Effects of austempering temperature on microstructure and surface residual stress of carbidic austempered ductile iron(CADI) grinding balls

The effects of austempering temperature on microstructure and surface residual stress of carbidic austempered ductile iron （CADI） grinding balls were systematically investigated in this work. The microstructures were oberserved by optical metallography and analyized by X-ray diffraction. The surface residual stress measured by the cutting method is mainly composed of thermal stress and phase transformation stress.The thermal stress in grinding balls was determined by ANSYS simulation technique, and the surface phase transformation stress was obtained by subtracting the simulated surface thermal stress from the measured surface residual stress. Results show that all microstructures consist of ausferrite, white-bright zones （mixture of martensite and austenite）, nodular graphite, and carbides. The distribution of ausferrite shows uniform. With the increase of austempering temperature, the volume fraction and carbon content of austenite increase, whereas the amount of white-bright zone decreases. In addition, the surface residual stress increases with the increase of austempering temperature. Only the tension exists at the austempering temperature of 200 ℃, and the pressure exists at the austempering temperature of 220-260 °C. The thermal stress changes from the tension on the inside with the radius of 0-35 mm to the pressure on the outside with the radius of 35-62.5 mm, and the stress balance state presents at the radius of 35 mm. It is also found that the transformation stress is related to the content of carbon-rich austenite, and will reduce by 5.03 MPa accompanied with 1vol.% increase of the austenite.The thermal compressive stress and the transformation tensile stress on the surface both decrease with the increase of the austempering temperature.

Simulation on stress of large diameter CADI grinding ball based on ANSYS

The falling ball tests were carried out on theΦ125 mm diameter Carbidic Austempered Ductile Iron(CADI)grinding balls with Mn content of 2.0wt.%,2.3wt.%,2.6wt.%and 3.0wt.%,respectively,and the kind of grinding ball with the most serious spalling was selected for stress simulation.The stress distribution between four grinding balls in the elbow of the falling ball test device when they collided with each other was simulated based on ANSYS.Results of the falling ball tests show that the spalling and mass loss of a CADI grinding ball increases with the increase of Mn content,and the CADI grinding ball with 3.0wt.%Mn shows the most obvious spalling and mass loss.The simulation results of stress distribution of a CADI grinding ball show that the maximum impact stress does not appear in the center of the contact area,but in the annular area(inner diameter of^20 mm and outer diameter of^50 mm)in the section with a depth of 5-15 mm below the grinding ball surface.The actual spalling of the ball is consistent with the simulation results,and the oxide-based impurities in CADI grinding ball accelerate the spalling of the grinding ball in service.

A general strategy for MOFs coupled to optical fiber for highly sensitive humidity sensing

To achieve real-time and high-sensitive humidity sensing,a universal method was developed to allow arbitrary nanocrystals to be attached to the end of an optical fiber,further producing an effective interference spectrum.To validate this approach,four classical metal-organic framework(MOF) materials(ZIF-8,UiO-66,HKUST-1,MIL-101) are connected to the end of a single-mode optical fiber by this connection method to form humidity sensors.

Facile preparation of covalent organic frameworks@alginate composite beads for enhanced uranium(Ⅵ) adsorption

Covalent organic frameworks(COFs) have broad application prospects in adsorption and separation.Yet,as COFs are generally in powder form,their superior performance at the laboratory scale is difficult to transfer into pilot-or industrial-scale use.Thus,there is a strong and urgent need to structure COFs into monolithic materials.Herein,a facile strategy was developed to prepare COFs@alginate composite beads.Three composite beads comprising different COFs including TpPa-1(2,4,6-triformylphloroglucinol(Tp) and p-phenylenediamine(Pa-1)as monomers),TpDb(Tp and 2,5-diaminobenzonitrile(Db)as monomers) and TpTt(Tp and 1,3,5-triazine-2,4,6-triamine(Tt) as monomers) with controlled COF loading and product size have been facilely achieved via this strategy,validating the applicability of this method.Furthermore,the representative TpDb@alginate composite beads showed good adsorption performance of uranium(VI) in aqueous solution with high adsorption capacity(635 mg·g^(-1)),good interference immunity and recyclability.This work offers a practical approach for incorporation of COFs into polymer matrix,which can serve as potential adsorbents for radioactive wastewater treatment.

Synergistic effect of cubic C_(3)N_(4)/ZnO/C hybrid composite for selective detection of sulfur dioxide

With the development of industrial society,the emission of SO_(2) gas increases sharply.Because of the harm of SO_(2) to the environment and human health,it is crucial to detect and capture SO_(2),especially to develop gas sensing materials with good selectivity and durability to SO_(2).In this work,we prepared a C_(3)N_(4)/ZnO/C hybrid,MFM@IRMOF-3-T,for SO_(2) monitoring by annealing a composite of melamine-formaldehyde resin microsphere (MFM) and isoreticular metal-organic frameworks (IRMOF)-3.