Speeding up the prediction of C-O cleavage through bond valence and charge on iron carbides

The activation of CO on iron-based materials is a key elementary reaction for many chemical processes.We investigate CO adsorption and dissociation on a series of Fe,Fe_(3)C,Fe_(5)C_(2),and Fe_(2)C catalysts through density functional theory calculations.We detect dramatically different performances for CO adsorption and activation on diverse surfaces and sites.The activation of CO is dependent on the local coordination of the molecule to the surface and on the bulk phase of the underlying catalyst.The bulk properties and the different local bonding environments lead to varying interactions between the adsorbed CO and the surface and thus yielding different activation levels of the C-O bond.We also examine the prediction of CO adsorption on different types of Fe-based catalysts by machine learning through linear regression models.We combine the features originating from surfaces and bulk phases to enhance the prediction of the activation energies and perform eight different linear regressions utilizing the feature engineering of polynomial representations.Among them,a ridge linear regression model with2nd-degree polynomial feature generation predicted the best CO activation energy with a mean absolute error of 0.269 eV.

Production of carbide-free thin ductile iron castings

The fast cooling rate of thin ductile iron castings requires special consideration to produce carbide-free castings. Extraordinary care was taken to select the charge to produce castings of 100-mm long round bars with 16-mm diameter. The castings show the presence of carbides in the bars. Seven melts were made with different temperatures and with different compositions to get rid of carbides. After chemical analyses,it was found that the extra purity of the charge with less than 0.008wt% sulfur in the castings was the cause of carbides. To remove the carbides from the castings,sulfur should be added to the charge.

Structures and Properties of Iron Matrix Composites with Tungsten Carbide Particle by EPC-V Process

In this paper the Expendable Pattern Casting with dry sand Vacuum(EPC-V) process is used to manufacture iron matrix composites with tungsten carbide particle.Microstructures of the composites layers were analyzed.The abrasive wear resistance of the composites layers were tested and compared with that of high chromium cast iron.The results show that the iron matrix composites with tungsten carbide particle have high hardness.The abrasive wear resistance of composites with tungsten carbide particle is higher than that of high chromium cast iron.The properties of the matrix materials have been improved remarkably.

Effect of Rare Earth Elements on Carbide Morphology and Phase Transformation Dynamics of High Ni-Cr Alloy Cast Iron

The effect of rare earth(RE) elements on carbide of high NiCr alloy cast iron was investigated. Meanwhile, the continuous cooling transformation(CCT) curves of cast iron with and without RE addition were determined. The results show that the carbides in high NiCr cast iron can be refined and changed from network and long strip structures into island and block ones. The phase transformation temperature was raised and incubation period of bainite transformation was shortened by adding RE element in high NiCr alloy cast iron.

Catalytic performance of iron carbide for carbon monoxide hydrogenation

Novel iron carbide and potassium-promoted iron carbide catalysts were prepared and investigated for CO hydrogenation. The iron carbide showed high activity for CO hydrogenation under high pressures; with the addition of potassium, activity and selectivity to C5＋ hydrocarbons were greatly enhanced, and the selectivity to methane was suppressed under high pressure.

Effect of partial remelting time on the initial carbide in semisolid structure of hypereutectic high Cr cast iron

In order to review the effect of partial remelting time on the morphology of initial carbides, semisolid ingots of hypereutectic high Cr17 cast iron were remelted at 1270℃ for four different times, and the changing characteristics of shape factor and the equivalent diameter of initial carbides were analyzed quantitatively using a Leica image analyzer. The results indicate that firstly, the evolution process of the initial carbides' morphology undergoes melting, spheroidization and refining during the partial remelting; secondly, the solute diffusion and interface tension take dominant roles at the primary and the middle-final stages respectively in the process of initial carbide evolution; finally, a perfect structure can be obtained by remelting semisolid ingots at 1270℃ for 15 min.

