Effects of Different Calcining Temperatures on the Properties of Ceramsite Prepared by High-carbon Gasification Slag

The structure and characteristics of high-performance lightweight aggregates produced by high-carbon gasification slag were investigated by X-ray diffraction,scanning electron microscopy,thermogravimetry/differential thermogravimetr,differential scanning calorimetry-Fourier transform infrared,and mercury intrusion porosimetry,respectively.The experimental results show that the ceramsite undergoes two weightless stages in the calcining process.With the increase in the calcining temperature,a large number of pores are formed inside the ceramsite,its structure becomes denser,but the calcining temperature band of the ceramsite becomes narrow.The crystalline phase of the ceramsite changes at different calcining temperatures and the mineral phase changes from the earlieralbite,quartz,oligoclase,hematite,etc,to a silica-aluminum-rich glass phase.The 1130℃ is a more suitable calcining temperature,and the cylinder compressive strength of ceramics is 11.59 MPa,the packing density,apparent density,porosity,and water absorption are 939.11 kg/m^(3),1643.75 kg/m^(3),28.11%,and 10.35%,respectively,which can meet the standards for high-strength lightweight aggregates.

Spheroidization process in large-deformed high-carbon steel

In this study,the spheroidization process of large-deformed steel under various conditions was researched.Steel with a high carbon content （1.0％ C） was first treated thermomechanically using multipass rolling.Then it underwent spheroidization treatments at different heating temperatures,using various heating times and cooling rates.Spheroidization processes with a lower heating temperature,shorter heating time,or faster cooling rate than those of the traditional process all showed good results,indicating that the spheroidization process was promoted significantly by the large deformation process.Grain refinement and fragmentation of cementite,along with the large deformation process,promoted this spheroidization process.

Effect of RE-Modifier on Microstructure and Mechanical Property of High-Carbon Medium-Manganese Steel

The effect of RE-modifier on the microstructure and mechanical properties of high carbon-medium manganese steel has been investigated in present work.The results showed that the RE-modifier can refine the crystalline grain of high-carbon medium-manganese steel.The shape and distribution of carbides are improved and the columnar grains and phosphide in grain boundary are eliminated.Consequently,the impact toughness of the steel is increased by more than one time,compared with no addition of RE-modifier.

Can the low-carbon city pilot policy promote the upgrading of high-carbon emitting enterprises? Evidence from China

As a crucial environmental reform system to realize“carbon peaking”and“carbon neutrality”,the pilot policy of low-carbon cities(LCCs)puts pressure and challenges on high-carbon emitting enterprises(HCEEs)while providing opportunities for these firms to take the path of independent transformation.Employing the data of Chinese listed enterprises from 2006 to 2016 and adopting a difference-in-differences(DID)model,we evaluated the impact of LCC construction on the upgrading of HCEEs and its mechanisms.The results indicate that LCC construction enhances the upgrading of HCEEs in the pilot cities.The conclusions remain stable after a series of robustness tests.The mechanism analysis reveals that LCC construction triggers the upgrading of HCEEs by promoting resource allocation efficiency,R&D investment,and green technology innovation.The heterogeneity results indicate that this positive effect is more pronounced for HCEEs in regions with more stringent environmental law enforcement.This study also observes that the upgrading impact is more promi‐nent for state-owned enterprises,enterprises with higher bargaining power,and enterprises whose managers have a long-term vision.The above results provide directions for upgrading HCEEs and replicable evidence for cities in developing economies to fulfill the win-win target of environmental protection and economic transfor‐mation.

Patenting of hot-rolled high-carbon steel and its applications

The patenting process of three hot-rolled steels with carbon mass contents of 0.70%-0. 90% was studied. The effect of the quenching temperature on the cementite lamellar distance in the steel was evaluated on the basis of microstructural characterization and mechanical property tests. The patenting treatment of high-carbon hot- rolled strip and its application in springs were discussed.

