Analysis of spot defects on the surface of a cold-rolled Fe-36%Ni alloy strip

Many spot defects were found on the surface of a cold-rolled Fe-36%Ni alloy strip produced in a factory,which seriously affected the surface quality of the product.Through metallographic microscopy and scanning electron microscopy analyses,it was found that the spot defects were caused by the residual oxide layer on the surface of the cold-rolled Fe-36%Ni alloy strip after hydrogen annealing.By properly increasing the grinding amount of the blank before cold rolling to remove the oxide layer,the spot defects on the surface of the cold-rolled strip were effectively eliminated,and the surface quality of the product was ensured.

Recrystallization and texture evolution of cold-rolled FeCrAl thin-wall tube with large Laves phase during annealing:Effect of Nb content

The recrystallization and texture evolution of cold-rolled FeCrAl-0.65 Nb and FeCrAl-1.2 Nb alloys thin-wall tubes annealed at 600−900℃ for 1−600 min were investigated.The microstructures were characterized by electron back scattering diffraction,electron probe micro-analyzer and transmission electron microscopy.The Vickers hardness and room temperature tensile properties were tested.The results showed that the hardness of fully recrystallized FeCrAl-1.2 Nb alloy was higher and more likely to recrystallize than FeCrAl-0.65 Nb alloy.The weak texture strength of annealing sample was obtained and the proportion of<111>//ND texture increased.The fine Laves phase distributed uniformly in FeCrAl-0.65 Nb alloy had good pinning effect and inhibited recrystallization.Higher Nb content had little effects on tensile properties of thin-wall tube,and induced the formation of larger Laves phase.There was less fine Laves phase pinning in the large area adjacent to the blocky Laves phase,which resulted in easy recrystallization in FeCrAl-1.2 Nb alloy.

Effect of water quenching processing parameters on the mechanical properties of a cold-rolled C-Mn-containing steel sheet

Cold-rolled advanced high-strength steel sheets have become the material of choice for the automotive industry because of their unique attributes of high strength and balanced mechanical properties.High-hydrogen gas jet cooling and water quenching are the most commonly used ultrafast cooling technologies for producing martensite-containing high-strength steel sheets.The water quenching technology ensures the fastest industrial cooling rate of 1 000 K/s;therefore,it has the highest potential with respect to saving alloys.In this study,the water quenching of a C-Mn-containing steel sheet is simulated during continuous annealing to investigate the effect of water quenching and tempering parameters on its mechanical properties.The results reveal that at low quenching temperatures,the strength of the steel sheet decreases as the soaking temperature increases.However,at high quenching temperatures,a high soaking temperature corresponds to increased strength after quenching,regardless of whether the material was austenitized in the single austenite zone or the inter-critical zone.Therefore,a high quenching temperature always results in a high strength and a high yield ratio after quenching.Low-temperature overaging(tempering) considerably influences the yield strength and yield ratio,and the extent of this influence is correlated with the soaking temperature.

Gradient coil design with enhanced shielding constraint for a cryogen-free superconducting MRI system

The relatively fragile low-temperature stability of cryogen-free superconducting magnetic resonance imaging(MRI)magnets requires the careful management of exogenous heat sources.A strongly shielded gradient magnetic field is important for the optimal operation of cryogen-free MRI systems.In this study,we present an enhanced shielding method incorporating a regionalized stray field constraining strategy.By optimizing the constraint parameters,we could develop engineering-feasible gradient coil schemes without increasing system complexity but with the stray field intensity reduced by half.In real measurement in an integrated MRI system,the developed gradient assembly demonstrated good performance and supported to output images of excellent quality.Our findings suggested that the proposed method could potentially form a useful design paradigm for cryogen-free MRI magnets.

Fracture Behavior of TiNi Based Shape Memory Alloy Cold-rolled Tube

The microstructures and interracial characteristics of matrices at the inwalls and the out-walls of the cold-rolled tube with different amounts of deformation were investigated by the scanning electronic microscope （SEM）, the optical microscope （OM）, and the transmission electronic microscope （TEM） techniques. It was observed that as the amount of deformation increases, the flaws nucleate at the out-walls of the cold rolled tube, the stress-induced martensites change from （111 ） type Ⅰ twins to （011） type Ⅱ twins and then to （100） compound twins, nanocrystals and bulk amorphisation happen, the high density dislocation causes stress concentration at the out-walls of the Ti50Ni50 cold-rolled tube, and then precipitates its fracture, and the Ti2Ni particles strengthen the grain boundaries and curb the dislocation movements during plastic deformation. The inhomogeneity level of the grains in the Ti50Ni50 alloy plays an important role on the fracture of the Ti50Ni50 cold rolled tube.

