新一代高速线材核心装备技术的研究与开发

分析了高速线材轧制装备技术的现状及发展趋势,对传统的集中传动与前沿的独立传动线材高速轧制工艺装备技术进行了对比分析,并针对机组传动型式、孔型设计、速降及微张力、控制冷却模型及机组模态等问题进行了分析和研究。提出了基于双模块的独立传动高速线材生产装备技术,创新性地开发了以独立双模块为主要技术特色的新一代高速线材核心装备技术,简化了设备结构,提高了高速线材生产的灵活性,并降低了生产能耗及投资成本。     

Niobium-Alloyed high speed steel by powder metallurgy

A philosophy for the use of strong carbide formers like niobium in high speed steels is described. It follows the concept of independently optimizing the compositions of the matrix (for maximum secondary hardening potential) and the volume fraction of the blocky carbides (for protection against abrasive wear). Normally, the two are interdependent through the action of the solidification equilibria, but separate control becomes possible when the blocky carbides are formed by a strong carbide former such as niobium. During normal ingot solidification, such strong carbide formers would produce very large primary carbides. This can be avoided by atomization and powder metallurgical processing. In this way, a steel has been produced whose matrix composition is similar to that of AISI M2, and whose primary carbides are all of NbC type. Its composition is 1.3C, 2W, 3Mo, 1.6V, 3.2Nb (wt pct). Because of its high stability, NbC is a much more effective obstacle to grain growth than the normal high speed steel carbides, and this allows substantially higher austenitization temperatures to be used. Despite its leaner composition, the Nb-alloyed steel matches the cutting performance of AISI M2, and its secondary hardening seems to be more persistent at high temperatures.     

Quantitative metallography of high speed steels by SEM

Secondary electron imaging in SEM offers a suitable combination of contrast, resolution and speed for quantitative metallography of high speed steels. To avoid distortion of measurements by topographic effects, plane polished specimens are used in the unetched state and imaged by chemical (atomic number) contrast. The optimization of primary beam parameters and photographic contrast are discussed. It has been found that the chemical contrast of carbide phases can be substantially enhanced (and further differentiated) by coatings of ZnSe and other semiconducting substances around 60 nm thickness. Applications are exemplified by the determination of matrix compositions from the overall alloy content and the amounts of alloy elements contained in the massive carbides, and by the effect of hot work and austenitization temperature on the size distribution and volume fraction of massive carbides in Fe—6W—5 Mo—2 V (AISI M2) high speed steel.     

高速钢轧辊在棒材生产线上的应用

介绍了高速钢轧辊的特性以及优点,并通过对西林钢铁集团轧钢总厂三轧作业区全连续棒材生产线在高速钢轧辊使用过程中,使用条件、事故处理以及使用效果等方面的总结,介绍高速钢轧辊的应用前景与效益。     

The high temperature transformation of high speed steel

Low tempered hardnesses on high speed steels which had been hardened in vacuum or atmosphere furnaces and gas quenched led to a search for a reaction occurring above 1400°F and probably initiated as a result of the slower cooling rate of the gas quench. A standard TTT evaluation was carried out on Ml, M2 high carbon, M3, and M7 high speed steels, quenching from conventional hardening temperatures, into salt baths maintained at 2000° to 1500°F. Examination of these specimens indicated the presence of a reaction occurring at all temperatures investigated but having its maximum rate at 1700° to 1800°F. The reaction involved precipitation of an MoC/Mo₂C carbide at grain boundaries and within the grains, with the amount of precipitate increasing with time. The precipitation of MoC/Mo₂C is directly related to the loss in tempered hardness and apparently causes this effect by 1) reducing precipitation hardening on tempering, 2) drastically lowering retained austenite contents, and 3) reducing as-quenched hardnesses.     

