The olivine-type LiFePO 4 powder was prepared by a chemical method using the synthesized FePO 4 1.78H 2 O, LiOH, citric acid and PEG as raw materials. The synthesized FePO 4 1.78H 2 O precursor powder was obtained by co-precipitation method. LiFePO 4 powder was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA)/differential scanning calorimetry (DSC). The results showed that the calcined LiFePO 4 was in a single phase when fabricated by using the synthesized FePO 4 1.78H 2 O powder at pH of 3.5 in argon atmosphere.
Comparing with conventional mechanical shot peening (SP) technique, water cavitation peening (WCP) experiments of Almen strips were carried out on a self-manufactured equipment. The results show that WCP demonstrates a wide range of standoff distance (SD) that from the nozzle to the surface of the object. By measuring the colour changes of the Fuji pressure sensing film, over 110 MPa impacting pressure was detected, which is resulted from the bubbles blasting on the sample surface when the SD is from 65 to 100 mm under 40 MPa of operating pressure. 600 MPa compressive residual stress achieved on the suface of the Almen strips after WCPed for 32 min. The depth of the zone affected by the compressive residual stress is about 100 µm. The highest residual stress appears in the top surface layer, while in case of SP it appears in the subsurface. Compared to SP, WCP is capable to get rather smoother surface and cause less deformation of the testing sheet, simultaneously.
The olivine-type LiFePO4 powder was prepared by a chemical method using the synthesized FePO4⋅2H2O, LiOH and glucose as raw materials. The synthesized FePO4⋅2H2O powder was obtained by co-precipitation method. FePO4⋅2H2O and LiFePO4 powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed the synthesized FePO4⋅2H2O powder at pH of 2.05 was in a single phase and nearly spherical in shape. Using the synthesized powders to prepared LiFePO4 at 600 °C in vacuum for 2 h was nearly spherical in shape and whose size was in the range of 0.1-0.5μm.
Hydraulic support is an important part of fully mechanized equipments. The constructional steels of hydraulic support with international advanced level mainly adopt the high-strength welding structural steel with its tensile strength of more than 700~1000MPa.This paper analyzes the chemical compositions features of S890 high-strength low alloy steel for 900MPa grade.The Influence of welding parameters,peak temperature and on the microstructures and mechanical properties of welding HAZ of S890 high-strength low alloy steel were investigated by thermo-simulated tests, The influence of welding heat input on the mechanical behaviors of the welded joint was also investigated. The results show that the microstructures of S890 steel change from tempered martensite to bainite and a little ferrite , pearlitic when welding heat input changes from low to high, and accompany the austenite grains coarsening ,so the impact toughness and hardness of welding HAZ at lower peak temperatures and shorter are higher than that at higher peak temperature and long . Welding HAZ produced by the second weld bead will overlap partially with the HAZ produced by the first weld bead. In this area, primitive microstructure tempers again or partial re-phase transformations and re-cools,but the area involved in the overlap is limited,so the influence on the properties of S890 steel is not obvious. In covered arc welding,the influence on the welded join strength of S890 steel is not distinct when heat input change in a certain scope, but the plasticity of the welded join falls off steeply as heat input increases. Keywords: S890 steel; high-strength low alloy steel; weld performance; hydraulic supports
The effects of HIP process on microstructure and mechanical properties of IN792 cast superalloy were studied. The results showed that HIP process produced more uniform and finer cubic γ′ than standard heat treatment. The difference of the mechanical properties should be caused by the microstructure changes. HIP process leads the homogeneous distribution of γ′ at dendritic arm and interdendritic area, and improved UTS and YS of tested alloy at 550°C. However, it played no role in increasing UTS and YS at room temperature and stress-rupture lives of 760°C/662MPa and decreased stress-rupture lives of 982°C/186MPa.
Abstract. S890 steel is a Mo-Mn alloy system bainitic structual steel which is developed in recent years and its strength is more than 900MPa,this steel is the material of hydraulic support possessing high-performance in coal mine.The continuous cooling curve of S890 steel was determined,microstructure and hardness of this steel in various cooling rate were analysised in the paper.Results have shown that:S890 steel has good quenching degree and quench-hardenability,and it can get steady microstructures which is mainly bainite over a broad range of cooling rate.
The cemented carbide YG30 and steel 1045 were welded with Co-Fe-C filling alloys with different carbon contents by the tungsten-inert-gas (TIG) arc welding. η phase formation at the welding joints was investigated through scanning electronic microscopy (SEM). The results show that the average composition of η phase is W-25, Fe-22, Co-19, C-24 (mass, %), which is a kind of carbide enriched by Fe, W，and Co. The amount of η phase formed near the interface of YG30 and weld bead is related to the C content in the filling alloy. Namely the amount of η phase decreases with the increasing of the C content in the filling metal. When the C content reaches to 0.8 wt%, no η phase forms. The reason of which is that the added C reduces and/or restrains the resolving of the WC that locates at the interface, so that inhibit the W and C to form η phase with Fe and Co. The existence of large-size η phase near the interface is mainly attributed to the aggregation of small size η phase with the unsolved WC due to the stir of liquid metal, and then growing up.
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