Effect of annealing parameters on mechanical properties of cold-rolled martensitic steel sheets

Cold-rolled martensitic steel sheets produced on continuous annealing lines with water quenching facility,have advantages of high strength and low alloying element contents.These are in good accordance with the trend of light-weighting and fuel saving for automotive steel.In this article,a cold-rolled martensitic steel is studied to investigate the effect of annealing parameters on its mechanical properties.It is found that the quenching temperature and the slow cooling speed as well as the overageing temperature have significant influence on the strength of the experimental steel.The temperature zone at which the austenite decomposition is slow or has not started may be chosen as the quenching temperature to ensure the steel’s strength stability.The slow cooling speed also influences the steel’s strength greatly.A high cooling rate will lead to significantly higher strength.Tempering would decrease the steel’s tensile strength but would increase its yield strength.

Development and application of Baosteel's cold-rolled martensitic steel sheets

Cold-rolled martensitic steel sheets are becoming widely applied in the automotive industry because of their ultra-high strength,which may result in satisfactory weight reduction. The grades of martensitic steel sheets are classified based on their tensile strength,which ranges from 980 to 1 700 MPa. The main applications include a series of structural parts of uniform cross-section or simple shape,such as bumper beams,door beams and door sills,etc. The study and development of cold-rolled martensitic steel sheets date back to 2007 in Baosteel,and some grades became commercially available in 2009. By 2015,Baosteel had commercially supplied thousands of tons of these steel sheets with tensile strength up to 1 400 MPa. Currently,1 500 MPa martensitic steel sheet is commercially available and 1 700 MPa martensitic steel sheet has been successfully produced. The process technology and application guides of Basoteel ＇s cold-rolled martensitic steels are summarized and analyzed in order to assist ongoing research and ensure correct applications of these ultra-high strength steel sheets.

Fatigue Response of Cold-Rolled Type-304 Stainless Steel Foil

This study presents the fatigue response of 304 stainless steel foil, cold-rolled to a thickness of 3.2 μm with 87 percent cold work at orientations of 0, 45, and 90 degrees to the direction of rolling. Fatigue specimens were fabricated by laminating a supportive layer of 20-μm polyimide film to one side of the foil and patterning 242 crack initiation features by photolithographic process. Progression of fatigue damage was determined through electrical resistance measurement. The fatigue response was demonstrated to be largely affected by anisotropy existing between the rolling direction and the off-axis orientations. Fatigue cracks that traveled in a direction parallel to the elongated grains (cyclic loads applied at 90-degree orientation to foil rolling direction) had the most fatigue response (undesirable characteristic). The construction of the specimens with thin foil supported by a film backing contributed to high fatigue threshold.

Properties of ultra-low carbon,cold-rolled sheet steels containing titanium or boron for use in enameling

Ultra-low carbon（ULC）,cold-rolled sheet steels for porcelain enameling containing alloys of titanium and boron are studied. The microstructure,mechanical properties,inclusions,and precipitates of the sheet steels are analyzed. The hydrogen permeation time of the sheet steels as-annealed and after skin-passed or cold-rolled at different reductions are measured. It is show n that the sheet steels possess different features of enameling properties in hydrogen permeability,fishscale resistance,and pinhole resistance.

Analytical computation of magnetic field in coil-dominated superconducting quadrupole magnets based on racetrack coils

Currently,three types of superconducting quadrupole magnets are used in particle accelerators:cos 2θ,CCT,and serpentine.However,all three coil configurations have complex spatial geometries,which make magnet manufacturing and strain-sensitive superconductor applications difficult.Compared with the three existing quadrupole coils,the racetrack quadrupole coil has a simple shape and manufacturing process,but there have been few theoretical studies.In this paper,the two-dimensional and three-dimensional analytical expressions for the magnetic field in coil-dominated racetrack superconducting quadrupole magnets are presented.The analytical expressions of the field harmonics and gradient are fully resolved and depend only on the geometric parameters of the coil and current density.Then,a genetic algorithm is applied to obtain a solution for the coil geometry parameters with field harmonics on the order of 10^(-4).Finally,considering the practical engineering needs of the accelerator interaction region,electromagnetic design examples of racetrack quadrupole magnets with high gradients,large apertures,and small apertures are described,and the application prospects of racetrack quadrupole coils are analyzed.

