Prediction and optimization of flue pressure in sintering process based on SHAP

Sinter is the core raw material for blast furnaces.Flue pressure,which is an important state parameter,affects sinter quality.In this paper,flue pressure prediction and optimization were studied based on the shapley additive explanation(SHAP)to predict the flue pressure and take targeted adjustment measures.First,the sintering process data were collected and processed.A flue pressure prediction model was then constructed after comparing different feature selection methods and model algorithms using SHAP+extremely random-ized trees(ET).The prediction accuracy of the model within the error range of±0.25 kPa was 92.63%.SHAP analysis was employed to improve the interpretability of the prediction model.The effects of various sintering operation parameters on flue pressure,the relation-ship between the numerical range of key operation parameters and flue pressure,the effect of operation parameter combinations on flue pressure,and the prediction process of the flue pressure prediction model on a single sample were analyzed.A flue pressure optimization module was also constructed and analyzed when the prediction satisfied the judgment conditions.The operating parameter combination was then pushed.The flue pressure was increased by 5.87%during the verification process,achieving a good optimization effect.

Study of high pressure sintering behavior of CBN composites starting with CBN-Al mixtures

Cubic boron nitride(CBN) composites starting with CBN-Al mixtures were sintered on WC-16 wt%Co substrate under static high pressure of 5.0 GPa at temperatures of 800 to 1 400℃for 30 min.Vickers hardness of the sintered samples increased with increasing CBN content and the highest hardness of 32.7 GPa was achieved for the CBN-5 wt%Al specimens sintered at 1 400℃.The reactions between CBN and Al started to occur at about 900℃and the reaction products strongly depended on the Al content,sintering temperature and Co diffused from the substrates according to the x-ray diffraction(XRD) observations.The CBN composite sintered at 1 200℃from a CBN-15 wt%Al mixture showed the best cutting performance.

Ferroelectric behaviour of 30nm BaTiO3 ceramics prepared by high pressure assisted sintering

Dense nanocrystalline BaTiO3 ceramics with a homogeneous grain size of 30 nm was obtained by pressure assisted sintering. The ferroelectric behaviour of the ceramics was characterized by the dielectric peak at around 120 ℃, the P-E hysteresis loop and some ferroelectric domains. These experimental results indicate that the critical grain size for the disappearance of ferroelectricity in nanocrystalline BaTiO3 ceramics fabricated by pressure assisted sintering is below 30 nm. The ferroelectric property decreasing with decreasing grain size can be explained by the lowered tetragonality and the ＇dilution＇ effect of grain boundaries.

Effects of sintering pressure and temperature on microstructure and tribological characteristic of Cu-based aircraft brake material

A novel Cu-based P/M aircraft brake material was prepared and the effects of sintering pressure and temperature on microstructure and tribological characteristic were investigated. For the constant sintering temperature, when the sintering pressure increases from 0.5 MPa to 1.5 MPa, the porosity, wear loss and friction coefficient decrease remarkably. When the sintering pressure increases from 1.5 MPa to 2.5 MPa, the porosity further decreases but in a little degree and wear behaviors are improved slightly. However, once the sintering pressure is larger than 2.5 MPa, it has no obvious effect on microstructure and tribological characteristic. For the constant sintering pressure, when the sintering temperature increases from 900 ℃ to 930 ℃, the sintered density remarkably increases, and wear behaviors are obviously improved. For further increasing sintering temperature to 1 000 ℃, the density keeps on increasing, but wear behaviors change slightly.

