稀土对可锻铸铁石墨化的影响

可锻铸铁有一定的强度及延伸率,跟灰铸铁和球墨铸铁相比,能利用大量廉价的废钢,成本低于球铁,炉前铁水处理比球铁简单。但不足之处是可锻铸铁有一个较长的石墨化退火过程。如何缩短这一过程,是铸造工作者们正在积极探索的重点。为了寻找快速退火的途径,我厂用稀土硅铁对可锻铸铁原铁水进行孕育,在这方面做了一些试验。     

孕育硅对可锻铸铁低温快速石墨化的影响

研究了可锻铸铁低温快速石墨化的机理认为,复合孕育处理带入的硅在铁水中形成较显著的浓度起伏,从而改善了形核条件、铸态组织和碳化物形态,加速了共晶渗碳体的分解和珠光体的粒状化,为石墨形核与生长提供了良好条件,因而是实现低温快速石墨化的关键.     

硅对球墨可锻铸铁石墨化过程的影响

研究硅对球墨可锻铸铁高温和低温石墨化的影响,试验证明:含硅量大于1.8％,第一、二阶段石墨化速度较快。     

薄壁球墨铸铁白口组织的形成及影响石墨化的因素

简述了薄壁球墨铸铁容易产生白口组织的原因,抑制白口组织的生成应促进石墨化、增加石墨球数.介绍了化学成分C、Si、S、Mn、稀土元素及球化、孕育处理对石墨化的影响.应通过严格控制铁液成分、加强孕育并适当添加稀土元素,促使铁液充分石墨化,增加石墨球数来有效抑制白口生成.     

可锻铸铁低温石墨化的进一步探讨

文中指出,低温石墨化的关键在于改善共晶渗碳体的石墨化动力学条件,研究了工业纯硅、硅钡、硅锆及碳化硅等孕育剂及硅含量对低温石墨比的影响。电子探针分析表明:硅在共晶渗碳体界面处富集,少量硅进入共晶渗碳体中。X射线衍射分析表明:随硅量增加,渗碳体点阵参数增加,晶胞体积显著增大。并就生产中如何实现低温石墨化提出一些看法。     

硅促进可锻铸铁石墨化机理的探讨

采用电子探针及X射线衍射仪测定了可锻铸铁白口组织中硅的分布和硅对渗碳体点阵参数的影响。结果表明:硅在共晶渗碳体和珠光体界面处富集,少量硅进入共晶渗碳体中;提高含硅量,界面处硅的富集量及进入共晶渗碳体中的硅量增加,使渗碳体点阵参数及晶胞体积增大。最后讨论了硅对渗碳体稳定性的影响。     

可锻铸铁石墨化的几个问题

用电镜观察了可锻铸铁白口组织经预温处理后的变化。结果表明:白口组织中珠光体与共晶渗碳体间存在一定厚度的铁素体隔层,预温处理后在铁素体隔层处析出石墨,还讨论了可锻铸铁在奥氏体转变温度下退火的热力学及动力学条件。     

孕育剂对可锻铸铁石墨化的影响

提出在可锻铸铁的生产过程中，炉前使用稀土硅铁，铝及铋等微量元素进行孕育处理，能促进渗碳体的分解，加速石墨化过程，缩短退火周期。     

可锻铸铁快速循环石墨化退火的试验

试验研究了一种适于可锻铸铁的快速循环石墨化退火工艺。用此方法可使ＫＴＨ３５０—１０可锻铸铁的力学性能达到ＫＴＨ３７０—１２的水平。该工艺节能效果可达４０～７０％，且质量稳定。     

复合孕育对可锻铸铁白口组织中碳化物类型的影响

对经ＦｅＳｉＢａ５ＲＥ３＋ＮａＣｌ＋Ｂｉ复合孕育处理的可锻铸件白口试样进行Ｘ射线衍射分析,结果发现,其组织中出现ＦｅＣ型碳化物,而经常规孕育处理的试样中仅有Ｆｅ３Ｃ型碳化物。通过热力学分析探讨了ＦｅＣ型碳化物的形成机理及其对石墨化的影响。石墨化退火试验表明,经复合孕育处理的可锻铸铁白口试样,能在８００℃以下迅速实现完全石墨化。     

EFFECT OF STRUCTURE ON GRAPHITIZATION OF WHITE MALLEABLE CAST IRON

The structure of white iron treated with Si-Bi-AI complex inoculant has been observed bySEM and TEM. The results show that, in comparison with the samples treated with ordinaryinoculants, disorder, overlapping and inflexion of the pearlitic lamella appear, besides, the dis-location density increases apparently. The graphitization can be quickly realized at the tem-perature lower than that of austenitic transition (720℃).     