Investigation of longitudinal surface cracks in a continuous casting slab of high-carbon steel

Based on a series of related investigations, a mechanism for the formation of longitudinal surface cracks on a continuous casting slab of high-carbon steel was investigated. High-temperature tensile tests performed on slab samples,metallographic and scanning electron microscopy studies, as well as heat flux and shell thickness in continuous casting predicted on the basis of a mathematical model were conducted. The results showed that high- carbon steel exhibited a much lower liquidus temperature and a wider brittle temperature range immediately after solidification compared with those of low-carbon steel. Concentrations of elements K and Na, which are contained in the mold fluxes, were not observed in the cracks during this study. The calculated results showed that the heat flux and the shell thickness were uneven along the mold width and that the shell was thinner and close to the center line of the slab surface. The longitudinal cracks were observed in situ using confocal laser scanning microscopy, to first occur close to the solidification front,where the ductility was extremely low;in addition ,the shell growth was slower than in other regions, which led to a thinner shell and depressed shrinkage owing to a lack of lubrication by the mold fluxes below the meniscus. Furthermore, the pouring temperature of high-carbon steel is - 100 ~C lower than that of low-carbon steel,so the formation of a stable liquid flux near the meniscus within a short time at the beginning of casting is difficult. The amounts of liquid slag film and crystalline slag film were insufficient to provide adequate lubrication between the shell and the mold, which resulted in greater friction force that induced or aggravated cracks. Therefore, the homogeneity of mold fluxes and initial solidification in the mold should be improved to reduce the concentration of slab surface defects.

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.

我国POE行业发展现状及应用前景展望

发展高端化工材料是我国从石化大国向石化强国迈进、助力高质量发展的必由之路。聚烯烃弹性体(POE)市场规模大、需求增速快且市场存在较大缺口,有望成为最具前景的高端材料之一。文章对POE的结构性能及特点进行了概述,分析了POE的下游消费结构及应用现状、产业供需格局,并从技术及价格方面探讨其竞争力,对其未来发展进行了展望。提出开发具有自主知识产权的催化剂及其配套工艺,拓展POE下游应用领域,是未来POE产业的重要发展方向。

Reaction mechanism between Al_(2)O_(3)–MgO refractory materials and rare earth high-carbon heavy rail steel

Submerged entry nozzle(SEN)clogging is a major problem affecting the production quality of rare earth steel,and finding a suitable refractory outlet can significantly reduce production costs.To explore the relationship between refractory composition and interface interaction,unprotected coated Al_(2)O_(3)–MgO refractories and SiO2-coated Al_(2)O_(3)–MgO refractories were added to rare earth high-carbon heavy rail steel under laboratory conditions,and the Al_(2)O_(3)–MgO refractory was found to be more suitable.The results show that,from the epoxy resin side to the refractory side,the contour of the refractory interface reaction layer can be divided into two main layers:an iron-rich reaction layer and an iron-poor reaction layer.Calculations based on the spherical model suggest that the adhesion force is proportional to the size of the refractory particles and inclusions,and the same result applies to the surface tension.Controlling the inclusions at a smaller size has a specific effect on alleviating the erosion of refractories.Combined with the erosion mechanism of Al_(2)O_(3)–MgO refractories,the interface reaction mechanism between Al_(2)O_(3)–MgO refractories and molten steel was proposed,which provides ideas for solving SEN clogging.

Spheroidization and Ostwald Growth of Carbide in Isothermal Process of Hot-Deformed High Carbon Chromium Cast Steel

In isothermal spheroidizing process,the spheroidization and growth of the carbide formed in hot-deformed high-carbon chromium cast steel at high temperature were investigated.The results showed that the spheroidizing growth of carbide proceeds in such a way that the bigger carbide particles swallow the smaller ones,and the short rhabdoid carbides dissolve and are spheroidized by itself.When the samples were held at 720℃ for more than 3 h,the spheroidization is not obvious.The feature of the process is the size increment and the amount decrement of carbide particles.The empirical equation for growth rate of carbides was obtained.The volume fraction of carbides keeps constant.The growth process agrees well with Ostwald Ripening Law.

Study on rolling process optimization of high carbon steel wire

The existing problems in the manufacture of SWRH82B high carbon steel wire were discussed by sampling and testing the microstructure and properties of the steel from the workshop. To solve the problems, the experimental parameters for thermal simulation were optimized, and the thermal simulating experiments were carded out on a Gleeblel500 thermal simulator. The process parameters for the manufacture were optimized after analysis of the data, and the productive experiments were performed after the water box in front of the no-twist blocks was reconstructed, to control the temperature of the loop layer. The results from the productive experiments showed that the cooling rate of 10-15℃/s was reasonable before phase transformation, about 5℃/s during phase transformation, and 600-620℃ was the suitable starting temperature for phase transformation. The ultimate strength of the Ф11.0 mm wire was increased to 1150-1170 MPa with an increase of 20-30 MPa, the percentage reduction of section was to 34%-36% with an increase of 1%-3% by testing the finished products after reconstruction.

