Han Wu Liu

Microstructure Changes and Computer Simulation of K4169 Superalloy Using Chemical Grain Refinement Casting

As an important aeronautical assembly materials, such as aeronautical gas turbine and turbine plate et al, K4169 alloy has enough high ability of resistance to high temperature deformation and a long low-period fatigue life when working, and its grain structure should be equiaxed dendrite as fine as possible in casting. Chemical grain refinement method was used to refine K4169 alloy to satisfy the demands mentioned above. By using new intermetallic compound grain refiners, chemical grain refinement casting technology was carried out to refine K4169 superalloy. The results show that the grain morphology has been transformed from dendrite to granulation, the average principal axis length of the primary dendrites has been shorted and the segregation ratios of main alloy elements mitigate with the decrease of grain size in fine-grained castings, which indicates the remarkable effects of grain refinement. In addition, basing on the model of equiaxed dendrite growth solute diffusion, continuous nucleation model, dendrite tip growth kinetics model and cellular automata (CA) technique to coupled simulate the grain structure formation process of K4169 alloy in chemical grain refinement casting, which agreed very well with experiments results, this will do much contribution to the theoretic base for studying high temperature mechanics performance and performance of resistance to corrosion of K4169 superalloy.

Study on Magnetron Sputtering Process of Stainless Steel Particles Sputtering on Copper Substrate Based on LS-DYNA

The deformation process of stainless steel particle sputtering on copper substrate to make coat was simulated by ANSYS/LS-DYNA software in the paper. The results showed that: when the steel particles are sputtered on the copper substrate, the contacting place of copper substrate with stainless steel particle top generates maximum stress and strain firstly, and then stainless steel particle shrinks from the bottom to the center, while the top flattens to the both sides. Subsequently, the bottom of the particle gradually spreads along the substrate with the stress increasing gradually, while the strain distribution and top of the particles basically unchanged, then, the particle flattens and its stress gradually spreads to particle interior, at the same time, the bottom of particle gradually shrinks and its top gradually expands to the end. Through analyzing equivalent stress and strain distributions, the kinetic and internal energy distributions of sputtering particle unit and substrate unit contacting together, the variation rules of mechanics and energy parameters in the sputtering process are elaborated further. It laid an important theoretical basis about exploring the basic laws and mechanics parameters variation in magnetron sputtering coating process.

Temperature Distribution Analysis of TIG Welding Process of Thin-Walled Stainless Steel and Red Copper

The connecting pipe in solar hot water system is made by TIG welding of thin-walled stainless steel and copper. As the welding of stainless steel and copper belongs to dissimilar metal welding and their physical properties are very different, thus the welding of them is difficult and it is likely to cause a variety of defects in the welding process. In this paper, ANSYS software is used to simulate the welding process of stainless steel and copper, and the temperature distributions in the welding process are obtained. The results show that: as the heat transferring of copper is faster than stainless steel, the temperature field distribution of thin-walled stainless steel and copper tubes in the welding process is extremely uneven. As a result, the melting degrees on both sides in the welding seam are inconsistent, which may cause poor forming of weld seam. The results provide references and theoretical basis for the welding technology of dissimilar materials.

Computer Simulation of Filling Process and Temperature Distribution of Oil Pump Cover in Solidification Process

Oil pump cover, as a part of the oil pump, is generally formed by adopting aluminum die casting molding, and required for good internal and external quality. In order to improve the oil pump cover forming quality, the paper first simulates the thermal equilibrium of die-casting mold in the forming process by finite element analysis, and obtains the temperature curves when mold works for 10 consecutive cycles, and determines that the thermal equilibrium temperature of die-casting mold is 260 °C. And then, based on the simulation results of filling and solidification in the forming process by ProCAST software, the shrinkage and cavity appear in the larger wall thickness of the casting. Meanwhile, by simulating the die-casting processes of the oil pump at different pouring temperatures, there are the least of shrinkage and cavity when the pouring temperature setting 640 °C. The results show that: it can take some methods to achieve the progressive solidification, and can reduce or eliminate the possible shrinkage and cavity, such as shortening the distance between sprue, runner and inner runner and die casting to reduce the casting heat loss, or adding cooling system to accelerate the cooling rate in the larger wall thickness of the casting. This analysis provides theoretical basis for the actual casting production of oil pump covers.

Numerical Simulation of Semi-Solid Die Casting of ZA Alloy Automotive Bushing Based on AnyCasting

In order to reduce the wear of parts caused by long-term friction, and to reduce the frequency of parts replacement, ZA alloy with low hardness and good wear resistance is chosen to replace the traditional copper alloy as the material to manufacture automotive bushing, and the semi-solid die casting is used. On this basis, the software AnyCasting is used to simulate and analyze the filling and solidification process, the filling sequence, the variation of temperature field, and the part region where defects are prone to occur in the semi-solid process. The simulation results show that under the parameters set in the simulation process, when casting filling rate reached 90%, the metal started to solidify; since the gate place is easy for heat dissipation, when the temperature of the alloy liquid reached its liquidus temperature 595°C, the phenomenon of solid-liquid phase separation appeared at the gate; the defects such as gas trapping, residual stress and deformation would appear both in the place of first filling and the parting surface; when the preheat temperature of the mold was 150°C-200°C,the alloy liquid possesses liquidity. The simulation results offer certain theoretical instruction to optimize the semi-solid casting process of ZA Alloy automotive bushing manufacturing, as well as reducing or avoiding a variety of quality defects arose in the actual casting process.

