Corrosion Test of the Steel Plate in a WJ-8 Fastener for High Speed Rail

It was found that the steel plate in the composite plate in the WJ-8 fastener used in high speed rail is rusty. The objective of this study is to test the zinc coating of the steel plate. A literature review was conducted to identify the zinc coating techniques, and the companies that can provide different coating service was identified. A salt fog chamber was built that was in compliance with the ANSI B117 code, and the steel plates that were coated by the identified companies were tested using the salt fog chamber. The results indicated that the coating technique that had the best performance in preventing corrosion was the Greenkote plates with passivation. The galvanized option had the roughest coating layer, and it was the most reactive in the salt water solution. This makes it non-ideal for the dynamic rail environment because the increased friction of the plate could damage the supports, especially during extreme temperatures that would cause the rail to expand or contract. Greenkote with Phosphate and ArmorGalv also provided increased corrosion prevention with a smooth, strong finish, but it had more rust on the surface area than the Greenkote with ELU passivation. The ArmorGalv sample had more rust on the surface area than the Greenkote samples. This may not be a weakness in the ArmorGalv process;rather, it likely was the result of this particular sample not having the added protection of a colored coating.

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.

Effects of electrode configuration on electroslag remelting process of M2 high-speed steel ingot

The electrode configuration determines the thermophysical field during the electroslag remelting(ESR) process and affects the final microstructure of the ingot. In this work, ingot with a diameter of 400 mm was prepared with two electrode configuration modes of single power ESR process, namely one electrode(OE) and two series-connected electrodes(TSCE). Finite element simulation was employed to calculate the electromagnetic field, flow field and temperature field of the ESR system. The results show that the temperature of the slag pool and the metal pool of the TSCE process is lower and more uniform than that of the OE process.The calculated temperature distribution of the ingot could be indirectly verified from the shape of the metal pool by the experiment. The experimental results show that the depth of the metal pool in the OE ingot is about 160 mm, while the depth of the TSCE ingot is nearly 40 mm shallower than that of the OE ingot. Microstructural comparisons indicate that coarse eutectic carbides are formed in the center of the OE ingot, whereas more even eutectic carbides appear in the center of the TSCE ingot. In general, compared with the OE process, the TSCE process is preferred to remelt high speed steel ingots.

Effect of RE-Al-N on Structures and Properties of M2 Cast High Speed Steel

M2 cast high speed steel was inoculated by addition of rare earth(RE)-Al-N, network eutectic carbides were eliminated, matrix microstructures were refined and the segregation of tungsten and molybdenum elements was relieved. In the condition that the hardness does not decrease, impact toughness obviously increases. Quenching at 1180 ℃ and three-times tempering at 560 ℃, the hardness of M2 cast high speed steel is 65～66 HRC, and impact toughness reaches 21.3 (J·cm^(-2)). Modified M2 cast high speed steel has excellent thermal fatigue resistance and high temperature wear resistance. Roller made in modified M2 cast high speed steel has excellent service effect when it is used in slit rolling mill of hot rolling bar mill.

Study on stable and meta-stable carbides in a high speed steel for rollers during tempering processes

A high speed steel （HSS） was studied for rollers in this work. The steel was quenched at 1150℃ and tempered at 520℃. The phase structures of the steel were determined by X-ray diffraction （XRD）, and the hardness of specimens was measured. The volume fraction of carbides was counted by Image-Pro Plus software. The typical microstructures were observed by field emission scanning electron microscope （FESEM）. Stable and meta-stable carbides were deduced by removing the existing phases one by one in the Fe-C equilibrium calculation. It is found that the precipitated carbides are bulk-like MC, long stripe-like M2C, fishbone-like M6C, and daisy-like M7C3 during the tempering process. The stable carbides are MC and M6C, but the meta-stable ones are M2C, M7C3, and M3C.

Experimental research on electromagnetic continuous casting high-speed steel composite roll

A high speed steel composite roll billet was fabricated, which is regular in shape, smooth in surface, slight in trace, compact in internal structure, free of slag inclusion, shrinkage cavity, cracks and other flaws, and good in macro quality of junction surface using a vertical continuous casting machine. The interface zone microstructure of bimetallic in billet of high speed steel composite roll was analyzed by metallurgical microscope(OM), X-ray diffractmeter(XRD), scanning electron microscopy(SEM) and energy-dispersive X-ray analysis(EDS). The results indicate that the microstructure of roll billet is composed of chilled solidified layer, dendrite zone, interfacial zone of bimetal and core material zone. The microstructure of outer shell material is composed of martensite + bainite + residual austenite + some small labyrinth-shape, small-short lath-shape, or dollop-shape eutectic carbides. The microstructure of core material is slice-shape pearlite and a little ferrite along boundary of cells. The interface region microstructure of bimetallic composite roll consists of diffusion region, chilled solidified layer and columnar grain region.

