域： [金属学及工艺]