氮对灰铸铁基体组织的作用

研究了氮对Fe—C-Si和Fe—C—Si-Mn灰铸铁基体组织的作用,实验结果表明,氮使灰铸铁共晶团组织细化,珠光体含量增多,并使珠光体和铁素体显微硬度提高氮对灰铸铁平衡及非平衡相变温度的影响和它溶入铁素体及渗碳体中是强化灰铸铁基体组织的重要原因.     

EFFECT OF NITROGEN ON MATRIX STRUCTURE OF GRAY CAST IRON

Effect of nitrogen on matrix structure of 3 different varieties of gray cast iron,i.e.,sub-eutectic Fe-C-Si,near-eutectic Fe-C-Si and Fe-C-Si-Mn,has been investigated.The eutectie colony structure of gray cast iron may be refined,the pearlite content increasedand the micro-hardness of pearlite and ferrite raised with an addition of nitrogen.The influ-ence of nitrogen on the transformation temperature of the equilibrium and non-equilibriumphases,as well as,the solution of nitrogen in ferrite and cementite seem to be the major rea-sons to strengthening the matrix structure of gray cast iron.     

稀土元素对低合金耐磨铸铁耐磨性的影响

从改变共晶碳化物形貌的角度研究了稀土元素对低合金耐磨铸铁耐磨性的影响。结果表明,稀土元 素能改善共晶碳化物的形状,提高其耐磨性,尤其稀土变质后再经950℃×3h正火处理后效果更显著。     

EFFECT OF NITROGEN ON GRAPHITE MORPHOLOGY IN GRAY CAST IRON

The distribution of N and morphology of graphite in gray cast iron containing N werestudicd by adopting the man-made specimens of Fe-C-Si-Mn alloys with some N added.The N adsorbed along the interfaces between graphite and matrix together with solid-solutioned in graphite is believed to be the principal cause of morpholongical variationof graphite.     

氮对灰铸铁中石墨组织的作用

本文研究了氮在灰铸铁中的分布及含氮灰铸铁石墨组织结构,结果表明,氮在石墨与基体界面上的吸附和在石墨中的固溶是氮使石墨组织形态发生变化的主要原因。     

STUDY ON THE MECHANISM OF GRAPHITIZATION IN MOLTEN CAST IRON PROMOTED BY ELECTROPULSE DISCHARGE

From the points of both molten cast iron structure and the appearing ratio of electrons in outer-layer of different atoms, analysis on enhancement mechanism of graphitization ability after processing of the iron by pulse electric discharge has been made, and the theory has been proofed by corresponding experiments. The results show that when the molten cast iron is being processed by pulse electric discharge, both the size of crystal embryos that composed by Fe and C atoms as well as the number of clusters can be reduced, even be separated by such discharging; consequently results in the segregation of C atoms in the molten cast iron near the cathode of discharging. The nucleation of graphite in these areas of the iron has been promoted at the discharging temperature; even though such degree has not been reached, the mast favorablenucleation conditions of graphite can be at least created. Under the preconditions of not breaking up the graphite crystal embryos, with proper adjustment of discharging frequency, the stronger of the electric field and the longer of the pulsation treatment time are, the more graphitization ability of the molten cast iron is. The theoretical analysis on the above rules consists well with experimental results.     

工业灰铸铁凝固组织形成过程的数值模拟

从接近工业灰铸铁实际凝固过程的角度出发,提出了数值模拟其凝固组织的一套方法,其中主要包括枝晶奥氏体生长过程体积分类的计算以及晶粒接触因素的处理,该方法经以样杯中浇注的试块为对象进行实验验证,模拟得到的冷却曲线、向氏体分数及共晶团密度均与实测结果符合较好。     

新型镍铁铸铁焊条的研制——新铸438

在试验的基础上探讨了焊条药皮中不同碳酸锶含量对镍铁铸铁焊缝的石墨化及石墨球化的影响，在此基础上获得综合性能较好的“新铸４３８”焊条。     

EFFECT OF LASER MELTING PROCESSING ON MICROSTRUCTURE OF GRAY CAST IRON

The microstructure of the laser hardened layer on the HT20-40 gray cast iron after lasermelting processing'was examined by optical microscopy,transmission electron microscopy(TEM)and scanning electron microscopy(SEM).Experimental results showed that a struc-ture with dendritic(M+A')and interdendriticly laminal transformed ledeburite(M+A'+Fe_3C)was produced after laser melting processing.The martensite is a mixture of dis-location martensite and twin martensite.Dislocation pile-ups and twins were found in theresidual austenite.Microsegregation of composition and heterogeneity of microstructure werealso apparent after laser melting processing.