CHARACTERISTICS OF MARTENSITE IN A HIGH CARBON FERROALLOY

Some characteristics of plate martensite in a 1.03% C ferroalloy have been studied by using the transmission electron microscopy.The habit plane of the plate martensite in this ferroalloy was found to be close to{224}_f.The morphology,distribution,coalescence and curving of martensite as well as the substructure in both martensite and austenite have been observed. The mechanism of both nucleation and growth of the martensite have been discussed.

Effect of cerium addition on non-metallic inclusions in a high-carbon chromium bearing steel

Effects of varied levels of cerium(28×10-6,65×10^(-6) and 150×10^(-6))on inclusions in a high-carbon chromium bearing steel at different stages(before adding cerium,after adding cerium for 1,5,10 min and ingot)were studied using laboratory experiments.An automatic scanning electron microscope system with energy-dispersive spectroscopy was used to analyze the amount,composition,size and morphology of inclusions in the steel at different stages.When the cerium content in the molten steel increased from 0 to 150×10^(-6),the evolution sequence of inclusions was as follows:Al_(2)O_(3)→CeAl11O18→CeAlO_(3)→Ce_(2)O_(2)S.After 28×10^(-6) cerium was added,Al_(2)O_(3) inclusions were modified into CeAl_(11)O_(18) inclusions in the molten steel and then were further transformed into Al2O3 and CeAlO3 inclusions in the solid steel during cooling.With the addition of 65×10^(-6) cerium,inclusions in the molten steel were modified into CeAlO_(3) and a small number of Ce2O2S inclusions.When the addition amount of cerium increased to 150×10^(-6),inclusions were transformed to Ce_(2)O_(2)S.The size of inclusions in the molten steel decreased obviously with cerium addition.On the other hand,the size of inclusions increased during the cooling process in solid steels of No.1 steel(with 28×10^(-6) cerium)and No.2 steel(with 65×10^(-6) cerium).During the cooling process,unmodified MnS inclusions were precipitated in the solid steel of No.1 steel and wrapped outside the Al2O3 and CeAlO_(3) inclusions to form large complex inclusions.During the cooling process of No.2 steel,the inclusion size of CeAlO_(3) increased due to the collision and polymerization.In the No.3 steel(with 150×10^(-6) cerium),the average size of inclusions decreased rapidly and remained at a lower size during the cooling process,which was beneficial to improving the fatigue life of the steel.

Effects of rare earth elements on inclusions and impact toughness of high-carbon chromium bearing steel

High-carbon chromium bearing steels with different rare earth (RE) contents were prepared to investigate the effects of RE on inclusions and impact toughness by different techniques. The results showed that RE addition could modify irregular Al2O3 and MnS into regular RE inclusions. With the increase of RE content, the reaction sequence of RE and potential inclusion forming elements should be O, S, As, P and C successively. RE inclusions containing C might precipitate in molten steel and solid state, but the precipitation tem perature was significantly higher than that of carbides in high-carbon chromium bearing steel. For experim ental bearing steels, the volume fraction of inclusions increased steadily with the increase of RE content, but smaller and more dispersed inclusions could be obtained by 0.018% RE content compared with bearing steel without RE, whereas the continuous increase of RE content led to an increasing trend for inclusion size and a gradual deterioration for inclusion distribution. RE addition could improve the transverse impact toughness and isotropy of bearing steel, and for modified highcarbon chrom ium bearing steel by RE alloying, the increase of RE content continuously increased both transverse and longitudinal im pact toughness until excessive RE addition.

Hybrid Friction Stir Welding of High-carbon Steel

A high-carbon steel joint,SK5（0.84 wt% C）,was successfully welded by friction stir welding（FSW）,both without and with a gas torch,in order to control the cooling rate during welding.After welding,the weld zone comprised gray and black regions,corresponding to microstructural variation：a martensite structure and a duplex structure of ferrite and cementite,respectively.The volume fraction of the martensite structure and the Vickers hardness in the welds were decreased with the using of the gas torch,which was related with the lower cooling rate.

Solid-Phase Decarburization of High-Carbon Ferromanganese Powders by Microwave Heating

The solid-phase decarburization of high-carbon ferromanganese powders （HCFPs） was investigated using calcium carbonate as the decarburizer by microwave heating and conventional heating methods to explore the differ-ences of microwave heating and conventional heating. Experimental results show that HCFPs containing calcium.car-bonate were heated up to 900, 1000, 1 100, and 1200 ℃ and held for 60 rain for decarburization by microwave heat-ing at decarburization ratios of 76.69%, 82.90%, 84.11%, and 85. 75%, respectively. These ratios are higher than the decarburization ratios used for conventional heating under the same experimental conditipns. The microwave heat- ing can significantly improve decarburization ratio. This indicates the microwave heating field features a non-thermal effect, which in turn, visibly enhances the carbon diffusion ability of HCFPs. It also improves the kinetic conditions of solid-phase decarburization.