PREDICTION OF FLOW STRESS OF HIGH-SPEED STEEL DURING HOT DEFORMATION BY USING BP ARTIFICIAL NEURAL NETWORK

The hot deformation behavior of TI (18W-4Cr-1V) high-speed steel was investigated by means of continuous compression tests performed on Gleeble 1500 thermomechan- ical simulator in a wide range of tempemtures (950℃-1150℃) with strain rotes of 0.001s-1-10s-1 and true strains of 0-0. 7. The flow stress at the above hot defor- mation conditions is predicted by using BP artificial neural network. The architecture of network includes there are three input parameters:strain rate,temperature T and true strain , and just one output parameter, the flow stress ,2 hidden layers are adopted, the first hidden layer includes 9 neurons and second 10 negroes. It has been verified that BP artificial neural network with 3-9-10-1 architecture can predict flow stress of high-speed steel during hot deformation very well. Compared with the prediction method of flow stress by using Zaped-Holloman parumeter and hyperbolic sine stress function, the prediction method by using BP artificial neurul network has higher efficiency and accuracy.

Semi-solid Casting of High Speed Steel Ingots Using Inclined Slope Pre-crystallization Method

Semi-solid casting of M2 high speed steel ingots was investigated by inclined slope pre-crystallization method. Effects of casting temperature and slope length on the microstructure of M2 HSS ingots were investigated. M2 cast ingots of non-dendritic primary austenite and fine eutectic ledeburite network carbide structure were obtained, with the casting temperature, slope length and angle of 1480 ℃, 500 mm and 60° respectively. Meanwhile, the microstructure of cast samples was quantitatively assessed by Image tool software. Results show that optimum mean equivalent diameter of primary austenite crystal grain is 50.8 μm, shape factor is 0.83, and mean thickness of network carbide is 5.21 μm.

The Effect of Intensity Pulsed Ion Beam Irradiation on Wear Resistance of High-speed Steel

The structural and phase transformations occurring in the near-surface layers of pre-quenched W6Mo5Cr4V2 high-speed steel (HSS) subjected to intensity pulsed ion beam (IPIB) melting have been investigated. The effect of IPIB irradiation on wear resistance of the HSS has also been studied. The IPIB consists mainly of Cn+(30%)^0 H+(70%), with a high beam current density of 80A/cm2, acceleration voltage of 250kV, pulse duration of 70 ns. Samples were bombarded with 1, 3, 5 pulses respectively. It has been revealed that after IPIB irradiation the initial martensite in the near-surface layer of HSS changed into austenite and produced residual stresses by using electron microscopy and X-ray diffraction. Redistribution and interlace of dislocations in the irradiated samples were generated under the impact of shock wave. With increasing pulse times gradual liquid-phase dissolution of M6C carbide particles occurs in the near-surface layer and produces nanocrystalline MC. This process results in the decrease of martensite crystal (a-phase) and increase of austenite (y-phase) content and the dispersed carbide. Wear resistance of the HSS is improved by a factor of 2, which is explained by the formation of metastable phases such nanocrystal and residual stresses and the redistribution and interlace of dislocations.

Microstructure and forming characteristics of spray-formed M42 high speed steel

M42 high speed steel （HSS）, a high grade alloy, was produced using the spray forming technology. Optical metallography （OM）,X-ray diffraction （XRD） and scanning electron microscope （SEM） were used to investigate the microstructures of the as-sprayed M42 HSS and the as-atomized powders. It is found that as-sprayed M42 HSS is composed of martensite, retained austenite and carbides. The grain size, as well as the morphology, size and distribution of the carbides have been greatly improved compared with those of the as-cast M42 steel （ a traditional process）. The size of the powder obtained at a high cold speed was ranged from 50 μm to 100μm in diameter. Its representative microstructures include dendrite, dendritic fragments, a mixture of dendrites, equiaxed grains and dendritic fragments,and equiaxed grains. The rapid solidification in the spray forming is a key factor to cause the refinement of the M42 HSS.