烧结硬化钢高速高扭矩齿轮的开发

烧结硬化使粉末冶金零件可在一般烧结炉的冷却带进行硬化，而不需要在烧结后进行热处理。为开发用于可再充电的电动工具用的高速、高扭矩齿输，试验了掺加有2．0％Cu与0．90％石墨的预合金化粉末ATOMET 4701(0．45Mn-0．45Cr-0．9Ni-1．0Mo)。将零件生坯压制到密度6．85g／cm^3，在1120℃下于吸热性煤气气氛中烧结30min。烧结态零件(密度6．80g／cm^3)的表观硬度为37HRC。显微组织分析表明，在烧结炉冷却带充分产生了马氏体相变。随后，零件在180～210℃下回火0．5～4h。在180℃回火2h后，烧结硬化材料的力学性能与齿输齿的精度处于最佳结合状态，优于经热处理的烧结低合金钢材。     

用连续浇注外层方法生产高碳高速钢复合轧辊的性能及其应用

近年来，对钢板质量要求日益提高，同时要求提高轧钢生产率、节约能源，因而轧制技术和设备取得长足进展。与此相应，开发了一种新的复合轧辊，它的外层是高碳高速钢，心部为锻钢。它是用新的连续浇注外层方法生产的。这种新的复合轧辊提高了轧钢生产率、改善了钢板的质量。     

Microstructure homogeneity of high speed steel M2 ingot by electroslag remelting

The homogeneity of the microstructure in M2 high speed steel ingot with a diameter of 400mm was studied by means of electroslag remelting process combined with numerical simulation. The microstructure differences between the center and the edge of the ingot were compared. The effects of local solidification time on eutectic carbides were discussed. The result shows that the size of the eutectic colonies varies from 100??m to 400??m near the center of the ingot, and lamellar eutectic carbides can reach a maximum thickness of tens of microns, and a length of more than 100??m. The maximum local solidification time is about 1300s at the center of ingot by calculation. Close to the edge of the ingot, the columnar crystals become small, and the size of eutectic colonies is among 50-200??m, and eutectic carbide lamellae are about 10??m in width, and tens of microns in length. The local solidification time at the edge of ingot is as short as 365s. When solidification of the ingot becomes quasi- steady state during electroslag remelting, the metal pool is pot- bottom- like. The pool depth is about 178mm by experiment, and the calculated pool depth is in accordance with that of experiment.     

Solidification of M2 high speed steel

The freezing process in AISI type M2 high speed tool steel (6 pct W, 5 pct Mo, 4 pct Cr, 2 pct V, 0.8 pct C) was studied by metallographic and thermal analysis techniques. Unidirectional solidification of small laboratory melts in a modified crystal growing apparatus was employed to provide metallographic sections of known macroscopic growth direction. Also cooling curves were obtained on 40 g specimens solidified in thimble crucibles. X-ray microradiography, electron probe scanning techniques, and quantitative microanalysis of dendrites and interdendritic carbides were extensively used to supplement conventional metallography. Carbon and vanadium contents of M2 were varied in order to observe the effect of an austenite and ferrite stabilizer on the thermal analysis curves and microstructure. The nonequilibrium freezing process in M2 includes three major liquid-solid reactions: 1) Liquid → Ferrite, 1435°C; 2) Liquid + Ferrite → Austenite, 1330°C; 3) Liquid → Austenite + M₆C + MC, 1240°C. These reactions account for the as-cast structure of the commercial alloy. The addition of carbon depresses the liquidus (1) and solidus temperatures (3) and narrows the gap between the liquidus (1) and peritectic transformation (2). This gap is eliminated at > 1.39 wt pct C, where the initial freezing reaction is the crystallization of austenite. The accompanying microstructural change is the elimination of σ eutectoid dendrite cores. The addition of vanadium promotes ferrite formation by strongly depressing the peritectic reaction and thus widening the gap between the liquidus and the peritectic.     