A Transmission Electron Microscopy Study of Plate Martensite Formation in High-carbon Low Alloy Steels

The martensitic microstructures in two high-carbon low alloy steels have been investigated by classical and automated crystallographic analysis under a transmission electron microscope. It is found that the martensitic substructure changes from consisting mostly of transformation twins for 1.20 mass% carbon （C） steel to both transformation twins and planar defects on {101}M for 1.67 mass% C steel. In the 1.67 mass% C steel it is further found that small martensite units have a rather homogeneous substructure, while large martensite units are more inhomogeneous. In addition, the martensite units in both steels are frequently found to be of zigzag patterns and have distinct crystallographic relationships with neighboring martensite units, e.g. kink or wedge couplings. Based on the present findings the development of martensite in high-carbon low alloy steels is discussed and a schematic of the martensite formation is presented. Moreover, whether the schematic view can be applied to plate martensite formation in general, is discussed.

Effect of Austempering–Partitioning on the Bainitic Transformation and Mechanical Properties of a High-Carbon Steel

The 1.1C-1.5Si-1.1Mn1.4Cr-0.5Mo-0.6Al-0.6Co （in wt%） steel was treated, respectively, by isothermal austempering process and newly developed austempering-partitioning-tempering process （A-P-T）. After austempering at 250, 280 and 300 ℃ for 38, 20 and 10 h, respectively, the sample microstructures were composed of bainitic ferrite plates and film-like retained austenite with thicknesses between 60 and 150 nm. The highest tensile strength of 2003 MPa and hardness value of 53.9 HRC were obtained for the steel after austempering at 250 ℃ for 38 h, resulting from the combining effect of super-saturated martensite decarburization and stabilization of bainitic formation. After A-P-T treating （heated at 300 ℃ for 8 h following water cooling, and then heated at 300 ℃ for 2 h following air cooling）, bamboo leaf-like martensite, primary and secondary bainites and retained austenite were observed. The thickness of the secondary bainitic ferrite plates formed during partitioning is much smaller than that of the primary bainite formed during 300 ℃ austempering. Samples subjected to A-P-T treatment showed improvement in ductility compared to that subjected to austempering.

Solid-phase Decarburization Kinetics of High-carbon Ferromanganese Powders by Microwave Heating

Solid-phase decarburization of high-carbon ferromanganese powders （HCFPs） was conducted using calcium carbonate powders （CCPs） as a decarburizer by microwave heating. Solid-phase decarburization kinelSics was investi- gated by isothermal method. The results show that the HCFPs show excellent microwave absorption at a higher av- erage heating rate of 80 ℃/min, while CCPs exhibit poor microwave absorption at a lower heating rate of 5--20 ℃/min; the heating characteristics are in-between when HCFPs and CCPs are mixed. The average heating rates of the mix- ture are 32.14, 31.25, 31.43, and 30.77 ℃/rain when the mixture is heated up to 900, 1000, 1100, and 1200 ℃, respectively. The good microwave absorption property of the mixed material lays the foundation for the solid-phase decarburization of HCFPs containing CCPs. Solid-phase decarburization of HCFPs containing CCPs is a first-order reaction by microwave heating. Apparent activation energy of solid-phase decarburization is 55.07 kJ/mol, which is far less than that of ordinary carbon gasification reaction and that of solid-phase decarburization under the same de- carburization condition by conventional heating. It indicates that microwave heating not only produces thermal effect, but also has non-thermal effect.

Impacts of multiple laser shock processing on microstructure and mechanical property of high-carbon steel

Multiple laser shock processing （LSP） impacts on microstructures and mechanical properties were investigated through morphological determinations and hardness testing. Microscopic results show that without equal channel angular pressing （ECAP）, the LSP-treated lamellar pearlite was transferred to irregular ferrite matrix and incompletely broken cementite particles. With ECAP, LSP leads to refinements of the equiaxed ferrite grain in ultrafine-grained microduplex structure from 400 to 150 nm, and the completely spheroidized cementite particles from 150 to 100 nm. Consequentially, enhancements of mechanical properties were found in strength, microhardness and elongations of samples consisting of lamellar pearlite and ultrafine-grained microduplex structure. After LSP, a mixture of quasi-cleavage and ductile fracture was formed, different from the typical quasi-cleavage fracture from the original lamellar pearlite and the ductile fracture of the microduplex structure.