Papers by Author: Jun Yang

Abstract: As the dynamic recrystallization (DRX) behavior of hot-deformed austenite is the basis of determining controlled rolling schedule for steel, in the present work, the dynamic recrystallization behavior of austenite of a 0.22%C-1.30%Mn-0.04%Nb micro-alloyed steel was investigated by means of high temperature compression tests on the Thermecmastor-Z simulator. By the analysis of true stress-strain curves at different deformation stages, the hot deformation equation of austenite was established for the steel. As a result, the energy to induce recrystallization of austenite for the steel is 419.1 kJmol^-1, as it was influenced by the drag effect of micro-alloyed element Nb in solid solution. The ratio (σ_c/σ_p) of critical stress σ_c (where DRX occurs) to peak stress σ_p is 0.93 while the ratio (ε_c/ε_p) of critical strain ε_c to peak stress ε_p is 0.52 for the steel. The austenite grain size of dynamic recrystallization of the micro-alloyed steel is refined by decreasing the deformation temperature and improving the stain rate.

Abstract: The relationship between the viscosity and the electrical conductivity of CaF₂-SiO₂- Al₂O₃-CaO-MgO slag system was deduced through theoretical calculation and experiment. The experiment was designed by quadratic orthogonal rotary regression method. The slag viscosity and conductivity were measured at 1600, and the constant (C) was calculated. The calculating model between each component mass fraction and constant C was performed, and the stability of calculating model was also verified by representative slag. The results showed that the calculating constant (C) of regression model is in good agreement with experimental values. Thus, the relationship between refining slag viscosity and conductivity using the formula at certain temperature is feasible.

Abstract: The separation of cobalt from zinc sulfate solutions by oxidation-precipitation process using peroxy-monosulfuric acid as oxidant has been presented according to the technological conditions of removal of cobalt from zinc electrolyte. After investigating the important parameters governing the separation of cobalt and their effect on the separation process, the optimal parameters of oxidation precipitation of cobalt were determined, the oxidation precipitation percent of cobalt was up to 90% under the conditions. The XRD analysis results of precipitates demonstrated that the precipitate was cobalt hydroxide oxide (CoOOH) in pure cobalt system while the precipitates were cobaltosic oxide (Co₃O₄) and basic zinc sulfate (ZnSO₄(OH)₆^.H₂O) in zinc-cobalt system.

Abstract: The hydrogen content was measured by HYDRIS hydrogen analyzer during ladle furnace (LF) refining process aiming to test the regular pattern of hydrogen variation in molten steel. The results showed that the hydrogen increased during temperature rising, Ca-treatment and soft blowing argon period, and the absolute increment were 0.64 ppm and 0.46 ppm respectively. The water in refining slag and submerged arc slag led to hydrogen increase during temperature rising period, and fast wire-feeding speed led to hydrogen increase during Ca-treatment and soft argon blowing period. In addition, during the desulfuration and alloying period, excessive large argon blowing caused the hydrogen content increasing by 0.22 ppm.

Abstract: The atomic oxidant was prepared under conditions of ultrasound and non-ultrasound. The influence of electrolysis time, electrolyte concentration, electrolysis voltage and additive concentration on concentration of oxidant were investigated. The results show that ultrasound could enhance the perpetrating rate. For ultrasonic cavitation and chemical effect, the concentration of oxidant significantly increased. Under the condition of electrolysis time 3 hours, voltage 6V, 35% sulfuric acid concentration and 0.5g/L additive, the ultrasonic frequency 40kHz and power 150W, the effect of oxidation could get the best result, and the oxidant concentration reached 0.9177mol/L.

Abstract: To overcome the disadvantage of MgO-CaO refractories, as the poor hydration resistance, MgO coating on the MgO-CaO clinker was fabricated by carbothermal reduction MgO with carbon as reduction agent and then the oxidation of Mg vapor. Effect of processing parameters (such as carbon source, reaction temperature and holding time) on the hydration resistance of MgO-CaO clinkers were investigated by hydration resistance test and SEM. The results indicated that the hydration resistance of treated MgO-CaO clinkers was improved when carbon black was used as reduction agent due to easy reaction with MgO than the graphite and coke. The high reaction temperature among 1450~1600°C and prolonged holding time within 4 h resulted in improvement of the hydration resistance of treated MgO-CaO clinker. Deposition mechanism of MgO coating on the MgO-CaO clinker was discussed.

Abstract: The atomic oxygen oxidant—Peroxy-monosulfuric acid was prepared by the method of electrolysis under the condition of with and without ultrasonic. The influence of electrolysis time, electrolyte concentration, electrolytic voltage and the additive concentration on the concentration of oxidant were investigated. The result indicated that with the usage of ultrasonic, combination the cavitation effect and the chemical effect enhanced the concentration of electrolysis oxidant; with the electrolytic time of 3 hours, the electrolytic tension of 6V, the sulfuric acid weight concentration of 35%, the additive concentration of 0.5g/L, the ultrasonic frequency of 40kHz and the power of 150W, the oxidant concentration could reach to 0.9177mol/L. This research is helpful for decreasing the production cost of atomic oxygen oxidant.

Abstract: Cu-coated Ti3SiC2 powder was fabricated by electroless copper plating method from CuSO4 using poisonless ascorbic acid (C6H6O4(OH)2) as reducing agent. Sensibilization and activation on Ti3SiC2 powder surface was performed by Sn-Ag catalyst system. Surfactants lauryl sodium sulfate (SDS) and Polysorbate 80 (Tween-80) were used as modifiers to control copper particle sizes and shapes. It is found that good pretreatment and activation can obtain fully-formed copper coating. The optimal copper deposition rate can reach to 2.053 g.dm-2.h-1 at 80°C . The best coating effect can be obtained in the samples modifying with 12g/L SDS+8ml/L Tween-80.

Abstract: The microstructural evolutions of 2205 duplex stainless steel welding joints were investigated in this paper. The specimens were solution treated at 1100°C and 1200°C for 1 h, water quenched and then isothermal aged for various durations at 850°C, followed by water cooling. The volume fraction of ferrite phase in HAZ, weld and base metal of the steel were measured by the ferrite scope detector. The changes of microstructure in sigma (σ) phase, ferrite and austenite phase were analyzed by optical microscope and energy dispersive spectrum. The results show that the volume fraction of ferrite phase increases and the ferrite grain becomes coarse when solution temperature enhances from 1100°C to 1200°C. During the aging, σ phase precipitates at γ/δ phase boundary and grows into the ferrite phase, and a eutectoid reaction of δ→σ+γ2 occurs. With extending of the aging time, the amount of ferrite phase decreases, σ phase increases and thin needle secondary austenite phase distributes across ferrite grains. In addition, high solution temperatures can delay the procedure of σ phase precipitation.

Abstract: HRB500 has been recognized an excellent material for structure. In this paper, Fire Dynamics Simulator (FDS) computer emulator method was adopted to analyze the bending performance and reinforcing ratio of HRB500 and conventional steel bar at the surface temperatures 600°C-900°C and center temperatures of 100°C-300°C underwent fire. The results showed that the HRB500 reinforced bar possessed superior seismic performance after the fire and this is helpful to the future application and design of steel for engineering.