Development and Application of Die-Casting High Speed Steel Rolls

Due to its high hardness,good red hardness and excellent wear resistance at high temperature,high speed steel(HSS)is fit for the roll manufacture.In order to overcome the segregation of centrifugal casting of HSS roll,die-cast processes were developed and its effects on the properties of the HSS roll were investigated.It was found that pressure,pressing time and speed are three important factors affecting shrinkage cavity.For pouring temperature of 1 400-1 450 ℃,pressure of 150-160 MPa,pressing time of 120-150 sand pressing speed of 14-16mm/s,a compact HSS roll was obtained,which has no segregation and small working allowance.In the high speed wire rod rolling mill,service life of the HSS roll is 5to 8times longer than that of high nickel chromium infinite chilled cast iron roll.

Structures and Properties of High-Carbon High Speed Steel by RE-Mg-Ti Compound Modification

The effects of rare earths(RE)-Mg-Ti compound modification on the structures and properties of high-carbon high speed steel(HSS) were researched.The impact toughness(α_k),the fracture toughness(K_(1c))and threshold of fatigue crack growth(ΔK_(th))are tested.The thermal fatigue test is done on a self-straining thermal fatigue tester,the wear test is done on a high temperature wear test machine.The results show that the matrix can be refined by the RE-Mg-Ti compound modification,the eutectic carbides are inclined to spheroidicize and are distributed evenly,the morphology and distribution of eutectic carbides are improved by appropriate RE-Mg-Ti complex modification.After RE-Mg-Ti compound modification,a little effects can be found on the strength,hardness and red hardness,but the fracture toughness(K_(1c)) and threshold of fatigue crack growth(△K_(th)) are improved in the meantime,the impact toughness (α_k) is increased by over one time,and the resistance to thermal fatigue and wear resistance at an elevated temperature are remarkably improved.

High Speed Steel and WC Particle-Reinforced Composites Produce by Spray Forming

The process of spray forming utilized to fabricate WC particle-reinforced high speed steel composites has been studied. In addition, microstructures and mechanical properties of M2 high speed steel and its composites made by spray forming have been analyzed. The results show that the primary carbides of high speed steel are of two types: MC and MbC. With the increase in flight distance, the morphology of the primary carbides varies from fine fish-bone-like to islandlike and both bending strength and hardness increase. With the increase in volume fraction of WC reinforcement particles,hardness of the composites increases considerably, but bending strength, however, appears to be a decreasing tendency.

ELECTRON MICROSCOPE STUDY ON δ-EUTECTOID IN HIGH SPEED STEEL

The morphology and structure of δ-eutectoid and the transformation of δ-eutectoidic austenite in high speed steel have been studied under SEM and TEM.The δ-eutectoid in as-cast high speed steel is rod-shaped eutectoidic units with different orientations and is markedly surrounded by carbide shell.The eutectoidic carbide is rod-shaped M_6C of square eross section.The eutectoidic austenite may transform into pearlite structure during cooling.

A new composite:spray-deposited M2 high speed steel reinforced by WC particles

The fabrication of the high speed steel matrix composites reinforced by WC particles utilizing the ultrasonicgas atomization and spray-deposition was studied. The change of microstware and mechanical Properties of thecomposites added WC Particles were investigated and analyzed as well. As some results, the WC particles exhibit tWomorphologies (spherical and angular) with different content of WC particles; and with the increase of content of WCparticles, the hardness of the composites increases, yet the bending strength appears a trend of decreasing.

Microstructure simulation of rapidly solidified ASP30 high-speed steel particles by gas atomization

In this study, the microstructure evolution of rapidly solidified ASP30 high-speed steel particles was predicted using a simulation method based on the cellular automaton-finite element （CAFE） model. The dendritic growth kinetics, in view of the characteristics of ASP30 steel, were calculated and combined with macro heat transfer calculations by user-defined functions （UDFs） to simulate the microstructure of gas-atomized particles. The relationship among particle diameter, undercooling, and the convection heat transfer coefficient was also inves- tigated to provide cooling conditions for simulations. The simulated results indicated that a columnar grain microstructure was observed in small particles, whereas an equiaxed microstructure was observed in large particles. In addition, the morphologies and microstructures of gas-atomized ASP30 steel particles were also investigated experimentally using scanning electron microscopy （SEM）. The experimental re- suits showed that four major types ofmicrostructures were formed： dendritic, equiaxed, mixed, and multi-droplet microstructures. The simu- lated results and the available experimental data are in good agreement.

