【作者】 李峰；

【导师】 黎振华；

【作者基本信息】 昆明理工大学 ， 材料加工工程， 2014， 硕士

【摘要】 亚共晶Fe-C-B合金是以硼为主要合金元素的新型铁基耐磨材料,由于其生产成本低,熔炼工艺简单,铸造性能好,近年来得到人们越来越多的关注。本文在前人研究的基础上,选取无铬亚共晶Fe-0.4C-1.5B合金,以锻造和轧制形变为手段,研究了形变量以及形变后热处理工艺对合金中含硼硬质相形貌分布、力学性能以及冲击磨料磨损性能的影响,并对变质与形变复合处理进一步改善硬质相分布、提高合金性能进行了初步研究。Fe-0.4C-1.5B合金的凝固组织为珠光体、铁素体以及共晶莱氏体,共晶莱氏体中网状分布的含硼硬质相Fe3(B,C1和Fe2B严重割裂基体,影响合金性能。热处理难以改变硬质相连续网状分布的特征。试验结果表明,锻造形变后合金中硬质相连续网状分布的形貌消失,转变成大块状聚集态。轧制形变后合金中连续网状分布的硬质相出现明显断网的现象,但不发生聚集。锻造和轧制形变后合金基体组织连续性增强,出现了少量二次硬质相,合金的硬度略有提高,而冲击韧性则大幅提高。对轧制形变量的研究表明,形变量在0到66.7%范围内,随着形变量的增加,硬质相的断网现象越来越明显,基体的连续性逐渐增强,共晶莱氏体组织逐渐减少,硬质相聚集现象越来越明显,二次硬质相数量有一定的增加。合金的硬度没有明显的变化而冲击韧性随着轧制形变量的增加而增加,合金的耐磨性也逐渐增加。形变量为66.7%时,经过1050℃保温30min后淬火处理,合金的硬度为58.3HRC,冲击韧性为12.6J/cm2,耐磨性是Cr20Mo高铬铸铁的1.21倍。对锻造比为1.2形变后合金淬火温度的研究表明,淬火温度在850℃到1100℃范围内,随着淬火温度的升高,合金中硬质相颗粒逐渐合并长大为条块状形貌的硬质相,同时硬质相的体积分数下降。合金冲击韧性逐渐降低而硬度和耐磨性逐渐增加到最大值后略微降低。淬火温度为1050℃时硬度达到57.8HRC,冲击韧性为9.3J/cm2,耐磨性与Cr20Mo高铬铸铁相当。稀土Ce变质处理的研究表明,随着稀土添加量的增加,莱氏体的团簇现象减少,含硼硬质相粗化,局部断网,基体的连续性增强,合金的硬度没有明显的变化规律,而冲击韧性则逐渐下降。变质处理后的合金结合66.7%形变和1050℃淬火处理后,硬质相出现了明显的断网现象,且有被拉长的趋势,析出少量二次硬质相。合金的硬度略有提高,而冲击韧性则大幅提高,平均提高了1.67倍,具有较好的耐磨性。综合考虑合金的力学性能和耐磨性,当稀土添加量为0.2%时,形变量为66.7%,淬火温度为1050℃时,合金性能最佳,此时,合金的硬度达到58.9HRC,冲击韧性为14.3J/cm2,同时,耐磨性是Cr20Mo高铬铸铁的1.55倍,具有较好的应用前景。更多还原

【Abstract】 Hypoeutectic Fe-C-B alloy is a new kind of iron-based wear resistance material which the main alloying element is boron, in recent years, the alloy attracted more and more attentions due to its low cost of production, simple melting process and well castability. The non-chromium hypoeutectic Fe-0.4C-1.5B alloy was selected to study on the basis of predecessors’ research, Forging and rolling was used for deformation, the effect of deformation rate and quenching temperature after deformation on the hard phase morphology and distribution, mechanical properties and wear resistance of the alloy were researched, and combine with deformation and modification of rare earth in order to further improve the distribution of hard phase and the properties of the alloy were preliminary studied.The solidification microstructure of the Fe-0.4C-1.5B alloy is made up of pearlite, ferrite and eutectic ledeburite, the continuous network hard phase containing boron consists of Fe3(B,C) and Fe2B in ledeburite spilt the matrix which affect the performance of the alloy. The hard phase morphology is hard to be improved by heat treatment. The experiment results show that the hard phase continuous network morphology disappeared and broken into gathered particles after forging deformed. The continuous network hard phase was broken evidently while no gathered after rolling deformed. After deformed by forging and rolling, the continuity of matrix was enhanced and some second hard phase appeared, in addition, the hardness of the alloy increased a little and the impact toughness improved significantly.The study on the effect of rolling deformation rate indicated that in the range of0～66.7%deformation, with the increase of deformation rate, the broken of hard phase more and more evidently, the continuity of matrix gradually reinforced, ledeburite reduced and more gathered hard phase particles appeared, second hard phase increased. The hardness of the alloy no obvious changing rule, while the impact toughness increases and the wear resistance of the alloy rises. When deformation rate is66.7%, after austenitizing at1050℃for30min then quenched, the hardness of the alloy is58.3HRC, the impact toughness reached12.6J/cm2, and the wear resistance is1.21times as well as Cr20Mo high chromium cast iron.The research on quenching temperature for1.2forging rate deformed alloy shows that in the range of850℃～1100℃, with the increase of quenching temperature, the broken hard phases particles merged and formed bulk and strip hard phases appear, and the volume of hard phase decreased; The impact toughness decreased, while the hardness and wear resistance of the alloy were gradually increase to maximum and then decrease a little. When quenching temperature is1050℃, The hardness of the alloy is57.8HRC, impact toughness is9.3J/cm2, the wear resistance is very close to Cr20Mo high chromium cast iron.The study on cerium modification indicated than with the increase of additive amount of rare earth, the clusters of ledeburite reduced, the hard phase coursing and continuous network local broke, the continuity of matrix strengthened, the hardness of the alloy no changing rule while the impact toughness decrease. The modification alloy after66.7%deformed and1050℃quenched, continuous network hard phase broken evidently and tend to be lengthened, a little second hard phase appeared. In addition, the hardness of the alloy increase slightly and the impact toughness increased1.67times on average, and with good wear resistance.Take into account of mechanical property and wear resistance, when added rare earth is0.2wt.%, deformation rate is66.7%and quenching temperature of deformed alloy is1050℃, best properties achieved. After that, the hardness of the alloy is58.9HRC, the impact toughness is14.3J/cm2, at the same time, the wear resistance of it is1.55times as well as Cr20Mo, which with good application prospect.更多还原