Effect of coil and chamber structure on plasma radial uniformity in radio frequency inductively coupled plasma

Enhancing plasma uniformity can be achieved by modifying coil and chamber structures in radio frequency inductively coupled plasma(ICP)to meet the demand for large-area and uniformly distributed plasma in industrial manufacturing.This study utilized a two-dimensional self-consistent fluid model to investigate how different coil configurations and chamber aspect ratios affect the radial uniformity of plasma in radio frequency ICP.The findings indicate that optimizing the radial spacing of the coil enhances plasma uniformity but with a reduction in electron density.Furthermore,optimizing the coil within the ICP reactor,using the interior point method in the Interior Point Optimizer significantly enhances plasma uniformity,elevating it from 56%to 96%within the range of the model sizes.Additionally,when the chamber aspect ratio k changes from 2.8 to 4.7,the plasma distribution changes from a center-high to a saddleshaped distribution.Moreover,the plasma uniformity becomes worse.Finally,adjusting process parameters,such as increasing source power and gas pressure,can enhance plasma uniformity.These findings contribute to optimizing the etching process by improving plasma radial uniformity.

Fuzzy Proportional Integral Derivative control of a voice coil actuator system for adaptive deformable mirrors

Research on adaptive deformable mirror technology for voice coil actuators(VCAs)is an important trend in the development of large ground-based telescopes.A voice coil adaptive deformable mirror contains a large number of actuators,and there are problems with structural coupling and large temperature increases in their internal coils.Additionally,parameters of the traditional proportional integral derivative(PID)control cannot be adjusted in real-time to adapt to system changes.These problems can be addressed by introducing fuzzy control methods.A table lookup method is adopted to replace real-time calculations of the regular fuzzy controller during the control process,and a prototype platform has been established to verify the effectiveness and robustness of this process.Experimental tests compare the control performance of traditional and fuzzy proportional integral derivative(Fuzzy-PID)controllers,showing that,in system step response tests,the fuzzy control system reduces rise time by 20.25%,decreases overshoot by 78.24%,and shortens settling time by 67.59%.In disturbance rejection experiments,fuzzy control achieves a 46.09%reduction in the maximum deviation,indicating stronger robustness.The Fuzzy-PID controller,based on table lookup,outperforms the standard controller significantly,showing excellent potential for enhancing the dynamic performance and disturbance rejection capability of the voice coil motor actuator system.

Mathematical Modelling and Design of Helical Coil Heat Exchanger for Production of Hot Air for Fluidized Bed Dryer

In global industrialization, efforts have been made to increase the rate of heat transfer in heat exchanger, minimizing the size of heat exchanger to reduce cost as well as increasing the effectiveness. Helical coil heat exchanger (HCHE) has been proven to be effective in improving heat transfer due to its large surface area. In this study, HCHE was designed to provide hot air needed for fluidized bed drying processes. The HCHE design model was fabricated and evaluated to study the efficiency of the hot air output for a laboratory fluidized bed dryer. The mathematical model for estimation of the final (output) temperature of air, Taf, passing through the HCHE was developed and validated experimentally. The drying of bitter kola particulates was carried out with a drying temperature of 50C 3C and a bed height-to-bed diameter ratio (H/D) of 1.5. The time taken to dry bitter kola particulates to 0.4% moisture content was 1 hour 45 minutes. Hence, HCHE is recommended for use in the production of hot for laboratory-scale fluidized bed dryers.

Experimental and Numerical Investigation of the Performance of Turbulent Heat Transfer in Tubes with Different Cross-Sectioned Wire Coils

The thermal-hydraulic performance of plain tubes with and without wire coils in turbulent regimes is investigated experimentally and numerically.The effects of wire coil distribution(circular cross section)within the tube were explored experimentally,and water was employed as the working fluid.The numerical simulation was carried out using software programmer ANSYS Fluent 2019 R3 using the finite-volume approach.In the turbulent regime,six cross-sectionedwire coilswere analyzed,including:circular,rectangular,hexagonal,square,star shape,and triangle.The utilization of a tube with a wire coil has been shown to increase heat transfer rate and pump consumption.The results indicate a high level of concurrence,as the deviations are all below 8%.Compared with plain tube,the wire coils,according to the arrangement(TWD),gave the best PEC.The heat transfer enhancement ability of different cross sections follows the following order:StCS>RCS>HCS>SqCS>CCS>TCS.Also,the sequence of pump consumption for each cross section is as follows:RCS>StCS>SqCS>HCS>CCS>TCS.