MICROSTRUCTURE OF LASER MELTED-RESOLIDIFIED LAYER ON HIGH SPEED TOOL STEEL

The laser melted-resolidified processing on W18Cr4V high speed tool steel has been made us- ing a 1 kW CO_2 continuous wave laser device.The microstructure of the laser melted- resolidified layer has been examined by optical microscopy and transmission electron microscopy(TEM).It was characteristic of extremely fine dendrite in the laser melted- resolidified layer and δ-ferrite in bulk form in the center of dendrite.The predominant twin martensite and a little dislocation martensite existed in the dendrite.The thin plate-like M_(213)C_6 carbide precipitated coherently on the twin martensites along their twin plane.There were both austenite rich in W,V and Cr and M_6C carbide in the interdendritic regions.

On microstructure and performance of tempered high-boron high-speed steel roll

Influences of the tempering temperature on the microstructure, mechanical property and wear resistance of High-Boron High Speed Steel （HBHSS） roll materials were investigated by means of optical microscopy, scanning electron microscopy （SEM）, X-ray diffraction, hardness measurement, impact tester, tensile tester and pin abrasion tester. The results show that the as-cast structure of HBHSS consists of a great amount of martensite and M2（B,C） and a few retained austenites and M23（B,C）6. After solution treated at 1,050℃ and followed by oil cooling, the amount of M23（B,C）6 carbo-borides in quenched HBHSS increases obviously and the macrohardness of the quenched HBHSS is 66 HRC, which is very close to the 65.8 HRC of as-cast HBHSS. On the whole, the hardness of HBHSS alloy shows a trend of slight decrease with increasing tempering temperature when tempered below 500 ℃. While when above 500 ℃, the hardness increases slightly as the tempering temperature increases and reaches a peak at 525 ℃ and then decreases obviously. The impact toughness of HBHSS has a tendency to increase as the tempering temperature increases. Tempering can improve the tensile strength and elongation of HBHSS, but a higher tempering temperature causes a slight decrease in both tensile strength and elongation. Excellent wear resistance can be obtained by tempering at 500 to 550 ℃.

Study on high speed tension property of B-grade bulletproof steel

In this paper, the high speed tension experiments have been performed on ultra high strength bulletproof steel. The specimen were cut from B-grade bulletproof steel sheet after hard-module quenching with thickness of 2.3 mm. The mechanical properties at strain rates of 0.001 s^-1, 0.01 s^-1, 0.1 s^-1 and 1 s^-1 were carried out on MTSS10, while those at higher strain rates of 200 s^-1, 500 s^-1 and i 000 s^-1 were tested on HTM5020 high speed tension tester and Hopkinson bar. The data from the high speed tension experiments were fitted via Johnson-Cook constitutive equation, and the fracture surface of each specimen was analyzed by scanning electron microscope （SEM）. The results indicate that, the shoot resistance capability of bulletproof steel is closely related to its strength, thickness and flow behaviors under high strain rate. The shoot resistance will be improved in the case of higher strength and better matching between strength and elongation. The Johnson-Cook constitutive equation fitted via experimental data provides fundament to numerical simulation. With the increase of strain rate, the size and depth of dimple trend to decrease and the depth of dimple changes less in steel with lower strength and higher elongation. The SEM analysis of fracture aspect is of benefit for further understanding of deformation and fracture mode under high strain rate.

Development of Centrifugal Cast High Speed Steel Roll with High Wear Resistance for Pre-Finishing Stands of a Hot Rod-Wire Mill

The present study aims at developing high speed steel (HSS) as roll materialsto replace traditional roll materials such as the alloy cast iron and powder metallurgical (PM)hard alloy, because low-cost alloy cast iron rolls have poor wear resistance and the cost ofhigh-quality PM hard alloy rolls is too high to be accepted by some users. By means of a centrifugalcasting method, HSS rolls with excellent wear resistance have been developed. Its hardness is 65-67 HRC, and its variation is smaller than 2HRC; its impact toughness excels 15J/cm^2. Usingpre-finishing stands of a high-speed hot wire-rod rolling mill, the wear rate of HSS rolls per onethousand ton of steel is 0. 25mm. However, the manufacturing burden of HSS rolls is obviously lowerthan that of PM hard alloy rolls; it is only 30% of that of PM hard alloy rolls.