High-pressure sintering and magnetic properties of Fe_(86)Zr_(11-x)Nb_xB_3(x=5.5, 6) amorphous alloys

The thermal stability of milling Fe86Zr11-xNbxB3（x=5.5, 6） melt-spun strip powders and the influence of high-pressure sintering conditions on phase component and grain size of bulk alloys were investigated by X-ray diffractometry（XRD）, differential scanning calorimetry（DSC） and scanning electron microscopy（SEM）. The results show that milling melt-spun powder remains in the amorphous state, and the crystallization temperature of which is 480530℃, the apparent activation energy Ep of crystallization process is 294.1219.5kJ/mol. The increasing Nb content can increase crystallization temperature and decrease Ep. Under the sintering conditions of 5.5GPa/3min, when Pw is 1150W, single phase α-Fe nanocrystalline （20.626.7nm） bulk alloy with relative density higher than 99.0% can be obtained. Under the sintering conditions of 5.5GPa/1150W/3min, the magnetic properties of these nanocrystalline bulk alloys are Fe86Zr5.5Nb5.5B3 alloy, Bs=1.15T, Hc=5.08kA·m-1; Fe86Zr5Nb6B3 alloy, Bs=1.26T, Hc=4.27kA·m-1.

Recent advances of high-pressure generation in a multianvil apparatus using sintered diamond anvils

The tried and tested multianvil apparatus has been widely used for high-pressure and hightemperature experimental studies in Earth science. As a result, many important results have been obtained for a better understanding of the components, structure and evolution of the Earth. Due to the strength limi- tation of materials, the attainable multianvil pressure is generally limited to about 30 GPa （corresponding to about 900 km of the depth in the Earth） when tungsten carbide cubes are adopted as second-stage anvils. Compared with tungsten carbide, the sintered diamond is a much harder material. The sintered diamond cubes were introduced as second-stage anvils in a 6--8 type multianvil apparatus in the 1980s, which largely enhanced the capacity of pressure generation in a large volume press. With the development of material synthesis and processing techniques, a large sintered diamond cube （14 ram） is now available. Recently, maximum attainable pressures reaching higher than 90 GPa （corresponding to about 2700 km of the depth in the Earth） have been generated at room temperature by adopting 14-mm sintered diamond anvils. Using this technique, a few researches have been carried out by the quenched method or combined with synchrotron radiation in situ observation. In this paper we review the properties of sintered diamond and the evolu- tion of pressure generation using sintered diamond anvils. As-yet unsolved problems and perspectives for uses in Earth Science are also discussed.

Computational Analysis of Selective Laser Sintering of Inconel 625

A two-dimensional multi-physics finite element model is developed to simulate the Selective Laser Sintering(SLS)process using Inconel 625 powders.The validity of the developed model is first assessed by comparing its results with experimental data.Various factors such as phase transition,recoil pressure,surface tension,and theMarangoni force are considered.The study’s findings underscore that the morphology and thermal-fluid dynamics of the molten pool in the SLS process are predominantly shaped by the influence of the Marangoni force and recoil pressure acting on its surface.The recoil pressure at the front of the laser spot rises exponentially with temperature,making the liquid metal move downward,and creating a depression at the pool’s head.It also causes particles to splash from the pool’s rear edge.The study explores the influence of the backward Marangoni force,where hightemperature liquid flows from the front to the rear of the molten pool,creating a vortex and moving the pool in the rear.Process parameters like laser intensity,scan speed,and spot size were analyzed.The findings indicate that higher laser power lower scanning speed and laser beam spot size lead to increased width and depth of the molten pool.

Fabrication and residual stresses of aluminum nitride ceramics sintered at high-pressure

High-density AlN ceramics were fabricated without sintering additives at high pressure(5.0 GPa) and temperature(1300～1800℃).The sintered bodies were characterized by XRD,SEM and micro-Raman spectroscopy(MRS).Controlling fracture mode was intragranular when the sintering temperature was as low as 1400℃under 5.0 GPa.The values of residual stresses due to the distortion of the AlN lattice were assessed using the Micro-Raman Spectroscopy(MRS).The residual compression stress of the AlN ceramics sintered at 5.0 GPaand 1700℃for 125 min is 2.0 GPa.The residual compression stress is increased according to the extension of the sintering time.