高速铁路用钢轨轧制工艺开发

针对高速铁路用钢轨高尺寸精度、高平直度的轧制特点，结合现有重轨生产存在问题，从孔型参数优化、导板结构设计开发、轧制调整技术开发、头部形状对应关系研究及轧制过钢量优化等方面开展工作，生产出了满足时速200公里铁路需要的钢轨。     

Design of steels for high speed machining

Abstract

Historical analysis of metal cutting shows that metal removal rates have been increasing in the course of the century, predicated by the advancement in tool materials but the steel design has lagged behind. This paper examines the mechanisms of chip formation and tool wear as a function of cutting speed in metal cutting. Chemical wear is identified as the dominant mechanism of tool wear at high cutting speeds caused by temperature rise due to shear localisation in the primary and secondary shear zones of chip. Shear localisation in the primary shear zone is shown to be influenced by both microstructural parameters, i.e. matrix hardening and second phase particles, and metal cutting variables, i.e. cutting speed (strain rate) and feed (pressure). Shear localisation in the secondary shear zone is caused by the tribological conditions of seizure at the tool/chip interface. Chemical crater wear is caused by the dissolution of tool into the workpiece (chip) by diffusion mechanism and can be prevented by suppressing the tribological condition of seizure. The design of steel for high speed machining is based on engineering glassy oxide inclusions in steel, which are designed to form a viscous layer in situ at the tool/chip interface at high cutting speeds. The viscous layer lubricates the tool/chip interface and prevents the occurrence of seizure, thereby suppressing chemical crater wear. In comparison with the large volume fraction of inclusions required for promoting ductile fracture at low cutting speeds, the amount of inclusions required for lubricating the tool/chip interface is very small and is in the range that is typical of clean steel. Thermodynamic modelling is shown to be a powerful tool to engineer glassy oxide inclusions in steel     

Microstructure characteristics of spray-formed high vanadium and cobalt high speed steel

The microstructure of high vanadium and cobalt high speed steel(high-V/Co HSS) and the morphology of its carbides were analyzed by optical microscope(OM),scanning electron microscope(SEM),electron probe microanalysis(EPMA),X-ray power diffraction(XRD),atomic force microscopy(AFM) and single phase erosion(SPE).The results suggest that the as-sprayed high-V/Co HSS has fine equiaxed grains(about 20 μm in size),which were homogeneously distributed.The carbides have two classical morphologies:one is fine particles(about 2 μm in size) distributed along the grain boundaries and the other is needle-like one,distributed on the grain boundaries.There are MC carbides,M2C carbides,M6C carbides and Cr2WC2 carbides in the as-sprayed high-V/Co HSS samples,however,in the as-cast high-V/Co HSS,there are MC carbides and Cr2WC2 carbides only.The SPE results show that there are two types of MC carbides in the as-sprayed HSS:the sphere one and the particle-like one.The former is about 2 μm in size and the latter is less than 1 μm,dispersed inside the grains,quite different from the MC carbides in the as-cast HSS.According to the AFM results,the skeleton-like M6C carbides of the as-sprayed high-V/Co HSS are embedded in the matrix along the grain boundaries.It is found that there are sharp membrane pieces on the carbides.Some small bamboo-shoot-like MC carbides grow from the matrix and are dispersed inside the grain.Those larger MC carbides are spherical particles embedded at the grain boundary junctions.     

Analysis of bulging for high speed continuous casting

In order to research the temperature distribution and mechanical deformation of slab bulging during high speed continuous casting,mathematical models have been developed to analyze the thermal and mechanical behavior of the slab.The thermal history of the slab has been predicted by a two-dimensional transient finite element heat transfer model,whose results serve as the input to the stress model.The stress model has been formulated for a two-dimensional longitudinal plane.In this case,the maximum tensile strain during the bulging process is located at the solidification front just past the top of the upstream roll,which may contribute to crack formation.The maximum tensile stresses are located at the cold surface in the middle of the two back-up rolls,just at the point of the maximum bulging.Stresses near the solidification front are small because of the high temperatures which produce lower elastic modulus values.Finally,the effect of the casting speed on the bulging deformation is discussed.     

高速机车齿轮用钢的研制

高速机车齿轮用钢为时速250km/h以上的高速机车牵引齿轮,是高档渗碳齿轮钢,具有高强度、高耐磨性、高的塑韧性,广泛应用于各类矿山、港口等工业用减速机、高速机车牵引齿轮等方面.黑龙江省冶金研究所自开发试制以来,对该钢种进行深入的研究,不断完善工艺,采用高功率电炉+LF炉外精炼+VD真空精炼及钢锭热送、轧制或锻造、退火工艺,工艺技术先进、质量性能稳定.     