Numerical Simulation of Preparation Process of Selective Absorbing Coating Based on Magnetron Sputtering Technology

According to a companys actual process of producing coatings, Finite Element Method is adopted to simulate and analyze the variation rules of various fields and mechanical parameters during the preparing process of solar spectrum selective absorbing coating for medium-high temperature application using magnetron sputtering. The results show that during the process of magnetron sputtering, magnetic fields uniformly distribute around the target and the sputtering etching area can be a wide range of 180°. In the spaces for magnetron sputtering, the magnetic flux is maximum at the contact between the and the core, and the magnetic flux density distributes uniformly between the magnetic steel and the target; the magnetic induction distribute uniformly within the120°direction of the target and forming two planar track typed etched channels; when the cylindrical target rotates at a proper speed, a large area of coating in uniform thickness can be deposited on the matrix. The results provide theoretical guidance for actual production of preparing medium-high temperature selective absorbing coating of uniform thickness and excellent quality.

Performance Forecast of Solar Spectrum Selective Absorbing Coating Based on RBF Neural Network

The paper researches on the coating performance prepared by sputtering stainless steel particles to Cu substrate, analyzes the effect of the six magnetron sputtering process parameters on absorption rate, such as Ar pressure, oxygen flow, sputtering vacuum degree, sputtering time, target voltage and target current with the artificial neural network technology, and forecasts the performance of the coating prepared by specific process parameters. The results show that during the process of magnetron sputtering when Ar pressure is within the range of 0.2 ~ 0.5 Pa, the oxygen flow is within the range of 0 ~ 20 sccm, and the target current is within the range of 380~ 430 A, the higher the sputtering vacuum degree and the target voltage, the superior the performance of the coating can be obtained. It is also found that the sputtering time has little effect on the coating performance, in the actual preparation process, on the condition that the performance can be guaranteed, the sputtering time should be as short as possible.

Residual Stress Analysis of TIG Welding Process of Thin-Walled Stainless Steel and Red Copper

The connecting pipe in solar hot water system is made by TIG welding of thin-walled stainless steel and copper. As the welding of stainless steel and copper belongs to dissimilar metal welding and their physical properties are very different, thus the welding process is difficult and it is likely to cause a variety of defects in the welding process. In this paper, ANSYS software is used to simulate the welding process of stainless steel and copper, and the residual stress distributions in the welding process are obtained. The results show that: at the end of the welding cooling, large residual stress (253MPa) is remained in the junction area of the starting and ending position of welding, which is close to the yield strength of material at the same temperature. Therefore, there will be greater deformation in the junction area and more cracks inside. Meanwhile, the stress distributions of stainless steel and copper tubes in the welding process are greatly different. Different volume changes emerge in two tubes, which are harmful to the welding seam and also leads to the unfitness of dimensional tolerance of welding parts, resulting in the scrapping of welding parts. The results provide references and theoretical basis for the welding technology of dissimilar materials.

Study on Thermal Stability and Salt Spray Resistance of SS-O Solar Spectrum Selective Absorbing Coating

The Cu-based SS-O solar spectrum flat-plate selective absorption coating system was prepared by the method of direct current reactive sputtering coating films, in which, two layers are SS-O absorbing layer and one is Si-O anti-reflection layer. The reflectance spectra of the absorption coating system was measured by UV3600 spectrophotometer, the reflectance and absorptance of the absorption layer and the anti-reflection layer were calculated, and certain experimental tests were conducted on the prepared absorption coating system in terms of the salt spray resistance performances, thermal stability and damp heat stability. The results show that the SS-O selective absorption coating which was prepared by magnetron sputtering technique possesses excellent processing property, corrosion resistance and thermal stability, whose absorption rate and the emission ratio have reached the level of the German blue tape series. It can meet the domestic demand for high-level flat-plate market.

Structure Analysis and Quality Prediction of DP Steel Engine Hood in the Process of Hot Stamping

Due to its good formability characteristics, such as high strength, high initial work hardening rate, as well as continuous yielding, thin-walled DP steel possesses great advantages of weight loss and security, and has been used to replace ordinary steel for automotive parts manufacturing by a lot of automotive industry. But along with the improvement of the performance of the strength, the high strength steels formability is worsened dramatically, and failure and fracture often occurs in its cold stamping process. So, hot stamping technology must be adopted to make the formability available. In the paper, it took the hot stamping process of DP steel engine hood for example and took DP800 as object of research. The forming limit, variation of major strain, minor strain and thickness, as well as the potential equality defects were analyzed by using eta/DYNAFORM software. The research results show that duplex steel plate can meet the performance requirements of car engine dumping plank forming, which offers theory basis for the production of similar parts.