Study on the Interaction between Rare Earth and Carbon in High Carbon Steel

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Influence of Rare Earth Elements on Microstructure and Mechanical Properties of Cast High-Speed Steel Rolls

The influence of rare earth （RE） elements on the solidification process and eutectic transformation and mechanical properties of the high-V type cast, high-speed steel roll was studied. Test materials with different RE additions were prepared on a horizontal centrifugal casting machine. The solidification process, eutectic structure transformation, carbide morphology, and the elements present, were all investigated by means of differential scanning calorimetry （DSC） and scanning electron microscopy energy dispersive spectrometry （SEM-EDS）. The energy produced by crack initiation and crack extension was analyzed using a digital impact test machine. It was found that rare earth elements increased the tensile strength of the steel by inducing crystallization of earlier eutectic γ-Fe during the solidification process, which in turn increased the solidification temperature and thinned the dendritic grains. Rare earth elements with large atomic radius changed the lattice parameters of the MC carbide by forming rare earth carbides. This had the effect of dispersing longpole M C carbides to provide carbide grains, thereby, reducing the formation of the gross carbide and making more V available, to increase the secondary hardening process and improve the hardness level. The presence of rare earth elements in the steel raised the impact toughness by changing the mechanism of MC carbide formation, thereby increasing the crack initiation energy.     

稀土对60CrVA钢组织和性能的影响

用兴澄特钢生产的φ18 mm 60CrVA圆钢做原料,在25 kg真空感应炉中,进行了三炉添加稀土的试验.对钢的化学成分、气体含量、金相以及硬度、横向韧性、塑性等性能进行检验.稀土改变了钢中夹杂物形态和细化了珠光体片间距,提高了钢的韧性和冲击性能,有利于延长产品的使用寿命.     

碳、钒含量对高钒高速钢组织和力学性能的影响

在ωv/ωc≈3与ωv≈10%的条件下,研究了钒、碳含量对高钒高速钢组织和力学性能的影响.结果表明：高钒高速钢的耐磨性决定于硬度与组织.硬度低于HRC 57时,耐磨性主要决定于硬度;硬度超过HRC 57之后,耐磨性主要决定于碳化钒的数量、形态、分布与基体组织.ωv=8.15%～10.20%、ωc=2.70%～3.15%时,经适当变质处理和热处理,可使团球状或团块状的碳化钒均匀分布在经1 050 ℃淬火,550 ℃回火的坚硬基体上,从而获得优良的耐磨性能.     

Effects of Rare Earth,Titanium, and Magnesium Additions on Microstructures and Properties of High-boron Medium-carbon Alloy

In order to improve the toughness and wear resistance of high-boron medium-carbon alloy(HBMCA),a novel wear-resistant HBMCA comprising granular borocarbide was obtained by titanium,magnesium,and rare earth modifications.These modifications gave rise to greatly refined as-cast eutectic borocarbide structures and a less interconnected continuous borocarbide network.Heat treatment mostly produced broken and spheriodized borocarbides that tended to exist as isolated particles in modified HBMCA.The heat treated modified HBMCA exhibited enhanced hardness than pristine and impact toughness was improved significantly to 12.5J/cm~2.In addition,it displayed 2.39 and 1.7times greater wear resistance than high-speed steel(HSS)and high nickel-chromium alloy steel(Cr25)at high temperature(500℃),respectively.Here,the modification mechanisms involving Re_2O_3,TiN,and MgO/MgS heterogeneous nuclei were discussed.     

Effect of Mischmetal on As-cast Microstructure and Mechanical Properties of M2 High Speed Steel

High speed steel has been widely used in various fields due to their excellent red hardness and good wear resistance.However,the influence of mischmetal(Ce-La)on the as-cast microstructures and mechanical properties of high speed steel has rarely been reported.Thus,the microstructure and mechanical properties of M2 high speed steel with addition of mischmetal(Ce-La)were investigated.The morphology and distribution of the eutectic carbides of the steel were observed by using optical microscopy and scanning electron microscopy,and the impact toughness and bending strength were tested.The results show that adding mischmetal has an obvious effect on the microstructure and mechanical properties of M2 high speed steel.The coarse eutectic structure is refined,the weak connection of the carbide networks is broken and the flake carbides become short and fine.More networks of eutectic carbides dissolve into the matrix.When a suitable adding content of mischmetal is selected,for example,0.3mass%,the impact strength and bending strength can increase by 27% and 10.76% compared with that without mischmetal,respectively.     