Influence of secondary carbide precipitation and transformation on abrasion resistance of a 3Cr15Mo1V1.5 white iron

The relationship between the secondary carbide precipitation and transformation of the 3Cr15Mo1V1.5 white iron and abrasion resistance was investigated by using optical microscope （OM）, transmission electron microscopy （TEM） and X-ray diffrac- tion （XRD）. The results show that the properties of secondary carbides precipitated at holding stage play an important role in the abrasion resistance. After certain holding time at 833 K subcritical treatment, the grainy （Fe, Cr）23C6 carbide precipitated and the fresh martensite transformed at the holding stage for 3Cr15Mo1V1.5 white iron improve the bulk hardness and abrasion resistance of the alloy. Prolonging holding time, MoC and （Cr, V）2C precipitations cause the secondary hardening peak and the corresponding better abrasion resistance. Finally, granular （Fe, Cr）23C6 carbide in situ transforms into laminar M3C carbide and the matrix structure transforms into pearlitic matrix. These changes weaken hardness and abrasion resistance of the alloy sharply.

Formation mechanism of spheroidal carbide in ultra-low carbon ductile cast iron

The formation mechanism of the spheroidal carbide in the ultra-low carbon ductile cast iron fabricated by the metal mold casting technique was systematically investigated. The results demonstrated that the spheroidal carbide belonged to eutectic carbide and crystallized in the isolated eutectic liquid phase area. The formation process of the spheroidal carbide was related to the contact and the intersection between the primary dendrite and the secondary dendrite of austenite. The oxides of magnesium, rare earths and other elements can act as heterogeneous nucleation sites for the spheroidal carbide. It was also found that the amount of the spheroidal carbide would increase with an increase in carbon content. The cooling rate has an important influence on the spheroidal carbide under the same chemical composition condition.

Technology of Iron Carbide Synthesis

铁碳化物是很有希望的冶金产品和罐头是使用的 forsteelmaking 过程，在它作为一种选择玩的地方，有重要经济的原料有利。另外，它有许多另外的应用，例如催化剂，磁铁，传感器。现在的评论调查铁碳化物的不同性质和使用。为铁碳化物合成(气体的渗碳(作用) ， mechanochemical 合成，激光热分解，血浆热分解，化学蒸汽免职和离子培植) 的商业生产和不同变化被考察。另外，象煤气的作文，原料，温度，反应时间，催化剂存在和硫增加一样的渗碳(作用) 过程上的不同因素的效果被显示。

Formation and Growth of Granular Carbides in Multiple Alloying Wear Resistant Cast Iron Containing RE Through Hot Deformation

The granular carbides formed from hot deformation in multiple alloying wear resistant cast iron were studied through the observation by means of optical microscope, SEM and TEM. The experimental results show that carbides with large size are formed from original short rhabdoid carbides existing in cast, those with small size directly nucleate in the matrix. Carbides with the size between the above are formed from precipitation induced by hot deformation. The bigger the deformation is, the larger the number of microsized granular carbides is. The mechanisms of nucleation and growth of granular carbides and the function of RE were discussed.

Effect of vanadium and chromium on the microstructural features of V–Cr–Mn–Ni spheroidal carbide cast irons

The objective of this investigation is to study the influence of vanadium（5.0wt%–10.0wt%） and chromium（0–9.0wt%） on the microstructure and hardness of Cr-V-Mn-Ni white cast irons with spheroidal vanadium carbides. The alloys＇ microstructural features are presented and discussed with regard to the distribution of phase elements. The structural constituents of the alloys are spheroidal VC, proeutectoid cementite, ledeburite eutectic, rosette-shaped carbide eutectic（based on M7C3）, pearlite, martensite, and austenite. Their combinations and area fraction（AF） ratios are reported to be influenced by the alloys＇ chemical composition. Spheroidized VC particles are found to be sites for the nucleation of carbide eutectics. Cr and V are shown to substitute each other in the VC and M7C3 carbides, respectively. Chromium alloying leads to the formation of a eutectic（γ-Fe ＋ М7С3）, preventing the appearance of proeutectoid cementite in the structure. Vanadium and chromium are revealed to increase the total carbide fraction and the amount of austenite in the matrix. Cr is observed to play a key role in controlling the metallic matrix microstructure.

