Advanced Materials Research Vols. 887-888

Abstract: Since the oil price has been significantly jumped for recent some years, the diesel engine of the merchant ship has been mainly used the heavy oil of low quality. Thus, it has been often exposed to severely corrosive environment more and more because temperature of the exhaust gas of a combustion chamber is getting higher and higher with increasing of using the heavy oil of low quality. As a result, wear and corrosion of the most parts surrounded with combustion chamber is more serious compared to the other parts of the engine. Therefore, an optimum repair welding for these parts is very important to prolong their lifetime in a economical point of view. In this study, 0.5Mo filler metal was welded with SMAW method in the forged steel which would be generally used with piston crown material. And the corrosion properties of weld metal zone, heat affected zone and base metal zone were investigated using electrochemical methods such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% H₂SO₄ solution. The heat affected and base metal zones exhibited the highest and lowest values of hardness respectively. And, the corrosion current density of the heat affected zone indicated the lowest value, having the highest value of hardness. It appeared that the corrosive products with red color was wholly covered on the surface of the base metal zone, while its products was not observed in the heat affected zone. The microstructure of the pearlite with black color was more or less observed in the base metal zone with patterns such as crystal and needle, in particular, the crystal pattern of ferrite microstructure with white color was considerably included in the base metal and heat affected zone, and the ferrite microstructure was significantly observed in the weld metal zone. In particular, the polarization characteristics such as impedance, polarization curve associated with corrosion resistance property were well in good agreement with each other. Keywords: Forged steel, Microstructure, 0.5Mo filler metal, SMAW, Weld metal zone, Electrochemical method, Corrosion current density, Hardness.

Abstract: In this work, the effect of isothermal heat treatments on microstructure evolution and mechanical properties after welding by induction of A37 pipeline steel have been studied by scanning electron microscopy, hardness measurements, and tensile tests. Microstructural evolution in welded joint was identified after isothermal annealing from 200 until 900 °C.

Abstract: In the process of deposition, the moving high energy heat source effect on the metal entity, and form the molten pool and the temperature field of directional conduction. Powder is accumulated in the substrate point by point, molten powder instantly solidify into a solid which is combined with substrate (or sediment) to reach metallurgical combination, from the perspective of the thermodynamic, the temperature field produced by coupling ring of heat source is regarded as a moving load to the base plate and the sedimentary section, and transient thermal stress field is generated, the load and boundary conditions (temperature field) of thermal stress field change over time, at the same time, the solution domain of thermal stress field change over time as a result. Therefore, through the life and death unit technology (ANSYS finite element analysis software of advanced analysis techniques) combined with the circulation order, the simulation of point to add deposition process is realized.

Abstract: The interface friction is used to evaluate the plastic flow behavior of workpiece material in different conditions such as temperature, pressure, strain rate and strain distribution. It is analyzed that deformation and material flow by the ring compression method during compression, which is contained with the theoretical calculation of different interface friction ring inside diameter and the height of the change. The progressive deformation incremental method is studied to the curve of the friction factor and ring size. It is given that the standard calibration curve of ring friction factor by 6:3:2 size ratio. According to the practical circle deformation ,it is given to the relative average stress, and then to calculate the average normal stress, according to the actual load stress ,it can be concluded that the actual flow stress of material. The change of ring height and diameter is measured by experiment. The results show that the friction factor is relatively stable, the maximum is 0.48, and then the minimum is 0.35.

Abstract: In order to solve the problem about the requirements of CNC equipments high speed measuring and simultaneous measurement of Multi-dimensional parameters accurately, this research describes the 6 D laser measurement system based on two-longitudinal modes thermal frequency stabilization laser. Because it launches two polarized light which is perpendicular to each other and the differences between the frequencies are big enough, it has high measurement speed (can be reach 1.3m/s) and can measure roll angle with high accuracy, which is the shortage of the existing 5D/6D multi-dimensional laser interferometer.

Abstract: Ni8W alloy ingots were prepared by SPS technic, followed by homogenizing, cold rolling and recrystallization annealing. The influence of ball milling on cold rolling and cube texture formation of Ni8W alloy substrates was investigated during the course of preparation. Finally, high quality cube-textured Ni8W alloy substrates were successfully obtained using this powder metallurgy process, and characterized by electron backscatter diffraction technic. It indicated that the cube texture fraction was as high as 90% (<10^o) when it annealed at 1350°C for 2 h.

Abstract: The article based on different frequency pulse equiponderance electromagnetic destressing comparison experiment, using vertical optical measurement to survey the changes of bearing ferrules size, study the difference between the effect of different frequency electromagnetic in removing residual stress, find the frequency of magnetic treatment pulse that help to maintain the stability of the thin-wall bearing collars' size, effectively improve the cycle of bearing ferrules process .

Abstract: Rolling schedule is an important parameter in high strength production of cold tandem rolling process, and the reasonable rolling schedule setting is important to cutting down energy consumption of unit, endurance of product stable and improving flatness as well as surface quality of sheet. Consequently, according to lots of theory research and spot experiment, taking relative balance of rolling force, flatness well of finished sheet and minimal rolling power as the control goal, the multi-object model for high strength sheet is built. Simultaneously, considering that PSO algorithm has shortcomings of initial randomness and premature convergence, the ACPSO algorithm is proposed which takes advantage of periodicity of the chaos motion and the inertial weight is adjust according to premature convergence extent of particle swarm and accommodate value of individual. It can improve convergence speed and accuracy. When the improved PSO algorithm is applied into rolling schedule model, it has good effect in spot experiment and productive practice.

Abstract: The plasma was used to assist hemp fiber degumming. After degumming, the relationship of the hemp fiber fineness and chemical composition was analyzed through the Grey Relation Analysis. The results indicates that pectin content is bigger than hemicellulose and lignin content on the influence of hemp fiber fineness, and the influence of cellulose content is small. This conclusion is consistent with the actual production and the experience of technical personnel.The pectin, hemicellulose, and lignin are therefore the main content to be removed in the plasma assisted degumming.