Numerical Studies on Thermal and Hydrodynamic Characteristics of LNG in Helically Coiled Tube-in-Tube Heat Exchangers

As compact and efficient heat exchange equipment,helically coiled tube-in-tube heat exchangers(HCTT heat exchangers)are widely used in many industrial processes.However,the thermal-hydraulic research of liquefied natural gas(LNG)as the working fluid inHCTT heat exchangers is rarely reported.In this paper,the characteristics of HCTT heat exchangers,in which LNG flows in the inner tube and ethylene glycol-water solution flows in the outer tube,are studied by numerical simulations.The influences of heat transfer characteristics and pressure drops of the HCTT heat transfers are studied by changing the initial flow velocity,the helical middle diameter,and the helical pitch.The results indicate that different initial flow velocities in the inner tube and the outer tube of the HCTT heat exchanger have little influence on the secondary flow of the fluid in the helical tubes,and the overall flow characteristics tend to be stable.The smaller helical middle diameter of the HCTT heat exchanger leads to the shorter fluid flow length,the smaller resistance along the tubes and the increase of initial pressure under the condition of constant inlet velocity,which promotes the occurrence of secondary flow.The axial flow of fluid promotes the destruction of heat transfer boundary layer and gains strength of the turbulence and heat transfer efficiency.With the increase of the helical pitch of the HCTT heat exchanger,the turbulent intensity and the heat transfer efficiency are also increased.Moreover,the improvement of the flow state of the HCTT exchanger in a longer helical pitch also enhances the heat exchange efficiency.

Numerical Simulation of Liquified Natural Gas Boiling Heat Transfer Characteristics in Helically Coiled Tube-in-Tube Heat Exchangers

Helically coiled tube-in-tube(HCTT)heat exchangers are widely applied to the process technology because of their compactness and higher heat transfer efficiency.HCTT heat exchangers play an important role in liquified natural gas(LNG)use and cold energy recovery.The heat transfer characteristics,pressure distribution,and degree of vaporization of LNG in HCTT heat exchangers are numerically investigated.By comparing the simulation results of the computational model with existing experimental results,the effectiveness of the computational model is verified.The numerical simulation results show the vapor volume fraction of the HCTT heat exchanger is related to the inlet Reynolds number,inner tube diameters,and helix diameter.The vapor volume fraction increases rapidly from the fourth to the seventh equal division points of the helix tube length.On condition that the inlet Reynolds number is greater than 33500,the pressure drop rate gradually increases.When the magnitude of the vapor volume fraction is below 0.2,the heat transfer coefficient increase rate is greater than that when the vapor volume fraction is above 0.2.The heat exchange efficiency of HCTT heat exchangers increases with the decrease of the ratio of helix diameter to inner tube diameter.

p-τ值对COIL的影响的实验研究

实验研究了单重态氧发生器 ( SOG)的 p-τ值 ,即初始氯气分压与停留时间的乘积 ,对化学氧碘激光器 ( COIL)的影响 ,并分析了诸多实验因素对 SOG的 p-τ值的影响。对于提高

以氮气为载气的千瓦级COIL的初步实验研究

首次在氯气流量为 110 mmol/ s、采用方列管型射流式 O2 (1 Δ)发生器 (SPJSOG)以及列阵式超音速氧碘混合喷管的 COIL装置上 ,以氮气替代氦气作为载气进行出光实验研究。初步实验获得 1.8k W的激光输出功率以及

超音速连续波COIL的二维半数值模拟

给出了超音速连续波（ＣＷ）氧碘化学激光器（ＣＯＩＬ）的理论模型，利用此模型对典型实验装置进行了二维半几何近似下的初步数值模拟研究，对所得结果进行了讨论。

COIL运行参量对激光器性能的影响

基于物理近似模型和以Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程求解为中心的数值计算，研究了氧碘化学激光器（ＣＯＩＬ）激光性能随一些相关运行参量的变化规律，这些结果将对器件运行条件的选取和实验分析有一定的参考价值。