Abrasive resistance of metastable V–Cr–Mn–Ni spheroidal carbide cast irons using the factorial design method

Full factorial design was used to evaluate the two-body abrasive resistance of 3wt%C–4wt%Mn–1.5wt%Ni spheroidal carbide cast irons with varying vanadium（5.0wt%–10.0wt%） and chromium（up to 9.0wt%） contents. The alloys were quenched at 920℃. The regression equation of wear rate as a function of V and Cr contents was proposed. This regression equation shows that the wear rate decreases with increasing V content because of the growth of spheroidal VC carbide amount. Cr influences the overall response in a complex manner both by reducing the wear rate owing to eutectic carbides（M7C3） and by increasing the wear rate though stabilizing austenite to deformation-induced martensite transformation. This transformation is recognized as an important factor in increasing the abrasive response of the alloys. By analyzing the regression equation, the optimal content ranges are found to be 7.5wt%–10.0wt% for V and 2.5wt%–4.5wt% for Cr, which corresponds to the alloys containing 9vol%–15vol% spheroidal VC carbides, 8vol%–16vol% M7C3, and a metastable austenite/martensite matrix. The wear resistance is 1.9–2.3 times that of the traditional 12wt% V–13wt% Mn spheroidal carbide cast iron.

Study on the Thermal Fatigue Behavior of Hot Deformed Wear Resistance Cast Iron and Effect of Carbide

The thermal fatigue behavior of wear resistance cast iron with different quantity of deformation has been investigated. The results show that eutectic carbide is the main location and passage for initiation and extension of thermal fatigue cracks, approving that the more serious, the carbide breaks. The higher thermal fatigue resistance of wear resistance cast iron will be and thermal fatigue fracture belongs mainly to brittleness.

Influence of RE on Carbide Morphology and Mechanical Property of Wear Resistant White Cast Iron

The influence of rare earths content on carbide morphology and mechanical properties of wear resistance of white cast iron was studied by means of metallographic examination,scanning electron microscopic examination and mechanical property test. The experiment results show that RE can change carbides from continuous network to isolated particles and improve the mechanical properties,especially in combination with proper heat treatment. The optimum properties of wear resistance of white cast iron modified by RE of 0.045% can be obtained by normalization at 960 ℃ for 2 h.

CARBIDE FORMATION IN AUSTEMPERED DUCTILE IRON ALLOYED WITH NICKEL AND COPPER

Carbide formation in austempered ductile iron (ADI) alloyed with Ni and Cu has been studied by use of TEM. The results show that η carbide precipitates in the bainitic ferrite when austempered at 350℃.for 6h, but no carbide was found at the austenite/.ferrite interfaces. When austempered at 300℃, two kinds of. s carbides appear in the bainitic ferrite when austempering time reached I h, and X carbide also precipitates at the austenite /ferrite interfaces when austempering time was extended up to 6h. The bainitic. ferrite and the retained austenite follow the Nishiyama- Wasserman relationship,

用后铁沟料加入量对Al_(2)O_(3)-SiC-C质浇注料性能的影响

为提高用后耐火材料的再利用率,以棕刚玉、用后铁沟料、白刚玉、碳化硅、α-Al_(2)O_(3)微粉、SiO_(2)微粉等为主要原料,制备了Al_(2)O_(3)-SiC-C质浇注料。探究了用后铁沟料加入量(加入质量分数分别为0、14%、28%、42%和56%)对浇注料性能的影响。结果表明,随用后铁沟料加入量的增加,浇注料的加水量显著增加,试样经1450℃保温3 h热处理后由膨胀转变为收缩,试样经110℃保温24 h及1450℃保温3 h热处理后的体积密度、常温抗折强度、抗侵蚀性能均呈现下降趋势,但当用后铁沟料加入量不超过28%(w)时,性能下降幅度较小。将用后铁沟料加入量为28%(w)的浇注料用于1080和1350 m3高炉铁沟支沟与渣沟,取得了良好服役效果,主体结构服役周期大于70 d。

高镍奥氏体球墨铸铁涡壳的铸造工艺优化

介绍了高镍奥氏体球墨铸铁涡壳铸件的结构及铸造工艺,针对试制过程中出现的表面缩孔、缩松、显微缩松以及组织中的碎块状石墨、表面恶化层、碳化物等问题进行了工艺优化,最后指出:(1)高镍奥氏体球墨铸铁液态收缩量大、石墨化膨胀弱,冒口设计遵循顺序凝固原则是防止涡壳产生缩孔、缩松缺陷的有效措施;(2)涡壳厚处和舌尖易形成碎块状石墨,强化孕育可防止缺陷的产生;(3)表面恶化层超标,可通过较高的残余镁量和砂芯刷涂料进行防止;(4)由于冷却速度较慢,舌尖部位碳化物析出数量较多,良好的孕育可减少碳化物析出量,热处理也可改变碳化物体积分数及其形态。