稀土对高速钢堆焊层组织与性能的影响

本文研究了稀土合金对高速钢Ｗ_（１８）Ｃｒ_４Ｖ堆焊层微观组织，力学性能和耐磨性的影响。结果表明，在焊条药皮中加入适量的稀土合金，在焊态下能使高速钢堆焊金属中的共晶碳化物由连续网状，粗大骨骼状（莱氏体）转变成孤立、细小的不规则块状；冲击韧性提高１５２％，耐磨性提高４７～１０９％。并对稀土所起的作用进行了分析讨论。     

高碳高速钢轧辊制造工艺研究现状及展望

轧钢工业的发展对轧辊性能提出了更高的要求 ,为适应这一要求 ,开发了高碳高速钢轧辊。普通铸造方法制造高碳高速钢轧辊 ,组织粗大 ,共晶碳化物呈网状分布 ,韧性低 ,抗疲劳性能差 ,使用寿命短。变质处理和电磁搅拌是改善钢铁材料组织和性能的重要手段 ,对高碳高速钢进行变质处理和电磁搅拌研究 ,有望明显改善其组织和性能 ,为普通铸造方法制造高性能高碳高速钢轧辊奠定基础。     

RE-Ti复合变质对高钒高速钢组织和性能的影响

研究了RE-Ti对高钒高速钢铸态组织、热处理组织和性能的影响.结果表明,变质处理使高钒高速钢共晶碳化物的形貌和分布得到了改善,共晶组织中片层状碳化物变短、变细.热处理后,共晶碳化物大部分变成团球状且分布均匀.变质剂中的合金元素可促进晶粒中或沿晶界均匀分布的非连续状硬质碳化物的生成,从而达到改善组织、提高硬度的作用.并分析了变质剂在高钒高速钢中的作用机理及改善合金性能的机制.     

高镧稀土添加剂在16Mn钢中的应用

针对高镧稀土添加剂对16Mn钢的夹杂物、力学性能的影响进行分析研究,并与富铈稀土添加剂进行对比.实验表明,高镧稀土添加剂能有效变质16Mn钢中的夹杂物,减少夹杂物的数量,改善钢的力学性能.当La/S(质量比)为2.5时,综合力学性能达到最佳值.高镧稀土添加剂能有效替代富铈稀土添加剂进行稀土钢的开发.     

Effect of Rare Earth Fluoride Complex Additives on Properties of Steel

A technique of treating steel with rare earth fluoride complex additives(REFCA),effects andinflunce factors have been studied.REFCA play a role on controlling inclusion morphology,purifying themolten steel and improving properties of steel.The optimum composition of REFCA is REF_3 42%;CaO33%;SiCa 25%,and the amount of REF_3 is 0.5 wt%～0.6 wt% of steel.     

夹杂物对稀土金属丝塑性和韧性的影响

稀土金属中的酸不溶物是影响其塑性、韧性的重要原因,将所述酸不溶物含量限于一定水平,则能保证稀土金属合格的塑性和韧性.     

New Spheroidizing Technique of Ultra-High Carbon Steel With Aluminum Addition

A new spheroidizing process of ultra-high carbon steel （UHCS） containing C 1.55%, Cr 1.45%, and Al 1.5% in mass percent has been proposed. The effect of processing parameters on the microstructure was analyzed. The UHCS produced by this new process has a microstructure with recrystallized ferrite matrix and fine and uniform carbide particles. After this spheroidizing, the UHCS exhibits good mechanical properties at ambient temperature, for example σb= 1 100 MPa, σs =915 MPa, δ=8% and high ratio of σs/σb.     

碳含量对高速车轮用钢综合性能的影响

研究了碳的质量分数在 0 .4 %～ 0 .7%的范围内变化时对高速列车车轮用钢综合性能的影响。结果表明 ,随着碳含量的增加 ,试验钢的耐磨性能和接触疲劳性能提高 ,而冲击韧性及抗冷热疲劳性能降低 ;在 880℃正火 5 30℃回火的热处理条件下 ,碳的质量分数为 0 .5 %并添加少量合金元素的试验钢 ,具有良好的强韧性匹配 ,特别是抗冷热疲劳和抗接触疲劳性能良好 ,并兼有较好的耐磨性能 ,综合性能优良 ,较适宜于生产具有抗剥离性要求的高速车轮钢。     

掺杂稀土的高速钢预合金粉对WC基钢结硬质合金组织和性能影响

钢结硬质合金是一种性能介于硬质合金与高速合金钢的材料,可以取代部分传统硬质合金与工模具钢在模具和切削刀具领域的应用。本研究采用气雾化法制备稀土掺杂高速钢预合金粉作为钢结硬质合金的粘结相,制备了掺杂稀土的WC基钢结硬质合金,用扫描电子显微镜观察了样品的显微组织和断口形貌,并对合金的密度、硬度、抗弯强度和冲击韧性进行了检测。研究结果表明,在高速钢预合金粉中掺杂稀土元素能提高WC基钢结硬质合金的密度,改善其硬度、抗弯强度、冲击韧性等力学性能;添加Ce元素的效果好于Y元素;采用掺杂稀土元素Ce的高速钢预合金粉制备的WC基钢结硬质合金力学性能优于传统球磨混料法掺入稀土元素Ce制备的WC基钢结硬质合金。     