高速过滤器的改进及运行效果

对八钢公司热轧厂浊循环水工艺中的主要水处理设备高速过滤器的运行结果进行了分析。认为高速过滤器存在设计缺陷。针对高速过滤器存在的问题,对其进行了改造。改造后,其出水水质显著提高,运行效果良好。     

激光熔覆无碳Fe-Co-Mo高速钢涂层的组织结构与性能

用水雾化合金粉末为原料,通过同步送粉式激光熔覆技术在40Cr基材上制备无碳高速钢涂层,对涂层的显微硬度、红硬性和抗回火稳定性进行测试和分析,研究工艺参数对涂层形貌及硬度的影响。结果表明,在适宜的参数下能够在基材表面获得无宏观裂纹和气孔的无碳高速钢涂层。涂层致密度高、稀释率低,与基体呈现出良好的冶金结合。涂层熔覆态下显微硬度(HV0.2)达到700,经过600℃下1 h时效后,涂层硬度(HV0.2)明显提升至900。经过4次600℃保温1 h的时效后,涂层硬度(HV0.2)保持在800。此外在600℃保温30 h的长时间回火后,涂层仍然可以保持硬度(HV0.2)达750,相较于常规高速钢ASP2030以及热作模具钢H13具有更加出色的抗回火能力。     

PCBN刀具高速精密切削W-Ni-Fe合金的性能研究

采用PCBN刀具对W-Ni-Fe合金进行高速精密切削试验,通过观测PCBN刀具前、后刀面的磨损形貌,分析了刀具的失效磨损机理;从CBN含量、刀具参数以及已加工表面粗糙度方面研究了PCBN刀具加工W-Ni-Fe合金的切削性能。结果表明,CBN含量高且刀尖圆弧半径大的PCBN刀具具有更长的使用寿命,在高速、低进给、小切深条件下可获得良好的表面质量。SEM和EDS分析结果表明,PCBN刀具高速精密切削W-Ni-Fe合金的磨损机理为粘结磨损、扩散磨损、局部剥落、氧化磨损以及崩刃磨损等多重磨损机理共同作用的结果。     

基于ANSYS的高速磨削中的砂轮破坏原因的研究

应用可视化数值模拟方法,借助于大型通用有限元软件ANSYS建立砂轮回转的数学模型,对离心应力进行了仿真研究.随着磨削速度的提高,磨粒的切削作用被磨粒对工件的高速冲击作用所取代.通过输入不同的转速对比,发现砂轮孔壁处所受切向应力σt最大,径向应力很小可忽略,而在砂轮外圆处切向应力较小.随转速提高,外圆切向应力增长趋势显著,破坏趋势也愈明显,因此切向应力是破坏的主要原因.这一虚拟分析既为砂轮实际应用中出现的破坏现象所佐证,又与砂轮受力分析结果相吻合,为磨削过程的安全奠定了良好的基础.     

T型结晶器抽锭电渣重熔高速钢90 mm方锭新工艺

 晶界处碳化物严重影响高速工模具钢的红硬性和耐磨性能,电渣重熔工艺能够有效地改善钢锭中碳化物尺寸及分布。传统电渣重熔生产较小钢锭的截面尺寸约为[?]200 mm,减小钢锭截面尺寸和增大冷却速率将会进一步减轻碳化物的偏析程度,但将降低生产效率、提高生产成本。采用双极串联、T型结晶器、抽锭电渣重熔新工艺生产90 mm方锭,并与相同熔化速度传统电渣重熔生产[?]200 mm钢锭进行对比试验。对钢锭成分、低倍、夹杂物、显微组织进行检验分析结果表明,90 mm方钢锭中碳化物尺寸和分布明显优于[?]200 mm钢锭,碳化物在后序锻造或轧制过程中更容易被破碎。新工艺电耗也低于传统电渣重熔工艺。