Application of pre-alloyed powders for diamond tools by ultrahigh pressure water atomization

Copper, iron and cobalt based pre-alloyed powders for diamond tools were prepared by ultrahigh pressure water atomization（UPWA） process. Pre-alloyed powders prepared by different processes including UPWA, conventional water atomization （CWA） and elemental metal mechanical mixing （EMMM） were sintered to segments and then compared in mechanical properties, holding force between matrix and diamond, fracture morphology of blank and sintering diamond section containing matrix. The results showed that the pre-alloyed powder prepared by UPWA exhibits the best mechanical properties including the relative density, the hardness and the bending strength of matrix sinteredsegment. Sintered segments fractography of UPWA pre-alloyed powder indicatesmechanical mosaic strength and chemical bonding force between the pre-alloyed powder and the diamond, leading to the great increase in the holding force between matrix and diamond. The mechanical performance andthe service life of diamond tools were greatly improved by UPWA pre-alloyed powders.

A Breakthrough in Pressure Generation by a Kawai-Type Multi-Anvil Apparatus with Tungsten Carbide Anvils

Expansion of the pressure range of Kawai-type multi-anvil presses (KMAPs) with tungsten carbide (WC) anvils is called for, especially in the field of Earth science. However, no significant progress in pressure generation has been made for 40 years. Our recent studies have expanded the pressure generation of a KMAP with WC anvils to 65 GPa, which is the world record for high-pressure generation in this device and is more than 2.5 times higher than conventional pressure generation. We have also successfully generated pressures of about 50 GPa at high temperatures. This work reviews our recently developed technology for high-pressure generation. High-pressure generation at room temperature and at high temperature was attained by integration of the following techniques:① a precisely aligned guideblock system,② a high degree of hardness of the second-stage anvils,③ tapering of the second-stage anvil faces,④ a high-pressure cell consisting of materials with a high bulk modulus, and ⑤ high thermal insulation of the furnace. Our high-pressure technology will facilitate investigation of the phase stability and physical properties of materials under the conditions of the upper part of the lower mantle, and will permit the synthesis and characterization of novel materials.

Polycrystalline cubic boron nitride prepared with cubic-hexagonal boron nitride under high pressure and high temperature

Polycrystalline cubic boron nitride(Pc BN)compacts,using the mixture of submicron cubic boron nitride(c BN)powder and hexagonal BN(h BN)powder as starting materials,were sintered at pressures of 6.5–10.0 GPa and temperature of1750℃without additives.In this paper,the sintering behavior and mechanical properties of samples were investigated.The XRD patterns of samples reveal that single cubic phase was observed when the sintering pressure exceeded 7.5 GPa and h BN contents ranged from 20 vol.%to 24 vol.%,which is ascribed to like-internal pressure generated at grain-to-grain contact under high pressure.Transmission electron microscopy(TEM)analysis shows that after high pressure and high temperature(HPHT)treatments,the submicron c BN grains abounded with high-density nanotwins and stacking faults,and this contributed to the outstanding mechanical properties of Pc BN.The pure bulk Pc BN that was obtained at 7.7 GPa/1750℃possessed the outstanding properties,including a high Vickers hardness(~61.5 GPa),thermal stability(~1290℃in air),and high density(~3.46 g/cm^(3)).

Characterization of diamond MWCNTs composite fiber synthesized under high pressure and high temperature

A regrown composite fiber was synthesized during the sintering of diamond under high pressure 5.8 GPa and high temperature 1500℃for 1 min,using 3wt%MWCNTs as additive.SEM observation of the fiber after alkali and acid treatment revealed that the outer layer of the fiber is composed of nano-polycrystalline diamond.EDS,XPS,XRD and Raman spectrum analysis further identified that the fiber is composed of MWCNTs in the inner part and nano-polycrystalline diamond in the out layer.It is proposed that the untransformed MWCNTs may act as a template for the regrown outer layer of nano diamond fiber under high pressure and high temperature.