高磷稀土精矿的碳热还原过程研究

采用63kVA直流矿热炉,对高磷稀土精矿直接进行碳热还原,制备高品位稀土硅化物合金。冶炼过程中生成的废渣很少,炉底不上涨,炉内碳热还原反应进行得较为彻底,稀土几乎全部进入产品合金当中。同时,对稀土精矿中的主要有害杂质磷在冶炼过程中及在矿热炉内的行为进行了深入的研究,提出了最大限度减少磷进入产品合金的策略。实验得到的稀土硅化物合金具有独特的组织结构,与众不同的抗水化性,其粉化特性也与传统观点有较大的差异。     

Influence of Rare Earth on Property of Low Chromium Semi-Steel

Itisnoticeablethatthelowchromiumsemi steelhashighhardnessandabrasionresistance[1] .However,thematerialhaslowductility ,owingtothereticulatedistributionofcarbide ,whichrestrictsitsapplications .Therefore ,itisnecessarytoim provethecomprehensivepropertiesforpotentialap plications .Thecomprehensive propertiesoflowchromiumsemi steelcanbeimprovedbyaddingrareearths (RE)becauseREcanchangethemorphologyofcarbideandnon metallicinclusions ,refinegrainsize,purifyandstrengthen grainboundaryandsoon[2 -5] …     

Effects of Rare Earth and Alkaline Earth on Spheroidizing of Eutectic Carbides in Low Tungsten White Cast Iron

Tungsten Alloy White Cast Iron(TAWCI) has great brittleness and narrow application scope. The influences of Rare earth element(Ce) and alkaline earth elements ( K, Na) on the microstructures and performances of TAWCI were researched, and the idea estimating spheroidizing effect of carbides using Circular Degree (C. D) were put forward. The result shows that eutectics carbide tums into sphericity from network after modification, and carbide is refined and uniformly distributed and the C. D of eutectic carbide increases. The mechanism of carbide spheroidizing was analyzed. The impact toughness and wear resistance of TAWCI obviously improve with the rise of C. D of carbides.The service life of modified TAWCI roll is 35 % higher than that of high chromium cast iron roll, and its production cost is reduced by 25 %.     

W9高速钢的电磁连续铸造研究

 研究了W9高速钢的电磁连续铸造工艺和铸坯的凝固组织特征,并与普通的模铸高速钢中共晶碳化物的类型和分布情况进行了比较,测定了在不同制备条件下高速钢莱氏体网的厚度和凝固冷却速度。结果表明：电磁连续铸造得到的高速钢铸坯表面光滑、振痕轻微、外观形状规整、内部组织致密无缺陷,莱氏体网明显变薄,晶粒明显细化;M2C和MC型碳化物的析出量增多,M6C型碳化物的析出量减少,合金碳化物变得细小、均匀和弥散;铸坯边部的凝固冷却速度为3.4×104 K/s,r/2处为6.5×103 K/s,心部为3.9×102 K/s,冶金质量明显优于普通模铸。     

Breakdown Behavior of Eutectic Carbide in High speed Steel during Hot Compression

 The evolution of eutectic carbide in as-cast M2 high-speed steel on different deforming conditions was investigated. Initially, specimens were deformed by hot compression in the range of 1223 to 1398K at strain rates of 0.01 to 1.0s-1. In a series of continuous deformation tests the flow stress curves were determined for the downstream process simulation. Subsequently, metallographic examination was carried out before and after deformed specimens for carbides analysis. As-cast microstructure is characterized as a spherical matrix of austenite and a continuous network of rodlike or irregular eutectic carbide, whereas deformed microstructure has broken carbide network and smaller granular products on all experimental conditions. It suggests that eutectic carbides fracture to particles during hot deformation by thermomechanical disintegration, while diffusion-controlled phase transformation was not remarkable. Combination with numerical simulation, the relationship between breakdown ratio of carbide network and deforming parameters were concluded. Strain was the most important one to shatter eutectic carbides and disperse products. Furthermore, critical strain values were obtained, beyond which carbide network disappeared, and fractured carbides kept a stable profile and deformed with matrix coordinately. A higher temperature or lower strain rate resulted in a lower critical strain.