Theoretical and experimental investigation on vertical tank technology for sinter waste heat recovery

In the present work, the gas flow pressure drop and gas–solid heat transfer characteristics in sinter bed layer of vertical tank were studied experimentally on the basis of the homemade experimental setup. The gas flow pressure drop through the sinter bed layer was measured with different gas velocity and particle diameters, as well as the sinter and air temperatures. The influences of gas superficial velocity and particle diameter on the gas flow pressure drop and gas solid heat transfer in sinter bed layer were analyzed in detail. The revised Ergun's correlation and gas solid heat transfer correlation were obtained according to the regression analysis of experimental data. It is found that, the pressure drop of unit bed layer height gradually increases as a quadratic relationship with increasing the gas superficial velocity, and decreases as an exponential relationship with the increase of sinter particle diameter. For a given sinter temperature, the heat transfer coefficient in sinter bed layer increases with increasing the gas superficial velocity, and increases with decreasing the sinter particle diameter. In addition, the heat transfer coefficient also gradually increases with increasing the sinter temperature at the same gas superficial velocity and sinter particle diameter. The mean deviations between the experimental data obtained from this work and the values calculated by the revised Ergun's correlation and the experimental heat transfer correlation are 7.22% and 4.22% respectively, showing good prediction.

Grain-refining fabrication of nanocrystalline(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)high-entropy ceramics by ultra-high pressure sintering

As an important A_(2)B_(2)O_(7)-type ceramic,(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)high-entropy pyrochlore pos-sesses promising properties such as high melting point,high chemical durability,and low thermal conductivity.However,the low sintering ability limits its application in thermal barrier coating and radioactive waste immobilization.It usually needs long-term high-temperature soaking to achieve full density,but with inevitable grain growth.In this work,dense and grain-refined nanocrystalline(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)ceramics were prepared with ultra-high pressure sintering(UHPS)method under 10 GPa at a low temperature of 800℃.The densification behavior,microstructure evo-lution,and properties of the UHPS-ed samples were then investigated.The grain size of as-prepared(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)ceramic was only 151 nm,which is 40%smaller than that of raw pow-der.In addition,it exhibited advantageous properties including both high hardness and aqueous durabil-ity.Plastic deformation under ultra-high pressure was believed as the dominant densification mechanism responsible for grain refinement and property improvement.

Investigation of the compressibility and sinterabilty of AZ91 powder production and particle production by gas atomisation method

This study intends to determine the pressability and sinterability of AZ91 powder production by gas atomisation method and that of the produced powder for partial production.Therefore,first,a gas atomisation unit has been designed and manufactured in the laboratories of the Karabiik University,Department of Manufacturing Engineering.Atomised powder production has been achieved at a temperature of 795℃,with nozzle diameters of 2 and 4 mm and four different gas pressures(5,15,25,35 bars).Argon gas has been used for atomisation and as a protective gas atmosphere.Scanning electron microscope(SEM)is used to determine the shape of the produced AZ91 powder,and a laser particle size analyzer is used to analyze the powder size.Additionally,a microhardness(HV0.025)measurement has been conducted to determine the hardness of the produced powders.To achieve a homogeneous distribution,the produced powders are mixed in a three-dimensional moving turbulator for 30 min.Mixed powders have been pressed at 300,400,500 and 600 MPa and have been sintered at 500℃,550℃and 600℃.Additionally,the density values have been determined before and after sintering of the materials.SEM images have been obtained from the fractured surfaces of the samples before and after sintering.XRD and EDX analyses have been performed to determine the chemical composition.Further,microhardness(HV0.5)is obtained from the pressure surfaces of the samples to determine the effects of the pressing pressure and the sintering temperature on the hardness.As a result of the experimental studies,it has been observed that the powder size decreases with the increase in gas pressure and that the powder shape generally changes from ligament and complex shape to droplet and spherical shape.From the XRD,XRF and EDX results,it has been determined that the structure comprises an a phase(Mg main matrix)and Mg17Al12 interphase,which isβphase,and very small amounts of MgO have been observed.The hardness of the produced powders increased based on the increase in gas pressure.The densities of the samples increased with both increasing pressing pressure and sintering temperature.It has been observed from the fractured surface SEM images that the number of pores formed in the samples decrease with an increase in the pressing pressure.It has been determined that the post-sintering structure exhibitsαtypical dendritic structure.In addition to theα-Mg matrix phase,β(Mg17Al12)intermetallic andα+βeutectic were formed in the structure.The microhardness values of the samples decreased depending on the sintering temperature;the highest hardness value was measured as 64,02 HV0.5 at a pressing pressure of 300 MPa and a sintering temperature of 500℃,whereas the lowest hardness value was measured as 54,86 HV0.5 at a pressing pressure of 600 MPa and a sintering temperature of 600℃.

Experimental study on convection heat transfer and air drag in sinter layer

Convection heat transfer coefficient and air pressure drop in sinter layer are important factors for the design of sinter cooling craft. Due to the lack of necessary data, the two parameters are studied by experimental method. The experimental results show that heat conduction of sinter impacts the measurement of convection heat transfer coefficient. Convection heat transfer increases with the increase of air volumetric flow rate. Sinter layer without small particles(sample I) gives higher convection heat transfer coefficient than that with small particles(sample II). Under the considered conditions, volumetric convection heat transfer coefficient is in the range of 400-1800 W/(m3·°C). Air pressure drop in sinter layer increases with the increase of normal superficial velocity, as well as with the rise of air temperature. Additionally, air pressure drop also depends on sinter particle size distribution. In considered experimental conditions, pressure drop in sinter sample II is 2-3 times that in sinter sample I, which resulted from 17% small scale particles in sinter sample II.

UPPER BOUND METHOD FOR SINTERED POWDER MATERIALS IN PLANE STRAIN

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Effect of current on the microstructure and performance of (Bi_2Te_3)_(0.2)(Sb_2Te_3)_(0.8) thermoelectric material via field activated and pressure assisted sintering

（Bi_2Te_3）_（0.2）（Sb_2Te_3）_（0.8） thermoelectric material was sintered via a field activated and pressure assisted sintering（FAPAS） process.By applying different current intensity（0,60,320 A/cm^2） in the sintering process,the effects of electric current on the microstructure and thermoelectric performance were investigated.This demonstrated that the application of electric current in the sintering process could significantly improve the uniformity and density of（Bi_2Te_3）_（0.2）（Sb_2Te_3）_（0.8） samples.When the current intensity was raised to 320 A/cm^2,the preferred orientation of grains was observed.Moreover,positive effects on the thermoelectric performance of applying electric current in the sintering process were also confirmed.An increase of 0.02 and 0.11 in the maximum figure of merit ZT value could be acquired by applying current of 60 and 320 A/cm^2,respectively.

Mo_(2)C-TiN_(0.3)复合材料的高温高压制备及性能

将Mo_(2)C和TiN_(0.3)粉体采用机械合金化和高温高压烧结相结合的方法进行分层烧结,并制备30%Mo_(2)C-70%TiN_(0.3)的烧结体复合材料,分析Mo_(2)C-TiN_(0.3)烧结体的物相组成、微观组织结构及力学性能。结果表明:Mo_(2)C和TiN_(0.3)间存在明显的相互扩散,且形成了2层不同的扩散层;随着烧结温度不断升高,Mo_(2)C-TiN_(0.3)烧结体的晶粒尺寸逐渐变大,会导致烧结体的机械性能变差;在烧结过程中有高硬高脆的MoC生成,能够维持Mo_(2)C-TiN_(0.3)烧结体的硬度在19.0~20.0 GPa,但会降低其断裂韧性。

热压制备SiC/Si_(3)N_(4)陶瓷复合材料的力学性能研究

通过热压烧结制备SiC/Si_(3)N_(4)陶瓷复合材料,研究温度和压力对复合材料的力学性能和微观结构的影响。结果表明:(1)原料质量配比Si_(3)N_(4)SiC CaF_(2)=641,在1400℃、25 MPa烧结压力下材料的抗弯强度达到最大值为66.7 MPa,体积密度为2.2 g/cm^(3),气孔率达到29.01%。随着温度的上升,材料的性能逐渐下降。在1400℃时主晶相仍为β-Si_(3)N_(4)且含有少量SiC。(2)相同的质量配比时,在1400℃烧结温度和45 MPa的烧结压力下制备的复合材料的力学性能为77.4 MPa,体积密度达到2.3 g/cm^(3),气孔率达到27.09%。从SEM图中可以观察到随着烧结压力的不断升高,材料的致密度和力学性能逐渐提高。